I'm not able to simulate a stable system in Simulink. States are being increased with no reason

Hi community,

I created a system to simulate quadcopter behavior, and used the parameters of a well known and tested vehicle.

When I try to simulate it, with no inputs (only force in Z axis to hold altitude), the states starts to diverge. May I missing something in Simulink? I tried to set some block as atomic but it didn't solve the problem.

When I disconnect the feedback from states (inputs of Required Prop Loads Block), it works as expected, as shown in picture below.

Answer 1

[Nehemiae]

Hello,

On testing with your model, I am able to get the simulation output when setting the maximum step size to 0.001 and the minimum step size to 0.0001 for the solver settings in the configuration parameters. To avoid out-of-bounds solver conditions, increasing the accuracy of the solver by reducing the step size is often helpful. The documentation on variable step solvers (https://www.mathworks.com/help/simulink/ug/variable-step-solvers-in-simulink-1.html) can be helpful for this.