Complex Data type not accepted in Simulink

Hello Everyone, I am having an issue with the interaction of matlab function block in the simulink with my model block. Below you can also find the picture.

I have created a matlab function with three inputs and 1 output. Since in the matlab function block, i have solved an differential equation, it has complex expressions in the form of for example .

(exp(sqrt(-a/b)))

This generates the output of complex data type from the function block. When passing this to the integrator which is the input to my plant, I cannnot run the simulink due to the error

"Cannot pass the complex value to non-complex location"

I tried chaning the data types of integrator, then the same thing happens to other blocks in the simulink.

I also tried using absolute values, which ofcourse gives real number, but turns out to be very large numbr and genrates high magnitude. I really need help in solving this issue.

Can anyone help me in this/

Thanks in advance.

[Walter Roberson]

https://dsp.stackexchange.com/questions/53554/how-to-model-state-space-for-complex-valued-system-correctly-in-simulink-matlab

[Prateek Tiwari]

Hello Walter,

My model/plant is a transfer function, using state space will complicate my simulink model, because I am doing a simlation for platoon of vehicles. Is there any other way to solve this?

[Walter Roberson]

"I have created a matlab function with three inputs and 1 output. "

"When passing this to the integrator"

"I am doing a simlation for platoon of vehicles."

The integrator block in Simulink remembers the previous state. Therefore if you have a platoon of N vehicles, you cannot simply stream N signals from the function block into the integrator to get N integrated values: you would need N such integrators so that each of the N remembers the state properly.

If you vectorize the task so that your function takes 3*N inputs and has N outputs, then you can express the MATLAB equivalent of integrating each seperately as

temp = repmat({tf(1, [1 0]}, 1, N);
integrate_all = blkdiag(temp{:});   [1/s, 0, 0, 0, ...; 0, 1/s, 0, 0, 0, ...0, 0, 1/s, 0, 0, ...]

and the state-space equivalent of this turns out to be:

A = zeros(N,N);
B = eye(N);
C = eye(N);
D = zeros(N,N);

which should be easy to initialize in simulink.

[Prateek Tiwari]

Hello Walter,

I know what are you trying to say, however, I only refered to the platoon of vehicles to let you know the model is bit complicated and therefore I did not put all the details here.

The question I have asked is not for all the N vehicles. This is for 1 vehicle.

[Prateek Tiwari]

Addiotnally, my question is only about, what is an alternative of sending the complex values to any simulink block. In other words, how can I solve the error states above in the question, such that integrator or LTI system block accept the complex values as well.

[Walter Roberson]

In past post, Mathworks employees say that if you need to use an integrator with complex values, then seperate real and complex parts and integrate them seperately. You indicated that you tried that but the coefficients got large. If you have a rotary motion, then the information about wrapping values on the Integrator page might help.

[Walter Roberson]

There is no configuration setting for the integration block in particular or Simulink in general to have it be happy about complex inputs to the integration, nor to have it accept such inputs with a warning.