Velocity control feedforward term

Questions about using encoders with the Roboclaw product line
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Joined: Wed Nov 14, 2018 2:06 pm

Velocity control feedforward term

Postby questioner » Wed Nov 14, 2018 2:29 pm

Is there a feedforward term in the velocity PID controller? Is it simply proportional to the commanded velocity? I want to control a motor driving a gravity-loaded joint. Adding a fixed positive or negative feedforward value to the PID output depending on the direction of desired motion will allow me to work with one set of PID gains for motion in both directions. But I don't see any way to add a feedforward term in the UI.

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Basicmicro Support
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Joined: Thu Feb 26, 2015 9:45 pm

Re: Velocity control feedforward term

Postby Basicmicro Support » Mon Nov 26, 2018 10:24 am

Yes, it is the QPPS value. The Roboclaw uses the QPPS value to determine the correct feedforward value automatically(you dont enter it other than setting the QPPS. QPPS is just the maximum speed of the motor in encoder counts per second. The simplest way to determine it is to run the motor at 100% duty and read out the speed.

Note that the autotuner will determine a reasonable QPPS setting automatically.

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