• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    D6260 Abstract of the Disclosure A method of indirect tire pressure monitoring for indicating When apneumatic tire on a Wheel at one end of a motor vehicle axle isunderpressurized relative to a pneumatic tire on a Wheel at an opposite endof the axle While the vehicle is being driven on a road surface. ABS Wheelsensors are used as inputs to a devoted processor for indirect tire pressure monitoring. 21
    公开号:SE1150181A1
    申请号:SE1150181
    申请日:2011-02-28
    公开日:2011-09-02
    发明作者:Zhengming Wang；Gregory A Jean-Baptiste；Huihui Duan
    申请人:Int Truck Intellectual Prop Co；
    IPC主号:
    专利说明:

    [2] [0002] The increased presence of ABS systems on motor has ledengineers to seek software methods for monitoring pneumatictire pressure that use messages from the ABS controller becausesuch methods can be highly cost effective due to the fact thateach Wheel is already equipped With a precision Wheel speedsensor. The use of ABS Wheel speed messages in methods formonitoring tire pressure are disclosed in Various patents andother documents.
    [3] [0003] In July, 2001 , the United States Department ofTransportation published a document “Tire PressureMonitoring System, FMVSS No. l38”, summarizing ITPM(indirect tire pressure monitoring) project progress. Thatdocument represents that ITPM”s can report tire underinflationWhen the tire pressure difference is greater than 20-3 0% of theirplacard pressure. This is due to the fact that the effective radiusD6260of a pneumatic tire decreases very slightly When a tire isunderinflated by about 15 psi (pounds per square inch).
    [4] [0004] The preferred embodiment of the invention utilizes adevoted processor to process data that is present in messages ona data bus conforming to SAE Standard Jl939 in a motorvehicle such as a truck and to send an alert to the driver whenthe result of processing data for two tires on a common axlediscloses that pressure in one has changed from the amount ofchange in the other by a certain amount while the vehicle isbeing driven. The messages include messages from ABSsensors. The calculations are made with a high degree ofstatistical confidence, such as 90% confidence. By the sametoken, a false alert is avoided with the same confidence.
    [5] [0005] The processing is performed in the devoted processor byexecuting an algorithm that has been developed to bereasonably sensitive and reliable, with relatively highprobability of giving a true alert indicative of a differencebetween pressure change in one tire relative to that in the otherand/or uneven tire loading on opposite sides of the vehicle, andwith relatively low probability of giving a false alert.
    [6] [0006] Although the invention is suitable for use on various motorvehicles equipped with 4-wheel ABS systems, it has beendeveloped to provide ITPM for large trucks whose GVWexceeds 4536 kg. with either single- wheel or dual-wheel driveD6260axles and that may have relatively larger tires and higherpressures than typical of smaller vehicles.[0007] One general aspect of the invention relates to a method ofindirect tire pressure monitoring for indicating When apneumatic tire on a Wheel at one end of a motor vehicle axle isunderpressurized relative to a pneumatic tire on a Wheel at anopposite end of the axle While the vehicle is being driven on aroad surface.[0008] The method comprises repeatedly calculating differencebetween a current measurement of effective radius of each tirerelative to a reference value for effective radius of the same tireand processing the calculated differences for each tire andcomparing the calculated differences to each other.[0009] When the comparison of the calculated differences disclosesthat one of the calculated differences differs from that for theother by more than a defined amount, that disclosure is used todetermine if an alert for indicating that one tire is toounderpressurized relative to the other should be issued.[0010] Another general aspect relates to an indirect tire pressuremonitoring system for indicating When a pneumatic tire on aWheel at one end of a motor vehicle axle is underpressurizedrelative to a pneumatic tire on a Wheel at an opposite end of theaxle While the vehicle is being driven on a road surface.[0011] The system comprises: a respective sensor at each Wheel thatsupplies the same data to an ABS system of the vehicle and to adevoted processor for indirect tire pressure monitoring.
    [12] [0012] The devoted processor is arranged to repeatedly execute analgorithm for calculating difference between a currentmeasurement of effective radius of each tire relative to areference value for effective radius of the same tire, to processthe calculated differences for each tire and compare thecalculated differences to each other.
    [13] [0013] When the comparison of the calculated differences disclosesthat one of the calculated differences differs from that for theother by more than a defined amount, that disclosure is used todetermine if an alert for indicating that one tire is toounderpressurized relative to the other should be issued.
    [15] [0015] The effective radius of a pneumatic tire can be Written asrj =rj(pj,vj,Tj,ljyxl.j,ykj), j=l,2,3,4, i,k=l,2,3,4.... Wherej =1,2,3,4 indicate front left, front right, rear left, rear rightWheels, p j. is the pressure, Tj is the ambient temperature, vj isWheel speed, lj is load, xljs are other factors Which are virtuallythe same acting When acting on Wheels on same axle While ykj sare factors Which act differently on each Wheel. Due to thecomplicated relationships and unpredictable factors that mayarise during driving, this generalized function cannot beD6260developed With sufficient specif1city to enable individual tirepressure to be directly monitored.
    [16] [0016] HoWever, the following generalized functional relationshipcan be further developed in a Way that enables indirectmonitoring of tire pressure in each of a pair of tires: rj = rjo + drjWhere rjo is the effective radius of a pneumatic tire under aspecified condition, such as the standard condition defined bythe tire manufacturer. Examples of other specified conditionsare the tire being under load on a vehicle, the tire being at aspecified ambient temperature, such as room temperature forexample, zero speed, etc.
    [17] [0017] drj is the first order derivative Which may be considered asmall quantity compared With rjo under normal and near-normal driving conditions. Higher order derivatives are quitesmall and can be ignored if desired for simplicity in developingan algorithm that can be executed by a processor.
    [18] [0018] Because of manufacturing tolerances and vehicle-to-vehiclevariations, rjo for each Wheel is likely to be slightly different.
    [19] [0019] Tests by one source have disclosed that a 10 PSI differencebetween the front tires Will cause the effective radius to changeabout 0.8x10*3m on average, but With a rather large standarddeviation, as Will be more fully discussed later. Because thedimensions are of the same order of magnitude, the toleranceassociated With them Will strongly affect the measurement ofD6260the effective radius due to the pressure change. To avoid this,the inventors focus attention on drj instead of rj directly.
    [20] [0020] The derivative drj can be Written asÖrj Örj Örj Örj Örj Örjdrj=â pj+â dTjJfïdvjJfïdljJfâ dxüßfïdykj;P1 Tj Vi lf xfj ykfWhere j =1,2,3,4 i,k=1,2,3,4....
    [21] [0021] Because xlj are factors Which are the same for each tire, thesubscripts of j can be omitted. The same is true for ambienttemperature, and hence the subscripts on T can also be omitted.
    [22] [0022] T h i s l e a v e s. Ö . Ö . Ö . Ö . Ö .drj = F] pj+ldT+ldvj+ldlj+ldxj+idyw WhereÖpj ÖT Övj Öl j. Öxl. Öykjj =1,2,3,4, 1,1: =1,2,3,4....[0023] Many factors are uncontrollable during driving. To reducethese effects as much as possible, consider first the differenceof derivatives of two front tires. (It is assumed that the loads onthe front tires are same, although that may be not true for reartires on uneven conditions):
    [24] [0024] dr, _ dr, = (ïdp, -Öldüp (ï-Ölyzr + (ïdv, -Öldm +Öpl Öpz ÖT ÖT Övl Övz<Öi~ Ölwl + <ï~ Öiwxf +< Örl dyki ~ Öldykz) whereÖl Öl Öxl. Öxl. Öykl Öykzi,k = l,2,3,4....
    [25] [0025] The same model tires should have similar behavior Withsmall tolerances for load, temperature, and other factors so thatthese effects Will be second order of small quantities and can beD6260
    [26] [0026]
    [27] [0027]
    [28] [0028]
    [29] [0029]neglected When the first order contributions are considered,thereby leaving:dr1_ drz I (fidpi _Öldp2)+ (ïdvi _âidvz) 'l-Öpi Öpz övr 2( än dyk, -Öldykg where k =1,2,3,4,.....Öyki ÖykzThe contribution of the second term during normal drivingshould be a small second order quantity (both and drj areVifirst order quantities) that can be neglected. Even on curvedriving, it can also be considered as a second order smallquantity. If a vehicle”s Width is a, the curvature of the road is R,a first Wheel (Wheel l) is on the inside of the curve and asecond Wheel (Wheel 2) is on the outside, v, and v, Will not beär är1 ~ 4, and canl 2íA,much different. Therefore, We can considerWrite the function as %(dv1 - dig).lAccording to the standard WdK (German Rubber EnterpriseAssociation) %so,oooi*fl (m/(knl/ro), usuany do, _v,)<10f2imile/h on curve driving, is small so that the contribution Will beon the order of l0'6 m, a small second order quantity that can beneglected. HoWever, the curve driving itself causes muchbigger “effective radius” change, to be discussed later. Thethird term can usually be f1ltered out unless some factors lastfor a long period, also to be discussed later.
    [30] [0030] Under normal condition, 1912192, dplzdpz = , = ,8191 6172making the first term of the right side of the above equationequal to 0.
    [31] [0031] If tire pressure changes such that dpl i dpz and gi i ål (ifpi p:dpI, dpg have a significant difference)ïdp2.dr] - drz = ïdpl - ap2ÖP 1
    [32] [0032] Should one tire leak (assume right front) and the other isnormal (left front):dr] - drz = - 31/2 dpz and because are not constants,p: apr Öpz
    [33] [0033]dr] - drz is not a linear function of dpz .[0034] Thus far the discussion has focused on the effective radiuschange due to physical factors. It is necessary to consideranother factor: the effective radius change due to calculation.That happens on curve driving. It is not decided by the physicalfactor as mentioned in the second term, but is decided bykinetic calculation by the formula for curve driving.
    [35] [0035] Let gb be the angle of the curve, and a be the distancebetween the two front steering Wheels. The inside Wheel travelsthe distance is Rqö and outside Wheel travels the distance is(R + a)q5. The contribution due to curve driving Will be:dig - drz i1/2 R|2
    [36] [0036]D6260
    [37] [0037] Usually the width a is about 2.5 m, and so if we setcurvature of the driving curve as 2500 m., å is about 0.l%, orthe difference is 0.5Xl0'3 m.[0038][0039]The measurement of dq - dr, is important to the algorithm.dr] is the difference between the current effective radius of atire (with the tire either cold or Warm) and the effective radiusof the tire when first put into service on the vehicle, typically asa new tire.[0040] dig is the difference between the current effective radius of atire and the effective radius that is first calculated after a limitedamount of time has elapsed upon the vehicle being first drivenafter having been parked for an amount of time sufficient toallow the tires to assume substantially ambient temperature.The limited amount of time corresponds to a warm-up time forthe tires and is typically preset (15 minutes for example), butcan be determined on the basis of certain conditions.[0041] The high resolution wheel speed data has the precision ofl/256 km/h (0.004 km/h). At a vehicle speed of 40 km/h, therelative error will be 0.0l% (for each wheel, this is only themeasurement error, we have not included the physical error forthe tire yet, but it will be discussed later), or the order of the0.05xl0'3 m. Testing has disclosed that the value of dq -dgWhen one me is io Psi iow, is about ozsxio-ß m.[0042] However, testing has disclosed that during driving, thevariation in the effective radius of a tire is significant. Forexample the standard deviation has been seen to have a rangeD6260from about 1.5x 103 m. to about 4.0x10'3 m., and that makes itdifficult to pick up useful information. The inventive algorithmhowever functions to extract the useful information with areasonably high degree of confidence in accuracy of theextracted information. Moreover, the algorithm can be used in acircumstance where the tires have slightly different initial radii.
    [49] [0049] The New Tire sub-system 18 saves the initial radii for tiresWhen first installed on the vehicle.[0050]
    [51] [0051]The Algorithm sub-system 20 judges the tire conditions.
    [60] [0060] While a presently preferred embodiment of the inVention hasbeen illustrated and described, it should be appreciated thatprinciples ofthe inVention apply to all embodiments fallingWithin the scope of the following claims.14
    权利要求:
    Claims (16)
    [1] l. A method of indirect tire pressure monitoring for indicating When apneumatic tire on a Wheel at one end of a motor vehicle axle isunderpressurized relative to a pneumatic tire on a Wheel at an opposite endof the axle While the vehicle is being driven on a road surface, the methodcomprising: repeatedly calculating difference between a current measurement ofeffective radius of each tire relative to a reference Value for effective radiusof the same tire; processing the calculated differences for each tire and comparing thecalculated differences to each other; and When the comparison of the calculated differences discloses that oneof the calculated differences differs from that for the other by more than adefined amount, using that disclosure to determine if an alert for indicating that one tire is too underpressurized relative to the other should be issued.
    [2] 2. A method as set forth in Claim l Wherein the reference value foreffective radius of each tire is determined When the respective tire Wasinitially installed on the axle by processing data representing rotationalvelocity of the respective Wheel and traveling speed of the vehicle accordingto an algorithm that repeatedly calculates the effective radius of therespective tire and that calculates the mean of a number of the repeatedcalculations of the effective radius for the respective tire, that number havingbeen statistically proven to provide each calculated mean With a certainprobability of being Within a defined margin of error for the calculated IT16 än . D6260
    [3] 3. A method as set forth in Claim 2 Wherein the number has beenstatistically proven to provide each calculated mean With at least a 90%probability of being Within a predefined acceptable margin of error for the calculated mean.
    [4] 4. A method as set forth in Claim 2 Wherein the effective radius ofeach tire determined When the respective tire Was initially installed on theaxle is used as the reference value for a limited time commencing Withdriving of the vehicle after a period of time during Which the vehicle Was notdriven and Which Was sufficient to allow the tires to assume substantially ambient temperature.
    [5] 5. A method as set forth in Claim 4 Wherein after the limited time haselapsed, the reference value that is used for effective radius of each tire issWitched to a measured value for effective radius obtained substantially contemporaneously With elapse of the limited time.
    [6] 6. A method as set forth in Claim l comprising obtaining themeasurement of effective radius of each tire by processing data from arespective sensor at each Wheel that also supplies the same data to an ABS system of the vehicle.
    [7] 7. A method as set forth in Claim l Wherein the step of processing acurrent measurement of effective radius of each tire relative to a referencevalue for effective radius of the same tire comprises calculating each current measurement by calculating the mean of a number of individual 16 D6260 measurements of the effective radius and then using the calculated mean foreach tire as the current measurement of effective radius of the respective tirein the calculation of difference between a current measurement of effectiveradius of each tire relative to the reference value for effective radius of the same tire.
    [8] 8. A method as set forth in Claim l Wherein the step of usingdisclosure that one of the calculated differences differs from that for theother by more than a defined amount to determine if an alert for indicatingthat one tire is too underpressurized relative to the other should be issuedcomprises incrementing or decrementing an alert parameter, and furtherincluding issuing an alert When the absolute value of the alert parameter equals a predetermined limit.
    [9] 9. An indirect tire pressure monitoring system for indicating When apneumatic tire on a Wheel at one end of a motor vehicle axle isunderpressurized relative to a pneumatic tire on a Wheel at an opposite endof the axle While the vehicle is being driven on a road surface, the systemcomprising: a respective sensor at each Wheel that supplies the same data to anABS system of the vehicle and to a devoted processor for indirect tirepressure monitoring; and Wherein the devoted processor is arranged to repeatedly execute analgorithm for calculating difference between a current measurement ofeffective radius of each tire relative to a reference value for effective radiusof the same tire, to process the calculated differences for each tire and compare the calculated differences to each other, and When the comparison 17 D6260 of the calculated differences discloses that one of the calculated differencesdiffers from that for the other by more than a defined amount, using thatdisclosure to determine if an alert for indicating that one tire is too underpressurized relative to the other should be issued.
    [10] 10. An indirect tire pressure monitoring system as set forth in Claim 9Wherein the algorithm operates to determine the reference Value for effectiveradius of each tire When the respective tire Was initially installed on the aXleby processing data representing rotational Velocity of the respective Wheeland traveling speed of the vehicle to repeatedly calculate the effective radiusof the respective tire and to calculate the mean of a number of the repeatedcalculations of the effective radius for the respective tire, that number havingbeen statistically proven to provide each calculated mean With a certainprobability of being Within a defined margin of error for the calculated mean.
    [11] 1 1. An indirect tire pressure monitoring system as set forth in Claim10 Wherein the number has been statistically proven to provide eachcalculated mean With at least a 90% probability of being Within a predefined margin of error for the calculated mean.
    [12] 12. An indirect tire pressure monitoring system as set forth in Claim10 Wherein algorithm operates to use the effective radius of each tiredetermined When the respective tire Was initially installed on the axle as thereference value for a limited time commencing With driving of the vehicleafter a period of time during Which the vehicle Was not driven and Which Was sufficient to allow the tires to assume substantially ambient temperature. 18 D6260
    [13] 13. An indirect tire pressure monitoring system as set forth in Claim12 Wherein after the limited time has elapsed, the algorithm operates toswitch the reference Value from the one that Was being used for effectiveradius of each tire to a measured Value for effective radius obtained substantially contemporaneously With elapse of the limited time.
    [14] 14. An indirect tire pressure monitoring system as set forth in Claim 9Wherein the algorithm operates to process a current measurement ofeffective radius of each tire relative to a reference value for effective radiusof the same tire by calculating the means of a number of currentmeasurement of effective radius for the same tire and then using thecalculated mean for each tire as the current measurement of effective radiusof each tire When calculating difference between a current measurement ofeffective radius of each tire relative to the reference value for effective radius of the same tire.
    [15] 15. An indirect tire pressure monitoring system as set forth in Claim 9Wherein the algorithm is arranged to use disclosure that one of the calculateddifferences differs from that for the other by more than a defined amount todetermine if an alert for indicating that one tire is too underpressurizedrelative to the other should be issued by incrementing or decrementing analert parameter, and then issuing an alert When the absolute value of the alert parameter equals a predetermined limit.
    [16] 16. A method of calculating a reference value for effective radius of a pneumatic tire on a Wheel just installed on an axle of a motor vehicle, and 19 D6260 then using the reference value for indirect tire pressure monitoring, themethod comprising: processing data representing rotational Velocity of the Wheel andtraveling speed of the vehicle in a processor according to an algorithm thatrepeatedly calculates the effective radius of the tire, that calculates the meanof a number of the repeated calculations of the effective radius for the tirethat has been statistically proven by prior testing to provide the calculatedmean With a certain probability of being Within a defined margin of error forthe calculated mean, that further processes the calculated mean effectiveradius With other data, and that causes an alert to be given When a result of the further processing discloses that the alert should be given.
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    法律状态:
    2012-09-18| NAV| Patent application has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    US12/714,684|US8350688B2|2010-03-01|2010-03-01|System and method for indirect indication of tire pressure loss|
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