Why is my Simscape Multibody model using the Reduced Order Flexible Solid block hangs or errors out?

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I am simulating a Simscape Multibody model where the Reduced Order Flexible Solid block is used in a closed kinematic loop along with the Spatial Contact force block.
When simulating the model using a variable-step solver, the simulation has a tendency to hang (take very small steps) when oscillations are damping out toward zero.
When simulating the model using a fixed-step solver like ode14x or ode1be, the simulation results are showing unexpected "jumps" or disturbances when the system should be close to a steady state. In some cases, the simulation can also error out with:
An error occurred while running the simulation and the simulation was terminated
Caused by: ['blockpath']: kinematic constraints cannot be maintained. Check solver type and consistency tolerance in the Simscape Solver Configuration block. Check Simulink solver type and tolerances in Model Configuration Parameters. A kinematic singularity might be the source of this problem.

Accepted Answer

MathWorks Support Team
MathWorks Support Team on 5 Aug 2022
This issue might be due to the perturbation level used by Simulink stiff solvers. When the states of the Reduced Order Flexible Solid block have a small amplitude, numerical noise can be introduced in the Jacobian computation, leading to such issues.
As a workaround, try executing attached file plimitDerivativePerturbations.p to limit the perturbation level used by stiff solvers. This file needs to be executed once per MATLAB session

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