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Initializing issues in a control problem

#7988  Permalink Top

Initializing issues in a control problem

Jul-25-17 11:02:56

I want to simulate a connected-tanks system where the level in tanks is controlled by PI controllers. The system starts off in a steady state which is not the set point. This is leading to initialization problems because at initialization, we want the inputs have arbitrary values not corresponding to the control law. Below is a minimal example of one tank.

Code:




model controlTest

  

  

  parameter Real mu = 0.5;

  parameter Real sp = 0.5;

  parameter Real Kp = 0.01;

  parameter Real Ti = 10;

  parameter Real g = 9.81;

  

  Real x(start = 1.0, fixed = true);

  Real u(start = 2.215);

  

  Real e;

  Real eI(start = 0, fixed = true);

  

  equation

  

  der(x) = u - mu*sqrt(2*g*x);

  e = -(x - sp);

  der(eI) = e;

  u = max(0, Kp*(e + eI/Ti));

  

  



  

  annotation(

    experiment(StartTime = 0, StopTime = 1000, Tolerance = 1e-06, Interval = 0.002));

end controlTest;

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