Robust control of attitude-orbit tracking system for flexible spacecraft is addressed using state and nonlinear disturbance observer-based control technique. A relative attitude-orbit-structure integrated dynamics model is derived for flexible spacecraft tracking maneuver, where environmental disturbances and parameter uncertainty are considered as lumped disturbance term. The relative position and attitude of the two spacecraft are described by the exponential coordinates on SE(3). A composite control technique is proposed for robust attitudeorbit tracking of a flexible spacecraft about a spacecraft under lumped disturbance by combining a state observer of modal parameter and nonlinear disturbance observer with an asymptotic tracking control. The vibration mode information and the lumped disturbance are estimated and compensated by the modal observer and the nonlinear disturbance observer respectively in the feedback link. Moreover, the stability of the composed control approach consisting of the asymptotic tracking control and multi-observer observer is guaranteed through Lyapunov method. The simulation results validate the composite control technique can effectively enhance disturbance attenuation ability, robust dynamics performance and the desired relative attitude tracking accuracy of a flexible spacecraft with multiple disturbances and parameter uncertainty.Mathematics Subject Classification (2020) MSC 05E15 · 15A30

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