Is there any way to apply static and dynamic friction to passive revolute joint in simscape multibody?

Greetings,

I have a technical question regarding friction and passive joints.

I know that we can apply the Coulomb and Viscous Friction to active joint in torque control mode. However, now I need to apply the Coulomb and Viscous Friction to a passsive revolute joint. So is there any advice?

Thanks in advance.

Answer 1

[Vidip Jain]

I understand you want to apply the Coulomb and Viscous Friction to a passive revolute joint.

Passive joints rely on external forces or torques to move, and you can model friction effects using various approaches. Here's how you can simulate Coulomb and Viscous friction on a passive revolute joint in Simulink:

1. Model the Passive Joint: Ensure that your passive revolute joint is properly modelled in your Simulink model. You might have already defined it using a block like a Revolute Joint block from Simscape Multibody, which inherently represents a passive joint.
2. External Torque Input: To apply Coulomb and Viscous friction, you'll need to provide an external torque input to the passive joint. This external torque represents the forces acting on the passive joint due to friction.
3. Modelling Coulomb Friction: Coulomb friction is typically modelled as a step function that opposes the motion of the joint once a certain torque threshold is reached. You can use a Step block in Simulink to simulate Coulomb friction. When the joint's velocity (angular velocity in the case of a revolute joint) exceeds a certain threshold, you can apply a step input to the joint to simulate Coulomb friction.
4. Modelling Viscous Friction: Viscous friction opposes the motion of the joint in proportion to its velocity. In Simulink, you can apply a damping term to the joint to simulate viscous friction. You can use a Gain block with a negative value to represent viscous friction, and the magnitude of the negative gain represents the damping coefficient.

Refer to this documentation for more information:

• https://www.mathworks.com/help/sm/ref/simscape.multibody.revolutejoint-class.html
• https://www.mathworks.com/help/simulink/slref/coulombandviscousfriction.html