Adaptive friction compensation based on the Lyapunov scheme

A simple method for constructing a nonlinear estimator for adaptive friction compensation is developed. The design is based on the Lyapunov technique and an attempt is made to compensate for frictional force by estimating the unknown Coulomb friction coefficient. The contribution of this paper is to provide a systematic procedure for selecting a nonlinear function in the estimator. It is shown that asymptotic stability of the error dynamics is guaranteed without imposing a constraint on the velocity. Simulation results confirm the advantages of the proposed method for a single-mass nonlinear system as well as a complicated nonlinear system such as a two-link planar rigid robot manipulator.