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

An output feedback based attitude synchronization tracking control law is developed for satellite formation flying, without using explicit angular velocity feedback, even in the presence of unknown communication non-uniform various time-delay and inertia matrix. More specifically, the controller structure includes a low-pass linear filter state that 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 prior. The associated stability proof is constructive and accomplished by the development of a novel Lyapunov function candidate which proves the formation systems to be bounded stability. Simulation results are presented to demonstrate the effectiveness of the control law.