Visual Measurement Method Of Shaft Diameter Based On Invariant Of Elliptic Quadratic Curve

In the environment where the manufacturing industry is moving towards automation,it is a consensus to introduce machine vision technology into mechanical production to improve production efficiency.As the most widely used part in the field of machining,shaft parts are of great significance for the research of online visual measurement technology.Through the research of line structured light visual measurement of shaft diameter technology,this paper proposes a method for measuring the shaft diameter based on the invariant of elliptic quadratic curve.This method effectively solves the problem that when the traditional line structured light vision measures the shaft diameter,the intersection of the light plane and the line which is between the imaging surface pixel point and the camera optical center,cannot be accurately located on the surface of the measured shaft diameter,which affects the accuracy of the shaft diameter measurement.First,the two-step method of camera calibration,light plane calibration technology based on coplanar target,top line calibration technology and Steger's sub-pixel light bar center point detection technology are analyzed.On this basis,the line structure light plane equations,the top line connection equations,and the detection method of the center point of the light bar which are involved in measuring the shaft diameter in this paper are given.Secondly,combined with the camera imaging model,the light bar formed by the intersection of the line structure light and the axis surface profile is analyzed,and the spatial oblique ellipse cone equation of the light bar image is established.The mathematical model of the projection ellipse on the image plane is obtained by coordinate transformation,which lays the foundation for the measurement of the shaft diameter using the quadratic curve invariant.Thirdly,the shaft diameter measurement model is researched and established by using the quadratic curve invariant.Study the ellipse algebra fitting algorithm and ellipse geometric fitting algorithm to obtain the shaft diameter information in the light bar image.By using the invariant of the quadratic curve,the projection ellipse of the imaging surface and the fitting ellipse of the image surface are connected to establish a shaft diameter measurement model.Then analyze the reason for the distortion error of the center coordinates of the projected ellipse,and propose a method to eliminate the distortion of the center projection of the ellipse.Finally,a platform for measuring shaft diameter using line structured light vision is established,the measurement accuracy of the measurement model in this paper is verified,and the factors that affect the measurement accuracy are analyzed.The visual measurement technology of shaft diameter in this paper has certain theoretical research significance and also has certain value in practical engineering applications.