Nonlinear dynamic characteristics analysis of active magnetic bearing system based on cell mapping method with a case study

Active magnetic bearings (AMBs) are widely applied in high-speed rotating machinery, especially those in special environments. In the designing and adjusting an AMB system, the mathematical model of the system plays an important role. An AMB system is essentially nonlinear, thus the widely applied linear model cannot fully reflect the system characteristics in some cases. Cell mapping (CM) method is a global analysis method for nonlinear dynamic systems, which can obtain the global structure of a nonlinear system and the influences of varying parameters on it. In this paper, a CM type method is applied to analyze the nonlinear characteristics of the AMB system. Operational data from an actual AMB system is analyzed. During the on-site commissioning experiment, this system was unstable under specific conditions and was stabilized after modifying the controller. Analysis based on CM method reveals that the main cause of the instability is the bifurcation due to the nonlinearity of the system and the on-site treatment was valid.