High-Torque Direct-Drive Machine with Combined Axial- and Radial-flux Out-runner Vernier Permanent Magnet Motor

This paper presents the design, modeling, and numerical performance evaluation for a novel type of high-torque motor, targeting various direct-drive applications such as robot actuator, precision motion rotatry stages, and in-wheel drive for electrical vehicles. The key idea of the motor design is to use a combination of (a) combined axial- and radial-flux electric machine and (b) vernier permanent magnet (VPM) motor. Such combination effectively increases the torque generation capability for the proposed motor, and makes it attractive for direct-drive applications. Analytical model for the motor's performance is derived and is validated using finite element method (FEM), and is used for optimizing the motor design parameters. Motor's losses and efficiency are evaluated by FEM simulations for various magnetic material selections. The mechanical design for the motor is also discussed. The simulation result of the proposed motor demonstrates a 1.5× torque improvement compared with a baseline off-she-shelf direct-drive machine of the same size. The comparison shows that the proposed machine design is promising for the next-generation high-torque direct-drive motors.