A Sequential Probability Ratio Test Method for Quality Monitoring in Robotised GMA Welding

Document type: Conference Papers
Peer reviewed: Yes
Author(s): Stefan Adolfsson, Ali Bahrami, Ingvar Claesson
Title: A Sequential Probability Ratio Test Method for Quality Monitoring in Robotised GMA Welding
Conference name: Proceedings of the 1997 15th International Modal Analysis Conference - IMAC-XV
Year: 1997
Pagination: vol 2, 1622-1628
ISBN: 0-912053-53-4
City: Orlando, FL, USA
ISI number: A1997BH25Y00234
Organization: Blekinge Institute of Technology
Department: Dept. of Signal Processing (Institutionen för signalbehandling)
Dept. of Signal Processing S-372 25 Ronneby
+46 455 780 00
Authors e-mail: Stefan.Adolfsson@isb.hk-r.se
Language: English
Abstract: This paper deals with the problem of automatic monitoring the weld quality when welding with Gas Metal Arc (GMA) in short circuiting mode. Experiments with two different types of T-joints are performed in order to provoke optimal and non-optimal welding conditions. During the experiments, voltage and current are measured from the welding process. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), is used. The algorithm can equivalently be viewed as a cumulative sum (CUSUM) - type test. The test statistics is based upon the fluctuations of amplitude in the weld voltage. It is shown that the fluctuations of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The results obtained from the experiments indicate that it is possible to detect changes in the weld quality automatically and on-line.
Subject: Signal Processing\Detection and Classification
Keywords: Carbon dioxide arc welding, Probability, Quality assurance, Welds, Statistical tests, Robotics, Algorithms