Observer-Based Contouring Controller Design of a Biaxial Stage System Subject to Friction

Friction is a major source of disturbances for common stage systems. For the purpose of high precision contouring performance, both contouring control and friction compensation are necessary. Hence, this brief studies the contouring controller design problem of a biaxial stage system subject to friction. Moreover, to cope with the real situation happening in most stage systems, position is assumed to be the only available information for design. By incorporating a friction model into system dynamics and with the help of the task coordinate formulation, an observer-based contouring controller is proposed to solve this problem. Based on the results of state observation, friction forces can be well estimated and compensated. The resulted contouring controller possesses an integrated structure such that the feedforward, feedback, contouring, and friction compensation controls can be synthesized in a systematic manner. Simulation and experimental results are consistent to the theoretical analyses and verify the proposed scheme.