Ona normal velocity PID loop, the command input and feedback are in position units, only the output command is in velocity units. For a torque command servo, if using a double nested loops the outer one would be a regular position/velocity loop, but the inner one would be velocity command input to torque command output. A single PID loop can be used with torque command servos, but tuning them is a lot harder and they are a bit unstable when loads change and at high or low speed. For such a loop tune with lots of I term with an i-error limit set so the I term can never saturate the output command. This allows a fast I reaction without windup induced overshoot causing instability.
On Thu, Jan 9, 2025, 9:08 AM Viesturs Lācis <viesturs.la...@gmail.com> wrote: > ceturtd., 2025. g. 9. janv., plkst. 13:26 — lietotājs Viesturs Lācis > (<viesturs.la...@gmail.com>) rakstīja: > > > > The thing I do not understand at all is how to approach PID tuning. At > > the moment I have set P=20 and all the rest to 0 and I get > > oscillations indicating that the value is too big, but the actual > > velocity is totally different from commanded. If I try to jog, motor > > does not slow down when button is released, I have to jog in opposite > > direction to reduce actual velocity, motor drifts until ferror limit > > is reached. > > Oh well this one was a marvelously stupid mistake of having position > on pid command and velocity on pid feedback, fixed that and now I can > jog the motor back and forth until I change pid parameters in > "Calibration" window. After that I get runaways. Ferror triggered, > motor stops. Hitting F2 will give immediate runaway. > And one more thing that seems strange is that motor makes noise at > standstill but motion is really quiet. Could these 2 things be related > to fact that it is the velocity on pid command and position loop is > not closed? > > Viesturs > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
