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    Robot Arm Calculator

    The Robot Arm Calculator is designed to help you determine the lifting capability of your robot arm. For example, can a robot arm of X length, with your motor, lift Y weight?

    It is a supplement to the robot arm tutorial. If you do not understand how to use this calculator, please read the tutorial first.

    Note that all entered values will be saved as a cookie on your computer (if you have cookies enabled) so you don't need to reenter anything on future visits.

    Note that you can also try out the excel version of the robot arm calculator. It includes an additional robot arm kinematics visualizer.

    Enter in values for your robot arm.

    Arm Lengths
    Between each motor joint is an arm linkage L. Enter the length of each linkage. If a linkage does not exist in your design, set L to zero.
    Select inches or meters

    Arm Weight
    Now enter the weight of each arm linkage. The center of mass is assumed to be 1/2 of L. If a linkage does not exist, set the weight to zero.
    Select pounds or kilograms
    W2 W4
    W6 W7 (object weight)

    Motor Weight
    Enter in the weight of each motor. Motor 1 is the base motor, Motor 2 is the middle joint, and Motor 3 is the wrist motor.
    Select pounds or kilograms
    Base Motor M1
    Joint Motor M2
    Wrist Motor M3

    Joint Rotational Acceleration
    note: For some reason the result when adding in acceleration looks astronomically high, but I can't figure out for the life of me where my equation mistake is. Just leave these at 0 if you don't trust the result. Sorry! Look at my source if you think you can figure it out . . .
    For each joint to rotate at a specific acceleration, you need to add additional torque to what you need just for static lifting. Fill in the acceleration you want for each joint.
    V0 degrees/s^2
    V1 degrees/s^2
    V2 degrees/s^2
    V3 degrees/s^2

    Motor Efficiencies
    Motors and gearing are never 100% efficient. Enter expected efficiency. If you are unsure about efficiency, check out my gearing efficiency tutorial.
    M1 % M2 % M3 %

    Torque Results
    These are the finished results. This is the maximum torque that each motor requires to lift both the arm and the given object weight at full extension at required velocity. Shorter arms and lower weights reduce required torque.
    Select Units
    Motor 0 Torque M0
    Motor 1 Torque M1
    Motor 2 Torque M2
    Motor 3 Torque M3

    Misc Results
    Useful information to help you with other parts of your robot design. For the encoder calculation, this will tell you the expected typical positioning error due to the base motor encoder. If you are using a servo for the base motor, enter 360. Shorter arms and higher resolutions decrease error.
    Total Weight
    Enter Base Motor Encoder Res. Ouput Arm Accuracy (inches)

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