Electronic – servo selection for robotic arm

roboticsservostepper motortorque

Hi i´m designing a robotic arm based on this idea of the NOVABOT I only want to change its structural parts by aluminum tubes. In this design 3D model it use the servo hs-311 wish have a max torque of 3.7 kg/cm, and its made of some plastic material.

I made my calculations following this url and made a excel that I append here… the mass of my design have been taken from iProperties of Autodesk Inventor, so they are in mass units not in weight. And I´m dismissing the mass of the joints (m5,m6) to have a first idea of the values, because I dont have the selected motors.

And my problems is that I think I´m missing something here because the it results in a very high torque motors, for this simple design.
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here is my excel

Best Answer

Your torque result is in the right ballpark. The joint actuators for arms like this usually have significant reduction through planetary gear boxes, harmonic reducers, etc which multiplies the torque of the motors by the reduction ratio (minus mechanical losses)-

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