The motor requirements of the quadruped robot joint module are low speed, high torque, thin and light. The existing permanent magnet synchronous external rotor motors basically meet this application. However, for this type of motor with the same size limit, how to optimize the design of the motor to achieve high-performance output, there are still few studies. In the robot joint module, the torque-mass density ratio that expresses the motor torque/mass is a very critical motor performance evaluation parameter. Based on the external rotor permanent magnet synchronous motor of the same size, this paper analyzes the influence of different slot pole numbers on the performance of the motor, and studies the electromagnetic and mechanical characteristics of the external rotor surface-mounted permanent magnet synchronous motor with the same pole number and different slot number combination. From the perspectives of motor average torque, cogging torque, winding factor, back-EMF, air gap flux density and unbalanced force, comprehensively analyze and compare the effects of four slot- pole combinations on motor performance. The finite element simulation results show that 30 slots/26 poles is a better and feasible option to achieve high torque, low speed and meet size requirements.

joint module;permanent magnet synchronous outer rotor motor; torque mass density ratio; number of slots and poles; finite element