Method for locating the position of the wheels of a vehicle

Abstract

Method for locating the position of the wheels of a vehicle, each equipped with an electronic module for measuring operational parameters of each wheel, includes: controlling the transmission, by the module equipping that wheel, of n signals transmitted at times t.sub.1 to t.sub.n for given angular positions .sub.1 to .sub.n of the module, to a connected central processing unit, and to speed sensors each positioned close to a wheel, capable of delivering, values convertible into angular values, data representing the orientation of the wheel. The central processing unit is programmed to calculate, for each series of angular values .sub.1 to .sub.n provided by a wheel measuring sensor at the times t.sub.1 to t.sub.n, a characteristic value V.sub.n1-V.sub.nr representing the dispersion of the values .sub.1, (.sub.2.sub.2) . . . (.sub.n.sub.n), and to compare the characteristic values to allocate, to the electronic module, the position of the wheel located close to the wheel speed sensor.

Claims

1. A method for locating the position of the wheels (1-4) of a vehicle (V), the vehicle comprising: r wheels (1-4), each equipped with an electronic module (5-8), integrating means (9) for measuring the angular position of said electronic module, and a transmitter (10) for transmitting signals comprising data representing operational parameters of each of said wheels and an identification code of said electronic module, positioned on the vehicle (V) close to each of the wheels (1-4), a wheel speed sensor (13-16) providing, in the form of values convertible into angular values, data representing orientation of the respective one of the wheels (1-4), and mounted on the vehicle (V), a central processing unit (11), provided with a receiver (12) for receiving signals coming from the electronic modules (5-8) and connected to the different wheel speed sensors (13-16), said method for locating the position of a wheel (1-4) comprising: the electronic module (5-8) equipping the wheel delivering, at a time t1, a signal called the first signal RF1, transmitted for a given angular position of said electronic module, and then at successive times t.sub.2, t.sub.3 . . . t.sub.n, (n1) signals RF2 . . . RFn transmitted for angular positions of said electronic module shifted by determined angular values, .sub.2 to .sub.n respectively, with respect to the angular position of transmission of the first signal, where 0i360 (i=2 to n), each of the n signals RF1 . . . RFn comprising the identification code of the electronic module (5-8) and data representing the angular position of transmission, and the central processing unit (11): gathering the values convertible into angular values .sub.1 to .sub.n measured by each of the r wheel speed sensors (13-16), at each of the successive times t.sub.1 to t.sub.n, calculating, for each series of angular values .sub.1 to .sub.n corresponding to the values measured by each wheel measuring sensor (13-16), a characteristic value V.sub.n1, V.sub.n2 . . . V.sub.nr representing the dispersion of the series of values .sub.1, (.sub.2.sub.2) . . . (.sub.n.sub.n), selecting, by comparison of the r characteristic values V.sub.n1, V.sub.n2 . . . V.sub.nr, the most closely grouped series of angular values .sub.1, (.sub.2.sub.2) . . . (.sub.n.sub.n), and allocating the identification code of the electronic module (5-8) to the position of the wheel (1-4) located close to the wheel speed sensor (13-16) which is the source of the most closely grouped series of angular values .sub.1, (.sub.2.sub.2) . . . (.sub.n.sub.n).

2. The locating method as claimed in claim 1, further comprising measuring the speed of movement V.sub.v of the vehicle (V) and determining a threshold speed V.sub.s beyond which an inhibit procedure is used, the inhibit procedure comprising, when the speed of movement V.sub.v of the vehicle (V) becomes less than the threshold speed V.sub.s, storing the characteristic values V.sub.n1, V.sub.n2 . . . V.sub.nr of the r dispersions of values .sub.1, (.sub.2.sub.2) . . . (.sub.n.sub.n), and suspending the locating procedure, at the end of which, when the speed of movement V.sub.v again becomes greater than the threshold value V.sub.s, restarting the locating procedure after receiving a first signal (RFd) coming from the electronic module (5-8) equipping the wheel (1-4) in the process of being located, on the basis of dispersions, on the one hand characterized by the stored characteristic values V.sub.n1, V.sub.n2 . . . V.sub.nr and on the other hand centered on values corresponding to the values .sub.d.sub.d calculated from the values measured by each of the r wheel speed sensors (13-16) at the time td of transmission of the first signal (RFd) by the electronic module equipping the wheel.

3. The locating method as claimed in claim 2, wherein when the wheel speed sensors (13-16) comprise sensors of an active safety system, a further inhibit procedure is used when said active safety system is deactivated, the further inhibit procedure comprising, when the active safety system is deactivated, storing the characteristic values V.sub.n1, V.sub.n2 . . . V.sub.nr of the r dispersions of values .sub.1, (.sub.2.sub.2) . . . (.sub.n.sub.n), and suspending the locating procedure, at the end of which, when the active safety system is activated, restarting the locating procedure after receiving a first signal (RFd) coming from the electronic module (5-8) equipping the wheel (1-4) in the process of being located, on the basis of dispersions, on the one hand characterized by the stored characteristic values V.sub.n1, V.sub.n2 . . . V.sub.nr and on the other hand centered on values corresponding to the values .sub.d.sub.d calculated from the values measured by each of the r wheel speed sensors (13-16) at the time td of transmission of the first signal (RFd) by the electronic module equipping the wheel.

4. The locating method as claimed in claim 1, wherein the comparison of the r characteristic values V.sub.n1, V.sub.n2 . . . V.sub.nr and the allocation of the identification code of the electronic module (5-8) comprise, starting from the reception of at least a predetermined number n of signals: selecting the two characteristic values V.sub.n1, V.sub.n2 of lowest value, where V.sub.n2>V.sub.n1, comparing the ratio V.sub.n2/V.sub.n1 with a predetermined threshold, and allocating the identification code to the wheel (1-4) located close to the wheel speed sensor (13-16) which is the source of the series of angular values exhibiting the characteristic V.sub.n1, when the ratio V.sub.n2/V.sub.n1 is greater than the threshold, and continuing the procedure for locating the position of the wheel (1-4) when the ratio V.sub.n2/V.sub.n1 is less than the threshold.

5. The locating method as claimed in claim 4, further comprising determining a threshold whose value decreases as a function of the number n of signals transmitted by the electronic module (5-8).

6. The locating method as claimed in claim 5, further comprising determining a threshold whose value is inversely proportional to the number of signals transmitted by the electronic module (5-8).

7. The locating method as claimed in claim 6, further comprising determining a threshold varying between a maximum value equal to 8 for a number of signals transmitted by the electronic module (5-8) equal to ten, and a minimum value equal to 2 for a number of signals transmitted by the electronic module (5-8) equal to or greater than twenty.

8. The locating method as claimed in claim 1, wherein, when a signal of order n is received from an electronic module (5-8), the angular value (.sub.n.sub.n) taken into account for the purpose of determining the new characteristic value of each dispersion is selected such that the angular distance d between the value Xn=(.sub.n.sub.n) and the mean X(n1) of the (n1) values .sub.1, (.sub.2.sub.2) . . . (.sub.n1.sub.n1) is equal to min(d1, d2), where d1 and d2 represent the two complementary angular sectors delimited by the values Xn=(.sub.n.sub.n) and X(n1) established on a circular circumference.

9. The locating method as claimed in claim 8, wherein the characteristic value V.sub.n of the dispersion of n angular values is such that: V.sub.n=V.sub.n1.Math.(n1)/n+d.sup.2.Math.(n1)/n.sup.2 where d=min (d1, d2).

10. The locating method as claimed in claim 2, wherein the comparison of the r characteristic values V.sub.n1, V.sub.n2 . . . V.sub.nr and the allocation of the identification code of the electronic module (5-8) comprise, starting from the reception of at least a predetermined number n of signals: selecting the two characteristic values V.sub.n1, V.sub.n2 of lowest value, where V.sub.n2 >V.sub.n1, comparing the ratio V.sub.n2/V.sub.n1 with a predetermined threshold, and allocating the identification code to the wheel (1-4) located close to the wheel speed sensor (13-16) which is the source of the series of angular values exhibiting the characteristic V.sub.n1, when the ratio V.sub.n2/V.sub.n1 is greater than the threshold, and continuing the procedure for locating the position of the wheel (1-4) when the ratio V.sub.n2/V.sub.n1 is less than the threshold.

11. The locating method as claimed in claim 3, wherein the comparison of the r characteristic values V.sub.n1, V.sub.n2 . . . V.sub.nr and the allocation of the identification code of the electronic module (5-8) comprise, starting from the reception of at least a predetermined number n of signals: selecting the two characteristic values V.sub.n1, V.sub.n2 of lowest value, where V.sub.n2 >V.sub.n1, comparing the ratio V.sub.n2/V.sub.n1 with a predetermined threshold, and allocating the identification code to the wheel (1-4) located close to the wheel speed sensor (13-16) which is the source of the series of angular values exhibiting the characteristic V.sub.n1, when the ratio V.sub.n2/V.sub.n1 is greater than the threshold, and continuing the procedure for locating the position of the wheel (1-4) when the ratio V.sub.n2/V.sub.n1 is less than the threshold.

12. The locating method as claimed in claim 2, wherein, when a signal of order n is received from an electronic module (5-8), the angular value (.sub.n.sub.n) taken into account for the purpose of determining the new characteristic value of each dispersion is selected such that the angular distance d between the value Xn=(.sub.n.sub.n) and the mean X(n1) of the (n1) values .sub.1, (.sub.2.sub.2) . . . (.sub.n1.sub.n1) is equal to min(d1, d2), where d1 and d2 represent the two complementary angular sectors delimited by the values Xn=(.sub.n.sub.n) and X(n1) established on a circular circumference.

13. The locating method as claimed in claim 3, wherein, when a signal of order n is received from an electronic module (5-8), the angular value (.sub.n.sub.n) taken into account for the purpose of determining the new characteristic value of each dispersion is selected such that the angular distance d between the value Xn=(.sub.n.sub.n) and the mean X(n1) of the (n1) values .sub.1, (.sub.2.sub.2) . . . (.sub.n1.sub.n1) is equal to min(d1, d2), where d1 and d2 represent the two complementary angular sectors delimited by the values Xn=(.sub.n.sub.n) and X(n1) established on a circular circumference.

14. The locating method of claim 1, wherein each of the wheels has only one said wheel speed sensor, and wherein the step of gathering the values convertible into angular values .sub.1to .sub.n measured by each of the r wheel speed sensors (13-16), uses only values from the one said wheel speed sensor for each of the wheels.

Description

(1) Other features, purposes and advantages of the invention will emerge from the following detailed description given with reference to the appended drawings which show a preferred implementation of it by way of non-limiting example. In these drawings:

(2) FIG. 1 is a diagrammatic plan view of a vehicle provided with a monitoring system and with an active safety system allowing the implementation of the method according to the invention for locating the position of the wheels of said vehicle,

(3) FIG. 2 consists of explanatory graphs of the principle of the inhibit procedures used by the locating method according to the invention,

(4) FIGS. 3a to 3d consist of four diagrams, each one representing, during the location of a wheel, the dispersion of the values obtained from the measurements carried out by one of the wheel speed sensors,

(5) FIG. 4 is an explanatory diagram of the principle of determination of the angular distance d during the reception of a new signal of order n coming from an electronic module,

(6) and FIG. 5 is a curve representing the variation of the value of the threshold determining the stopping of the locating procedure, as a function of the number of signals coming from an electronic module.

(7) The method according to the invention is designed to be used for the purpose of locating the position of the wheels of a vehicle V such as shown in FIG. 1, provided with four wheels 1-4 and equipped with a system for monitoring parameters, such as the pressure or temperature of the tires, and with an active safety system such as an ABS Anti-lock Braking System or an, ESP dynamic stability control system.

(8) In the usual way, the monitoring system conventionally comprises, firstly, associated with each wheel 1-4, an electronic module 5-8, for example firmly attached to the rim of said wheel such that it can be positioned inside the casing of the tire.

(9) Each of the electronic modules 5-8 includes sensors dedicated for measuring parameters of the tires, connected to a microprocessor central processing unit connected to a transmitter 10.

(10) Each of these electronic modules 5-8 also includes, in a conventional manner, means 9 for measuring the angular position of said electronic module. Such measuring means can advantageously consist of an accelerometer capable of providing modulated signals representing values of the gravity and therefore of the angular position of the electronic module, whose frequency, equal to the frequency of rotation of the wheels, furthermore makes it possible to calculate the speed of rotation of said wheels.

(11) The monitoring system also comprises a central processing unit 11 situated in the vehicle V, comprising a microprocessor and integrating a receiver 12 capable of receiving the signal transmitted by the transmitters 10 of each of the electronic modules 5-8.

(12) The vehicle V is also equipped with an active safety system such as an ABS Anti-lock Braking System, or an ESP dynamic stability control system, comprising four wheel speed sensors 13-16 positioned on the vehicle V, each one close to a wheel 1-4, and designed to provide, in the form of values convertible into angular values, data representing the orientation of said wheel. The location of the vehicle of each of these speed sensors is known.

(13) Moreover, this active safety system comprises an ABS or ESP computer 17 connected to the different wheel speed sensors 13-16, so as to receive the items of wheel speed information measured by said sensors, and programmed to anticipate adjustments intended to prevent the locking of the wheels 1-4.

(14) In the usual way, the wheel speed sensors 13-16 consist of inductive, magnetoresistive or Hall Effect sensors, designed to measure the speed of rotation of each wheel 1-4 on a toothed or magnetic wheel.

(15) For the purpose of locating each wheel 1-4 of the vehicle V, the method according to the invention consists in using the data provided by the accelerometers 9 and the sensors 13-16, according to the method described below.

(16) Firstly, the electronic module 5-8 equipping the wheel 1-4 to be located provides a plurality of signals including a first signal RF1 transmitted at a time t.sub.1 for a given angular position of said electronic module, and then (n1) signals RF2 . . . RFn transmitted at successive times t.sub.2, t.sub.3 . . . t.sub.n for angular positions of said electronic module shifted by determined angular values, .sub.2 to .sub.n respectively, with respect to the angular position of transmission of the first signal, where 0.sub.i360 (i=2 to n). Each of these n signals RF1 . . . RFn notably comprises, in the usual way, the identification code of the electronic module 5-8 and data representing the angular position of transmission.

(17) The transmission of these signals is carried out over several seconds, generally 15 to 20 seconds, on the one hand for compliance with radio-frequency standards and, on the other hand, to allow a sufficient desynchronizing of the wheels 1-4,

(18) At the same time, the sensors 13-16 deliver to the computer 17 data representing the orientation of the associated wheels 1-4, in the form of values convertible into angular values (number of the tooth of the toothed wheel, etc.).

(19) As this is an active safety system, the time of transmission of these signals is distinctly shorter than that of the electronic modules 5-8, for example of the order of 10 ms to 20 ms.

(20) As shown in FIGS. 3a-3d, the central processing unit 11 of the monitoring system is itself programmed to: gather the values transmitted by the computer 17 and convert the values measured at the successive times t.sub.1 to t.sub.n into angular values .sub.1 to .sub.n, calculate, for each series of angular values .sub.1 to .sub.n corresponding to the values measured by each wheel sensor 13-16, a characteristic value, in this example the variance V.sub.n1, V.sub.n2, V.sub.n3, V.sub.n4, representing the dispersion of the series of values .sub.1, (.sub.2.sub.2) . . . (.sub.n.sub.n), select the two characteristic values V.sub.n1, V.sub.n2 of lowest value, compare the ratio V.sub.n2/V.sub.n1 with a predetermined decision threshold, and: allocate the identification code to the wheel 1-4 located close to the wheel speed sensor 13-16 which is the source of the series of angular values exhibiting the variance V.sub.n1, when the ratio V.sub.n2/V.sub.n1 is greater than the decision threshold, continue the location procedure when the ratio V.sub.n2/V.sub.n1 is less than the decision threshold.

(21) Moreover, the decision threshold has a value that is inversely proportional to the number of signals transmitted by the electronic module 5-8. As shown in FIG. 5, this decision threshold varies, more precisely, between a maximum value equal to 8 for a number of signals transmitted by the electronic module 5-8 equal to ten and a minimum value equal to 2 for a number of transmitted signals equal to or greater than twenty.

(22) Moreover, the location method is advantageously terminated when the number of signals transmitted reaches a ceiling value, equal to forty in this example, representing an obvious problem preventing the success of the location procedure.

(23) Moreover, during this procedure and during the reception of a signal of order n coming from the electronic module 5-8, the angular value (.sub.n.sub.n) taken into account for determining the new variance of each dispersion, is selected, as shown in FIG. 4, such that the angular distance d between the value (.sub.n-.sub.n) and the mean X(n1) of the (n1) values .sub.1, (.sub.2.sub.2) . . . (.sub.n1.sub.n1) is equal to min(d1, d2), where d1 and d2 represent the two complementary angular sectors delimited by the values (.sub.n.sub.n) and X(n1) established on a circular circumference.

(24) On the basis of this principle, the new characteristic variance V.sub.n, of the dispersion of the n angular values, is calculated from the following formula:
V.sub.n=V.sub.n1.Math.(n1)/n+d.sup.2.Math.(n1)/n.sup.2
where d=min(d1, d2).

(25) Moreover, during the location procedure, the method according to the invention also consists in measuring the speed V.sub.v of movement of the vehicle and in monitoring the activity of the active safety system, in such a way as to implement an inhibit procedure when the speed V.sub.v of movement of the vehicle V becomes less than a threshold speed V.sub.s, where for example V.sub.s=2 km/h, and/or when the active safety system is deactivated.

(26) As shown in Tel in FIG. 2, this inhibit procedure consists in storing the characteristic values V.sub.n1, V.sub.n2, V.sub.n3, V.sub.n4 of the four dispersions of values .sub.1, (.sub.2.sub.2) . . . (.sub.n.sub.n), and in suspending the location procedure as long as the speed V.sub.v of movement of the vehicle V remains below the threshold speed V.sub.s and/or for as long as the active safety system is deactivated.

(27) At the end of this inhibit procedure, for example as shown in FIG. 2, when the speed of movement V.sub.v again becomes higher than the threshold value V.sub.s, the central processing unit 11 is programmed to command the restarting of the locating procedure on reception of a first signal RFd coming from the electronic module 5-8 equipping the wheel 1-4 in the process of being located, on the basis of dispersions, on the one hand characterized by the stored characteristic values V.sub.n1, V.sub.n2, V.sub.n3, V.sub.n4 and on the other hand centered on values corresponding to the values .sub.d.sub.d calculated from the values measured by each of the wheel speed sensors 13-16 at the time td of transmission of the first signal RFd.

(28) When restarting, the variances taken into account therefore consist of the variances V.sub.n1, V.sub.n2, V.sub.n3, V.sub.n4 stored at the time of interrupting the procedure, recentered on the angular values .sub.d.sub.d calculated at the time td of transmission of the first signal RFd by the electronic module equipping the wheel in the process of being located.

(29) Thus, on the basis of this principle, the variances calculated subsequently depend solely on the variances V.sub.n1, V.sub.n2, V.sub.n3, V.sub.n4 and on the angular values .sub.d+1.sub.d+1, .sub.d+2.sub.d+2 . . . , that is to say values not affected by events occurring during the inhibit procedure.

(30) The location method according to the invention described above has the advantage of constituting a high-performance method in terms of reactivity and of reliability, furthermore not susceptible to being affected by possible changes in the quality of the signals delivered by the speed sensors of the active safety systems used for the purpose of implementing said method.