Integrated Optimization of Two Design Techniques for Cogging Torque Reduction Combined With Analytical Method by a Simple Gradient Descent Method

This paper presents an integrated optimization process to minimize cogging torque in permanent-magnet (PM) machines by a simple Gradient Descent method. The presented optimization method can be easily achieved in machine design. The design techniques of nonuniformly distributed magnets and teeth are presented to illustrate the optimization process. First, with the assistance of an analytical model deduced, the initial solution and feasible domain of the optimization can be easily identified. Then a simple Gradient Descent method is combined with finite element analysis to perform the optimization within the identified feasible domain. Four representative PM machines-including surface-mounted permanent-magnet synchronous machine (SPMSM), brushless DC machine (BLDC), and interior permanent-magnet synchronous machine (IPMSM)-are designed and optimized by the presented method, respectively. The results verify that the presented optimization process can greatly reduce the cogging torque in PM machines. In addition, it is easily achieved and very time-saving. At last, the influence of the nonuniformly distributed magnets method on load torque is examined.