Straightness measurement of large-diameter steel pipes has always been an important technical problem that plagues modern industrial production. At present, the main methods for measuring large-scale straightness at home and abroad are: laser collimation method, self-collimator method, three-coordinate measurement method, etc. All these measurement methods can only be applied to off-line sampling, and online real-time automatic measurement is not possible. For online real-time automatic detection of large-scale seamless steel tube axial straightness, it has not been solved well in foreign countries; domestic seamless steel pipe manufacturers adopt The visual method measures the straightness of several busbars on the outer surface of the cylindrical surface of the steel tube, so as to estimate the straightness of the axis in any direction. With the continuous development and improvement of the visual inspection technology, the straightness measurement scheme of large-diameter steel pipe based on visual inspection technology should be transported. The student adopts the structured light sensor to obtain the cross-section information of the steel pipe to be tested, thereby obtaining the curvature center coordinate of the cross-section, and by aligning the coordinates of the multi-vision sensor, a plurality of curvature center coordinates can be obtained. From this coordinate, the theoretical spatial axis line can be fitted, and the straightness error can be obtained by the error evaluation principle. The method has large-scale, non-contact measurement speed, fast system flexibility and moderate accuracy, and is especially suitable for geometric parameters of products. Testing and quality monitoring areas.
2 Measurement principle As shown in the figure, the detection system distributes a sensor group composed of a plurality of visual sensors on the steel pipe. Each sensor is projected by the semiconductor laser LD to form a beam of light intersecting the steel pipe to be tested, and a straight line measurement vision of the steel pipe is obtained. Detecting the elliptical arc of the circumference of the cross section of the steel pipe; receiving the image of each elliptical arc by the CCD camera and converting it into an electrical signal; converting it into a digital signal through the image acquisition system into the computer; by appropriate mathematical method, by the partial circumference of the section Get the size of the section and the space of the center of the section 1 Luo Ming. The research and application of multi-sensor vision measurement system: the external parameters of the internal parameters of the camera computer* can be calibrated and transmitted by the camera. V. Three-dimensional coordinates; multiple sensors obtain the dimensions of multiple sections and the three-dimensional space coordinates of the center of the section; comprehensive data can be used to derive the straightness error of the seamless steel tube. 3 Sensor Mathematical Model for Sensor Measurement Schematic UV is defined image Cartesian coordinate system Taking the O point of the camera perspective center as the origin, the Xc axis and the Yc axis are parallel to the image rectangular coordinate U, V, and the Z axis is the camera optical axis, which is perpendicular to the image plane, and the intersection of the optical axis and the image plane is 1, at right angles to the image. The coordinate in the coordinate system is (u, v), then CIXcYcZ constitutes the camera coordinate system, 01 is the camera focal length f, and a reference coordinate system X'.iY'.iZ is called the world coordinate system, and (xw, yw,) is the space point. The coordinates of P in the world coordinate system. (u, v) is the coordinate of the point P in the rectangular coordinate system of the image v. Vision sensor measures the coordinates of the center of the steel tube. For any point on the projected light plane, the relationship between the world coordinate system and the rectangular coordinate system of the image can be simplified as: = I4I5, t=ty is the transformation matrix between the camera coordinate system and the world coordinate system Nx, Ny is the horizontal and vertical pixel spacing of the CCD. The arc of the steel tube is captured by the optical plane through the image acquisition system, and the elliptical arc digital image is obtained. The least squares method can obtain the coordinates (Uc, Vc) of the arc center c in the image rectangular coordinate system and obtain the coordinates (xw, yw, z.) in the world coordinate system. This coordinate is the center of curvature of the measured section. 14 unknown parameters in C coordinate equation (4) (5 cameras and 3 multi-sensor coordinates are unified In order to make the coordinates of multiple sensors feasible, we need to put each sensor's world coordinate system together, which needs to be established A global coordinate system. Here we use a double-event to establish a global coordinate system. As shown in the figure, there are four filaments suspended in the space, and the light plane projected by the light projector and the suspended wire meet the bright spot. It can be aimed at both the camera and the drop-off instrument at the same time. The drop-off instrument is a high-precision angle measuring instrument, and the precision can reach the coordinate system established by the autumn pass-through instrument called OtXtYtZt. The coordinates measured by the theodolite are (XT, yT, ZT). The coordinates measured by the camera are (Xw, yw, z.), and the relationship between them is: 3 orthogonal unit matrix, Zw1t is a three-dimensional translation vector. The 12 parameters in R, t can be obtained by calibration.
4 Experimental results Using the measuring device, the straightness of the seamless steel tube with a radius of 70mm and a length of 1500mm was tested. Compared with the inspection department, the measurement accuracy of the collimation system is higher than 0.1mm. The experiment proves its own due to the visual inspection technology. Features, it is ideal for online real-time measurement of large parts. The visual collimation detection technology proposed in this paper can not only detect the straightness of large parts, but also measure the geometric parameters such as the coaxiality of the large spindle and the straightness of the guide rail in real time.
Aluminium Circle,Aluminium Circle Sheet,Aluminum Circle Sheets,3003 Aluminum Discs
Zhengzhou Yearshine Industry Co., Ltd , https://www.zzyscorp.com