ASME B89.4.10:2021 pdf free download – Methods for Performance Evaluation of Coordinate Measuring System Software
SCOPE
A critical issue in industrial coordinate metrology is the measurement of a work piece to assure compliance with itsdimensional requirements. When using a computerized coordinate measuring system (CMS), the usual practice is tocorrelate computer-calculated outputs with the dimensional requirements of the workpiece.This correlation isperformed by various computer routines that process dimensional coordinate data sets consisting of measurementsamples of the object being evaluated.
The purpose of this Standard is to provideguidelines for evaluating the quality of solutions generated by CMS softwareand to define minimal documentation requirements for software providers.Additionally, this Standard gives defaultdefinitions for collections of data sets that span a variety of real-world measuring scenarios. These data sets are depen-dent on the fitting algorithm being tested. This Standard is concerned with testing the behavior of algorithm imple-mentation,not the testing of algorithms themselves.Thus, the softwareis treated as a black box; only theinput and outputare observed and evaluated. lt is not the intent of this Standard to endorse or rate any computational method or system.Software performance evaluation is useful because it
(a) allows objective validation of software
(b) reduces the possibility of error in software application(c] defines a method of comparing CMS software
This Standard covers the following areas: input data, feature construction, software documentation, performancecharacterization, and test methodologies.
3 SOFTWARE FUNCTIONS
ln 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 bymathematical computation.The former represents a test ofthe 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 different objective functions,ie., 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 establishesthe characteristics by which CMS software 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.