Distributed attitude consensus tracking control for spacecraft formation flying via adaptive nonsingular fast terminal sliding mode control

This article investigates the distributed attitude consensus tracking control for spacecraft formation flying with unknown external disturbances and model uncertainties. First, a terminal sliding mode disturbance observer (TSMDO) is constructed to estimate the generalized disturbances including external disturbances and model uncertainties. The finite-time convergence of the estimation errors using TSMDO is analyzed. Second, a variable structure control law is developed to avoid introducing initial errors of the TSMDO. Third, a novel adaptive nonsingular fast terminal sliding mode (ANFTSM) control law based on TSMDO is proposed to ensure the convergence of attitude tracking errors to zero. Based on theoretical analysis, the finite-time stability can be guaranteed by Lyapunov theory. Finally, the effectiveness of the developed control law is verified via numerical simulations.

Distributed Attitude Synchronization for Spacecraft Formation Flying via Event-Triggered Control

The distributed attitude synchronization control problem for spacecraft formation flying subject to limited energy and computational resources is addressed based on event-triggered mechanism. Firstly, a distributed event-driven controller is designed to achieve attitude coordination with the limitation of energy and computing resources. Under the proposed control strategy, the controller is only updated at the event triggering instants, which effectively reduces the update frequency. Subsequently, an event-triggered strategy is developed to further decrease energy consumption and the amount of computation. The proposed event-triggered function only requires the latest state information about its neighbors, implying that the trigger threshold does not need to be calculated continuously. It is shown that the triggering interval between two successive events is strictly positive, showing that the control system has no Zeno phenomenon. Moreover, the update frequency of the proposed controller can be reduced by more than 90% compared to the update frequency of the corresponding time-driven controller with an update frequency of 10 Hz by choosing appropriate control parameters and the control system can still achieve high-precision convergence. Finally, the effectiveness of the constructed control scheme is verified by numerical simulations.