ASME B89.4.10 pdf free download

ASME B89.4.10 pdf free download MethodsforPerformance Evaluation of Coordinate Measuring System Software
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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 provide guidelines 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 software is treated as a black box; only the input 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 applicationic) defines a method of comparing cMS software
This Standard covers the following areas: input data, feature construction, software documentation, performancecharacterization, and test methodologies.
1.1 Assumptions
The assumptions inherent in this Standard are as follows:
(a) Measurement uncertainty in coordinate samples is not addressed.
(b) Methods to input predetermined samples to the computational system are available.
(c) Personnel have adequate experience and training to implement the evaluation and understand the implications ofthe results.
1.2 Application
This Standard is one component required for the evaluation of CMSs. Other relevant documents can be found inNonmandatory Appendix E.
1.3 References
The following is a list of standards referenced in this Standard.Unless otherwise noted, the most recent edition shallapply.
ASME Y14.5,Dimensioning and Tolerancing
ASME Y14.5.1，Mathematical Definition of Dimensioning and Tolerancing Principles
Publisher: The American Society of Mechanical Engineers (ASME),Two Park Avenue, New York, NY 10016-5990(www.asme.org)
See Nonmandatory Appendix E for additional, informative references.2 DEFINITIONS
algorithm: a well-defined procedure for solving a particular problem, e.g, sorting algorithms.
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,theleast-squares fit is understood to be not weighted i.e.,.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.A differentobjectivefunction is used for each type ofit,e.g. a least-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 corresponds to a set of data 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 bymathematical computation.The former represents a test oftheentire measuring system, while thelatter 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,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.