Location of objects without use of salient features

Abstract

The physical location of a surface in six degrees of freedom relative to the nominal location of a nominal surface is uniquely defined automatically by a measurement system provided with a processing unit, if sufficient asymmetric curvature exists in the surface to uniquely locate three points on the surface. Useful in inspection and material handling applications, a master model of the surface with a known location is defined. Two points are selected on the surface and then a plane is passed through the points, preferably perpendicular to the surface if no edge is present. Then a third point is selected along the curve of intersection so that the three points form a unique triangular template that locates the points along the curve. If the three points are on a sharp edge of the surface this may be adequate information. Otherwise a plane is passed through one of the points (or two planes, one through each of the two points), preferably perpendicular to the first plane, and two additional points are selected along the curve of intersection so that the three points form a unique triangular template that locates the points in the direction orthogonal to the direction of the first curve. Thus, depending on the surface curvature, as few as three points are chosen and measurements made in those relative locations on the surface to be located. By fitting the measured data to the nominal model surface, the location of the surface relative to the model can be determined.