Research On High Precision Fault-tolerant Attitude Control For Deep Space Probe

With the development of space technologies,deep space exploration has become a new central issue of aeronautic and astronautic in many countries.Attitude controller design for deep space probes(DSP)is a key technology for the successful implementation of deep space exploration(DSE),which gives strict requests to the performances of the attitude controller,such as high attitude tracking accuracy,strong robustness to internal and external disturbances,good fault tolerance ability.Therefore,to design a robust attitude fault-tolerant control system for DSP is a subject of great significance and challenge.In this thesis,a high precision fault-tolerant attitude controller is designed for a DSP,which is subject to uncertain time-varying inertia matrix,unknown external disturbances,multiple actuator faults and the installation deviation of the actuator.Firstly,the research background and significance of this subject are introduced,and the development of deep space exploration is expounded.Meanwhile,the development of attitude control technology of deep space exploration is systematically summarized.The possible shortcomings of the application of existing research methods to DSP are presented,and accordingly we establish the research direction and focus of this article.Secondly,the mathematic model of deep space attitude control system is studied.The common coordinate system needed for the description of attitude of deep space probes is introduced,and then the commonly used attitude description methods in engineering application and theoretical research are briefly introduced.Based on this,the attitude kinematics equations and dynamics equations of deep space probe are constructed,and the common faults in deep space attitude control systems are modeled.Thirdly,the unknown disturbance and the uncertainties of moment of inertia of DSP are analyzed.Considering their influence on the control accuracy of attitude control system,as well as considering the time-varying of moment of inertia,a high-precision attitude controller,based on the combination of fast terminal sliding mode control law and adaptive estimation theory,is designed for a class of DSP.In simulation,the proposed attitude control method is compared with the existing control methods to fully verify that the proposed high precision attitude controller has faster convergence rate and higher attitude pointing accuracy and attitude stability.Finally,based on the designed high-precision attitude controller,multiple failures and deviations of actuators are simultaneously considered.To deal with the uncertainty of the reaction flywheel of the deep space probe,a new kind of method is proposed and analyzed.The controller designed based on this method can handle larger installation deviations and has higher control precision.The applicable scope of the designed fault tolerant controller is given,and the maximum installation deviation that can be dealt with is defined.By comparing the proposed controller with other attitude fault-tolerant methods,it is discussed that the designed attitude fault-tolerant controller can handle a larger range of installation deviations with more practical engineering significance.In the simulation,the performance of the controller in three fault cases is simulated and compared,which demonstrates the validity and superiority of the designed attitude fault-tolerant controller.