Research On Fault-tolerant Guidance And Control For Reentry Hypersonic Vehicles

Because the stability and security of reentry hypersonic flight vehicles are very important, an appropriate fault-tolerant scheme is needed, especially fault-tolerant guidance scheme, to ensure the safety of the aircraft. This paper addresses the fault-tolerant guidance and control techniques for reentry hypersonic flight vehicles in the presence of aircraft failures.Firstly, the background and the significance of the research are summarized, and the knowledge about hypersonic vehicles is introduced. Furthermore, an overview of the reentry guidance problem which is the core problem of this paper is provided and the current research status of guidance technology and fault-tolerant guidance technology of reentry hypersonic flight vehicles is presented.Secondly, an integrated fault-tolerant guidance and control scheme is designed in the presence of actuator stuck faults for reentry hypersonic flight vehicles. This method implements the integrated control of guidance loop and attitude loop and designs a tracking control system among the commands of trajectory state, control input, control torque, and surface deflection angle through predictor-corrector guidance method, backstepping method and control allocation method. The control surface faults are considered and the remaining healthy control surfaces are distributed in an optimal way to compensate the influence of the failed surface.Thirdly, since the fault-tolerant ability of attitude loop is limited, and even if fault-tolerant control of attitude loop can make the attitude track the control commands provided by the guidance loop, the control input under fault condition already may not meet the requirements of the reentry guidance. We need to study on fault-tolerant algorithm in guidance loop. Online trajectory database can be created by the flight data of initial states disturbance and the deviation of aerodynamic coefficients. We use the trajectory database to reconstruct a new trajectory in real-time through fault-tolerant guidance algorithm based on neighboring feasible trajectory existence theorem, ensuring the flight vehicle in a safe and feasible corridor.Finally, since the previous two parts mainly focus on the research about fault-tolerant methods, we directly select a given aerodynamic model in advance. Because the aerodynamic parameters are changing with various factors in the process of the actual flight, we need respectively design nominal aerodynamic model and reconstructed aerodynamic model to introduce the fault and surface information to aerodynamic models and study the dynamic changing process of aerodynamic parameters. Then, the nominal and reshaping aerodynamic models are applied to the reentry guidance system, to obtain reentry guidance trajectory under different aerodynamic models.