Research Of Flange Cover Opening Robot And Its Control Method On Nuclear Power Plant

With the expansion of the scale of nuclear power in China,the daily maintenance and troubleshooting of nuclear power plants have become an urgent problem to be solved.The replacement of RCV filters in nuclear power plants is part of the routine maintenance work.This requires the flange cover to be removed,and the workers must wear complex protective clothing to carry out the work.They work intensively and face a high risk of radiation and health threats.Using robots to replace manual opening of the flange cover can well reduce the radiation risk of workers,which is of great research significance.In this paper,a prototype of flange cap opening robot for nuclear power plant is designed.In order to make the manipulator position the flange cover accurately and loosen the bolt safely and effectively,the corresponding control method is put forward and tested on the developed prototype.Firstly,the operating environment of RCV flange cover in nuclear power plant and the process of using flange cover opening robot are analyzed.This paper studies the overall structure of the robot and the structure of the manipulator arm,and establishes the kinematics model of the manipulator arm,solves the end workspace of the manipulator arm,and proves the feasibility of the structure of the manipulator arm designed in this paper.The structure of the robot control system is introduced,which provides a foundation for the operation control of the following paper.Secondly,this paper studies the alignment control method of flange cover.Visual detection algorithm based on SSD is used to identify the flange cover and bolt.The camera calibration is carried out in this paper,and the 3D coordinates of the target point are determined by solving the PNP problem.Then,the coordinate of the target in the camera coordinate system is converted to the coordinate of the manipulator base system by using the method of hand-eye calibration.The control quantity of joint motor was calculated by inverse kinematics solution,and the position of motor was controlled by fuzzy-pid control method,and the alignment task of flange cover center was completed.Thirdly,the compliance connection method between bolt and socket wrench is studied.Because it is difficult to completely align and match between the socket wrench and the bolt,in order to achieve the smooth docking between the two,the laser distance sensor ranging method is first used to adjust the posture of the socket wrench,so that the socket wrench and the flange cover are completely vertical.In the process of the vertical bolt feeding of the manipulator arm,the active compliance control method based on the force sensor is adopted to adjust the position of the sleeve,and the position deviation between the sleeve and the bolt is adjusted actively to make the socket wrench wrap the bolt smoothly.Finally,the motion control test of the manipulator arm,the compliance alignment test of the bolt and the operation test of the whole machine are carried out on the prototype of the flange cap opening robot.The experimental results show that the robot can accurately align the center of the flange cover and bolt,which verifies the effectiveness and feasibility of the robot to open the flange cover.