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controlling a servo motor to generate constant force


I have a machine which interacts with foot and I would like to control the motor so that it generates a constant load at the end effector (applied on the foot). I am able to read force and position information. What kind of control algorithm should I use to control a constant force generated by the servo motor? A force feedback controller which feeds back the force information to the controller and update the command signal seems to be ideal but my force sensors could be noisy and I don't know what filters and what cut off frequency I should choose. Can I assume a linear relationship between the currnet command to the motor and the amount of force generated at the output or it could be wrong due to the back emf, friction, etc...

I appreciate if you could advice.

I use compactRIO and labview fpga 8.6.



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I am not an electromechanical guy by any means so take this for what its worth. If you can read force then you should be able to set it using a PID control loop.
LabVIEW 2012

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It's been a while but did you ever get a comprehensive answer to this question? Also what servo motor are you using to drive to constant pressure/force?

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I think it can be done with a simple force sensor and a DC motor provided you have a means to control the voltage from Analog output.


The only problem you might encounter is it may oscilate around your force setpoint but you can find some simple ways to smooth that out.


It really depends (quite a bit) on what control precision your design is willing to tolerate.



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We will have fairly tight toerances as well as vibration issues that need to be filtered as well. The application is to drive a drill or saw at constant down force through a particular cut medium.

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