CODEWITHSUNDEEP
openmodelica
NameOfTheRose
NameOfTheRose

Reputation: 825

Initial Conditions in OpenModelica

Will somebody please explain why the initial conditions are properly taken care of in the following openmodelica model compiled and simulated in OMEdit v1.9.1 beta2 in Windows, but if line 5 is commentd and 6 uncommented (x,y) is initialized to (0.5,0)? Thank you.

class Pendulum "Planar  Pendulum"
constant Real PI = 3.141592653589793;
parameter Real m = 1,g = 9.81,L = 0.5;
Real F "Force of the Rod";
output        Real  x(start=L*sin(PI/4)) ,y(start=-0.35355);
//output Real x(start = L * sin(PI / 4)), y(start=-L*sin(PI/4));
output Real vx,vy;
equation
m * der(vx) = -x / L * F;
m * der(vy) = (-y / L * F) - m * g;
der(x) = vx;
der(y) = vy;
x ^ 2 + y ^ 2 = L ^ 2;
end Pendulum;

Upvotes: 1

Views: 464

Answers (1)

NameOfTheRose
NameOfTheRose

Reputation: 825

The short answer is that initial values are treated merely as hints, you have to add the fixed=true attribute to force them as in:

 output Real x(start=L*cos(PI/4),fixed=true);

If initialized variables are constrained, the fixed attribute should not be used on all initialized variables but on a 'proper' subset, in this case on just one.

The long answer can be found here

Upvotes: 1

Related Questions