Research Of Alumium Alloy Spot Welding Quality Measuring System Based On Multi-Information Fution

Aluminum alloy spot welding has been widely used in auto and aerial production. But an effective way hasn't been found for on-line inspection of the nugget's quality.The present monitoring system for resistance spot welding quality mainly uses single parameter method to identify the spot welding quality, which identifies the quality according to the one-by-one relation of the characteristic number and the quality parameter in aluminum alloy spot welding. Nevertheless, the measuring method using single or less welding parameters as standards of the inspection and testing will produce great measuring error due to the plentiful factors which affect the spot welding process.In order to overcome the flaw of single parameter measuring method and fully utilize the nugget information gained from various parameters in spot welding process, the aluminum spot welding monitoring system was constructed. Welding magnetic field, voltage and tip displacement are selected as the characteristic signals to measure and estimate the quality of the nuggets. This system uses LabVIEW as programming language of data acquiring module, and uses four-channel high-speed synchronized data acquisition card to synchronously acquire welding magnetic field, voltage and electrode displace during aluminum alloy spot welding. Then extracting characteristic number of welding magnetic field through using correlation analysis, and based on non-linear theory,using both Lyapunov exponent to validate the signals and fractal analysis method to extract the Box dimension number of voltage and electrode displace signals, and last utilizing fuzzy control method to fuse the data and identify the nugget quality.The system is able to acquire the real-time characteristic signals, accurately reflect the change of welding spot nugget during the welding process, accurately identify the nugget quality, and satisfy the real-time measuring in spot welding process.