Modeling a Hollow Shaft Using Simscape Multibody

I am trying to model a hollow shaft using MATLAB Simscape. I read the "Compound inertia" article in MATLAB help.

It says that one of the approaches to model a hollow shaft is to use two Cylinder Solid blocks. By setting the density of one of the two blocks to a negative value, a subtraction will be made and a hollow shaft will be modeled.

I am trying to use this specific approach, however, I don't get a hollow shaft in the Mechanics Explorer. I have attached my Simulink model, Solid blocks properties, resulted model in Mechanics Explorer and the "Compound inertia" help article as pictures. Anyone knows why I don't get a hollow shaft in the Mechanics Explorer?

Thanks in advance.

Answer 1

[Vasco Lenzi]

Hi Muneer

there is a free library on File Exchange that adds lots of parametrized parts to Multibody:

https://www.mathworks.com/matlabcentral/fileexchange/36536-simscape-multibody-parts-library

The simplest thing woul be to add this library and drag and drop the cylinder with hole block. You could take a look at how this was built as well. This library is provided by Steve Miller, our technical marketing manager for Simscape.

You don't see an hollow shaft with the method you posted about because there isn't one: there are two cylinder, one inside the other,so graphically you are going to see two cylinder even if one has negative mass. For the mathematical purpose though, it behaves like a hollow shaft. On the other hand the block in this library will be with a hole graphically.

Screenshot of the library and cylinder block:

[Muneer Wahbah]

Thank you so much for your demonstration. I didn't know about this library. I am appreciated.