How to simulate overconstrained simscape model?

Hello,

I would like to use a simscape model of Permanent Magnet Synchronous Motor to estimate input power required to achieve defined torque.

In my understanding of the situation, I need to prescribe torque (through variable) flowing from the rotor of PMSM to the inertia. Torque source is not suitable - it generates diferrence of across variable.

Ideal torque source code:

variables(Access = protected)
    w = { 0, 'rad/s' };     % Angular velocity
    t = { 0, 'N*m' };       % Torque
end

branches
    t : R.t -> C.t;
end

equations
    w == C.w - R.w;
    t == -S;
end

I tried to edit the source code of the ideal torque source and defined the zero diferrence of across variable. Simscape refused to compile because I have more equations then variables in my block...

equations
    w == C.w - R.w;
    w == 0;
    t == -S;
end

Is there a way to define the through variable in particular physical branch without affecting its across variable? Is my approach correct?

Thank you for any kind of help.

Answer 1

[Kartik Saxena]

Hi,

If you want to prescribe a torque to the rotor of a Permanent Magnet Synchronous Motor (PMSM) without affecting the angular velocity (i.e., without creating a difference in angular velocity across the connection), you cannot simply set the angular velocity difference to zero, as this would create an overconstrained system.

Instead, you should use an ideal torque source and connect it in such a way that it applies the desired torque to the motor shaft. The ideal torque source in Simscape allows you to specify a torque directly, and the motor will respond to this torque based on its dynamics and the rest of the system.

For more information on using the Ideal Torque Source block and other Simscape components, refer to the following MathWorks documentation: https://www.mathworks.com/help/simscape/ref/idealtorquesource.html

I hope this resolves your issue.