Study And Prediction Of 0-25km Aero-optics Imaging Deviation For Blunt Head Aircraft

In the atmosphere,the infrared guided aircraft flies at a high speed.Due to the violent compression and friction between the head of the incoming flow and the aircraft,a complex turbulent flow field is generated.These complex turbulent flow fields will produce aero-optical effects,and make the target picture accepted by the optics system have aero-optical imaging deviation,which will affect the precise aiming of aircraft and seriously affect the guidance accuracy,and seriously affect the guidance accuracy.In the research of aero-optical,the aero-optical effect’s analysis and prediction has become one of the important research tasks of modern aircraft.In this paper,firstly,the research background and significance of aero-optical effect are analyzed,the research history of aero-optical effect in recent years is described in detail,and the main research content and chapter arrangement of the paper are introduced.Secondly,in the simulation part,fluid mechanics technology is used to model and mesh the head of the aircraft.The density of the flow field near the head of the aircraft is calculated in the finite element analysis software,and the aero-optical flow field distribution in different states is obtained.Then,the fourth order Runge-Kutta method is used to backward ray tracing in the optical calculation part,and the aero-optical imaging deviation under different flight conditions is obtained.The influence of flight altitude on aero-optical imaging deviation is studied,and orthogonal array is introduced for experimental arrangement.Nine groups of representative aero-optical imaging deviation and imaging deviation slope are obtained in the altitude range of 0-25 km.The results show that: 1)The imaging deviation decreases with the increase of altitude.2)With the increase of altitude,the slope of imaging deviation tends to zero from negative value,that is,the change of lower altitude will cause larger imaging deviation,and the imaging deviation is more susceptible to the lower altitude changes.Finally,the regression prediction algorithm was used to realize the rapid estimation of unknown data from the imaging deviation data of known flight conditions,and the rapid estimation and prediction model of aero-optical effect optimized by BP neural network with improved sparrow search algorithm was established.Individual sparrows of the sparrow search algorithm converge to the current optimal solution by directly jumping to the vicinity of the current optimal solution,which leads to the sparrow search algorithm is easy to fall into the local optimal,and the global search ability is poor.Aiming at this shortcoming,the idea of flight behavior of bird colony algorithm is introduced to improve it,so that the entrants can approach the discoverer with a certain probability,which reduces the working time of the algorithm,and ensure the global convergence and the diversity of the population.Four test functions are used to evaluate the performance of the improved sparrow search algorithm,and the evaluation results show that the improved sparrow search algorithm has fast convergence speed and strong searching ability.