Controllability and observability in flexible rotor-magnetic bearing systems.

Abstract

This paper is concerned with controllability and observability for a flexible rotor system supported by active magnetic bearings. The criterion of two steps concerning controllablity and observability is proposed based on the concept that a control system of magnetic bearings consists of position feedback and velocity feedback in general. The first step of the criterion is for a position feedback and the second step is for velocity feedback. The first step is to check free-free modes for only flexible rotors. In the second step, flexible modes including position feedback loops have to be analyzed because free-free modes are varied by position feedback gains. We can explain and make clear the experimental vibration behaviors which are very stable until just before the fourth critical speed, become unstable in passing through the fourth critical speed and then become stable again.