time make my program unstable

i have a simulation program that works very good with a good response (stable system ) .... but after 400 seconds ... the result become unstable without any resone and no error messages .... i try to change the solver and the sample time but the result also become unstable at second 400.... so does any one have an idea about how to solve that ??? thanx

Answer 1

[Azzi Abdelmalek]

I don't think that your system becomes unstable for no reasons. set your stop time to a value before your system becomes unstable. For example stop time=400. Then check your output signals if their values are not bigger then whet they should be. You have to check all your signals

[Azzi Abdelmalek]

Have you checked all your intermediate signals ?