Simscape - Sphere to Plane Force Enabled Block Input

Hi everyone,

I am having trouble with the 'Sphere to Plane Force Enabled'-block from the Simscape Multibody Contact Forces Library. I was looking for a contact model block which I can switch on or off as I need it to and figured that this one looked alike. Sadly I could not find a description of how to use this block properly, especially not about the required input. Please see the attached screenshots for clarification of my questions:

In the first layer under the mask, one can see that there are two input ports labeled as '1'. As I understand it, the top middle one is a switch to activate the contact force calculation. The one on the left enters the sensing block and is supposed to contain signals 'vx' and 'vy'.

1) First of all, is this the right block for my purpose?

2) Why are there two input ports with the same number? How is this even possible? The block has only one input port on the top level (first screenshot). When I expand the subsystem and wrap it up again, it shows two inputs as expected and the ports are labeled '1' and '2'. I honestly do not know what to do with this second input port or the 'vx' 'vy' signals it demands for. I am familiar with the 'Sphere to Plane Force'-block, but I can't figure out this one.

Please feel free to share your experience.

Answer 1

[Steve Miller]

Hi David,

The contact force can be enabled or disabled using the input signal as you have identified.

The input signal must be a Simulink Bus.

• Signal "Enable" should be 1 if you want the force calculated and applied ("enabled"), 0 if not
• Signals "vx" and "vy" can be used to override the relative velocity at the contact patch. This is used to model conveyor belts. By specifying the relative velocity of the parts as a signal, it models the effect that the outer surface is moving, even if the solid is staying still.

The double appearance of the Inport 1 is done using "Duplicate Inport". It is used route the same input signal to multiple locations without making a bunch of line crossings. Goto/From would have accomplished the same thing, but requires 2 additional blocks.

You can see this block used in example Gripper_2Belts.slx

Hope this helps!

--Steve