Hello:

I discovered openmodelica recently, and I'm sincerely impressed by both the ambition and the current status of the project.

I have found around a wide array of examples of modelling, and a few nice resources for system optimization.

I'm not finding many examples of a system with unknown parameters, which are estimated a posteriori by minimization of mean squared error to some observations, for instance. Something like this:a Lotka-Volterra system with unknown growth rates and/or interaction terms:

https://docs.juliahub.com/DifferentialE … stimation/

How do people do this with openmodelica?

Regards

There you go, thanks a lot!

model FirstOrder annotation(uses(Modelica(version="3.2.3")));

  Modelica.SIunits.Position x;

equation

  der(x) = 1-x;

end FirstOrder;

I got a warning recently that I could upgrade to Modelica 4.0.0, but it turns out I didn't upgrade:

> dpkg -l | grep modelica
ii  drmodelica                                    1.17.0-1                                         all          An OMNotebook course in the Modelica language
ii  omlib-modelica-3.2.3                          3.2.3~20201118~124214~git~OM~maint~3.2.3-1       all          Modelica 3.2.3 is a Modelica library
ii  omlib-modelicabyexample-0.5.0                 0.5.0~154~g6044b75-1                             all          ModelicaByExample 0.5.0 is a Modelica library
ii  omlib-modelicareference                       20201118~124214~git~OM~maint~3.2.3-1             all          ModelicaReference is a Modelica library
ii  omlib-modelicaservices-3.2.3                  3.2.3~20201118~124214~git~OM~maint~3.2.3-1       all          ModelicaServices 3.2.3 is a Modelica library
ii  openmodelica                                  1.17.0-1                                         amd64        A complete Modelica environment

Hello everyone:

I started recently learning modelica, but there is a problem I avoided and I really need to solve.

I can import and simulate succesfully, both in OMEdit and through OMPython, models without units such as this:

model FirstOrder

  Real x;

equation

  der(x) = 1-x;

end FirstOrder;

But all of the following fail:

model FirstOrder

  import Modelica.Units.SI;

  SI.Position x;

equation

  der(x) = 1-x;

end FirstOrder;

model FirstOrder

  Modelica.Units.SI.Position x;

equation

  der(x) = 1-x;

end FirstOrder;

model FirstOrder

  import SI = Modelica.SIunits;

  SI.Position x;

equation

  der(x) = 1-x;

end FirstOrder;

I include both examples because of the recent change in notation in Modelica 4, since I'm not really sure if my system uses v4 or v3.2.3, since it says "Notification: Automatically loaded package Modelica 3.2.3 due to uses annotation."

I can import other libraries:

model exer

  import Modelica.Electrical.Analog.Basic;

  Basic.Resistor r(R = 10);

  Basic.Capacitor c(C = 1e-4, v(start = 0));

  Basic.Ground g;

  Modelica.Blocks.Sources.Sine sine(amplitude = 10, freqHz = 10);

  Modelica.Electrical.Analog.Sources.SignalVoltage signalVoltage1;

equation

  connect(sine.y, signalVoltage1.v);

  connect(signalVoltage1.p, r.p);

  connect(r.n, c.p);

  connect(c.n, g.p);

  connect(signalVoltage1.n, g.p);

  annotation(uses(Modelica(version="3.2.3")));

end exer;

Any idea?

Regards