Closed loop speed control


I have a dc motor that is running a pump. this pump has a presure sensor and I would like to controll the pressure of the pump by changing the speed of the pump. this works fine manualy but now i want the pressure to be constant.

the pololu jrk21v3 controller because it offers position or speed feedback options. This board works very good whit position feedback. But the problem is whit speed feedback. When the PID error gets down to 0 also the duty cycle goes down to 0 and my pump is not running ok. the pump is oscilating from almost 0 rpm to full load

what am I doing wrong whit the controller.

I think that the speed controll would work in a diferent way.
when the feedback and the set valeu are the same the duty cycle stays constant and is geting smaller or larger if needed…What is happening to me the duty cycle goes to 0 when the feedback and the set valeu are the same

any solutions

thanked you

How are you providing speed feedback to the controller? What sensor, what wiring, etc.?

It sounds like the problem you described might be from either your PID values not being tuned very well, or your PID period being set too long. What is your PID period set to under the “PID” tab of the Jrk Configuration Utility? Please note that if you change the PID period when using “Frequency (digital)” feedback you will probably have to adjust your feedback scaling settings since the feedback is based on a per PID period basis. Also, could you post your jrk settings file? You can save the settings file by using the “Save settings file…” option under the “File” drop-down menu within the Jrk Configuration Utility.