Design and Development of a Compact Magnetic Bearing Momentum Wheel for Micro and Small Satellites

Reaction and momentum wheels have become standard equipment for three-axis attitude stabilisation of conventional satellite classes as used e.g. for telecommunication and remote sensing missions. Owing to very compact mechanical designs and highly integrated electronics, wheels are now also more and more interesting for small satellites up to 100…200 kg with increasingly demanding requirements on attitude control. Wheels suitable for small satellites have a typical momentum capacity up to approximately 0.4 Nms, and masses up to about 2 kg. All existing miniature wheels known to the authors are relying on ball bearings for rotor suspension, which may limit the lifetime of a particular mission or introduce undesired levels of micro-vibrations. Magnetic bearings have the potential to overcome those disadvantages. However, the design of a sufficiently small magnetic bearing with all the necessary components and sub-assemblies involves a number of technical challenges, which are discussed in detail. The paper focuses on the magnetic bearing design process, using magnetic field CAE tools, and the overall wheel design. A prototype of a compact magnetic bearing wheel currently under construction is presented. Moreover, control aspects of the magnetic bearing and the drive motor design will be described and an outlook for further improvements and potential future developments will be given