Control Allocation of a GEO Satellite for Station-Keeping and Momentum Management by Using Thrusters and Reaction Wheels

Abstract

This paper presents a control allocation method for simultaneous station-keeping and momentum management maneuvers. The considered satellite model is equipped with internal and external actuators to control the satellite’s orbit and attitude and, concurrently, unload the angular momentum stored in the reaction wheels. Our method allocates the external and internal actuators to achieve the control objectives. Internal actuators such as reaction wheels generate torque based on the conservation of the momentum. In this study, two different controllers are utilized to control satellite attitude and reaction wheel speeds. To manage the satellite attitude in three axes, at least three reaction wheels are needed. In this study, four reaction wheels are used to ensure control in case of failure of a reaction wheel. In addition, with six chemical thrusters, east-west and north-south orbit correction maneuvers are performed. For the satellite to serve throughout its service life, fuel optimization of the satellite is required. The proposed control allocation method will enforce constraints that maintain orbital accuracy and the satellite in a nadir pointing attitude configuration while minimizing the use of thrusters, significantly reducing fuel consumption. The method combines the two generally separated objectives of orbital and attitude control through constraints determined by the propulsion system. Numerical simulations are performed to validate the proposed method. The simulations show that using the proposed control allocation method can significantly increase the service life of geostationary satellites.