Robust Adaptive Control for Robot Manipulators with Friction

A composite tracking control scheme, consisting of an adaptive friction estimation and a robust controller, is proposed for a robot manipulator to achieve a tracking control objective under the influence of unknown friction and uncertainty. The adaptive friction estimation is used to estimate the extent of friction, which includes Coulomb friction, viscous friction and the Stribeck effect, and then a robust controller is designed to enhance the overall stability and robustness. It is shown that the design of the friction estimator and the design of the robust control gain can be conducted separately. The effect of the robust adaptive friction controller is verified by the simulation results for a two-degree-of-freedom planar robot manipulator.