Modeling and Sensorless H_∞ Control of Magnetic Bearing with Effect of Eddy Current

摘要

Sensorless control is a method to realize the motion or vibration control without using displace- ment sensors or acceleration sensors which are generally used in the control of mechanical systems. The advantages of applying sensorless control to mechanical systems are cost reduction, prevention of instability of the control system by collocation, downsizing and lightening of the apparatus. In this study, a sensorless control to magnetic bearing system was investigated. Sensorless magnetic bearing control has been already realized by using an observer which is estimating the state of the system using the measured current in the electromagnet. However it is difficult to realize a sensorless control of magnetic bearing system using an observer for such a system with eddy current loss because the modeling of an eddy current loss is so complicated and has not been clarified yet. So, a model of magnetic bearing with the effect of eddy current was identified by curve fit based on least square method, and an output feedback type sensorless control system was designed based on H_∞ control theory. It is clarified through the experiment that the proposed control strategy in this paper is a very useful approach to realize a sensorless control.