1、_SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising theref
2、rom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2010 SAE International All rights reserved. No part of this publication ma
3、y be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside US
4、A) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J2909_201005SURFACEVEHICLERECOMMENDEDPRACTICEJ2909 MAY2010 Issued 2010-05Light Vehicle Dry Stop
5、ping Distance RATIONALENot applicable. 1. SCOPE This document establishes best practices to measure vehicle stopping distance on dry asphalt in a straight path of travel intended for the purpose of publishing stopping distance by manufacturers and media organizations. It is recommended that the test
6、 method within be adopted for all vehicles less than 10 000 lb (4536 kg) GVWR. This procedure is typically used with initial speeds of 100 km/h and 60 mph, but other speeds may be used.1.1 Purpose This vehicle stopping distance procedure outlines methodology to provide consistent results within a te
7、st facility or test site, using best known practices including standards for test equipment, vehicle and tire guideline preparation, and dry asphalt surface friction compensation.2. REFERENCES 2.1 Applicable Documents The following publications form a part of this specification to the extent specifi
8、ed herein. Unless otherwise indicated, the latest issue of SAE publications shall apply. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.SAE J299 Stopping
9、Distance Test Procedure 2.1.2 ISO Publications Available from American National Standards Institute, 25 West 43rd Street, New York, NY 10036-8002, Tel: 212-642-4900, www.ansi.org.ISO21994 2007 Passenger Cars Stopping Distance at Straight Line Braking with ABS Open Loop Test Method SAE J2909 Issued M
10、AY2010 Page 2 of 192.1.3 ATSM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.orgE445 Standard Test method for Stopping Distance on Paved Surfaces Using a Passenger Vehicle Equipped with Full-Scale Ti
11、res E1136 Standard Specification for a Radial Standard Reference Test Tire E1337 Standard Test Method for Determining Longitudinal Peak Braking Coefficient of Paved Surfaces Using a Standard Reference Test Tire F2493 Standard Specification for P225/60R16 97S Radial Standard Reference Test Tire 2.1.4
12、 United States Government Federal Safety Standards Available from U.S. Superintendent of Documents, Washington, DC 20402-0001, Tel: 866-512-1800, http:/bookstore.gpo.gov.Motor Vehicle Safety Standard No. 105 (FMVSS105); Hydraulic and Electric Brake Systems Motor Vehicle Safety Standard No. 135 (FMVS
13、S135); Passenger Car Brake Systems 3. DEFINITIONS 3.1 Asphalt Surface Known as asphalt concrete, it is a composite of asphalt binder and aggregate, mixed and compacted to form a road bed.3.2 ABS Anti Lock Brake System - a collection of sensing and control hardware installed on a vehicle to prevent w
14、heel lockup during brake application. (ASTM F 1649) 3.3 GVWR Gross Vehicle Weight Rating - the maximum amount allowable total weight of a vehicle.3.4 Tire Burnishing A break-in condition of the tires tread surface completed under braking and/or miles driven prior to testing.3.5 OEM-Original Equipmen
15、t Manufacture Reference to OEM applies to vehicle manufacturers specifications. 3.6 Surface Temperature The temperature of the test surface at the time of the test. 3.7 Adjusted Stopping Distance The corrected stopping distance adjusted for actual initial speed, surface friction and temperature. 3.8
16、 Tanh SAE J2909 Issued MAY2010 Page 3 of 19The mathematical hyperbolic tangent function. 4. INSTRUMENTATION AND RECORDING 4.1 Vehicle Parameters The minimum vehicle data channels required to conduct stopping distance testing are listed in the first column of Table 1 accompanied by suggested full sca
17、le ranges and sensor accuracy. TABLE 1 - VEHICLE PARAMETERS Variable Sensor Range Sensor Accuracy Longitudinal Velocity 0 to 150 km/h 0.5 km/h Longitudinal Distance 0 to 100 m 0.2%Brake Pedal Force Trigger 0 to 700 N 5 N It shall be ensured that transient vehicle pitch angle changes during braking d
18、o not affect the measurement of the velocity and distance variables for the chosen transducer system. All transducers shall be calibrated according to the manufacturers instructions. The transducer manufacturers recommended application software and firmware version shall be used. If parts of the mea
19、suring system used can be adjusted, such calibration shall be performed immediately before the beginning of the tests. 4.1.1 Optional Vehicle Parameters Optional vehicle parameters and their corresponding full scale range and sensor accuracy are given in Table 2. These parameters may be useful for f
20、urther understanding of results and associated variation in results. TABLE 2 - OPTIONAL VEHICLE PARAMETERS Vehicle Data Channel Sensor Range Sensor Accuracy Brake Lining Temperatures 0 to 200 C 1.0 CBrake Master Cylinder Pressure 0 to 20 000 kPa 100 kPa Brake Caliper Pressures 0 to 20 000 kPa 100 kP
21、a Road Surface Temperature 0 to 75 C 0.5 CAmbient Temperature 0 to 50 CLongitudinal Accelerometer 0 to 1.2 G 0.01 G Brake Pedal Force 0 to 1000 N (1500 N max) 5 N 4.2 Data Recording Recommend use of digital data acquisition system with the capability to scan all data channels at a minimum sample rat
22、e of 100 Hz with the same time reference. 5. TEST CONDITIONS 5.1 Test Vehicle Preparation 5.1.1 Brake Burnish Condition new brake hardware with 200 stop FMVSS135 brake burnish (see Appendix C). Mileage accumulation, typically in the range of 2500 miles (not to exceed 50% highway), is another method
23、to burnish new brake hardware equivalent to FMVSS135 brake burnish for the purpose of stopping distance testing. Vehicles with regenerative braking technology may require more mileage accumulation. Mileage accumulation up to 5000 miles of normal city/highway driving has typically not resulted in exc
24、essive wear of the brakes provided that the brakes have not been overheated. SAE J2909 Issued MAY2010 Page 4 of 195.1.2 Tire Burnish Condition new tires by performing ten 100 km/h ABS stops on dry asphalt. Mileage accumulation exceeding 2500 miles (500 miles) (not to exceed 50% highway) plus three 1
25、00 km/h ABS stops on dry asphalt is another method to burnish new tires. The tire parameters and tread widths should show a steady wear condition with a tread depth of at least 90% of the original value across the whole breadth of the tread and around the whole circumference of that of the new tire.
26、 Tire burnish is a critical factor in determining vehicle stopping distance and when comparing stopping distance between vehicles. See Appendix A for examples of tire burnish effects on stopping distance due to mileage accumulation or consecutive ABS stops. 5.1.3 Brake Lining Temperature Install the
27、rmocouples at each corner of the vehicles at the center of the most heavily loaded brake lining shoe or pad following instructions in FMVSS135. The purpose of measuring brake lining temperatures is to establish initial brake lining temperatures between 80 and 120 C before each ABS brake stop. This c
28、an be accomplished by using brake snubs from 80 to 30 km/h at 0.2 G deceleration. For cases where measuring brake lining temperatures is not practical, special attention will be required to ensure that the brake linings are not overheated and that identical brake cooling procedures are used when com
29、paring stopping distances between vehicles. 5.1.4 Tire Inflation Pressure Tire inflation pressure shall be set to OEM specifications or placard pressure to within 3.5 kPa (0.5 psi). Inflation pressures shall be set to the OEM placard with the tires in their cold state at approximately test ambient t
30、emperature. The inflation pressure will then change as the vehicle is driven. Do not adjust the inflation pressure of a warm tire. 5.1.5 Vehicle Test Weight Vehicle weight shall be set at curb weight with the fuel level set between and full capacity. Stopping distance testing shall occur with driver
31、 and test instrumentation only. The total load of the driver plus instrumentation should not exceed 150 kg. If the vehicle is to be tested in any other load condition (e.g., GVWR), then the additional payload shall be evenly distributed such that cross-axle variations do not exceed 50 kg. 5.1.6 Vehi
32、cle Operational Test Conditions Vehicles with an automatic transmission should have the gear selector in highest forward gear during stopping distance testing. Vehicles with manual transmissions should disengage the clutch or shift into neutral before applying brake pedal during stop. All vehicle op
33、enings (windows, hood, trunk, etc.) should be closed. All vehicle accessories should be turned off, except for headlights if required for test track operation.On vehicles equipped with a vacuum booster, the brake force depends on the vacuum level of the vacuum brake booster. Therefore, a sufficient
34、vacuum shall be ensured at the beginning of braking. To achieve a sufficient vacuum level, it is recommended to move the vehicle in a drag operation for a short time during the cooling phases between individual braking events. When doing so, the accelerator pedal can be released for at least 10 s at
35、 high engine speed (e.g., by engaging a suitable gear). Afterwards, the brake shall not be operated before the next measurement because this will reduce the vacuum level that was established before. 5.2 Test Track Conditions 5.2.1 Test Track Ambient and Surface Temperature The surface temperature of
36、 the test track shall be between 5 and 55 C and its variation during a sequence of measurements shall not exceed 10 C. Ambient temperature should be between 5 and 40 C and its variation during a sequence of measurements should not exceed 10 C. Surface friction is normalized by the test surface tempe
37、rature outlined in 5.2.2. Record the ambient and road surface temperatures at time of test. For tires intended for summer only use, ambient temperature shall be between 10 and 55 C and surface temperature of the test track shall be between 10 and 55 C. SAE J2909 Issued MAY2010 Page 5 of 195.2.2 Test
38、 Track Road Surface Friction The road surface friction coefficient should be measured with an ASTM E 1136 standard reference tire in accordance with ASTM E 1337 method, at a speed of 64 km/h (40 mph) at the time of the test. The purpose of this measurement is to compensate for changes in road surfac
39、e friction due to changes in environmental conditions such as ambient temperature and road surface temperature. Examples of dry asphalt surface friction variation are shown in Appendix B for both old (10 years) and new (1 year) asphalt surfaces. An example regression of road surface friction based o
40、n road surface temperature is shown in Figure 1. Road surface friction can be predicted as a function of road surface temperature by using the polynomial equation shown in Figure 1. Note that a surface friction and a temperature will have to be selected as a reference point and surface friction corr
41、ections will then be made to this reference point. See Appendix E for an example.Surface Friction Vs. Surface Temperature Measured With 14“ Standard Reference Test Tire E1136y = -0.0000001476x3+ 0.0000308145x2- 0.0023675387x + 0.9852362928R2= 0.74797162000.90.910.920.930.940.950.960.970.980.9910 102
42、030405060Road Surface Temperature in Degrees CRoadSurface FrictionFIGURE 1 - SURFACE FRICTION VERSUS SURFACE TEMPERATURE EXAMPLE The purpose of measuring road surface friction is to be able to provide a common reference point for comparing stopping distances between vehicles tested at different time
43、s. Alternative methods may be considered to establish this common reference point such as using a common reference vehicle with an accompanying reference tire that has had the same brake burnish and tire burnish described in this procedure. Special attention will be required to ensure the tires used
44、 for this purpose are equivalent, similar to methods used for the industry standard reference test tire. 5.2.3 Test Track Road Grade The gradient of the test surface to be used shall not exceed 1% longitudinal inclination and 2% transversal inclination when measured over any distance interval betwee
45、n that corresponding to the vehicle track and 25 m. Special attention will be required to ensure each test vehicle was measured with same road grade when comparing stopping distances between vehicles. SAE J2909 Issued MAY2010 Page 6 of 195.2.4 Other Test Track Conditions The ambient wind velocity in
46、 the direction of travel shall not exceed 10 km/h or, if the wind velocity ranges between 10 km/h and 18 km/h maximum, alternate runs in both driving directions. Special attention will be required to ensure that each test vehicle was measured with same wind speed and direction when comparing stoppin
47、g distances between vehicles.6. STOPPING DISTANCE TEST PROCEDURE 6.1 Verify all instrumentation is functioning properly. 6.2 Drive to the test track. 6.3 Establish initial brake temperatures between 80 and 120 C using brake snubs from 80 to 30 km/h at 0.2 G deceleration.6.4 Accelerate vehicle 5 to 8
48、 km/h above target test speed. Maintain this speed and prepare instrumentation for test. Suggested range of target test speed is 80 to 120 km/h. 6.5 Release accelerator pedal and coast in gear to the target test speed. If the vehicle has a manual transmission, disengage clutch or shift into neutral
49、to avoid stalling vehicle at low vehicle speed. 6.6 For vehicles equipped with ABS, activate ABS by using a spike brake pedal apply. The brake pedal force must be high enough to guarantee ABS control throughout the entire stop after the initial ABS activation. The spike brake pedal apply rate should be a minimum of 6000 N per second and shall not exceed 12 000 N per second within the first 0.1 s after exceeding a
