Structural Design and FEA of a New Type of Multi-DOF Spherical Induction Motor without Output Shaft

A new type of multi-DOF(degrees of freedom) spherical induction motor with no output shaft was designed aiming at shortages of current multi-DOF motion systems. This type of motor uses a 2-layer shell-like metal rotor coated on the outermost layer and four independent spherical curved motors based on linear induction motor which are mutually orthogonal. The motor can generate output torque in any direction directly on the outer surface to realize multi-DOF rotary motion around any axis. This paper firstly introduces the structure of this kind of motor, and the output torque distribution of each stator when moving. Then, the motor's size parameters were designed based on the design theory of linear induction motor. Finally, 2D and 3D finite element analysis (FEA) were carried out using ANSYS, and the operating characteristics under different rotor parameters and power supply conditions were obtained, which provides a theoretical basis for the selection of rotor parameters and the implementation of stator's motion control. The results show that this spherical motor can reach up to 5.18Nm torque at 300 rpm with only one working stator, thus meeting the requirements of multi-DOF motion.