一种利用外轮廓配准的活塞侧面缺陷检测方法

Method for the detection of the piston side defect based on external contour registration

为了有效地对活塞侧面进行缺陷检测,根据两个相同型号和规格的活塞在相同的光照及角度下拍摄得到的图像极其相似的特点,提出了基于外轮廓配准的活塞侧面缺陷检测方法。该方法分为四步:第一,在特定的光照条件下,对不同型号和规格的标准活塞进行多角度的图像采集,建立标准模板库;第二,利用尺度不变特征转换算法,根据外轮廓特征点对模板图像和待检测图像做图像配准,找到两幅图像相对应的区域;第三,用相同大小的滑动窗口分别对两幅图像的相对应区域进行遍历,提取窗口内的特征,包括灰度均值、灰度方差、垂直投影、水平投影;第四,通过比较两个窗口内的特征值,判断窗口内是否存在缺陷。结果表明,该方法能够有效地检测活塞表面缺陷及确定缺陷位置,准确率约为94.78%,具有较强的实用性。

In order to detect the defects on the side of the piston, we propose an effective method for detecting the piston side defect based on the registration of piston contour according to the high similarity between the images of two pistons of the same type and specification under the same illumination and angle. The method is divided into four steps: first, we establish a standard template dataset by taking multi-angle images of standard pistons of different types and specifications under standard illumination conditions;second, we use the Scale Invariant Feature Transform (SIFT) algorithm to register the template image and the current image according to the piston contour features so as to find the exactly corresponding region of the two images;third, the corresponding regions of the two images are traversed with sliding windows of the same size to calculate such features as mean, variance, vertical projection and horizontal projection;finally, we determine whether there is a defect in the current window by comparing the features of two corresponding windows. The results show that the method can effectively detect the piston surface defect and determine the position of the defect, and that the accuracy rate is 94.78%, and it has strong practicability.