Multi-Bound-Dependent Robust And Fault-tolerant Attitude Control For Flexible Spacecraft

In the rapid development of aerospace industry, the accuracy requirements for the spacecraft are increasing,whether it is communication or positioning,and also closely related to people's lives. So, in order to meet these needs, when the spacecraft is in orbit, the carried accessories are far more than those in 1960s,regardless of the number or type. Due to the existence of objective factors about rocket carrying capacity and economy, more and more manufacturing lightweight materials of flexible appendages appeared in the spacecraft. Thus, the spacecraft attitude control research has gradually shifted to the attitude control of flexible spacecraft. In addition, when the spacecraft is in orbit, the disturbances, time delay and actuator failure often affect the attitude control of the spacecraft. To solve this problem, this paper will discuss the following aspects:(1) For the flexible spacecraft model, only the disturbances and delay are considered firstly. Based on the Lyapunov stability theory and the linear matrix inequality (LMI) method,a delay-dependent H,, state feedback controller is obtained in form of LMI by constructing a new augmented Lyapunov function.Numerical simulations are used to test the validity of the control method and to analysis the disturbances of the delay time, H? performance index and the integral coefficient of the delay integral inequality on the attitude angle and attitude angular velocity of flexible spacecraft.(2) For the partial actuator failure case of flexible spacecraft, a passive fault-tolerant controller is constructed. Firstly, the fault tolerant control with loss of actuator effectiveness is transformed into robust control with uncertain parameters.Secondly, a new multi-bound-dependent robust state feedbackH?, control algorithm is designed. This algorithm is not only dependent on the decomposition coefficient of the time delay integral inequality and time delay bounds, but also depends on the partial failure factor. Finally, the effectiveness of the proposed method is verified by a series of simulations.(3) For the case of partial actuator failure, an adaptive fault tolerant controller is designed by using online estimation, and the compensation control is added to the conventional control law. This compensation method can reduce the fault effect without the need for fault detection and isolation (FDI) mechanism. Compared with some existing results, the design of the controller depends on the time delay and uncertain parameters. Finally, simulation results are given to illustrate the effectiveness of the proposed fault tolerant scheme.