Pitstop june 2014 by IIT Bombay Racing

FS 2014 edition Year at a glance

Co 01 ..........

Research at IITB

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Improvements in EVo 3.0

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Sponsorsâ&#x20AC;&#x2122; Feedback

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Design Launch Report

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Our Sponsors

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The IITB Racing Family

ontents S

on iti er ed add L 14 the 20 Up ng

F ci Ra

A Research AT

IITB

Racing

number of performance and safety related aspects of motor sports have received attention in recent years. With the advent of electric race cars in Formula Student, safety has become even more important. Two critical areas that we identified were aerodynamics for performance improvement and accumulator system for safety aspects. Because of the limited timeframe we have for the competition and given the complexities involved in these aspects of race car design, we have put them into research category. We have involved faculties and masters student to guide and help us in these research projects with the long term objective of implementing the results in future cars of the team.

Aerodynamics

The use of aerodynamic devices is quickly becoming a necessity in Formula Student. So in order to understand its effectiveness, we started working on aerodynamics. For this season the objective of aerodynamics subsystem was drag reduction by streamlining the bodyworks, thereby improving the fuel economy. With no prior knowledge and experience in aerodynamics and CFD, our initial focus was on development of technical expertise in this field.

Various design iterations were done with increasing level of complexities to ultimately perform full car CFD. A substantial reduction in drag force of 18.8% is achieved which can be attributed to lower frontal area and streamlined bodyworks design. Energy consumption of the vehicle for endurance race is reduced by 11.5 % improving the fuel economy.

Using the CFD expertise that we gained, design and development of complete aero package has been started. Wind tunnel validation of drag study will be done in aerospace engineering department on scaled down models. Complete aero package will also be validated by wind tunnel testing.

Thermal aspects of accumulator

The development of safe, high voltage batteries is regarded as a major challenge in electric car design. The safety issue concerns the thermal aspects of battery pack. A Li-ion cell generates heat during both charge and discharge, and the heat generation in the battery can increase sharply leading to temperature rise above safety limit. It also affects the performance and life of the cells. In this research project we focused on the thermal characteristics of battery pack i.e. the temperature profile across the pack as the car runs during endurance.

Other thermal properties like specific heat capacity of the pack and conductivities were evaluated by experiments. For this season it was ensured that the temperature does not rise above the safety limit. Other data collected and estimated will help the future teams in designing the cooling system for the battery pack if required. More advanced thermal models and experiments to validate them are being developed by the team.

Two papers on these projects titled as “Parametric study of drag force on formula student electric race car using CFD” and “Thermal characterization of lithium polymer battery module for electric vehicle application” were submitted to 2nd International Conference on Mechanical, Automotive and Materials Engineering (CMAME 2014). Both of them have been accepted for presentation during the conference.

PITSTOP- June 2014

3 1

5 4

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Overall Improve

Improvements

Evo 3.0

• Weight Reduction: Subsystem

Chassis and Bodyworks Vehicle Dynamics Powerdrain Electronics Battery Overall

• Tunability:

Wireless tuning of e achieve better tunability. • Reliability: Reliability has been gi cation, validation and testing

Chassis and body

• Weight and overall height r

was reduced by 16% majorly by narro

roll hoop height. The reduction of h

driver seat angle to 40 degree witho

• Custom Impact Attenuator:

Custom IA was designed, fabricate

for the first time using Rohacell hig

density foam and tested at the Auto

motive Research Association of India

â&#x20AC;˘ Aerodynamics:

ements

For the first time, an aerodynamics subsystem

was established to focus on streamlining of bodyworks for better fuel Evo 2.0

Evo 3.0

67 kg

62 kg

95 kg

64 kg

73 kg

58 kg

12 kg

11 kg

90 kg

55 kg

340 kg

250 kg

economy. By doing CFD simulations and iterative bodyworks design significant reduction of 18.8% is achieved in drag force acting on the car.

e-differential parameters helps us

iven key focus during design, fabri-

yworks

reduction: The weight of chassis

owing the cockpit and reducing the

height was achieved by tilting the

out compromise of driver vision

Powertrain â&#x20AC;˘ E-Differential: EVo 2.0 e-differential implemented a slip control strategy wusing wheel RPM feedback. EVo 3.0 implements torque vectoring using yaw rate control helping us achieve better driver comfort and improved handling by avoiding over or under steer.

PITSTOP- June 2014

â&#x20AC;˘ Drivetrain:

Improvements

Evo 3.0

EVo 3.0 houses an

innovative planetary gearbox weighing merely 9 kg, in comparison to EVo 2.0â&#x20AC;&#x2122;s two-step gearbox weighing 16 kg.

Battery and safe Improvements

Integration

Robust safety system

Easy Debugging of safety system

Battery casing

Electronics and harness • Wire Harness:

This year’s motto is to keep wires less interconnected to each other and use separate connectors for bunch of different types of signals. For ease in connections between PCBs and connectors, PCB mounted connectors are used. Also for more reliability and compactness, we are keeping all the PCBs in just one enclosure

• Data Acquisition:

This year our objective is to make the DAQ system wireless to avoid plugging the USB cable for exchange of data. Our DAQ system processes and logs all the data onto a fast and powerful central computer, BeagleBone Black, not missing a single bit of crucial data and sending this data for laptop to observe. The data from sensors will be sent to laptop using the long range XBee module while the Car is running so that it can be analysed in real time.

Vehicle Dynamics

• Custom Vehicle Dynamics model:

A MATLAB model was developed that incorporated tire data, roll calculations and steering geometry, helping us simultaneously design a suspension and steering system that maximized the overall vehicle performance.

• Weight Reduction:

ety

Suspension and wheel Assembly Rocker, Spring, ARB Steering Assembly Brake Assembly Overall

Evo 2.0 All the components inside battery were mainly integrated using cables and connectors

67.85 kg 6.76 kg 4.43 kg 19.93 kg 98.97 kg

44.09 kg 3.80 kg 2.62 kg 13.65 kg 64.16 kg

Evo 3.0 The electronic components are mainly placed on the printed circuit board which interconnects them.

Filters were introduced later which result- The board was designed to be noise ed in bad integration of the boards tolerant by adding filters and appropriate pull up/pull down resistor LEDs were incorporated for identification A micro-controller monitors important of faults. Internal signals needed to be signals on board. On failure it communidebugged using a multimeter cates with DASH and displays the failure. Aluminium battery box weighing 3.5kg Carbon fibre box weighing only 1.5kg

PITSTOP- June 2014

r o s n o Sp

b d e e F

rs’

back

PITSTOP- June 2014

Design Launch

Report

This year, IIT Bombay Racing decided to have separate launch for the design prior to the car launch. The Design Launch of Evo3.0 was held during the third day of the Techfest 2014, technical festival of IIT Bombay. Designs from both, mechanical and electrical subsystems were revealed during the event, which was attended by Prof. Urjit Yagnik, Dean (Student Affairs) of the institute and officials from sponsors companies like NRB Bearing, Imaginarium and Mathworks* . Members of other college’s racing team were also present. The launch event was hosted by the team captain, Siddhesh Sakhalkar. During the launch, heads of each subsystems presented their designs. Imaginarium gifted a small-scaled version of the Evo3.0 manufactured through 3D printing, which boosted the team’s enthusiasm. After the presentation, 2nd edition of PITSTOP “Design Launch Edition” was launched. The event ended by a concluding speech from Akshay Goyal (Head, Organisation Team) thanking all the students, Dean(SA) and dignitaries from the sponsor companies. Besides the Design Launch event, IIT Bombay Racing also showcased the last year’s car Evo2.0 during the 3-days exhibitions at Techfest 2014. At the exhibitions, posters of each subsystem’s design for Evo3.0 were displayed.

PITSTOP- June 2014

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