Design and Analysis of Two Degree-of-Freedom Rotary-Linear Machines with Hybrid Permanent Magnets for Robotic Applications

In this paper, a double-stator hybrid permanent magnets (PMs) array rotary-linear (RL) machine, which exhibits high linear force density and rotary torque density, is proposed. Due to the yokeless design the proposed machine features high linear and rotary accelerations, which are two important performance indexes for robotic application. In the proposed machine, a specially designed PMs array is adopted in the mover side, which decouples the magnetic fields of linear and rotary motions. The proposed concepts are verified by the analytical model and finite element method. Based on the double-stator structure, linear and rotary motions are controlled individually by the windings set in two stators. A performance comparison between the proposed machine and other double-stator RL machines is conducted. It shows not only the linear force and rotary torque can be enhanced, but the dynamic performances of both motions are also improved. In addition, the linear force and rotary torque in the proposed machine are consistent under single motion or helical motion due to the separated winding.