Research On Weld Beads Laser Recognition And Reconstruction For Rail Weld Beads Grinding Robot

With the development of high-speed rail business, and the popularity of the seamless rail in our country, grinding the weld beads by worker and low automation equipment can not meet the requirements. And it will become a trend and necessity that industrial robots will replaces workers grinding the weld beads because of the popularity and rapid development of industrial robots. In order to grinding the weld beads with the robot, first should recognize it and reconstruct it's model, because it's morphology is very complex and varied, then off-line programming and planning the grinding track according to the model. Therefore this article is research on weld beads laser recognition and reconstruction for rail weld beads grinding robot based on the laser displacement sensor. The main research contents are summarized as follows:(1) Established the kinematics model of robot. First introduced spatial descriptions and coordinate transformation in robotics, and how to build D-H kinematic model and get D-H kinematic parameters. And then using the D-H method, established link coordinate system for Staubli TX200 robot, which is used to grinding the weld beads, and got D-H kinematic parameters after analyzed, then each link's transformation matrix and kinematic equations of the robot are obtained. Finally, established the robot kinematics model by using MATLAB robotics toolbox, and verified the correctness of model with experiments.(2) Completed the hand-eye calibration between the robot and the laser displacement sensor. First, introduced the classification and principle of laser displacement sensor and made a brief introduction to the sensor, which is used in this project. Then studied the principles, processes and derivation algorithm of fixed point from different poses hand-eye calibration method, which can calibrate robot and the laser displacement sensor. And finally with this method by experiment the robot and the sensor are calibrated, and the homogeneous transformation matrix between the coordinates of the robot end-link and the laser displacement sensor is obtained.(3) Reconstructed the point cloud of rail weld beads. First, built a experiment platform, and then manipulated the robot, lets the sensor scanned the rail weld beads, at the same time, recorded the value of robot's joint angles and the sensor. Making use of the robot kinematic model, which established previously, and result of sensor calibration, and recorded experimental data, transformed the coordinate of scanning spot on to robot base coordinate, and got the point cloud of rail weld beads, in order to fitted the point cloud data, studied and researched the Geomagic Studio, which is a reverse engineering software, then imported the point cloud of rail weld beads in to it,and finally got the model of rail weld beads, after processed. Once had the model, can planning grinding track based on it, and grinding weld beads perfectly. At the same time, conducted the experiment of grinding rail weld beads, and the result is not too bad.