Stability Consideration of Magnetic Suspension in Two-Axis Actively Positioned Bearingless Motor With Collocation Problem

This paper presents a comprehensive stabilization technique for a two-axis actively regulated bearingless motor. Two-axis actively regulated bearingless motors have the advantages of low cost and compactness; however, only two degrees of freedom are actively regulated in the radial x - y directions, thus a tilting motion sometimes causes serious interference resulting to instability. The interference occurs in non-collocated structure. In this paper, novel mathematical analysis is carried out and a block diagram including the interference is presented. It is also shown that stable suspension can be successfully realized by means of adjustments of an integral gain. The analytical results are evaluated by the experiments.