1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 14794:2011Heavy commercial vehicles and buses Braking in a turn Open-loop test methodsBS ISO 14794:2011 BRITISH STANDARDNational forewordThis British Standard is the UK im
2、plementation of ISO 14794:2011. It supersedes BS ISO 14794:2003 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee AUE/15, Safety related to vehicles.A list of organizations represented on this committee can be obtained on request to its secretary.This pu
3、blication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. BSI 2011 ISBN 978 0 580 72783 2 ICS 43.020 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under t
4、he authority of the Standards Policy and Strategy Committee on 31 March 2011.Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 14794:2011Reference numberISO 14794:2011(E)ISO 2011INTERNATIONAL STANDARD ISO14794Second edition2011-02-15Heavy commercial vehicles and buses Braking in
5、a turn Open-loop test methods Vhicules utilitaires lourds et autobus Freinage en virage Mthodes dessai en boucle ouverte BS ISO 14794:2011ISO 14794:2011(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but
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10、9 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2011 All rights reservedBS ISO 14794:2011ISO 14794:2011(E) ISO 2011 All rights reserved iiiContents Page Foreword iv Introduction.v 1 Scope1 2 Normative references1 3 Principle .1 3.1 Test objectives.1 3.2 General condit
11、ions1 4 Reference system2 5 Variables.2 6 Measuring equipment .3 7 Test conditions 3 8 Tests .3 8.1 General .3 8.2 Brake temperature.3 8.3 Initial driving condition.4 8.4 Application of braking.4 9 Data evaluation and presentation of results 5 9.1 General .5 9.2 Time histories 5 9.3 Brake applicatio
12、n.5 9.4 Reference variables and steady-state values.7 9.5 Characteristic values 7 Annex A (normative) Test report General data and test conditions .9 Annex B (normative) Test report Presentation of results10 Bibliography22 BS ISO 14794:2011ISO 14794:2011(E) iv ISO 2011 All rights reservedForeword IS
13、O (the International 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 co
14、mmittee has been 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 electro
15、technical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the me
16、mber bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identif
17、ying any or all such patent rights. ISO 14794 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 9, Vehicle dynamics and road-holding ability. This second edition cancels and replaces the first edition (ISO 14794:2003), which has been technically revised. BS ISO 14794:2011
18、ISO 14794:2011(E) ISO 2011 All rights reserved vIntroduction The main purpose of this International Standard is to provide repeatable and discriminatory test results. The dynamic behaviour of a road vehicle is a very important aspect of active vehicle safety. Any given vehicle, together with its dri
19、ver and the prevailing environment, constitutes a closed-loop system that is unique. The task of evaluating the dynamic behaviour is therefore very difficult since the significant interaction of these driver-vehicle-environment elements is each complex in itself. A complete and accurate description
20、of the behaviour of the road vehicle must necessarily involve information obtained from a number of different tests. Since this test method quantifies only one small part of the complete vehicle handling characteristics, the results of these tests can only be considered significant for a correspondi
21、ngly small part of the overall dynamic behaviour. Moreover, insufficient knowledge is available concerning the relationship between overall vehicle dynamic properties and accident avoidance. A substantial amount of work is necessary to acquire sufficient and reliable data on the correlation between
22、accident avoidance and vehicle dynamic properties in general and the results of these tests in particular. Consequently, any application of this test method for regulation purposes will require proven correlation between test results and accident statistics. BS ISO 14794:2011BS ISO 14794:2011INTERNA
23、TIONAL STANDARD ISO 14794:2011(E) ISO 2011 All rights reserved 1Heavy commercial vehicles and buses Braking in a turn Open-loop test methods 1 Scope This International Standard specifies open-loop test methods for determining the effect of braking on the course-holding and directional behaviour of h
24、eavy vehicles or heavy vehicle combinations when braking is accomplished using the service-brake system, or the retarder or engine brake only. This International Standard is applicable to heavy vehicles i.e. commercial vehicles, commercial vehicle combinations, buses and articulated buses as defined
25、 in ISO 3833 covered by Categories M3, N2, N3, O3 and O4 of UNECE (United Nations Economic Commission for Europe) and EC vehicle regulations. These categories pertain to trucks and trailers with a maximum mass above 3,5 t and to buses and articulated buses with a maximum mass above 5 t. 2 Normative
26、references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3833, Road vehicles Types Terms an
27、d definitions ISO 8855, Road vehicles Vehicle dynamics and road-holding ability Vocabulary ISO 15037-2:2002, Road vehicles Vehicle dynamics test methods Part 2: General conditions for heavy vehicles and buses 3 Principle 3.1 Test objectives The primary objective of these test methods is to determine
28、 the effect of braking on the course-holding and directional behaviour of heavy vehicles. Constant longitudinal velocity and a steady-state circular path of a given radius define the initial conditions. The brake system is then applied in a step-wise manner. The control inputs and the vehicle respon
29、ses are measured and recorded during the test. From the recorded signals, characteristic values are calculated. 3.2 General conditions The applicable provisions for general test conditions specified in ISO 15037-2 shall apply, with the modifications and additions as indicated in the following clause
30、s. BS ISO 14794:2011ISO 14794:2011(E) 2 ISO 2011 All rights reserved4 Reference system The variables of motion used to describe the effect of braking on course-holding and directional behaviour of the vehicle relate to the intermediate axis system (X, Y, Z) (see ISO 8855). For the purposes of this I
31、nternational Standard, the reference point shall be the centre of gravity of the vehicle unit. NOTE This provision overrides the similar provision of ISO 15037-2. 5 Variables The following variables shall be determined. a) For single-unit vehicles or for the first vehicle unit of a vehicle combinati
32、on: lateral acceleration, aY; longitudinal acceleration, aX; brake-application signal; longitudinal velocity, vX; steering-wheel angle, H; yaw velocity, . b) For vehicle combinations: articulation angles, , or angular velocity of articulation angles between adjacent vehicle units. c) For tests using
33、 the service-brake system: brake pressure at the outlet of the master cylinder or in a brake circuit that activates at least one of the front wheel brakes, pB, or brake-pedal position, sB, if brake pressure is not the signal that activates the brake system as, for example, in the case of electronic
34、brake systems. In addition, the following variables should be determined. d) For the first vehicle unit: wheel rotational speeds, i, i=1,n, sideslip angle, . e) For trailing units: lateral acceleration, aY, yaw velocity, , wheel rotational speeds, i, i=1,n, sideslip angle, . Other variables which ma
35、y be determined are given in ISO 15037-2. BS ISO 14794:2011ISO 14794:2011(E) ISO 2011 All rights reserved 36 Measuring equipment The measuring and recording equipment shall be in accordance with ISO 15037-2. Typical operating ranges and recommended maximum errors for the transducer and recording sys
36、tems of the variables not given in ISO 15037-2 are shown in Table 1. Table 1 Variables, typical operating ranges and recommended maximum errors Variable Range Recommended max. error of combined transducer and recorder system Brake pressure in air systems 0 kPa to 1 500 kPa 15 kPa Brake pressure in h
37、ydraulic systems 0 MPa to 30 MPa 0,3 MPa Brake-pedal position, if rotational 0 to 45 0,5 Brake-pedal position, if translational 0 m to 0,2 m 0,001 m Wheel rotational speed 0 /s to 6 000 /s 5 /s 7 Test conditions Limits and specifications for the ambient and the vehicle test conditions shall be in ac
38、cordance with ISO 15037-2. Although the standard condition specified by ISO 15037-2 is a dry clean road, because it could be particularly useful, this test may be conducted on other relevant surfaces with appropriate adjustments to levels and increments of accelerations. 8 Tests 8.1 General The brak
39、ing-in-a-turn test consists of a series of test runs, in each of which the vehicle is initially placed in a steady-state turn of specified speed and lateral acceleration and is then subjected to a rapid application of either the service-brake system or the retarder or engine brake. In conducting the
40、 braking-in-a-turn test, the general test specifications shall be in accordance with ISO 15037-2. Test runs shall be conducted using both left- and right-hand turns. All the data may be taken in one direction followed by all the data in the other direction. As an alternative, data may be taken succe
41、ssively in each direction for each acceleration level proceeding from the lowest to the highest level. The method chosen shall be noted in the general data. (See Annex A.) The series of tests should be performed at least three times. 8.2 Brake temperature An acceptable range for initial brake temper
42、ature shall be specified for tests in which braking is to be accomplished using the service brakes. Prior to each individual run of such tests, the brakes shall be warmed up or allowed to cool as required such that the initial brake temperatures are within the specified range. The initial temperatur
43、e of the brakes shall be reported in the general data. (See Annex A.) BS ISO 14794:2011ISO 14794:2011(E) 4 ISO 2011 All rights reserved8.3 Initial driving condition The initial driving condition for this test method shall be in accordance with that given for steady-state circular runs in ISO 15037-2
44、. In this initial condition, the vehicle shall be steered such that the reference point of the vehicle moves along the desired circular path. The standard radius of this path is 100 m. Optionally, larger or smaller radii (to a minimum of 30 m) may be used. However, as it is known that the significan
45、ce of the results and the ability to discriminate between different vehicles increase with increasing test speed, testing should be carried out on larger radii at appropriately higher speeds. The initial lateral acceleration of the vehicle, or of the first vehicle unit of vehicle combinations, shall
46、 be appropriate to the test surface. The recommended lateral acceleration is 3 m/s2on the standard surface. However, for safety reasons, the maximum lateral acceleration should not be more than 75 % of the estimated rollover limit or of the estimated road adhesion limit. The initial lateral accelera
47、tion level shall be noted in the test report. Outriggers should be used in order to prevent rollover. When the initial steady-state driving condition has been reached, the steering wheel shall be held at a constant angle by a mechanical device; alternatively, it shall be firmly held by the driver. T
48、he steering wheel shall be held fixed until the test run is completed. 8.4 Application of braking 8.4.1 General The braking effort in the initial test run shall correspond to a mean longitudinal acceleration of 1 m/s2. Subsequently, braking shall be increased by increments of not more than 1 m/s2. I
49、f the results vary rapidly with longitudinal acceleration, or when operating on low-friction surfaces, smaller increments should be selected. 8.4.2 Test procedure 8.4.2.1 Service-brake systems Release the accelerator pedal as quickly as possible and apply the brakes in accordance with 9.3. For vehicles with manual transmissions, conduct the test in the highest gear compatible with the conditions of the test. The clutch may be disengaged immediat
