# SAE J1013v001

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 therefrom, 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: (412) 772-8512 FAX: (412) 776-0243TO PLACE A DOCUMENT ORDER; (412) 776-4970 FAX: (412) 776-0790SAE WEB ADDRESS http://www.sae.orgCopyright 1992 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001STANDARDAn American National StandardJ1013REV.AUG92Issued 1973-08Revised 1992-08Superseding J1013 JAN80(R) MEASUREMENT OF WHOLE BODY VIBRATION OF THE SEATED OPERATOR OF OFF-HIGHWAY WORK MACHINESForeword—This Document has not changed other than to put it into the new SAE Technical Standards BoardFormat.1. Scope—This SAE Standard defines a method for the measurement of the whole body vibration to which theseated operator of off-highway self-propelled work machines is exposed while performing an actual orsimulated operation. It applies to vibration transmitted to the operator through the seat. There are noequivalent ISO Standards.1.1 Application—In the main body of this document, conditions are defined for measuring and recording whilebody vibration of the seated operator of off-highway self-propelled work machines. The specification ofinstruments, analytic methods, and description of site and operating conditions allows the measurements to bemade and reported with an acceptable precision. The procedure includes means of weighting the vibrationlevel at different frequencies as specified in ISO 2631. A standard format for reporting spectral data isrecommended.The definitions, instruments, and analytic methods also apply to simulated tests for operator vibration asperformed in laboratories.This procedure is a measuring method only and is not intended for the evaluation or selection of seatingsystems.2. References2.1 Applicable Publications—The following publications form a part of this specification to the extent specifiedherein. Unless otherwise indicated the latest issue of SAE publications shall apply.2.1.1 SAE PUBLICATIONS—Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J711 MAR91—Tire Selection Tables for Agricultural Tractors of Future DesignSAE J751 APR86—Off-Road Tire and Rim Classification - Construction MachinesSAE J1013 Revised AUG92-2-2.1.2 ANSI AND ISO PUBLICATIONS—Available from ANSI, 11 West 42nd Street, New York, NY 10036-8002.ANSI S2.2-1959 (R-1990)—Methods for Calibration of Shock and Vibration PickupsISO 2631-1:1985—Evaluation of human exposure to whole body vibration—Part 1: General requirementsISO 2041-1975—Vibration and shock vocabularyISO5008-1979(E)—Agriculture wheeled tractors and field machinery—Measurement of whole-bodyvibration of the operator2.1.3 IRIG PUBLICATION—Available from Secretariat, Range Commanders Council, Attn: STEWS-SA-R, WhiteSands Missile Range, New Mexico 88002.IRIG Document 106—Inter Range Instrumentation Group. Magnetic Tape Recorder ReproducerStandards2.2 Related Publications—The following publications are provided for information purposes only and are not arequired part of this document.2.2.1 SAE PUBLICATIONS—Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE HS J6a—Ride and Vibration Data Manual2.2.2 ANSI PUBLICATIONS—Available from ANSI, 11 West 42nd Street, New York, NY 10036-8002.ANSI S1.11-1986—Specifications for Octave Band and Fractional Octave Band Analog and Digital FiltersANSIS2.4-1976 (R-1990)—Method for Specifying the Characteristics of Auxiliary Equipment for Shockand Vibration Measurement3. Definitions3.1 Whole Body Vibration—As used in this document, this term means vibration transmitted to the body as awhole through the buttocks of a seated operator.3.2 Operator Seat—Specifically for the purposes of this document, that portion of the machine provided for thepurpose of supporting the buttocks of the seated operator, including the seat suspension system.3.3 Frequency Analysis—Process of arriving at a quantitative description of the amplitude of a vibration as afunction of frequency.3.4 Measurement Interval—The time interval over which vibration data for analysis is obtained.3.5 Average Ground Speed—Ratio of the distance traveled during the measurement interval to the length of themeasurement interval.Other terminology used in this recommendation is in accordance with ISO 2041.4. Letter Symbolsa - instantaneous accelerationaf - rms value of 1/3 octave acceleration having center frequency faw - frequency weighted acceleration signalawf - weighted rms acceleration calculated as described in 6.4.1, 6.4.2, or 6.4.3Be - resolution bandwidth of a frequency analysis, Hzf - frequencyrms - root-mean-squareSAE J1013 Revised AUG92-3-T - analysis time duration, secondsm/s2 - acceleration units, meters per second squaredHz - hertz, standard notation for frequency, cycles per secondWf - frequency dependent, dimensionless weighting factorG - acceleration of gravity, by international agreement equal to 9.80665 m/s2 at sea levelPSD - Power Spectral Density expressed as mean square acceleration per unit bandwidth (m/s2)2 Hz5. Vibration Measurement Axes—The vibration shall be measured along three mutually perpendicular axes,passing through a point on the interface between the operator and the seat. These axes are substantiallyvertical, longitudinal, and lateral (az, ax, and ay) with respect to the orientation of the seated operator and aredefined in Figure 1. The operator should sit in a typical upright position and should keep both hands in anormal position for operating the controls as suggested by Figure 1. The seat shall be adjusted permanufacturer s instructions.FIGURE 1—MEASUREMENT AXESSAE J1013 Revised AUG92-4-6. Instruments6.1 Acceleration Transducers—Vibration shall be sensed by acceleration transducers (accelerometers) in themounting device described in 6.2.1. The accelerometers, together with their associated amplifiers, shall becapable of measuring rms acceleration levels ranging from 0.1 m/s2 to 10 m/s2 with a crest factor as great asthree. During the test the accelerometer and amplifier, with proper calibration for the test, shall have anaccuracy of at least ±2.5% of the actual rms vibration levels in the frequency range from 0.3 to 40 Hz and atleast ±6% of the actual rms vibration levels in the frequency range from 40 to 80 Hz as calculated from theinstrument specifications and the actual test conditions. See 6.5 for accuracy and frequency responserequirements during calibration. The resonant frequency of the accelerometers shall be greater than 300 Hz.The accelerometers shall sustain instantaneous acceleration levels up to 100 m/s2 without damage.Accelerometers in the mounting device (see 6.2.1) and on the seat mounting base (see 6.2.2) should be ofsimilar type or model, with similar signal to noise ratios.6.2 Transducer Mounting6.2.1 VIBRATION TRANSMITTED TO THE OPERATOR—The accelerometers for sensing vibration transmitted to theoperator shall be attached near the center of a thin disc 200 mm ± 5 mm in diameter placed between theoperator and the seat cushion. The primary requirements for the disc are that it should provide a suitablemounting for the accelerometers, shall not adversely affect operator comfort, and shall not significantlydistort the buttock-cushion load distribution. Either a rigid or semirigid disc may be used; however, thesemirigid disc is recommended especially for soft or highly contoured cushions. Suggested disc designs areshown in Figures 2 and 3. Either disc shall be placed on the seat so that the accelerometers are locatedmidway between the ischial tuberosities and are aligned parallel to the measurement axes (Figure 1). Thedisc should be taped or similarly attached to the cushion to maintain its location.FIGURE 2—SUGGESTED DESIGN FOR RIGID DISC WITH ACCELEROMETER ASSEMBLY BONDED AT CENTERSAE J1013 Revised AUG92-5-FIGURE 3—SUGGESTED DESIGN FOR SEMIRIGID DISC OF APPROXIMATELY 80 TO 90 DUROMETER (A-SCALE) MOLDED RUBBER, PLASTIC, ETC.6.2.2 VIBRATION AT THE SEAT MOUNTING BASE—The vibration of the machine at the base of the seat shall besensed by accelerometers attached to a rigid portion of the machine or seat mounting base. Theaccelerometers shall be located within the vertical projection of seat cushion, not more than 100 mm fromthe vertical, longitudinal plane through the center of the seat, and shall be aligned parallel to themeasurement axes (see Figure 1).6.3 Magnetic Tape Recorder—The electrical signals generated by the transducers may be recorded on magnetictape for later analysis. The magnetic tape recorder, with proper calibration for the test, shall be capable of areplay accuracy of at least ±3% of the rms value of the total signal within the frequency range from 0 to 80 Hz,as calculated from the instrument specifications and the actual test conditions. The tape recorder should meetcurrent standards for alignment and distortion characteristics (see IRIG Document 106).6.4 Frequency Weighting—Frequency weighting may be achieved in any of three ways: by digital analysis of theacceleration into constant bandwidth levels, weighting the levels in individual bands and recombination; byanalysis of the acceleration into 1/3 octave band levels, weighting the levels in individual bands andrecombination; or by the use of frequency weighting analog or digital filters. The three methods generallyprescribe the calculation of the weighted acceleration over the range of 1 to 80 Hz; however, the weightedacceleration may be calculated over a reduced frequency range if such a range is specified by an approvedstandard that governs the conduct of the specific test. The three methods are described in 6.4.1, 6.4.2, and6.4.3 in decreasing order of accuracy (accuracy as resulting from practical considerations of analysisequipment).6.4.1 CONSTANT BANDWIDTH METHOD—Each vibration tape recording, or vibration signal where a tape recorder isnot used, shall be analyzed into constant bandwidth acceleration levels over the frequency range from 1 to80 Hz by appropriate digital methods. The length of the measurement interval, T (in seconds), andresolution bandwidth, Be (in Hz), shall satisfy the following equation:(Eq. 1)2BeT 140≥ Be 0.3Hz≤SAE J1013 Revised AUG92-6-The mean square value of the digitized time data (time domain) should be compared to the mean squarevalue of the spectral estimate (frequency domain). If these values differ, then the analysis procedure shouldbe reviewed and corrected as necessary for possible errors such as improper scaling, wrong correctionfactor for the data time window (sampling window), or program errors.The constant bandwidth rms levels shall each be multiplied by weighting factors calculated for each centerfrequency from Figure 4 for az (vertical) vibration, or Figure 5 for ax or ay (horizontal) vibration. A weightedacceleration value, awf, shall be calculated as the square root of the sum of the squares of the weightedconstant bandwidth levels over the range 1 to 80 Hz.6.4.2 ONE-THIRD OCTAVE BANDWIDTH METHOD—Each vibration tape recording, or vibration signal where a taperecorder is not used, shall be analyzed into 1/3 octave component accelerations for the center frequencies ofTable 1. The rms value of each component, af, shall be averaged over the duration specified for themeasurement. The 1/3 octave values shall each be multiplied by the weighting factors, Wf, listed in Table 1,and a weighted acceleration, awf, value calculated for each recording as in the following equation:(Eq. 2)To satisfy the following equation:(Eq. 3)The minimum measurement interval, T, is 300 s to insure sufficient statistical precision.Because of the bandwidth of 1/3 octave data, this method includes a slightly wider frequency range than theother methods. In practice, this will usually have a negligible effect on the results.awfwf2af2f 1=80∑12⁄=2BeT 140≥SAE J1013 Revised AUG92-7-FIGURE 4—FILTER RESPONSE IN VERTICAL MODE, aZTABLE 1—VIBRATION WEIGHTING FACTORS1/3 Octave CenterFrequency, fWeightingFactor, WfWeightingFactor, Wf1/3 Octave CenterFrequency, fWeightingFactor, WfWeightingFactor, WfVerticalVibrationHorizontalVibrationVerticalVibrationHorizontalVibration1.0 0.50 1.00 10.0 0.80 0.201.25 0.56 1.00 12.5 0.63 0.161.6 0.63 1.00 16.0 0.50 0.1252.0 0.71 1.00 20.0 0.40 0.1002.5 0.80 0.80 25.0 0.315 0.0803.15 0.89 0.63 31.5 0.25 0.0634.0 1.00 0.50 40.0 0.20 0.0505.0 1.00 0.40 50.0 0.16 0.0406.3 1.00 0.315 63.0 0.125 0.03158.0 1.00 0.25 80.0 0.10 0.025SAE J1013 Revised AUG92-8-FIGURE 5—FILTER RESPONSE FOR aX AND aY6.4.3 FREQUENCY WEIGHTING FILTERS—An analysis system based on this method shall consist of a frequencyweighting filter incorporated between the transducer and a time integration stage. Both the filter and theintegrator may be implemented by analog or digital means. The weighting network shall have an insertionloss conforming to the curve in Figure 4 for az (vertical) vibration, or Figure 5 for ax or ay (horizontal)vibration. The loss shall not deviate from the curve by more than ± 1 dB for frequencies between 1.1 and10Hz, and ± 2 dB at any other frequency. The integration stage shall be capable of indicating the integral ofthe square of weighted acceleration, aw, for the measurement interval of the test. That is, for an analogintegrator,(Eq. 4)and for a digital integrator,(Eq. 5)Where conditions permit, a minimum measurement interval of 300 s shall be used.NOTE—The measurement interval (methods of 6.4.1, 6.4.2, and 6.4.3) when testing on a specific test trackshall be the time required to traverse the track.awf()2 1T---a 2w td⋅t 0=T∫=awf()1N--- aw n()2n 1=N∑=SAE J1013 Revised AUG92-9-6.5 Calibration6.5.1 GENERAL—Operating manuals or other literature furnished by the instrument manufacturer should bereviewed for both recommended operation of the instrument and precautions to be observed. The entiremeasurement and analysis system should be regularly calibrated by technically trained instrumentationpersonnel following manufacturer s recommendations for the adjustment and application of individualcomponents.Acceleration transducers should be calibrated in accordance with a suitable recognized calibration methodsuch as outlined in ANSI S2.2 (R-1990). In particular, the calibration procedures should ensure that theaccelerometer sensitivity (V/(m/s2)) varies less than ±2.5% of a mean value over the frequency range of 0 to40 Hz and less than ±6% of a mean value over the frequency range of 0 to 80 Hz.The effects of amb