Disturbance-observer-based control of a 6-DOF magnetic levitation table with an optimal distribution of electromagnetic forces

Based on optimization techniques and sliding-mode disturbance observers, this paper presents a controller design for a six-degree-of-freedom table magnetically levitated by attractive forces. Due to the commonly-used structure of four-point attraction, the levitation system has one subsystem with four independent inputs and three independent outputs. By making use of the control redundancy in this subsystem, an optimal distribution of electromagnetic forces is designed to both minimize the energy loss and also to diminish the possible problem of actuator saturation. To yield a robust levitation system, this paper presents a sliding-mode disturbance observer that estimates system perturbation and generates minimal control to govern system dynamics to a desired one. The feasibility of the proposed scheme is demonstrated through computer simulation.