Error using the library Modelica_LinearSystems2 in OpenModelica - modelica

Question

I am trying to use the Kalman Filter from the Modelica_LinearSystem2 Library (Modelica_LinearSystems2.WorkInProgress.Controller.KalmanFilter.KF) in OpenModelica, but it seems the functions of the library are not working properly in my test models.
To find the problem I copied the code example from the documentation (https://build.openmodelica.org/Documentation/Modelica_LinearSystems2.StateSpace.%27constructor%27.fromABCDMatrices.html)
model test3
Real A[1,1] = [1];
Real B[1,1] = [1];
Real C[1,1] = [1];
Real D[1,1] = [0];
public
Modelica_LinearSystems2.StateSpace ss;
algorithm
ss := Modelica_LinearSystems2.StateSpace.'constructor'.fromABCDMatrices(A, B, C, D);
equation
end test3;
When I click on check model I receive the Error:
[Modelica_LinearSystems2.StateSpace: 7:3-8:68]: Failed to deduce dimension 1 of A due to missing binding equation.
This refers to the line
Real A[:,size(A, 1)];
When I predefine this (and other) matrices with for example
Real A[4,4];
I get the error
Internal error Instantiation of test3 failed with no error message.
My question is: Why is this and how can I prevent these errors?

Answer 1

Findings
It looks like Modelica_LinearSystems2 is only supported by Dymola. The landing page of their github repository states:
Please note that the library is known to work with Dymola only.
It looks as this is still the case. At least on my machine the library Modelica_LinearSystems2 v2.4.1 has serious issues in OpenModelica v1.18.0. Most examples exit with errors or do nothing.
Still, the code in the question does not work in Dymola. Below you find an explanation and corrected examples, which were successfully tested with Dymola. The fundamental problem should be the same in all tools and I hope my solution will also work in OpenModelica once it support the Modelica_LinearSystems2 library.
Original answer (most relevant for Dymola users)
The problem with your example code is that Modelica tools must know the size of vectors, matrices and arrays when a simulation is performed, but not when a function is called. Since you are building a model, the tool assumes that you want to simulate it.
Your code instantiates the StateSpace record ss. ss holds the matrices A, B, C and D. As long as you don't assign anything to ss, their sizes are not known. Of course there is an algorithm, which sets ss, but this happens during simulation. During translation, the size of the matrices in ss cannot be determined. Therefore, a typical Modelica tool requires you to use a binding equation.
To make your snipped work, you can change it to this:
model Demo
Real A[1,1] = [1];
Real B[1,1] = [1];
Real C[1,1] = [1];
Real D[1,1] = [0];
Modelica_LinearSystems2.StateSpace ss = Modelica_LinearSystems2.StateSpace.'constructor'.fromABCDMatrices(A, B, C, D);
end Demo;
Note that ss now has a binding equation. Hence, the size of the matrices inside ss can be determined.
The question is, if you really want to run a simulation with your StateSpace record. Typically, the functions in the liner systems library are used in Modelica functions. In this case your code could look as follows:
function demo
output Modelica_LinearSystems2.StateSpace ss;
protected
Real A[1,1] = [1];
Real B[1,1] = [1];
Real C[1,1] = [1];
Real D[1,1] = [0];
algorithm
ss = Modelica_LinearSystems2.StateSpace.'constructor'.fromABCDMatrices(A, B, C, D);
end demo;
I suggest looking at the various examples in the package Modelica_LinearSystems2.Examples.StateSpace for the correct usage of the StateSpace record.