Hybrid Measuring System for Dimensional Metrology Tasks on Large-Volume Workpieces and Assessment of Its Uncertainty

The production and assembly of large engineering structures, many requiring tight tolerances, demand accurate long-distance measurements. This poses a major challenge for metrologists across industries such as energy, aviation, automotive, and machinery. Contact measurements provide high accuracy but are slow, as tactile probes must be moved over large distances. Optical methods are much faster, yet their effective range is usually limited to a few meters, and they generally offer lower accuracy. Measurements of large-scale components are further complicated by varying environmental conditions (e.g., temperature gradients) and the accumulation of different error sources, making high-accuracy measurements difficult to achieve. These challenges motivated the authors to develop hybrid measurement systems (HMS) and methods for improving their accuracy. This paper describes the steps taken to build an HMS combining a large-volume, high-accuracy coordinate measuring machine with a structured-light scanner. It also presents a dedicated method for determining measurement uncertainty in HMS, based on a multiple-measurement strategy. A series of tests were performed on material standards with various shapes, dimensions, and geometric features, using both contact and optical systems. The measurement uncertainties were then evaluated using the developed method. Finally, the method was validated through tests conducted on a selected large-scale engineering object.