# How to find the maximum torque to apply to a robot joint to have realistic movement? [closed]

I am a computer science student. I am trying to simulate a locomotion of a legged robot.

The weight and dimensions of the robot:

• A rectangular torso has 1 Kg, (0.15m*0.3m*0.03m) (width * length * height)
• Four cylinder legs, each one is about 0.2 Kg (0.04m length, 0.01m radius)

Moment of inertia of each leg: (computed them from wiki page )

• Ix =Iy = 0.000126667
• Iz = 0.00001

My question is, how to know what is the maximum of torque and angular velocity to get the joint rotate in a realistic way. Here is a video of what I mean by not realistic.

I know that in a linear movement: Force = Mass * Acceleration. So we can find approximately the force. But in a joint ?

Sorry for the question, it may be stupid but I didn't studied physic since high school!

## closed as off-topic by ACuriousMind♦, Kyle Kanos, rob♦, Qmechanic♦May 12 '15 at 21:39

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• "This question appears to be about engineering, which is the application of scientific knowledge to construct a solution to solve a specific problem. As such, it is off topic for this site, which deals with the science, whether theoretical or experimental, of how the natural world works. For more information, see this meta post." – ACuriousMind, Kyle Kanos, rob, Qmechanic
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• Would be Engineering SE or Robotics SE a better home for your question? – Gonenc Mogol May 11 '15 at 10:01
• "to get the joint rotate in a realistic way" - that's not a well-defined question. You should try and be more specific of what your criteria is. If you can't then trial and error is the way forward. – lemon May 11 '15 at 10:28
• Since you know about moments of inertia, you should know the equations of motion of rotating system. You simply have to apply them. Where this gets complicated is if you have multiple degrees of freedom and non-trivial constraints. Now you are deep into Lagrange/Hamilton territory, and if you have to deal with more general forces than conservative ones (of course you do!) even that's not enough. – CuriousOne May 11 '15 at 11:23
• So I have to take a look at the equations of motion of rotating...what do you mean by general forces, thank you – user1931907 May 11 '15 at 20:24
• I also suggest you have a look at some biomechanics textbook. Torque exerted on the leg of human varies with the angle in a non-trivial manner. – Azad May 15 '15 at 8:27