Abstract: Nonlinearity of servo-axis controller is an important factor to influence the performance in the modern CNC system with high velocity and high precision. Aiming at the nonlinearity of axis controlling, fuzzy slide-mode control based on variable structure system establishes the theoretical foundation. However, owing to the coupling effect of the multi-nonlinearity in actual CNC systems, fuzzy slide-mode controller cannot effectively drive the servo-axis. In order to solve the problem, a method is presented, which imports self-tuning technique to fuzzy slide-mode controller. In the method, an adaptive rule is obtained through the simulation, while a self-tuning function is derived from the controlled object. On the basis of the method, a self-tuning fuzzy slide-mode is designed, which not only makes full use of the robustness of fuzzy slide-mode theory, but also tunes the parameter of the controller on-line. The results of simulation on backlash and deadzone show that this controller can improve run-time efficiency and performance. So it pro-vides a good solution to multi-nonlinearity of CNC systems.

Key words: Axis controller, Backlash, CNC, Deadzone, Fuzzy sliding-mode control, Nonlinearity, Self-tuning control