Evaluation of multidimensional data from optoelectronic sensors for the determination of the penetration depth in laser-welding

This PhD thesis deals with the estimation of the penetration depth during laser welding with solid-state lasers via optically measurable secondary process quantities. As optically measurable secondary process quantities, the plasma thermal radiation, the backreflected laser radiation and the melt pool geometry were investigated in theory and by experiment. The univariate estimates of penetration depth based on each of these secondary process quantities were combined into a multivariate estimation; and thus, the precision of the penetration depth estimation improved. The results show that by adding further suitable univariate estimates, the precision of the penetration depth estimation can be improved towards a value suitable for industrial use. Details on the precision of univariate estimates and their suitability to contribute an improvement to the multivariate estimation are discussed.