Follow the steps listed below to keep both the Visual (Solid) block for appearance and the Inertia block for accurate dynamics, without causing a "degenerate mass distribution" error:
1. Use a Solid block for visualization only
- In each body subsystem, keep your Solid ("Body Elements → Solid") block connected so the geometry renders correctly in Mechanics Explorer.
- In its block parameters, you can uncheck or ignore the Calculate Inertia from Geometry / Density section, so it does not interfere dynamically.
2. Add an Inertia block next to it for mass properties
- From Body Elements, insert an Inertia block and connect its Frame (R) port to the same reference frame of your Solid block.
- In that block’s dialog:
- Set Type to Custom (if you have a full inertia tensor) or Point Mass (mass-only).
- Provide the mass and inertia values.
- For Marker, choose None—this suppresses the icon or ellipsoid in the visual output, preventing visual clutter while still contributing dynamically. To read more about “Inertia” block, refer the link given here: www.mathworks.com/help/sm/ref/inertia.html
The underlying mechanics are designed for compounding: you can layer solids (for visualization) and separate inertia blocks (for dynamics) on the same reference frame. By setting the Inertia block's Marker to None, you effectively say: "Use only the visual Solid, but still include the mass/inertia in the physics."
This approach ensures:
- No degenerate mass error (since you are not duplicating or mis-specified inertias).
- Clean visuals in Mechanics Explorer with just the Solid block shown.
- Accurate dynamics, as mass and inertia come exclusively from the Inertia block.
Refer the following documentation pages posted by MathWorks for more detailed info:
- Representing Solid Inertia: www.mathworks.com/help/sm/ug/specifying-solid-inertia.html
- Modeling Bodies: www.mathworks.com/help/sm/ug/simmechanics-bodies.html
- Specifying variable inertias: www.mathworks.com/help/sm/ug/model-a-body-with-variable-mass.html
Hope this helps!
