Motor PI controllers

[Sam_3]

Hi,

I am new to motor PI controllers.

I am building a Field oriented control of a motor. There are two cascading loops. One for current controller and one for speed controller.
I know that in order to have proper control, bandwidth of the inner controller should be 10 times higher than the outer control loop. However, we can select any bandwidth for the speed controller. I have few questions related to this. I would be glad if someone could help me to figure these out.

1. How can I select the most suitable bandwidth for the speed controller.
2. Does the operating speed range varies depending on the bandwidth or the PI gains of my speed controller?
3. If so,how can I determine the operating speed range mathematically before working experimentally?
4. Does at low speeds high torque conditions we need a higher bandwidth, If so, the reason for that?
5. How can I determine mathematically at a specific speed, how much torque can be handled by the given PI setting?

Thank you loads for helping me out
Kind regards
Sam

 

[IRstuff]

The bandwidth depends on what you need the motor to do and how quickly you want it done. For example, a servo loop motor might need to respond 30-Hz events, and the control loops would be scaled accordingly.

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[Sam_3]

Hi IRstuff,

Thank you for your reply.

Any idea about the speed range for the specific bandwidth.
For example lets say I want to run the motor (PMSM) at 30 rpm and 1200 rpm at different loads (1 Nm and 10 Nm). Will the bandwidth of the speed controller is same as 30 rpm 10 Nm case and 1200 rpm 10 Nm case. If not, How can I determine which bandwidth is suitable for that specific speed and torque range.

Thank you for your kind consideration.
Kind regards
Sam