Optimal measurement point planning for workpiece localization

This paper addresses the problem of measurement point planning for 3-D workpiece localization in the presence of part surface errors and measurement errors. A number of frame-invariant norms of the infinitesimal rigid body displacement are defined to quantify the localization accuracy required by manufacturing processes. Then, two kinds of frame-invariant indices are derived to characterize the sensitivities of the accuracy measures to the sampling errors at the measurement points. With a dense set of discrete points on the workpiece datum surfaces pre-defined as candidates for measurement, planning of probing points for accurate recovery of part location is modeled as a combinatorial problem focusing on minimizing the accuracy sensitivity index. A heuristic floating forward search algorithm is presented to efficiently find a near-optimal solution. An example confirms the validity of the presented criteria and algorithm.