ROBUST MOTION CONTROLLER-DESIGN FOR HIGH-ACCURACY POSITIONING SYSTEMS

This paper presents a controller structure for robust high-speed/high- accuracy motion control systems, The overall control system consists o f four elements: a friction compensator, a disturbance observer for th e velocity loop, a position loop feedback controller, and a feedforwar d controller acting on the desired output. A parameter estimation tech nique coupled with friction compensation is used as the first step in the design process. The friction compensator is based on the experimen tal friction model and it compensates for unmodeled nonlinear friction , Stability of the closed-loop is provided by the feedback controller, The robust feedback controller based on the disturbance observer comp ensates for external disturbances and plant uncertainties, Precise tra cking is achieved by the zero phase error tracking controller, Experim ental results are presented to demonstrate performance improvement obt ained by each element in the proposed robust control structure.