ROAD SURFACE CONDITION ESTIMATING METHOD, ROAD SURFACE CONDITION ESTIMATING TIRE, ROAD SURFACE CONDITION ESTIMATING APPARATUS, AND VEHICLE CONTROL APPARATUS

• US 20090105921A1
• Filed: 06/19/2006
• Published: 04/23/2009
• Est. Priority Date: 06/17/2005
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Bridgestone (Bridgestone Corporation)
• Original Assignee: Kabushiki Kaisha Bridgestone (Bridgestone Corporation)
• Inventors: Hanatsuka, Yasushi, Morinaga, Hiroshi
• Granted Patent: US 9,046,457 B2
• Time in Patent Office: Days
• US Class Current: 701/80
• CPC Class Codes: B60G 17/0165 to an external condition, e.g. rough road surface, side wind
• CPC Class Codes: B60G 2204/113 Tyre related sensors
• CPC Class Codes: B60G 2400/206 Body oscillation speed; Body vibration frequency
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2400/821 Uneven, rough road sensing affecting vehicle body vibration
• CPC Class Codes: B60G 2600/70 Computer memory; Data storage, e.g. maps for adaptive control
• CPC Class Codes: B60G 2800/162 Reducing road induced vibrations
• CPC Class Codes: B60G 2800/702 Improving accuracy of a sensor signal
• CPC Class Codes: B60G 2800/916 Body Vibration Control
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 8/1725 Using tyre sensors, e.g. Sidewall Torsion sensors [SWT] for tyre pressure and temperature detection B60C23/00
• CPC Class Codes: B60W 2422/70 on the wheel or the tire
• CPC Class Codes: B60W 2552/35 Road bumpiness, e.g. potholes
• CPC Class Codes: B60W 40/06 Road conditions
• CPC Class Codes: G01N 19/02 Measuring coefficient of friction between materials testing of tyres G01M17/02; determinations of friction coefficient used in vehicle braking or traction control systems B60T8/172

Abstract

The vibration of a tire 10 of a running vehicle in the circumferential direction or the width direction is detected by a road surface condition estimating tire 10, provided with an acceleration sensor 11 and a signal processing unit 12. Data of a detected vibration waveform are divided into data of three domains, namely, a pre-leading domain, a contact patch domain, and a post-trailing domain, and then the vibration levels in the pre-leading domain and the contact patch domain, respectively, are extracted. At the same time, a vibration component in a low-frequency band and a vibration component in a high-frequency band are extracted respectively from the vibration levels in the respective domains, and respective vibration level ratios R, which are each a ratio thereof, are calculated. Then, on the vehicle body side, the condition of a road surface on which the vehicle is running is estimated, based on the calculated vibration level ratio R and a map 32M, stored in a storage means 32, showing a relationship between the vibration level ratio R of tire vibration and road surface conditions. Thus a road surface condition can be estimated with accuracy even when there are changes in temperature or vehicle speed.

Claims

1. A road surface condition estimating method comprising:

detecting the vibration of a tire of a running vehicle;

dividing the detected tire vibration into vibration in a pre-trailing domain, the domain existing before a trailing edge position, and vibration in a post-trailing domain, the domain existing after a trailing edge position, and at the same time

extracting signals of tire vibration in the pre-trailing domain or signals of tire vibration in a time range corresponding to the pre-trailing domain;

obtaining a frequency spectrum by analyzing the frequencies of the extracted signals; and

thereafter

calculating a vibration level in a predetermined frequency band from the obtained frequency spectrum; and

estimating a road surface condition based on the calculated vibration level.

3. The road surface condition estimating method according to claim 1 or 2, wherein the pre-trailing domain is any or all of a pre-leading domain, the domain existing before a leading edge position, a contact patch domain, the domain existing from the point of tire touching a road surface to the point of tire leaving it, and a domain covering the pre-leading domain and contact patch domain.

4. The road surface condition estimating method according to any one of claims 1 to 3, wherein the trailing edge position is estimated from a peak position of the tire vibration appearing near the tire contact patch.

5. The road surface condition estimating method according to claim 4, wherein the peak position of tire vibration is the peak position of tire vibration in the tire circumferential direction or the tire width direction occurring at a trailing edge.

6. The road surface condition estimating method according to claim 3, wherein a wheel speed is measured and a length of the pre-trailing domain of tire vibration or a time range corresponding to the pre-trailing domain is determined from data of the measured wheel speed.

7. The road surface condition estimating method according to any one of claims 1 to 6, wherein vibration levels in at least two frequency bands are calculated from the frequency spectrum or the time-series waveform, and a road surface condition is estimated from a vibration level computed value calculated using the plurality of calculated vibration levels.

8. The road surface condition estimating method according to any one of claims 1 to 7, wherein signals of tire vibration of a running vehicle of at least two predetermined positions in the pre-trailing domain or at least two predetermined time ranges before the trailing edge time (point) are extracted, and a road surface condition is estimated using a vibration level computed value calculated using the vibration level of the plurality of signals or the plurality of vibration levels.

9. The road surface condition estimating method according to any one of claims 1 to 8, wherein the lower-limit frequency in the predetermined frequency band or the lower-limit frequency of at least one of the two frequency bands is 2,000 Hz or above.

10. The road surface condition estimating method according to claim 1 or any one of claims 3 to 6, wherein in addition to a vibration level of a predetermined frequency band obtained from a frequency spectrum of the pre-trailing domain, a vibration level in a frequency band lower than the predetermined frequency range is calculated from a frequency spectrum obtained by analyzing the frequencies of signals of the post-trailing domain, and a road surface condition is estimated based on a vibration level computed value calculated using the calculated vibration level in the pre-trailing domain and vibration level in the post-trailing domain.

12. The road surface condition estimating method according to claim 10 or claim 11, wherein the lower frequency band is selected from a frequency band of 0.5 to 4 kHz, and the higher frequency band is selected from a frequency band of 2 to 10 kHz.

13. The road surface condition estimating method according to any one of claims 10 to 12, wherein a wheel speed is measured and either or both of the lower frequency band and higher frequency band are changeable according to the data of the wheel speed.

14. The road surface condition estimating method according to any one of claims 10 to 12, wherein either or both of the lower frequency band and higher frequency band are changeable according to tire type.

15. The road surface condition estimating method according to any one of claims 10 to 14, wherein the vibration of a tire of a running vehicle is detected at least two points on the tire, vibration level computed values therefor are calculated respectively, and a road surface condition is estimated using an average value of the calculated vibration level computed values.

16. The road surface condition estimating method according to any one of claims 1 to 15, wherein a relationship between various road surface conditions and the vibration level or the vibration level computed value is determined previously, and a road surface condition is estimated based on the relationship.

17. The road surface condition estimating method according to any one of claims 1 to 16, wherein a road surface is decided to be slippery when the vibration level or vibration level computed value exceeds a predetermined threshold value.

18. The road surface condition estimating method according to any one of claims 1 to 17, wherein a vibration level of one or a plurality of specific frequency bands in a specific range within the pre-leading domain of tire vibration is calculated, and a decision is made as to whether an intervening matter exists between road surface and tire based on a vibration level computed value calculated from the vibration level or the plurality of vibration levels.

19. The road surface condition estimating method according to claims 18, wherein an intervening matter is decided to exist between road surface and tire when the vibration level or vibration level computed value in the specific frequency band exceeds a predetermined threshold value.

20. The road surface condition estimating method according to claim 18 or claim 19, wherein frequencies in the specific frequency band are frequencies that increase or decrease in relation to the vehicle speed.

21. The road surface condition estimating method according to claim 20, wherein the specific frequency band is a frequency band including a pattern pitch frequency of tire vibration.

22. The road surface condition estimating method according to claim 20, wherein the specific frequency band is a frequency band whose lower-limit frequency is higher than a pattern pitch frequency of tire vibration.

23. The road surface condition estimating method according to claim 17 or any one of claims 19 to 22, wherein the threshold value is changed according to the data of wheel speed.

24. The road surface condition estimating method according to claim 17 or any one of claims 19 to 22, wherein the threshold value is changed according to tire type.

25. The road surface condition estimating method according to any one of claims 1 to 24, wherein a road surface condition is estimated by detecting vibration at least two points on the tire circumference.

2. A road surface condition estimating method comprising:

detecting the vibration of a tire of a running vehicle;

dividing the detected tire vibration into vibration in a pre-trailing domain, the domain existing before a trailing edge position, and vibration in a post-trailing domain, the domain existing after a trailing edge position, and at the same time

extracting signals of tire vibration in the pre-trailing domain or signals of tire vibration in a time range corresponding to the pre-trailing domain;

obtaining a time-series waveform of tire vibration including only the frequencies in a predetermined frequency range by passing the extracted signals through a band-pass filter of the predetermined frequency band; and

thereafter

calculating a vibration level in the predetermined frequency band from the obtained time-series waveform of tire vibration; and

estimating a road surface condition based on the calculated vibration level.

11. The road surface condition estimating method according to any one of claims 2 to 6, wherein in addition to a vibration level of a predetermined frequency band obtained from a time-series waveform of tire vibration in the pre-trailing domain obtained through a band-pass filter of the predetermined frequency band, a vibration level of a frequency band lower than the predetermined frequency band in the post-trailing domain, the frequency band obtained by passing signals of the post-trailing domain through a band-pass filter of the frequency band lower than the predetermined frequency range, is calculated, and a road surface condition is estimated based on a vibration level computed value calculated using the calculated vibration level in the pre-trailing domain and vibration level in the post-trailing domain.

26. A road surface condition estimating tire comprising:

a tire vibration detecting means disposed on the air chamber side of an inner liner in a tire tread area, the tire vibration detecting means detecting the vibration of a tire of a running vehicle; and

a signal extracting means for extracting signals of the pre-trailing domain of the tire vibration detected by the tire vibration detecting means.

27. The road surface condition estimating tire according to claim 26, further comprising:

a frequency analysis means for analyzing the frequencies of signals extracted by the signal extracting means; and

a vibration level calculating means for calculating a vibration level of a predetermined frequency band from a frequency spectrum obtained by the frequency analysis means.

28. The road surface condition estimating tire according to claim 26, further comprising:

a band-pass filter for extracting signals of a predetermined frequency band from signals extracted by the signal extracting means; and

a vibration level calculating means for calculating a vibration level of the predetermined frequency band from a time-series waveform of the extracted tire vibration.

29. The road surface condition estimating tire according to claim 27 or claim 28, further comprising:

a means for calculating vibration levels of at least two frequency bands from the frequency spectrum or the time-series waveform; and

a means for calculating a vibration level computed value using the plurality of calculated vibration levels.

30. The road surface condition estimating tire according to claim 26, further comprising:

a signal extracting means for extracting signals tire vibration in the post-trailing domain, in addition to the signals of tire vibration in the pre-trailing domain.

31. The road surface condition estimating tire according to claim 30, further comprising:

a frequency analysis means for analyzing the frequencies of the signals of the pre-trailing domain and signals of the post-trailing domain extracted by the signal extracting means;

a vibration level calculating means for calculating a vibration level of a frequency band, the lower-limit frequency of which being 0.5 kHz or above and the upper-limit frequency of which being 4 kHz or below, from a frequency spectrum of the post-trailing domain obtained by the frequency analysis means, and a vibration level of a frequency band, the lower-limit frequency of which being 2 kHz or above and the upper-limit frequency of which being 10 kHz or below, from a frequency spectrum of the pre-trailing domain obtained thereby; and

a means for calculating a vibration level computed value using the calculated vibration level in the post-trailing domain and vibration level in the pre-trailing domain.

32. A road surface condition estimating tire according to claim 30, further comprising:

a band-pass filter for extracting respective signals of mutually different predetermined frequency bands by inputting the signals of the post-trailing domain and signals of the pre-trailing domain extracted by the signal extracting means;

a vibration level calculating means for calculating a vibration level of a frequency band, the lower-limit frequency of which being 0.5 kHz or above and the upper-limit frequency of which being 4 kHz or below, from the extracted time-series waveform of the post-trailing domain, and a vibration level of a frequency band, the lower-limit frequency of which being 2 kHz or above and the upper-limit frequency of which being 10 kHz or below, from the time-series waveform of the pre-trailing domain; and

a means for calculating a vibration level computed value using the calculated vibration level in the post-trailing domain and vibration level in the pre-trailing domain.

33. The road surface condition estimating tire according to any one of claims 26 to 32, further comprising:

a means for wirelessly transmitting data of the vibration level or vibration level computed value to the vehicle body side.

34. The road surface condition estimating tire according to any one of claims 26 to 33, wherein the tire vibration detecting means is a tire vibration detecting means for detecting tire vibration in the circumferential direction.

35. The road surface condition estimating tire according to any one of claims 26 to 33, wherein the tire vibration detecting means is a tire vibration detecting means for detecting vibration in the tire width direction.

36. The road surface condition estimating tire according to any one of claims 26 to 35, wherein the tire vibration detecting means is disposed at the center of the tire width.

37. The road surface condition estimating tire according to any one of claims 26 to 35, wherein the tire vibration detecting means is disposed a predetermined distance apart in the width direction from the center of the tire width.

38. The road surface condition estimating tire according to any one of claims 26 to 37, wherein the tire vibration detecting means is a tire vibration detecting means capable of detecting up to 20,000 Hz of tire vibration.

39. The road surface condition estimating tire according to any one of claims 26 to 38, wherein the tire vibration detecting means is disposed at least two points on the tire circumference.

40. The road surface condition estimating apparatus comprising:

a reception means for receiving data of a vibration level or a vibration level computed value wirelessly transmitted from a road surface condition estimating tire according to any one of claims 33 to 39; and

a road surface condition estimating means for estimating a road surface condition based on the received data of a vibration level or a vibration level computed value.

41. The road surface condition estimating apparatus according to claim 40, further comprising:

a storage means for storing a map of a previously determined relationship between various road surface conditions and the vibration level or the vibration level computed value, wherein a road surface condition is estimated using the received data of vibration level or vibration level computed value and the map.

42. The road surface condition estimating apparatus according to claim 40, further comprising:

a storage means provided on the tire side, the storage means storing a map of a previously determined relationship between various road surface conditions and the vibration level or the vibration level computed value; and

a reading means provided on the vehicle body side, the reading means reading information of the map, wherein a road surface condition is estimated, on the vehicle body side, based on the map information read as above.

43. The road surface condition estimating apparatus according to any one of claims 40 to 42, further comprising:

a transmission means for wirelessly transmitting information of the estimated road surface condition to another vehicle.

44. The road surface condition estimating apparatus according to claim 43, further comprising:

a reception means for receiving the wirelessly transmitted information on a road surface condition; and

a means for grasping a road surface condition ahead from information on a road surface condition transmitted from a vehicle running ahead.

45. The vehicle control apparatus comprising:

a road surface condition estimating apparatus according to claim 43;

an inter-vehicular distance estimating means for estimating the distance to a vehicle ahead;

a wheel speed detecting means; and

a running condition control means for controlling the running condition of a vehicle based on road surface information from the means for grasping a road surface condition ahead, inter-vehicular distance information from the inter-vehicular distance estimating means, and wheel speed information from the wheel speed detecting means.