Adaptive auto-balancing control of magnetic bearings for an optical chopper

We show how adaptive notch filters and magnetic bearings can be utilized for auto-balancing of an optical chopper. This optical chopper is required. to operate between 4800 and 5200 RPM (rotations per minute) for five years in space. Life testing of the ball bearings in the optical chopper has indicated potential failure of the bearings after three to four years due to lubrication break down. The goal of this research is to investigate the feasibility of replacing the ball bearings with magnetic bearings. By using magnetic bearings to suspend the optical chopper, friction between the bearings and the rotor, and associated failures, can be eliminated. Initial testing using standard feedback controllers, however, showed excessive wobble in the chopper due to mechanical imbalances. By using adaptive notch filters based on the LMS (least mean squares) algorithm, we show how this wobble can be significantly attenuated. Experimental results are presented.