Stepper motor PID control

[[email protected]]

Sorry.. I've forgotten this question in previous message: It's
possible to control a stepper motor in a closed loop system via a
common PID algorithm ? I ask this to you because many commercial
controllers that I've found have encoder input but use it only for
stall detection. I think a continuous controlling of stepper motor
isn't a great idea due to discreet nature and relative low resulution
of stepper motors: I think that is sufficient an accidental little
movement of mechanical system respect to idle position to cause
continuous vibrations: is it correct ? My idea is to use PID only
during motion commands and stop it when axis is settled in a given
range: it will limits axis overshoot and precise positioning without
undesidered steady vibrations.
What do you think about.

Best regards.
Simone Navari.

 

[BobG]

Pretend its a DC sin/cos torquer and drive it with a variable
frequency sin/cos drive?

 

[whit3rd]

Sorry.. I've forgotten this question in previous message: It's
possible to control a stepper motor in a closed loop system via a
common PID algorithm ?

Yes, in a way. You can make an error signal with PID techniques, feed
it to a VFC (voltage-frequency converter-I like CD4046 for this
application)
and use pulses from the VFC to clock your stepper drive. Two VFCs and/
or
a bit of logic can make it work in reverse as well as forward.

The discontinuity at a step will, however, drive the 'D' term of your
PID
somewhat crazy. PID control is better suited to DC servomotors.