Levitation Control for a Double-Sided Bearingless Linear Motor Based on Feedback Linearization

Abstract

This paper deals with levitation control for a doublesided bearingless linear-motor system. Analytical design rules for a state-feedback gain and a state observer are derived. To decouple the production of forces in thrust-and normal-force directions, feedback-linearizing control based on the magnetic model is proposed. The proposed control design is tested in an experimental system consisting of four individually supplied linear-motor units in a double-sided configuration. The results from time-domain simulations and experimental tests suggest that the proposed control design can successfully provide smooth transition to contactless operation and retain the stable levitation during the movement in the thrust-force direction.

A Dynamic Model for Bearingless Flux-Switching Permanent-Magnet Linear Machines

“…A magnetically levitating drive system may consist of bearingless FSPM linear machine units [11], [15]. The machine units can be arranged in various ways.…”

“…Furthermore, we present new FEM and experimental results. It is also to be noted that a control system based on the developed model as well as experimental results of levitation and propulsion tests were recently presented in [15].…”

“…It is worth noticing that the equivalent MMF i m has an effect on both the total field energy W in (15) and the field energy term w 0 in (16). The analytical expression for the normal force can be calculated using (13) and (15). However, the force expression becomes very long in the case of rational functions.…”

“…Alternatively, they could be approximated by means of a magnetic equivalent circuit, whose reluctances are calculated using the geometry. Applying (13), (15), and (18), the normal force expression becomes…”

“…where the field energy function w 0 at ψ d = ψ q = 0 generally differs from the magnetically linear case, cf. (15). However, for simplicity, we assume w 0 equal to the linear case.…”