Method of associating tire pressure control apparatuses to wheel positions

Abstract

Tire pressure control devices include first sensors to deliver repeatedly a measured value M1 for the rotation speed of the wheel. A measurand, from which the rotation speed of the associated wheel can be derived, is detected in a pointwise manner by means of a second sensor over a predetermined rotation angle of the wheel as a function of time, is subjected to a low pass filtering in a subsequent first time interval t1 and from the filtered development of the measurand a second measured value M2 is determined, which is a measurement for the rotation speed or respectively for the angular speed of the associated wheel. Each tire pressure control device transmits at the end of a second time interval t2 the second measured value M2 together with an identification of the tire pressure control device to a central unit. Comparing M1 and M2 determines wheel position.

Claims

1. A method for the allocating of tire pressure control devices of a tire pressure control system of a vehicle to the different positions at which respectively a wheel of the vehicle is mounted, automatically by the tire pressure control system, the method comprising the steps of: providing the tire pressure control system, the system comprising: a number of first sensors, corresponding to the number of wheel positions, which are each fixedly allocated to one of the wheel positions and can detect a rotation speed or an angular speed of the wheel which is mounted in the wheel position; a number of tire pressure control devices, coinciding with the number of the mounted wheels, which devices are mounted on the wheels rotating together with these, are provided with an individual identification and contain a second sensor for determining a measurand, from the chronological development of which the rotation speed of the respective wheel or the angular speed of the wheel can be derived; a central unit, in which the allocation of the tire pressure control devices to respectively one wheel position, namely the identification of the tire pressure control device situated in the wheel position in connection with the associated wheel position, can be stored; wherein it is known by the central unit from this method which first sensor is allocated to which wheel position; delivering, by the first sensors, repeatedly a measured value M1 for successive time segments T, the measured value M1 being a measurement for the rotation speed or for the angular speed of the wheel to which the respective first sensor is allocated; sending, by the tire pressure control devices, their individual identification to the central unit in chronological intervals; wherein in each rotating tire pressure control device there are performed the steps of: detecting, by each rotating tire pressure control device, pointwise the development of the measurand from which the rotation speed or the angular speed of the associated wheel can be derived by means of the second sensor over a predetermined rotation angle of the wheel as a function of time; low pass filtering, by each rotating tire pressure control device, of the chronological development of the measurand in a first time interval t.sub.1 following the detection of the measurand detected during the rotation of the wheel about the predetermined rotation angle ; storing, by each rotating tire pressure control device, the result of the filtering; determining, by each rotating tire pressure control device, a second measured value M2 from the filtered development of the measurand, which is a measurement for the rotation speed or respectively for the angular speed of the associated wheel in the range of the observed predetermined rotation angle ; transmitting, by each tire pressure control device, the second measured value M2 together with its identification to the central unit at the end of a second time interval t.sub.2, the duration of which is not less than the first time interval t.sub.1; comparing, in the central unit as a result of this transmittal, the second measured values M2 transmitted by the tire pressure control devices with the measured values M1 detected in a timely manner by the first sensors of all wheels; and storing, in the central unit, the identification of the tire pressure control device respectively under that wheel position in which the measured value M1 delivered by the first sensor best coincides with the measured value M2.

2. The method according to claim 1, wherein as first sensors anti-lock braking system (ABS) sensors are used, of which in each case one ABS sensor is allocated to one of the wheel positions of the vehicle.

3. The method according to claim 1, wherein the duration of the second time interval t.sub.2 is constant.

4. The method according to claim 1, wherein the end of the first time interval t.sub.1 is placed such that it coincides with the moment at which the end of the filtered development of the measurand detected by the second sensor has left the low pass filter and is stored in the tire pressure control device.

5. The method according to claim 1, wherein the measured value M2, if applicable also the measured value M3, is additionally used in the central unit in order to determine the angular position which the wheel has at the end of the first time interval t.sub.1 and/or at the end of the second time interval t.sub.2.

6. The method according to claim 1, wherein more than one identification is stored in the central unit for each wheel position.

7. The method according to claim 1, wherein the tire pressure control devices send in shorter time intervals in the allocation method than in a normal operation of the tire pressure control system, in which only identifications which are already stored in the central unit are transmitted to the central unit from all tire pressure control devices.

8. The method according to claim 1, in which a low pass filter is used, the threshold frequency of which lies between 1 Hz and 5 Hz.

9. The method according to claim 1, wherein as measured values M1 detected in a timely manner, those measured values M1 are selected which were measured in not more than five successive time segments T, wherein the end of the second time interval t.sub.2, in which in a tire pressure control device a low pass filtering of the development of the measurand detected by the second sensor and the transmittal of the second measured value M2 as well as the identification to the central unit takes place, lies in the no more than five time segments T or at the boundary thereof.

10. The method according to claim 1, wherein the second measured values M2 are transmitted twice to the central unit, namely once at the end of the second time interval t.sub.2 and a second time after a further rotation of the wheel about less than one revolution.

11. The method according to claim 1, wherein as second sensor such a sensor is used which delivers a signal with a periodic development, wherein the period is constant as long as the vehicle moves in a straight line with a constant speed.

12. The method according to claim 11, wherein as second sensors acceleration sensors are used, at least one of which is contained in each tire pressure control device.

13. The method according to claim 1, wherein as measured values M1 detected in a timely manner, those measured values are selected which were measured in several successive time segments T, which overlap with the second time interval t.sub.2 or lie at its boundary.

14. The method according to claim 13, wherein as measured values M1 detected in a timely manner, the measured values M1 are selected which were measured in two successive time segments T.

15. The method according to claim 1, wherein it is carried out repeatedly, wherein the allocations obtained in each run of the method are collected in the central unit, wherein the collected allocations are analyzed according to the frequency of their occurrence, and wherein for each wheel position the identification is stored which is allocated to it the most frequently.

16. The method according to claim 15, wherein after a start of a journey it is then carried out in a shortened manner, i.e. with a smaller number of repetitions than with a storage for the first time of a particular allocation, if, to the given wheel positions, that identification, which was already stored during the preceding journey as the most frequent identification, is transmitted again to the central unit.

17. The method according to claim 1, wherein the first sensors measure the measurand, which is a measurement for the rotation speed or for the angular speed, and store the measurement result for a predetermined duration.

18. The method according to claim 17, wherein the measurement results of the first sensors are stored for a time span T1, which is twice to five times as long as the predetermined time segment T for the individual measurement.

19. The method according to claim 17, wherein the time segment T for the individual measurement lies between 10 ms and 100 ms.

20. The method according to claim 1, wherein the duration of the first time interval t.sub.1 is constant.

21. The method according to claim 20, wherein the first time interval t.sub.1 in which, in the tire pressure control devices, the development of the measurand detected by the second sensor is subjected to a low pass filtering, or the rotation angle about which the wheel has further rotated during the first time interval t.sub.1 and/or the second time interval t.sub.2, is either given as known to the central unit or is transmitted to it as a third measured value M3 by the tire pressure control device together with its identification and with the filtered measurand or with the second measured value M2 derived therefrom.

22. The method according to claim 21, wherein the predetermined duration of the first time interval t.sub.1 in which the detected measurand is subjected to a low pass filtering in the tire pressure control devices, and/or the duration of the second time interval t.sub.2 is selected in a speed-dependent manner, and namely such that the duration of the first time interval t.sub.1 and/or the duration of the second time interval t.sub.2 decreases with increasing speed of the vehicle.

23. The method according to claim 22, wherein the predetermined duration of the first time interval t.sub.1 and or the predetermined duration of the second time interval t.sub.2 is adapted in stages or continuously to the speed of the vehicle or to the rotation speed or respectively angular speed of the wheel concerned.

24. The method according to claim 1, wherein in the tire pressure control devices the second sensor detects its measurand several times, in each case for a second time span T2, which the wheel requires in order to rotate about at least 180.

25. The method according to claim 24, wherein in the tire pressure control devices the second sensor detects its measurand several times, in each case for a second time span T2, which the wheel requires in order to rotate about a whole-number multiple of 180.

26. The method according to claim 24, wherein the predetermined rotation angle about which the wheels are to rotate for the detecting of the measurand of the second sensor, is selected so that the measuring begins in a predetermined rotation angle position of the second sensor.

27. The method according to claim 26, wherein in the tire pressure control devices the measurand detected by the second sensor is filtered by means of a digital low pass filter and that by means of the filtered signal the second time span T2 is measured which the wheel requires for its rotation about the predetermined rotation angle .

28. The method according to claim 27, wherein as measurement for the rotation speed or the angular speed of the wheel, the second time span T2 which the wheel required for a rotation about the predetermined rotation angle , or the rotation speed or angular speed of the wheel calculated from the predetermined rotation angle and the second time span T2 required therefor in the tire pressure control device at the end of the second time interval t.sub.2 together with the identification of the tire pressure control device and if applicable together with the second time interval t.sub.2 or with the rotation angle , about which the wheel has further rotated during the second time interval t.sub.2, is transmitted to the central unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The enclosed drawings serve for further explanation of the invention:

(2) FIG. 1 shows in a flow diagram the obtaining of measured values which are a measurement for the rotation speed or respectively for the angular speed of wheels of a vehicle, on the one hand by means of ABS sensors and on the other hand by means of tire pressure control devices, and the transmitting of these signals to a central unit;

(3) FIG. 2 shows a flow diagram following the flow diagram of FIG. 1, for the evaluation of the measured values obtained according to FIG. 1 in the central unit; and

(4) FIG. 3 shows diagrammatically in an example how on a rotating wheel the position of the tire pressure control device rotates further in the time interval t.sub.2 between the detection of a measurand, from which the rotation speed or the angular speed of a wheel can be derived, and the transmittal of a measured value, obtained therefrom, by the tire pressure control device to the central unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) According to FIG. 1, the method begins in the tire pressure control device of a wheel which is mounted on a vehicle, in step 1 with a start signal which is generated in the tire pressure control device itself, e.g. in that an acceleration sensor establishes that the wheel is rotating after it was not able to establish a movement for a predetermined duration, e.g. more than half an hour. Triggered by the start signal, in a step 2 the acceleration occurring at the tire pressure control device is begun to be measured continuously and the acceleration measured values are begun to be stored pointwise respectively for the duration of a predetermined number of periods.

(6) The pointwise storage can take place so that an analog acceleration signal delivered by the acceleration sensor is scanned pointwise, in particular in constant time intervals, and the discrete acceleration values ascertained in this way for a predetermined number of periods of the acceleration signal are stored in the tire pressure control device. The chronological development of the acceleration is then present pointwise in the memory. This is advantageous for a digital further processing.

(7) In a step 3 a digital low pass filter is activated, which in a step 4 subjects the pointwise stored development of the signal of the acceleration sensor to a digital low pass filtering. The filtered acceleration signal is likewise present as a sequence of discrete acceleration values and has an approximately sinusoidal development, superimposed by the constant gravitational acceleration as offset. The length of the period of the filtered acceleration signal is inversely proportional to the rotation speed of the wheel.

(8) Already the observing of only a half period of the acceleration signal permits a statement as to the rotation speed of the wheel. A more precise statement is possible, however, when not only a half period of the acceleration signal is evaluated, but rather a greater length of the acceleration signal. It is in particular possible to evaluate respectively two periods of the acceleration signal. Therefore, in a step 5 the length of the period is measured for a segment of the filtered acceleration signal which is two periods long, and in a step 6 the rotation speed of the wheel is calculated therefrom.

(9) In a step 7 the beginning and the end of the two periods of the filtered acceleration signal are sought. The beginning and the end of a period can be best established in a sinusoidal development by means of the zero crossings of the development. This takes place in step 7 by calculation, by either the development of the filtered acceleration signal being differentiated and the extreme values of the development being sought, or by the offset originating from the gravitational acceleration being eliminated in the development of the acceleration signal and the zero points of the remaining alternating component of the acceleration signal being sought.

(10) In a step 8 the duration of the first period and the duration of the second period of the acceleration sensor are measured and compared with one another. If they are identical, in a step 11 the measured value determined from the two periods, which is a measurement for the rotation speed of the wheel and which is the second measured value M2 in the sense of the claims, is transmitted by radio to the central unit 22. The radiotelegram transmitted to the central unit 22 contains in addition the identification of the tire pressure control device and particularly the duration of the second measurement interval t.sub.2, by which the transmittal of the radiotelegram is delayed with respect to the end of the second period of the acceleration signal detected in real time by the acceleration sensor. This second time interval t.sub.2 is sufficiently long in order to enable the filtering of the acceleration signal and the measuring and testing of the period lengths.

(11) After the transmittal of the radiotelegram to the central unit, the stored data of the two evaluated periods of the acceleration signal are deleted in the tire pressure control device, in particular in that they are overwritten with the data of the two subsequent periods of the acceleration signal.

(12) If it is found on comparing the durations of the two periods of the acceleration signal that they deviate from one another, in a step 9 the extent of the deviation is determined and is compared with a predetermined tolerance value in a step 10. If the difference of the two periods is not greater than the predetermined tolerance value, the second measured value determined from the two periods is transmitted to the central unit 22 in step 11.

(13) If, however, on comparing the durations of the two periods in step 8 it is found that they deviate from one another by more than the predetermined tolerance value, these two periods of the acceleration signal are discarded and the method is continued with the step 6, in which the rotation speed of the wheel is determined from the two successive periods of the acceleration signal.

(14) The time interval t.sub.2 can be given as known to the central unit when it is not possible in the control of the tire pressure control device to change the time interval t.sub.2 autonomously. In this case, the duration of the second time interval t.sub.2 does not have to be also transmitted to the central unit in the radiotelegram.

(15) When the tire pressure control device is programmed so that it always evaluates two revolutions of the wheel in order to determine the rotation speed, which corresponds to a rotation angle =720, this can also be given as known to the central unit. The central unit can calculate from the rotation angle and the transmitted measured value of the rotation speed the duration of the second time span T2, which the wheel has used for the two revolutions, and from the time interval t.sub.2 which is also transmitted, the central unit can determine how long ago the period of time was for which the tire pressure control device has determined the rotation speed. This is of importance for the subsequent comparison of the rotation speed transmitted by the tire pressure control device with the rotation speeds or angular speeds determined by the stationary second sensors.

(16) The measurements by the ABS sensors which are fixedly allocated to the wheel positions take place chronologically independently of the steps occurring in the tire pressure control device. For a vehicle with four wheels there are four ABS sensors for the positions front right (FR), front left (FL), rear right (RR) and rear left (RL). Each ABS sensor counts in a step 12 independently of the other ABS sensors and independently of the tire pressure control devices e.g. the teeth, running past it, of a toothed ring rotating with the wheel repeatedly in successive constant time segments T, which can be given as known to the central unit 22. In a processing unit 23 the rotation speeds or angular speeds can be calculated therefrom in a step 13 for the different wheel positions. The processing unit 23 can be allocated to the ABS sensor or to the central unit 22.

(17) Alternatively, it is possible for the determining of the rotation speed or of the angular speed to not take as the basis identical time segments T, but rather for a predetermined number of teeth, in particular for the entire number of teeth of the ABS toothed ring, to determine the time span T which is required in order to count the predetermined number of teeth of the ABS toothed ring. In this case, instead of the number of teeth, the variable time segments T must be transmitted to the central unit 22, whereas the total number of teeth of the ABS toothed ring can be given as known to the central unit 22.

(18) In order to determine the correct allocations, the central unit 22 on the one hand can access the data transmitted by the tire pressure control devices, which contain the identification, the rotation speed or the angular speed of the tire pressure control device and the associated time period of their detection, namely the second measured values M2, and on the other hand can access the rotation speeds or angular speeds originating from the ABS sensors, that is the first measured values M1, connected with the time period for which they were determined.

(19) The method explained by means of FIG. 1 continues in the method sequence illustrated in FIG. 2. The first measured values M1 originating from the ABS sensors are stored for successive time spans T in the central unit 22 under the associated wheel position FR or respectively FL or respectively RR or respectively RL. This takes place in step 13 or 14. The second measured values M2, transmitted in a timely manner by the tire pressure control devices, are stored in step 14 in the central unit 22. In FIG. 2, in step 14 only the signal M2 from one of the tire pressure control devices is indicated, for the sake of clarity.

(20) In the next step 15, the central unit 22 compares the time indications linked with the measured values and establishes which of the measured values M1 originating from the four ABS sensors were detected contemporaneously or in a timely manner with the measured value M2 of the one tire pressure control device. These measured values M1 are selected in step 15 and are compared with the measured value M2 in step 16.

(21) In step 17 the identification belonging to the measured value M2 is stored under that of the four wheel positions, the measured value M1 of which shows the least deviation from the measured value M2. The storage takes place in a matrix which contains a counter for each possible allocation, i.e. a total of 16 counters. If it was established by the comparison in step 16 therefore e.g. that the measured value M2, which is linked with a particular identification, coincides best with the feature M1, which is linked with the position FL, then the counter status is increased by ONE in the counter which is allocated to the particular identification and to the position FL. This is carried out repeatedly for each measured value M2 transmitted by the tire pressure control devices and for each coincidence of a measured value M2 with one of the measured values M1 the counter status is increased by ONE in the counter which is allocated to the associated identification and the corresponding wheel position. This takes place in step 18.

(22) After the step 18, the first measured values M1, which form the basis of the entry into the matrix, can be deleted, in particular in that they are overwritten with the subsequent first measured values M1.

(23) In a step 19 after each increase of a counter status a check is made as to whether in the four counters, which are allocated to one of the four wheel positions, one of the four identifications has reached a counter status which is significantly higher than the counter status reached for the other three identifications. As long as this is not the case, the method according to FIG. 1 is not terminated for the corresponding tire pressure control device. If, however, the counter status for an identification paired with a particular wheel position has increased significantly above the three other counter statuses for the same wheel position, the identification is stored under the corresponding wheel position in the step 20, and in a step 21 the allocation method for the respective wheel position is terminated by a radio signal sent from the central unit 22 to the corresponding tire pressure control device. Thereafter, only the normal tire pressure control takes place in the allocated tire pressure control device.

(24) The terminating of the allocation method can be decided and brought about separately for the four tire pressure control devices. As soon as three allocations have fulfilled the criterion for the termination of the allocation method, the method for the fourth and final allocation can also be terminated, because the final allocation inevitably results from the three previous allocations.

(25) The allocation methods can, however, also be terminated simultaneously.

(26) FIG. 3 shows diagrammatically about which angle a wheel 24, rotating anti-clockwise, rotates further anti-clockwise in the time interval t.sub.2, which passes between the end of the detecting of a measurand from which the rotation speed of the wheel 24 can be derived and the sending of the second measured value M2 obtained therefrom. At a speed of approximately 15 km/h, the tire pressure control device is activated. It is assumed that the tire pressure control device at 15 km/h sends from the angular position 25 which lies at the beginning of the path 26. Whilst the speed increases up to 100 km/h, the position from which the tire pressure control sends travels along the path 26 anti-clockwise up to the position 27. On exceeding 100 km/h or respectively on exceeding a wheel rotation speed corresponding to this speed, which is determined by means of the acceleration sensor in the tire pressure control device, this shortens the time interval t.sub.2 in a stage so that at speeds between 100 km/h and e.g. 200 km/h the position of the sending tire pressure control device moves along the path 28. The illustrated movement takes place for the two speed ranges respectively provided that the tire pressure control device, at the end of the detecting of the measurand from which the rotation speed can be derived, is always situated in the same angular position, e.g. in the 3 o'clock position 29.

(27) In summary, the invention relates to a method for the allocating of tire pressure control devices of a tire pressure control system of a vehicle to the different wheel positions at which respectively a wheel of the vehicle is mounted. First sensors, which are fixedly allocated to the wheel positions, deliver repeatedly a measured value M1, which is a measurement for the rotation speed of the wheel to which the respective first sensor is allocated. In each tire pressure control device the development of a measurand, from which the rotation speed of the associated wheel can be derived, is detected in a pointwise manner by means of a second sensor over a predetermined rotation angle of the wheel as a function of time, is subjected to a low pass filtering in a subsequent first time interval t1 and from the filtered development of the measurand a second measured value M2 is determined, which is a measurement for the rotation speed or respectively for the angular speed of the associated wheel. Each tire pressure control device transmits at the end of a second time interval t2, the duration of which is not less than the first time interval t1, the second measured value M2 together with an identification of the tire pressure control device to a central unit; in the central unit, as a result of this transmittal, the second measured values M2 transmitted by the tire pressure control devices are compared with the measured values M2 detected in a timely manner by the first sensors of all wheels, and the identification of the tire pressure control device is stored under that wheel position in which the measured value M1 delivered by the first sensor best coincides with the measured value M2.

NUMERALS

(28) 1-21 steps 22 central unit 23 processing unit 24 wheel 25 angular position 26 path 27 position 28 path 29 3 o'clock position M1 first measured value M2 second measured value T1 first time span T2 second time span T time segment t.sub.1 first time interval t.sub.2 second time interval predetermined rotation angle T displacement of an angular position caused by t.sub.2