Research On Measurement Method Of Hole Shape And Position Parameters Of Support Plate Of Nuclear Steam Generator

The development of digital measurement technology has made high-precision,high-efficiency,non-contact,online automated measurement widely used in industrial measurement.At present,the theory and application research of digital measurement in the industrial field has made significant progress.However,for the rapid and highprecision measurement of the large-area and large-number hole group in large-scale workpieces,the existing measurement methods cannot meet accuracy,speed,and online measurement requirements simultaneously.This paper study the high-precision measurement method of the shape and position parameters of the large-area hole group,using both close-range photogrammetry technology and computer vision technology.The two technical routes are respectively researched to build and implement the measurement systems,and experiments in both laboratory and field environments are carried out with the completed measurement systems.The satisfactory results prove that this research provides a non-contact,high-precision,and automated measurement method for measuring the shape and position parameters of the hole group in the nuclear power evaporator support plate and solves the challenging online measurement problem of the support plate in our country's third-generation high-temperature gas-cooled nuclear reactor.The work and innovations of this paper mainly include:(1)Considering the problems of the online processing and measurement of the support plate,the existing methods are summarized and analyzed.Two technical routes,including close-range photogrammetry measurement and computer vision measurement,are proposed,and the theoretical basis and interrelationship between the two routes are explained.(2)Applying close-range photogrammetry technology,a measurement system towards the hole group in the support plate is established.By settling a high-precision control field,the target extraction algorithm and image point matching algorithm are studied,and an image point matching method based on ICP and template matching is proposed.The camera is calibrated by a self-checking beam adjustment method through the research on the distortion model of the optical system and the calibration method,and the calibration result is verified experimentally.The accuracy verification experiment is carried out for the photogrammetry measurement system of the hole group in the support plate.Ablation experiments are also conducted to study the influence on the measurement accuracy resulting from the number of cameras and the increase in control points.(3)Based on computer vision measurement technology,a high-precision measurement system for shape and position parameters of the hole group is built using continuous hole-by-hole sweep and intermittent trigger mode.The hardware construction and the software system design are completed accordingly.The relationships among the bed coordinate system,the coordinate system of the support plate workpiece,and the image coordinate system are analyzed,and these three are unified in the same coordinate system.Considering the characteristics of the measurement system and the fieldwork,a sharpness evaluation method based on the extended spatial frequency is proposed to achieve the high-precision focusing requirement of the system.A synchronous sampling method in the online visual inspection system is proposed to realize the online synchronous sampling requirement.Furthermore,a high-precision measurement method for contour parameters under edge constraint conditions is put forward to realize the high-precision measurement of plate hole contour parameters.The error analysis of the measurement system is carried out,and the system's calibration is completed by making a high-precision standard target.Experiments are conducted to verify the measurement accuracy and repeatability accuracy.Moreover,the influences of working distance,the vertical deflection angle of the optical axis,center offset,and other variable factors are studied.The accuracy of the measurement system is also verified under actual working site conditions.The results show that the contour parameter measurement method has the anti-interference ability and can guarantee the measurement accuracy under vibration,light change,and temperature change.