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 entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, 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.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8512 FAX: (724) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1996 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICESubmitted for recognition as an American National Sta
4、ndardJ266ISSUEDJAN96Issued 1996-01STEADY-STATE DIRECTIONAL CONTROL TEST PROCEDURES FORPASSENGER CARS AND LIGHT TRUCKSForewordThis Document has not changed other than to put it into the new SAE Technical Standards BoardFormat.1. ScopeThis SAE Recommended Practice establishes consistent test procedure
5、s for determination ofsteady-state directional control properties for passenger cars and light trucks with single axles. Theseproperties include the gradients with respect to lateral acceleration of steering wheel angle, understeer/oversteer, sideslip, roll angle, and steering wheel torque; the gain
6、s with respect to steering wheel angle of yawvelocity, lateral acceleration, and sideslip; the characteristic speed or critical speed; and the total, steering, andtire compliances at the front and rear wheels.2. References2.1 Applicable PublicationsThe following publications form a part of this spec
7、ification to the extent specifiedherein. Unless otherwise specified, the latest issue of SAE publications shall apply.2.1.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J670eVehicle Dynamics TerminologySAE J2181Steady-State Circular Test Procedure for Tru
8、cks and BusesSAE Paper 670078The Influence of Vehicle Design Parameters on Characteristic Speed andUndersteer, R. T. Bundorf2.1.2 ISO PUBLICATIONSAvailable from ANSI, 11 West 42nd Street, New York, NY 10036-8002.ISO 4138:1982(E)Road vehiclesSteady state circular test procedureISO 7401:1988(E)Road ve
9、hiclesLateral transient response test methods2.2 Related PublicationsThe following publications are provided for information purposes only and are not arequired part of this document.2.2.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE Paper 760713The Corne
10、ring Compliance Concept for Description of Vehicle Directional ControlProperties, R. T. Bundorf and R. L. LeffertSAE J266 Issued JAN96-2-SAE Paper 741096A Primer on Nonlinear, Steady-State Vehicle Turning Behavior, R. W. Topping,October 1974SAE Paper 720473A New Laboratory Facility for Measuring Veh
11、icle Parameters Affecting Understeerand Brake Steer, A. L. Nedley and W. J. WilsonSAE Paper 741104Understanding Tire Intermix Through the Cornering Compliance Concept, R. L.Leffert, P. M. Riede, and R. E. Rasmussen2.2.2 ISO PUBLICATIONAvailable from ANSI, 11 West 42nd Street, New York, NY 10036-8002
12、.ISO 8855-1991Road vehiclesVehicle dynamics and roadholding vocabulary3. DefinitionsThe terminology used herein follows the standard definitions as found in SAE J670e.4. General4.1 Test MethodsFive test methods are described:Method 1Constant radius testMethod 2Constant steering wheel angle testMetho
13、d 3Constant speed/variable radius testMethod 4Constant speed/variable steer testMethod 5Response gain/speed testThe first four methods yield substantially similar data, but they differ in requirements for testing space, driverskill, and instrumentation. Methods 1 and 3 depend upon the path-keeping a
14、bility of the driver to minimizeinstrumentation requirements. Methods 2 and 4 use fixed steering wheel angle and measure path radius withinertial instruments. Method 5 utilizes the ratios of the various responses to steering wheel angle. Method 4 isgenerally run at 80 to 100 km/h. Method 5 is limite
15、d to the 0 to 0.4 g “linear range“ of vehicle operation, but canbe run at considerably higher speeds than the other methods. The data plot of Method 5 also demonstratesmost clearly the concepts of characteristic speed and critical speed, as defined in SAE J670e.4.2 Relationship to Other StandardsThi
16、s document is a superset of International Standard ISO 4138:1982(E)and a complement to International Standard ISO 7401:1988(E). Method 1 is the same as the proceduredescribed in ISO 4138. Method 4 is similar to the step/ramp steer input test protocol described in paragraph5.4 of ISO 7401. The test p
17、rocedures differ only in the amount of throttle applied, but the procedure describedherein is used to extract only steady-state vehicle characteristics, whereas ISO 7401 extracts only transientresponse characteristics. SAE J2181 OCT91 describes the test of Method 1 and Method 2 adapted for busesand
18、heavy trucks, including articulated vehicles.4.3 Theoretical Basis for the Test ProceduresThe path curvature of an automobile in steady turning at agiven speed (that is, in a given state of equilibrium, or trim) is determined by speed, steering wheel angle,wheelbase, and the elastic and kinematic ch
19、aracteristics of the front and rear steering systems, suspensions,and tires.In the absence of elastic and kinematic steer effectsfor example, at very low speedsthe Ackerman turnradius (Figure A1 in Appendix A) is defined geometrically by wheelbase and by front wheel and rear wheelsteer angles. At in
20、creasing speed, steady turning results in centrifugal force, which produces deflections insteering, suspension, and tire systems. As described in SAE Paper 670078, these include lateral forcedeflection steer, aligning torque deflection steer, roll steer, tire slip angles from lateral force and cambe
21、r force,etc. When expressed in degrees per g of lateral acceleration and lumped together, these “corneringcompliances“ produce steer angles and tire slip angles in front and rear which modify the Ackerman turnradius. Cornering compliances subtract from the front and rear Ackerman steer angles as sho
22、wn in Figure A1.Cornering compliances greater in the front than in the rear increase path radius from the Ackerman condition,and produce understeer, while cornering compliances greater in the rear than in the front reduce path radius,SAE J266 Issued JAN96-3-causing oversteer. The difference between
23、the total front and rear cornering compliance is called understeer/oversteer gradient, expressed in degrees per g. Likewise, the change in steering wheel angle required tomaintain a given radius with increasing lateral acceleration is called steering wheel angle gradient, the changein roll angle wit
24、h lateral acceleration is called roll angle gradient, etc.The test procedures described herein are designed to measure these various vehicle response gradients.The sensitivities of the vehicles responses to steer inputs are called yaw rate gain (degrees per second perdegree of steering wheel movemen
25、t), lateral acceleration gain (gs per degree of steering wheel motion),sideslip gain, etc. These can be calculated from the vehicle speed, steering wheel angle, steering ratio,wheelbase, and understeer/oversteer gradient, or they can be obtained directly from measured data.4.4 Equivalence of Test Pr
26、oceduresThe nature of any stable steady state is independent of the method bywhich it is achieved. Therefore, to obtain a desired set of steady-state trim conditions of speed, steering wheelangle, and turn radius, it is possible to hold any one of them constant, vary a second, and measure the third.
27、Thus one may use a constant radius test, in which speed is varied and steer angle is measured; a constantsteer angle test in which speed is varied and radius is measured; a constant speed variable radius test in whichradius is varied and steer angle is measured; or a constant speed variable steer an
28、gle test in which steer isvaried and radius is measured. All of these test methods will produce equivalent results, provided they spanthe same variation of speed-steer-radius steady-state conditions. In fact, one may in principle obtain anequivalent to any of the tests by cross-plotting a series of
29、one of the other tests: for example, one could takepoints at constant speed from a series of constant radius tests run on different radii.In practice, results obtained from significantly different combinations of speed-steer-radius may differsomewhat due to differences in road-load throttle, aerodyn
30、amics, tire slip, and inclination angles at differentsteering angles, etc. Some gradients obtained by different methods from a given speed-steer-radius trimcondition may differ because in some methods lateral acceleration is controlled by changing speed, and inother methods by changing steer angle.
31、Practical considerations such as tire heating during long test runs andfailure to maintain true steady-state also tend to affect test results.4.5 Steering SystemsUndersteer/oversteer gradients are stated in terms of the difference in corneringcompliances between the front and rear roadwheel “axles“;
32、 however, cornering compliances includedeflections of the steering system under side loads and aligning torques. In order to include steering systemcompliances, understeer/oversteer are determined from measurements at the steering wheel. Steering wheelangles are referred to the roadwheels by the ove
33、rall steering ratio.“Overall steering ratio“ is a variable which describes the geometric relationship between steering wheel angleand average roadwheel angle, measured under conditions of zero aligning torque and sideforce (see 7.1). Itdoes not imply a steering system with a fixed ratio: In many veh
34、icles the steering system is significantlynonlinear, due to steering arm geometry, universal joint relationships, or a variable ratio steering gear. If thesteering system is significantly nonlinear, each measured steering wheel angle must be used together with aplot of average roadwheel angle versus
35、 handwheel angle to obtain the corresponding roadwheel steer angle.Steer angle gradients are obtained from a plot of roadwheel steer angle versus lateral acceleration.4.6 Vehicles with Four-Wheel SteerCurrent four-wheel steering systems can be divided into three generaltypes: rear steer having a pro
36、grammed relationship to steering wheel angle; rear steer programmed accordingto lateral acceleration; and rear/front steer ratio programmed according to speed or other, more complex,relationships. The first type creates a combined net-effect front-rear steering ratio (Figure A1 and Figure A2)which i
37、s in general nonlinear, and which may be treated as discussed in 4.5. The second type can be treatedas only an additional source of (usually negative) rear wheel compliance steer. However, the third type mustbe considered as a separate control input. For steady-state testing of this third type of ve
38、hicle, it may benecessary to disable the rear steering to measure “basic“ response parameters, then by additional testing withrear steer enabled, determine the rear-steer control algorithm and measure its effect on steady-state responseparameters.SAE J266 Issued JAN96-4-5. Instrumentation5.1 Descrip
39、tionThe variables selected for test purposes shall be monitored using appropriate transducers, andthe data shall be recorded on a multichannel recorder having a timebase. The frequency response of theentire measurement system, including transducers, data filters, and recorder, shall have amplitude e
40、rrors(combined attenuation and ripple) less than 0.5% in the relevant frequency range of 0 to 5 Hz. If the recordingsystem involves sampling rather than continuous recording of all data channels, pre-sampling, anti-aliasingfilters are required. For 0.5% data accuracy, the anti-aliasing filters must
41、ensure that any noise components atfrequencies greater than 1/2 the sampling frequency have amplitudes less than 0.5% of the signal amplitude.The order and passband of the filters, and the sampling rate, shall be selected together to provide the requiredperformance.All pre-recording analog filters s
42、hall have sufficiently similar phase characteristics to ensure that time delaydifferences lie within the required accuracy for time measurements. Additional filtering for data evaluation andanalysis shall utilize phaseless (zero phase shift) methodologies.Corresponding samples of all data channels w
43、hich are to be compared in analysis shall be takensimultaneously, or separated in time by a delay sufficiently short to maintain the required data accuracy. (Notethat the maximum rate of amplitude change of a 5 Hz signal is 3% per millisecond.)The typical operating ranges and recommended maximum err
44、ors of the transducer/recording system areshown in Table 1.5.2 Transducers and Their InstallationTransducers of various types, some commercially available and somespecially fabricated, are used in measuring the several variables. If a transducer does not directly measure therequired variable, approp
45、riate corrections shall be made to its signal to obtain the required variable with asufficient level of accuracy.Because of the variety of instrumentation possibilities, the type of each instrument used shall be recorded; andwhere applicable, its location on the vehicle shall be entered on the test
46、data sheets.Typical errors for various direct measurement transducers are given in following paragraphs. Net percentageerror for a variable computed from the output signals of several transducers is found by taking the differential ofthe computed variable and dividing it by the computed variable.TAB
47、LE 1VARIABLESVariableTypicalOperatingRangeRecommended Maximum Errorof the CombinedTransducer/recorder SystemSteering wheel angle 180 deg 1.0 degLateral acceleration 10 m/s2 0.10 m/s2 1.0 g 0.01 gYaw velocity 50 deg/s 0.5 deg/sForward velocity 0 to 50 m/s 0.5 m/sLateral velocity 10 m/s 0.1 m/sSidesli
48、p angle 15 deg 0.5 degVehicle roll angle 15 deg 0.15 degFront wheel angle 10 deg 0.2 degRear wheel angle 10 deg 0.2 degSteering wheel torque 30 Nm 0.3 NmSAE J266 Issued JAN96-5-5.2.1 STEERING WHEEL ANGLE5.2.1.1 Steering wheel angle is measured relative to the sprung mass. Typical transducers are mul
49、titurnpotentiometers or digital shaft encoders, geared to the back of the steering wheel or attached to a “secondsteering wheel.“5.2.2 FORWARD VELOCITY5.2.2.1 A forward velocity transducer should be installed as close as possible to the mid-track position on thevehicle. If not located at mid-track, its location must be recorded and its signal corrected as necessary indata processing. Typical transducers are fifth wheels with accuracies to 0.2 km/h, and “contactless“velocity transducers based upon optical principle
