This tutorial is intended to complement the Robot Arm Torque Calculator found in the Dynamic Tools section of GoRobotics. The equations used in the calculator to determine the torque required at any given lifting joint (raising the arm vertically) in a robotic arm are presented h…

@Jdiknight Welcome to the RobotShop Community. By “3DoF”, do you mean an articulated arm with shoulder / elbow and wrist, or a “3DoF” like: https://www.robotshop.com/en/lynxmotion-lss-3-dof-robotic-arm-kit.html Regarding moment of inertia, you’d need it for each actuator and fo…

@cbenson by 3dof i mean like the example you gave here Lynxmotion (LSS) - 3 DoF Robotic Arm (Kit)

It would be interesting if you could treat each link as “massless” to save a ton of calculations (and only take into account the “heavier motors” like the ones in the wrist, as well as the payload (which is now only moving in 2D). On the plus side, the inertia calculations are a …

Hello @cbenson I am struggling with calculating the the required torque for my robot arm (I tried to follow the tutorial but I am confused at how to apply it to my robot arm). This is a diagram of my arm below: [image] How would I calculate the torque due to gravity, would I a…

@pk2902 Welcome to the RobotShop Community. “Counter-torque” needed to keep the arm horizontal against gravity would be: 0.535Kg x 45cm (assuming the mass is centered) = 24.075 Kg-cm 0.81Kg x 50.5cm (90-22-35/2) = 40.905 Kg-cm 0.55Kg x 79cm (90-22/2) = 43.45 Kg-cm 0.5Kg x 90cm…

Moving 45 degrees in one second doesn’t actually directly give you acceleration (radians per second per second) but rather the average angular speed. The harder part tends to be calculating the total inertia of the system.

Thank you, Total Inertia=Motor Inertia + Link Inertia, if i’m correct Does that mean I will already need to have motors selected? And then do the calculations

Effectively the inertia of each of the masses (and the support rod). Assuming the motor is not rotating at high speed (and it’s not a flywheel), its effect on the inertia is likely to be minimal so it’s up to you if you want to estimate it and include it. Remember, even with all …

So would I use this equation I=(m*r^2)/2 for each of the masses and add them together? (I’ve also seen some other equations for inertia online) I’m gonna be adding around 20% to my final calculations as the safety margin. I’m really appreciating your help!

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Robot Arm Torque Tutorial

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pk2902 February 15, 2022, 4:09pm 89

Thank you for replying!! Very helpful

Yes the 0.5kg is the payload.

Great, i’m gonna try to calculate the torque due to angular acceleration and then add it to the torque due to gravity?

I’m guessing I will need to specify in how many seconds I would like the link to move up or down. (E.g. 45 degrees in 1 second).