Method of eliminating velocity ripples in Brushless DC motor based on internal model principle and sliding model control

Abstract

In the practical application, Brushless DC motor (BLDCM) faces various disturbances including parametric uncertainties, load disturbance and unmodeled dynamics. These disturbances can be divided into two types of periodic disturbances (sinusoidal/cosinoidal) and aperiodic (slowly-varying or constant) disturbances. Velocity ripples can be seen as the result of a plurality of periodic interference signals of different frequencies acting on the system. In the paper we propose a composite control scheme combining integral sliding mode control (ISMC) based on disturbance observer (DO) embedded with the internal model principle to improve the speed performance of BLDCM. Conventional disturbance observer, such as extended state observer (ESO) can only asymptotically estimate slowly-varying or constant disturbances and is not good at estimating periodic disturbance. So we combine internal model of disturbance into disturbance observe for high precision. Then, the estimates are introduced in the feedforward compensation, and a composite speed controller is obtained. At last, experimental comparisons with conventional proportional-integral (PI) and ISMC+ESO, are given to validate the effectiveness of the proposed method.