基于全景視覺(jué)的汽車行駛環(huán)境監(jiān)測(cè)系統(tǒng)關(guān)鍵技術(shù)研究
本文選題:魚(yú)眼攝像頭 + 全景圖像; 參考:《中國(guó)農(nóng)業(yè)大學(xué)》2017年博士論文
【摘要】:基于全景視覺(jué)的汽車行駛環(huán)境監(jiān)測(cè)系統(tǒng)可以為駕駛員提供全景成像和目標(biāo)檢測(cè)兩大駕駛輔助功能,是主動(dòng)安全領(lǐng)域的重要技術(shù),具有重要的應(yīng)用價(jià)值,F(xiàn)有的目標(biāo)檢測(cè)功能主要基于雷達(dá)或普通攝像頭實(shí)現(xiàn),其檢測(cè)算法對(duì)于大視場(chǎng)、大畸變的魚(yú)眼攝像頭并不適用。本文首先對(duì)全景成像系統(tǒng)的標(biāo)定方法進(jìn)行改進(jìn)從而快速獲得精確的系統(tǒng)參數(shù),然后對(duì)基于全景視覺(jué)的行人檢測(cè)算法進(jìn)行研究。主要研究?jī)?nèi)容包括:分析了全景成像系統(tǒng)的標(biāo)定原理。通過(guò)對(duì)比實(shí)驗(yàn)選擇折反射模型作為魚(yú)眼攝像頭的成像模型,以此為基礎(chǔ)進(jìn)行攝像頭的標(biāo)定和全景成像系統(tǒng)的標(biāo)定。為魚(yú)眼攝像頭設(shè)計(jì)一種由三個(gè)相互垂直的標(biāo)定板組成的立體標(biāo)定板,使標(biāo)定時(shí)角點(diǎn)完全覆蓋攝像頭,從而充分利用魚(yú)眼圖像邊緣部分以獲得更精確的攝像頭參數(shù)。在全景系統(tǒng)標(biāo)定板上添加定位塊,保證系統(tǒng)標(biāo)定的穩(wěn)定性。對(duì)魚(yú)眼圖像進(jìn)行前視圖投影和直方圖均衡化,完成預(yù)處理。建立歸一化的行人樣本庫(kù)。分別對(duì)常用的行人描述特征和機(jī)器學(xué)習(xí)算法進(jìn)行分析,包括Haar特征結(jié)合AdaBoost算法,HOG特征結(jié)合SVM算法,以及卷積神經(jīng)網(wǎng)絡(luò)進(jìn)行分類器訓(xùn)練實(shí)驗(yàn),對(duì)所得分類器和訓(xùn)練過(guò)程進(jìn)行評(píng)價(jià),總結(jié)各自的特點(diǎn)。對(duì)行人局部HOG特征與整體HOG特征進(jìn)行對(duì)比,提出基于ROI-HOG特征訓(xùn)練SVM分類器;設(shè)計(jì)卷積神經(jīng)網(wǎng)絡(luò)行人檢測(cè)分類器,優(yōu)化網(wǎng)絡(luò)結(jié)構(gòu)參數(shù),并結(jié)合無(wú)監(jiān)督CNN提取特征與線性SVM分類器監(jiān)督學(xué)習(xí)形成組合分類器,實(shí)現(xiàn)快速準(zhǔn)確的行人檢測(cè)。為充分利用魚(yú)眼圖像的大視場(chǎng),研究如何克服圖像邊緣的大幅度變形。提出了多橫擺角前視投影的方法,將一幅魚(yú)眼圖像展開(kāi)為不同橫擺角的前視投影圖,然后進(jìn)行行人檢測(cè)。圖像任意位置的行人在某一范圍內(nèi)的虛擬橫擺角下的前視圖中,都可去除仿射變形恢復(fù)正常人體比例,方便后續(xù)進(jìn)行行人檢測(cè)。通過(guò)實(shí)驗(yàn)總結(jié)前視圖橫擺角設(shè)置規(guī)則,盡量減少一幅魚(yú)眼圖像的展開(kāi)數(shù),減少檢測(cè)耗時(shí)。進(jìn)行實(shí)車全景系統(tǒng)標(biāo)定實(shí)驗(yàn),結(jié)果表明系統(tǒng)具有較高的標(biāo)定精度和標(biāo)定穩(wěn)定性。采集行車視頻數(shù)據(jù),逐幀標(biāo)記行人形成測(cè)試集,在PC上設(shè)計(jì)評(píng)估軟件,運(yùn)行行人檢測(cè)程序,評(píng)估行人檢測(cè)算法性能,結(jié)果表明在一定距離范圍內(nèi)本文算法可以實(shí)現(xiàn)較高的行人檢測(cè)率。
[Abstract]:The vehicle driving environment monitoring system based on panoramic vision can provide driving assistant functions of panoramic imaging and target detection. It is an important technology in active safety field and has important application value. The existing target detection function is mainly based on radar or ordinary camera, and its detection algorithm is not suitable for large field of view and large distortion fish-eye camera. In this paper, the calibration method of panoramic imaging system is improved to obtain the accurate system parameters quickly, and then the pedestrian detection algorithm based on panoramic vision is studied. The main contents are as follows: the calibration principle of panoramic imaging system is analyzed. The refraction model is chosen as the imaging model of fish-eye camera by contrast experiment, and the camera and panoramic imaging system are calibrated based on the model. A stereo calibration board composed of three vertical calibration boards is designed for the fish-eye camera, which can cover the camera completely when the corners are calibrated, thus making full use of the edge part of the fish-eye image to obtain more accurate camera parameters. A positioning block is added to the panoramic system calibration board to ensure the stability of the system calibration. The front view projection and histogram equalization are used to preprocess the fish eye image. A normalized pedestrian sample bank is established. The common pedestrian description features and machine learning algorithms are analyzed respectively, including Haar feature and AdaBoost algorithm combined with SVM algorithm, and convolution neural network for classifier training experiment. The classifier and training process are evaluated. Summarize their own characteristics. By comparing the local HOG features of pedestrians with the overall HOG features, a SVM classifier based on ROI-HOG feature training is proposed, and a pedestrian detection classifier based on convolution neural network is designed to optimize the network structure parameters. Combined with unsupervised CNN feature extraction and linear SVM classifier supervised learning, a combined classifier is formed to realize fast and accurate pedestrian detection. In order to make full use of the large field of view of the fish-eye image, this paper studies how to overcome the large deformation of the image edge. A method of forward projection with multiple yaw angles is proposed. A fish-eye image is expanded into a forward projection image with different yaw angles, and then pedestrian detection is carried out. In the front view of a virtual yaw angle in any position of the image, the affine deformation can be removed to restore the normal proportion of the human body, and it is convenient to carry out pedestrian detection. The rules of yaw angle setting in front view are summarized by experiments to reduce the expansion number of a fish-eye image and the detection time. The calibration experiment of real vehicle panoramic system shows that the system has high calibration accuracy and stability. Collect the video data of the vehicle, mark the pedestrian to form the test set frame by frame, design the evaluation software on the PC, run the pedestrian detection program, evaluate the performance of the pedestrian detection algorithm, The results show that the proposed algorithm can achieve high pedestrian detection rate within a certain range of distances.
【學(xué)位授予單位】:中國(guó)農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】:博士
【學(xué)位授予年份】:2017
【分類號(hào)】:U463.6
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