Research On Trajectory Optimization And Guidance For Hypersonic Cruise Vehicles

The hypersonic cruise vehicle with its advantages of fast flight speed and significant combat capability has become the focus of national defense technology research in many countries.This paper concentrates on the researches about the trajectory optimization and guidance problems from the scramjet engine’s ignition to finally attacking the target on the ground.Based on those researches,the hypersonic vehicle is able to realize the smooth climb,cruise with optimal trajectory and precise attack on the target.Firstly,according to the derived dynamic equations of the hypersonic cruise vehicle,the flight characteristics and aerodynamic characteristics in climbing phase,cruise phase and dive phase of the aircraft are analyzed respectively.And according to the specific flight missions of different flight phases,three-degree-of-freedom dynamics model is established to describe the changes of the vehicle and the flight trajectory,which is for the analysis of trajectory optimization and guidance methods.Since the scramjet engine is served for propulsion in the process of climbing,the dynamic model is complicated as well as the flight speed of the vehicle is fast,which results in the rapid changing of the flight environment.The simple trajectory design methods are unable to meet the requirement of the flight trajectory design.Hence,this paper aims to solve the trajectory design problem of the climbing phase by proposing the quintic Pythagorean Hodograph curves.The constraints about the altitude,Mach,flight path angle at the starting time and final time of flight are considered.Besides,the flight path constraint to ensure the scramjet engine in operation is also considered in the process of trajectory design.Finally,the trajectory of the climbing phase satisfying all the constraints is achieved.Considering the difference between the aerodynamic model in the actual flight environment and the reference aerodynamic model,the actual dynamic model of the hypersonic cruise vehicle is uncertain.Therefore,the traditional reference trajectory tracking methods cannot satisfy the requirements for guidance in climbing phase.In order to overcome the difficulties during the design of guidance command,an adaptive guidance method based on dynamic inverse is proposed.Based on this method,the guidance command can be generated immediately although the flight environment is changing fast with time.Besides,a least squares identification method with forgetting factor is used to identify the actual aerodynamic parameters online,which ensure that the aerodynamic parameters in the guidance method are close to the actual flight parameters.Hence,the guidance commend is generated with very high precision,which is able to achieve the smooth climb of the hypersonic vehicle under different flight conditions.In order to realize the optimal flight for minimum fuel consumption in the cruise phase,the two typical cruise flights which are steady state cruise and periodic cruise are studied in this paper.Firstly,the description of the trajectory optimization problem in cruise phase is given,including the process constraints such as dynamic pressure,overload and heat flow as well as the endpoint conditions.Then,considering that the steady state cruise indicates that the vehicle flies with fixed height and velocity,the dynamic characteristics of the vehicle are relatively simple.An improved particle swarm optimization algorithm is proposed to obtain the optimal steady state cruise trajectory.Besides,since the dynamic characteristics of the vehicle during the periodic cruise are more complex,a traditional optimization algorithm is adopted and the optimal steady state cruise trajectory is served as the initial value to finally obtain the optimal periodic cruise trajectory.After the cruise phase,the vehicle starts to dive and finally hits on the ground to destroy the target thoroughly.In this paper,first the terminal guidance problem of a single vehicle is discussed to satisfy the required terminal flight path angle and zero terminal miss distance.Besides,considering the limitation on vehicle’s structure and material,the overload of the vehicle should be taken into account.The terminal guidance method proposed in this paper can satisfy the terminal constraints as well as the restriction on overload.Moreover,the cooperative terminal guidance problem of multiple vehicles is also studied.By proposed cooperative terminal guidance strategy,multiple vehicles are able to simultaneously achieve the target on the ground.Finally,the summary and the main innovation of this paper are presented.Besides,some suggestions about the further researches are proposed.