Decentralized Adaptive Output Feedback Attitude Synchronization Tracking Control of Satellite Formation Flying

A quaternion-based attitude synchronization tracking problem is treated for satellite formation flying without using absolute and relative angular velocity measurements. More specifically, an adaptive control based output feedback attitude synchronization tracking control law is first developed under the requirement of communication links between each satellite in formation and the desired trajectory. 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 a parameter 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 prior. Then, a modified control law is investigated by involving distributed finite-time sliding mode estimator to relax the requirement that every satellite has access to the desired angular velocity from the practical view of inexpensive online computations. Simulation results are presented to demonstrate the effectiveness of the control law, especially, potential advantages derived through the inclusion of the integral feedback term within the control law being evaluated by computing the attitude synchronization tracking error convergence in the presence of unknown disturbance torques.