Are omega_0 and delta actually variables? They kinda look like parameters. What happens when you add the parameter keyword?

OK. The parameter keyword didn't matter (still probably, not a bad idea though).

Using initial equations instead of start values fixes the problem, though. Perhaps someone else can explain why this is:

model SMP

    Real y; 

    Real y_dot; 

    Real omega_0=5.0; 

    Real delta=0.2;

initial equation

    y = 5;

    y_dot = 0;

equation 

    y_dot = der(y); 

    der(y_dot) + 2.0*delta*omega_0*der(y) + omega_0^2*y = 0; 

end SMP; 

Dave wrote:

Code:

Real y(start=5);

Real y_dot(start=0);

Any reason why I am getting this error?

Since without fixing the start value by the fixed attribute (fixed=true) this are just initial guess and not initial conditions.

watkipet wrote:

Are omega_0 and delta actually variables? They kinda look like parameters. What happens when you add the parameter keyword?

Yes, omega_0 and delta are variables, but are treated like parameters while the compile process. The difference is that this variable as parameters are changeable after the compile process.