Robust attitude consensus control for multiple spacecraft systems with unknown disturbances via variable structure control and adaptive sliding mode control

This paper addresses the robust attitude consensus tracking problem for spacecraft formation flying (SFF) systems in the presence of unknown lumped disturbances including external disturbances and model uncertainties. Firstly, a nonlinear disturbance observer (NDO) considering that the derivatives of the lumped disturbances are nonvanishing is developed to estimate the lumped disturbances. Secondly, based on NDO, sliding mode control and adaptive control theories, a novel variable structure control algorithm is proposed to avoid the introduction of large observation errors of the NDO while ensuring that state errors of the SFF system can converge to zero asymptotically. The designed controller does not need accurate upper bounds of angular acceleration, disturbances, and disturbance derivatives, which makes the control system robust to the lumped disturbances. Moreover, the asymptotical stability can be guaranteed by Lyapunov theory. Finally, numerical simulations are carried out to verify the effectiveness of the proposed control scheme.