can we cascade PID and PIV loops to control the servo motor

[sidda]

hi

presently we are using PID loop for controlling the motion of a servo motor using ni-7352 card. We  are not able to receive the desired response from this implemenatation. So is there any other alternative like using a PIV loop or using PID cascaded with PIV to achieve a better response. If there is possibility help us to proceed further with this.
 also tell us which is more reliable 1)using PID alone  2) Using PIV Alone 3) using PIV and PID cascaded.

please mail to this query to info@jisnu.com

[Jochen]

Sidda,

before you start thinking about advanced control architectures I want to ask you to tell me some details about your system behavior and the control parameters that you have used. I have used 73xx boards for very dynamical systems and I have always been able to find control parameters that resulted in a very fast and stable system behavior.

For the case that you need some help with tuning please have a look at this link. In many cases autotuning doesn't result in good system behavior but you will find a lot of interesting hints about the manual tuning process there (e. g. that increasing the Kd gain typically results in a better damped system).

If this doesn't help please attach some screenshots from your step response and the control parameters that you have used.

Best regards,

Jochen Klier
National Instruments Germany