Research On Scanning Imaging Technology Of Eddy Current Testing Based On Six-Degrees-of-Freedom Robotz

Carbon fiber reinforced polymer(CFRP)composites are widely used in automobile,aircraft,medical apparatus and other fields,with corrosion resistance,high structural strength,light weight,weak electrical conductivity and other characteristics.Due to the limitation of preparation technology,defects often exist,so defect detection and quality evaluation of composite materials are particularly important.Eddy current testing(ECT)method has been widely concerned by scholars at home and abroad because of such characteristics as fast speed,no coupling agent and low testing environment requirements.Aiming at complex surfaces and complex shape components,this paper introduces the robot guided ECT scanning technique to realize automatic defect detection of complex surfaces and complex shape components.The main research contents include the kinematic analysis of inspection robot,the design and analysis of scanning tool scheme,the development of coordinate system point surface calibration method,the design and integration of ECT inspection system,the trajectory planning and scanning imaging verification of inspection robot,etc.The specific research contents are as follows.(1)Development of robot guided ECT system.The ECT system RGNTS was designed and developed according to the principle of eddy current testing,software tracking method,combined with robotics technology,digital processing method and computer technology to realize the robot motion control,parameter setting,signal acquisition and scanning imaging and other functions,providing an experimental platform for the research of scanning imaging technology.(2)Kinematics analysis of inspection robot.Taking ER10-C60 robot as the research object,the D-H parameter method and screw theory were used to establish forward and inverse kinematics equations,and Python programming was combined to verify the accuracy of the solution process.The characteristics of the two models were analyzed,and the rational model was selected as the basis for the calibration of the coordinate system and the control of the scanning motion.(3)Design and analysis of scanning tool scheme.According to the physical characteristics of the eddy current probe and the structure characteristics of the rear three axes of the detection robot,a Z-shaped scanning tool was designed,and the bearing capacity of the main components was analyzed and verified based on ANSYS software.Aiming at the deficiency of traditional contact calibration method,a point-plane calibration method of coordinate system was proposed to reduce the difficulty of calibration and improve the accuracy.In view of the dependence of software tracking on models,a point cloud acquisition system was developed based on VC and PCL libraries to provide reliable 3D data for reverse modeling.(4)Research on scanning trajectory planning.Based on the consistency of single path scanning direction,the zigzag and bow trajectory methods were proposed for plate specimen to reduce the detection time.An axial double trajectory method was proposed for curved specimen to reduce the energy consumption of the robot.(5)Research on discrete pixel matching.To solve the problem of C-scan imaging deviating from the actual scanning surface,based on experimental summary and data induction,combined with the defect distribution characteristics of the specimen,the discrete pixel matching was realized through data secondary processing.This study is supported by CRAFT project and Nanjing Life and Health Technology Special Project.The research highlights include the innovation of scanning tool structure and point-plane calibration method,the development of point cloud acquisition system,and the development of eddy current detection system based on LabVIEW.