Torque ripple adaptive rejection in brushless motors

A known problem with brushless permanent magnet AC motors is that parasitic pulsations generally affect the torque. A compact model of the pulsating torque has been recently proposed by the authors (1998), together with simple laboratory identification experiments. In this paper the identification methodology is first extended to cope with variable speed motion. Then, recognizing the time varying nature of the torque disturbance, an adaptive identification, based on a recursive least squares algorithm, is proposed, which naturally leads to an adaptive compensation of the disturbance. Experimental results confirm the validity of the method