Minimization of Power Losses in Active Magnetic Bearing Control

Acknowledgments My special thank goes to my advisor Dr. Marcio S. de Queiroz. I thank him for all his continued support in all stages of this project. I would also like to extend my sincere gratitude to my committee members Dr. Kemin Zhou and Dr. Yitshak Ram for their valuable support and guidance. Abstract A solution to the problem of AMB control with reduced electrical power losses will be presented in this thesis. The proposed control solution will be founded on the integrator backstepping technique, which decouples the rotor stabilization problem from the bias flux design problem. It further allows for the easy redesign of the control law to compensate for uncertainties in the AMB system. A class of nonlinear controllers will be developed that reduces the AMB power losses in comparison to standard fixed-bias controllers, while containing no control singularity. Control laws will be presented for the standard AMB operating mode where both electromagnets are active at all times, as well as for the " energy-saving " operating mode where only a single electromagnet is active at any given time. The main contribution of this work is the development of a smart bias flux, and function of the rotor position and velocity. General conditions motivated by physical and mathematical properties are developed for the functional form of the bias, ensuring the reduction of power losses and the avoidance control singularities without affecting the closed-loop system stability. Simulation results also illustrate the interesting role the smart bias plays in stabilizing the rotor. Note that while the power loss discussion in this thesis is focused on ohmic losses, the proposed control strategies also help reduce eddy current-and hysteresis-induced losses due to their proportionality to the magnetic flux.