BRITISH STANDARD AUTOMOBILE SERIES BS AU 228 2 1989 ISO 8721 1987 Impact tests on road vehicles — Part 2 Specification for measurement techniques using optical instrumentation [ISO title Road vehicles[.]
BRITISH STANDARD AUTOMOBILE SERIES BS AU 228-2: 989 ISO 8721 :1 987 Impact tests on road vehicles — Part 2: Specification for measurement techniques using optical instrumentation [ISO title: Road vehicles — Measurement techniques in impact tests — Optical instrumentation] UD C 62 1 : 62 / 1 BS AU 228-2:1 989 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Automobile Standards Committee (AUE/- ) to Technical Committee AUE/7 upon which the following bodies were represented: Association for Consumer Research Automobile Association Child Accident Prevention Trust Consumer Policy Committee of BSI Department of Transport (Highways) Department of Transport (Transport and Road Research Laboratory) Institute for Consumer Ergonomics Ltd Man- made Fibres Producers’ Committee Medical Research Council Ministry of Defence Motor Industry Research Association National Automobile Safety Belt Association Royal Automobile Club Royal Society for the Prevention of Accidents Society of Motor Manufacturers and Traders Ltd University of Birmingham This British Standard, having been prepared under the direction of the Automobile Standards Committee, was published under the authority of the Board of BSI and comes into effect on 31 March 989 © BSI 01 - 2000 The following BSI references relate to the work on this standard: Committee reference AUE/7 Draft for comment 86/77884 DC ISBN 80 685 X Amendments issued since publication Amd No Date of issue Comments BS AU 228-2:1 989 Contents Page Committees responsib le National foreword ii Scope and field of application Reference D efinitions Performance Annex D istortion index measurement methods Figure — Target for distortion index determination Pub lications referred to © BSI 01 - 000 Inside front cover Inside back cover i BS AU 228-2:1 989 National foreword This Part of BS AU 228 has been prepared under the direction of the Automobile Standards Committee and is identical with ISO 8721 : 987 “Road vehicles — Measurement techniques in impact tests — Optical instrumentation”, published by the International Organization for Standardization (ISO) Terminology and conventions The text of the International Standard has been approved as suitable for publication as a British Standard without deviation Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following The comma has been used as a decimal marker In British Standards it is current practice to use a full point on the baseline as the decimal marker Wherever the words “International Standard” appear, referring to this standard, they should be read as “Part of BS AU 228” Cross-reference International Standard C orresponding British Standard ISO 6487: 987 BS AU 228 Impact tests on road vehicles Specification for measurement techniques and general instrumentation Part : 988 (Identical) A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages to 4, an inside back cover and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii © BSI 01 - 2000 BS AU 228-2:1 989 Scope and field of application This International Standard defines performance criteria for an optical data channel used in impact tests on road vehicles, when numerical time and space data are taken from the images to analyse impact test results The requirements are to facilitate comparison between results obtained by different laboratories The annex gives a method of measuring the distortion index as a quality parameter of the optical data channel using a standard target, and, as an alternative, an indirect method This International Standard complements ISO 6487 which covers non-optical instrumentation used in impact tests on road vehicles Reference ISO 6487, Ro ad vehicles — Techniq ues o f m easurem ent in im p act tes ts — Instrum entatio n 3.6 imaging rate frequency of renewal of information for a given point expressed in renewals per second or in images per second when all the points of the image are renewed simultaneously Performance The performance of the optical data channel shall be evaluated initially to establish performance levels; this evaluation shall be repeated whenever the system is modified to an extent which could cause a change in accuracy 4.1 Distortion index The distortion index shall be assessed using the photographic target and procedure described respectively in A.1 and A.1 of the Annex It shall be evaluated as indicated in A.1 The distortion index shall not exceed % 4.2 Time base A time base is required It shall permit For the purposes of this International Standard, the determination of the time between recorded events to an accuracy of the reciprocal of the imaging rate following definitions apply or % of the actual time, whichever is greater 3.1 Definitions optical data channel 1) system composed of an image-taking device (e.g a camera), a recording medium for these images (film, disc, magnetic tape, etc.) and a system for analysing the images, including any analysis procedure and data correction that modify the content of the data 3.2 distortion index quality parameter of the optical data channel 3.3 analysis system system to measure and collect the coordinates of target points as a function of time 3.4 time-base system device allowing determination of the time interval elapsing between any two recorded events 3.5 time origin identification device device to identify the instant chosen as the time origin, usually the beginning of the impact 4.3 Time origin identification device The accuracy of the device shall be equal to the reciprocal of the imaging rate 4.4 Imaging rate The imaging rate shall be left to the user’s discretion, taking account of all factors including: — the goal to be attained; — the limitations due to the equipment (e.g blur); — the need to combine data from several image-taking devices and from electronic recordings of the impact test The user’s choice shall be guided by the distance the recorded point moves between two images analysed This distance shall not exceed any accuracy requirement there may be on determination of position 4.5 Reference length A length calibration shall be carried out which permits determination of lengths within any requirements there may be on accuracy In the absence of such requirements, it is recommended that determinations of length to within ± % of the diagonal of the picture should be possible 1) The influence of the operator on accuracy has not been taken into account during the development of this International Standard © BSI 01-2000 BS AU 228-2:1 989 Annex Distortion index measurement methods (This annex forms an integral part of the Standard ) The diameter, d , and the standard deviation, respectively shall be calculated taking the 40 diameter values following equations: di s , into account from the A.1 Standard target method A.1 Test target A rectangular target of type and dimensions in conformity with the figure shall be used where This target shall be divided into four parts by N = 40 j oining the centre points of the two opposite sides In each quadrant thus obtained, and at the target centre, circles 400 ± mm in diameter shall be drawn The five circles shall be marked on their N circumferences with reference marks, this where defining eight diameters for each, and The distortion index is equal to the ratio of the hence 40 diameters for the whole target standard deviation, A.1 Test method s d – = 39 s , to the mean diameter, d , i e - The target shall be recorded full- frame by the image- taking device which forms one element of the optical data channel to be tested A.2 Alternative (indirect) method The image- recording medium to be used for Other targets with different sizes or patterns of calibration shall be of the same type and quality as reference marks may be used, in which case the user those used for impact testing It shall be analysed shall determine the distortion index indirectly using the analysis system The coordinates of the marks of each diameter di shall be measured on the same frame while the coordinates of the marks of different diameters shall be measured on consecutive analysed images A.1 Calculation of results The 40 diameters di y y There is then also a need to show that the indirect method gives results equivalent to those using the target specified in A.1 This may be of advantage when for instance a target with a rectangular pattern of reference marks is used for the determination of lens corrections, which are needed in case of some wide- angle lenses shall be calculated between two points, P and Q, from the equation di = [( x x P – Q) + ( P – Q) 0, ] © BSI 01 - 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