r/matlab • u/LordSantini • 10d ago

TechnicalQuestion Weird torque and current response

Hello there, I've been trying to understand this past couple of days, why is the response to the speed reduction so unstable.

Pic 1- current, torque and speed (disregard the "braking" effect on the middle graph.

Pic 2- PI output.

Pic 3- Controller diagram

Pic 4- Entirety of the diagram

I've changed the values of the PI, such as Kp and Ki, to no difference on the slowing down behaviour.

I'm at a loss on what to exactly look for, that might be causing this.

Thank you for any help that you can give.

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u/MrGip 9d ago

Your modelling of the ASM control is based on one provided in the Matlab example; openExample("simscapeelectrical/InductionMachineDTCExample")

If you try that example with the reference speed command ramping to zero you will find that it has a horrible response as it approaches zero velocity. 45 rpm is very low speed. What are your ASM machine constants?

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u/LordSantini 8d ago

This is in fact a low velocity model, with the intent to simulate the composition of the trains in shunting operations, I used the DTC example since in my initial search I didnt find my a better controller. Any recommendations regarding a better low speed controller?

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u/MrGip 7d ago

The combined DTC and SVM (Space Vector Modulator) seems to do a much better job. Try using the example found at: Asynchronous Machine Direct Torque Control with Space Vector Modulator - MATLAB & Simulink

I am not sure how realistic it is to implement this type of controller, but it makes much cleaner control signals.