A novel robust perfect tracking control method for nonlinear servo systems

In this paper, we extend perfect tracking control to nonlinear systems, and propose a novel robust perfect tracking control (RPTC) strategy for nonlinear servo tracking systems. The overall control system consists of four parts: a model-based friction compensator, a feedforward perfect tracking controller, an improved internal model controller as the feedback controller, and a disturbance observer for position feedback. First, the friction compensator is introduced to compensate the nonlinear dynamic friction, and the feedforward perfect tracking controller is applied to widen the frequency band. Then, the internal model controller with a differentiator is adopted to yield improved tracking accuracy. Moreover, by utilizing the disturbance observer, the robustness against external disturbances and plant uncertainties is ensured. Finally, high accuracy tracking and ideal robustness are achieved by the RPTC scheme. The stability of the closed loop system is analyzed. Simulation results demonstrate that the proposed RPTC strategy significantly improves the tracking accuracy and enhances the robustness.