Localization of 3-D Objects Having Complex Sculptured Surfaces Using Tactile Sensing and Surface Description

This paper presents a method for locating 3-D objects having complex and sculptured surfaces. Among many complex shaped objects, dies, molds, gears, turbine blades, forged parts, and aerospace structural parts are some examples of particular interest. Locating a part amounts to finding a rigid body transformation between the part coordinate frame and the machine coordinate frame. The presented method determines position and orientation of an object by minimizing the sum of the squared distances of the measurement points from the surface of the object with respect to the parameters of transformation. Tactile sensing by Coordinate Measurement Machine (CMM) has been used as the means of measurement. A criterion for selecting measurement points to avoid singularity and help achieve better accuracy of the solutions has also been discussed. Computer simulation of the algorithm has been performed on objects of various shapes and numerical problems encountered are discussed. Experimental implementation of the method for integration of the algorithm with inspection process is also illustrated.