nerc robot presentation.pdf

7/27/2019 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.

Generated by Foxit PDF Creator Foxit Softwarehttp://www.foxitsoftware.com For evaluation only.


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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 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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