Abstract: This paper deals with the Integrated Power and Attitude Control System(IPACS) for spacecraft with single-gimbal Variable-Speed Control Moment Gyroscopes(VSCMGs) as main actuator. Two adaptive attitude controllers are designed, one for three axes attitude stable mode and the other for attitude tracking mode of the spacecraft. The dynamic characteristics of VSCMGs are considered in both controllers. The stabilities for both control systems are proved. For the former, the relative attitude description is used, so that the torque jump which may appear when choosing rotation direction in inertial attitude description is avoided. For the latter, the Modified Rodrigues Parameters(MRPs) are used to describe the attitude, thus the design procedure is simplified, and the kinematics singularities are avoided. For the former, the attitude error is provided in the form of subtraction based on the assumption of small attitude angles. For the latter, it is expressed by rotation matrix from desired attitude to current one. The steering law, which can escape the singularities of VSCMGs configuration and balance the speeds of rotors, is proposed. The 3-axis magnetic torquers are applied for desaturation of VSCMGs. Finally, numerical examples based on a small satellite on sun-synchronous orbit are provided, and the simulation results illustrate the feasibility and validity of the proposed control algorithms.

Key words: adaptive tracking, IPACS, VSCMG, energy conversion, momentum discharge