Marc van Doornik wrote: > > What it boils down to is this question: what is the quickest way to > remove this 1~1.2mm hysteresis/backlash without being limited to 200mm/s > **for the purpose of backlash removal ONLY**. > Why do you think you have 1 mm of hysteresis or backlash? Is that the pole pitch of the motor? It is totally irrelevant, as long as you consider this a closed-loop servo, not as a stepper. maybe that is where you are getting lost. > Fortunately, I think I've found the answer. Given the fact the motors > are directly commutated (and the field can move 'infinitely' fast) No, the field can not move infinitely fast, due to inductance. The drive has to apply a different voltage over some time for the field to change. > > Does this make sense or do I really need to get me some coffee now? ;-) Yes, definitely go for the coffee, in large doses. Then, you have to analyze the system as a control loop, putting in as much of the "plant" details as possible. Do the servo amps have a current (or torque) loop in them? If not, you have a real mess, I think. Having the amps match current output to the torque command in greatly helps the loop stability. Without this being built into the amps, it is REAL hard to patch it on the outside, especially in a multi-phase output.
My personal preference for this setup would be to derive a tach signal from the encoder, preferably at a fairly high rate, maybe 10 KHz or better, and try to implement the classic 3 nested loops (position, velocity and torque=current). If the amps don't have current feedback, then you may just be sunk. It may be impossible to give enough gain to satisfy the position error requirements and still have a stable system under all conditions. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
