Long simulation times with flexible simscape

Hello everybody,

I've been using flexible multibody simscape for a few days.

I have found the simulations to be very slow both using the default bodies and using Reduce Order. is this a common problem?

how can i fix it?

Answer 1

[Praharshita]

Dear Rosario,

I understand that you are facing an issue of slow simulation using default bodies and reduced order.

This issue can happen in large models combining Simscape and Simscape Multibody. In most cases, this issue has been observed in models where prismatic joints in Simscape Multibody are interfaced with Hydraulic Cylinders from Simscape Fluids.

The root cause of this issue is the size of the numerical perturbation used to compute the solver Jacobian, relative to the amplitude of the state. For this type of model, the perturbation can be too small, leading to numerical noise in the Jacobian computation process.

A technique that can help with this kind of robustness issue is Simscape nominal values.

To view if nominal values could help the numerical robustness of the model, run the simulation through the Solver Profiler and then launch the

States Explorer. In the State Explorer, rank the states by State Value.

If you identify states belonging to Simscape blocks that take very large values, it is recommended that you scale them down using nominal values. See the documentation for how to specify nominal values for individual states or for all the states with a similar unit.

We recommend scaling states so they operate mostly in the -1 to 1 range.