CONTROL OF AN ACTIVE MAGNETIC BEARING SYSTEM USING SLIDING MODE TECHNIQUES

ABSTRACT In this paper, stabilization of an Active Magnetic Bearing (AMB) system with varying rotor speed using Sliding Mode Control (SMC) techniques are considered. The gyroscopic effect and imbalance inherited in the system is proportional to rotor speed in which this nonlinearity effect causes high system instability as the rotor speed increases. Also, transformation of the AMB dynamic model into a new class of uncertain system shows that both the gyroscopic effect and the imbalance lie in the mismatched part of the system matrix. SMC design methods based on Linear Matrix Inequality (LMI) and H2 techniques are proposed in which the sufficient condition that guarantees the stability of the reduced-order system is achieved. Then, a chattering-free control law is also established and discussed such that the system states are not only driven to reach the switching surface and to maintain the sliding mode, but also the control effort is reduced. The performance of the controllers applied to the AMB model is demonstrated through simulation works under various system conditions