OpenModelica: Input in second level for FMU export

Question

I have a model, create an FMU out of it, and want to import it in to python.

Having inputs on the first canvas works, and transferring them to the blocks which are used works, too.

Because of the architecture of the python code, i need to have the prefix for the inputs as for the rest of the block.

I made a minimal example:

package testi
  model source
    Modelica.Electrical.Analog.Sources.SignalVoltage signalVoltage annotation(
      Placement(visible = true, transformation(origin = {0, 36}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Electrical.Analog.Basic.Ground ground annotation(
      Placement(visible = true, transformation(origin = {48, 22}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Electrical.Analog.Interfaces.Pin pin annotation(
      Placement(visible = true, transformation(origin = {100, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0), iconTransformation(origin = {100, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Blocks.Interfaces.RealInput u annotation(
      Placement(visible = true, transformation(origin = {0, 108}, extent = {{-20, -20}, {20, 20}}, rotation = -90), iconTransformation(origin = {0, 108}, extent = {{-20, -20}, {20, 20}}, rotation = -90)));
  equation
    connect(signalVoltage.n, ground.p) annotation(
      Line(points = {{10, 36}, {48, 36}, {48, 32}}, color = {0, 0, 255}));
  connect(signalVoltage.p, pin) annotation(
      Line(points = {{-10, 36}, {-20, 36}, {-20, 0}, {100, 0}, {100, 0}}, color = {0, 0, 255}));
  connect(signalVoltage.v, u) annotation(
      Line(points = {{0, 48}, {0, 48}, {0, 108}, {0, 108}}, color = {0, 0, 127}));
  end source;

  model base
  testi.source source1 annotation(
      Placement(visible = true, transformation(origin = {-42, 40}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  testi.measurement measurement1 annotation(
      Placement(visible = true, transformation(origin = {44, 40}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  equation
    connect(source1.pin, measurement1.pin) annotation(
      Line(points = {{-32, 40}, {34, 40}}, color = {0, 0, 255}));
  end base;

  model measurement
  Modelica.Electrical.Analog.Basic.Resistor resistor annotation(
      Placement(visible = true, transformation(origin = {-24, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Electrical.Analog.Interfaces.Pin pin annotation(
      Placement(visible = true, transformation(origin = {-100, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0), iconTransformation(origin = {-100, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Electrical.Analog.Basic.Ground ground annotation(
      Placement(visible = true, transformation(origin = {30, -28}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  equation
    connect(pin, resistor.p) annotation(
      Line(points = {{-100, 0}, {-34, 0}}, color = {0, 0, 255}));
  connect(resistor.n, ground.p) annotation(
      Line(points = {{-14, 0}, {30, 0}, {30, -18}, {30, -18}}, color = {0, 0, 255}));
  end measurement;
  annotation(
    uses(Modelica(version = "3.2.3")));
end testi;

Trying to create the FMU causes the error: Undetermined equation system: 23 equations, 24 variables, although i would provide the input "source.u" via python. If I create an additional Input directly in the base model and connect it to the input of the source, it works, but then i do not have the same prefix "source.u" in my python code, which i would really like to have.

Does anyone know a way to solve this problem?

AnHeuermann AnHeuermann · Accepted Answer · 2020-07-02T13:14:10

Define a second input u inside model base and connect it to the input of source.u so you only have inputs on the top level of the FMU. Now the FMU will happily compile and you should be able to change source.u from outside.

model base
  Modelica.Blocks.Interfaces.RealInput u;
  testi.source source1;
  testi.measurement measurement1;
equation
  connect(source1.pin, measurement1.pin);
  connect(u, source1.u);
end base;

OpenModelica: Input in second level for FMU export

1 Answers