Simscape R2020a multibody block "spatial contact force" does not work properly for the contact of a hollow cylinder with its piston!

1. Why does the simscape R2020a multibody block with "spatial contact force" not work properly for the contact of a hollow cylinder with its piston for an internal combustion engine?
2. Why is the separation distance a scalar? There is no help to center better the solids!
3. When the Frictional force is set to "none" is a friction torque allready present, why?
4. How does the "normal force magnitude" work? Especially when frictional force is set to none?
5. Only if the spacial contact force blocks are "commented out" have no influence on simulation results.

Thank you for your help!

[Victor Gheorghiu]

Hi Steve, thank you very much for your answer! I will check everything, use your indications and get back to you later. Victor

Answer 1

[Steve Miller]

Hi Victor:

1. Why does the simscape R2020a multibody block with "spatial contact force" not work properly for the contact of a hollow cylinder with its piston for an internal combustion engine?

The Spatial Contact Force block through MATLAB release R2021a treats every solid as a convex hull.

2. Why is the separation distance a scalar? There is no help to center better the solids!

The separation distance is the minimum distance between the two solids. If you want x-y-z distance between the reference frames, you can use a Transform Sensor

3. When the Frictional force is set to "none" is a friction torque allready present, why?

If Frictional Force is set to "none", no friction force is applied between the bodies.

4. How does the "normal force magnitude" work? Especially when frictional force is set to none?

"Normal force magnitude" is the magnitude of the collision force applied at the point of contact, which is normal to the surface at that point. Frictional force would be parallel to the surface and would have no effect on the normal force calculation

5. Only if the spacial contact force blocks are "commented out" have no influence on simulation results.

The Spatial Contact Force blocks will have no influence on the simulation results if the bodies do not touch each other.

--Steve