How to simulate friction between a cable and an object？

[3H2Oaaa]

Hello，everyone！

I am working on a simulation of a cable-driven soft robot, where the cables are embedded within the soft body. Therefore, there will inevitably be friction between the cables and the robot. However, I currently do not know how to simulate this frictional interaction.

Thank you for your reply！

[3H2Oaaa]

I am currently using the CableConstraint component to simulate cable actuation. However, I am unsure if it is possible to use this component to simulate the friction between the cable and the soft robot.

[hugtalbot]

Hi @3H2Oaaa
Interesting, as far as I know, friction is not modeled in the cable actuation, correct @bakpaul @EulalieCoevoet ?

[3H2Oaaa]

Hi @hugtalbot
Thank you for your reply. By the way，Is there any alternative approach to implement this functionality in SOFA?

[EulalieCoevoet]

Hi @3H2Oaaa, @hugtalbot,

Indeed, you cannot model friction between the cable and the robot with the CableConstraint component.
Implementing this feature shouldn't be too complicated on the C++ side; we know the contact points (passing points of the cable in the robot), and we know the direction of the friction force. I think this problem is easy to solve. But I'm pretty sure it hasn't been added to the SoftRobots plugin yet.

For an alternative approach I haven't tried: you could model your cable using the Cosserat plugin, then

1. Add a collision model to your cable using the LineCollisionModel component
2. Add a collision model to the passing locations of your cable in the robot—I'd use circles, for instance
3. And finally add the required components to detect and solve friction contact in your scene

This approach is computationally very expensive though.

[3H2Oaaa]

Hi， @EulalieCoevoet
Thanks for the reply. I’m new to SOFA and still getting familiar with some of the components, so your answer was really helpful.