Electric Vehicles Vehicle Dynamics Vehicle Ergonomics Motors Alternating Current AC Charging Simulation Modelling Performance Computer Aided Design Hyper-Works Brushless Induction Motors AC Induction Motors Batteries Power Transmission Skewing Computer Aided Engineering Battery Management System Hybrid Vehicles Manufacturing DC Charging Magnet Design Computer Aided Manufacturing Characteristics Control Strategies Controller Efficiency Permanent Magnet Computerized Fluid Dynamics Solid Works Direct Current Technology State-of-art Prime Mover Vehicle Convertors Invertors EMI/EMC Induction Suspension Steering Ackermann Davis Mechanism Comparison Compression Tires Braking Hydraulics Master Cylinder Brake Booster High Pressure Lines Overview of Electrical Machines Construction Rotational Inertia Static Force Dynamic Force Newton's Law Wishbone Trailing Arm Ohms Law Resistance Current Voltage Mc-Pherson Anti Roll Dive Squat Electromotive Force Electron Kirchhoff’s Law Green Steering Wheel Steering Ratio Engine Management System Wireless Communication Unit Ergonomics All-Terrain Vehicle Autonomous Car Multi Body Dynamics Automotive Sketching Plastic Waste Management Motorcycle Repair Course Solar Power Plant Charging Station Car Repair and Maintenance Cyber Security Lab View industrial Application 3 D Printing Satellite Engineering Fire Safety Management Helicopter Management Wind Farm Engineering Drone Design Big Data Analytics Spacecraft Engineering Drone Programming Vehicle Crash Business Analytics Hydrogen Fuel Cell Technologies Web Security Airport Planning and Design Drone Taxi Ground Crew Management Drone/UAV Robotics Fundamentals Network Security Quadrotor Design Asteroid Mining Cloud Performance Tuning and Managing Sustainable Energy & Entrepreneurship Rocket Science UAV Designing & Development Security in Cloud Hyperloop Pod Autonomous Farming Railway Engineering Mars Rover Challenge Space Launch management Composite Material AI/ML ROBOCON Machine Learning Robofest Aeromodelling Design Autonomous Robotics Signal Processing Collapse Electric Vehicles Vehicle Dynamics Vehicle Ergonomics Motors Alternating Current AC Charging Simulation Modelling Performance Computer Aided Design Hyper-Works Brushless Induction Motors AC Induction Motors Batteries Power Transmission Skewing Computer Aided Engineering Battery Management System Hybrid Vehicles Manufacturing DC Charging Magnet Design Computer Aided Manufacturing Characteristics Control Strategies Controller Efficiency Permanent Magnet Computerized Fluid Dynamics Solid Works Direct Current Technology State-of-art Prime Mover Vehicle Convertors Invertors EMI/EMC Induction Suspension Steering Ackermann Davis Mechanism Comparison Compression Tires Braking Hydraulics Master Cylinder Brake Booster High Pressure Lines Overview of Electrical Machines Construction Rotational Inertia Static Force Dynamic Force Newton's Law Wishbone Trailing Arm Ohms Law Resistance Current Voltage Mc-Pherson Anti Roll Dive Squat Electromotive Force Electron Kirchhoff’s Law Green Steering Wheel Steering Ratio Engine Management System Wireless Communication Unit Ergonomics All-Terrain Vehicle Autonomous Car Multi Body Dynamics Automotive Sketching Plastic Waste Management Motorcycle Repair Course Solar Power Plant Charging Station Car Repair and Maintenance Cyber Security Lab View industrial Application 3 D Printing Satellite Engineering Fire Safety Management Helicopter Management Wind Farm Engineering Drone Design Big Data Analytics Spacecraft Engineering Drone Programming Vehicle Crash Business Analytics Hydrogen Fuel Cell Technologies Web Security Airport Planning and Design Drone Taxi Ground Crew Management Drone/UAV Robotics Fundamentals Network Security Quadrotor Design Asteroid Mining Cloud Performance Tuning and Managing Sustainable Energy & Entrepreneurship Rocket Science UAV Designing & Development Security in Cloud Hyperloop Pod Autonomous Farming Railway Engineering Mars Rover Challenge Space Launch management Composite Material AI/ML ROBOCON Machine Learning Robofest Aeromodelling Design Autonomous Robotics Signal Processing Collapse Electric Vehicles Vehicle Dynamics Vehicle Ergonomics Motors Alternating Current AC Charging Simulation Modelling Performance Computer Aided Design Hyper-Works Brushless Induction Motors AC Induction Motors Batteries Power Transmission Skewing Computer Aided Engineering Battery Management System Hybrid Vehicles Manufacturing DC Charging Magnet Design Computer Aided Manufacturing Characteristics Control Strategies Controller Efficiency Permanent Magnet Computerized Fluid Dynamics Solid Works Direct Current Technology State-of-art Prime Mover Vehicle Convertors Invertors EMI/EMC Induction Suspension Steering Ackermann Davis Mechanism Comparison Compression Tires Braking Hydraulics Master Cylinder Brake Booster High Pressure Lines Overview of Electrical Machines Construction Rotational Inertia Static Force Dynamic Force Newton's Law Wishbone Trailing Arm Ohms Law Resistance Current Voltage Mc-Pherson Anti Roll Dive Squat Electromotive Force Electron Kirchhoff’s Law Green Steering Wheel Steering Ratio Engine Management System Wireless Communication Unit Ergonomics All-Terrain Vehicle Autonomous Car Multi Body Dynamics Automotive Sketching Plastic Waste Management Motorcycle Repair Course Solar Power Plant Charging Station Car Repair and Maintenance Cyber Security Lab View industrial Application 3 D Printing Satellite Engineering Fire Safety Management Helicopter Management Wind Farm Engineering Drone Design Big Data Analytics Spacecraft Engineering Drone Programming Vehicle Crash Business Analytics Hydrogen Fuel Cell Technologies Web Security Airport Planning and Design Drone Taxi Ground Crew Management Drone/UAV Robotics Fundamentals Network Security Quadrotor Design Asteroid Mining Cloud Performance Tuning and Managing Sustainable Energy & Entrepreneurship Rocket Science UAV Designing & Development Security in Cloud Hyperloop Pod Autonomous Farming Railway Engineering Mars Rover Challenge Space Launch management Composite Material AI/ML ROBOCON Machine Learning Robofest Aeromodelling Design Autonomous Robotics Signal Processing Collapse Electric Vehicles Vehicle Dynamics Vehicle Ergonomics Motors Alternating Current AC Charging Simulation Modelling Performance Computer Aided Design Hyper-Works Brushless Induction Motors AC Induction Motors Batteries Power Transmission Skewing Computer Aided Engineering Battery Management System Hybrid Vehicles Manufacturing DC Charging Magnet Design Computer Aided Manufacturing Characteristics Control Strategies Controller Efficiency Permanent Magnet Computerized Fluid Dynamics Solid Works Direct Current Technology State-of-art Prime Mover Vehicle Convertors Invertors EMI/EMC Induction Suspension Steering Ackermann Davis Mechanism Comparison Compression Tires Braking Hydraulics Master Cylinder Brake Booster High Pressure Lines Overview of Electrical Machines Construction Rotational Inertia Static Force Dynamic Force Newton's Law Wishbone Trailing Arm Ohms Law Resistance Current Voltage Mc-Pherson Anti Roll Dive Squat Electromotive Force Electron Kirchhoff’s Law Green Steering Wheel Steering Ratio Engine Management System Wireless Communication Unit Ergonomics All-Terrain Vehicle Autonomous Car Multi Body Dynamics Automotive Sketching Plastic Waste Management Motorcycle Repair Course Solar Power Plant Charging Station Car Repair and Maintenance Cyber Security Lab View industrial Application 3 D Printing Satellite Engineering Fire Safety Management Helicopter Management Wind Farm Engineering Drone Design Big Data Analytics Spacecraft Engineering Drone Programming Vehicle Crash Business Analytics Hydrogen Fuel Cell Technologies Web Security Airport Planning and Design Drone Taxi Ground Crew Management Drone/UAV Robotics Fundamentals Network Security Quadrotor Design Asteroid Mining Cloud Performance Tuning and Managing Sustainable Energy & Entrepreneurship Rocket Science UAV Designing & Development Security in Cloud Hyperloop Pod Autonomous Farming Railway Engineering Mars Rover Challenge Space Launch management Composite Material AI/ML ROBOCON Machine Learning Robofest Aeromodelling Design Autonomous Robotics Signal Processing Collapse Electric Vehicles Vehicle Dynamics Vehicle Ergonomics Motors Alternating Current AC Charging Simulation Modelling Performance Computer Aided Design HyperWorks Brushless Induction Motors AC Induction Motors Batteries Power Transmission Skewing Computer Aided Engineering Battery Management System Hybrid Vehicles Manufacturing DC Charging Magnet Design Computer Aided Manufacturing Characteristics Control Strategies Controller Efficiency Permanent Magnet Computerized Fluid Dynamics Solid Works Direct Current Technology State-of-art Prime Mover Vehicle Convertors Invertors EMI/EMC Induction Suspension Steering Ackermann Davis Mechanism Comparison Compression Tires Braking Hydraulics Master Cylinder Brake Booster High Pressure Lines Overview of Electrical Machines Construction Rotational Inertia Static Force Dynamic Force Newton's Law Wishbone Trailing Arm Ohms Law Resistance Current Voltage Mc-Pherson Anti Roll Dive Squat Electromotive Force Electron Kirchhoff’s Law Green Steering Wheel Steering Ratio Engine Management System Wireless Communication Unit Ergonomics All-Terrain Vehicle Autonomous Car Multi Body Dynamics Automotive Sketching Plastic Waste Management Motorcycle Repair Course Solar Power Plant Charging Station Car Repair and Maintenance Cyber Security Lab View industrial Application 3 D Printing Satellite Engineering Fire Safety Management Helicopter Management Wind Farm Engineering Drone Design Big Data Analytics Spacecraft Engineering Drone Programming Vehicle Crash Business Analytics Hydrogen Fuel Cell Technologies Web Security Airport Planning and Design Drone Taxi Ground Crew Management Drone/UAV Robotics Fundamentals Network Security Quadrotor Design Asteroid Mining Cloud Performance Tuning and Managing Sustainable Energy & Entrepreneurship Rocket Science UAV Designing & Development Security in Cloud Hyperloop Pod Autonomous Farming Railway Engineering Mars Rover Challenge Space Launch management Composite Material AI/ML ROBOCON Machine Learning RobofestAeromodelling Design Autonomous Robotics Signal Processing Collapse Electric Vehicles Vehicle Dynamics Vehicle Ergonomics Motors Alternating Current AC Charging Simulation Modelling Performance Computer Aided Design Hyper-Works Brushless Induction Motors AC Induction Motors Batteries Power Transmission Skewing Computer Aided Engineering Battery Management System Hybrid Vehicles Manufacturing DC Charging Magnet Design Computer Aided Manufacturing Characteristics Control Strategies Controller Efficiency Permanent Magnet Computerized Fluid Dynamics Solid Works Direct Current Technology State-of-art Prime Mover Vehicle Convertors Invertors EMI/EMC Induction Suspension Steering Ackermann Davis Mechanism Comparison Compression Tires Braking Hydraulics Master Cylinder Brake Booster High Pressure Lines Overview of Electrical Machines Construction Rotational Inertia Static Force Dynamic Force Newton's Law Wishbone Trailing Arm Ohms Law Resistance Current Voltage Mc-Pherson Anti Roll Dive Squat Electromotive Force Electron Kirchhoff’s Law Green Steering Wheel Steering Ratio Engine Management System Wireless Communication Unit Ergonomics All-Terrain Vehicle Autonomous Car Multi Body Dynamics Automotive Sketching Plastic Waste Management Motorcycle Repair Course Solar Power Plant Charging Station Car Repair and Maintenance Cyber Security Lab View industrial Application 3 D Printing Satellite Engineering Fire Safety Management Helicopter Management Wind Farm Engineering Drone Design Big Data Analytics Spacecraft Engineering Drone Programming Vehicle Crash Business Analytics Hydrogen Fuel Cell Technologies Web Security Airport Planning and Design Drone Taxi Ground Crew Management Drone/UAV Robotics Fundamentals Network Security Quadrotor Design Asteroid Mining Cloud Performance Tuning and Managing Sustainable Energy & Entrepreneurship Rocket Science UAV Designing & Development Security in Cloud Hyperloop Pod Autonomous Farming Railway Engineering Mars Rover Challenge Space Launch management Composite Material AI/ML ROBOCON Machine Learning Robofest Aeromodelling Design Autonomous Robotics Signal Processing Collapse Electric Vehicles Vehicle Dynamics Vehicle Ergonomics Motors Alternating Current AC Charging Simulation Modelling Performance Computer Aided Design Hyper-Works Brushless Induction Motors AC Induction Motors Batteries Power Transmission Skewing Computer Aided Engineering Battery Management System Hybrid Vehicles Manufacturing DC Charging Magnet Design Computer Aided Manufacturing Characteristics Control Strategies Controller Efficiency Permanent Magnet Computerized Fluid Dynamics Solid Works Direct Current Technology State-of-art Prime Mover Vehicle Convertors Invertors EMI/EMC Induction
THE ELECTRIC VEHICLE GUIDE A Beginner’s Guide to EV Technology
An Electric Vehicle Manual
A DIYguru Presentation
The Electric Vehicle Guide Book A Guide to Electric-Vehicle Technology The guidebook documents the experience and knowledge gained from DIYguru’s consultants. Using IEEE, SAE, ARAI and ASME as the accountability tool, the resource has been designed to foster improvement in overall technical and nontechnical knowledge of electric vehicle. The guidebook will be continuously updated and expanded to encompass the new technology in this domain. It is our hope that by creating and sharing this resource, we can support others in their learning as we all strive to meet the profound challenge of becoming an environmentally sustainable society.
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This guide is published by DIYguru Education and Research Pvt. Ltd. Copyright 2019, DIYguru. All rights reserved. This document or any part thereof may not be reproduced for any reason whatsoever in any form or means whatsoever and howsoever without the prior written consent and approval of DIYguru Education and Research Pvt. Ltd. Whilst every effort has been made to ensure the accuracy of information contained in this publication, DIYguru, its employees or agents shall not be responsible for any mistake or inaccuracy that maybe contained herein and all such liability and responsibility are expressly disclaimed by these said parties.
Published by: DIYguru Press Delhi NCR, India +91-11-40365756 www.diyguru.org printed in India at New Delhi November 2019, Inaugural edition – 3000 Copies support@diyguru.org NOT FOR RESALE 2|Page
An Electric Vehicle Manual
A DIYguru Presentation
Project Team • • •
Aayush Chimurkar Anubhav Sen Nikhil Raj
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Foreword
Mr. Avinash Kumar Singh Director, DIYgur Education and Research Pvt. Ltd.
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A DIYguru Presentation
Preface
Mr. Nikhil Raj Program Manager
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Contents
PROJECT TEAM
3
FOREWORD
4
PREFACE
5
1.ELECTRIC AND HYBRID VEHICLE
11
INTRODUCTION A) ELECTRIC VEHICLE B) HYBRID ELECTRIC VEHICLE HISTORY ECONOMIC AND ENVIRONMENTAL IMPACT BASIC DESIGN A) CONFIGURATION OF ELECTRIC VEHICLE B) VARIOUS ARCHITECTURE OF HYBRID ELECTRIC VEHICLE OPERATING MODES A) ELECTRIC VEHICLE B) HYBRID ELECTRIC VEHICLE CONCEPT OF HYBRIDIZATION
11 11 12 12 13 13 13 14 14 14 15 16
2. PNEUMATIC HYBRID VEHICLE CONCEPT
16
3. FUEL CELLS
17
FUEL CELL TECHNOLOGIES A) HYDROGEN FUEL CELL B) PROTON EXCHANGE MEMBRANE C) DIRECT METHANOL FUEL CELL D) MOLTEN CARBONATE FUEL CELL
18 18 18 18 19
4. SHORT TERM STORAGE SYSTEMS
20
ULTRA FLYWHEEL SUPERCAPACITORS
20 20
5. MOTORS
22
BRUSHLESS DC MOTORS (BLDC) A) CONSTRUCTION
22 23
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B)
WORKING INDUCTION MOTORS A) CONSTRUCTION B) WORKING
24 25 25 27
6. BATTERIES AND BATTERY MANAGEMENT SYSTEM
28
BATTERIES LITHIUM-ION BATTERIES BATTERY MANUFACTURING BATTERY MANAGEMENT SYSTEM
28 29 29 33
7. MOTOR CONTROLLERS
34
FEATURES: CONTROL WIRING CAN BUS COMMUNICATIONS INVERTER/CONVERTER TANDEM UNITS TYPES
34 35 35 37 38
9. REGENERATIVE BRAKING
39
ENERGY RECOVERY SYSTEM TURBOCHARGER MOTOR GENERATING UNIT – KINETIC MOTOR GENERATING UNIT – HEAT ENERGY STORE (ES) CONTROL ELECTRONICS
39 40 41 42 43 43
10. VEHICLE DYNAMICS
43
COORDINATE SYSTEM EARTH FIXED COORDINATE SYSTEM VEHICLE FIXED COORDINATE SYSTEM TIRE AXIS SYSTEM LOADS STATIC LOADS ON LEVEL GROUND DYNAMIC AXLE LOADS LOAD TRANSFER LATERAL LOAD TRANSFER LONGITUDINAL LOAD TRANSFER DIAGONAL LOAD TRANSFER LUMPED MASS EXTERNAL FORCES ON VEHICLE DRAG FORCE
44 44 44 45 46 46 46 48 48 49 50 51 52 52
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SIDE FORCE LIFT FORCE POWER-LIMITED ACCELERATION ENGINES POWER TRAIN TYRE MECHANICS TERMINOLOGIES OF TIRE AXIS SYSTEM MECHANICS OF FORCE GENERATION SLIP ANGLE TRACTIVE PROPERTIES
53 53 54 54 55 58 58 60 61 62
11. AUTOMOTIVE CHASSIS
65
MATERIALS FRAME WHEELS FUEL TANK BODYWORK FRAMEWORK DESIGN FRAME RAILS DESIGN FEATURES TYPES OF FRAME HINGE POINTS VERTICAL LOADING HORIZONTAL LOADING
65 67 68 70 70 71 72 73 73 77 78 78
12.TRANSMISSION SYSTEM AND DRIVE TRAIN
79
TRANSMISSION IN ELECTRIC VEHICLES TRANSMISSION IN CONVENTIONAL VEHICLES A) MANUAL GEARBOX B) SEMI-AUTOMATIC GEARBOX C) AUTOMATIC GEARBOX PROPELLER SHAFT DIFFERENTIAL A) OPEN DIFFERENTIAL B) LIMITED SLIP DIFFERENTIAL C) TORSEN DIFFERENTIAL
79 80 81 81 82 83 84 85 85 86
13. BRAKING SYSTEM
87
BRAKE HYDRAULICS TYPES
87 88
14. SUSPENSION
90
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An Electric Vehicle Manual INDEPENDENT SUSPENSION A) MACPHERSON STRUT SUSPENSION B) DOUBLE WISHBONE SUSPENSION SEMI INDEPENDENT SUSPENSION TWIST BEAM DEPENDENT SUSPENSION DE-DIEO SUSPENSION SUSPENSION TECHNOLOGIES ACTIVE SUSPENSION SEMI ACTIVE SUSPENSION MAGNETORHEOLOGICAL DAMPER INBOARD SUSPENSION POINTS A) ANTI-DIVE B) ANTI-SQUAT C) ROLL CENTRE MIGRATION
A DIYguru Presentation 92 92 93 94 94 94 95 96 96 97 98 98 99 99 99
15. STEERING SYSTEM
101
STEERING SYSTEM TECHNOLOGIES A) HYDRAULIC POWER STEERING B) ELECTRONIC POWER STEERING C) REAR-WHEEL STEERING STEERING GEARBOX EXPLANATION
102 102 105 107 107 108
16. ERGONOMICS
109
COMMON RISKS AND WAYS TO MINIMIZE IT MUSCULOSKELETAL DISORDERS (MSD’S) FATIGUE VIBRATION SUN EXPOSURE
112 112 112 113 113
17. CASE STUDY : HOW TO DESIGN AN ELECTRIC BIKE
114
ELECTRIC BIKE POWER SOURCE CHARGING BATTERY SWAPPING COMPONENTS OF E - BIKE DESIGN OF E BIKE DESIGNING OF SHAFT SHAFT DESIGN DESIGN OF SPROCKET AND CHAIN FOR ELECTRIC BIKE
114 114 114 114 114 116 116 116 117
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BIBLIOGRAPHY
121
NOTES
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1.Electric and Hybrid Vehicle Introduction There are two basic types of EVs: a) Electric vehicles (EVs) b) Plug-in hybrid electric vehicles (PHEVs) All-electric vehicles (AEVs) run only on electricity. Most have all-electric ranges of 80 to 100 miles, while a few luxury models have ranges up to 250 miles. When the battery is depleted, it can take from 30 minutes (with fast charging) up to nearly a full day (with Level 1 charging) to recharge it, depending on the type of charger and battery. If this range is not sufficient, a plug-in electric vehicle (PHEV) may be a better choice. PHEVs run on electricity for shorter ranges (6 to 40 miles), then switch over to an internal combustion engine running on gasoline when the battery is depleted. The flexibility of PHEVs allows drivers to use electricity as often as possible while also being able to fuel up with gasoline if needed. Powering the vehicle with electricity from the grid reduces fuel costs, cuts petroleum consumption, and reduces tailpipe emissions compared with conventional vehicles. When driving distances are longer than the all-electric range, PHEVs act like hybrid electric vehicles, consuming less fuel and producing fewer emissions than similar conventional vehicles.
a) Electric Vehicle
All-electric vehicles (AEVs) run only on electricity. Most have all-electric ranges of 80 to 100 miles, while a few luxury models have ranges up to 250 miles. When the battery is depleted, it can take from 30 minutes (with fast charging) up to nearly a 11 | P a g e
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full day (with Level 1 charging) to recharge it, depending on the type of charger and battery.
b) Hybrid electric Vehicle
Hybrid electric vehicles are powered by an internal combustion engine and an electric motor, which uses energy stored in batteries. A hybrid electric vehicle cannot be plugged in to charge the battery. Instead, the battery is charged through regenerative braking and by the internal combustion engine. The extra power provided by the electric motor can potentially allow for a smaller engine. The battery can also power auxiliary loads like sound systems and headlights, and reduce engine idling when stopped. Together, these features result in better fuel economy without sacrificing performance. Modern HEVs make use of efficiency-improving technologies such as regenerative brakes which convert the vehicle's kinetic energy to electric energy, which is stored in a battery or supercapacitor. Some varieties of HEV use an internal combustion engine to turn an electrical generator, which either recharges the vehicle's batteries or directly powers its electric drive motors; this combination is known as a motor– generator.
History The invention of the first model electric vehicle is attributed to various people. In 1828, Ă nyos Jedlik invented an early type of electric motor, and created a small model car powered by his new motor. In 1834, Vermont blacksmith Thomas 12 | P a g e
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Davenport built a similar contraption which operated on a short, circular, electrified track. In 1834, Professor Sibrandus Stratingh of Groningen, the Netherlands and his assistant Christopher Becker created a small-scale electric car, powered by nonrechargeable primary cells. An electric vehicle held the vehicular land speed record until around 1900. The high cost, low top speed, and short range of battery electric vehicles, compared to later internal combustion engine vehicles, led to a worldwide decline in their use; although electric vehicles have continued to be used in the form of electric trains and other niche uses.
Economic and Environmental Impact Electric cars (EVs) (also known as battery electric cars) have several environmental benefits compared to conventional internal combustion engine cars. They have lower operating and maintenance costs, produce little or no local air pollution, reduce dependence on petroleum and also have the potential to reduce greenhouse gas emissions. Electric motors are significantly more efficient than internal combustion engines and thus, even accounting for distribution losses, less energy is required to operate an EV. Producing batteries for electric cars requires additional resources and energy, so they may have a larger environmental footprint when new. Reduced noise emissions resulting from substantial use of the electric motor at idling and low speeds, leading to roadway noise reduction, in comparison to conventional gasoline or diesel powered engine vehicles, resulting in beneficial noise health effects (although road noise from tires and wind, the loudest noises at highway speeds from the interior of most vehicles, are not affected by the hybrid design alone). Reduced noise may not be beneficial for all road users, as blind people or the visually impaired consider the noise of combustion engines a helpful aid while crossing streets and feel quiet hybrids could pose an unexpected hazard.
Basic Design a) Configuration of Electric Vehicle
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b) Various Architecture of Hybrid Electric Vehicle
Operating modes a) Electric Vehicle Motor and battery only
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b) Hybrid Electric Vehicle
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Concept of hybridization
2. Pneumatic Hybrid Vehicle Concept
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3. Fuel Cells
Hydrogen + Oxygen = Electricity + Water Vapor Cathode: O2 + 4H+ + 4e– → 2H2O Anode: 2H2 → 4H+ + 4e– Overall: 2H2 + O2 → 2H2O A fuel cell is a device that converts chemical potential energy (energy stored in molecular bonds) into electrical energy. A PEM (Proton Exchange Membrane) cell uses hydrogen gas (H2) and oxygen gas (O2) as fuel. The products of the reaction in the cell are water, electricity, and heat. This is a big improvement over internal combustion engines, coal burning power plants, and nuclear power plants, all of which produce harmful by-products. Since O2 is readily available in the atmosphere, we only need to supply the fuel cell with H2 which can come from an electrolysis process (see Alkaline electrolysis or PEM electrolysis).
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Fuel Cell Technologies a) Hydrogen Fuel cell
b) Proton exchange Membrane
c) Direct methanol Fuel cell
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d) Molten Carbonate Fuel Cell
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4. Short Term Storage Systems Ultra flywheel
Flywheel energy storage systems (FESS) use electric energy input which is stored in the form of kinetic energy. Kinetic energy can be described as “energy of motion,” in this case the motion of a spinning mass, called a rotor. The rotor spins in a nearly frictionless enclosure. When short-term backup power is required because utility power fluctuates or is lost, the inertia allows the rotor to continue spinning and the resulting kinetic energy is converted to electricity. Most modern high-speed flywheel energy storage systems consist of a massive rotating cylinder (a rim attached to a shaft) that is supported on a stator – the stationary part of an electric generator – by magnetically levitated bearings. To maintain efficiency, the flywheel system is operated in a vacuum to reduce drag. The flywheel is connected to a motor-generator that interacts with the utility grid through advanced power electronics.
Supercapacitors
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The supercapacitor, also known as ultracapacitor or double-layer capacitor, differs from a regular capacitor in that it has very high capacitance. There are two conducting metal plates with an insulating material called a dielectric in between them. A capacitor stores energy by means of a static charge as opposed to an electrochemical reaction. Applying a voltage differential on the positive and negative plates charges the capacitor. This is similar to the buildup of electrical charge when walking on a carpet. Touching an object releases the energy through the finger. Capacitors have many advantages over batteries: they weigh less, generally don't contain harmful chemicals or toxic metals, and they can be charged and discharged zillions of times without ever wearing out. Electrochemical capacitors (supercapacitors) consist of two electrodes separated by an ion-permeable membrane (separator), and an electrolyte ionically connecting both electrodes. When the electrodes are polarized by an applied voltage, ions in the electrolyte form electric double layers of opposite polarity to the electrode's polarity. For example, positively polarized electrodes will have a layer of negative ions at the electrode/electrolyte interface along with a charge-balancing layer of positive ions adsorbing onto the negative layer. The opposite is true for the negatively polarized electrode.
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5. Motors Brushless DC Motors (BLDC) A Brushless DC motor (also known as a BLDC motor) is an electronically commutated DC motor which does not have brushes. The controller provides pulses of current to the motor windings which control the speed and torque of the synchronous motor. These types of motors are highly efficient in producing a large amount of torque over a vast speed range. In brushless motors, permanent magnets rotate around a fixed armature and overcome the problem of connecting current to the armature. The BLDC motor is widely used in applications including appliances, automotive, aerospace, consumer, medical, automated industrial equipment and instrumentation. The BLDC motor is electrically commutated by power switches instead of brushes. Compared with a brushed DC motor or an induction motor, the BLDC motor has many advantages: a) b) c) d) e) f) g)
Higher efficiency and reliability Lower acoustic noise Smaller and lighter Greater dynamic response Better speed versus torque characteristics Higher speed range Longer life
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a) Construction Stator
The BLDC motor stator is made out of laminated steel stacked up to carry the windings. Windings in a stator can be arranged in two patterns; i.e. a star pattern (Y) or delta pattern (Δ). The major difference between the two patterns is that the Y pattern gives high torque at low RPM and the Δ pattern gives low torque at low RPM. This is because in the Δ configuration, half of the voltage is applied across the winding that is not driven, thus increasing losses and, in turn, efficiency and torque.
Steel laminations in the stator can be slotted or slot less as shown in Figure 2. A slot less core has lower inductance, thus it can run at very high speeds. Because of the absence of teeth in the lamination stack, requirements for the cogging torque also go down, thus making them an ideal fit for low speeds too (when permanent magnets on rotor and tooth on the stator align with each other then, because of the 23 | P a g e
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interaction between the two, an undesirable cogging torque develops and causes ripples in speed). The main disadvantage of a slot less core is higher cost because it requires more winding to compensate for the larger air gap. Rotor The rotor of a typical BLDC motor is made out of permanent magnets. Depending upon the application requirements, the number of poles in the rotor may vary. Increasing the number of poles does give better torque but at the cost of reducing the maximum possible speed.
Another rotor parameter that impacts the maximum torque is the material used for the construction of permanent magnet; the higher the flux density of the material, the higher the torque.
b) Working A machine that converts DC electrical power into mechanical power is known as a Direct Current motor. BLDC motor working is based on the principle that when a current carrying conductor is placed in magnetic field, the conductor experiences a mechanical force. The direction of this force is given by Fleming’s left-hand rule and magnitude is given by; F = BIL (Newtons) where, F= Force B= Magnetic Field I= Current L= Length of Conductor According to Fleming’s left-hand rule when an electric current pass through a coil in a magnetic field, the magnetic force produces a torque that turns the DC motor. The direction of this force is perpendicular to both the wire and the magnetic field. 24 | P a g e
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Induction Motors An Induction motor is a type of three phase induction motor which functions based on the principle of electromagnetism. It is called a ‘squirrel cage’ motor because the rotor inside of it known as a ‘squirrel cage rotor’ looks like a squirrel cage. One big advantage of a squirrel cage motor is how easily you can change its speedtorque characteristics. This can be done by simply adjusting the shape of the bars in the rotor. Squirrel cage induction motors are used a lot in industry as they are reliable, self-starting, and easy to adjust. A squirrel cage induction motor consists of the following parts: • Stator • Rotor • Fan • Bearings
a) Construction Stator It consists of a 3-phase winding with a core and metal housing. Windings are such placed that they are electrically and mechanically apart. The winding is mounted on the laminated iron core to provide low reluctance path for generated flux by AC currents.
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Rotor It is the part of the motor which will be in a rotation to give mechanical output for a given amount of electrical energy. The rated output of the motor is mentioned on the nameplate in horsepower. It consists of a shaft, short-circuited copper/aluminum bars, and a core.
Fan A fan is attached to the back side of the rotor to provide heat exchange, and hence it maintains the temperature of the motor under a limit. Bearings Bearings are provided as the base for rotor motion, and the bearings keep the smooth rotation of the motor.
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b) Working In an induction motor only the stator winding is fed with an AC supply. Alternating flux is produced around the stator winding due to AC supply. This alternating flux revolves with synchronous speed. The revolving flux is called as "Rotating Magnetic Field" (RMF). The relative speed between stator RMF and rotor conductors causes an induced emf in the rotor conductors, according to the Faraday's law of electromagnetic induction. The rotor conductors are short circuited, and hence rotor current is produced due to induced emf. That is why such motors are called as induction motors. (This action is same as that occurs in transformers; hence induction motors can be called as rotating transformers.) Now, induced current in rotor will also produce alternating flux around it. This rotor flux lags behind the stator flux. The direction of induced rotor current, according to Lenz's law, is such that it will tend to oppose the cause of its production. As the cause of production of rotor current is the relative velocity between rotating stator flux and the rotor, the rotor will try to catch up with the stator RMF. Thus, the rotor rotates in the same direction as that of stator flux to minimize the relative velocity. However, the rotor never succeeds in catching up the synchronous speed. This is the basic working principle of induction motor of either type, single phase of 3 phase. Synchronous Speed: The rotational speed of the rotating magnetic field is called as synchronous speed.
where, f = frequency of the supply P = number of poles
Slip: Rotor tries to catch up the synchronous speed of the stator field, and hence it rotates. But in practice, rotor never succeeds in catching up. If rotor catches up the stator speed, there won’t be any relative speed between the stator flux and the rotor, hence no induced rotor current and no torque production to maintain the rotation. However, this won't stop the motor, the rotor will slow down due to loss of torque, the torque will again be exerted due to relative speed. That is why the rotor rotates at speed which is always less the synchronous speed. The difference between the synchronous speed (Ns) and actual speed (N) of the rotor is called as slip.
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6. Batteries and Battery Management System Batteries Lithium-ion batteries comprise a family of battery chemistries that employ various combinations of anode and cathode materials. Each combination has distinct advantages and disadvantages in terms of safety, performance, cost, and other parameters. The most prominent technologies for automotive applications are lithium-nickel-cobalt-aluminum (NCA), lithium-nickel-manganese cobalt (NMC), lithium-manganese spinel (LMO), lithium titanite (LTO), and lithium-iron phosphate (LFP). The technology that is currently most prevalent in consumer applications is lithium-cobalt oxide (LCO), which is generally considered unsuitable for automotive applications because of its inherent safety risks. All automotive battery chemistries require elaborate monitoring, balancing, and cooling systems to control the chemical release of energy, prevent thermal runaway, and ensure a reasonably longlife span for the cells.
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Lithium-Ion Batteries Lithium-ion batteries are currently used in most portable consumer electronics such as cell phones and laptops because of their high energy per unit mass relative to other electrical energy storage systems. They also have a high power-to-weight ratio, high energy efficiency, good high-temperature performance, and low selfdischarge. Most components of lithium-ion batteries can be recycled, but the cost of material recovery remains a challenge for the industry. Most of today's plug-in hybrid electric vehicles and all-electric vehicles use lithium-ion batteries.
Battery Manufacturing Electrode Coating The anodes and cathodes in Lithium cells are of similar form and are made by similar processes on similar or identical equipment. The active electrode materials are coated on both sides of metallic foils which act as the current collectors conducting the current in and out of the cell. The anode material is a form of Carbon and the cathode is a Lithium metal oxide.
Cell Assembly
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In the best factories cell assembly is usually carried out on highly automated equipment, however there are still many smaller manufacturers who use manual assembly methods.
Prismatic Cells Prismatic cells are often used for high capacity battery applications to optimize the use of space. These designs use a stacked electrode structure in which the anode 30 | P a g e
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and cathode foils are cut into individual electrode plates which are stacked alternately and kept apart by the separator. The separator may be cut to the same size as the electrodes but more likely it is applied in a long strip wound in a zig zag fashion between alternate electrodes in the stack. Cylindrical Cells For cylindrical cells the anode and cathode foils are cut into two long strips which are wound on a cylindrical mandrel, together with the separator which keeps them apart, to form a jelly roll (Swiss roll in the UK). Cylindrical cells thus have only two electrode strips which simplifies the construction considerably. Formation Once the cell assembly is complete the cell must be put through at least one precisely controlled charge / discharge cycle to activate the working materials, transforming them into their usable form. Instead of the normal constant current constant voltage charging curve, the charging process begins with a low voltage which builds up gradually. This is called the Formation Process. For most Lithium chemistries this involves creating the SEI (solid electrolyte interface) on the anode. This is a passivating layer which is essential for moderating the charging process under normal use. C-rate (hours) Sometimes the battery specification may refer to the C-Rate or charge time (hours). The Nominal Capacity of the battery is given at this C Rate. The discharge current can then be worked out from the C Rate and the Nominal Capacity.
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Recycling Batteries Widespread battery recycling would keep hazardous materials from entering the waste stream, both at the end of a battery's useful life, as well as during its production. Work is now under way to develop battery-recycling processes that minimize the life-cycle impacts of using lithium-ion and other kinds of batteries in vehicles. But not all recycling processes are the same: a) Smelting Smelting processes recover basic elements or salts. These processes are operational now on a large scale and can accept multiple kinds of batteries, including lithium-ion and nickel-metal hydride batteries. Smelting takes place at high temperatures, and organic materials, including the electrolyte and carbon anodes, are burned as fuel or reductant. The valuable metals are recovered and sent to refining so that the product is suitable for any use. The other materials, including lithium, are contained in the slag, which is now used as an additive in concrete. b) Direct recovery At the other extreme, some recycling processes directly recover battery-grade materials. Components are separated by a variety of physical and chemical processes, and all active materials and metals can be recovered. Direct recovery is a low-temperature process with minimal energy requirements. c) Intermediate processes The third type of process is between the two extremes. Such processes may accept multiple kinds of batteries, unlike direct recovery, but recover materials further along the production chain than smelting does.
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Battery Management System
The BMS is the brains behind plug-in hybrid (PHEV) and electric vehicles (EV), managing battery and other vital vehicle functions, so certainly this debate is essential in determining the proper technology and placement thereof to ensure years of increased PHEV and EV production without rapidly aging the charging infrastructure. Battery management systems work in real time to control many functions including battery monitoring, maintenance, regeneration, battery optimizing, failure prediction and/or prevention, battery data collection/analysis and planning. BMSs are an integral component of PHEVs and EVs to ensure proper battery operation and to protect the highly expensive automotive component. Apart from the battery module, the key components in the BMS include the following: Battery Monitoring Unit (BMU): It uses a microprocessor-based unit to monitor the various parameters such as state of charge, cell balancing and cell temperature and compares them with the specifications and communicate to the BCU. It also communicates with other devices through the CAN bus. Battery Control Unit (BCU): It receives inputs from the BMU and incorporates any remedial measures needed to protect the battery or balance the cell or maintain the SOC. BCU is designed with power electronics components.
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7. Motor Controllers A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor. A motor controller might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults.
Features: a) Smooth, hybrid throttle algorithm for familiar driving feel. b) Durable weather-resistant extruded aluminum housing. c) Adjustable motor idling function for automatic gearboxes or maintaining auxiliaries. d) High pedal lockout (protects against non-zero throttle on startup). e) Independent hardware overcurrent protection system.
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Control Wiring Two aviation-style screw-lock plugs for all control/low power connections –one with 4 pins for the throttle and one with 5 pins for power input and CAN bus connections. The diagram below shows pin identifications as viewed on the controller case. Plug 1: Throttle a) 5V: Output power supply for throttle. Max 50mA output (internal selfresetting fuse). b) Gnd: Ground connection for throttle. c) Throttle A: First throttle input, usually the analog level, 0-5V input. d) Throttle B: Second throttle input, either enable switch or 2nd analog, 0-5V input. e) Plug 2: Power and CAN f) 12V In: Connect to a key-switched 12V supply so the controller comes on when the key is turned on. Often wired in parallel with your main contactor. Maximum voltage range 8-18V input, approx. 200mA draw. g) Gnd: Connect to ground / vehicle chassis. h) CAN L and CAN H: Two wires for CAN bus communications. i) Shield: Not required (usually for pass through of shielding on CAN-bus cables).
CAN Bus Communications The industry-standard CAN bus interface, allowing the user to monitor and/or log information in real-time from the controllers such as voltages, currents, throttle levels, controller temperature, and a variety of possible error conditions. It also supports throttle control over CAN bus, and the reprogramming of controller settings. The easy way to interface over CAN bus is to use our EVMS Monitor. The Monitor will automatically detect the motor controller on the bus and display operating information on its colour touchscreen. (An EVMS Core or Lite can share the same CAN bus and EVMS Monitor if present, but is not required.)
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The following settings are available: a) Minimum battery voltage: This setting can be useful to avoid overworking or over-discharging your battery, by setting it to whatever voltage represents a low state of charge (flat battery). Note that this cannot replace a proper battery management system for protecting your cells! b) Maximum motor voltage: If using a motor rated to a lower voltage than your battery pack, you can use this setting to ensure that the motor controller will not over speed the motor. c) Maximum motor current: In vehicles with smaller motors, you may wish to reduce the maximum motor current in order to avoid damaging your motor from overcurrent. Most larger Series DC motors will be fine with the maximum 600A setting. d) Maximum battery current: If using small or weak batteries, you can adjust this setting to avoid overworking your batteries. (This typically does not affect acceleration when setting off, but may reduce high speed performance.)
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8. Converter A converter is an electrical or electro-mechanical device for converting electrical energy. It may be converting AC to or from DC, or the voltage or frequency, or some combination of these. One way of classifying power conversion systems is according to whether the input and output are alternating current (AC) or direct current (DC): • • •
DC to AC DC to DC AC to DC
Function of a Converter More properly called a voltage converter, this electrical device actually changes the voltage (either AC or DC) of an electrical power source. There are two types of voltage converters: a) step up converters (which increases voltage) b) step down converters (which decreases voltage). The most common use of a converter is to take relatively low voltage source and step-it-up to high voltage for heavy-duty work in a high-power consumption load, but they can also be used in reverse to reduce voltage for a light load source.
Inverter/Converter Tandem Units An inverter/converter is, as the name implies, one single unit that houses both an inverter and a converter. These are the devices that are used by both EVs and hybrids to manage their electric drive systems. Along with a built-in charge controller, the 37 | P a g e
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inverter/converter supplies current to the battery pack for recharging during regenerative braking, and it also provides electricity to the motor/generator for vehicle propulsion. Both hybrids and EVs use relatively low-voltage DC batteries (about 210 volts) to keep the physical size down, but they also generally use highly efficient high voltage (about 650 volts) AC motor/generators.
Types DC-AC Converters The main source of electrical power is the battery which is a DC source. The DC output of the battery is bucked or boosted according to the requirement and then converted into AC using a DC-AC inverter. The function of an inverter is to change a dc input voltage to a symmetric ac output voltage of desired magnitude and frequency. The output voltage waveforms of ideal inverters should be sinusoidal. DC-DC Converters The DC/DC converter effectively replaces the alternator on an Internal Combustion Engine (ICE) car. Instead of taking energy from the rotation of the ICE motor to charge the 12V battery, it pulls power from the main High Voltage (HV) battery pack and converts it down to 12V. The 12V systems (headlights, stereo, seat heaters, etc.) use a lot of power and would quickly drain the on-board 12V battery if it were not charged while driving. Some DC/DC converters also have the ability to boost convert. In other words, it can work backwards to take power from the 12V battery and boost it up to about 300V to charge the HV pack.
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9. Regenerative Braking Energy Recovery System
The energy stored under braking is made available to the pilot, who can decide to reuse it in specific situations – straight stretches, while overtaking other cars or at strategic points of the track – providing a power boost during each lap through a pushbutton or throttle. The device is connected directly to the drive shaft through a motor-generator that, under braking, driven by the same shaft, converts kinetic energy into electrical energy, Through the control unit and through shielded wiring, this current recharge lithium ion batteries. Under acceleration, on the other hand, kinetic energy is taken from the batteries when the pilot operates the power boost and, again through the electronic control unit, it is sent to the motor-generator, which rotates in the opposite direction and applies an accelerating force on the drive shaft. The motorgenerator can reach up to 40,000 revolutions per minute.
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The Advanced Hybrid Electrical Systems ingeniously recycle energy produced by the brakes and exhaust gases. Optimizing power through these advanced efficiencies
Turbocharger
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The current internal combustion engines also use a turbocharger so that apart from the electrical power boosting the engine from the hybrid system, further power comes from the turbo, which works by taking the hot gases from the engine’s exhaust system and uses them to spin a compressor that increases the air and fuel mix going into the engine. Burning fuel needs oxygen - and burning fuel efficiently needs even more, especially when restricted to 110kg of fuel per race. Our turbocharger simply helps the engine ‘breathe’ faster - handy when it spins at roughly 100,000 times a minute.
Motor generating Unit – Kinetic
The MGU-K - Motor Generator Unit, Kinetic - is one of the most complex pieces of the F1 Power Unit, performing several roles. Formula 1 braking generates massive amounts of heat - so intense that brake pads glow red with all the energy they are forced to absorb. Operating at around 1000 degrees Fahrenheit, the MGU-K can take that energy and regenerate it into electricity that can be fed into the ES (Energy Store). The MGU-K is not just a generator, however - it also deploys energy from the ES to the drivetrain, giving the car up to 160bhp of additional power when required. This energy can also be deployed to the MGU-H to support the turbo.
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Motor generating Unit – Heat The MGU-H - Motor Generator Unit, Heat - uses heat from the car’s waste exhaust gases to drive a generator - the same way the MGU-K uses energy. This converted energy can be sent directly to the ES or the MGU-K. The MGU-H has the ability to work in both ways. It can suck energy out, or, put energy back in. Primarily it works to support the turbo, helping the compressor get back up to speed when you re-apply your foot to the accelerator – minimizing Turbo lag, and maximizing performance.
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Energy Store (ES) The Energy Store is a specialist battery specific to each Formula 1 Power Unit that stores electricity harvested from the MGU-K and MGU-H. Since electrical energy is generated both by the extreme forces developed from braking and the heat emitted from the exhausts, it is an essential power source. Storing the recovered energy within the car is a must so that it can be utilized when needed. Over a single lap the maximum amount of energy that can be deployed from the Energy Store to the rear wheels is 4MJ. That provides roughly an extra 30 seconds of power per lap. Without the Energy Store, we wouldn’t have the hybrid cars that we run today.
Control Electronics The Power Units Electronic Control Unit (ECU) checks and controls electrical elements of the PU, millions of times every second. It is crucial in ensuring that the driver has the right amount of power at the right time throughout a race. Controlling the Input, output and generation of energy, the ECU enables the whole Unit to create its power.
10. Vehicle Dynamics Vehicle dynamics in its broadest sense and composes all forms of convince like ships, air planes. The principal involved in the dynamics of any kind of vehicle are diverse and extensive. In as much as the performance of a vehicle-the motions accomplished in accelerating, braking, cornering and ride-is a response to forces imposed, much of the study of vehicle dynamics must involve the study of how and why the forces are produced. The dominant forces acting on a vehicle to control performance are developed by the tire against the road. Thus, it becomes necessary to develop an intimate understanding of the behavior of tires, characterized by the forces and moments generated over the broad range of conditions over which they operate. Studying tire performance without a thorough understanding of its significance to the vehicle is unsatisfying, as is the inverse. Handling is often used interchangeably with cornering, turning, or directional response, but there are nuances of difference between these terms. Cornering, turning, and directional response refer to objective properties of the vehicle when changing direction and sustaining lateral acceleration in the process. For example, cornering ability may be quantified by the level of lateral acceleration that can be sustained in a stable condition, or directional response may be quantified by the lime required for lateral acceleration to develop following a steering input. Handling, on the other hand, adds to this the vehicle qualities that feed back to the 43 | P a g e
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driver affecting the ease of the driving task or affecting the driver's ability to maintain control. Handling implies, then, not only the vehicle's explicit capabilities, but its contributions as well to the system performance of the driver/vehicle combination.
Coordinate System Earth fixed coordinate system Vehicle attitude and trajectory through the course of a maneuver are defined with respect to a right-hand orthogonal axis system fixed on the earth. It is normally selected to coincide with the vehicle fixed coordinate system at the point where the maneuver is started. The coordinates are: X -Forward travel Y -Travel to the right Z-Vertical travel (positive downward) ψ- Heading angle (angle between x and X in the ground plane) ѵ-Course angle (angle between the vehicle's velocity vector and X axis) β- Sideslip angle (angle between the x axis and the vehicle velocity vector)
Vehicle Fixed Coordinate System On-board, the vehicle motions are defined with reference to a right-hand orthogonal coordinate system (the vehicle fixed coordinate system) which originates at the CG and travels with the vehicle. By SAE convention the coordinates are: x -Forward and on the longitudinal plane of symmetry y -Lateral out the right side of the vehicle Z-Downward with respect to the vehicle p -Roll velocity about the x axis q -Pitch velocity about the y axis r -Yaw velocity about the z axis
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Tire Axis System To facilitate precise description of the operating conditions, forces, and moments experienced by a tire, the SAE has defined the axis system. The X-axis is the intersection of the wheel plane and the road plane with the positive direction forward. The Z-axis is perpendicular to the road plane with a positive direction downward. The Y-axis is in the road plane, its direction being chosen to make the axis system orthogonal and right-hand.
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Loads Static Loads on Level Ground
When the vehicle sits statically on level ground, the load equations simplify considerably. The sine is zero and the cosine is one, and the variables R hx, Rhz, ax and DA are zero, Thus:
��� = �
đ?’„ đ?‘ł
đ?‘žđ?’“đ?’” = đ?‘ž
đ?’ƒ đ?‘ł
Dynamic Axle Loads Determining the axle loadings on a vehicle under arbitrary conditions is a first simple application of Newton's Second Law. It is an important first step in analysis of acceleration and braking performance because the axle loads determine the tractive effort obtainable at each axle, affecting the acceleration, grade ability, maximum speed, and draw bar effort.
Forces: W=mg=weight at CG 46 | P a g e
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Wf = Weight at front wheel Wr = Weight at rear wheel Fxf = Traction force at front Fxr = Traction force at rear Rxf = Rolling resistance at front Rxr = Rolling resistance at rear DA = Aerodynamic load acting on the body at ha Rhz = Vertical load under towing condition Rhx = Longitudinal load under towing condition Load on the front axle is found by taking net moment about the point A under the rear tires. Under no acceleration in pitch and taking clockwise direction as positive: đ?‘Š đ?‘Šđ?‘“ đ??ż + đ??ˇđ??´ â„Žđ?‘Ž + đ?‘Žđ?‘Ľ â„Ž + đ?‘…â„Žđ?‘Ľ â„Žâ„Ž + đ?‘Šâ„Ž đ?‘ đ?‘–đ?‘›đ?œƒ + đ?‘… â„Žđ?‘§ đ?‘‘â„Ž − đ?‘Šđ?‘? đ?‘?đ?‘œđ?‘ đ?œƒ = 0 đ?‘” For uphill altitude: đ?œƒ = +đ?‘Łđ?‘’ For downhill altitude: đ?œƒ = −đ?‘Łđ?‘’ Wf can be obtained by solving the above equation. Similarly, W r can be obtained by taking the moment about B under the front wheel đ?‘Šđ?‘“ = (đ?‘Šđ?‘? đ?‘?đ?‘œđ?‘ đ?œƒ-đ?‘…â„Žđ?‘Ľ â„Žâ„Ž -đ?‘… đ?‘Šđ?‘&#x; = (đ?‘Šđ?‘? đ?‘?đ?‘œđ?‘ đ?œƒ+đ?‘…â„Žđ?‘Ľ â„Žâ„Ž +đ?‘…
đ?‘Š â„Žđ?‘§ đ?‘‘â„Ž - đ?‘” đ?‘Žđ?‘Ľ â„Ž-đ??ˇđ??´ â„Žđ?‘Ž -đ?‘Šâ„Ž â„Žđ?‘§ (đ?‘‘â„Ž
đ?‘ đ?‘–đ?‘›đ?œƒ)/đ??ż
đ?‘Š
+ đ??ż)+ đ?‘” đ?‘Žđ?‘Ľ â„Ž+đ??ˇđ??´ â„Žđ?‘Ž +đ?‘Šâ„Ž đ?‘ đ?‘–đ?‘›đ?œƒ)/đ??ż
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Load Transfer Two main types of load transfer exist; lateral load transfer and longitudinal load transfer. In this article we will cover the basic equations for both to provide an understanding of what each is and how it works dynamically.
Lateral Load Transfer
Lateral load transfer occurs during cornering and is the shift of mass across the wheels due to the centrifugal force and the lateral acceleration. The diagram below shows a typical cornering scenario. When a car is cornering it creates a force called centrifugal force. This force works against the lateral acceleration which is created by the grip from the tyres known as the tyre cornering forces. The diagram above shows a vehicle cornering around a right-hand turn. In the diagram the cornering forces created by the tyres are what result in the lateral acceleration (ay). The units for “ayâ€? are in m/sec² but for the purposes of the calculations and equation simplifications we need it to be in units of g. Therefore, the below equation can be used to convert this. Where “Ayâ€? is the lateral acceleration in g force.
đ??´đ?‘Ś(đ?‘”) =
đ?‘Žđ?‘Ś 9.81
Another benefit to having the acceleration in terms of g force is that it can be directly correlated with data logging from sessions out on track that record cornering forces. Therefore, if you have any previously logged data or a target g force to generate around a certain corner then that figure could be used directly. Due to the equation
đ?‘ = đ?’Žđ?’‚ Where: 48 | P a g e
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• F = Force • m = Mass • a = Acceleration We can relate our scenario to the force equation in terms of the centrifugal force when cornering which is equal to: đ?‘Şđ?’†đ?’?đ?’•đ?’“đ?’Šđ?’‡đ?’–đ?’ˆđ?’‚đ?’? đ?’‡đ?’?đ?’“đ?’„đ?’† = đ?‘žđ?‘¨đ?’š Where: • W = Total vehicle mass • Ay = Lateral acceleration in g As the centrifugal force is always acting in the opposite direction to the lateral acceleration, the equation for centrifugal force becomes: đ?‘Şđ?’†đ?’?đ?’•đ?’“đ?’Šđ?’‡đ?’–đ?’ˆđ?’‚đ?’? đ?’‡đ?’?đ?’“đ?’„đ?’† = −đ?‘žđ?‘¨đ?’š First of all, we must take moments about the inside tyre using the following moment equation: đ?‘Ą đ?‘Šđ??ż ∗ đ?‘Ą = (đ?‘Š ∗ ) + (đ?‘Š ∗ đ??´đ?‘Ś ∗ â„Ž) 2 Where: • WL = Static Mass on Left Wheel (kg) • t = Track Width (m) • W = Vehicle Total Mass (kg) • Ay = Lateral Acceleration in G • h = Height of center of gravity (m) We can simplify and compress this equation to produce: đ?›Ľđ?‘Š = đ?‘Šđ??ż −
đ?‘Š đ?‘Š ∗ đ??´đ?‘Ś ∗ â„Ž = 2 đ?‘Ą
his can be simplified once more to produce the lateral load transfer expressed as a fraction of the total weight of the vehicle:
đ??żđ??żđ?‘‡ =
đ??´đ?‘Ś ∗ â„Ž đ?‘Ą
Longitudinal Load Transfer When a car is accelerating or braking, a reaction force is generated similar to the centrifugal force generated when cornering. This reaction force is “WAx�. The longitudinal acceleration is in g force again similar to the lateral load transfer. The g force value is “Ax�. If you have acceleration in meters per second squared then the below equation can be used to convert it into units of g. 49 | P a g e
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đ??´đ?‘?đ?‘?đ?‘’đ?‘™đ?‘’đ?‘&#x;đ?‘Žđ?‘Ąđ?‘–đ?‘œđ?‘› đ?‘šđ?‘ −1 đ??´đ?‘?đ?‘?đ?‘’đ?‘™đ?‘’đ?‘&#x;đ?‘Žđ?‘Ąđ?‘–đ?‘œđ?‘› đ??´đ?‘Ľ(đ?‘”) = 9.81đ?‘šđ?‘ −1 If the longitudinal acceleration is due to acceleration, then it is a positive value. If it is caused by braking then the acceleration should be assigned a negative sign. The diagram below displays a car accelerating that will be referred to for the initial equation to calculate the load transfer front to rear. It assumes that the center of gravity position is on the center line of the track width.
Taking moments about the front wheel we can generate the following equation: đ?›Ľđ?‘Š ∗ đ??ż = â„Ž ∗ đ?‘Š ∗ đ??´đ?‘Ľ Where: ΔW x = The increase in the rear axle downward load and therefore the decrease in front axle load. Or if braking, it is the decrease in rear axle load and the increase in front axle load in Kg. L = The wheel base of the car in meters h = The height of the center of gravity from the ground in meters W = Total mass of the car in Kg Ax = Longitudinal acceleration in g force. This equation can be reorganized to produce just the load transfer: â„Ž đ?›Ľđ?‘Š = ∗ đ?‘Š ∗ đ??´đ?‘Ľ đ??ż
Diagonal Load Transfer When we combine turning, or lateral acceleration braking or linear deceleration, some of the load from the inside rear tire is shifted diagonally to the outside front tire. The rear cornering power is lost by transferring load to the front and we lost front cornering power by generating and understeer torque about the vehicles CG. Also, further front cornering power is lost by either overloading the outside front 50 | P a g e
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tire or we compress its spring to the point the we fall off the tires camber curve. Exiting the corner, this situation is reversed.
Lumped Mass A motor vehicle is made up of many components distributed within its exterior envelope. Yet, for many of the more elementary analyses applied to it, all components move together. For example, under braking, the entire vehicle slows down as a unit; thus, it can be represented as one lumped mass located at its center of gravity (CG) with appropriate mass and inertia properties. For acceleration, braking, and most turning analyses, one mass is sufficient. For ride analysis, it is often necessary to treat the wheels as separate lumped masses. In that case the lumped mass representing the body is the "sprung mass," and the wheels are denoted as "unsprung masses." For single mass representation, the vehicle is treated as a mass concentrated at its center of gravity (CG).
Quarter Car Model
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External Forces on Vehicle
Drag Force In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers (or surfaces) or a fluid and a solid surface. Unlike other resistive forces, such as dry friction, which are nearly independent of velocity, drag forces depend on velocity. Drag force is proportional to the velocity for a laminar flow and the squared velocity for a turbulent flow. Even though the ultimate cause of a drag is viscous friction, the turbulent drag is independent of viscosity. Drag forces always decrease fluid velocity relative to the solid object in the fluid's path.
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Side Force Cornering force or side force is the lateral (i.e., parallel to the road surface) force produced by a vehicle tire during cornering. Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at which cornering force builds up is described by relaxation length. Slip angle describes the deformation of the tire contact patch, and this deflection of the contact patch deforms the tire in a fashion akin to a spring. As with deformation of a spring, deformation of the tire contact patch generates a reaction force in the tire; the cornering force. Integrating the force generated by every tread element along the contact patch length gives the total cornering force. Although the term, "tread element" is used, the compliance in the tire that leads to this effect is actually a combination of sidewall deflection and deflection of the rubber within the contact patch. The exact ratio of sidewall compliance to tread compliance is a factor in tire construction and inflation pressure. Because the tire deformation tends to reach a maximum behind the center of the contact patch, by a distance known as pneumatic trail, it tends to generate a torque about a vertical axis known as self-aligning torque. The diagram is misleading because the reaction force would appear to be acting in the wrong direction. It is simply a matter of convention to quote positive cornering force as acting in the opposite direction to positive tire slip so that calculations are simplified, since a vehicle cornering under the influence of a cornering force to the left will generate a tire slip to the right. The same principles can be applied to a tire being deformed longitudinally, or in a combination of both longitudinal and lateral directions. The behavior of a tire under combined longitudinal and lateral deformation can be described by a traction circle.
Lift Force A fluid flowing past the surface of a body exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it can act in any direction at right angles to the flow. If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a hydrodynamic force. Dynamic lift is distinguished from other kinds of lift in fluids. Aerostatic lift or buoyancy, in which an internal fluid is lighter than the surrounding fluid, does not require movement and is used by balloons, blimps, dirigibles, boats, and submarines. Planning lift, in which only the lower portion of the body is immersed in a liquid flow, is used by motorboats, surfboards, and water-skis.
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Power-Limited Acceleration The analysis of power-limited acceleration involves examination of the engine characteristics and their interaction through the powertrain.
Engines The source of propulsive power is the engine. Engines may be characterized by their torque and power curves as a function of speed. Gasoline engines typically have a torque curve that peaks in the mid-range of operating speeds controlled by the induction system characteristics. In comparison, diesel engines may have a torque curve that is flatter or even rises with decreasing speed. This characteristic, controlled by the programming of the injection system, has led to the high- torquerise heavy-duty engines commonly used in commercial vehicles. (In some cases, the torque rise may be so great as to provide nearly constant power over much of the engine operating speed range.) The other major difference between the two types of engines is the specific fuel consumption that is obtained. At their most efficient, gasoline engines may achieve specific fuel consumption levels in the range near0.4 lb./hp-hr., whereas diesels may be near 0.2 or lower.
Gasoline
Diesel
The ratio of engine power to vehicle weight is the first-order determinant of acceleration performance. At low to moderate speeds an upper limit on acceleration can be obtained by neglecting all resistance forces acting on the vehicle. Then from Newton's Second Law: Max=Fx Where: M= Mass of the vehicle=W/g ax= Acceleration in the forward direction Fx= Tractive force at the drive wheel Since the drive power is the tractive force times the forward speed equation can be written as: 54 | P a g e
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ax= 1/M*Fx = 550{(g*HP)/(V*W)} (ft/sec2) Where: g= Gravitational constant V= Forward speed HP= Engine Horsepower W= Weight of the vehicle
Power Train Starting with the engine, it must be remembered that engine torque is measured at steady speed on a dynamometer, thus the actual torque delivered to the drivetrain is reduced by the amount required to accelerate the inertia of the rotating components (as well as accessory loads not considered here). The torque delivered through the clutch as input to the transmission can be determined by application of NSL as: Tc = Te -Ieđ?œśe Where: Tc = Torque at the clutch (input to the transmission) Te = Engine torque at a given speed Ie= Engine rotational inertia đ?›źe= Engine rotational acceleration The torque delivered at the output of the transmission is amplified by the gear ratio of the transmission but is decreased by inertial losses in the gears and shafts. If the transmission inertia is characterized by its value on the input side, the output torque can be approximated by the expression: Td=(Tc-Itđ?œśe)Nt Where: Td= torque output to the drive shaft Nt= Numerical ratio of the driveshaft It= Rotational inertia of the transmission (as seen from the front side) Similarly, the torque delivered to the axles to accelerate the rotating wheels and provide tractive force at the ground is amplified by the final drive ratio with some reduction from the inertia of the driveline components between the transmission and final drive. The expression for this is: Ta=Fxr+Iwđ?œśw=(Td-Idđ?œśd)Nf 55 | P a g e
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Where: Ta= Torque on the axles Fx= Tractive force at the ground r = radius of the wheel Iw = Rotational inertia of the wheel and axle shaft đ?›źw= Rotational acceleration of the wheel Id = Rotational inertia of the drive shaft đ?›źd= Rotational acceleration of driveshaft Nf= numerical ratio of the final drive Now the rotational accelerations of the engine, transmission, and driveline are related to that of the wheels by the gear ratios. đ?œśd=Nfđ?œśW
and
đ?œśe= Ntđ?œśd=NtNfđ?œśW
The above equations (2-5) to (2-8) can be combined to solve for the tractive force available at the ground. Recognizing that the vehicle acceleration, ax is the wheel rotational acceleration, Îąw times the tire radius, yields:
Fx=
đ?‘ť đ?’† đ?‘ľ đ?’•đ?’‡ đ?’“
− {(Ie+It)Ntf2+IdNf2+IW}
đ?’‚đ?’™ đ?’“đ?&#x;?
where: Ntf= Combined ratio of transmission and final drive Thus far the inefficiencies due to mechanical and viscous losses in the driveline components (transmission, driveshaft, differential and axles) have not been taken into account. These act to reduce the engine torque in proportion to the product of the efficiencies of the individual components [3]. The efficiencies vary widely with the torque level in the driveline because viscous losses occur even when the torque is zero. As a rule of thumb, efficiencies in the neighborhood of 80% to 90% are typically used to characterize the drive line [5]. The effect of mechanical losses can be approximated by adding an efficiency value to the first term on the right-hand side of the previous equation, giving:
Fx=
đ?‘ť đ?’† đ?‘ľ đ?’•đ?’‡ đ?œź đ?’•đ?’‡ đ?’“
− {(Ie+It)Ntf2+IdNf2+IW}
đ?’‚đ?’™ đ?’“đ?&#x;?
Where: đ?œ‚ đ?‘Ąđ?‘“ =Combined efficiency of transmission and final drive 56 | P a g e
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It has two components: The first term on the right-hand side is the engine torque multiplied by the overall gear ratio and the efficiency of the drive system, then divided by tire radius. This term represents the steady-state tractive force available at the ground to overcome the road load forces of aerodynamics and rolling resistance, to accelerate, or to climb a grade. The second term on the right-hand side represents the "loss" of tractive force due to the inertia of the engine and drivetrain components. The term in brackets indicates that the equivalent inertia of each component is "amplified" by the square of the numerical gear ratio between the component and the wheels. Knowing the tractive force, it is now possible to predict the acceleration performance of a vehicle. The expression for the acceleration must consider all the forces that were shown in Figure 1.6. The equation takes the form: đ?‘ž
Max= đ?’‚
đ?’™
đ?’ˆ
=đ?‘
đ?’™
−đ?‘š
��
−đ?‘Ť
�
−đ?‘š
��
− đ?‘ž đ?’”đ?’Šđ?’?đ?œ˝
Where: M = mass of the vehicle= W/g ax= Longitudinal acceleration Fx= Tractive force at the ground Rx = Rolling resistance force DA= Aerodynamic drag force Rhx= Towing force Fx includes the engine torque and rotational inertia terms. As a convenience, the rotational inertias from Eq. (2-9b) are often lumped in with the mass of the vehicle to obtain a simplified equation of the form: đ?‘ž+đ?‘žđ?’“
(M+Mr)ax=
đ?’ˆ
đ?’‚
đ?’™
=
đ?‘ť đ?’† đ?‘ľ đ?’•đ?’‡ đ?œź đ?’•đ?’‡ đ?’“
−đ?‘š
��
−đ?‘Ť
�
−đ?‘š
��
− đ?‘ž đ?’”đ?’Šđ?’?đ?œ˝
Where: Mr = Equivalent mass of the rotating components The combination of the two masses is an “effective mass� and the ratio of (M+Mr)/M is the “mass factor�. The mass factor will depend on the operating gear, with typical values as below:
A representative number is often taken as:
Mass Factor= 1+ 0.04+ 0.0025 Ntf2 57 | P a g e
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Tyre Mechanics Terminologies of Tire Axis System
• • • • •
•
•
•
•
Wheel Plane central plane of the tire normal to the axis of rotation. Wheel Center-intersection of the spin axis and the wheel plane. Center of Tire Contact-intersection of the wheel plane and projection of the spin axis onto the road plane. Loaded Radius-distance from center of tire contact to the wheel center in the wheel plane. Longitudinal Force (Fx) component of the force acting on the tire by the road in the plane of the road and parallel to the intersection of the wheel plane with the road plane. The force component in the direction of wheel travel (sine component of the lateral force plus cosine component of the longitudinal force) is called tractive force. Lateral Force (Fy) component of the force acting on the tire by the road in the plane of the road and normal to the intersection of the wheel plane with the road plane. Normal Force (Fz) component of the force acting on the tire by the road which is normal to the plane of the road. The normal force is negative in magnitude. The term vertical load is defined as the negative of the normal force, and is thus positive in magnitude. Overturning Moment (Mx) moment acting on the tire by the road in the plane of the road and parallel to the intersection of the wheel plane with the road plane. Rolling Resistance Moment (My) -moment acting on the tire by the road in the plane of the road and normal to the intersection of the wheel plane with the road plane. 58 | P a g e
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Aligning Moment (Mz)- moment acting on the tire by the road which is normal to the plane of the road. Slip Angle (α)-angle between the direction of wheel heading and the direction of travel. Positive slip angle corresponds to a tire moving to the right as it advances in the forward direction. Camber Angle (ϒ) angle between the wheel plane and the vertical. Positive camber corresponds to the top of the tire leans outward from the vehicle.
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Mechanics of Force Generation The forces on a tire are not applied at a point, but are the resultant from normal and shear stresses distributed in the contact patch. The pressure distribution under a tire is not uniform but will vary in the X and Y directions. When rolling, it is generally not symmetrical about the Y-axis but tends to be higher in the forward region of the contact patch.
Because of the tire's viscos-elasticity, deformation in the leading portion of the contact patch causes the vertical pressure to be shifted forward. The centroid of the vertical force does not pass through the spin axis and therefore generates rolling resistance. With a tire rolling on a road, both tractive and lateral forces are developed by a shear mechanism. Each element of the tire tread passing through the tire contact patch exerts a shear stress which, if integrated over the contact area, is equal to the tractive and/or lateral forces developed by the tire. There are two primary mechanisms responsible for the friction coupling between the tire and the road. Surface adhesion arises from the intermolecular bonds between the rubber and the aggregate in the road surface. The adhesion component is the larger of the two mechanisms on dry roads, but is reduced substantially when the road surface is contaminated with water; hence, the loss of friction on wet roads. The hysteresis mechanism represents energy loss in the rubber as it deforms when sliding over the aggregate in the road. Hysteresis friction is not so affected by water on the road surface, thus better wet traction is achieved with tires that have highhysteresis rubber in the tread. Both adhesion and hysteresis friction depend on some small amount of slip occurring at the tire- road interface.
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Slip Angle In vehicle dynamics, slip angle of sideslip angle is the angle between the direction in which a wheel is pointing and the direction in which it is actually traveling (i.e., the angle between the forward velocity vector vx and the vector sum of wheel forward velocity vx and lateral velocity vy, as defined in the image to the right). This slip angle results in a force, the cornering force, which is in the plane of the contact patch and perpendicular to the intersection of the contact patch and the midplane of the wheel. This cornering force increases approximately linearly for the first few degrees of slip angle, and then increases non-linearly to a maximum before beginning to decrease.
Causes A non-zero slip angle arises because of deformation in the tire carcass and tread. As the tire rotates, the friction between the contact patch and the road results in individual tread 'elements' (finite sections of tread) remaining stationary with respect to the road. If a side-slip velocity u is introduced, the contact patch will be deformed. When a tread element enters the contact patch, the friction between the road and the tire causes the tread element to remain stationary, yet the tire continues to move laterally. Thus, the tread element will be ‘deflected’ sideways. While it is equally valid to frame this as the tire/wheel being deflected away from the stationary tread element, convention is for the coordinate system to be fixed around the wheel mid-plane. While the tread element moves through the contact patch it is deflected further from the wheel mid-plane. This deflection gives rise to the slip angle, and the cornering force. The rate at which the cornering force builds up is described by the relaxation length.
Effects The ratios between the slip angles of the front and rear axles (a function of the slip angles of the front and rear tires respectively) will determine the vehicle's behavior 61 | P a g e
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in a given turn. If the ratio of front to rear slip angles is greater than 1:1, the vehicle will tend to understeer, while a ratio of less than 1:1 will produce oversteer. Actual instantaneous slip angles depend on many factors, including the condition of the road surface, but a vehicle's suspension can be designed to promote specific dynamic characteristics. A principal means of adjusting developed slip angles is to alter the relative roll couple (the rate at which weight transfers from the inside to the outside wheel in a turn) front to rear by varying the relative amount of front and rear lateral load transfer. This can be achieved by modifying the height of the roll centers, or by adjusting roll stiffness, either through suspension changes or the addition of an anti-roll bar. Because of asymmetries in the side-slip along the length of the contact patch, the resultant force of this side-slip occurs away from the geometric center of the contact patch, a distance described as the pneumatic trail, and so creates a torque on the tire, the so-called self-aligning torque.
Tractive Properties Under acceleration and braking, additional slip is observed as a result of the deformation of the rubber elements in the tire tread as they deflect to develop and sustain the friction force.
Braking deformation in the contact patch Slip On a dry road, when the slip approaches approximately 15-20 percent, the friction force will reach a maximum (typically in the range of70 to 90 percent of the load) as the majority of tread elements are worked most effectively without significant slip. Beyond this point friction force begins to drop off as the slip region in the rear 62 | P a g e
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of the contact patch extends further forward. The force continues to diminish as the tire goes to lockup (I 00% slip).
Brake forces v/s slip Vertical Load Increasing vertical load is known categorically to reduce friction coefficients under both wet and dry conditions. That is, as load increases, the peak and slide friction forces do not increase proportionately. Typically, in the vicinity of a tire's rated load, both coefficients will decrease on the order of 0.01 for a 10% increase in load.
Typical variation of friction coefficient with the tyre load
Inflation Pressure On dry roads, peak and slide coefficients are only mildly affected by inflation pressure. On wet surfaces, inflation pressure increases are known to significantly improve both coefficients.
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Speed On dry roads, both peak and slide coefficients decrease with velocity as illustrated in Figure 10.9. Under wet conditions, even greater speed sensitivity prevails because of the difficulty of displacing water in the contact patch at high speeds. When the speed and water film thickness are sufficient, the tire tread will lift from the road creating a condition known as hydroplaning.
Sliding coefficient as a function of speed on various surfaces
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11. Automotive Chassis Materials Before deciding which material is most suitable for any particular component, we clearly need to know something about material properties, and the main properties of concern to us are: • • • • • • • •
Strength Stiffness Density (or specific gravity) Ductility Fatigue resistance Available joining methods Cost of material Cost of machining and working
Top left shows the meaning of the term stress. The significance of strain is shown below that. A typical stress strain curve for steel is on the right. The initial slope of the line is the Young’s Modulus. The stress strain curve shows the typical performance of a non-brittle material such as the grades of steel used in frame construction. If we subject a piece of the material to a stress below the yield limit then a certain degree of strain occurs, as explained above, but this is elastic strain and when we remove that stress then the material returns to its original unstrained shape and size. This is called elastic deformation because it behaves like a spring. However, if we attempt to apply a higher stress than the yield point, then the material gives and deforms permanently. When the stress is removed the object does not return to its original condition. This is known as plastic deformation. When we continue to apply sufficient load beyond the yield point, we reach the point of ultimate failure and the material actually breaks. The amount of strain that occurs between the yield point and the failure point is a measure of the materials ductility.
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Density is a measure of mass per unit volume; hence, size for size, it compares the masses of different materials. We get the same comparison from specific gravity, since that is just the density of any material compared with that of water under standard conditions. The above properties are a rough guide only, as the tensile strength may vary considerably, depending on the metal composition or alloy and its state of heat treatment and working. In particular the tubing used for frame construction will lose some strength after welding, and composites vary considerably. The specific gravity and Young’s Modulus do not vary in this way. In the above table, the term “relative stiffness” means the ratio of Young’s Modulus to specific gravity referenced to that of steel, which is a measure of stiffness per unit weight. Thus, the most efficient way to use light-weight materials is to make the sections as large as possible consistent with maintaining a practical wall thickness. But, in maintaining similar structural characteristics to those of steel, our light alloy tube will weigh more than a simple comparison of density indicates. The density of aluminum is 33 per cent that of steel but the structural weights of our bar and tube in the foregoing examples are 58 and 70 per cent respectively. The terms chrome-moly, T45, 4130 and 531 are frequently bandied about as though they have some magical significance, implying extra stiffness and lightness, to such steels. In fact, these terms are simply standards or commercial references and refer to steels with alloying elements calculated to enhance strength, particularly strength after welding. Their Young’s modulus, hence stiffness, is no different from that of other steel alloys, nor is their density.
A Reynolds trade name, 531 is often referred to as chrome-moly, whereas it is actually a manganese molybdenum steel, which Reynolds claim has superior properties to those of a chrome-molybdenum steel. For many years this tube type
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was a favorite amongst British specialist frame builders. The main alloying elements in Reynolds 531 are as follows:
Its minimum strength properties are:
These figures indicate the excellent retention of strength after brazing, which is a great boon. The use of this and other high-strength tubing is normally confined to competition machines, for roadsters the extra cost is not usually warranted. Now that we have dealt with the principles underlying the selection of materials, let us consider the choices open for various components.
Frame Steel is easily the most common material here, either as tube or sheet, depending on design. There are several reasons for its choice, viz: • • • •
Raw material cost is relatively low. Well-developed manipulating and joining techniques are available. Young’s Modulus is high, so the required stiffness can be obtained with small tube sizes. Aluminum has often been used for specials and racing machines in the form of monocoques and large section backbones such as the fabricated Ossa and Kawasaki mentioned earlier. Cast-aluminum backbones have been tried by Eric Offenstadt in France and Terry Shepherd in England. However, components such as complete frames are rarely cast because the minimum material thickness needed for the casting process usually results in excessively heavy components.
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Then tubular aluminum frames started to appear on works racers, with Yamaha taking the initiative. This trend started cautiously, when just the pivoted rear fork was made in light alloy, before spreading to the complete chassis. In the development of aluminum frames, however, it is interesting to note that tube sizes increased rapidly to compensate for the low Young’s Modulus, as explained earlier. A great help in this context would be the spread of proper triangulation. In GP racing now, the use of aluminum alloy fabricated twin-spar frames is almost universal, and is also widely featured on expensive sports models for the street. It must be remembered that the fatigue characteristics of aluminum are such that failure is inevitable eventually in components subjected to alternating stress, hence limited life must be accepted. In the case of works racers, their natural rapid obsolescence makes this less of a serious problem.
Wheels For most of motorcycle history, the traditional wheel was a composite of hub, spokes and rim. Hubs have been made in steel, cast iron, aluminum and magnesium. In the days of drum brakes, the light alloy hubs usually had a cast-iron brake drum. Although some people experimented with various forms of plating or other hard surfacing direct on the drum surface to improve heat dissipation and save weight. Spokes were of steel, sometimes titanium, usually with brass nipples, though these were sometimes in aluminum for racing. Rims have mostly been of steel, except that aluminum took over for sports and competition machines and some roadsters. Since the late 1960s, however, cast wheels have become increasingly popular, first for racing (where magnesium predominates) then on roadsters, where cost and corrosion problems favor aluminum. Even cheap mopeds now use die-cast aluminum wheels. In magnesium, a properly designed cast wheel may well be lighter than a steelspoked wheel with an aluminum rim and magnesium hub; but cast-aluminum wheels usually have a weight penalty though in some cases they may be stiffer laterally and run more accurately. 68 | P a g e
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An ingenious sheet-aluminum design by Tony Dawson consists of left and right pressings riveted together at the rim and bolted to a cast hub. The higher strength of the wrought material used enabled these wheels to compete with cast magnesium for weight, while the greater ductility of the sheet material gives a high safety factor. It would be interesting to see this technique tried with magnesium sheet. Honda developed a multi-part wheel called the Comstar. As with conventional wire spoked wheels this comprised separate rim, hub and spokes, but where it was different was in the spokes. In place of the normal wire spokes they used aluminum stampings and these were bolted to the hub and riveted to the rim. The rims for these wheels had a rib running around the inner circumference on which to fix the spokes. A similar rim can also be used in another type of composite wheel. The hub and spokes are cast, like a complete cast wheel without the rim, and the end of the spokes are machined to fit the aforementioned rib inside the rim. This form of construction is useful for low volume production “specials� because it is considerably cheaper to make patterns and castings made and machined than for full cast wheels. It also has the advantage that various width rims can be tried without the expense of new castings. Compared to full cast wheels it has the disadvantage that the rim would not run so true, although it will likely spin truer than a conventional spoked wheel. Standard aluminum rims are available with this inner rib and the central spider could be cast in either aluminum or magnesium. Where expense was of little concern, complete wheels have been machined from an Aluminum billet and this has become a more practical proposition for one-offs and show machines, with the spread of CNC machine tools.
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Fuel Tank Steel is the traditional material here for roadsters, aluminum for racers. To prevent cracking, care must be taken to isolate aluminum tanks from vibration. Plastic tanks – both glass fibre-reinforced and moulded thermoplastics (ABS or similar) – have been successfully used for competition duty (particularly on off-road machines) but the Construction and Use regulations forbid the use of non-metallic tanks on public roads in Britain. As with many other components Carbon Fibre reinforced material is now making an appearance in fuel tanks also.
Bodywork The use of steel or aluminum for seats, mudguards, fairings and suchlike has been largely superseded in racing by reinforced plastics. Initially this was GRP or Glass Reinforced Plastic, polyester being the plastic or resin most used. This has been overtaken by the use of Carbon Fibre Reinforced Plastic, polyester has given way to the stronger and more stable epoxy resin. Carbon fibre has the advantage of having a very high Young’s modulus, that is, it is very stiff. Some of this stiffness is given up when imbedded in the epoxy but the overall resulting composite material is still stiffer than most other forms of construction. This enables thin and hence light weight panels and shapes to be moulded, without undue flexibility in the finished component. Like GRP, carbon fibre parts can be made at home or in a small workshop, but for the best results the work needs to be done with specialist facilities. The final setting or hardening of the material is done in autoclaves (ovens) and some form of pressure moulding (such as vacuum bagging) is best to ensure an even thickness and uniform matrix. It is important to expel any air trapped in the liquid resin. Working with the 70 | P a g e
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resins used in composite materials can be hazardous and appropriate precautions and protective clothing should always be worn. On road machines, too, metal is being ousted for these components in order to save weight, but in this case thermoplastic mouldings are commonly used, some of which have greater flexibility, which reduces the chance of permanent damage in a minor accident. A disadvantage, however, is their tendency to look tatty in time as a result of scratching and other surface blemishes.
Framework Design A vehicle frame, also known as its chassis, is the main supporting structure of a motor vehicle, to which all other components are attached, comparable to the skeleton of an organism. Until the 1930s virtually every car had a structural frame, separate from its body. This construction design is known as body-on-frame. Over time, nearly all passenger cars have migrated to unibody construction, meaning their chassis and bodywork have been integrated into one another. Nearly all trucks, buses, and most pickups continue to use a separate frame as their chassis. Function The main functions of a frame in motor vehicles are: 1. To support the vehicle's mechanical components and body 2. To deal with static and dynamic loads, without undue deflection or distortion. 3. These include: ● Weight of the body, passengers, and cargo loads. ● Vertical and torsional twisting transmitted by going over uneven surfaces. ● Transverse lateral forces caused by road conditions, side wind, and steering the vehicle. ● Torque from the engine and transmission. ● Longitudinal tensile forces from starting and acceleration, as well as compression from braking. ● Sudden impacts from collisions.
Types of frame according to the construction: • Ladder type frame • X-Type frame • Off set frame • Off set with cross member frame 71 | P a g e
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Perimeter Frame
Frame Rails Typically, the material used to construct vehicle chassis and frames is carbon steel; or aluminum alloys to achieve a more light-weight construction. In the case of a separate chassis, the frame is made up of structural elements called the rails or beams. These are ordinarily made of steel channel sections, made by folding, rolling or pressing steel plate. There are three main designs for these. If the material is folded twice, an open-ended cross-section, either C-shaped or hat-shaped (Ushaped) results. "Boxed" frames contain chassis rails that are closed, either by somehow welding them up, or by using pre-manufactured metal tubing. C-Shape
By far the most common, the C-channel rail has been used on nearly every type of vehicle at one time or another. It is made by taking a flat piece of steel (usually ranging in thickness from 1/8" to 3/16", but up to 1/2" or more in some heavy-duty trucks) and rolling both sides over to form a C-shaped beam running the length of the vehicle. Hat
Hat frames resemble a "U" and may be either right-side-up or inverted with the open area facing down. Not commonly used due to weakness and a propensity to rust, however they can be found on 1936–1954 Chevrolet cars and some Studebakers. High performance custom frame, using boxed rails and tube sections. Abandoned for a while, the hat frame gained popularity again when companies started welding it to the bottom of unibody cars, in effect creating a boxed frame.
Boxed
Originally, boxed frames were made by welding two matching C-rails together to form a rectangular tube. Modern techniques, however, use a process similar to 72 | P a g e
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making C-rails in that a piece of steel is bent into four sides and then welded where both ends meet. In the 1960s, the boxed frames of conventional American cars were spot-welded here and there down the seam; when turned into NASCAR "stock car" racers, the box was continuously welded from end to end for extra strength.
Design Features While appearing at first glance as a simple form made of metal, frames encounter great amounts of stress and are built accordingly. The first issue addressed is beam height, or the height of the vertical side of a frame. The taller the frame, the better it is able to resist vertical flex when force is applied to the top of the frame. This is the reason semi-trucks have taller frame rails than other vehicles instead of just being thicker. As looks, ride quality, and handling became more important to consumers, new shapes were incorporated into frames. The most visible of these are arches and kickups. Instead of running straight over both axles, arched frames sit lower—roughly level with their axles—and curve up over the axles and then back down on the other side for bumper placement. Kick-ups do the same thing, but don't curve down on the other side, and are more common on front ends. Another feature seen are tapered rails that narrow vertically and/or horizontally in front of a vehicle's cabin. This is done mainly on trucks to save weight and slightly increase room for the engine since the front of the vehicle does not bear as much of a load as the back. Design developments include frames that use more than one shape in the same frame rail. For example, some pickup trucks have a boxed frame in front of the cab, shorter, narrower rails underneath the cab, and regular C-rails under the bed. On perimeter frames, the areas where the rails connect from front to center and center to rear are weak compared to regular frames, so that section is boxed in, creating what is known as torque boxes.
Types of Frame Ladder frame
So, named for its resemblance to a ladder, the ladder frame is one of the simplest and oldest of all designs. It consists of two symmetrical beams, rails, or channels running the length of the vehicle, and several transverse cross-members connecting them. Originally seen on almost all vehicles, the ladder frame was gradually phased out on cars in favor of perimeter frames and unitized body construction. It is now seen mainly on trucks. This design offers good beam resistance because of its 73 | P a g e
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continuous rails from front to rear, but poor resistance to torsion or warping if simple, perpendicular cross-members are used. Also, the vehicle's overall height will be greater due to the floor pan sitting above the frame instead of inside it.
Unibody
The term unibody or unit body is short for unitized body, or alternatively unitary construction design. It is traditional body-on-frame architecture has shifted to the lighter unitized body structure that is now used on most cars. Integral frame and body construction require more than simply welding an unstressed body to a conventional frame. In a fully integrated body structure, the entire car is a loadcarrying unit that handles all the loads experienced by the vehicle—forces from driving as well as cargo loads. Integral-type bodies for wheeled vehicles are typically manufactured by welding preformed metal panels and other components together, by forming or casting whole sections as one piece, or by a combination of these techniques. Although this is sometimes also referred to as a monocoque structure, because the car's outer skin and panels are made load-bearing, there are still ribs, bulkheads and box sections to reinforce the body, making the description semimonocoque more appropriate. Backbone Tube
A backbone chassis is a type of automobile construction chassis that is similar to the body-on-frame design. Instead of a two-dimensional ladder type structure, it consists of a strong tubular backbone (usually rectangular in cross section) that connects the front and rear suspension attachment areas. A body is then placed on this structure.
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X-frame
This is the design used for the full-size American models of General Motors in the late 1950s and early 1960s in which the rails from alongside the engine seemed to cross in the passenger compartment, each continuing to the opposite end of the cross member at the extreme rear of the vehicle. It was specifically chosen to decrease the overall height of the vehicles regardless of the increase in the size of the transmission and propeller shaft humps, since each row had to cover frame rails as well. Several models had the differential located not by the customary bar between axle and frame, but by a ball joint atop the differential connected to a socket in a wishbone hinged onto a cross member of the frame. The X-frame was claimed to improve on previous designs, but it lacked side rails and thus did not provide adequate side-impact and collision protection.[18] This design was replaced by perimeter frames. Perimeter Frame
Similar to a ladder frame, but the middle sections of the frame rails sit outboard of the front and rear rails just behind the rocker / sill panels. This was done to allow for a lower floor pan, especially at the passenger footwells, to lower the passengers' seating height and therefore reduce the overall vehicle height in passenger cars. This became the prevalent design for body-on-frame cars in the United States, but not in the rest of the world, until the uni-body gained popularity. It allowed for annual model changes introduced in the 1950s to increase sales, but without costly structural changes. As of 2014, there are no perimeter frame automobiles sold in the United States after the Ford Motor Company phased out the Panther platform in 2011, which ended the perimeter frame passenger car in the United States (the Chevrolet Corvette has used a variation of the perimeter frame since 1963, but its fourth generation variant to its current generation as of 2016 has elements of the perimeter frame integrated with an internal endoskeleton which serves as a clamshell). In addition to a lowered roof, the perimeter frame allows lower seating positions when that is desirable, and offers better safety in the event of a side impact. However, the design lacks stiffness, because the transition areas from front to 75 | P a g e
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center and center to rear reduce beam and torsional resistance, and is used in combination with torque boxes and soft suspension settings. Platform Frame
This is a modification of the perimeter frame, or of the backbone frame, in which the passenger compartment floor, and sometimes also the luggage compartment floor, have been integrated into the frame as loadbearing parts, for extra strength and rigidity. Neither floor pieces are simply sheet metal straight off the roll, but have been stamped with ridges and hollows for extra strength. Platform chassis were used on several successful European cars. The most wellknown of this is the Volkswagen Beetle, on which it is called body on pan construction. Another German example are the Mercedes-Benz "Ponton" cars of the 1950s and 1960s,[19] where it was called a "frame floor" in English-language advertisements. The French Renault 4 of which over eight million were made, also used a platform frame. The frame of the Citroen 2CV represents a more minimal interpretation of a platform chassis. Space frame
In a (tubular) spaceframe chassis, suspension, engine, and body panels are attached to a three-dimensional skeletal frame of tubes, and the body panels have little or no structural function. In order to maximize rigidity and minimize weight, the design makes maximum use of triangles, and all the forces in each strut are either tensile or compressive, never bending, so they can be kept as thin as possible.
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Subframe
A subframe is a distinct structural frame component, to reinforce or complement a particular section of a vehicle's structure. Typically attached to a unibody or monocoque, the rigid subframe can handle high chassis forces and can transfer them evenly to a wide area of relatively thin sheet metal of a unitized body shell. Subframes are often found at the front or rear end of cars, and are used to attach the suspension to the vehicle. A subframe may also contain the engine and transmission. It is normally of box steel construction, but may be tubular. Monocoque
A monocoque chassis is a structure which integrates body and chassis together to form a composite structure which has better stiffness as well as weight advantage. In a monocoque chassis the stress generated by the vehicle during motion is being distributed among the structure and does not form localized stress which may have higher value of deformation. As the stress is being distributed equally among the structure the torsional stiffness of the chassis is high which proves advantageous for the suspension as they can be designed to be more robust and increases the performance of the vehicle. It proves to be a great balance between strength and weight which ultimately increases performance. This form of chassis is now a days being adopted by various segments of vehicle from its inception in F1 which later was adopted to be used for sports cars and now SUV even. The performance of the structure depends on another important factor i.e., the material used to build the structure. The range of material used are from carbon titanium fibre used in Pagani huayra to Mahindra XUV 500 where aluminum is used. It depends on the type of vehicle and the required performance specifications.
Hinge Points The question of hinge strength often arises during the design of the enclosure. Determining the strength of the individual hinges is fairly straightforward, but 77 | P a g e
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relating the strength predictions to real-life situations can be a challenge. The dimensions of the door, the position of the center of gravity, the position of the hinges, and the installation tolerances profoundly affect the load-carrying capability of a hinge. The most common enclosure-door orientation has hinges in a vertical plane. Nontrivial out-of-plane loads render simple tensile testing of single hinges meaningless. When sizing such a door, the engineer must consider vertical load from the weight of the door, load sharing between hinges, horizontal loads caused by door and hinge geometry, gasket force against the door, and shock loading.
Vertical loading The vertical load from the weight of the door can be easily calculated as the total weight of the door plus anything hanging from it. W = (md + ms) g where md = mass of the door, ms = mass of anything suspended on the door, and g = gravitational constant, 9.8 m/sec2. If we assume the door has two hinges aligned vertically, the vertical force is divided equally between them: W = FA + FB Equal load distribution between hinges requires the hinges be made exactly to nominal dimensions and installed precisely. Tolerances in hinge manufacture or placement cause the load to be distributed unequally. In the extreme case shown in the figure, the lower hinge takes all the vertical force because the gap between the two halves of the upper hinge prevents load transfer between the door and the frame at that location. Neither the hinges nor the door is perfectly rigid, however. Hinge parts or the door itself can deflect under the uneven force so the unloaded hinge may pick up some of the vertical load. Softer hinge materials such as glass reinforced nylon may make up for their reduced strength by sharing load more equally. This permits more leeway for manufacturing tolerance and imperfect installation.
Horizontal loading Although the main force on the door is vertical, the load on the hinges also has a horizontal component in the plane of the door. The center of gravity of the door is cantilevered off the hinges, resulting in an induced moment. The hinges see this moment as a horizontal load at the hinge points. Heavier and wider doors, therefore, generate greater horizontal forces on the hinges. A simple rectangular door will have its CG at its center. Varying thickness, 78 | P a g e
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cutouts, or suspended loads can move the CG away from the center and affect the moment on the hinges accordingly. Wider hinge spacing reduces the horizontal force. Because of the nature of the moment, a third hinge at the pivot point will not take a significant amount of the horizontal loading. Similarly, a door CG which is above or below the midpoint between the two hinges will result in uneven horizontal loading. The moment from the weight of the door is: M=WxY where Y = the distance between the door CG and the hinge line. The moment M is reacted by horizontal loads C and D on the upper and lower hinges, respectively: M = (ZC x C) + (ZD x D) where ZC and ZD = the distances from the pivot point to the upper and lower hinges, respectively.
12.Transmission System and Drive Train
Transmission in Electric Vehicles Typical assumption: “Electric Vehicles do not require multi speed transmissions�: 1. Electric motor can deliver high torque at 0 rpm (stall torque) 2. Electric motor can cover wide speed range (e.g. up to 14 000 rpm) 3. Peak power can be delivered in wide speed range The electric motors on board electric vehicles rev to a significantly higher rate than conventional diesel or petrol engines. A typical electric vehicle motor can rev up to 20,000rpm, far higher than the usual 4,000-6,000rpm limit found in conventional cars.
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Why multi speed transmissions are not desired for electric vehicles: 1. 2. 3. 4.
Multi Multi Multi Multi
Speed Speed Speed Speed
transmissions inefficient transmissions are too large and too heavy transmissions are expensive transmissions are uncomfortable in an electric vehicle
Transmission in Conventional Vehicles It is clear and that there is a need for multi speed transmissions in combination with internal combustion engines: 1. No torque at 0 rpm 2. Limited speed range (e.g. up to 6000 rpm) 3. Peak power is delivered at one specific speed 4. More speeds is better (e.g. 8 speed, 9 speed, CVT,)
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a) Manual Gearbox
A manual transmission, also known as a manual gearbox, a standard transmission, is a type of transmission used in motor vehicle applications. It uses a driver-operated clutch, usually engaged and disengaged by a foot pedal or hand lever, for regulating torque transfer from the engine to the transmission; and a gear selector that can be operated by hand. A conventional 4- or 5-speed manual transmission is often the standard equipment in a modern base model vehicle, with 4-speed being more common in non-passenger vehicles such as pickup trucks and light commercial vehicles. Higher end vehicles, such as sports cars and luxury cars are often usually equipped with a 6-speed transmission for the base model.
b) Semi-Automatic Gearbox
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A semi-automatic transmission (also known as a clutch less manual transmission, auto-manual, automated manual transmission, trigger shift, flappy-paddle gear shift or paddle-shift gearbox) is an automobile transmission that combines manual transmission and automatic transmission. A clutch less manual facilitates gear changes by dispensing with the need to press the clutch pedal at the same time as changing gears. It uses electronic sensors, pneumatics, processors and actuators to execute gear shifts on input from the driver or by a computer. This removes the need for a clutch pedal, which the driver otherwise needs to depress before making a gear change, since the clutch itself is actuated by electronic equipment which can synchronize the timing and torque required to make quick, smooth gear shifts. The system was designed by automobile manufacturers to provide a better driving experience through fast overtaking maneuvers on highways.
c) Automatic Gearbox
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An automatic transmission, also called auto, self-shifting transmission, n-speed automatic (where n is its number of forward gear ratios), or AT, is a type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually. Like other transmission systems on vehicles, it allows an internal combustion engine, best suited to run at a relatively high rotational speed, to provide a range of speed and torque outputs necessary for vehicular travel. The number of forward gear ratios is often expressed for manual transmissions as well (e.g., 6-speed manual). The most popular form found in automobiles is the hydraulic planetary automatic transmission. Similar but larger devices are also used for heavy-duty commercial and industrial vehicles and equipment. This system uses a fluid coupling in place of a friction clutch, and accomplishes gear changes by hydraulically locking and unlocking a system of planetary gears. These systems have a defined set of gear ranges, often with a parking pawl that locks the output shaft of the transmission to keep the vehicle from rolling either forward or backward.
Propeller shaft
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A drive shaft, propeller shaft, is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement between them. As torque carriers, drive shafts are subject to torsion and shear stress, equivalent to the difference between the input torque and the load. They must therefore be strong enough to bear the stress, while avoiding too much additional weight as that would in turn increase their inertia.
Differential A differential is a system that transmits an engine’s torque to the wheels. The differential takes the power from the engine and splits it, allowing the wheels to spin at different speeds. A vehicle with two drive wheels has the problem that when it turns a corner the drive wheels must rotate at different speeds to maintain traction. The automotive differential is designed to drive a pair of wheels while allowing them to rotate at different speeds. In vehicles without a differential, such as karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism. When cornering, the inner wheel travels a shorter distance than the outer wheel, so without a differential either the inner wheel rotates too quickly or the outer wheel rotates too slowly, which results in difficult and unpredictable handling, damage to tires and roads, and strain on (or possible failure of) the drivetrain. In rear-wheel drive automobiles the central drive shaft (or prop shaft) engages the differential through a hypoid gear (ring and pinion). The ring gear is mounted on the carrier of the planetary chain that forms the differential. This hypoid gear is a bevel gear that changes the direction of the drive rotation.
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a) Open Differential
The cars are equipped with Open Differential are designed for running on the dry patches and city roads which are generally smooth and doesn’t require any extra effort from the machine. But it certainly has its own limitations. The one thing that people often stumbles upon is when a tire loses traction, all the torque is supplied to that tire, which is apparently not true. In reality, the sent torque is low, as the required torque is also low. Such a differential can cause the wheel to rotate in different directions, which will ultimately toss up some or the other issue. For instance, if two tires of a car lose traction, the one with no traction spins, while the other with traction doesn’t offer much. Thus, the Open Differential out-turn equal torque to both tires.
b) Limited Slip Differential
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Limited Slip Differentials churns out more traction as compared to the Open Differential. It employs the clutch to drive the tires and slips automatically on the turns. The Limited Slip Differential is smart enough to sense when the wheel loses its traction and binds it with others through various methods. It doesn’t let the other wheel to spin in altogether different alignment. This way, the machine is pushed forward, even if one wheel has less traction. And when the ratio between rubber and the terrain breaks, there comes out the burnout; the true essence of a complete car.
c) Torsen Differential
Torsen Torque-Sensing is a type of limited-slip differential used in automobiles. The Torsen functions as an open differential as long as the amount of torque transmitted to each rear wheel remains equal. When one tire begins to lose traction, the Torsen instantly senses the change in torque being applied to the ground. The excess torque that cannot be delivered to the ground by the tire that is beginning 86 | P a g e
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to lose traction is delivered to the opposite tire, which has better traction and can take more torque. The Torsen's unique torque-sensing ability keeps engine power going to the ground during changing traction conditions.
13. Braking System
A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Most brakes commonly use friction between two surfaces pressed together to convert the kinetic energy of the moving object into heat, though other methods of energy conversion may be employed. Most modern cars have brakes on all four wheels, operated by a hydraulic system. The brakes may be disc type or drum type. The front brakes play a greater part in stopping the car than the rear ones, because braking throws the car weight forward onto the front wheels. Many cars therefore have disc brakes, which are generally more efficient, at the front and drum brakes at the rear. All-disc braking systems are used on some expensive or high-performance cars, and all-drum systems on some older or smaller cars.
Brake hydraulics A hydraulic brake circuit has fluid-filled master and slave cylinders connected by pipes. When you push the brake pedal it depresses a piston in the master cylinder, forcing fluid along the pipe. The fluid travels to slave cylinders at each wheel and fills them, forcing pistons out to apply the brakes. Fluid pressure distributes itself evenly around the system.
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The combined surface 'pushing' area of all the slave pistons is much greater than that of the piston in the master cylinder. Consequently, the master piston has to travel several inches to move the slave pistons the fraction of an inch it takes to apply the brakes. This arrangement allows great force to be exerted by the brakes, in the same way that a long-handled lever can easily lift a heavy object a short distance. Most modern cars are fitted with twin hydraulic circuits, with two master cylinders in tandem, in case one should fail. Sometimes one circuit works the front brakes and one the rear brakes; or each circuit works both front brakes and one of the rear brakes; or one circuit works all four brakes and the other the front ones only. Under heavy braking, so much weight may come off the rear wheels that they lock, possibly causing a dangerous skid. For this reason, the rear brakes are deliberately made less powerful than the front.
Types a) Disc Brake
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A disc brake has a disc that turns with the wheel. The disc is straddled by a caliper, in which there are small hydraulic pistons worked by pressure from the master cylinder. The pistons press on friction pads that clamp against the disc from each side to slow or stop it. The pads are shaped to cover a broad sector of the disc. There may be more than a single pair of pistons, especially in dual-circuit brakes. The pistons move only a tiny distance to apply the brakes, and the pads barely clear the disc when the brakes are released. They have no return springs. When the brake is applied, fluid pressure forces the pads against the disc. With the brake off, both pads barely clear the disc. Rubber sealing rings round the pistons are designed to let the pistons slip forward gradually as the pads wear down, so that the tiny gap remains constant and the brakes do not need adjustment. Many later cars have wear sensors leads embedded in the pads. When the pads are nearly worn out, the leads are exposed and short-circuited by the metal disc, illuminating a warning light on the instrument panel.
b) Drum Brake
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A drum brake has a hollow drum that turns with the wheel. Its open back is covered by a stationary backplate on which there are two curved shoes carrying friction linings. The shoes are forced outwards by hydraulic pressure moving pistons in the brake's wheel cylinders, so pressing the linings against the inside of the drum to slow or stop it. With the brakes on, the shoes are forced against the drums by their piston. Each brake shoe has a pivot at one end and a piston at the other. A leading shoe has the piston at the leading edge relative to the direction in which the drum turns. The rotation of the drum tends to pull the leading shoe firmly against it when it makes contact, improving the braking effect. Some drums have twin leading shoes, each with its own hydraulic cylinder; others have one leading and one trailing shoe - with the pivot at the front.
14. Suspension Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support both road holding/handling and ride quality, which 90 | P a g e
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are at odds with each other. The tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the road or ground forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different.
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Independent Suspension Independent suspension is a kind of suspension in which wheel travel takes place independently in the same axle.
a) MacPherson Strut Suspension
A MacPherson strut uses a wishbone, or a substantial compression link stabilized by a secondary link, which provides a bottom mounting point for the hub carrier or axle of the wheel. This lower arm system provides both lateral and longitudinal location of the wheel. The upper part of the hub carrier is rigidly fixed to the bottom of the outer part of the strut proper; this slides up and down the inner part of it, which extends upwards directly to a mounting in the body shell of the vehicle. The line from the strut's top mount to the bottom ball joint on the control arm gives the steering axis inclination. The strut's axis may be angled inwards from the steering axis at the bottom, to clear the tyre; this makes the bottom follow an arc when steering.
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b) Double wishbone Suspension
In automobiles, a double wishbone suspension is an independent suspension design using two (occasionally parallel) wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckle. The shock absorber and coil spring mount to the wishbones to control vertical movement. Double wishbone designs allow the engineer to carefully control the motion of the wheel throughout suspension travel, controlling such parameters as camber angle, caster angle, toe pattern, roll center height, scrub radius, scuff and more. Double wishbone suspension allows each wheel to act and react independently from the others. It achieves this thanks to two wishbone-shaped arms (also known as control arms or double A-arms) that are located between the knuckle on the wheel assembly and the car’s chassis. The upper and lower control arms have ball joints on both ends to allow movement in multiple directions. Vertical movement is controlled through the shock absorber and coil spring which are mounted on the wishbones. By carefully adjusting the relationship between the upper and lower control arms’ lengths and relative angles, a technician can modify the car’s ride and handling. This includes controlling the wheel’s motions, via parameters like camber angle, caster angle, toe pattern, roll centre height, scrub radius and scuff.
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Semi Independent Suspension In a semi-independent suspension, the wheels of an axle are able to move relative to one another as in an independent suspension but the position of one wheel has an effect on the position and attitude of the other wheel. This effect is achieved via the twisting or deflecting of suspension parts under load. The most common type of semi-independent suspension is the twist beam.
Twist Beam
The twist-beam rear suspension (also torsion-beam axle or deformable torsion beam) is a type of automobile suspension based on a large H or C shaped member. The front of the H attaches to the body via rubber bushings, and the rear of the H carries each stub-axle assembly, on each side of the car. The cross beam of the H holds the two trailing arms together, and provides the roll stiffness of the suspension, by twisting as the two trailing arms move vertically, relative to each other.
Dependent Suspension
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If one tyre moves, other shows movement corresponding to that. These are not in much use nowadays but being cheaper compared to independent, they can be used. Because it assures constant camber, dependent suspension is most common on vehicles that need to carry large loads as a proportion of the vehicle weight, that have relatively soft springs and that do not (for cost and simplicity reasons) use active suspensions. The use of dependent front suspension has become limited to heavier commercial vehicles.
De-Dieo Suspension
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A de Dion tube is an automobile suspension technology. It is a sophisticated form of non-independent suspension and is a considerable improvement over the swing axle, Hotchkiss drive, or live axle. Because it plays no part in transmitting power to the drive wheels, it is sometimes called a "dead axle". De Dion suspension uses universal joint at both the wheel hubs and differential, and uses a solid tubular beam to hold the opposite wheels in parallel. Unlike an anti-roll bar, a de Dion tube is not directly connected to the chassis nor is it intended to flex. In suspension geometry it is a beam axle suspension.
Suspension Technologies Active Suspension
Active suspension is a type of automotive suspension that controls the vertical movement of the wheels relative to the chassis or vehicle body with an onboard system, rather than in passive suspension where the movement is being determined entirely by the road surface. Active suspensions can be generally divided into two classes: pure active suspensions, and adaptive/semi-active suspensions. While adaptive suspensions only vary shock absorber firmness to match changing road or 96 | P a g e
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dynamic conditions, active suspensions use some type of actuator to raise and lower the chassis independently at each wheel. These technologies allow car manufacturers to achieve a greater degree of ride quality and car handling by keeping the tires perpendicular to the road in corners, allowing better traction and control. An onboard computer detects body movement from sensors throughout the vehicle and, using that data, controls the action of the active suspensions. The system virtually eliminates body roll and pitch variation in many driving situations including cornering, accelerating, and braking. It is extremely suitable for leveling a car during accelerating, braking and cornering, or for taking care of static load variations.
Semi Active Suspension
Semi-active systems can only change the viscous damping coefficient of the shock absorber, and do not add energy to the suspension system. Semi-active suspensions have time response close to a few milliseconds and can provide a wide range of damping values. Therefore, semi-active suspensions modify the damping in real time, depending on the road conditions and the dynamics of the car. Though limited in their intervention (for example, the control force can never have different direction than the current vector of velocity of the suspension), semi-active suspensions are less expensive to design and consume far less energy. In recent times, research in semi-active suspensions has continued to advance with respect to their capabilities, narrowing the gap between semi-active and fully active suspension systems. 97 | P a g e
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Magnetorheological damper
A magnetorheological damper or magnetorheological shock absorber is a damper filled with magnetorheological fluid, which is controlled by a magnetic field, usually using an electromagnet. This allows the damping characteristics of the shock absorber to be continuously controlled by varying the power of the electromagnet. Fluid viscosity increases within the damper as electromagnet intensity increases. This type of shock absorber has several applications, most notably in semi-active vehicle suspensions which may adapt to road conditions, as they are monitored through sensors in the vehicle, and in prosthetic limbs. A magnetorheological damper is controlled by algorithms specifically designed for the purpose. There are plenty of alternatives, such as skyhook or ground hook algorithms. The idea of the algorithms is to control the yield point shear stress of the magnetorheological fluid with an electric current. When the fluid is in the presence of an applied magnetic field, the suspended metal particles align according to the field lines. Viscosity of the fluid increases according to the intensity of the magnetic field. When this occurs at the right instant, the properties of the damper change helps in attenuating an undesired shock or vibration. The relative efficacy of magnetorheological dampers to active and passive control strategies is usually comparable.
Inboard suspension points These are the factors that need to be considered to decide 98 | P a g e
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the inboard pick up points:
a) Anti-Dive
Anti-features are to be added to the suspension to stop pitching of the vehicle. More anti-percentage simply means that more load is going to the A-arms rather than through the springs. This prevents vehicle pitching. Setting Anti features is a matter of experience and is generally kept between 0-20 percent. As the inboard pickup points affect the Side View Geometry the percent anti-dive also gives a fair idea about the placement of the inboard pickup points.
b) Anti-Squat
c) Roll Centre Migration Roll Centre migration also affects the inboard pickup points. The roll centre migration follows a trend where in the migration reduces drastically if the lower wishbone length is increased compared to the upper wishbone length. Thus, the inboard wishbone points can be kept under the chassis if space is available to make 99 | P a g e
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the lower wishbone longer while keeping the upper wishbone pick up points at their desired position relative to chassis design. Roll centre static height
As the front view IC is determined by the inboard pickup points, by changing the position of the inboard pick up points along the Z axis, the static roll centre height can be fixed. The static roll centre height at the front is generally kept greater than the rear to allow the rear of the car to catch up during cornering with the front. However too high a roll centre will cause jacking which is unwanted.
d) Anti-Roll Bar The anti-roll bar itself is a simple piece of engineering. It’s essentially a U-shaped cylindrical piece of metal that connects both the left and right ends of an axle. When you round a corner, the mass of your car shifts to the outside of the turn due to centrifugal force, causing the car to “roll”. By connecting both ends, the anti-roll bar forces both ends of the axle – the wheels in this case – to raise or lower to a similar
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height, preventing roll. The bar resists twisting, or torsion, through its torsional rigidity. The stiffer the bar, the less the car leans in turns. One benefit of such bars is that the vehicle can be made to lean less without increasing the stiffness of the suspension, which compromises ride quality. Some bars are even adjustable via the positions of the mounting position of the bar to the end links, or through a computercontrolled setup.
15. Steering System
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The steering system converts the rotation of the steering wheel into a swiveling movement of the road wheels in such a way that the steering-wheel rim turns a long way to move the road wheels a short way. The system allows a driver to use only light forces to steer a heavy car. The rim of a 15 in. (380 mm) diameter steering wheel moving four turns from full left lock to full right lock travels nearly 16 ft (5 m), while the edge of a road wheel moves a distance of only slightly more than 12 in. (300 mm). If the driver swiveled the road wheel directly, he or she would have to push nearly 16 times as hard. The steering effort passes to the wheels through a system of pivot joints. These are designed to allow the wheels to move up and down with the suspension without changing the steering angle. They also ensure that when cornering, the inner front wheel - which has to travel round a tighter curve than the outer one - becomes more sharply angled. The joints must be adjusted very precisely, and even a little looseness in them makes the steering dangerously sloppy and inaccurate.
Steering System Technologies a) Hydraulic Power steering
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Hydraulic fluid Power steering fluid is a sub type of hydraulic fluid. Most are mineral oil or siliconebased fluids, while some use automatic transmission fluid, made from synthetic base oil. Automatic transmissions use fluids for their lubrication, cooling and hydraulic properties for viscous couplings. Use of the wrong type of fluid can lead to failure of the power steering pump Steering fluid reservoir Just like how we have a petrol tank for petrol, we have a steering fluid tank for steering fluid. Whenever we are using fluid, we always have a container that holds them when we are not using them. There is nothing too fancy about this part here, and its purpose is quite selfexplanatory too. But, the journey of a hydraulic power steering begins here. When we fill the steering fluid, we put it into this reservoir. It holds the fluid, and supplies them to the steering pump through rubber hoses.
Steering pump You can find the steering pump attached to the car engine, usually right next to the car alternator and A/C compressor. We connect the steering pump to the engine through a belt-pulley mechanism using an engine belt. When your car’s engine is running, the engine belt turns in a loop and that also turns the steering pump. With that, the pump pulls the steering fluid from the steering fluid reservoir and pressurizes them. 103 | P a g e
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How exactly do they do that? Well, I don’t want to overwhelm you with all the tiny details, but if you are interested in knowing more, we have an article on the steering pump coming up very soon. For now, think of the steering pump as a black box. We put low pressure steering fluid in, and high-pressure steering fluid comes out of the other end. These high-pressure steering fluids then leaves the steering pump, through the steering hoses and into the steering rack, specifically into the rotary valve. Rotary Valve Inside the steering rack, we have what is known as the rotary valve. A rotary valve is a highly sensitive metal casing with strategically placed holes that redirects the steering fluid either back to the steering pump or into the steering rack. Think of it as the traffic police at a busy road intersection. It tells the steering fluid which way to go depending on where you turn your steering wheel. Here’s how it works If the steering wheel is in its original position, the rotary valve redirects the steering fluid back to the steering pump and nothing happens. The cycle of steering fluid moving from reservoir to pump and rotary valve just keeps repeating itself. But when the driver turns the steering wheel, the rotary valve opens up and steering fluid from the steering pump gets redirected. This time, it doesn’t go back to the steering pump but it exits the rotary valve through the fluid lines and into one of the hydraulic chambers of the steering rack. Hydraulic Chamber As the steering fluid from the rotary valve gets redirected into the hydraulic chamber, we start to get power assist! But let’s take a step back and see how it all happened. In the hydraulic chamber, there is a hydraulic piston right down the middle. It separates the hydraulic chamber into two equal portions: the left side, and the right side. The steering fluid gets redirected into these two chambers, but here’s the twist – they don’t get equal amounts of steering fluid! When there is more steering fluid on one side of the hydraulic chamber, it creates a pressure differential across the chamber. The steering fluid then pushes the hydraulic piston towards the weaker side of the hydraulic chamber and the steering rack moves accordingly. Now some of you may be wondering, why is there a pressure differential. Because of fluid dynamic. Or, more specifically the Bernoulli’s Equation. To give you a metaphor that helps you understand it, imagine two rooms of equal sizes with a movable wall that you can push in the middle. One room is filled with 50 people while the other is filled with 100 people. Because it’s so hot and stuffy in the room, I would push the wall so that I can get more space in my room. But hey, the other 104 | P a g e
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room want more space as well! Very quickly, this becomes a tug of war where the stronger team pushes the wall to the other side. Anyway, this “pushing of the wall” is what gives us the extra power. Since both ends of the steering rack is connected to the car wheels, when the steering rack move to the right, so will the car wheels. And… Voilà! The car changes direction and steering fluid flows back to the steering fluid reservoir to repeat the entire process again.
b) Electronic Power Steering
An Electronic Power Steering (EPS) system’s advantage over a hydraulic system is if the engine stalls, you will still have steering assist. This advantage can also be a disadvantage if the system should shut down while the engine is running you lose steering assist. A driver unaware of this condition would become concerned if an electrical or electronic failure occurred while the engine was running, as the loss of assist would not be expected. Electronic power steering systems eliminate the need for a pump, hoses and a drive belt connected to the engine using variable amounts of power. The configuration of an EPS system can allow the entire power assist system to be packaged on the rack and pinion steering gear or in the steering column. The system does not drag on the engine from either a power steering pump or alternator because it will not provide assist until required by driver input. Also, there is no hydraulic fluid. An EPS steering application uses a bidirectional brushless motor, sensors and electronic controller to provide steering assist. The motor will drive a gear that can 105 | P a g e
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be connected to the steering column shaft or the steering rack. Sensors located in the steering column measure two primary driver inputs — torque (steering effort) and steering wheel speed and position. The steering wheel is referred to as a hand wheel in the service information. The torque, speed and position inputs, vehicle speed signal, and other inputs are interpreted in the electronic control module. The controller processes the steering effort and hand wheel position through a series of algorithms for assist and return to produce the proper amount of polarity and current to the motor. Other inputs that will affect assist and return are vehicle speed, engine speed and chassis control systems such as ABS and electronic stability control (ESC).The brushless motor uses a permanent magnet rotor and three electromagnetic coils to propel the rotor. Most applications use a motor worm gear to drive the gear on the steering shaft or rack.
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c) Rear-Wheel Steering
At the rear axle is a steering system containing an electrical spindle drive and two track rods. They activate to turn the wheels a few degrees in the same or opposite direction relative to the front wheels, depending on the car’s speed. At low speeds, the rear wheels turn in the opposite direction to the front wheels. That reduces the car’s turning circle by about one meter, making the car more agile. The rear-wheel steering is most significantly felt when maneuverings the car through tight spaces like car parks or parking gantries. At higher speeds around 60km/h, the rear wheels follow the direction of the front wheels. Turning all the wheels in the same direction improves on the steering response and further increases stability in evasive maneuvers.
Steering Gearbox a) b) c) d) e) f)
Rack and Pinion Worm and roller Worm and sector Cam and Roller Reciprocating Ball Worm and Ball Bearing
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Explanation Rack and Pinion
A rack and pinion are commonly found in the steering mechanism of cars or other wheeled, steered vehicles. Rack and pinion provide less mechanical advantage than other mechanisms such as recirculating ball, but less backlash and greater feedback, or steering "feel". The mechanism may be power-assisted, usually by hydraulic or electrical means. The use of a variable rack (still using a normal pinion) was invented by Arthur Ernest Bishop in the 1970s, so as to improve vehicle response and steering "feel," especially at high speeds. He also created a low-cost press forging process to manufacture the racks, eliminating the need to machine the gear teeth.
Reciprocating Ball
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sector shaft (also called a sector gear) which moves the Pitman arm. The steering wheel connects to a shaft, which rotates the worm gear inside of the block. Instead of twisting further into the block, the worm gear is fixed so that when it rotates, it moves the block, which transmits the motion through the gear to the Pitman arm, causing the road wheels to turn. Bearing balls The worm gear is similar in design to a ball screw; the threads are filled with steel balls that recirculate through the gear and rack as it turns. The balls serve to reduce friction and wear in the gear, and reduce slop. Slop, when the gears come out of contact with each other, would be felt when changing the direction of the steering wheel, causing the wheel to feel loose.
16. Ergonomics
Ergonomics is the process of designing or arranging workplaces, products and systems so that they fit the people who use them. When it comes to car, it involves almost everything that is related to the passengers sitting inside the car. First thing that comes to our mind is seats. seating position, sitting posture, seat bolstering, under thigh support, lumbar support etc. are the few things which comes first to my mind when we talk about automobile ergonomics. 109 | P a g e
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Next comes the position and reach of the Pedals, Dials and Stalks. Pedals are very important part, for example, there are many people who enjoy laid back sitting position while driving. So, even when they push back the seat to enjoy their comfortable sitting position, ABC pedals should be within their reach. if they are not, driving experience will become cumbersome and tiring. this is where ergonomics comes into play. Similarly, for stalks and dials, it’s not just that they should be positioned where one expects them to be, they should be well within the reach of your hand. for example, I expect the volume control dial should be positioned just below the stereo system and its present there as well. But what if the dashboard is placed too far and its not in my reach or even if it's in my reach, dashboard is tilted towards the passenger rather than the driver. in both the cases, it’ll be extremely uncomfortable for me to use the dials. So, it’s the Ergonomics which deals with all these designs and makes our journey not only more comfortable and plusher but enhances security as well Prolonged periods of sitting can place heavy demands of our posture, particularly when sitting in a vehicle due to added effects of movement and vibration on the body. Being comfortable and well positioned in a vehicle aims to reduce driver fatigue and the development of musculoskeletal disorders. It is imperative that everyone using a vehicle for work observes adequate ergonomic requirements to minimize the risk of injury. a) Seat Height • • •
Raise the seat to ensure the driver has maximum vision of the road. Ensure there is adequate clearance From the roof.
b) Lower Limb Position • • •
Knees should be bent, in order to comfortably operate The accelerator/Clutch and break. The steering wheel should not come into contact with the top of the legs.
c) Seat Pan • •
Thighs supported along the length of the cushion. Avoid pressure behind the knees.
d) Back Rest • •
Adjust the backrest so it provides continued support along the length. Shoulders slightly behind the hips.
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e) Lumbar Support • •
The lumbar support whether adjustable or not, should provide comfort with no pressure points or gaps between the spine and car seat. A S-shape spine is a safe shape.
f) Steering Wheel • • • • • •
All objects and controls should be in easy reach to prevent unnecessary reaching. Elbows and shoulders should be in a relaxed position with hands positioned below shoulder level. Check for clearance Thighs and Knees (allow 2-4cm). Ensure display panel is in full view and not obstructed. A good test is to put your arms Straight in front (above the top of the steering wheel), the top of the wheel should sit at approximately wrist level.
g) Headrest •
The neck should be in a neutral position, with the head rest positioned centrally behind the head.
h) Mirrors •
Adjust the rear view and side mirrors to ensure adequate vision of surrounding areas.
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Common Risks and Ways to Minimize it
Musculoskeletal Disorders (MSD’s) • •
•
Driving a vehicle can be more detrimental than sitting or standing due to the effects of movement and vibration on the body. Common risk factors associated with the development of MSD’s include: prolonged sitting, fixed postures, inappropriate lumbar support and manual handling tasks when getting out of the car. Lower back, shoulder and neck pain are commonly associated with prolonged periods of driving.
Solution • • • •
During breaks (15 minutes every 2 hours) incorporate postural variation e.g. stretches, walking around car etc. Make small adjustments to driving posture every 30-60 minutes. Practice correct manual handling techniques when taking items in/out of the vehicle. If pain or discomfort persists, consult your treating health practitioner for further advice.
Fatigue • • • •
Fatigue is often ranked as the major factor in causing road accidents. Fatigue occurs from insufficient sleep and when drivers are required to sustain attention over long periods of time. Fatigue results in impaired attention, reaction speeds, vision, memory, impacting on driving ability. Fatigue can result in micro-sleeps, which are unintended periods of light sleep, either in the form of a lapse in concentration, blankly staring/day dreaming or even momentarily nodding off. Microsleeps can last between last a few seconds to a minute
Solution • • • • • •
Ensure you get 7-8-hour quality sleep the night before driving. Aim to not travel more than 8 hours per day. Take 15-minute break every 2 hours. Where possible, alternate driving with your colleagues or with nondriving tasks. Avoid driving whilst on medication that can cause drowsiness. Eat a well-balanced meal, avoiding fatty foods as they cause drowsiness. 112 | P a g e
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Heat can increase feelings of fatigue, therefore fresh cool air and music act as a short-term strategy in improving alertness. Music can act as short-term strategies in improving alertness.
Vibration • •
Vibrations from the mechanics of a moving vehicle can be transferred to your body through the seat and steering wheel. The operation of heavy machinery or heavy vehicles can cause higher levels of vibration.
Solution • • •
•
Vibration forces can be decreased with thick, firm foam car seats, which can absorb some vibration as it passes through. If possible, it is important to alternate driving tasks with non-driving tasks, to reduce the vibration exposure. Maintain a neutral spine; your spine is better able to observe shock when the lumbar curve is being maintained in a neutral position, compared to a flexed lumbar spine position sit up straight. Ensure tyre and suspension systems are maintained.
Sun Exposure • • •
Most side car windows can only block out approximately 37% of harmful UV rays. The most vulnerable areas whilst driving include the eyes, face, neck, arms and hands, particularly on the right side of your body. This results in more pigmentation and sun damage on the right-hand side of the body, increasing the risk of skin cancer.
Solution • • • •
It is optimal to have UV blocking/protective film on all windows to minimize exposure. Wear sun protective clothing such as a hat or long sleeves. Sunglasses are essential to prevent glare and reflection of UV rays. Sunscreen is SPF 30+, apply 20 mins before exposure and reapply every 2 hrs.
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17. Case Study : How to design an Electric bike Electric Bike Electric motorcycles and scooters are plug-in electric vehicles with two or three wheels. The electricity is stored on board in a rechargeable battery, which drives one or more electric motors. Electric scooters (as distinct from motorcycles) have a step-through frame.
Power Source Most electric motorcycles and scooters as of May 2019 are powered by rechargeable lithium ion batteries, though some early models used nickel-metal hydride batteries. Alternative types of batteries are available. Z Electric Vehicle has pioneered the use of a lead/sodium silicate battery (a variation on the classic lead acid battery was invented in 1859, still prevalent in automobiles) that compares favorably with lithium batteries in size, weight, and energy capacity, at considerably less cost. EGen says its lithium-iron phosphate batteries are up to two-thirds lighter than lead acid batteries and offer the best battery performance for electric vehicles. In 2017, the first vehicle in the US to use the new Lithium Titanium Oxide (LTO) battery non-flammable battery technology is a scooter called The Expresso. This new technology charges a battery in less than 10 minutes and withstands 25,000 charges (the equivalent of 70 years of daily charges).The technology, created by Altairnano, is currently being used in China where over 10,000 urban buses run on these fast charge batteries.
Charging All electric scooters and motorcycles provide for recharging by plugging into ordinary wall outlets, usually taking about eight hours to recharge (i.e. overnight). Some manufacturers have designed in, included, or offer as an accessory, the high-power CHAdeMO level 2 charger, which can charge the batteries up to 95% in an hour.
Battery swapping Manufacturers like Zero Motorcycles and recent entrants to the scooter market Gogoro and Unu have designed machines that allow quick battery swapping, for apartment dwellers who do not have a garage outlet, or for an instant recharge on the go.
Components of E - Bike The Electric bike consists of following components viz, DC motor, Frame, Platform, Battery, Drive etc. 114 | P a g e
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Dc motor: The motor is having 250 watts. Capacity with maximum 2100 rpm. Its specifications are as follows: • • • •
Current Rating: 7.5amp Voltage Rating: 48 Volts Cooling: Air – cooled Bearing: Single row ball
Frame: The Frame is made up of M.S. along with some additional light weight components. The frame is designed to sustain the weight of the person driving the unit, the weight of load to be conveyed and also to hold the accessories like motor. Also, it should be designed to bear and overcome the stresses which may arise able to due to different driving and braking torques and impact loading across the obstacles. It is drilled and tapped enough to hold the support plates. Platform: The Platform is designed with robust base so that it can hold the load along with the weight of the driving person uniformly. It is fabricated from Mild Steel at a specific angle in cross section and welded with a sheet of metal of specific thickness. The platform’s alignment is kept horizontal irrespective whether it is loaded or unloaded and this is directly bolted and welded to the frame. Battery: The battery also acts as a condenser in a way that it stores the electric energy produced by the generator due to electrochemical transformation and supply it on demand. Battery is also known as an accumulator of electric charge. This happens usually while starting the system. Chain Drive: A Chain is an array of links held together with each other with the help of steel pins. This type of arrangement makes a chain more enduring, long lasting and better way of transmitting rotary motion from one gear to another. The major advantage of chain drive over traditional gear is that, the chain drive can transmit rotary motion with the help of two gears and a chain over a distance whereas in traditional many gears must be arranged in a mesh in order to transmit motion. Braking System: For the braking system it is convenient to use braking system used in band brake system which consist of spring-loaded friction- shoe mechanism, which is driven with the help of hand lever. Sprockets: The chain with engaging with the sprocket converts rotational power into rotary power and vice versa. The sprocket which looks like a gear may differ in three aspects • Sprockets have many engaging teeth but gears have only one or two. • The teeth of a gear touch and slip against each other but there is basically no slippage in case of sprocket 115 | P a g e
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The shape of the teeth is different in gears and sprockets.
Design of E Bike Here we have used permanent magnet self-generating motor with 250-watt power and 2100rpm. The motor runs on 48volts and 7.5amps power source. This motor can reach a peak current during starting equal to 15 amps. P = 2 x 3.14 x N x T /60 250 = 2 x 3.14 x 2100 x T /60 T = 1.13 N m = 1136 N-mm Reduction in chain drive R chain = 66/11 = 6:1 Torque at wheel shaft = T x R chain = 1136 x 6 = 6820 N mm Speed of wheel shaft = 2100 /6 = 350 rpm
Designing of shaft Bending: The force which develops across a specific cross section of the shaft, it generates stress at that point of cross section that are subjected to maximum loading. This internal or resisting moment gives rise to the stress called as bending stresses. Torsion: When the shaft which is twisted by the couple such that the axis of the shaft and the axis of the couple harmonize, that shaft is subjected to pure torsion and the stresses generated at the point of cross section is torsion or shear stresses. Combined Bending and Torsion: In actual practice the shaft is subjected to a combination of the above two types of stresses i.e. bending and torsion. The bending stresses may occur due to any one of the following reasons: • • • •
Weight of belt Pull of belts Eccentric Mounting of shafts/gears Misalignment of shafts/gears
Shaft design T = 36000 N mm T = 3.14 / 16 x σs x d3 Fs allowable = 80 N/mm^2 6820 =3.14 x σs x d3/16 σs = 34.73 N/mm2 116 | P a g e
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Material = C 45 (mild steel) σut = 320 N/mm2 ------------ PSG design data book. factor of safety = 2 σ t = σb = σ ut/ fos = 320/2 = 160 N/mm^2 σs = 0.5 σt = 0.5 x 160 = 80 N/mm2 σs is less than allowable so our shaft design is safe.
Design of Sprocket and Chain for Electric Bike We know, TRANSMISSION RATIO = Z2 / Z1 = 66/11 = 6 For the above transmission ratio number of teeth on the pinion and the number of teeth sprocket is in the range of 21 to 10, so we have to select number of teeth on pinion sprocket as 11 teeth. So, Z1 = 11 teeth Selection of Pitch and Sprocket The pitch is decided on the basis of RPM of sprocket. RPM of pinion sprocket is variable in normal condition it is = 2100 rpm For this rpm value we select pitch of sprocket as 6.35mm from table. P = 6.35mm Calculation of minimum centre distance between sprocket THE TRANSMISSION RATIO = Z2 / Z1 = 66/11 = 6 which is less than 7 Dia. of small sprocket, Periphery = π × dia. Of sprocket 11 × 6.25 = π × D D = 11 × 6.25 / π D = 21.8 mm Dia. of sprocket, Periphery = π × dia. Of sprocket 66 × 6.25 = π × D D = 66 × 6.25/ π D = 131.3 mm So, from table, referred from PSG Design Data book The minimum centre distance between the two sprockets = C’ + (80 to 150 mm) Where C’ = Dc1 + Dc2 117 | P a g e
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----------2 C’= 131.3 + 21.8 ------------2 C’ = 76.5 mm MINIMUM CENTER DISTANCE = 76.5 + (30 to 150 mm) MINIMUM CENTER DISTANCE = 170 mm Calculations of values of constants K1 K2 K3 K4 K5 K6 Load factor K1 = 1.25 (Load with mild shock) Distance regulation factor K2 =1.25(Fixed center distance) Center distance of sprocket factor K3 =0.8 Factor for position of sprocket K4 = 1 Lubrication factor K5 = 1.5 (periodic) Rating factor K6 = 1.0 (single shift)
Calculation of Factor of Safety For pitch = 6.35 & speed of rotation of small sprocket = 2100 rpm Calculation of Allowable Bearing Stress: For pitch = 6.35 & speed of rotation of small sprocket = 2100 rpm Allowable Bearing stress in the system = 2.87 kg / cm^2 =2.87 * 981/100 =28 N /mm^2 Calculating Maximum Tension on Chain Maximum torque on shaft = Tmax= T2 = 6820 N-mm Where, T1= Tension in tight side T2= Tension in slack side O1, O2 = center distance between two shafts Sin ∝ = R1 - R2 --------O1O2 Sin ∝ = 65.65 - 10.9 ------------118 | P a g e
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170 Sin ∝ = 0.33 ∝ = 18.78
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TO FIND θ θ = (180 –2∝ ) X 3.14/180 θ = (180 –2*18.78) X 3.14/180 θ = 2.48 rad According to this relation, T1/T2 = e ^µθ T1/T2 = e ^0.35 x 2.48 T1 = 2.38T2 We have, T = (T1 – T2) X R 6820 = (2.38 T2 – T2) X 65.65 T2 = 75.27 N T1 = 2.38 X 75.27 T1 = 179.16 N So tension in tight side = 179.16 N We know, Stress = force / area x 2 Stress induced = 179.16/ (3.14 * 3^2 / 4) x 2 Stress induced = 12.67 N /mm^2 As induced stress is less than the allowable stress =28N /mm^2 design of sprocket is safe.
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Bibliography
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Notes
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