ASME B89.4.10:2021 pdf free download

ASME B89.4.10:2021 pdf free download MethodsforPerformance Evaluation of Coordinate Measuring System Software
coordinate measuring system (CMS): any piece of equipment that collects coordinates (points), calculates, and displaysadditional information using the measured points.
datum: a theoretically exact point, line, or plane derived from a feature on a part. See ASME Y14.5M-2018.
least-squares fit feature: a feature of perfect form, corresponding to a set of data points, that minimizes the sum of thesquared deviations between the feature and the individual data points.(Reference Nonmandatory Appendix C for addi-tional information.) This term is elsewhere sometimes referred to as the Gaussian associated feature.
NOTE:In this Standard,unless otherwise indicated, the least-squares fitis understood to be not weighted iLe., each point is given equalweight in the least-squares objective function, even if the points in the test data are not exactly evenly spaced.
objective function: a function which is to be optimized by searching for a minimum (or maximum) as its parameters arevaried.Adifferentobjectivefunction is used foreach type of fit,e.g.aleast-squares versus minimum-circumscribed circle.reference evaluation: the evaluation of the substitute feature using a known implementation of an algorithm.
reference feature: a substitute feature used as the basis for evaluating a test feature.
substitute feature: a feature of perfect geometric form that correspondsto a set ofdata points and is intended to minimizean objective function.
test: a basic unit of evaluation, based on one or more related data sets, which are applied to one or more softwareimplementations of an algorithm.
test feature: a substitute feature computed by the software under test.
3 sOFTWARE FUNCTIONs
In normal usage, CMS hardware is used to collect data points (raw data) on the surfaces of parts being inspected.CMSsoftware can process these raw data to construct datums, part coordinate systems, and substitute features that representthe surfaces being inspected. From these constructions, the CMS software can evaluate such characteristics as size,location, orientation, and form.
3.1 Input Data
Raw data to be used to test and analyze CMS software may be obtained by physically inspecting a test workpiece or bymathematicalcomputation.The former represents a test of the entire measuringsystem,while the latter approach avoidsoperator, workpiece,environment, and machine influences.The latter approach also makes it possible to more closelycontrol the raw data sets, including limits on their spatial distribution, as well as inclusion of artificially induced formerrors.For software analysis, the latter approach is the most universally accepted and the most reliable. This is theapproach addressed herein.
3.2 Data Analysis
The raw data points are processed by mathematical algorithms with the purpose to calculate perfect-form substitutefeatures. First, substitute features are calculated to represent the original data. Then the substitute features are used toevaluate conformance to tolerances or to determine other geometric characteristics of the workpiece.An alternative tothe use of substitute features is the use of Functional Gage Simulation, described in Nonmandatory Appendix D.Different methods can be used for obtaining substitute features.These methods may have differentobjective functions,i.e, different criteria for deciding that a particular substitute feature is better or worse than other possible substitutefeatures. Different criteria can, in general, lead to different results. The proper selection of fitting criterion and dataanalysis method is outside the scope of this Standard.Fit criteria are usually based on L”-norm estimation, or minimum-circumscribed, or maximum-inscribed methods. Refer to Nonmandatory Appendix C for explanations of these methods.The objective of this Standard is not to decree that any one method is better than any other.Guidance is provided to theuser for checking whether particular CMS software produces results that agree sufficiently closely with the referenceresults within the context of the design requirements.
4 PERFORMANCE CHARACTERIZATION
This section establishes the characteristics by which CMSsoftware performance is evaluated.These characteristics arediscussed in terms of four categories: quality,robustness,reliability, and ease of use.Characteristics that are not used forperformance evaluation in this Standard are discussed at the end of this section.