I search for a stepper-, servo- or other motor and a related circuit, which is suitable to handle the following aspects:

  • freewheeling:
    Spinning the motor shaft by hand without (or as little as possible) friction

  • variable friction at the motor shaft under computational control: Rotate the motor shaft by hand with a specific rotation behavior (rotation needs less force (smoothly rotation), or rotation needs more force (hardly rotation))

  • motor brake / lock: Rotate the motor shaft by hand is not possible, position locked

  • exert a specific and directed motor force: Rotate the motor shaft with a maximum of force so that a human can not hold the shaft

I would be very pleased if anyone can give me any advice. It would be perfect if the motor size is as small as possible.

Thanks in Advance :-)

  • \$\begingroup\$ Any modern didgital PMSM servo drive system can do that, and much more. \$\endgroup\$ Commented Sep 16, 2015 at 13:33
  • \$\begingroup\$ Can you provide me a simple motor model with an example, tutorial-link? I find no suitable PMSM servo with a controller and example. \$\endgroup\$ Commented Sep 17, 2015 at 10:09
  • 1
    \$\begingroup\$ Industrial servo systems: Omron servo motor/drive, Yaskawa Servopack, Siemens S120, Beckhoff AX5xxx, Emmerson, Samsung,...If you like more accademic you have evaluation boards from TI, ST, Microchip, Freescale...probably is better to buy a used industrial one, cheaper. freewheeling - disabling the servo, motorbrake - set target position to actual position, exert - positioning/speed/torque control, force - torque control, or speed setpoint = 0 with low Kp gain. \$\endgroup\$ Commented Sep 17, 2015 at 10:23

1 Answer 1


I believe that the performance that you describe requires a servo motor with a high resolution shaft position feedback to a high quality controller. In order to select a torque rating, you need to quantify "force so that a human can not hold the shaft" and also define the maximum speed for shaft rotation under motor power. A servo motor system can hold a shaft at a fixed position quite well, but not as solidly locked as a friction brake.

  • \$\begingroup\$ Is there a way to use a servo in a non-positioning way and define a friction? As I pointed out at the second requirement, I need to control the motor shaft also manual by hand with different haptic feedback. And in my understanding servo motors are controlled by absolute positions. Can you provide me a simple example, tutorial-link or motor type on how to do that? Thank you so much :-) \$\endgroup\$ Commented Sep 17, 2015 at 9:24
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    \$\begingroup\$ I believe that a servo controller could be set up to hold the speed of the motor shaft at zero, but develop only a set torque to do that. That set torque could be adjustable from zero to the maximum capability of the motor. I can not provide any links. I suggest that you look for the web sites of the brands mentioned by Marko Buršič and download product literature and manuals. There is likely general tutorial information available, but I don't have any links to offer. \$\endgroup\$
    – user80875
    Commented Sep 17, 2015 at 15:24

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