Application of decoupling fuzzy sliding mode control with active disturbance rejection for MIMO magnetic levitation system

Magnetic levitation techniques have been used to eliminate friction due to mechanical contact, decrease the maintaining cost and achieve high-precision positioning. Although there are many studies on the single degree-of-freedom magnetic levitation control algorithms, it is difficult to achieve excellent control performance using classical control methods for the multiple-in-multiple-out magnetic levitation system because of the coupling in the dynamic system and the nonlinearity of the electromagnetic force. This article presents a 3 degrees-of-freedom magnetic suspension stage. At first the dynamic model of the stage is derived; then a nonlinear intelligent decoupling controller is developed to stabilize the levitation system. The control architecture consists of three components: (1) fuzzy sliding mode technique for the uncertainty in the system parameter; (2) force distribution for decoupling; (3) extended state observer for compensating the system disturbance. Finally experiments are designed to verify the effectiveness of the proposed controller. Experimental results show that compared with the classical proportional–integral–derivative controller, the proposed controller provides excellent transient response performance and the system is robust against the parameter uncertainty and external disturbance.