Why are the gears within my Simscape Multibody model not interacting with each other even after constraining them with the proper gear constraint?

I am using Simscape Multibody within MATLAB R2019b to model a simple gear interaction (bad_worm_and_gear.slx). In order to properly constrain the two gears, I am following the documentation linked below to create and configure my model:

https://www.mathworks.com/help/sm/ug/satisfying-gear-assembly-requirements.html

When I go to run my simulation, I notice that the gears are not interacting with each other as expected. I tried changing my version of MATLAB, but I observed the same behavior.

What is causing this unexpected behavior and how can I resolve this issue?

Answer 1

[MathWorks Support Team]

Within your model bad_worm_and_gear.slx, the consistency tolerance of 1e-1 is causing the issues you described above. The current setting provides the solver with too much “play” or tolerance when constructing the system of equations. As a result, the solver actually considers the corresponding equations for the worm gear to be considered redundant; therefore, it is ignored during the solving process.

Generally, the default value of 1e-9 is a good choice, but in very rare cases (e.g. extremely complex CAD models), a consistency tolerance as large as 1e-6 may also be acceptable.

For your particular model, changing the original consistency of 1e-1 to 1e-9 results in the expected behavior for the model (good_worm_and_gear.slx).