Feedback Control of a Magnetic Bearing Using Fusion of Rotor Acceleration and Position Measurements

This paper considers controlling a magnetic bearing using combined feedback of rotor acceleration and position measurements. A controller design based on sensor fusion via complementary filtering is described. The control method can maintain stability while allowing the cross-over frequency for the acceleration and position feedback loops to be set arbitrarily. In this way, position measurements can be utilized primarily for disturbance cancellation over a low frequency band while acceleration feedback maintains bearing stability and disturbance rejection over a higher frequency band. The approach has the advantage that it gives enhanced robustness to poor quality position measurements. For flexible rotors, stabilization with large axial separation of position sensors and bearing locations can be easily achieved by utilizing collocated rotor-embedded accelerometers. The approach also offers improved robustness to measurement noise, position sensor run-out error and other forms of physical contamination or damage. Through analysis and simulation, important physical effects on vibration control performance are identified and further considered within the design methodology.