Feasibility study on Three Dimensional Reaction Wheel

Abstract

This paper presents a novel satellite attitude control device, Three Dimensional Reaction Wheel (3DRW). 3DRW consists of a spherical rigid metal which can rotate around arbitrary axes by magnetic levitation. 3DRW is 3-DOF device with only one reaction mass so that it would be possible to drastically reduce the weight and volume compared to the conventional attitude control system. Furthermore, this device does not have the mechanical contact as bearings, so longer operational lifetime can be expected. This is also quite significant for future applications. In this study the concept of 3DRW is introduced and then, dynamics of the rotational mass in a magnetic field is formulated and simulated numerically. Experiments of magnetic levitation and rotation are also conducted and the feasibility of this device was examined and demonstrated. Although in these experiments one axis rotation was investigated by applying four magnets, 3-DOF rotation will be easily obtained by adding a pair of magnets perpendicular to the four magnets. The disturbance torque was generated by DC magnetic field for levitation against the gravity as expected. In space application such magnetic field for levitation will be negligible to control the position of the ball, therefore, this disturbance will be also able to be ignored. In recent years small satellites, lighter than 50kg, are very popular to be developed, this device will be promising in reducing the weight and the volume. The precise attitude control for such small satellites with single wheel will be available by introducing active 3-axis control of 3DRW. This enables for those satellites to have more sophiscated missions and longer life on orbit.