How can I stabilize this simulink model ??

Hi everyone,

I built a model in simulink representing the propulsion plant of a ship. The simulation is supposed to run for 1050s but it runs only for about 108s and after that it is blocked. When I change the value of any of its design parameters the simulation stops at an earlier time with an error message about singularity or is blocked at a simulation time less than 108s.

So I have decided to set the simulation time to 100s. When I do not change the value of any of the design parameters of the model, the simulation runs until the end of the 100s. But the problem is that the results are not as they should be and the model is very unstable.

To stabilize the model I tried many tools of Simulink: PID tuner, control system tuner, linear analysis, parameter estimation, response optimization, sensitivity analysis.But no one of them was able to solve my problem.

I have joined to my question the complete model of the ship propulsion plant, the input to this model is the fuel rack generated by the PID controller, and the output of the model is the simulated speed of the engine of the ship. In the 2 other models (curves1 and curves2) you will find respectively, the correct curve of the simulated speed of the engine during a simulation time set to 100s, and the curve of the speed ordered during a simulation time set to 1050s and the correct curve of the simulated speed of the engine during a simulation time set to 1050s. The correct curves (in curves1 and curves2) were generated by another simulation of the same ship equipped with the same engine but using a different modelling approach.

Finally, I have added the m-file containing the values and the definitions of all the design parameters used in the model.

I hope that someone can help with this problem, because I have spent 4 months trying to solve it without any concrete results.

Thank you in advance.