Reduction of periodic torque ripples in PM synchronous motors using learning variable structure control

PM synchronous motor drives are widely used for high-performance industrial servo applications where torque smoothness is an essential requirement. However, parasitic torque pulsations do exist in PMSM drive due to nonperfect sinusoidal flux distribution, cogging torque and current measurement errors. A consequence of these torque ripples is speed oscillation that deteriorates the drive performance particularly at low speeds. In this paper, we propose a simple plug-in learning variable structure control (LVSC) scheme for generating a compensation reference current to improve the steady-state torque and hence the speed responses. Extensive simulation and experimental investigations have been carried out in order to evaluate the performance of the scheme. Experimental results obtained demonstrate the effectiveness of the proposed control scheme in reducing torque ripples significantly.