Question

I have the following Simulink model:

I would like to externally provide inputs u[k] and y[k], i.e., I will be running simulations via MATLAB command line. I found previously that I could set the [LoadExternalInput and ExternalInput][3] options, and they default to the vector [t u].

But my u[k] and y[k] are vectors, and it looks like the ExternalInput can only specify one vector. So each row of [t u] is the value of the entire vector u at time t.

The sizes of u[k] and y[k] in my model here are not necessarily known ahead of time. Is there a way to pass in these vectors (as structs, perhaps)?

Answer 1

From Importing Data to Root-Level Input Ports I’ve found that I could do something like

sim('myModel', 'LoadExternalInput', 'on', 'ExternalInput', 'u, y');

where u and y are structures with fields time, signals.values, and signals.dimensions; each row of signals.values is a vector corresponding to a n element of time. signals.dimensions is the dimension of signals.values. I have to manually set the In1 ports to expect the same dimension as u.signals.values (well, I can of course do it programatically before hand..):

Note You must set the Port dimensions parameter of the Inport or the Trigger block to be the same value as the dimensions field of the corresponding input structure. If the values differ, an error message is displayed when you try to simulate the model.

(from "Importing Data Structures to a Root-Level Input Port")

What’s the point of setting signals.dimensions if I have to set the dimension on the In1 block manually anyhow? Anyway that might have to be how I do this: just examine u and y before running the simulation, then setting the Inblock properties (programatically, of course) to expect vectors of that length.

I am still hoping there is a more elegant solution for this.