Modelling a moving pulley in Simscape Multibody/ simulating a cable disengaging with a pulley

Hi, I'm a beginner to Simscape Multibody and I’m having a problem that I think is a little advanced for me. I am attempting to simulate a cable that is constrained around a pulley for part of the simulation, and free from it in another part. This is normally not possible with a Simscape pulley because the cable must always be partially wrapped around it to simulate.

However, I found a suggestion on this forum to wrap the pulley 360 degrees and move the pulley along the path of the cable once the unconstrained pulley condition is met. I have created a frame with prismatic joint that moves along the cable, however connecting a pulley block to this arrangement results in the following error:

An error occurred while running the simulation and the simulation was terminated

Caused by: ['ArmSupport/Pulley', 'ArmSupport/Solver Configuration']: 'ArmSupport/Pulley' 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.

Component:Simulink | Category:Block error

Can anyone provide some clarity on this please?

Answer 1

[Steve Miller]

That diagnostic can indicate a number of problems with your model.

Common reasons for this diagnostic are:

• Your solver settings are permitting the simulation to take too large of a time step
• A degree of freedom whose motion is prescribed (distance/angle defined in time) is blocked by another constraint.

If you can share the model we might be able to diagnose it further.

Thanks,

--Steve