Product Code: ICAL09_1504

Closed Loop Control of Laser Welding Processes using Cellular Neural Network Cameras: Measurement Technology
Authors:
Andreas Blug, Fraunhofer Institute for Physical Measurement Techniques IPM; Freiburg Germany
Felix Abt, Forschungsgesellschaft Fuer Strahlwerkzeuge Fgsw; Stuttgart Germany
Leonardo Nicolosi, Iee Institut Fuer Grundlagen Der Elektrotechnik U. Elektronik; Dresden Germany
D. Carl, -; -
Friedrich Dausinger, Dausinger & Giesen Gmbh; Stuttgart Germany
Heinrich Hoefler, Fraunhofer Institute for Physical Measurement Techniques Ipm; Freiburg Germany
Ronald Tetzlaff, Iee Institut Fuer Grundlagen Der Elektrotechnik U. Elektronik; Dresden Germany
Rudolf Weber, Institut Fuer Strahlwerkzeuge Ifsw; Stuttgart Germany
Presented at ICALEO 2009

Today, image processing using coaxial camera setups is used to monitor the quality of laser material processes such as laser welding, cutting or ablation. This article proposes a sensing system for the next step: Using image based quality features to form an instant feedback signal in order to maintain the process in the desired state. The key component is a camera based on Cellular Neural Networks (CNN). This technology enables the integration of processor elements in the electronic circuitry of CMOS camera pixels. The result is a massively parallel computing architecture where similar instructions are applied simultaneously to every camera pixel, a so called Single Instruction Multiple Data (SIMD) system. Such systems are very efficient for real time image processing which is necessary for a robust feature analysis in high dynamic laser processes. It is used to control the laser power of a welding system by the contour of the full penetration hole. Algorithms detecting the size of the contour are discussed. Compared to conventional systems, the frame rate for both, acquisition and evaluation rises from about 1 kHz to 14 kHz for area images. Welding results show that the full penetration state is maintained even under rapidly changing process conditions such as steps in material thickness or variation of speed.