Hybrid Fuzzy Decoupling Control for a Precision Maglev Motion System

This paper presents a hybrid fuzzy decoupling control strategy, and its implementation for leveling and positioning a maglev wafer carrier in an integrated circuit (IC) packaging application. The maglev platform possesses micron scale positioning and can carry the wafers with precision motion between workstations. Because the maglev system is open-loop unstable, there are strong nonlinear interactions between electromagnets and the exact nonlinear system model is unknown, it is hard to achieve a good decoupling control performance by using conventional control strategy. Therefore, in this paper, a hybrid fuzzy decoupling control with good decoupling performance is proposed. The decoupling control uses a master–slave structure, which consists of a linear master decoupling control term and a nonlinear slave intelligent compensation term. The master decoupling term decouples the main interactions of the coupled maglev system. Using the decoupled main system as reference, the slave intelligent term compensates the nonlinear interactions. Furthermore, for this control strategy, establishing the exact linear or nonlinear model is not necessary, only an approximated linear model is needed. The experimental results show that the proposed control strategy decouples most of the interactions between the electromagnetic actuators. Experimental comparisons also highlight that the master–slave decoupling control has shorter settling time and smaller steady-state error than a conventional adaptive fuzzy controller and proportional-integral-differential controller.