In Simscape-M​ultibody-C​ontact-For​ces library is there a Face to Face Contact Force Block?

I am new to Simscape and Multibody contact Forces.

So, I know there is a Face to Plane Contact Force Block, where the plane is assumed to be much larger than the face.

But I need a Face to Face Block, where, in my case, both faces will be identical in size.

Is this available or even possible to create in Simscape?

The simpelest way to look at it is: I need to model two dice sliding on a plane towards each other, where any face on one dice might contact any face on the other die, we can assume at this point that the contacting faces are oriented parallel to each other.

My untimate model would be much more complicated with multiple dodecaherons, rolling at arbitrary angles, but the above will suffice for now.

Any advice would be appreciated.

John

Answer 1

[Steve Miller]

Hi John O,

While the Simscape Multibody Contact Forces library could be used for these types of collisions, a better solution would be to use the Spatial Contact Force block that ships with Simscape Multibody. I recommend you attach a Point Cloud block to each die with points representing each of the corners. Between each pair of dice (die A and die B) place two Spatial Contact Force blocks. One Spatial Contact Force block will connect to the Point Cloud on die A and the exported geometry on die B, the other will connect to the Point Cloud on die B and the exported geometry on die A.

--Steve

[John O]

Steve, thank you.

I will give that a try!

[John O]

Steve, I know it's been a while, but I've started converting over to point cloud.

A few questions.

I get an error when I attempt to use the spacial contact force block:

Caused by: ['POintCloud']: Spatial Contact Force 'POintCloud/Spatial Contact Force5' has physical signals and is connected to a Point Cloud geometry. This configuration is invalid. Disable the physical signals to resolve this issue. Resolve this issue in order to simulate the model.

I need to use those signals, is there a way around this?

In the image below I have done as you suggested, points on each corner. But as you might be able to discern, the edge of the green cube has penetrated the red(and vice versa). Is there anothr solution for this besides a row of points along each edge?

e

Is there any documentation other than the help file? I've haven't found any. All of the searches I've done tend to return graphical point clouds.

And to generate the point cloud coordinat matrix, is there any semi-automated way to generate this, or do I have to write my own script to do this? My "dice" have become much more complicated and will likely become even more so.

~John

[Steve Miller]

Hi John - attached is a function I created to create point clouds for bricks. See if it helps you. If you want to measure the distance between the two solids, you can use another Spatial Contact Force block attached to the solids, but set the stiffness to 0. This won't give you the force, but it will give you the separation distance.

--Steve

[John O]

Thank you Steve, I'm looking at that now.

And just in general, will using point clouds result in a simulation performance improvement over just using the two solid's geometries with a Spatial Contact Force block?

Or maybe a more general question is what is the advantage of the Point Cloud blocks?

I have been experimenting with PCB's in my simulation and it seems to be behaving pretty much the same, Though of course I may not be implementing them optimally!

~John