Modeling and system identification of active magnetic bearing systems

Active magnetic bearing (AMB) systems have drawn much attention in the rotating machinery industry due to their advantages over conventional bearings such as fluid film and rolling element bearings. The AMB control system must provide robust performance over a wide range of machine operating conditions and over the machine lifetime in order to make this technology commercially viable. An accurate plant model for AMB systems is essential for aggressive design of control systems. In this paper, we propose two approaches to obtain accurate AMB plant models for the purpose of control design: physical modeling and system identification. The former derives a model based upon the underlying physical principles. On the hand, the latter uses input-output data without explicitly resorting to the physical principles. For each problem, a brief summary of the theoretical derivation and assumptions is given. Experimental results based on data collected from an AMB test facility at United Technologies Research Center provides a vehicle to compare two approaches.