| With the development of science and technology and the rise of high-end manufacturing industry,hydraulic components play an increasingly important role in aviation,shipping,transportation and other fields.Diaphragm pump is one of the core power components of hydraulic components,and its cylinder head is a relatively complex casting and forging.The complete dimensional measurement of the three-dimensional surface of the diaphragm pump cylinder head can provide basic data for the optimization of the forming process,improve the product quality of the diaphragm pump cylinder head and reduce the rate of inferior products.Stereo vision is one of the commonly used methods to obtain the three-dimensional information of hydraulic components.Because of the tedious phase unwrapping in the process of grating projection three-dimensional measurement,and its calibration process is more complex,this paper uses the method of binocular stereo vision combined with digital speckle to carry out the research on the three-dimensional dimension measurement and model reconstruction of diaphragm pump cylinder head.(1)The measurement method of binocular vision system was studied in this paper.The limit constraint and correction theory of binocular vision were deduced,and the solution principle of point cloud in the case of parallel optical axis was given.Besides,the coordinate transformation between the camera and the workpiece to be measured in the three-dimensional space was deduced.The checkerboard and circular array calibration board were adopted to calibrate the camera and the projector,respectively.A new type of circular array calibration board was selected based on the problems of checkerboard calibration board and the comparative analysis of calibration results.In order to solve the interference factors such as natural light and noise in the measurement process,the binocular infrared calibration and epipolar correction method were further investigated.(2)The three-dimensional information of the surface of some hydraulic components such as diaphragm pump cylinder head is difficult to be collected completely,mainly because the surface is easy to reflect light and has weak texture.In this work,digital speckle was adopted to add auxiliary features in the measurement process of diaphragm pump cylinder head surface.The influence of manual spraying speckle and computer generated digital speckle on enhancing auxiliary features of cylinder head surface was compared.The global position random digital speckle and the local position random digital speckle were obtained by computer programming.Results showed that the local random digital speckle could greatly reduce the superposition of digital speckle and highlight the surface auxiliary features of diaphragm pump cylinder head.In order to improve the accuracy of stereo matching in the measurement process,the normalized covariance correlation algorithm was selected to optimize the pixel level corresponding points.The parabolic correlation interpolation method was also adopted to measure the dimension and the reconstruct model of subsequent diaphragm pump cylinder head.(3)A set of three-dimensional surface measurement platform for diaphragm pump cylinder head was designed,which was composed of digital cameras,projection device and conveying mechanism.The digital speckle image of diaphragm pump cylinder head surface was collected by digital cameras.On the basis of binocular infrared camera calibration and epipolar correction,the three-dimensional point cloud data of diaphragm pump cylinder head surface was obtained by using the normalized covariance correlation algorithm.Through cloud data processing and measurement,the relative errors of diameter and bolt hole of diaphragm pump cylinder head size were less than 1.33% and 2.61%respectively.It can be concluded that the online measurement function of three-dimensional dimension for hydraulic components with diaphragm pump cylinder head as the main measurement target in industrial application scenarios can be realized by this platform.In view of the hole phenomenon in the point cloud data of the diaphragm pump cylinder head,the Poisson algorithm was used to reconstruct the point cloud data model,and the reconstruction results could better repair the hole in the point cloud in some areas of the diaphragm pump cylinder head.The experimental results showed that the measurement system and model reconstruction method could basically meet the needs of industrial measurement,and had a certain practical application value.Figure [33] table [3] reference [62]... |
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