Robust control of a linear actuator with nonlinear dynamic friction and unknown width input dead-zone

This investigation mainly deals with positioning operation of the electric servo system and an adaptive sliding-mode-based controller via the output feedback scheme is derived for the servo actuator in the presence of the unknown model, nonlinear input, dynamic nonlinear friction and disturbances. The designed controller based on sliding-mode approach includes a LuGre model-based friction state estimator that ensures the cancelation of the friction, and a set of model parameter estimation algorithms for the servo actuator, which are derived in the sense of Lyapunov stability theorem. In addition, in response to uncertainties and disturbances with model or not in practical applications, especially for the unknown bounded ones, the adaptive law is presented to guarantee the system's robustness. Also, the chattering problem in sliding-mode control is confronted based on the fuzzy logic. In the end, the simulation examples under the continuous trajectory commands verify the robustness and performance of the proposed control strategy.