Wave Surface Identification Based on Stereo Vision and Wave Theory: an Initial Attempt
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摘要:
波高是波浪信息最基本的元素，对波高的精确测量无论是对波浪理论的研究还是数值方法的拓展，都起着指导和验证的作用。文中基于双目立体视觉原理自主搭建了波面光学测量系统，突破了传统测量设备如浪高仪等单点测量的局限性，并将波浪理论融入到数据后处理方法中，对常用的单纯依赖图像的光学测量方法进行了改进。通过在拖曳水池中对单向规则波瞬时波面的识别和重构，并将结果与浪高仪以及理论来波参数进行了对比验证，结果表明该测量系统在大范围波面的测量中误差在1%左右，最后对其在非规则的来波下进行了初步尝试。
Abstract:The wave height is the most basic element of wave information, and accurate measurement of wave heights plays a crucial role in both understanding wave theory and verifying numerical models. An improved optical measurement system was proposed based on the principle of binocular stereo vision, which breaks through the limitations of traditional measurement devices such as wave gauges and other single-point measurements, and improves the commonly used optical measurement method relying solely on images by involving the water wave theory into the data post-processing procedure. Through the identification and reconstruction of the unidirectional regular wave surface in a towing tank and the comparison of the results with the wave gauges and theoretical incoming wave parameters for validation, the research shows that, the measuring system has an error of about 1% in the measurement of a wide-area wave surface. Finally, a preliminary attempt was made on the irregular wave surface identification.
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Key words:
- wave surface identification /
- stereo vision /
- wave theory
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图 2 立体视觉测量经典流程
Figure 2. The standard procedure of the stereo vision measurement system
图 5 试验照片：(a) 聚乙烯泡沫；(b) 标定示例；(c) 左相机瞬时图像；(d) 右相机瞬时图像
Figure 5. Experimental photos: (a) the polyethylene marker; (b) the snapshot of calibration; (c) the snapshot of the left camera; (d) the snapshot of the right camera
图 6 重构出的瞬时波面图： (a) t=20 s；(b) t=30 s；(c) t=40 s；(d) t=50 s (2为1的侧视图)
Figure 6. Reconstructed wave contours: (a) t=20 s; (b) t=30 s; (c) t=40 s; (d) t=50 s (2 is the side-view of 1)
图 7 拟合后的瞬时波面图： (a) t=20 s；(b) t=30 s； (c) t=40 s； (d) t=50 s
Figure 7. Wave contours: (a) t=20 s; (b) t=30 s; (c) t=40 s; (d) t=50 s
图 9 重构出的瞬时波面图：(a) 不规则波；(b) 图9(a)的侧视图
Figure 9. Reconstructed wave contours: (a) irregular waves; (b) the side-view of fig. 9(a)
表 1 立体视觉测量系统标定参数
Table 1. Calibration parameters of the stereo vision measurement system
intrinsic parameter left camera right camera focal length ( fx, fy) / mm [3937.20908, 3936.40700] T [3925.72662, 3924.51774] T principal point (cx, cy) / pixel [1349.85569, 952.73155] T [1278.88564, 886.81188] T distortion (k1, k2, p1, p2) 0.01 × [−2.593, 32.052, 1.046, 0.321] T 0.01 × [ −2.287, 47.839, 0.656, −0.27] T extrinsic parameter rotation [−0.03702, 0.25002, 0.1387] T translation [−1397.67526, −141.94746, 153.43894] T pixel error / pixel [ 0.20014, 0.23406] T [ 0.13965, 0.21090] T 
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表 2 波幅、波数的统计量
Table 2. Statistics of the wave amplitude and the wave number
average maximum minimum variance standard deviation A/mm 40.2810 41.8385 38.3161 0.2096 0.4578 k 2.4803 2.5928 2.3435 0.0012 0.0351
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表 3 双目测量、浪高仪测量与造波机输入参数对比
Table 3. Comparison of parameters obtained by the stereo vision, the wave gauges and the wave maker
parameter stereo vision wave gauge error wave maker error A/mm 40.2810 40.10 0.45% 40 0.70% k 2.4803 2.5112 1.23% 2.5116 1.25% f/Hz 0.7853 0.7899 0.58% 0.79 0.59%
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