Simulation Error with Fixed-Step Solver

I'm running a Simulink model with a 99×2 double array from the workspace, where each row represents a control input every 0.5 seconds (the first column contains the time values). I've configured the solver settings to fixed-step (automatic solver selection) with a 0.5-second sample time.

However, during compilation I receive the following error:

Error: An error occurred during simulation and the simulation was terminated

Caused by:

['go2_elips/Solver Configuration1']: Error evaluating equations at time 0.75. Stopping simulation. There may be a singularity in the solution. If not, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)

['go2_elips/6-DOF Joint1']: 'go2_elips/6-DOF Joint1' has a degenerate mass distribution on its follower side.

Any idea what might be causing this?

Answer 1

[Jaskirat]

Hi @Ben Navon,

The diagnostic indicates you have a degree of freedom with no inertia associated with it. Fixing this in the model should solve the error. A very common cause for this is using a point mass.

Changing the “Inertia->Type” in the Inertia block from “Point Mass” to “Custom” should fix the problem and allow you to simulate the model.

Hope this helps!

[Ben Navon]

I changed the inertia type to “Custom,” but the issue still isn't resolved.

[Jaskirat]

Hi,

As I mentioned before, the error is usually caused due to having a degree of freedom with no inertia associated with it; the suggested fix works if this is caused by using a point mass, and may not be applicable for every case. It would be impossible to determine the exact cause without looking at the model.

That being said, another cause of the error could be due to the solver being unable to handle large fluctuations. You can refer to the following MATLAB Answer to check if this solution works for you:

https://www.mathworks.com/matlabcentral/answers/474563-error-in-simulink-singularity-in-solution#answer_386766