Optimal combined attitude control method for spacecraft based on minimum energy cost

Reaction wheels and magnetorquers are usually employed independently to implement the attitude control of the three axis stabilized satellite. Hybrid use of reaction wheels and magnetorquers brings the benefit of reducing the energy because of the assistance of the Magnetorquers. This paper presents a quaternion based linearized attitude control model with reaction wheels under gravity gradient torque disturbance and an LQ controller is designed. Moreover, base upon the simple algorithms using reaction wheels only, a combined controller separated the required torques for reaction wheels and magnetorquers is developed. Numerical simulation shows that the combined control algorithm can satisfy the requirement of the attitude accuracy. It can also reduce the speed of the reaction wheels and the system power consumption at least 30 percent. The combined controllers are readily applicable to real time practical attitude control.