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Classes • Innovative Mechanisms and its implementation. • Autonomous robotics – Basics and Advanced. • Programming in C for Autonomous robotics.
Hands – On • Sensor circuits and motor driver. • Line follower/Object detection/Light follower. • Microcontrollers.
MATERIALS REQUIRED
•Wire Stripper •63-37 Solder •Pencil tip soldering iron •Desoldering wick •Multimeter •Basic Bread board •Single strand wires •Tweezers •Screw driver set •Heat shrink tube(10mm/5mm/2mm/1mm) •Matchbox •Glue-fevikwik •Insulation Tape
GEARED SYSTEMS • Gears are the most common form of torque increment devices, found in almost all mechanical machines. • The concept of reducing the rotation speed to increase torque is known as ‘Gear Reduction’. • A high speed motor with low torque is used to drive heavier loads at lower speeds. • They have much more efficiency than pulleys • The maximum torque capability is not limited by friction but material strength.
USES OF GEAR SYSTEMS
Reduction’ to increase torque / decrease speed of rotation. • Alter the direction of rotation axis. • Synchronization to two axes. • Reversal of direction of rotation. •
‘Gear
TYPES OF GEARS
• • • • •
Spur Gears Helical Gears Bevel Gears Worm Gears Rack and Pinion Gears
SPUR GEARS • Very common kind of Gear. • Used primarily for gear reduction. • Reduction ratio is the ratio of teeth in the driver gear and the driven gear.
WORM WHEEL MECHANISM • Used for very high gear reduction • The wheel is driven by the worm screw. • One rotation of the worm causes the wheel to advance one tooth
RACK & PINION MECHANISM Used for converting rotational motion into linear motion
GEARS THEORY • Velocity of contact point and power transferred from one gear to other remains constant. • V=r . w, Power=Torque x w • Consider r1 and r2. r1w1=r2w2 and T1 x w1=T2 x w2. • The gear with larger radius will have lower w and larger torque.
GRIPPING MECHANISMS
RACK AND PINION • A rack and pinion is a type of linear actuator that comprises a pair of gears which convert rotational motion into linear motion. • The circular pinion engages teeth on a linear "gear" bar. • The rack. Rotational motion applied to the pinion will cause the rack to move to the side, up to the limit of its travel.
GRIPPING MECHANISMS
• The most important thing that is to be taken care of in order to properly stack objects, is the gripper. For this type of gripper we can have one part of the gripper as stationary and actuate the other.
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SOME GRIPPING MECHANISM
GEARS • Another option with the grippers can be to move both the parts simultaneously using gears or wires and spool.. • The picture below shows how to accomplish this mechanism using gears. • When motor moves the driving gear the driven gear automatically moves in the opposite sense due to the meshing. • This is used to move the gripping pads closer or farther from one another.
Walking Mechanisms •
Most living creatures on this planet use limbs as a mode of locomotion. So it must probably be the most easiest way of locomotion. But then why do we go on using wheels? • It turns out that making a walking robot is far more difficult than making a wheeled or tracked one. Even the most basic walker requires more actuators. • More degrees of freedom i.e. more moving parts.
BASICS OF A WALKER There are basically three ways in which to move a robotic limb: 1. Linear actuators(hydraulic, pneumatic, electrical etc) 2. Rotary actuators 3. Cable driven
LINEAR ACTUATORS
http://www.youtube.com/watch?v=ue wMphsBamk
ROTARY ACTUATORS • These are the most elegant sort of actuators as they are the simplest to use. • The only problem with these is that they make the joints of the limb very bulky as they have to be directly attached at the limb for best performance. • Some of the most commonly used of these actuators are servo motors and stepper motors. A normal DC motor of low rpm can also be used to this extend.
ROTARY ACTUATORS SERVO MOTORS
http://www.youtube.com/watch?v=RCgOCfaWShc
Now imagine implementing these methods of actuation into a structure like the one shown below.
RELAYS • A relay is an electrically operated switch. • Relays use an electromagnet to operate a switching mechanism mechanically.
BASIC DESIGN AND OPERATION
• Each relay has two mechanical parts inside. • The first one is the contact(s) of the relay. The contacts operates similarly to the contacts of a simple switch or pushbutton. • You should consider the contacts as a pair of metals like the following diagram.
BASIC DESIGN AND OPERATION • The two terminals operates as a switch. When the contacts are 'in contact' then the current flows from Terminal 1 to Terminal 2. There are two types of contacts: the NO and the NC. • NO stands for Normal Open contact, while NC stands for Normal Closed contact. The Normal Open is a contact like the one showed in the previous illustration. • When the contact is still, then no current flows through it (because it is an OPEN circuit). On the other hand, a Normal Closed contact allows the current to flow when the contact is still. Below is illustrate both of these contacts:
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BASIC DESIGN AND OPERATION • A relay may have a combination of the above contacts. Look at the following illustration:
• In this case, there is a 3rd terminal called "COMMON". The NO and NC contacts are referred to the COMMON terminal. Between the NC and the NO contact, there is no contact at any time! The following animation shows how this pair operates:
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BASIC DESIGN AND OPERATION • This is the last part of the relay operation. • The device that forces the terminal to move, is actually an electromagnet! A coil is placed right under the contact. • When current is flown through this coil, a magnetism is created. • This magnetism can overcome the force of the spring and can pull the contact towards it, thus it changes it's position!
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