Decentralized attitude cooperative regulation of spacecraft formation without angular velocity feedback

This paper treats the decentralized cooperative attitude regulation problem without angular-velocity feedback for spacecraft formation flying. The nonlinear attitude dynamic and kinematic equations are considered for the case that the relative quaternion and angular velocity are employed such that the dynamics of formation agents are strongly coupled. More specifically, the controller structure includes a lead filter which is derived without explicit differentiation of attitude to synthesize angular velocity-like signals. And the stability of such a formation is also investigated by the development of a novel Lyapunov function candidate containing cross/mixed terms. Considering the affect of external disturbance, a modified controller is developed to confer the closed-loop system the capability of L₂-gain disturbance attenuation. A sufficient condition is provided under which this controller could render the system uniformly ultimately bounded stable. As such, the closed-loop system is robust with respect to any disturbance within a quantifiable restriction on the amplitude. Numerical examples are presented to demonstrate the efficacy of the proposed controllers to maintain the relative attitude cooperation by correcting for initial offsets and external perturbation effects that tend to disperse the formation.