Control System for Inside-Out Configuration Magnetic Bearings

Abstract

The University of Texas Center for Electromechanics (UT-CEM) in association with the Texas A&M Vibration Control Lab (TAMU-VCL) has developed an active magnetic bearing control system for use in a 5 MW, 25 MJ, 20,000 RPM flywheel alternator developed under the Combat Hybrid Power Systems (CHPS) program. The inside-out topology of this flywheel (i.e., the 650 lb (294 kg) flywheel rotor is positioned outside the stator) was dictated by the extreme power density and energy density requirements, and presented unique control challenges seldom encountered in conventional magnetic bearing applications. These challenges resulted from a large number of flexible modes in the rotor and stator, requiring a high-order flexible dynamic model and extensive rotordynamic analysis. A simulation-based design effort was implemented to accomplish the primary control objective: to provide robust, efficient magnetic levitation of the CHPS rotor over a wide range of operating speeds and disturbance inputs, while minimizing the occurrence of backup bearing touchdowns. Additionally, this design effort provided critical specifications for CHPS flywheel design and component selection. Details of the CHPS magnetic bearing design, prototyping, and testing are presented in a companion paper “Inside-Out Configuration Active Magnetic Bearing Actuators”.