Analytical and Numerical Investigation on the Magnetic Field of Novel PM Spherical Actuator with Outer Rotor

This paper proposes a novel permanent magnet (PM) spherical actuator with an outer rotor. The employment of outer rotor helps to increase the magnetic flux density, and thus to improve the torque output. The investigation of the magnetic field distribution is important for the performance analysis and design of the spherical actuators. The general solution of magnetic scalar potential in 3D space of the spherical actuator is formulated based on Laplace´s equations and spherical harmonics. Specific solutions of magnetic flux density are obtained according to the boundary conditions. Numerical computation is utilized to validate the analytical model and facilitate the observation of the magnetic field variation. The comparison shows that the analytical model is precise and could be used for subsequent design and control implementation. The torque output will be investigated in the further research.