k.r.a.i.g. 104
DESCRIPTION
Gears, Grippers, Walking Mechanisms, RelaysTRANSCRIPT
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W W W . R O B O T I X . I N
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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.
WELCOME TO KRAIG
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•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
MATERIALS REQUIRED
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• 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.
GEARED SYSTEMS
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• ‘Gear Reduction’ to increase torque / decrease speed of
rotation.
• Alter the direction of rotation axis.
• Synchronization to two axes.
• Reversal of direction of rotation.
USES OF GEAR SYSTEMS
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• Spur Gears
• Helical Gears
• Bevel Gears
• Worm Gears
• Rack and Pinion Gears
TYPES OF GEARS
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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.
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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
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RACK & PINION MECHANISM
Used for converting
rotational motion into
linear motion
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• 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.
GEARS THEORY
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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
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• 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.
GRIPPING MECHANISMS
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DEMO
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SOME GRIPPING MECHANISM
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• 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.
GEARS
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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.
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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
BASICS OF A WALKER
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LINEAR ACTUATORS
http://www.youtube.com/watch?v=ue
wMphsBamk
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• 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
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ROTARY ACTUATORS -
SERVO MOTORS
http://www.youtube.com/watch?v=RCgOCfaWShc
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Now imagine implementing these methods of actuation
into a structure like the one shown below.
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• A relay is an electrically operated switch.
• Relays use an electromagnet to operate a switching mechanism
mechanically.
RELAYS
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• 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
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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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DEMO
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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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DEMO
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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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DEMO