Visibility Analysis and Synthesis for Assembly Fixture Certification Using Theodolite Systems

Abstract

In automotive sheet metal assembly, part positioning and clamping is accomplished by fixtures consisting of fixture elements, such as pins and blocks. The locations of these elements are determined during process design and need to be certified during the construction and installation of an assembly line. Usually, theodolite systems are used to certify the locations of these elements by measuring the trihedron points on the fixture elements. However, no systematic method exists for the selection and placement of measuring systems. As a result, the current certification procedure is very time-consuming and is prone to error. This paper presents an algorithm for the optimal setup and placement of theodolite systems based on visibility analysis and synthesis. For a given tooling fixture, the visibility map is introduced to represent the set of potential measurement locations when a number of fixture elements are to be measured. From the set of potential measurement locations, an optimal setup will be selected based on minimizing the number of theodolite heads by optimally locating these theodolites. This approach will minimize measurement setups and improve measurement accuracy.