Nonlinear Controller Design of Three Degree-of-Freedom Hybrid Magnetic Levitation Control Based on Fuzzy Model for a Contactless Servo-Actuator

This paper presents a nonlinear servo-control design based on Fuzzy model for safer and comfortable levitation of an electromagnetic suspension stage consisting of triple arrangement of hybrid electromagnets, since conventional linear control design can give satisfactory results only around a specified linearization point for tiny displacements. The authors have proposed compensation principle for a proper control action according to change of operational points through fuzzy inference algorithm. Fuzzy reasoning acts as a gain scheduler among approximate local linear controllers derived from various gap operating points. The authors integrate a zero-order disturbance observer for estimating gap velocity and winding currents, as well as for improving performance of the system under external load-force changes. The effectiveness of the proposed control methodology is verified through several experiments. Keywords— fuzzy model-based control, hybrid electromagnet, servo control, magnetic levitation, magnetic suspension