Research On The Method Of Geometric Dimension Detection Of Assembling Surface Based On Grating Projection

During the assembling process of mechanical products,due to the machining deviation and the assembling surface alignment error,the geometric information of the assembling surface is not matched,which directly affects the improvement of the mechanical assembling efficiency.Therefore,it is of great practical significance to study a non-contact automatic detection method of the geometrical dimensions of the assembling surface for improving the assembling efficiency of mechanical parts.The grating projection method is a three-dimensional reconstruction method based on surface structured light.In this paper,the method is extended to the measurement of the geometric dimensions of the assembling surface,and a geometric dimension detection method of the assembling surface based on the grating projection is proposed.This article takes a certain engine assembling surface as a research object,a grating projection three-dimensional measurement platform is built by digital grating projector and CCD camera,moiré images are collected,and the assembling surface three-dimensionally is reconstructed,thus completing the assembling surface geometric size detection.The detection content includes the assembling surface height,flatness and the dimension information of the threaded hole.The work of this article is as follows:Based on the analysis of commonly used phase solving methods,by comparing the simulation results of various phase shift methods,the four-step phase shift method with low error is used to solve the wrapped phase of the assembling surface.By analyzing the wrapped phase of the optical path and the assembling surface,the phase missing problem in the actual measurement process of the phase shift method is studied,and the missing phase is compensated by the wrapped phase compensation method of the assembling surface,so as to accurately reconstruct the missing wrapped phase area of the assembling surface.In order to solve the problem of accurate unwinding of the wrapped phase on the assembling surface,this paper analyzes the unfolding results of the branching method,the quality map guidance method and the multi-frequency heterodyne method for the wrapped phase of the mounting surface.The multi-frequency heterodyne method is used as the unwinding algorithm of the winding phase to complete the accurate three-dimensional reconstruction of the assembling surface.In this paper,RANSAC and morphology are used to obtain the edge feature points of the point cloud edge of the assembly surface,and then the circle point cloud edge feature points are obtained,and then the least squares algorithm is used to perform round fitting on the obtained point set to obtain the geometric size of the threaded hole of the assembly surface.The surface flatness of the assembly surface is obtained by calculating the degree of the point cloud coordinates deviating from the reference plane.In this paper,the extracted bottom plane is taken as the reference plane and the distance of the point cloud coordinate from the plane to be fitted is taken as the reference,the upper plane of the assembly part with the same direction as the reference plane is obtained,and the distance between the two planes is calculated to obtain the height of the assembly plane.By simulating the assembly surface of the solid rocket motor through the flange workpiece,the test results show that: the measurement error of the geometric dimensions of the threaded holes on the assembly surface is less than 0.05mm;The measuring error of the hole spacing of the thread on the assembly surface is less than 0.08mm;The measurement error of assembly height is less than 0.05mm;The measurement error of flatness of assembly surface is less than 0.05 mm.