Decentralized robust adaptive control for attitude synchronization under directed communication topology

A decentralized adaptive sliding-mode control law which regulates attitude and angular velocity errors of individual spacecraft with respect to reference commands and minimizes relative attitude and angular velocity errors between spacecraft was proposed. A decentralized adaptive sliding-mode control law is designed by introducing appropriate multispacecraft sliding-mode vector, which includes attitude error and angular velocity error of individual spacecraft, as well as relative attitude errors and relative angular velocity errors between spacecraft. An adaptive mechanism to estimate the model uncertainty and external disturbance bound was presented. Convergence of the tracking errors was established using graph theoretic formulation. Numerical simulations are performed to validate the robust performance of the proposed control law in the presence of model uncertainties and disturbances. Simulation results demonstrate that each individual spacecraft converges to the desired attitude and angular velocity with acceptable control magnitude.