Angle velocity free attitude synchronization adaptive tracking control for satellite formation flying with time-varying delays

An output feedback structured attitude synchronization tracking control law has been developed for satellite formation flying without using explicit absolute angular velocity or relative angular velocity feedback, in which the unknown communication non-uniform various time-delays and inertia matrix are explicitly considered. More specifically, the controller structure includes a low-pass linear filter state which is derived without explicit differentiation of attitude to synthesize angular velocity-like signals, and an adaptive updating law is also involved to identify the satellite inertia matrix such that no knowledge of the inertia of the satellites in formation is required a priori. The associated stability proof is constructive and accomplished by the development of a novel Lyapunov function candidate which proves the formation systems' bounded stability. Simulation results are presented to demonstrate the effectiveness of the control law.