I created a minimal example (DC-Voltage, Load) in OpenModelica. Afterwards, I created an FMU and used it via Python.
Problem summary: By using just a Resistor as a load, i can´t change the parameters via python. After adding an Inductor to the model, I can change some parameters and the simulation reacts to this changes.
In this simple model, there is nothing which could cause troubles from the electrical engineering part, the problem must be somewhere else.
Model Set-up
Problematical Model:
model testbench
parameter Real v_DC (start = 100);
Modelica.Blocks.Sources.RealExpression realExpression(y = v_DC) annotation(
Placement(visible = true, transformation(origin = {-70, 70}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Sources.SignalVoltage signalVoltage annotation(
Placement(visible = true, transformation(origin = {-30, 46}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Basic.Resistor resistor(R = 10) annotation(
Placement(visible = true, transformation(origin = {-30, 14}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Basic.Ground ground annotation(
Placement(visible = true, transformation(origin = {28, 28}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
equation
connect(realExpression.y, signalVoltage.v) annotation(
Line(points = {{-58, 70}, {-30, 70}, {-30, 58}, {-30, 58}}, color = {0, 0, 127}));
connect(signalVoltage.n, resistor.n) annotation(
Line(points = {{-20, 46}, {-6, 46}, {-6, 14}, {-20, 14}, {-20, 14}}, color = {0, 0, 255}));
connect(signalVoltage.n, ground.p) annotation(
Line(points = {{-20, 46}, {28, 46}, {28, 38}, {28, 38}}, color = {0, 0, 255}));
connect(resistor.p, signalVoltage.p) annotation(
Line(points = {{-40, 14}, {-40, 14}, {-40, 46}, {-40, 46}}, color = {0, 0, 255}));
annotation(
uses(Modelica(version = "3.2.3")));
end testbench;
Partly working model:
model testbench
parameter Real v_DC (start = 100);
Modelica.Blocks.Sources.RealExpression realExpression(y = v_DC) annotation(
Placement(visible = true, transformation(origin = {-70, 70}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Sources.SignalVoltage signalVoltage annotation(
Placement(visible = true, transformation(origin = {-30, 46}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Basic.Resistor resistor(R = 10) annotation(
Placement(visible = true, transformation(origin = {-30, 14}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Basic.Ground ground annotation(
Placement(visible = true, transformation(origin = {28, 28}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Basic.Inductor inductor annotation(
Placement(visible = true, transformation(origin = {-60, 14}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
equation
connect(realExpression.y, signalVoltage.v) annotation(
Line(points = {{-58, 70}, {-30, 70}, {-30, 58}, {-30, 58}}, color = {0, 0, 127}));
connect(signalVoltage.n, resistor.n) annotation(
Line(points = {{-20, 46}, {-6, 46}, {-6, 14}, {-20, 14}, {-20, 14}}, color = {0, 0, 255}));
connect(signalVoltage.n, ground.p) annotation(
Line(points = {{-20, 46}, {28, 46}, {28, 38}, {28, 38}}, color = {0, 0, 255}));
connect(inductor.n, resistor.p) annotation(
Line(points = {{-50, 14}, {-40, 14}, {-40, 14}, {-40, 14}}, color = {0, 0, 255}));
connect(signalVoltage.p, inductor.p) annotation(
Line(points = {{-40, 46}, {-74, 46}, {-74, 14}, {-70, 14}, {-70, 14}}, color = {0, 0, 255}));
annotation(
uses(Modelica(version = "3.2.3")));
end testbench;
Used Software
- Windows 10
- OpenModelica 1.16.0
- PyFMI 2.5
- Spyder 3.3.6
FMU Creation
Created the FMU with a .mos file with the following settings:
OpenModelica.Scripting.loadFile("testbench.mo"); getErrorString();
setCommandLineOptions("-d=newInst"); getErrorString();
setCommandLineOptions("-d=initialization"); getErrorString();
setCommandLineOptions("--simCodeTarget=Cpp"); getErrorString();
setCommandLineOptions("-d=-disableDirectionalDerivatives"); getErrorString();
OpenModelica.Scripting.translateModelFMU(testbench, version="2.0", fmuType = "me"); getErrorString();
Python code for testing
import pylab as P
import numpy as N
from pyfmi import load_fmu
def run_demo(with_plots=True):
model = load_fmu('testbench.fmu')
Tstart = 0.0 #
Tend = 0.1
dt = 0.0001
model.setup_experiment(start_time = Tstart)
model.enter_initialization_mode()
model.exit_initialization_mode()
time = Tstart
model.enter_continuous_time_mode()
x = model.continuous_states
model.set('resistor.R', 1000)
model.set('v_DC', 5700)
vref = [model.get_variable_valueref('resistor.i')]
vref2 = [model.get_variable_valueref('resistor.R')]
t_sol = [Tstart]
sol = [model.get_real(vref)]
sol2 = [model.get_real(vref2)]
while time < Tend:
dx = model.get_derivatives()
time = time + dt
model.time = time
x = x + dt*dx
model.continuous_states = x
t_sol += [time]
sol += [model.get_real(vref)]
sol2 += [model.get_real(vref2)]
if with_plots:
P.figure(1)
P.plot(t_sol,N.array(sol)[:,0])
P.title(model.get_name())
P.ylabel('Current at Resistor1 (A)')
P.xlabel('Time (s)')
P.figure(2)
P.plot(t_sol,N.array(sol2)[:,0])
P.title(model.get_name())
P.ylabel('Resistor1 (Ohm)')
P.xlabel('Time (s)')
if __name__ == "__main__":
run_demo()
Bugs
In the second model (with the inductor), a change of the DC voltage (model.set('v_DC', 5700)) leads to a proportional change of the current at resistor1. This works as it should.
A change of the value of the resistor (model.set('resistor.R', 10000)) does not affect the current in the resistor in any way. The printing the value shows the one which was actually set (see second plotted figure), but for the calculation of the current, the default value which was selected in OpenModelica is used.
In the first model (without inductor), neither a change in the DC voltage nor a change in the Resistor affect the current in the resistor, though should.
Within other models, changing the value of the resistor works with the demanded result, and we had difficulties setting the voltage of the source.
Is there a mistake in the way of setting the parameters, a bug in OpenModelica, in PyFMI, or what is going on here?