Research On Attitude-Vibration Coupled Modeling And Fault-Tolerant Control Of Flexible Solar Sail Spacecraft

With the expansion of the field of human exploration into outer space,the solar sail spacecraft has received extensive attention as a new spacecraft that uses solar light pressure to propel.Solar sail spacecraft can change the direction of photopressure thrust through attitude maneuver,and then complete the task of orbit change,so its attitude control is particularly important.At the same time,the special physical configuration of the solar sail spacecraft has the characteristics of large moment of inertia,large flexibility,weak damping,low stiffness and dense mode,which are different from those of ordinary spacecraft.Moreover,the solar sail spacecraft is prone to malfunction because of the complex deep space environment and long running time.Therefore,it is a challenging and significant task to design an effective fault-tolerant control system to ensure the safe navigation of solar sail spacecraft with special dynamic characteristics in the case of failure.In this paper,the flexible solar sail spacecraft is taken as the research object,considering its special physical structure,the combination scheme of actuators and corresponding faults,the attitude dynamics modeling and attitude fault-tolerant control of the solar sail spacecraft are emphatically studied.Firstly,the background and significance of the flexible solar sail spacecraft are introduced.The system outlines the existing flexible solar sail attitude modeling method and the current control methods,and summarizes the fault-tolerant attitude control methods for deep space detectors belonging to flexible solar sail.Secondly,the attitude vibration coupling modeling is carried out for the flexible solar sail spacecraft.The Dalangbert principle and the floating coordinate method are used to establish the attitude and vibration coupling model.The finite element modal analysis and data processing of the flexible solar sail spacecraft are carried out by ABAQUS software to obtain the vibration mode related parameters.The attitude vibration coupling model which effectively reflects the special dynamic characteristics of the flexible solar sail spacecraft is obtained.Thirdly,the zero dynamic analysis is performed on the previously established attitude vibration coupling model,and the controller is further designed according to the analysis result.An adaptive sliding mode controller based on radial basis network is designed for the attitude vibration coupling model.It can effectively deal with the attitude maneuver problem of flexible solar sail with unknown external disturbance and unknown moment of inertia and internal elastic vibration.Finally,it is verified by simulation that the controller can effectively perform attitude maneuvering without significantly exciting the elastic mode.Fourthly,based on the comparative analysis of the actuators for solar sail attitude control in the existing literature,the actuator combination suitable for flexible solar sail maneuvering is selected.Model its faults based on how the propellant-free actuator works.A control error-tolerant allocation strategy based on hybrid integer linear programming is designed for the control variables of two types of actuators and considering faults.In order to further reduce the opening time of the propeller,a chain-incremental control allocation strategy is adopted,and a control torque-tolerant allocation strategy based on chain incremental,linear programming and pulse width pulse frequency(PWPF)modulation method is designed.Both control torque fault-tolerant distribution strategies can ensure the stability of the attitude system under fault conditions,and effectively solve the problem of distribution of propellant-free actuators and pulsed plasma propellers under various working conditions.Finally,in order to effectively reduce the communication load and the number of executions without propellant actuator,an adaptive RBF fault-tolerant controller based on event triggering mechanism is designed.An event triggering mechanism related to control state is designed,and a continuous adaptive control law based on RBF neural network is designed for some possible failure faults combined with event triggering mechanism.The Lyapunov stability analysis proves that the adaptive fault-tolerant controller based on the event trigger mechanism can effectively ensure that the state in the system is ultimately uniformly bounded and effectively avoids the Zeno phenomenon.