Changing input type in PMSM Field oriented control

Hello everyone,

I am doing my thesis on safety critical control for electric drives, I am using the existing model in simulink named Permanent Magnet Synchronous Motor Field Oriented Control attached below

To build a robust control strategy, I want to try the existing PI controllers for different inputs, currently there is only a step input present (which goes to an amplitude equal to third of the motor base speed), I want to implement a sine wave input, however, when doing so, it appears as a square wave, this is because the sample time has to be -1 since it is present in an inherited block. It appears like in the image below, as opposed to a clean sine-wave. I cannot use a sample time of 0 because it displays the error "Consider setting the sample time for the block 'Possibility_1_sensorless_FOC_PMSM/Serial Receive/SCI_Rx/Simulation/Sine Wave' to inherited (-1) if the block has a sample time parameter".

Does anyone know how to solve this, apologies for the long question and suggestions are highly appreciated

Answer 1

[Joel Van Sickel]

Hello Rohan,

your sine wave is being digitzed at the controller rate of input for that signal. In this case, I'm assuming it's the blue signal. To get higher resolution, you will need to increase the rate of the speed control loop. This will also require you to retune the speed control PI loop. However, your sine wave will always be digitized, and it doesn't matter for testing the speed control loop if it is digitized or not. It might not look like a smooth sine wave, but that doesn't affect anything regarding safety critical opertaion. However, if you have an application that requires higher resolutin of your speed, or smoother transitions between speeds, then that would be a good reason to try and run the speed loop faster and retune the control loop.

[Rohan]

Sorry for the late response, thanks a lot for the suggestion, I will try to work it out and see if it works !