Research And Prediction Of Imaging Deviation At Mach Number 0.5-3 For A Blunt Nose Aircraft

When the infrared guided vehicle moves at high speed in the atmosphere,the air and the head of the vehicle have a violent effect,and the air in the head of the vehicle is violently squeezed,resulting in a turbulent flow field with nonuniform density and refractive index.These flow fields will produce aerodynamic thermal effect,thermal radiation effect or transmission effect,so that the target image received by the optical system will be blurred,jittered and deviation.This phenomenon is called aero optical effect.In military applications,the existence of aero optical effects will seriously affect the infrared detection capability of aircraft,thereby reducing the precision of aircraft precision guidance.It is of great significance to study aero optics effects to improve the accuracy of aircraft guidance and deviation correction compensation.This article first introduces the research background and significance of aerodynamic optical effects,as well as the progress of aerodynamic optical research from scratch both domestically and abroad.At the same time,the research content and organizational structure of this topic are also presented.The aerodynamic optical theory of the system was studied,and then Solid Works was used to model the head of the aircraft.GAMBIT is used to divide the grid of the aircraft head,FLUENT is used to calculate the flow field density of the aircraft head,and CFD-POST is used to draw the density distribution map to obtain the aerodynamic flow field distribution of the aircraft head under different conditions.Aero-optical imaging deviation is calculated by using reverse ray tracing in geometric optics,and partial imaging deviation results of aircraft in the range of Mach0.5-3 are analyzed.In order to reduce the number of tests,nine groups of imaging deviation test results are given using orthogonal test strategy,making the test results more representative.Through nine groups of tests,the results show that: 1)The imaging deviation will gradually increase with the increase of Mach number;2)The imaging deviation slope will gradually approach 0 from a positive value with the increase of Mach number;3)With the increase of Mach number,the aero optical flow field in the head the aircraft is gradually compressed.Due to the unknown flight conditions of the aircraft,an improved sparrow algorithm is used in this article to optimize the prediction model of extreme learning machines,use known imaging deviation data to quickly predict unknown data.Although the sparrow search algorithm can quickly find the optimal value,it is easy to get the non-global local optimal solution.It improves the global search ability by using the sine cosine algorithm to optimize the location formula of the discoverer and the location formula of the joiner of Levy flight optimization,and then uses the improved sparrow algorithm to optimize the input weight of the limit learning machine and the hidden layer neuron threshold.The algorithm results show that: 1)The improved algorithm has a faster search speed and reduces the search time of the algorithm;2)According to the evaluation index of the algorithm,the improved algorithm has better estimation and prediction ability.