中文摘要：

为了减小管线钢管JCO成形工艺中成形管坯的椭圆度，基于塑性弯曲工程理论和机器视觉测量技术提出了管线钢管JCO精确弯曲成形工艺。在管坯首道次成形过程中，采用两次预弯法，识别出板材的弹复规律，结合管坯目标成形角，预测出精确的压制行程；在后续成形道次中，利用误差补偿技术循环补偿上一道次的成形误差，实现管坯每道次精确弯曲成形。确定了适合管坯端面的图像处理算法、图像处理流程和直线检测算法，提出了采用正三角形作为标定模板求解摄像机外部参数的标定方法，由单幅图片快速、高精度地标定出摄像机的外部参数，建立了将图像角转换为管坯真实成形角的数学模型。实验结果表明，管坯成形角监测误差在0．2°以内，可控制成形管坯的椭圆度在1．5％以内，减小了成形管坯的椭圆度，改变了成形管坯的椭圆度控制依赖于操作者经验的现状。

英文摘要：

To reduce the ellipticity of the steel pipes processed by JCO forming,a precise bending technology was presented based on plastic bending engineering theory and machine vision technology. In the first bending step,the prescribing two-bend was used to obtain the springback law,then using the springback law and con- sidering the aimed bend angle, the exact punch displacement to determine the forming angle in each bending step was predicted. In the succedent bending steps, the bending process was carried out with the exact punch displacement predicted above. The angle error in each bending step was calculated by comparing the actual forming angle with the aimed bend angle, and each precise bending process was realized by compensating for the last angle error in the next bending step. Furthermore, the image processing and line detecting algorithms suitable for the image of the steel pipe end plane were proposed by a machine vision system. A calibration method was presented to calculate the exterior parameters of the CCD camera, which employed a equilateral triangle as the calibration board and only needs to capture one image. A mathematical model was derived to convert the angle in the image into the actual forming angle. Experimental results show that the measuring error of the forming angle is less than 0. 2° and the ellipticity of the formed pipe is less than 1.5%. Employing the precise bending technology, the high-quality pipes can be manufactured without depending on worker＇soperating experiences.