Determination of uncertainty of coordinate measurements on the basis of the formula for EL,MPE

Abstract

A technique of estimating the uncertainty of coordinate measurements, called the sensitivity analysis method according to ISO/TS 15530-1, developed at University of Bielsko-Biała, is presented. Measurement uncertainty is estimated on the basis of information contained in the formula for the maximum permissible error (EL,MPE) of the applied coordinate measuring system (CMS) and on the basis of its acceptance or reverification test results. Measurement models are of the nature of close mathematical dependencies expressing the measured characteristic in the form of a distance which is a function of coordinates differences of a low number of essential points, properly selected on the workpiece. Measurement models for dimensions and various geometrical deviations were developed. Thanks to the applied vector notation the models are in the form of cross and dot products and they are easily programmable in software such as Matlab, Maple or Python. Detailed examples of the uncertainty analysis for two characteristics (position deviations of the axes of the holes in relation to the datum system) of a car steering knuckle are provided.