CAD Model-Based Localization of Parts in Manufacturing

Abstract

The authors present a solution to the problem of determining the location of a part in a robotic manufacturing situation. The problem is solved by matching a database surface description of the part with discrete points measured on its surface. The matching is accomplished through the calculation of a transformation. The transformation specifies the position and orientation of the part as it appears in front of the robot. The method was developed for use in flexible manufacturing where low precision, general purpose fixtures, and positioners are employed. Knowledge of the approximate location of the part is used. In a typical application the uncertainty in the location of the part is small relative to the dimensions of the part, but more than an order of magnitude greater than the tolerances allowed by the manufacturing operation. The introduction of a robot into a manufacturing process requires an investment in time and effort to program the robot. Consequently, industrial robots have found use in large-batch manufacturing such as the automotive industry, where a large volume of identical parts justifies the initial outlays for programming.