Research And Implementation Of Seam Tracking System For Arc Welding Robots

Robot welding is one of the key technologies for modern manufacturing. How to increase the intelligence have become a problem in the development of modern welding technology. Now, however, the robot are working on playback mode with poor ability and high precision of the workpiece. If the workpiece has assembly variation and thermal stress deformation, robot is unable to replicate the ideal seam, this will also directly affect the quality and consistency of workpece. Simple robot system is unable to detect the deviation of the seam, it needs a separate detecting system. Then the deviation is sent to the robot controller to correct the teached trajectory in the welding process.The dissertation analyzes the arc welding robot kinematics, a six-point method of calibrating the tool frame is proposed. The Cartesian space trajectory is planned with S-shaped velocity curve, a weaving trajectory planning method with parameters is proposed. In addition, this dissertation analyzes the physical and mathematical model of static welding arc, the linear relationship between the torch height and the welding current is get. According to the proposed weaving weld trajectory, a weaving arc sensor for robots is studied. By filtering and extracting the welding current signal, the deviation of seam position can be get. According to the deviation, a trajectory correction program online is proposed. This dissertation also research on the structure light measure, a structure light vision sensor is designed. A motion method is used to calibrate the camera parameters, structure light plane and the robot hand-eye relation. The pixel coordinates of feature points of seam can be get by processing the images captured on camera, then converted to the robot coordinate frame. According to the converted coordinates, a trajectory correction program online is proposed.In this dissertation, the weaving trajectory with parameters greatly reduce the interpolation calculation process. The designed arc sensor is simple and low cost, it can achieve v-type and fillet seam tracking. The designed structure light vision sensor is easy to be calibrated and can apply to the complex seam tracking.