Active Magnetic Bearing Control with Zero Steady-State Power Loss

In this paper, we address the problem of controlling an active magnetic bearing with reduced ohmic power losses. A solution is proposed which introduces an exponentially decaying bias ßux in the nonlinear control law. To avoid control singularities, the closed-loop system is exponentially stabilized at a faster rate than the bias decay. In the steady state, the proposed controller has zero bias ßux; hence, there are no ohmic power losses. The control scheme is applied to two different bearing modes of operation – all electromagnets active at all times and only one opposing electromagnet active at any given time. A rigorous analysis of the latter mode of operation is presented along with an implementation strategy. Simulations are provided to illustrate the performance of the proposed controller for the two operating modes in comparison to a standard constant-bias controller.