Torque ripple minimization in permanent magnet synchronous servodrive

Abstract

In this paper the electromagnetic torque developed in permanent magnet synchronous motors is analyzed. Two strategies are discussed for torque ripple minimization. The first is based on numerical predetermination of the current waveform which is imposed by the control in machine phases to obtain a constant torque. The second is a torque regulation based on its on-line instantaneous estimation. To optimize the current waveform and minimize copper losses, two methods for current modulus minimization are compared. One is relative to the optimal current which leads to a perfect constant instantaneous torque with minimum instantaneous current modulus, and the second concerns only the mean current modulus. Relation between current components and torque reference can be expressed by functions after normalization. These functions optimizing the mean torque are easy to implement and can be used for torque ripple minimization.