interactive simulation with OpenModelica using OPC UA interface

Question

I made my second model simulating a gas pipe where we want to simulate the pipe filling by gas to validate our tightness test sequence. The idea was to connect this model to our PLC program using OPC UA interface already included in OpenModelica. When I run the model in Interactive mode, the OPC UA embedded server is well started. I am able to browse model objects using OPC expert as OPC client and data are refreshed following my simulation. For internal validation of my model, I triggered the valve based on condition related to simulation time but

i would like these opening to be written depending on boolean variable written through OPC UA by my PLC.

 Real leak ;
equation
  leak =  if (time > 20) then 0.01 else 0.0;// no leak at staring up to help init
  CO0011_FSV02.opening = if (time > 60) and (time < 70) then 0.05 else  if time > 110 then 1 else leak;
  CO0011_FSV03.opening = if (time > 20) and (time < 30)  or ( time > 110 ) then 1 else leak;
  CO0011_FSV04.opening = if (time > 10) and (time < 100) then 1 else leak;

becomes

//valves commands from PLC
  Boolean YV01;
  Boolean YV02;
  Boolean YV03;
  Boolean YV04; 
equation
  leak =  if (time > 20) then 0.01 else 0.0;// no leak at staring up to help init
//  CO0011_FSV02.opening = if (time > 60) and (time < 70) then 0.05 else  if time > 110 then 1 else leak;
//  CO0011_FSV03.opening = if (time > 20) and (time < 30)  or ( time > 110 ) then 1 else leak;
//  CO0011_FSV04.opening = if (time > 10) and (time < 100) then 1 else leak;
  
  CO0011_FSV02.opening = if YV02 then 0.05 else  if YV01 then 1 else leak;
  CO0011_FSV03.opening = if YV03 then 1 else leak;
  CO0011_FSV04.opening = if YV04 then 1 else leak;

but this give me the following errors messages:

[2] 18:59:41 Symbolique Erreur Too few equations, under-determined system. The model has 239 equation(s) and 243 variable(s).

[3] 18:59:41 Symbolique Avertissement [Gas_supply_test: 34:3-34:15]: Variable YV01 does not have any remaining equation to be solved in. The original equations were: Equation 204: CO0011_FSV02.opening = if YV02 then 0.05 else if YV01 then 1.0 else leak, which needs to solve for YV02

What is the good way to declare these command variables that will be changed online during interactive simulation but do not need to be solved and count by the compiler?

When i define them as parameters, they are no listed nor visible by OPC browser. thanks for any good idea

i changed the YV0n to input and i could compile the simulation and run it in interactive mode. YV01 to YV04 are now visible as boolean data on my OPC Expert UA browser. When simulation is running, the simulation time should be updated on my OPCUA browser but it is not the case, when i try to write a boolean value into YV01, the simulation crashes without any error message — Piwi447, Feb 22 '23 at 17:48

score 0 · Answer 1 · answered Feb 22 '23 at 09:19

0

AFAICT these should be "input" variables: input Boolean YV01; etc. See https://mbe.modelica.university/components/components/component_models/#balanced-components

answered Feb 22 '23 at 09:19

Christoph

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interactive simulation with OpenModelica using OPC UA interface

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