What kind of motor should i choose?

Thread Starter


Joined Feb 26, 2019
I am working on a project at home where i would like to build an elbow exoskeleton (like the picture i atteched). The load on the motor would be a forearm, the aluminium structure on the forearm and little or no load in the hand. So the torque on the motor would be max 20 Nm. The motor should have to be able to rotate at the speed it could follow the used arm (and a bit faster). The rotation can be just 180°, because the motor just has to follow the movement of the forearm. The complete structure should have to be portable, so i wouldn't like to power the motor from huge power sources. Also it would be better if i wouldn't have to pay a lot for it. If required i would measure the rotation with a potentiometer.

So what kind of motor would you recommend for this project?



Joined Feb 22, 2014
Hi Temeraire, to get the sort of high torque you need in a small package you will really need to look for some sort of gearing. A worm gear configuration would be the most compact, but the problem is then that you cannot force the gearing to move by moving the arm.
Some thing like this:
A stepper motor lets you position the motor accurately, but they are more expensive than DC motors. So if you are happy getting the position with a pot. as you say, I would go for the DC option. You can also get some feedback for how much resistance there is to the motion by monitoring the current needed on a DC motor.