Target position error

[varmih]

Hello,

I have some problem using an analog feedback PID to control a servo axis, both in MAX and in LabVIEW environment, on 7344 controller. The actual steady state axis position is at least 15-20% less than the target position. I have changed PID control loop parameters, but 15-20% difference is the best result. Do you have any idea how can this problem be resolved?

Thanks.

[varmih]

Attached you can find a typical example of the system step response

[Jochen]

This looks like Ki = 0. Could you please provide your PID parameters?

Thanks,

Jochen Klier
National Instruments Germany

[PGriese]

For a tutorial about PID contol have a look to:
Classical PID Control
http://zone.ni.com/devzone/conceptd.nsf/webmain/F0A8687D6706719686256D6D005F9C56 

Message Edited by Peter Schlosser on 03-31-2005 09:05 AM

[Jochen]

Please also have a look at this link. Here you find a less theoretical explanation of PID tuning based on the tuning features provided by MAX.

Best regards,

Jochen Klier
National Instruments Germany

[varmih]

Thank you very much for the exact answer, Jochen. The problem was in the absense of Ki and now the system can really achieve the target position.