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A robust entry guidance law based on terminal sliding mode and second-order differentiator is designed for trajectory tracking in this paper. The bank angle is regarded as the control variable. A novel nonlinear compound controller is designed to make the system with the trajectory-tracking error and its rate as states be input-to-state stable (ISS) with respect to uncertainties. The terminal sliding mode controller is designed to the problem of entry guidance by using the second-order differentiator to estimate the total disturbances. The proposed nonlinear compound control law by employing the second-order differentiator and the terminal sliding mode controller, provide robustness, higher control precision. Also, simulation results are presented to illustrate the effectiveness of the control strategy. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a general framework for synchronized multiple spacecraft rotations via consensus-based virtual structure. In this framework, attitude control systems for formation spacecrafts and virtual structure are designed separately. Both parametric uncertainty and external disturbance are taken into account. A time-varying sliding mode control (TVSMC) algorithm is designed to improve the robustness of the actual attitude control system. As for the virtual attitude control system, a behavioral consensus algorithm is presented to accomplish the attitude maneuver of the entire formation and guarantee a consistent attitude among the local virtual structure counterparts during the attitude maneuver. A multiple virtual sub-structures (MVSSs) system is introduced to enhance current virtual structure scheme when large amounts of spacecrafts are involved in the formation. The attitude of spacecraft is represented by modified Rodrigues parameter (MRP) for its non-redundancy. Finally, a numerical simulation with three synchronization situations is employed to illustrate the effectiveness of the proposed strategy. [Copyright &y& Elsevier]