Comparative study of power minimizing control algorithms for active magnetic bearings

This paper describes a comparative study of power minimizing control algorithms for active magnetic bearing (AMB) systems. Active magnetic bearings usually employ bias currents in order to linearize the nonlinear force-current relationship. Although these bias currents guarantee certain amount of dynamic performance, ohmic losses due to the bias currents are a major source of power consumption in a magnetic bearing system. There have been efforts to reduce or eliminate the bias currents while satisfying the requirements. However, these power minimizing algorithms have never been compared against each other under same conditions. In this paper, we compare the two of the existing power minimizing algorithms with a proportional-derivative (PD) type controller which is a de facto controller for magnetic bearings. Also, a PD controller with synchronous notch filter is compared with the power minimizing controllers in a attempt to appraise the performance of these controllers as well as the power saving.