Dynamics

Direction of torque and friction

The sign of applied joint torques matches the direction of increasing angle. That is, a positive joint torque, would increase the joint angle through positive joint velocity and acceleration.

Friction as computed by the link Link.friction(q) method should be added to the motor output torque to determine the nett torque. It implements a viscous + Coulomb friction model that opposes the motor torque. For positive motor velocity the result will be negative.