Topology Comparison of Slotless Permanent Magnet Semispherical Actuators

Abstract

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Closed-loop magnetic bearing and angular velocity control of a reaction sphere actuator

“…Depending on the practical case, the magnetic flux density model can be formulated with a variety of methods including the distributed multipoles (DMP) methods [33][34][35][36], which consists in modeling both the stator coils and the PMs as distributed multipoles, the charge and current models [27,[37][38][39], where PM are replaced by an equivalent spatial (volume or surface) distribution of ''magnetic charges'' that is in turn used as a source term in the magnetostatic field equations, the finite element analysis [40], which is widely adopted in the design optimization and model verification of spherical actuators, and the harmonic model [19,30,22,17,41], which is derived by solving Maxwell's equations under certain boundary conditions to express the solution as a series of space spherical harmonic function. A particular approach to the harmonic model method consists in employing boundary conditions measured on all the rotor surface to reconstruct the magnetic flux density model [42,43].…”

“…Depending on the architecture of the design, force and torque forward models between stator coils and the permanent magnet rotor can be obtained with multiple approaches including the superposition of the approximated interactions between stator and rotor pole pairs [45][46][47][48]24], the Maxwell stress tensor approach [27], and the most commonly employed method based on the Lorentz force law [49,50,17,19,30,37], especially useful when the force/torque is generated by a current-carrying conductor laying in the magnetic field of PM [11]. An alternative approach to characterize torque models, while reducing the computational time, consists in modeling both the stator coils and the permanent magnets as DMP.…”

Torque Evaluation Method for Multi-Degree-of-Freedom Spherical Actuators Considering Cogging Torque under Current Limiting

“…Spherical actuators have several advantages such as a simple structure, a low moment of inertia, and a simple control method compared with conventional multi-degree-of-freedom (DOF) actuating systems that are composed of several single-DOF motors [1]. Therefore, they are expected to be applied in the fields of robotics [2][3][4][5], industrial machinery [6,7] and aerospace [8,9], and have been actively developed. In particular, a permanent magnet synchronous spherical actuator is popular because its torque can be controlled using a torque generating equation around an arbitrary axis.…”

“…In particular, a permanent magnet synchronous spherical actuator is popular because its torque can be controlled using a torque generating equation around an arbitrary axis. For this reason, a variety of studies have focused on the permanent magnet synchronous spherical motor [1,[3][4][5][6]8,9].…”

A new topology of a spherical actuator

“…Therefore, the development of a 3-DOF actuator in a single piece, being lightweight, robust and having few moving parts with easy control, is expected for several applications in the robotics and manufacture industry [2], [5], [6], [7]. The number of publications on the subject of spherical motor or spherical actuators is growing every year.…”