Research On Vision Measurement Technology Of Disc Cam Based On Line Structure Light

As a typical roulette part,cam is widely used in mechanical transmission parts.The engine camshaft is a key part of the engine.The contour error of the disc cam on the camshaft directly determines the movement law of the driven member,thereby affecting the working performance of the engine.Existing engine camshafts often use special equipment for contact-type measurement of cams,which not only has poor versatility,but also can' t achieve online intelligent detection of camshafts.Aimed at the non-contact detection of the camshaft of the engine,a linear structured light measurement system consisting of a line laser,a camera,and a computer is established in the paper.Based on the geometric characteristics of the disk cam,a method of measuring the disk cam based on line structured light vision is proposed.Firstly,in order to improve the detection accuracy of the center point of the light bar on the cam surface,the paper combines the template matching algorithm with the edge detection algorithm to ensure that the light bar area is accurately obtained in the high-noise image.The Steger algorithm is used to obtain the pixel of the center point of the light bar in the determined area.This method not only has good robustness,but also avoids large-scale convolution calculations and improves the speed of detecting the center point of the light bar.Aimed at the problem that the high reflectance of the cam mirror on the camshaft affects the algorithm of detecting the center point of the light strip,this paper proposes a light strip image enhancement algorithm based on the Gaussian flat-top function by analyzing the energy distribution of the beam emitted by the line laser.Without changing the gray stripe distribution rule of the light bar,the quality of the light bar in the image is improved,and a high-quality light bar image is provided for cam measurement.Secondly,in the calibration of structured light vision systems,this paper uses mobile lasers to obtain multiple parallel light planes,and uses parallel geometric constraints to optimize the light plane calibration process to overcome the light plane equation parameters obtained from the single-dimensional information of light bar gray scale,which causes defects that can't restrict the calibration process.Since the engine camshaft is composed of multiple cams,in order to achieve the measurement of multiple cams with one clamping,this paper proposes an algorithm that solves the equation of the light plane after the movement based on the linear movement distance of the line laser,which solves the positioning errors caused by multiple clamping and measurement accuracy on cam.Thirdly,in the acquisition of point clouds on the cam surface,because the vision system used in this paper consists of a single laser and a camera,in order to obtain the complete contour information of the cam,it is proposed to rotate the cam at a known angle,and obtain all the point clouds at the initial position through the cam shaft axis equation,which is information coordinate transformation method.In order to solve the problem that it is difficult to ensure the vertical relationship between the light plane and the measured axial position of the camshaft axis,this paper projects the cam point cloud to a plane perpendicular to the axis.These projection points can represent the plane geometric information of the cam profile.In the cam base circle and contour error measurement,according to the camshaft clamping method,the cam measurement reference and design reference are unified,and the base circle radius measurement value is obtained in the process;according to the cam geometric characteristics,the cam sensitive point is used to obtain the peach tip position and search the edge area of the base circle to obtain the cam lift starting point and establish the contour error of the cam lift and return.Finally,on the line structured light measurement system constructed in the paper,the camshaft of the automobile engine is measured to obtain the cam base radius,peach tip position,lift and return contour error.By comparing and analyzing the measurement results of the paper,the cam design values,and measured values obtained by the three-coordinate measuring instrument,the feasibility of the proposed measurement method is verified and factors affecting the measurement accuracy are analyzed.