Robust laser-stripe sensor for automated weld-seam-tracking in the shipbuilding industry

Abstract

A new laser stripe sensor system for the automation of welding processes in heavy industries is presented. Conventional laser stripe sensors use expensive multiprocessor boards with up to six digital signal processors (DSP) to cope with the high data rate of 14 Mbyte/s delivered by the sensor's CCD-camera. A new solution using only one highly integrated logic IC (FPGA) has been developed offering the same performance as multiprocessor solutions at a drastically lower price making laser stripe sensors attractive for cost sensitive applications in the heavy industries. Integrating the FPGA in the sensor head facilitates data transmission to the sensor computer as the data rate is decreased by a factor of 700 and can thus be transmitted as a robust RS485 serial signal over large distances. For the detection of the location of the welding groove a new robust fuzzy algorithm has been developed that guarantees a satisfying tracking result even when the welding gap geometry strongly varies or is distorted by noise. Using this new method, investigations carried out on industrial samples from the ship-building industry showed that the fuzzy approach was able to cope with strong seam geometry variations and proved to be superior to conventional approaches.