Design Of End Effector For CFRP Drilling And Research On Algorithm Of Holes Position Identification

Because of excellent physical and mechanical properties,CFRP is widely used in aerospace field.In aircraft assembly process,the quality of the connection holes between CFRP structure has an important influence on safety and service life of the plane.Due to the large number of holes made in CFRP structural parts,the accuracy and efficiency of manual hole making methods are difficult to meet the assembly requirements of modern aircraft.Aiming at this problem,automatic drilling technology emerges as the times require,and robot automatic drilling technology is one of the most widely used technology.In this context,this paper conducts in-depth research on the hole-making end effector based on industrial robots,designs the structure and control system of the end effector,and proposes a hole position recognition algorithm based on machine vision.Specific content is as follows:Firstly,according to the requirements of hole of CFRP structure and the characteristics of the robot automatic hole making system,functional analysis was carried out on the end effector.According to the functional requirements of the end effector,the structure of each unit is designed in detail,including drilling unit,feed and attitude adjustment unit,visual positioning unit,normal vector detection unit and cantilever hanging plate.The strength and stiffness of the key components is checked and modal analysis is carried out through the finite element simulation.Secondly,according to the design requirements of the end effector control system,this paper determines the "PC+PLC" end effector control system plan,and establishs the MPI-based communication strategy between PC and S7-300 PLC.Based on the adaptive fuzzy PID,the feed motion of the electric spindle is controlled in a closed loop,and according to the control design of each unit component of the end effector,the communication mode and content of each component are determined,so the precise control of S7-300 PLC,robot control cabinet,high-speed camera and 3D laser intelligent sensor is realized by PC.Thirdly,according to the actual needs of camera calibration and workpiece hole position recognition to be drilled,the corresponding image hole position extraction algorithm is developed,and the nine-hole array and the extraction of marking lines are studied.The internal parameters of the camera are determined by the extracted nine-hole array image,and the surface of the workpiece is fitted by interpolation and least squares,and the normal vector at the intersection of the markings on the workpiece surface under the tool coordinate system is determined.Finally,the experiment platform of the end effector is built,and its functions are tested,and carries out drilling experiments.The function and design index of the end effector system are verified by measuring the size and positioning accuracy of the machining holes.