Proposal on nonlinear friction compensation based on variable natural length spring model

Ball-screw-driven stages are used for industrial equipments such as machine tools and exposure systems. Fast and precise positioning is necessary to enhance productivity and microfabrication technology of the system. Authorspsila research group has improved the positioning performance of the stage by using perfect tracking control (PTC). However, when modeling error occurs, the positioning performance of the stage is greatly degraded. Most of the modeling errors are rolling friction of the stage. Therefore, the control system based on the friction model is necessary. In this paper, we propose variable natural length spring model (VNLS-model) as the friction model. VNLS-model is simple and easy to implement as friction controller. Moreover, the control system based on VNLS-model is proposed. Finally, the simulations and experiments show that the advantages of the proposed method.