Nonlinear control of an active magnetic bearing with bias currents: experimental study

This paper presents an experimental comparison of position tracking controllers for a five degree-of-freedom active magnetic bearing system. Two variations of a nonlinear design are presented, each subject to a different actuating constraint: constant current sum (CCS) uses bias currents and current almost complementary (CAC) avoids bias currents. While both designs achieve accurate tracking for a non-rotating shaft, a comparison of unbalance responses show that voltage saturation can limit the dynamic response of the CAC-based design. Performance of the nonlinear designs is also compared to a decentralized PID controller