Research On Trajectory Optimization Of Hypersonic Vehicle Based On Adaptive Pseudo-spectral Method

The entire flight process of a hypersonic vehicle is a complex process of large maneuver,wide range,strong uncertainty and strong nonlinear constraints.The complex flight environment and the drastically changing atmospheric environment will have a great impact on the entire flight process of the aircraft.It is necessary to design and optimize this type of flight trajectory quickly,efficiently and accurately.Therefore,it is of great significance to study effective trajectory design and optimization methods.In this paper,the design and optimization of hypersonic vehicle trajectory are studied in the aspects of multi-discipline,multi-constraint,multi-objective and real-time,mainly including the following:(1)Designing of a six-degree-of-freedom trajectory for hypersonic vehicle.Based on the description of the coordinate system widely used for aircraft motion,by using the laws of kinematics and Newton’s law,the motion model has been successfully derived,and the relatively complete nonlinear six-degree-of-freedom mathematical model was finally been established.Perform detailed data analysis on aerodynamic force and aerodynamic torque,and fit multi-dimensional typical aerodynamic data through nearest neighbor interpolation,this can ensure the accuracy of the calculation process data.Research on engine thrust models in hot areas,and perform data analysis and modeling on solid rocket motors and scramjets.(2)Researching on the trajectory optimization algorithm of hypersonic vehicle.Aiming at the unsatisfactory performance of the global Radau pseudo-spectral method when solving complex non-smooth problems,a hp adaptive strategy is proposed,and three different trajectory optimization algorithms are introduced.The p-Radau pseudospectral method increases the number of allocation points in the entire interval and improves the calculation accuracy;the h-Radau pseudo-spectral method refines the time interval,reduces the order of the polynomial,and speeds up the calculation.Finally,the two methods are combined to form an adaptive hp-Radau pseudo-spectral method,it is used to optimize the trajectory of the aircraft.(3)Performing segmented trajectory optimization simulation analysis on hypersonic vehicle.The minimum fuel consumption is selected as the performance index for the ascending section,and the maximum range and the shortest time are respectively selected as the performance indicators for the descending section.The adaptive hp-Radau pseudospectral method and the sequential quadratic programming algorithm are combined to solve the trajectory optimization problem.Finally,the integration of the ascending section,the cruise section and the descending section is completed to form a complete and optimized trajectory.(4)Using Qt to develop a set of visual simulation software.The dynamic simulation software uses Matlab as the underlying algorithm calculation,C++ as software design,STK as animation display,and realizes the visual simulation of the flight process in the form of three interactions.Through visual simulation software,researchers can have a deeper grasp of the entire design optimization process,and can also be easily integrated with engineering projects.This article focuses on the trajectory optimization method based on hp adaptive strategy,and has carried out simulation verification.The results show that the adaptive hp-Radau pseudo-spectral method has high solution accuracy,reasonable selection of points,and high calculation efficiency.The optimization results can meet various flight constraints,and it is an effective method for hypersonic vehicle trajectory optimization under multiple constraints.