轴类零件尺寸的视觉测量技术研究

发布时间：2018-05-31 08:18

本文选题：摄像机标定 + 轴径　；参考：《吉林大学》2017年硕士论文

【摘要】：在精密测试技术领域,机器视觉测量技术是一项新兴技术,该技术可以实现零件的尺寸测量、目标的视觉跟踪及机械装置的运动分析等功能。机器视觉测量技术利用计算机代替“人眼”,看到图像并理解图像,对摄像机采集的数字图像信息特征进行提取,最终完成视觉检测。轴类零件是各类机械装置中应用最广泛的一种零件,随着技术的探索与进步,对机械装置的精密度以及运转速度的要求越来越高,在机加工过程中常常需要对轴类零件进行高精度的加工,因此对轴类零件直径尺寸的准确测量显得尤为重要。本文根据轴类零件的自身几何特征及光学成像过程,提出一种轴径测量方法。首先,本文根据小孔成像原理建立摄像机的成像模型,分析了摄像机标定技术。基于张正友的平面标定法,在畸变模型中考虑两项径向畸变和两项切向畸变,以此修正光学镜头畸变,进而提高了摄像机内部参数和外部参数的标定精度;为提高摄像机参数标定精度,通过摄像机标定实验,确定合适的角点检测数目以及背光源光照强度。然后,为提高图像测量的检测精度,从图像中获取被测物体的亚像素边缘位置是至关重要的。本文首先理论分析了几类常见的亚像素边缘检测方法,包括灰度矩法、空间矩法、Zernike正交矩法、高斯拟合法、双曲正切拟合法、梯度插值法以及三点插值法;最后以实际测量尺寸的误差作为亚像素边缘检测精度的评价准则,通过测量实验,确定了稳定性较好并且检测精度较高的梯度插值法,作为本文轴径测量的亚像素边缘检测方法。接下来,本文首先根据轴零件在摄像机下的成像过程,建立轴径测量的数学模型,并着重减小了轴线与图像平面不平行所带来的误差;然后对轴径测量数学模型中的未知参数进行标定;最后,考虑到测量轴径的实用性与便捷性,提出了一种基于目标轴的真实轴径与像素轴径比值的标定系数方法。最后,通过轴径测量实验,验证本文提出的轴径测量方法的精度及标定系数方法的实用性。对两种轴径测量方法的测量结果进行比较,并分析了影响测量精度的误差因素,为提高测量精度确定方向。对于机器视觉测量技术的发展来说,本文的研究工作有一定的工程应用意义。
[Abstract]:In the field of precision measurement technology, machine vision measurement technology is a new technology, which can realize the functions of measuring the dimension of parts, tracking the vision of the target and analyzing the motion of the mechanical device. The machine vision measurement technology uses the computer instead of the "human eye", sees the image and understands the image, extracts the information feature of the digital image collected by the camera, and finally completes the visual detection. Shaft parts are one of the most widely used parts in all kinds of mechanical devices. With the exploration and progress of technology, the precision and running speed of mechanical devices are becoming more and more demanding. In the process of machining, it is often necessary to process the shaft parts with high precision, so it is very important to measure the diameter of shaft parts accurately. Based on the geometrical characteristics of shaft parts and optical imaging process, a method for measuring axis diameter is presented. Firstly, according to the principle of pinhole imaging, the camera imaging model is established and the camera calibration technology is analyzed. Based on the plane calibration method proposed by Zhang Zhengyou, two radial and two tangential distortions are considered in the distortion model to correct the distortion of the optical lens, and the calibration accuracy of the internal and external parameters of the camera is improved. In order to improve the precision of camera parameter calibration, the appropriate number of corner detection points and the illumination intensity of backlight are determined by camera calibration experiments. Then, in order to improve the accuracy of image measurement, it is very important to obtain the sub-pixel edge position from the image. In this paper, several common sub-pixel edge detection methods, including gray moment method, spatial moment method, Gao Si fitting method, hyperbolic tangent fitting method, gradient interpolation method and three-point interpolation method, are theoretically analyzed. Finally, the error of actual measurement dimension is taken as the evaluation criterion of sub-pixel edge detection accuracy. Through the measurement experiment, the gradient interpolation method with good stability and high detection accuracy is determined. As a subpixel edge detection method for axis diameter measurement in this paper. Then, according to the imaging process of the axis parts under the camera, the mathematical model of the axis diameter measurement is established, and the error caused by the axis is not parallel to the image plane is reduced. Then, the unknown parameters in the mathematical model of axis diameter measurement are calibrated. Finally, considering the practicability and convenience of measuring axis diameter, a calibration coefficient method based on the ratio of real axis diameter to pixel diameter is proposed. Finally, the accuracy of the proposed method and the practicability of the calibration coefficient method are verified by the experimental results. The measurement results of the two methods are compared, and the error factors affecting the measurement accuracy are analyzed to determine the direction for improving the measurement accuracy. For the development of machine vision measurement technology, the research work in this paper has certain engineering application significance.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH133.2;TP391.41

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