用自校正模糊滑动控制器解决数控系统中的非线性问题

随着数控系统向高速、高精度方向发展,伺服轴的非线性特性已成为影响控制器性能的重要因素。针对控制系统中的非线性问题,基于变结构的模糊滑动控制奠定了解决问题的理论基础。然而,在实际的轴控制中,由于多种非线性间的耦合效应,单纯采用模糊滑动控制存在着相应的问题。为了消除非线性特性间影响,探讨了将自校正控制引入模糊滑动控制的方法。通过仿真试验,建立了模糊滑动控制的自适应律;根据轴控制对象,设计了自校正环节的控制函数,建立了一种自校正模糊滑动控制器。该控制器不仅可利用模糊滑动控制的鲁棒特性,而且可在线调节控制器的参数。针对反向间隙与死区的仿真试验表明,自校正模糊滑动控制器执行效率更高,误差更小,可以很好地解决数控系统轴控制器中存在的非线性问题。

SOLUTION TO NONLINEARITY OF CNC BASED ON SELF-TUNING FUZZY SLIDE-MODE CONTROLLER

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 nonlinear-ity 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 provides a good solution to multi-nonlinearity of CNC systems.