Adaptive Friction Compensation for Tracking Control With Position Error Constraints of Servo Control Systems: A Switched System Point of View

ABSTRACT

This paper will investigate the adaptive backstepping friction compensator for a class of servo control systems from a switched system point of view. Firstly, by introducing a convergence‐invariant unbounded transformation, the position error bounds are incorporated into the original system. Secondly, an integral term is introduced to increase the robustness and the ‐backstepping technique is utilized to deal with the sign‐indefinite term. Then, an adaptive controller with a Coulomb friction estimator is obtained and the generated closed‐loop error system has the upper block‐triangle structure, which can be treated as a pair of cascade‐connected systems. Further, the common Lyapunov function (CLF) is obtained. The objects of asymptotical tracking with position error constraints and identification of the Coulomb friction coefficient can be realized. By similar methods, we propose adaptive friction compensators for the viscous friction model and the Coulomb & viscous model. Finally, the simulation results demonstrate the advantages of the proposed methods.