Study On Dimensional Inspection Of U-Beam Assembly Hole Position

The measurement accuracy of the size of large workpieces is an important measure of its production quality and assembly quality,U-beam as the main bearing part of the bottom of the truck,the size of the U-beam assembly hole detection and real-time feedback will play an important role in the assembly of the truck,if the assembly hole does not meet the accuracy requirements,it will affect the loading process of the truck.With the rapid advancement of science and technology,the greater the demand for U-beam in heavy-duty trucks,the higher the quality requirements,the traditional detection methods of enterprises are mainly three-coordinate and caliper measurement,etc.,but in the measurement process shows slow detection speed,high influence of human factors and other phenomena,so the measurement method of U-beam assembly hole needs to be improved,for the current problems,this paper on the detection of U-beam assembly hole for the following research:Firstly,aiming at the existing detection methods and the detection problems presented by the U-beam assembly holes,this paper proposes a mobile detection scheme based on the U-beam assembly holes,and the corresponding structural aspects of this testing organization were designed,and according to the technical specifications to complete the selection of cameras,optical lenses and light sources and other hardware.Then,the stitching of the image of the U-beam assembly hole was studied.First,the camera is fixed position,and with the help of 7×7 dot square calibration plate to calibrate the camera and image acquisition,after preprocessing the image,then determine the conversion relationship between the camera coordinate system,determine the conversion relationship between the camera coordinate system and the custom global coordinate system by determining the conversion relationship between the custom global coordinate system and the world coordinate system to achieve coordinate system unification.Then the resampling method is used to realize the mapping between the image and the projection plane,so as to realize the single group of image correction and stitching of the left and right cameras,A SURF bi-directional matching algorithm is proposed,in which the mapped images are stitched together by the SURF algorithm and the RANSAC algorithm,and the Euclidean distance is invoked to match the feature points extracted by the SURF operator in both directions,so as to improve the accuracy of matching,and finally the workpiece diagram of the U-beam assembly hole is obtained,but due to the difference in exposure of different cameras,plus the difference in the illumination of different workpieces,there are splicing traces in the workpiece diagram of the U-beam assembly hole,so finally the stitching gaps in the stitched map are processed using the weighted average fusion algorithm.So that the image is beautiful overall.Next,the inspection and study of the assembly hole of the U-beam is studied.When noise is generated during the acquisition process,the image noise is effectively removed by analysis and denoising processing,and a detection method for subpixel edge extraction of images combining coarse positioning and precise positioning is proposed.Firstly,the image edge detection algorithm is studied and experimentally analyzed,and the Canny operator is used to coarsely locate the contour edge of the image,and then the improved Zernike moment is used to precisely locate the image edge,followed by the least squares method to fit the aggregated data of the extracted edge,so as to find out the center position and aperture diameter of the circular hole,Finally,the location of the circular hole is found by the distance formula of Euclidean and the point-to-line distance formula.Finally,through the construction of the experimental platform and the data acquisition and processing of images,the experimental data is compared with the three-coordinate detection data,the technical index requirements of ±0.2mm measurement error of round hole diameter and ±1mm measurement error of position dimension per meter in ideal condition of U-beam assembly hole are satisfied,which verifies the feasibility and accuracy of the movement detection scheme of U-beam assembly hole proposed in this paper.