[andy55]

Hi Group,

I'm building an AC servodrive which now sort of works, commutation seems to work nicely, and open-loop speed control works.

I'm going to be controlling the servos with EMC using a 5I20 servocard, so the encoder signals will be hooked up to the 5i20 and EMC will respond by outputting a speed command through the 5i20.

My question is, what improvements/benefits, if any, are there in improving the software in the servodrive so that it includes a PID loop for maintaining speed and possibly inside this loop a PID loop for phase current (torque).

These speed/torque loops could run at around 10-20kHz in the servodrive microcontroller which is pretty close to the 1-10 kHz position PID loop update rate in EMC.

I imagine this question is similar to a situation with DC servos where one drive would only get a speed command from the controller and controller would get encoder counts from motor.
The other, with speed-loop closed in servodrive, would have the servodrive read a tacho and maintain constant speed.
Anyone have experience with differences between these kind of setups ?

If anyone has any views on this I'd be glad to hear about them.

[NC Cams]

Try this:

PID tuning
http://www.cnczone.com/forums/showthread.php?t=20927