BRITISH STANDARD AUTOMOBILE SERIES BS AU 164 1977 ISO 3784 1976 Specification for Measurement of impact velocity in collision tests on road vehicles UDC 629 113 614 864 531 66 531 112 082 L ic e n s e[.]
Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 49: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BRITISH STANDARD AUTOMOBILE SERIES Specification for Measurement of impact velocity in collision tests on road vehicles UD C 62 1 : 61 864: 66: 1 82 BS AU 164:1977 ISO 3784:1976 Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 49: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 64 : 977 Fore word Road vehicles — This British Standard was prepared under the authority of the Automobile Measurement of impact velocity in collision tests Standards Committee and is identical with ISO 3784: 976 “ ”, prepared by Technical Committee ISO/TC 22, Road vehicles, of the International Organization for Standardization Te rmino lo gy and conve ntio ns The text of the International Standard has been accepted as suitable for publication, without deviation, as a British Standard Certain terminology and conventions are used, however, that are not strictly appropriate in a British Standard, and attention is therefore drawn to the following Wherever the words “International Standard”, relating to this publication, appear, they should be interpreted as “British Standard” The comma has been used throughout as a decimal marker In British Standards it is current practice to use a full point (a full stop on the baseline) as the decimal marker 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 C o mp liance with a British S tand ard doe s not o f itse lf co nfe r immunity fro m le gal ob ligations S ummary o f p age s This document comprises a front cover, an inside front cover, pages i and ii, pages to and a back cover This standard has been updated (see copyright date) and may have had This British Standard, having been prepared under the amendments incorporated This will be indicated in the amendment table on the inside front cover direction of the Automobile Standards Committee, was published under the authority of the Executive Board on Ame ndme nts issue d since p ub lication 31 January 977 © BSI 02- 2000 The following BSI references relate to the work on this standard: Committee reference AUE/- /1 /6 Draft for comment 75/73852 DC IS B N 80 9 Amd No Date of issue Comments Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 49: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 164:1977 Contents Page Foreword Scope and field of application Performance Methods of measurement Annex Typical methods of measurement of velocity © BSI 02 - 000 Inside front cover i Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 49: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI ii blank Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 49: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 64 : 97 S cop e and fie ld of ap p lication Pe rformance This International Standard lays down the accuracy The accuracy of velocity measurement shall of measurement of the impact velocity in collision be ± % tests on road vehicles In addition, some typical The impact velocity measurement shall be made methods suitable for the measurement of this within 0,2 s prior to impact impact velocity are described in the Annex These methods are intended to facilitate the comparison of data obtained in similar tests by different Typical methods for measuring impact velocity are laboratories described in the Annex Other methods may be used provided they meet the requirements of and 2.1 2.2 Me thods of me asure me nt 2.1 © BSI 02-2000 2.2 Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 49: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 64:1 977 A further variation involves attaching the transmitter directly to a rear wheel of the vehicle instead of the fifth wheel In this case it is difficult Velocity measurement methods can be classified in to calibrate the system and there must be no tyre slip at the road surface However, the calibration three general categories: must be carried out carefully a) Doppler effect method; A.3 Measurement of time needed to cover a b) summation of the units of distance in a given given distance time (fifth wheel method); The following typical methods are in general use: c) measurement of the time needed to cover a A.3.1 System using a photoelectric barrier given distance A transmitter and a receiver are located on either A.1 Doppler effect method side of a shutter in a U-shaped arrangement fixed This effect utilizes the apparent frequency variation rigidly on the vehicle of a wave in motion This variation is proportional to the speed of the body in relation to the observer and The transmitter consists of a lamp emitting a light beam with essentially parallel rays which is governed by the following formula: illuminate a photoelectric cell which constitutes the v f0 receiver f = v1 – v2 Successive cutting of the light beam by the arms of the U start and stop a digital chronometer where The transmitter is placed approximately m from f is the apparent frequency; the receiver A diaphragm can be placed on the f0 is the emitted frequency; receiver to limit parasitic reflections v is the speed of the wave emitted in an The cutting of the beam is effected by means of a ambient medium; shutter in a U shape mounted on the side of the v is the speed of the vehicle vehicle This mounting should be very rigid in order to avoid any deflection tending to spread or tilt the The emitted electromagnetic waves which are two arms, thus altering their separation The generally used are situated in two different spacing between the arms of the U should be known wavelength bands: within approximately 0,2 % The U is painted matt a) centimetric waves: radar with an accuracy that black to avoid any reflections is only of the order of %; The passage of the first arm of the shutter through b) micrometric waves: the laser the barrier produces a variation in voltage at the The laser system, more perfected than the radar amplifier This difference in potential applied at system, permits measurements with an error less entrance A of a digital chronometer whose time base than % It should be noted, however, that the cost is regulated to 10–5 s, initiates the time recording of this type of equipment is very high When the second arm obscures the receiver, it A.2 Summation of the units of distance in a produces a new voltage variation at entrance B of given time (fifth wheel method) the chronometer, stopping the recording A wheel attached to the rear of the vehicle by an The accuracy with this system is very high and can articulated yoke is maintained in contact with the be better than % ground by a spring Mounted axially on this wheel is A.3.2 System with induction proximity sensor a disc containing slits spaced regularly around the The receiver is of a cylindrical form and has circumference A photoelectric transmitter-receiver dimensions of approximately 60 mm in length with system is located on either side of the disc a diameter of 11 mm The receiver includes an Passage of the slits in front of a photoelectric cell electronic amplifier within the sensor activates a series of impulses corresponding to the The sensor is an oscillator which is stopped when a distance covered The summation of these data metallic body passes in front of the active extremity permits direct reading from a galvanometer, or a of the receiver The power supply required by this recording on an ultra-violet oscillograph Careful receiver 24 V d.c The output current can machining permits an accuracy of the order of % attain 40ismA from a receiver having a resistance An alternative method is to use an induction of 600 7, with a response time of 150 È s A digital proximity sensor in place of the photoelectric chronometer is started and stopped by the metallic receiver Its advantages are simpler assembly and body passing close by resistance to weather Annex Typical methods of measurement of velocity © BSI 02-2000 Li cen sed Copy: Lon d on Sou th Ban k U n i versi ty, Lon d on Sou th Ban k U n i versi ty, Sat Dec 09 01 : 49: 35 G M T+00: 00 2006, U n trol l ed Copy, (c) BSI BS AU 64 : 97 The accuracy of this system is better than % Durability is also very good due to the fact that there is no direct contact This procedure can only be utilized if the vehicle is perfectly guided, the maximum detection distance being mm Equipment utilizing electromagnetic beam barriers Two centimetric transmitters and two receivers are located on each side of the test track at an interval of at least m Passage of the vehicle interrupts the beams Interruption of the first beam actuates the circuit of the chronometer; interruption of the second stops the circuit The major drawback of this system is its high cost Assuming that the axes of the beams from the two transmitters are perfectly parallel, the principal source of error comes from measurement of the spacing of the receivers It is considered that this system provides an accuracy better than % Cinematographic procedure The impact velocity can also be measured by use of high-speed cinematography, of the order of 500 to 000 images per second A clearly visible target is placed on the vehicle and its displacement in relation to a ground target is measured on a certain number of film images The time is derived on the basis of the camera time based on an impression on the margin of the film of a small flash every 0,01 s or 0,001 s, contingent on the film speed chosen To obtain the time measurement, another method can be utilized by filming a disc operated by a small synchronous motor The accuracy of this procedure depends on: a) the grain of the film, which can cause blurring of the image; b) the time base of the camera A A © BSI 02-2000 Analysis of the films must be effected with equipment permitting positioning of the film within ± 15 È m, a resolution of 1/20 mm in X and Y and 22 of angle in Ú In order to minimize parallax errors, the cameras must be positioned as far away as possible and be equipped with long focal length lenses compatible with the field to be filmed To obtain accuracies of %, very detailed attention to equipment and technique is required System of plates actuated by the vehicle wheels ½ A A Metallic plates Two flexible metallic plates, separated from each other and arranged across the test track, are put in contact by the pressure of the front wheels of the vehicle Coupled with a direct current generator, this contact actuates a digital chronometer The passage of the rear wheels re-closes the contact and stops the chronometer Knowing the time required to cover a given distance, i.e the wheelbase of the vehicle, it is simple to derive the velocity This procedure is not very precise owing to the disparity of the pressures engendered by the front wheels and the rear wheels This drawback leads to the use of a variation of this procedure which consists in placing two identical sets of plates across the track The actuation and stopping of the chronometer are then caused by the front wheels alone If the contact is subjected to repeated actuation and wear is not apparent, it is possible that after several tests the velocity measurement would be affected by erratic release A Pneumatic plates In this version, the receiver consists of a rubber tube closed at one end Passage of the vehicle over the tube produces a pressure variation, which actuates an electrical contact formed from a movable element and a stationary element Time measurement is achieved in the same manner as with the metallic plates equipment Li cen sed Copy: Lon d 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