NERC ROBOT PRESENTATION.pdf
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Transcript of NERC ROBOT PRESENTATION.pdf
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SYLAR1st Runner Up
(NERC-09)
Robot Design Strategy
Sit down in your groups and start discussing.
Make a plan:
What do you want to do?
How do you want to do? How much budget do you have?
How much time do you have?
Listen to everyone in the group.
Discuss your ideas and seek help fromfriends andpeople in your social circle.
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Robot Design Strategy
Go through the score distribution scheme and chooseone with the highest score.
Select a path which involves minimumtime tocomplete the task.
Finalize above two points before you start designingyour robot
Path Strategy
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Starting Mechanical Design Main parts of your robot will be:
Peg placement mechanism
Peg loading mechanism
Base (including wheels and drives)
Think on each part step by step.
Go fromthe top to the base of the robot.
Visualize every design that comes up in your mind.
Make sketches of all the main parts of the robot. Stick to the most robust and reliable design.
Do not indulge yourself in a very complicated design.
Finalize model of your robot on any designing software
SYLAR
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Material Selection Aluminiumis light in weight & relatively strong.
Acrylic can also be used in some parts:
Flexible
Light Weight
Easily available
Use Hard Nylon for small parts which are not
bearing too much load Main drive shafts should be preferably of steel.
Dont go for stainless steel as it is heavier then steel
Mechanical Design
The Peg Placement & Loading Mechanism:
Go for the one giving you max. tolerance in placement.
Try to minimize the placement time by extending the arm
out of the base. The mechanisms should be rigid and firmly supported.
Keep mechanisms as simple as possible.
Discuss your purpose and ideas with your machinist.
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Peg Placing Strategy
Peg Placing Mechanism
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Peg Placing Mechanism
Peg Placing Mechanism
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Peg Placing Mechanism
Peg Loading Mechanism
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Peg Loading Mechanism
Peg Loading Mechanism
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Mechanical Design Robots Base:
Base should be strong enough to carry the load.n Aluminiumbeams are suitable in most cases
The lower the base, the stable it is.
Prefer nuts & bolts on welding.
Always use spring washers with the nuts.
Ask your Machinist for the suitable bolt sizes.
Minimize the material to minimize the weight. Try for a frame rather than a completely filled platform.
Always use bearings to couple the shaft with the base.
Keep in mind overall dimensions of the Robot.
Bottom View of Base
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Mechanical Design Robots Wheels:
Your robot can have:nTwo powered wheels with a roller
nTwo powered wheels with two rollers
n Four powered wheels (coupled with belts, chains etc.)
Minimize the distance between tires on same side for preciseturning.(for four powered wheels only)
Ready made wheels are available in market.n Bigger the wheels, Higher the required torque , More the speedn Bigger the wheels, More the ground clearance
n Select the dia. which best fulfills your requirement
For custommade nylon wheels, use O rings to avoid slippage.n Do not use very thick rings.
Old Base
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Base Drive
Mechanical Design
Selecting a Motor: Go for simple PMDC motors with matched RPM. Always use a gear ration 48V PITMAN motors with their gear box will be an ideal
selection. Check your motor s torques on the turns Test motors with 100% PWM to check difference
between their RPM.nMinimumthe diff, stable the drive
Use servos for precise operation of the mechanisms Complete and test your base along with the drives
before the time limit.
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Old Motor
Pitman 48V
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Robot Design Flexibility
Keep in mind the time constraints.
Always leave allowance in your measurements.
Always keep space for modification in your design.
Test your design practically before time limit.
Arm Adjustment
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Sensors & Mountings Types of Sensors generally used:
IR Sensors Photo Transistors LDR (Light Dependant Resistors)
n Photo Transistors have best response & are handled easily
Mount your sensors in proper housings(prefer internally blackenedhousings)
Keep your sensors covered to filter undesired lights. Keep sensors mountings adjustable in two DOF.
Up-Down Left Right
Max. Distance between front sensors and Pivot Point.
IR Reflection Sensor (Focused and Daylight Filtered)..
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Photo Transistors
Front Sensors Mounting
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Peg handling
Dont depend on clock for Peg Handling.
Place pegs in a closed loop.
Load pegs while moving fromone stand to the other.
Use IR sensors, Limit switches as feedback sensors.
Minimize the chances of pegs getting stuck in the
mechanism.
Peg Handling
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ELECTRONICSBasically electronics of an autonomous machinecomprises following circuitry
Power Distribution Card
Motors and Actuators Drive Cards
Sensors and signal conditioning Cards
Control Card
ELECTRONICS
In SYLAR, we used a modular approach; it hadthree major boards:
Control and Power distribution board Sensors and their distributor board
Motor drives
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CONTROL & POWER DISTRIBUTION
BOARD
Traditionally both are kept separate but in Sylar,we combined themon one.
Advantage:
Reduced the clutter of multiple boards.
Simplified wiring.
CONTROL & POWER DISTRIBUTIONBOARD
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CONTROL & POWER DISTRIBUTION
BOARD
Sensors Junction Board
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MOTOR DRIVES A real critical decision to take
Reliable and Efficient Motor Drives
Relay-Mosfetbased vs. Conventional H-bridge
Response time
Acceleration and Deceleration
Protection against Surge Currents
Fuse Protected
MOTOR DRIVES
Sylar initially used motor drive IC; LMD 18201.
Shortcomings:
n IC kept on short circuiting due to design fault.
Relay-Mosfet based Motor Drives were used latteron.
Shortcomings:
nThis motor drive did not provide perfect sq wave requiredfor PWM control.
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Wiring Strategy & Noise Reduction We managed to get rid of heavy wiring
Simplify wiring by designing modules
Implementing hardware in software;ADCs vs. Comparators
Combining Power Board and Control Board
We managed to minimize electronics noise
Good PCB-designs
Use of Ground Planes
Use of Capacitors with Voltage Regulators
Use of 0.1uF Capacitors with sensor signal lines
Preferably use In-circuit Programming
Controller Selection
Major Criterian
Sensors Interfacing
nADCs
nOther interfaces
Actuators and Motors interfacing
n PWM requirement
nOther techniques
Processing Speed
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Programming Strategy Start with planned initial settings
Efficient & reliable Low-level Programming
Use of functions
Use of Multiple Files
Makes work a lot easier
Use of LCD or a COM link
Helpful in debugging
Multiple Files; Easier Programming
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