Attitude cooperative control of spacecraft formation via output-feedback

Purpose - The purpose of this paper is to propose a decentralized output feedback controller for cooperative attitude regulation of spacecraft formation in absence of angular velocity feedback. Design/methodology/approach - The nonlinear relative attitude dynamic and kinematic equations represented by relative quaternion and relative angular velocity, respectively, are considered in this paper. The lead filter is employed to synthesize virtual angular velocity signal so that the design of output feedback controller is achieved. Lyapunov method is adopted to prove the stability of closed-loop system. Considering the external disturbance, the theory of L2-gain disturbance attenuation is employed to improve the designed controller. Numerical simulations are carried out to verify the controllers proposed. Findings - It is found that the closed-loop system can be guaranteed asymptotically stable in absence of external disturbance. When disturbance is considered, as long as the sufficient condition proposed is satisfied, the improved controller can render system uniformly ultimately bounded stable. Practical implications - The proposed output feedback control scheme can be considered as a fall-back alternative for the case that the angular velocity sensors fail, or seen as another option for the system without angular velocity sensors at all. Originality/value - Unlike most classical works in the field of output feedback which focus on centralized scheme and neglect the disturbance, the controller proposed in this paper is able to handle the output feedback control problem of multi-agent formation in a decentralized fashion, so as to avoid the single failure point of a centralized scheme. Meanwhile, the capability of L2-gain disturbance attenuation is also achieved simultaneously.