package SpringMassDamperPackage
  // Plant
  model Plant
    parameter Modelica.SIunits.Mass m = 1;
    parameter Modelica.SIunits.TranslationalSpringConstant k = 1;
    parameter Modelica.SIunits.TranslationalDampingConstant b = 0.1;
    Modelica.SIunits.Position x(start = 1, fixed = true) "Position";
    Modelica.SIunits.Velocity v(start = 0, fixed = true) "Velocity";
    Modelica.SIunits.Force f "Force";
  equation
    assert(m > 0, "Mass is outside of the domain of validity", AssertionLevel.error);
    der(x) = v;
    m * der(v) = f - k * x - b * v;
  end Plant;
  //Controller
  model Controller
    extends Plant;
    constant Real K = 1 "Gain of speed P controller";
    constant Modelica.SIunits.Velocity vref = 2 "Speed ref.";
    discrete Real vd;
    discrete Real u;
  equation
    when sample(0, 1) then
          vd = v;
      u = K * (vref - vd);
      f = u;
    
    end when;
  end Controller;
end SpringMassDamperPackage;