Active magnetic bearings: A review of design configurations, control approaches, vibration control, and failure modes

Active Magnetic Bearings (AMBs) stand for shaft support means based on controlled electromagnetic forces, which provide non-contact support of rotors. Differing from common rolling and sliding bearings, AMBs exclude mechanical contact between elements of the bearing and, therefore, prevent the rotor from frictional wear and need for lubrication. High-speed performance and controllability of AMBs’ rotor position allow using them in turbomachinery, machine tools, flywheel energy storage systems, compressors, vacuum equipment, and medical devices. This paper gives an overview of basic issues of AMBs: principles of operation, types, designs, design methods, control strategies, vibration behavior, experimental results, and failure modes. Special emphasis is paid to configurations of AMBs with 3, 4, 6, 8 and 12 poles and their impact on system size, power requirements, cross-coupling effect, and dynamic behavior. In accordance with reviewed literature, a crown-type AMB configuration with trapezoidal windings can reduce stator diameter by 13% and 7% for different windings. To ensure vibration control, a three-degree-of-freedom magnetic actuator generates forces up to 248 N in radial direction and 34 N·m torque at frequency of 850 Hz, while speed-independent control increases chatter-free chip width by 63% compared to PID control. Moreover, PID, fuzzy logic, sliding mode, model predictive, and fault-tolerant control strategies and sensor, power amplifier, coil, controller, rotor load, and touchdown bearings’ failures are considered. Thus, the paper analyzes the relations between bearing configuration, electromagnetic design, sensors, controller selection, vibration control, and fault handling, which show vibration reduction, cross-coupling control, power efficiency, and reliability as promising development directions of AMB technology.