A scheme for estimating joint friction using a model-based controller

A real-time estimation scheme for directly estimating the frictional forces and torques of the joints in a robotic manipulator (in contrast to estimating frictional model parameters) is presented. The estimated frictional force/torques can then be incorporated into the nonlinear compensation of the computed-torque control method. This provides the capability of eliminating unstable motion at low velocity, primarily caused by improper compensation for joint friction. The scheme requires two stages: simultaneous extraction and adaptive linear filtering. The derivation is basically heuristic