Torque Density Improvement of a Low-Speed High-Torque Swirling Actuator Driven by Electromagnetic Radial Force With Integrated Mechanical Gears

The torque density improvement of a low-speed high-torque swirling actuator is presented in this article. The swirling actuator is driven by the electromagnetic radial force and integrated mechanical gears. The electromagnetic radial force generates the circular motion of the swirler, which is converted into the low-speed rotor rotation by the mechanical gears. First, the dimensions of the swirler with 12-pole permanent magnets are optimized to enhance the electromagnetic radial force by analytical calculation and three-dimensional finite-element analysis. Second, an improved gear set with a reduced pressure angle and an increased transmission ratio is designed. The gear efficiency and torque are investigated analytically considering the friction loss. Two prototypes are designed, and the experimental results exhibit that the peak torque density is improved from 27 to 64 Nm/L with a small volume of 0.16 L.