1、BSI Standards Publication PD ISO/TS 18571:2014 Road vehicles Objective rating metric for non- ambiguous signalsPD ISO/TS 18571:2014 PUBLISHED DOCUMENT National foreword This Published Document is the UK implementation of ISO/TS 18571:2014. The UK participation in its preparation was entrusted to Tec
2、hnical Committee AUE/15, Safety related to vehicles. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The Brit
3、ish Standards Institution 2014. Published by BSI Standards Limited 2014 ISBN 978 0 580 82290 2 ICS 43.040.01 Compliance with a British Standard cannot confer immunity from legal obligations. This Published Document was published under the authority of the Standards Policy and Strategy Committee on 3
4、1 August 2014. Amendments issued since publication Date Text affectedPD ISO/TS 18571:2014 ISO 2014 Road vehicles Objective rating metric for non-ambiguous signals Vhicules routiers Mesures pour lvaluation objective de signaux non ambigus TECHNICAL SPECIFICATION ISO/TS 18571 First edition 2014-08-01
5、Reference number ISO/TS 18571:2014(E)PD ISO/TS 18571:2014ISO/TS 18571:2014(E)ii ISO 2014 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2014 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electro
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7、41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandPD ISO/TS 18571:2014ISO/TS 18571:2014(E) ISO 2014 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Symbols and abb
8、reviated terms . 1 5 General data requirements . 4 6 ISO metric 4 6.1 Calculation of the overall ISO rating . 5 6.2 Corridor score 5 6.3 Phase, magnitude, and slope scores . 7 7 Meaning of the overall ISO rating .13 8 Pre-processing of the data .13 8.1 Synchronization of the signals 13 8.2 Sampling
9、rate.14 8.3 Filtering 14 8.4 Interval of evaluation .14 9 Limitations .15 9.1 Type of signals 15 9.2 Metric validation 15 9.3 Meaning of the results .15 9.4 Multiple responses .15 Annex A (informative) Case studies 16 Bibliography .61PD ISO/TS 18571:2014ISO/TS 18571:2014(E) Foreword ISO (the Interna
10、tional Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has be
11、en established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical stan
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15、rsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information The committee resp
16、onsible for this document is ISO/TC 22, Road vehicles, Subcommittee SC 10, Impact test procedures.iv ISO 2014 All rights reservedPD ISO/TS 18571:2014ISO/TS 18571:2014(E) Introduction Computer-aided engineering (CAE) has become a vital tool for product development in the automobile industry. Various
17、computer programs and models are developed to simulate dynamic systems. To maximize the use of these models, the validity and predictive capabilities of these models need to be assessed quantitatively. Model validation is the process of comparing CAE model outputs with test measurements in order to
18、assess the validity or predictive capabilities of the CAE model for its intended usage. The fundamental concepts and terminology of model validation have been established mainly by standard committees including the American Institute of Aeronautics and Astronautics (AIAA), 1the American Society of M
19、echanical Engineers (ASME) Standards Committees on verification and validation of Computational Solid Mechanics 2and Computational Fluid Dynamics and Heat Transfer, 3the Defence Modelling and Simulation Office (DMSO) of the United States Department of Defence (DoD), 4the United States Department of
20、Energy (DOE), 5and various other professional societies. 1920 One of the critical tasks to achieve quantitative assessments of models is to develop a validation metric that has the desirable metric properties to quantify the discrepancy between functional or time history responses from both physical
21、 test and simulation result of a dynamic system. 61617Developing quantitative model validation methods has attracted considerable researchers interest in recent years. 11121315171823242527However, the primary consideration in the selection of an effective metric should be based on the application re
22、quirements. In general, the validation metric is a quantitative measurement of the degree of agreement between the physical test and simulation result. This Technical Specification is the essential excerpt of ISO/TR 16250:2013 10which provides standardized calculations of the correlation between two
23、 signals of dynamic systems, and it is validated against multiple vehicle safety case studies. ISO 2014 All rights reserved vPD ISO/TS 18571:2014PD ISO/TS 18571:2014Road vehicles Objective rating metric for non- ambiguous signals 1 Scope This Technical Specification (TS) provides validation metrics
24、and rating procedures to be used to calculate the level of correlation between two non-ambiguous signals obtained from a physical test and a computational model, and is aimed at vehicle safety applications. The objective comparison of time- history signals of model and test is validated against vari
25、ous loading cases under different types of physical loads such as forces, moments, and accelerations. However, other applications might be possible too, but are not within the scope of this Technical Specification. 2 Normative references There are no normative references used in this document. 3 T e
26、rms a nd definiti ons For the purposes of this document, the following terms and definitions apply. 3.1 f i lt er i n g smoothing of signals by using standardized algorithms 3.2 goodness or level of correlation similarity of two signals 3.3 interval of evaluation time domain that is used to calculat
27、e the correlation between two signals 3.4 rating rating score calculated value that represents a certain level of correlation (objective rating) 3.5 sampling rate recording frequency of a signal 3.6 time sample pair values (e.g. time and amplitude) of a recorded signal 3.7 time-history signal physic
28、al value recorded in a time domain; those signals are non-ambiguous 4 Symbols and abbreviated terms CAE Computer-aided engineering TECHNICAL SPECIFICATION ISO/TS 18571:2014(E) ISO 2014 All rights reserved 1PD ISO/TS 18571:2014ISO/TS 18571:2014(E) CORA Correlation and analysis DTW Dynamic time warpin
29、g EEARTH Enhanced error assessment of response time histories SME Subject matter expert a 0 Relative half width of the inner corridor b 0 Relative half width of the outer corridor C, C(t) Analysed signal (CAE signal) C ts , C ts (i) Truncated and shifted CAE curve C ts+d Derivative CAE curve, C ts C
30、 ts+w Warped CAE curve, C ts DTW Dynamic time warping distance DTW opt(i, j) Cost of the optimal warping path d Local cost matrix to perform the dynamic time warping d(i, j) Local cost function to perform the dynamic time warping dtwi, j Cumulative cost matrix t Interval between two time samples i H
31、alf width of the inner corridor i (t) Lower/upper bounds of the inner corridor at time, t, (curve) o Half width of the outer corridor o (t) Lower/upper bounds of the outer corridor at time, t, (curve) E M Magnitude score E P Phase score E S Slope (topology) score M * Maximum allowable magnitude erro
32、r P * Maximum allowable percentage of time shift S * Maximum allowable slope error mag Magnitude error slope Slope error i Index number of time shifted and truncated CAE curve, C ts i k Index number of k-th warping path of curve, C ts2 ISO 2014 All rights reservedPD ISO/TS 18571:2014ISO/TS 18571:201
33、4(E) i w Index number of warping path of CAE curve, C ts j Index number of time shifted and truncated test curve, T ts j k Index number of k-th warping path of curve, T ts j w Index number of warping path of test curve, T ts k Index number k M Exponent factor for calculating the magnitude score, E M
34、 k P Exponent factor for calculating the phase score, E P k S Exponent factor for calculating the slope score, E S k Z Exponent factor for calculating the corridor score between the inner and outer corridors m Time steps moved to evaluate the phase error N Total number of sample points (e.g. time st
35、eps) between the starting time, t start , and ending time, t end N 0 All natural numbers without zero n Number of data samples of time shifted and truncated curves (C tsand T ts ) n w Number of data samples of the optimal warping path n Number of time shifts to get E E Maximum cross correlation of a
36、ll L (m) and R (m) L (m) Cross correlation (signal is moved to the left) R (m) Cross correlation (signal is moved to the right) R Overall ISO rating r Rank of the sliding scale of the ISO metric SC lower(r) Lower threshold of rank, r SC upper(r) Upper threshold of rank, r T, T(t) Reference signal (t
37、est signal) T norm Absolute maximum amplitude of the reference signal, T T ts , T ts ( j) Truncated and shifted test curve T ts+d Derivative test curve, T ts T ts+w Warped test curve, T ts t Time signal (axis of abscissa) t end Ending time of the interval of evaluation t start Starting time of the i
38、nterval of evaluation ISO 2014 All rights reserved 3PD ISO/TS 18571:2014ISO/TS 18571:2014(E) t 0 Time zero of an event (e.g. test, crash, impact etc.) w Warping path w M Weighting factor of the magnitude score, E M w P Weighting factor of the phase score, E P w S Weighting factor of the slope score,
39、 E S w Z Weighting factor of the corridor score, Z w k The k-th warping path cell Z Corridor score Z(t) Corridor score at time, t, (curve) 5 General data requirements The metric described in this Technical Specification requires non-ambiguous curves (e.g. time-history curves). Furthermore, it is req
40、uired that the reference curve, T(t), and the evaluated curve, C(t), are both defined between starting time, t start , and ending time, t end . Both curves shall have the same number of sample points, N, with a constant time interval, t, within the evaluation interval. 6 ISO metric The approach of t
41、his Technical Specification is to combine different types of algorithms to get reliable and robust assessments of the correlation of two signals. The calculated score must provide fair assessment for poor and for good correlations of two signals. The two most promising metrics are identified in Refe
42、rence 10 and they are CORA corridor method and EEARTH. A combined metric based on the improved CORA corridor method and EEARTH is then proposed for an ISO Technical Specification which has been fully validated using responses from multiple vehicle passive safety applications. Figure 1 shows the stru
43、cture of the overall ISO metric. While the corridor method calculates the deviation between curves with the help of automatically generated corridors, the EEARTH method analyses specific curve characteristics such as phase shift, magnitude, and shape. Hence, the ISO metric consists of the two best a
44、vailable algorithms. Figure 1 ISO metric structure4 ISO 2014 All rights reservedPD ISO/TS 18571:2014ISO/TS 18571:2014(E) 6.1 Calculation of the overall ISO rating The combination of the four metric ratings (corridor, phase, magnitude, and slope) will provide a single number, R, for the correlation o
45、f the analysed signals which represents the final overall objective rating. The overall objective rating, R, is calculated by combining the separate sub-ratings of corridor (Z), phase (E P ), magnitude (E M ), and slope (E S ). Four individual weighting factors are defining the influence of each met
46、ric on the overall rating see Formulae (1) and (2). The corresponding weighting factors are shown in Table 1. (1) 1 (2) Table 1 Weighting factors of the ISO sub-ratings Parameter Value Description w Z 0,4 Weighting factor of the corridor score w P 0,2 Weighting factor of the phase score w M 0,2 Weig
47、hting factor of the magnitude score w S 0,2 Weighting factor of the slope score 6.2 Corridor score The corridor metric calculates the deviation between two signals by means of corridor fitting. The two sets of corridors, the inner and the outer corridors, are defined along the mean curve. If the eva
48、luated curve, C, is within the inner corridor bounds, a score of “1” is given and if it is outside the outer corridor bounds, the score is set to “0”. The assessment declines from “1” to “0” between the bounds of inner and outer corridors resulting in three different rating zones as shown in Figure
49、2. The compliance with the corridors is calculated at each specific time, t, and the final corridor score, Z, of a signal is the average of all scores, Z(t), at specific times, t. Figure 2 Rating zones of the corridor metric (corridors of constant width) 9 The philosophy of the ISO approach is to use a narrow inner corridor and a wide outer corridor. 14It limits the number of “1” ratings to only good corre
