An algorithm for generating an optimum CMM inspection path is developed to improve the throughput of CMMs. In this algorithm, a modified 3-D ray tracing technique is applied to an octree database of a CMM configuration space to detect obstacles between any two target points. After an obstacle is detected, collision-free silhouette contour vertices of the object are generated, from a selection criterion, as potential points of a vertex path. As the ray advances, a sequential-decision-making technique is used to derive the suboptimum vertex path from possible collision-free vertex paths. After the suboptimum vertex path is generated, a selection strategy is employed to ensure a correct edge path sequence for deriving an optimum edge point path. A 3-D simulation shows that the proposed global algorithm eliminates the dynamically undesirable characteristics of octree based algorithms and saves searching time in congested work spaces by finding paths around colliding objects. Actual measurement of a test part indicates that the proposed method can reduce the inspection time to less than half as compared to the interactive graphic method.

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