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NERC ROBOT

Apr 14, 2018

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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 s

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