I. Introduction
In pursuit of high efficiency and high torque density, permanent magnet (PM) motors have been extensively applied in various industrial fields[1]–[3]. Comparing with electric excitation motors, PM machines have the advantages of high torque density, low copper consumption, excellent energy indicators, etc. Cogging torque is one of the unique problems of PM motors, and it is a key problem that must be considered and solved in the design and manufacture of high-performance PM machines.