Automatic Initial Levitation with Active Magnetic Bearings

Active magnetic bearings (AMBs) require a feedback controller for stable operation. This paper describes a procedure which allows for fully automated initial levitation with no knowledge about the AMB system. Combined with some adaptive or self-tuning techniques, bearings could be setup automatically with minimal human interaction, without calibration or tuning. Based on the ideal and linearized model of a single mass one degree of freedom levitated body, the criterion for a stable suspension is reviewed. A step-by-step description outlines how the needed parameters are found which lead to a stabilizing controller. A more general, hybrid model including sensor and amplifier dynamics as well as a discrete-time PID controller is used to compare the regions of stabilizing control parameters to the ideal case. The presentation of experimental data and a discussion conclude this paper.