Applications of robotics in laser welding

This chapter describes how seam-tracking sensors can be integrated in a robotic laser welding system for automatic teaching of the seam trajectory as well as for correcting small errors from a pre-defined seam trajectory. Calibration procedures are required to derive accurate transformations of laser and sensor tool frames relative to each other or relative to the robot flange. A tool calibration procedure is described that involves movements of the tool above a special calibration object. The accuracy of this procedure is influenced by errors in the robot movement. Therefore, another calibration procedure is developed, which is a direct measurement of the sensor tool frame relative to the laser tool frame. A trajectory-based control approach is presented for real-time seam tracking, where a seam-tracking sensor measures ahead of the laser focal point. In this control approach, sensor measurements are related to the robot position to build a geometric seam trajectory, which is followed by the laser focal point