Research On Automatic Alignment System Of Drilling Riser Based On Vision

Drilling riser is an important equipment unit for offshore deep-water oil and gas exploration and development.Once the failure modes such as weld fatigue cracking occur,it will cause serious economic losses.Therefore,it is necessary to carry out full-scale fatigue test on the newly shipped drilling riser.Accurate alignment of drilling riser and pressure test end plugging device is a necessary part of pressure,sealing and fatigue strength test of drilling riser.The traditional manual alignment technology needs continuous trial and error adjustment in the assembly process of the riser shaft hole,which leads to the low efficiency of the riser fatigue strength test.In the face of the above problems,in order to improve the efficiency of fatigue strength test of drilling riser,this paper takes the shaft hole alignment of pressure test plug and flange end face as the research background,and carries out the shaft hole alignment detection and application research.The main contents are as follows:(1)Firstly,the drilling riser experimental platform is analyzed,and then the technical parameters of the riser pressure test device are described.Secondly,according to the motion characteristics of the pressure test end plugging device,the conversion relationship between the end face of the pressure test plug and the base coordinate system is established,and the distance parameters between the connecting rods are determined by using the drawings.Finally,the functional relationship between the range of attitude angle change and the linear motion of the driving device is constructed by manual adjustment,so as to solve the joint torsion angle.(2)In order to obtain the accurate pose information of the riser flange end face,the extraction and matching algorithm of sub-pixel edge points in the riser flange end face image is firstly analyzed.Then,considering the feasibility and environmental complexity,an off-line pose estimation combined with perspective plane shape matching algorithm is adopted.This method only needs the riser flange end face template and calibration plate to quickly complete the pose estimation of the riser flange end face.(3)In order to obtain the conversion relationship between the end face coordinate system of the pressure test plug and the industrial camera coordinate system,the principle of handeye calibration is first introduced.Aiming at the problem of small-scale movement of the plug of the on-orbit pressure test end plugging device,an on-orbit hand-eye calibration method based on the dot calibration plate is adopted.Then,for the automatic alignment stage,an automatic alignment strategy based on fuzzy control algorithm is used,so that the pressure test end plugging device and the riser flange end face can automatically adjust their attitude according to the angle and displacement error.Finally,a simple model of the riser automatic alignment system is built on the simulation platform,and the effectiveness of the fuzzy controller designed in this paper is verified by the automatic alignment model.(4)The experiment of automatic shaft hole assembly was carried out on the automatic alignment system of drilling riser,including industrial camera calibration experiment,handeye calibration experiment of pressure test end plugging device,pitch angle,yaw angle,roll angle and translation distance accuracy test experiment of pressure test end plugging device,fuzzy control experiment and overall automatic alignment experiment.The experimental results show that the automatic alignment of the drilling riser can be completed by using the visual positioning technology.The method is simple in structure,and the average error of the attitude angle is 0.10 degrees,and the average error of the displacement distance is 0.20 mm,which meets the accuracy requirements of the axial hole alignment of the end face of the pressure test plug and the end face of the riser flange.