MATLAB/Simulink error

Hello,

I am trying to run this model, where the gains and transport delay are constants.

However, I get the following error and I am not sure why:

Error due to multiple causes.

Caused by:

Error in port widths or dimensions. 'Output Port 1' of '.../Transport Delay' has 2 elements. This port does not accept the dimensions (or orientation) specified by the output signal.

Error in port widths or dimensions. Invalid dimension has been specified for 'Input Port 1' of '.../Gnm'.

Thank you very much for your help!

[Benjamin Thompson]

Can you post the Simulink model?

[Jon]

Can you also please attach a script that assigns all of the inputs, e.g. ref_signal, Kp and Kr for your from workspace block so that we can try to replicate the problem. Also, the model in your screenshot is a little different than the one you attached. It uses the from workspace blocks and products for Kp and Kr rather than the gains shown in your screenshot. I assume though that the problem also occurs with the model you have attached

[aeropista]

Indeed, the same error occures for the model in the picture and the one I attached. Here is the workspace I use.

[aeropista]

and the plant code

Answer 1

[Jon]

It looks like your problem may be that you have a SISO (single input single output) transfer function block (Gnm) but the input to it comes from a two dimensional signal and the SISO block doesn't know what to do with the second input signal. The fact that there are two signals seems to trace back to some of the other blocks such as the MATLAB function block within the Plant subsystem whose output signal has dimension of two, and also the integrator block inside that subsystem that has two initial conditions (implying it also provides a two dimensional output.

So either you didn't intend for those blocks to be two dimensional and you will need to correct that, or you need to replace the SISO transfer function block with a MIMO, or at least MISO one.

Finally, your from workspace block ref_signal is only one dimensional, so do you really just want to add that one signal to both of the plant outputs, or again did you intend the output of your plant to be one dimensional.

By the way even with your attached model and the workspace.mat there were some additional errors that needed fixing. Kp and Kr should just be constants, not from workspace blocks unless they are time varying. You also didn't assign a value for the delay parameter of the delay block.

Hope this helps

[aeropista]

Thank you very much Jon

[Jon]

Glad you got it working. One thing I was curious about, was the code inside of the MATLAB function block:

function y_dot = fcn(u, dynamics_case, speed_case, transition)
    t = u(1);
    u_c = u(2);
    y_prev = u(3:4);
    
    if transition == 0
        y_dot = models.plant(dynamics_case, speed_case, t, u_c, y_prev);
    elseif transition == 1
        y_dot = models.plant_3_phases(dynamics_case, speed_case, t, u_c, y_prev);
    else 
        y_dot = [0;0];
    end
end

I was trying to understand where the function models.plant () is defined. I never have seen that usage before. Is "models" somehow assigned in your MATLAB base workspace?

[aeropista]

Indeed, models is a folder in my workspace.