Electromagnetic Force and Torque Simulations on a Reaction Sphere Laboratory Prototype

L. Rossini[1], O. Chételat[1], E. Onillon[1], Y. Perriard[2]
[1]Centre Suisse d’Electronique et Microtechnique – CSEM, Neuchâtel, Switzerland
[2]Ecole Polytechnique Federale de Lausanne - EPFL, Lausanne, Switzerland

The reaction sphere is a magnetic bearing electromagnetic spherical actuator for satellite attitude control. The reaction sphere consists in a 3D motor composed of a 20-coil stator and an 8-pole permanent magnet rotor. The rotor is synthesized wit a mosaic of 728 cylindrical magnets glued on the rotor back-iron so as to approximate the selected magnetization pattern. These cylindrical magnets have the same magnetic remanence and their height is adjusted to obtain a desired magnetic flux density in the airgap.

A finite element simulation model has been implemented using COMSOL Multiphysics v4.1. The meshed geometry is presented in Figure 1 (left and center). In this article we present finite element simulations of the magnetic flux density, forces, and torques performed using the developed simulation model. Simulations are compared to the expected values of the analytical model and to the measurement performed on the developed laboratory prototype. Simulated magnetic flux density, forces, and torques turned out to be in good agreement with the measured values.