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Is it possible to model a ball and wheel system using SimMechanics?

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Manuel
Manuel on 17 Dec 2013
Answered: Steve Miller on 25 Jun 2021
I would like to model a Ball and Wheel system in order to allow my students to be able to design PID controllers to control such a system (control the wheel position/velocity in order for the ball to remain in the top of the wheel). In case the controller is not able to control the system correctly, then the ball should roll along the wheel until a position on which the ball will leave the wheel and fall to the ground.
My question is the following: is it possible to simulate this system using SimMechanics?
I have studied the SimMechanics documentation and I was considering modeling the wheel as a cylinder, the ball as a sphere and then define the contact among them as a SimMechanics “Point-Curve Constraint” block, on which the curve spline would represent the external surface of the wheel.
Can this be done? Is this the correct way simulating this type of contact among bodies?
Thanks for your help.

Answers (1)

Steve Miller
Steve Miller on 25 Jun 2021
You can do this in Simscape Multibody in a couple of ways.
  1. If you can assume that the ball will not slip, you could connect the two using a Common Gear Constraint. Once the ball leaves the wheel, the system has failed (since the controller cannot recover), so this assumption is probably OK for the conditions you care about.
  2. If you want the ball to slip, you could use the Spatial Contact Force block, which will model the normal force and friction force bewteen the ball and the wheel. This would allow it to slip and fall off.
--Steve

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