Identify multiple parameters with nonlinear greybox model matlab

Hello everybody,

I am currently trying to estimate the Parameters of a nonlinear single track model of the following modelstructure:

dx = [A1,A2; A3, A4]* [Beta;dPsi] + [B1;B2]*Delta

y = [1,1]*[Beta;dPsi]

The Parameters that should be identified are A1,A2,A3,A4,B1 and B2. After the model setup, Matlab tells me that " _The specified model parameters or states are infeasible for simulation. Verify that the model's ODE file ("stm") can be simulated with the given parameters and initial states values."

I have attached the model for the greymox model structure and the linke file stm. I would very thankful, if someone of the experienced Users could help me :)

Thank you very much in advance!