【摘要】：高速飛行器周圍會產(chǎn)生復(fù)雜的氣流場，導(dǎo)致氣體密度變化，形成不均勻的光學(xué)折射率分布，進(jìn)而影響光傳輸。激光雷達(dá)可以探測目標(biāo)的多種信息，并且具有極高的測距精度以及分辨率，但氣動光學(xué)效應(yīng)會嚴(yán)重破壞激光雷達(dá)系統(tǒng)的性能。因而研究這種氣流場對激光雷達(dá)系統(tǒng)參數(shù)的影響，進(jìn)而找到修正方法具有重要的研究意義。 本文研究了氣動光學(xué)領(lǐng)域以及激光雷達(dá)測距精度的發(fā)展現(xiàn)狀。目前對于氣動光學(xué)的研究主要集中在提高數(shù)值模擬精確度，建立飛行參數(shù)與光學(xué)畸變的聯(lián)系方程以及自適應(yīng)光學(xué)修正，關(guān)于氣動光學(xué)效應(yīng)對激光雷達(dá)系統(tǒng)測距精度的研究卻鮮有發(fā)表。另外，一直以來關(guān)于氣動光學(xué)的研究一直集中在光學(xué)窗口附近的氣動光學(xué)效應(yīng)，以帶有氣動光學(xué)效應(yīng)的飛行器為目標(biāo)的激光雷達(dá)系統(tǒng)研究卻很少被提到。本文旨在從該改角度出發(fā)對激光雷達(dá)測距精度進(jìn)行研究。 首先，將氣動光學(xué)的統(tǒng)計(jì)理論與大氣光學(xué)進(jìn)行了對比，根據(jù)氣體物態(tài)參數(shù)與飛行狀態(tài)的聯(lián)系方程以及飛行狀態(tài)與光學(xué)性質(zhì)的對應(yīng)關(guān)系，將流場研究引入到了氣動光學(xué)效應(yīng)研究中，并推導(dǎo)了斯特爾比與光程差均方根的聯(lián)系方程，，為計(jì)算激光雷達(dá)回波能量衰減提供了理論基礎(chǔ)。 其次，從光學(xué)折射率隨飛行參數(shù)變化的關(guān)系式出發(fā)，研究分析了激波層所導(dǎo)致的光束偏折大小，給出了偏折角隨飛行參數(shù)以及飛行器外形的變化曲線，最大偏折角可以達(dá)到1.5mr ad。研究分析了曲面激波層所導(dǎo)致的額外焦距，給出了額外焦距與飛行參數(shù)以及飛行器外形的變化關(guān)系。綜合考慮激波的光束偏折效應(yīng)以及額外焦距效應(yīng)，對激光雷達(dá)系統(tǒng)的回波能量進(jìn)行了計(jì)算，結(jié)果表明激波的存在可以使得回波能量衰減70%，極大的影響激光雷達(dá)系統(tǒng)。 最后，推導(dǎo)了一定條件下的激光雷達(dá)回波脈沖響應(yīng)函數(shù)以及其與目標(biāo)外形的關(guān)系式，利用光程差的實(shí)驗(yàn)結(jié)果，分析了目標(biāo)表面湍流層對脈沖測距激光雷達(dá)回波波形的影響。采用光線追跡方法，計(jì)算了氣動流場引起的波面畸變及斯特爾比，進(jìn)而分析了激光雷達(dá)回波受到湍流流場散射所導(dǎo)致的能量衰減。綜合波形畸變與能量衰減，對氣動流場對激光雷達(dá)測距精度的影響進(jìn)行了分析。結(jié)果表明，在湍流層的影響下，長度為12cm的目標(biāo)最大可以產(chǎn)生約為36mm的測距誤差，達(dá)到了目標(biāo)尺度的30%，說明湍流層的散射效應(yīng)對激光雷達(dá)測距精度具有不容忽略的作用。并且，峰值探測回波時間判定法會帶來最小的測距誤差。
[Abstract]:The complex airflow field around the high-speed vehicle will lead to the change of the gas density and the formation of an uneven optical refractive index distribution which will affect the light transmission. Lidar can detect many kinds of information of the target and has high ranging accuracy and resolution. But the performance of the lidar system can be seriously damaged by the aero-optical effect. Therefore, it is of great significance to study the effect of this airflow field on the parameters of lidar system, and to find a correction method. In this paper, the field of aero optics and the development of laser radar ranging accuracy are studied. At present, the research on aero-optics mainly focuses on improving the accuracy of numerical simulation, establishing the relation equation between flight parameters and optical distortion, and adaptive optical correction. However, the research on the accuracy of laser radar system based on aero-optical effect is rarely reported. In addition, the research on aero-optics has been focused on the aerodynamic effect near the optical window, but the research on the lidar system with the aero-optical effect is seldom mentioned. The purpose of this paper is to study the ranging accuracy of lidar from this angle. Firstly, the statistical theory of aero-optics is compared with that of atmospheric optics. According to the relation equation between gas physical state parameters and flight state, and the corresponding relation between flight state and optical properties, the statistical theory of aero-optics is compared with that of atmospheric optics. The study of flow field is introduced into the study of aero-optical effects, and the relation equation between Stelby and the root mean square of optical path difference is derived, which provides a theoretical basis for calculating the energy attenuation of laser radar echo. Secondly, based on the relation between optical refractive index and flight parameters, the beam deflection caused by shock wave layer is studied and analyzed. The curve of deflection angle with flight parameters and the shape of aircraft is given. The maximum deflection angle can reach 1.5mr ad. The additional focal length caused by the curved shock wave layer is analyzed and the relationship between the extra focal length and flight parameters and the shape of the aircraft is given. Considering the beam deflection effect of shock wave and the extra focal length effect, the echo energy of laser radar system is calculated. The results show that the shock wave can attenuate the echo energy by 70%, which greatly affects the laser radar system. Finally, the response function of laser radar echo and the relation between the response function and the shape of the target are derived. The influence of the turbulent layer of the target surface on the echo waveform of the pulse ranging laser radar is analyzed by using the experimental results of optical path difference. The wave surface distortion and Str ratio caused by aerodynamic flow field are calculated by ray tracing method, and the energy attenuation caused by the scattering of laser radar echo by turbulent flow field is analyzed. Combined with waveform distortion and energy attenuation, the influence of aerodynamic flow field on laser radar ranging accuracy is analyzed. The results show that under the influence of turbulent layer, the maximum range error of the target with length of 12cm is about 36mm, which reaches 30 points of the target scale, which indicates that the scattering effect of the turbulent layer can not be ignored to the accuracy of lidar ranging. Moreover, the peak detection echo time determination method will bring the minimum ranging error.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN958.98

【參考文獻(xiàn)】

相關(guān)期刊論文 前4條

1 柳建;李樹民;金鋼;劉順發(fā);張翔;;飛行器外流場對光傳輸?shù)挠绊慬J];光子學(xué)報;2006年04期

2 楊文霞;蔡超;丁明躍;周成平;;超音速湍流脈動流場氣動光學(xué)效應(yīng)分析[J];光子學(xué)報;2009年08期

3 高穹;易仕和;姜宗福;趙玉新;謝文科;;Analysing the structure of the optical path length of a supersonic mixing layer by using wavelet methods[J];Chinese Physics B;2012年06期

4 高穹;易仕和;姜宗福;何霖;謝文科;;Temporal evolution of the optical path difference of a supersonic turbulent boundary layer[J];Chinese Physics B;2013年01期

相關(guān)博士學(xué)位論文 前1條

1 田立豐;超聲速光學(xué)頭罩流場精細(xì)結(jié)構(gòu)及其氣動光學(xué)效應(yīng)的機(jī)理研究[D];國防科學(xué)技術(shù)大學(xué);2011年

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