Abstract:

In order to eliminate the friction between moving beam and guide rail in gantry CNC machine, two suspension systems were adopted to suspend the moving beam jointly, so there were coupling relation between two suspension systems. When the beam suffering unbalance force or external disturbance as the CNC machine working, the existing coupling relationship would influence the two suspension system's air gap, so the machining accuracy of compent was reduced. This paper analysed and concluded the coupling quantitative relationship when beam rolling around the center of mass and moving up and down.In order to eliminate the influence of coupling this paper adopted SVM to approach the two coupling suspension systems's α order inverse system. The obtained α order inverse system in series to coupling systems will be decoupled to two SISO pseudo linear systems.The decoupled SISO system adopted time-varying sliding mode control method. The method can make the system reach to the sliding mode surface directly at any original state, eliminating the process of original state reach to the sliding mode surface. So the sliding control can be achieved using shortest time and can realize global robustness of parameter perturbation and external disturbance. The simulation results show that the proposed method can decouple the coupling system effectively and can approach to the controlled object's α order inverse system without precise mathematical model. The time-varying sliding mode control method has fast response speed and strong robustness ability.

Key words: &alpha, order inverse system, decoupling, support vector machine(SVM), time-varying sliding mode

摘要：

龙门数控加工中心移动机械横梁可采用双电磁悬浮系统共同悬浮来消除摩擦的影响，而这两个电磁悬浮系统存在着一定的耦合关系。当数控机床工作时，由于受力不平衡或者扰动等因素影响，这种耦合的存在会使两个电磁悬浮系统的悬浮气隙受到影响，并降低加工精度。分析得出了横梁发生绕质心旋转和上下平移时两个电磁悬浮系统的耦合定量关系，为了消除耦合的影响，采用支持向量机逼近双电磁悬浮系统的α阶逆系统，将所得到的α阶逆系统串联在原系统前构成伪线性复合系统，从而将原系统解耦成两个独立的SISO伪线性系统。针对解耦后的伪线性SISO系统设计了时变滑模变结构控制器，可使系统在任意初始状态下系统状态变量都能直接到达系统的滑模面上，消除了状态变量到达滑模面的过程，以最短的时间实现了滑模变结构控制，实现了对参数摄动和外部干扰的全局鲁棒性。仿真实验结果表明，该方案不需要被控对象精确的数学模型即可采用支持向量机逼近被控系统的α阶逆系统，可有效地对耦合的悬浮系统实现解耦。解耦后的SISO伪线性系统采用时变滑模变结构控制具有响应速度快和鲁棒性强等特点。

关键词: &alpha, 阶逆系统；解耦；支持向量机；时变滑模变结构