# Simscape modeling of bristle roller

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Saravanan Arumugam on 10 Mar 2022
Answered: Steve Miller on 24 Nov 2022
I am trying to model a Bristle roller in Simscape. As per the penalty based method to find the stiffness and damping values for the bodies to simulate, I have found using the formula for solid objects. But how to model the object like bristles which deform or bend when come into contact, what is the best approach for this. I know the physical property - stiffness of the bristles. How to relate the physical stiffenss value with the stiffness and damping values for spatial contact force block.
The spiral part of the object is the bristles which come into contact with the floor.
Thanks
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### Answers (1)

Steve Miller on 24 Nov 2022
Interesting question! It depends how much detail you want.
1. Abstract: If your roller is spinning quickly and you are simply going to treat the bristles as an extra mechanical load on the motor that is only active when the roller is spinning and touching the floor, you could use the Spatial Contact Force block (or a Transform Sensor) to measure the distance to the floor, and when it gets close enough apply a resistance torque to the joint holding the roller that is dependent on the roller speed. You could have the damping vary with angular position to give it some sort of cyclic behavior.
2. Detailed: You could model some/many of the bristles as independent bodies with a revolute joint where the bristle attaches to the roller (with a spring damper) and a spatial contact force at the tip to model collision with the floor. Setting those values will take some trial and error.
I think if you can measure the change in current draw of the motor as the roller strikes the ground, you would have a good basis for adjusting the parameters these two models of the physics you are trying to represent.
--Steve
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