Orbit Motion Tracking Control for Rotating Machine With Magnetic Suspensions

Conventional use of active magnetic bearings (AMB) focuses on keeping a rotor centered at the zero reference. In this research, a control algorithm is developed for an alternate task of tracking high-bandwidth sinusoidal targets: whirling and conical motions. To increase robustness to the parametric uncertainty and the nonlinearity of inherent AMB dynamics, the sliding mode control is developed based on an original nonlinear AMB model with an uncertain magnetic force constant. Performance indices, such as the I²R power loss, the tracking error and the phase lag, are compared for the two target motions, and they are also utilized to find an optimal bias current of the actuators. Simulation results show that the rotor follows the two high-bandwidth large motion targets with low tracking error and phase lag in the presence of parametric uncertainty. Orbit motion tracking control has a variety of potential applications in rotating machinery such as active rotating stall control, in which seal clearance is required to follow a sinusoidal dynamic motion.