Precise and Robust Large-Shape Formation Using Uncalibrated Vision for a Virtual Mold

Abstract

The surface-reduction-gauging experiment proves the ability of laser-spot assisted, 3D image analysis to characterize the geometry of the surface and provide the CSM target with high precision. It also discloses the extent of measurement precision of surface-reduction gauging and reveals the relationship between the density of laser spots cast on the surface, in spots per unit area, to the accuracy of the characterized geometry of surface. The experimental results also prove the following three premises of the surface extent application of laser spots using CSM-based 3D nominal World-frame-coordinate estimation: Though the nominal optical model and nominal robot kinematics model in the CSM system are globally imperfect, the premise is that as long as the laser spots are close enough to each other within the asymptotic-limit region or volume the relative error between them is close to zero-mean. Therefore, any error on the CSM side does not propagate into the measurement of surface reduction relative to an as-located original surface. The experiment repeatedly proves the premise for a range of surface positions and orientations. Another premise is that error in thickness assessment with laser-spot data is unbiased and random. This means that, provided they are matched, a laser-spot center detected in each camera corresponds to one single physical juncture on the object's surface. In other words, only error in thickness assessment with laser-spot data can be averaged out by applying a large amount of laser-spot data on the surfaces. The results of the above experiment repeatedly verify this premise. There is no bias between 2D position of the detected center of a circular cue and that of a laser spot in camera space if they occupy same physical location. (The "physical location" of the laser-spot center is not, strictly speaking, actually defined. What the tests indicate is that, on average, the software places each camera's camera-space center of a given laser spot in such a way as to represent the same surface juncture in all three cameras.) High-precision surface-change gauging extends the vision-guided-robot system based on CSM into a more potent surface-operating system, one that in practice only can be done by humans, and this in an imprecise, non-uniform, and often ineffective way. A number of surface-finishing tasks entail application of force or pressure combined with in-plane motion in order to achieve a scrubbing, polishing or sanding effect. Such tasks often make use of human dexterity and effort, which can result in repetitive-motion injury and incomplete or uneven treatment of the surface. But with high-precision surface reduction gauging and