Reduction of Cogging Torque in DC Brushless Motors for Electric Power Steering

Abstract

This research focused on reducing cogging torque in DC brushless motors for electric power steering system without causing steering feel to decline, even during vehicle operation with low steering angles at high vehicle speeds. Cogging torque magnitude was predicted by using FEM analysis, but large differences were seen between the predictions and the actual results. These differences were analyzed theoretically by using a cogging frequency formula, and the mechanism in the actual motor was inspected. As a result, it was found that if the connections among all the stator core junctions were uniform, the cogging target could be achieved.