Wenjing Liu's research while affiliated with China Institute of Veterinary Drug Control and other places

The large-angle attitude maneuver trajectory design and tracking control for flexible spacecraft with slosh structure under attitude measurement errors and actuator faults are investigated in this article. Considering that rapid attitude maneuvers can lead to severe flexible vibrations and liquid sloshing, which in turn affects system stability. Therefore, under the requirement of fast maneuvering, the attitude trajectory is optimized to maximize the system’s stability by establishing a new indicator function, while satisfying multiple physical constraints. Furthermore, the novel adaptive multivariable command filtering backstepping fault-tolerant controller is proposed for the coupled spacecraft, to achieve the finite-time attitude tracking to the optimized trajectory, despite the measurement errors and actuator faults. The merits lie in the modified auxiliary signals and virtual commands design, which can compensate the filter errors, caused by the applied filters to deal with the “explosion of terms” of conventional backstepping control, in finite time with better control performance. The numerical simulations are performed to verify the effectiveness of the proposed method.

The attitude synchronization problem for multiple spacecraft with angular velocity and input constraints is investigated in this article, under the mild assumptions that the leader's states can reach each follower through a path and the communications between followers are bidirectional. An adaptive finite-time distributed observer is designed to estimate the leader's states for each follower spacecraft, which has the superiority in the fully distributed that the communication topology or some other global information is not required, and the finite-time convergence can be guaranteed. Furthermore, the novel auxiliary systems are first proposed to avoid the angular velocity and input constraints being violated, while the finite-time command filtered backstepping controller is designed to track the leader's attitude motion. The remarkable features of the developed algorithm are the global finite-time attitude consensus of multiple spacecraft, with the constraints satisfied. Moreover, the efficiency of the proposed method is illustrated by numerical simulations and real-time platform verification.

In this paper, an adaptive multivariable continuous terminal sliding mode (CTSM) controller with robust input shaper (RIS) is proposed for flexible spacecraft under model uncertainty and external disturbance. Firstly, for the problem of flexible vibration introduced by flexible appendage, the RIS based on disturbance observer is designed. The proposed input shaper can eliminate the flexible vibration effectively even if there are some disturbances in flight. Then, an adaptive multivariable CTSM controller is proposed for attitude tracking of flexible spacecraft, using only information about the output and its first derivative. The features of the developed methods are that it is continuous multivariable controller which attenuates the chattering effectively and the attitude tracking can be achieved in finite time. The stability and robustness properties of the system are proven using Lyapunov function. Finally, some numerical simulations are performed to validate the efficiency of the developed algorithm.

In this article, active vibration suppression and attitude control for flexible spacecraft under model uncertainty and external disturbance are investigated. First, an adaptive disturbance observer (ADO) and flexible vibration observer (FVO) are proposed to estimate the lumped uncertainty and flexible vibration. It is shown that the proposed ADO is nonoverestimated and the first derivative upper bound of disturbance is unknown. Then, based on the proposed observers, a novel controller is designed to suppress flexible vibration and realize attitude control. The remarkable feature of the designed algorithm is that flexible vibration is suppressed and attitude tracking is guaranteed simultaneously without intelligent materials which are used to suppress flexible vibration in the previous work. In addition, high-precision attitude control can be achieved. The rigorous proof of closed-loop system stability is presented using Lyapunov techniques. Finally, numerical simulations are given to illustrate the efficiency of the proposed algorithm.

The tracking control of a flexible hypersonic vehicle with system perturbation and actuator fault is investigated in this paper. A control-oriented model is constructed, which is composed of velocity loop and altitude loop. A double-layer fast adaptive-gain super-twisting disturbance observer (ASTDO) is designed to provide finite-time estimation of the lumped terms of external disturbances and actuator faults. The ASTDO has the property of the non-overestimation of adaptive gains and chattering reduction with higher precision. Based on the estimation of ASTDO, a novel finite-time command filtered backstepping (FCFB) scheme is proposed for the high-order altitude loop. The merit lies in the modified compensating signals and new virtual commands to compensate the command filter errors. The remarkable features of the developed algorithm include the finite-time convergence with higher accuracy and the chattering suppression. Finally, comparative simulation results are given to demonstrate the superiority of the proposed method.

This paper investigates a fuzzy disturbance observer (FDO)-based terminal sliding mode control (TSMC) strategy for the liquid-filled spacecraft with flexible structure(LFS-FS) under control saturation. Firstly, a novel FDO is designed to estimate the lumped uncertainty, including the inertia uncertainty, external disturbance, the coupling of liquid slosh and flexible structure(LF), as well as the parts that exceed control saturation. The merits of the FDO lie in that estimation error can be arbitrarily small by adjusting the designed parameters and the prior information is not required. Then, based on the estimation of FDO, a finite-time TSMC is designed, which has more satisfactory control performance, such as chattering reduction and fast convergence speed. The stability of the closed-loop system is proved strictly by Lyapunov theory. Finally, numerical simulations are presented to demonstrate the effectiveness of the proposed method.