The real time monitoring and control of resistance spot welds is a problem of critical importance in automotive and many other manufacturing industries. One of the major problems faced by the process control engineers today is the lack of a reliable, low-cost, nondestructive technique for identifying bad welds and predicting weld strengths in real time. This paper proposes the usage of dynamic weld resistance for the above tasks. A reliable technique for estimating the dynamic resistance profiles is presented, and its usefulness in detecting and identifying a variety of bad welds is demonstrated. Both theoretical and experimental results related to estimation, analysis, and classification of resistance signatures are presented. Furthermore, an outline of the overall monitoring and control scheme is included.
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