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OMC and Corba - Error in initialization. System of initial equations

#1207  Permalink Top

OMC and Corba - Error in initialization. System of initial equations

Jun-08-11 17:29:13

Dear all,
I created a model for a double mass-damper-spring system with PI controllers using OpenModelica.
I would like to use the Corba interface in order to optimize it using an homemade Java application or using the JMetal one (in the future).

I started with simple proportional controllers. It works fine.
But when I add the integrator part (the PI controller from the Modelica library) I get the following error :

Code:


Sending expression:runScript("Systeme_MRA.mos")

Got reply:"true

true

record SimulationResult

    resultFile = \"\",

    simulationOptions = \"startTime = 0.0, stopTime = 10.0, numberOfIntervals = 1000, tolerance = 0.0001, method = 'dassl', fileNamePrefix = 'Systeme_MRA', storeInTemp = false, noClean = false, options = '', outputFormat = 'mat', variableFilter = '.*', measureTime = false, cflags = ''\",

    messages = \"Simulation execution failed for model: Systeme_MRA

Error in initialization. System of initial equations are not consistent.

(Least Square function value is 0.07)

Error in initialization. Solver iterated 100 times without finding a solution

residual[0] = 0.1

residual[7] = 0.1

residual[8] = -0.2

residual[9] = -0.1

Initialization of the current initial set of equations and initial guesses fails!

Try with better Initial guesses for the states.

Error in initialization. Storing results and exiting.



Simulation terminated while the initialization. Could not find suitable initial values.\",

    timeFrontend = 0.0,

    timeBackend = 0.0,

    timeSimCode = 0.0,

    timeTemplates = 0.0,

    timeCompile = 0.0,

    timeSimulation = 0.0,

    timeTotal = 0.0

end SimulationResult;

false

My MOS file is :

Code:

loadModel(Modelica);

loadFile("Systeme_MRA.mo");

simulate(Systeme_MRA,startTime=0.0,stopTime=10.0,numberOfIntervals = 1000,tolerance = 1e-04);

plot({const.y,const1.y,positionSensor.s,positionSensor1.s});

where "Systeme_MRA" is my double mass-spring-damper modelica model, created using OMEdit.

My modelica model:

Code:

model Systeme_MRA

  annotation(Diagram(graphics), uses(Modelica(version = "3.2")), Diagram(graphics));

  Modelica.Mechanics.Translational.Components.SpringDamper springDamper(stateSelect = StateSelect.default, s_nominal = 0.1, s_rel(fixed = true, start = 0), v_rel(fixed = true, start = 0), c = 5, d = 1300, s_rel0 = 0) annotation(Placement(visible = true, transformation(origin = {88,50}, extent = {{-10,10},{10,-10}}, rotation = 270)));

  Modelica.Mechanics.Translational.Components.Fixed fixed annotation(Placement(visible = true, transformation(origin = {88,82}, extent = {{10,10},{-10,-10}}, rotation = 180)));

  Modelica.Mechanics.Translational.Components.Mass mass(m = 120, s(fixed = true), L = 0.2, v(fixed = true), a(fixed = true), stateSelect = StateSelect.default) annotation(Placement(visible = true, transformation(origin = {88,10}, extent = {{-10,10},{10,-10}}, rotation = 270)));

  Modelica.Mechanics.Translational.Sources.Force force1(useSupport = true) annotation(Placement(visible = true, transformation(origin = {32,0}, extent = {{-10,-10},{10,10}}, rotation = 0)));

  Modelica.Mechanics.Translational.Components.SpringDamper springDamper1(stateSelect = StateSelect.default, s_nominal = 0.1, s_rel(fixed = true, start = 0), v_rel(fixed = true, start = 0), c = 3, d = 1000, s_rel0 = 0) annotation(Placement(visible = true, transformation(origin = {88,-28}, extent = {{-10,10},{10,-10}}, rotation = 270)));

  Modelica.Mechanics.Translational.Sensors.PositionSensor positionSensor(s(start = 0, fixed = true)) annotation(Placement(visible = true, transformation(origin = {-4,-16}, extent = {{10,10},{-10,-10}}, rotation = 180)));

  Modelica.Mechanics.Translational.Components.Mass mass1(m = 70, s(fixed = true), L = 0.2, v(fixed = true), a(fixed = true), stateSelect = StateSelect.default) annotation(Placement(visible = true, transformation(origin = {88,-62}, extent = {{-10,10},{10,-10}}, rotation = 270)));

  Modelica.Mechanics.Translational.Sources.Force force(useSupport = true) annotation(Placement(visible = true, transformation(origin = {32,-72}, extent = {{-10,-10},{10,10}}, rotation = 0)));

  Modelica.Blocks.Continuous.PI PIctrl1(k = 1, T = 0.01) annotation(Placement(visible = true, transformation(origin = {-20,-72}, extent = {{-10,-10},{10,10}}, rotation = 0)));

  Modelica.Blocks.Continuous.PI PIctrl(k = 1, T = 0.01) annotation(Placement(visible = true, transformation(origin = {-32,0}, extent = {{-10,-10},{10,10}}, rotation = 0)));

  Modelica.Blocks.Math.Feedback feedback1 annotation(Placement(visible = true, transformation(origin = {-62,-72}, extent = {{-10,-10},{10,10}}, rotation = 0)));

  Modelica.Blocks.Math.Feedback feedback annotation(Placement(visible = true, transformation(origin = {-68,0}, extent = {{-10,-10},{10,10}}, rotation = 0)));

  Modelica.Mechanics.Translational.Sensors.PositionSensor positionSensor1(s(start = 0, fixed = true)) annotation(Placement(visible = true, transformation(origin = {58,-92}, extent = {{10,10},{-10,-10}}, rotation = 180)));

  Modelica.Blocks.Sources.Constant const1(k = 2) annotation(Placement(visible = true, transformation(origin = {-100,-72}, extent = {{-10,-10},{10,10}}, rotation = 0)));

  Modelica.Blocks.Sources.Constant const(k = 1) annotation(Placement(visible = true, transformation(origin = {-104,0}, extent = {{-10,-10},{10,10}}, rotation = 0)));



equation 

  connect(const.y,feedback.u1) annotation(Line(points = {{-93,0},{-76,0}}));

  connect(feedback1.u1,const1.y) annotation(Line(points = {{-70,-72},{-89,-72}}));

  connect(feedback1.u2,positionSensor1.s) annotation(Line(points = {{-62,-80},{-62,-91.9},{47,-91.9}}));

  connect(positionSensor1.flange,mass1.flange_b) annotation(Line(points = {{68,-92},{104,-92},{112,-72},{88,-72}}));

  connect(PIctrl.u,feedback.y) annotation(Line(points = {{-44,0},{-59,0}}));

  connect(feedback.u2,positionSensor.s) annotation(Line(points = {{-68,-8},{-68,-15.9},{-15,-15.9}}));

  connect(PIctrl1.u,feedback1.y) annotation(Line(points = {{-32,-72},{-53,-72}}));

  connect(PIctrl.y,force1.f) annotation(Line(points = {{-21,0},{20,0}}));

  connect(PIctrl1.y,force.f) annotation(Line(points = {{-9,-72},{20,-72}}));

  connect(force.support,springDamper1.flange_a) annotation(Line(points = {{32,-82},{32,-18},{88,-18}}));

  connect(force.flange,mass1.flange_b) annotation(Line(points = {{42,-72},{88,-72}}));

  connect(mass1.flange_a,springDamper1.flange_b) annotation(Line(points = {{88,-52},{88,-38}}));

  connect(positionSensor.flange,mass.flange_b) annotation(Line(points = {{6,-16},{108,-16},{108,-5.55112e-16},{88,-5.55112e-16}}));

  connect(mass.flange_b,springDamper1.flange_a) annotation(Line(points = {{88,-5.55112e-16},{88,-18}}));

  connect(force1.support,springDamper.flange_a) annotation(Line(points = {{32,-10},{32,60},{88,60}}));

  connect(force1.flange,mass.flange_b) annotation(Line(points = {{42,0},{88,0}}));

  connect(springDamper.flange_b,mass.flange_a) annotation(Line(points = {{88,40},{88,20}}));

  connect(fixed.flange,springDamper.flange_a) annotation(Line(points = {{88,82},{88,60}}));

end Systeme_MRA;

It seems to be an issue with the initialisation of my PI controllers.

Could you please tell me how I can solve it?

Thanks in advance for your kindly reply.
Best,

#1211  Permalink Top

Re: OMC and Corba - Error in initialization. System of initial equations

Jun-09-11 14:04:06

Hi,

the problem in your model are not PI controllers, but rather the modifier for the positionSensors. The initialisation problem is overdetermined if you set a  "fixed" start value for the positionSensors and for the SpringDamper. Just change the properties of the positionSensor.
Form


Code:


Modelica.Mechanics.Translational.Sensors.PositionSensor positionSensor(s(start = 0, fixed = true))

Modelica.Mechanics.Translational.Sensors.PositionSensor positionSensor1(s(start = 0, fixed = true))

to

Code:


Modelica.Mechanics.Translational.Sensors.PositionSensor positionSensor 

Modelica.Mechanics.Translational.Sensors.PositionSensor positionSensor1

then the model works fine.

so long.
Willi

#1217  Permalink Top

Re: OMC and Corba - Error in initialization. System of initial equations

Jun-09-11 14:56:05

Hi,
Thanks for your kindly answer.
I edited the model as you suggested and it works perfectly.
Best,

#1223  Permalink Top

Re: OMC and Corba - Error in initialization. System of initial equations

Jun-09-11 17:25:22

Hi,
I just have an another question regarding OMC and Corba.
How can I set parameters to my modelica model using the corba interface and how can I get the simulation results?

In my model, I would like to optimize parameters from the PI controllers by minimizing the sum of quadratic errors:
I'm currently using the JMetal package (I may develop my own algorithm in the future) and I would like to do this as my optimization problem:
- Setting PI parameters (calculated by my optimization algorithm)
- Simulate the model with those parameters
- Get the values from the feedback.y and feedback1.y variables that are containing the error values.
- Calculate the sum of errors using a java function

I would like to know how I can set the parameters that are calculated by my algorithm to my Modelica model (PIctrl.k, PIctrl.T, Pictrl1.k and PIctrl1.T variables) and get simulation results.


Is it possible ?
Best,

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