Study of Electromagnetic Suspension System Using Acceleration Signal of Electromagnet Supported with Spring

Abstract

The authors propose a novel control scheme for an electromagnetic suspension system. The excitation current of an electromagnet is usually controlled using feedback gap sensor signals. An acceleration sensor signal is used in the proposed scheme, where the gap acceleration, integrated acceleration, and excitation current are considered as the state variables. The following three points should be noted: (1). the electromagnet is movable and supported by a spring-damper, because the acceleration sensor should not be attached to the controlled object; (2). the speed signal is stabilized by the integration of the acceleration; and (3). the observer is used to estimate the speed as a countermeasure of the integration drift problem. The authors show the state equation of the proposed scheme and the consequent controllability and observability; they then report the evaluation of the system using the experimental apparatus, as well as present the vibration characteristics of the controlled object.