Visibility Analysis for Assembly Fixture Calibration Using Screen Space Transformation

In a number of manufacturing processes—tooling installation, calibration, and maintenance—guarantee the precision of fixtures and play important roles toward the overall quality of products. Recently, a new type of measurement equipment called a “laser tracker” was developed and utilized for assembly fixture calibration to shorten calibration time and improve the accuracy of the currently used theodolite systems. Though calibration of the assembly fixture is critical for product quality, as such, calibration time creates a significant burden for productivity of multistation assembly processes. In order to shorten calibration lead time, the number of necessary setups, determined by visibility analysis, needs to be minimized. This paper presents a screen space transformation-based visibility analysis that allows minimizing the number of setups. The screen space transformation is applied to transform the visibility problem from three- to two-dimensional space, thus, efficiently solving the visibility problem. A case study illustrates the procedure and verifies the validity of the proposed methodology. This methodology can be applied not only for manufacturing processes, such as in-line fixture calibration, but also toward analysis and optimization of AGVs, robot navigation systems, and building security.