The Flexible Measurement Method For Relative Pose Between Flanges Of The Ship Inserting Pipe

Inserting pipe is widely used in ship piping systems.The characteristics of long construction period and poor precision control of inserting pipe measurement result in measurement of relative pose of inserting pipe flange becoming a key issue that related ship companies hope to solve.Traditionally,the relative pose between flanges of the ship inserting pipe is measured by on-site sampling method,which has low precision,large randomness and hidden safety risks.A new type of contact measurement method based on pull rope sensors adopted by a few advanced shipyards is also difficult to be widely applied because of its inadaptability to the complex measurement environment on site.This paper applies line laser measurement and auxiliary target tracking technology,and proposes a flexible measurement method for the relative pose between flanges of the ship inserting pipe,which can simultaneously solve the problems above.The line laser sensor in the hand-held measuring instrument measures the coordinates of the hole center of the flange hole,and uses the sensor-target Hand-Eye calibration result and the auxiliary target pose tracked by the monocular camera to perform two coordinate transformations,so that the measurement data is unified in the tracking camera coordinate system,and further processed to obtain flange relative pose data.The pose tracking problem of the auxiliary target based on monocular vision is studied.A multifaceted auxiliary target based on projective invariant decoding is designed.Combined with the center positioning method based on contour extraction,the pose tracking of auxiliary target is achieved,where the marks are multi-angle shot and incomplete.Various types of noise in the flange line laser image are analyzed,and the influence of noise is reduced from much aspects such as measurement attitude optimization and adaptive threshold algorithm.The improved center positioning method and the principle of random sampling are used to extract the center data of the light streaks.The method of 3D circle fitting by plane points improves the accuracy of hole center positioning.The relative pose measurement experiment of the flange is designed and completed whose results show that the error of flange center distance measurement is 0.93 mm and the flange plane normal vector angle measurement error is 0.20°,which meets the design accuracy requirements of the inserting pipe.