Method for estimating vehicular running state, vehicular running state estimating device, vehicle control device, and tire wheel

• US 20020162389A1
• Filed: 06/07/2002
• Published: 11/07/2002
• Est. Priority Date: 06/23/2000
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Bridgestone
• Original Assignee: Kabushiki Kaisha Bridgestone
• Inventors: Yokota, Hidetoshi, Morinaga, Hiroshi, Otani, Koji
• Granted Patent: US 7,032,436 B2
• Time in Patent Office: Days
• US Class Current: 73/146
• CPC Class Codes: B60C 23/06 Signalling devices actuated by deformation of the tyre , e.g. tyre mounted deformation sensors or indirect determination of tyre deformation based on wheel speed, wheel-centre to ground distance or inclination of wheel axle
• CPC Class Codes: B60C 23/065 by monitoring vibrations in tyres or suspensions B60C23/062 takes precedence
• CPC Class Codes: B60G 17/0165 to an external condition, e.g. rough road surface, side wind
• CPC Class Codes: B60G 17/019 characterised by the type of sensor or the arrangement thereof B60G17/01941 takes precedence
• CPC Class Codes: B60G 17/0195 characterised by the regulation being combined with other vehicle control systems conjoint control of vehicle sub-units including control of suspension systems B60W10/22
• CPC Class Codes: B60G 2204/11 Mounting of sensors thereon
• CPC Class Codes: B60G 2204/113 Tyre related sensors
• CPC Class Codes: B60G 2400/102 vertical
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/206 Body oscillation speed; Body vibration frequency
• CPC Class Codes: B60G 2400/208 of wheel rotation
• CPC Class Codes: B60G 2400/52 in tyre
• CPC Class Codes: B60G 2400/821 Uneven, rough road sensing affecting vehicle body vibration
• CPC Class Codes: B60G 2400/91 Frequency
• CPC Class Codes: B60G 2600/02 Retarders, delaying means, dead zones, threshold values, cut-off frequency, timer interruption
• CPC Class Codes: B60G 2600/188 Spectral analysis; Transformations
• CPC Class Codes: B60G 2600/60 Signal noise suppression; Electronic filtering means
• CPC Class Codes: B60G 2600/604 low pass
• CPC Class Codes: B60G 2800/162 Reducing road induced vibrations
• CPC Class Codes: B60G 2800/70 Estimating or calculating vehicle parameters or state variables
• 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 2210/13 : Aquaplaning, hydroplaning
• CPC Class Codes: B60T 8/172 : Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• CPC Class Codes: G01H 1/003 : of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G01H 1/12 : of longitudinal or not specified vibrations
• CPC Class Codes: G01H 1/14 : Frequency
• 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
• CPC Class Codes: G01N 2203/0676 : Force, weight, load, energy, speed or acceleration
• CPC Class Codes: G01N 2203/0682 : Spatial dimension, e.g. length, area, angle
• CPC Class Codes: G01N 2203/0688 : Time or frequency
• CPC Class Codes: G01N 9/24 : by observing the transmission of wave or particle radiation through the material

Abstract

The output level (vibration level) of vibration of a portion below the spring of a vehicle detected by a vibration sensor mounted to the portion below the spring of the vehicle is frequency converted by frequency analyzing means 14F to obtain the frequency spectrum of the vibration level and an operation is carried out on at least two vibration levels at different frequency bands of the obtained frequency spectrum by vibration level computing means 14R, and this computed value is compared with a master curve showing the frequency spectrum of vibration level stored in vibration level storage means 16S to estimate the condition of a road surface so as to estimate the running state of the vehicle.

Further, the running state of each tire including the air pressure of the tire is detected from the vibration level of the portion below the spring of the vehicle to estimate the running state of the vehicle, thereby constructing a multi-function sensing system for estimating the condition of a road surface or the running state of the tire with one sensor.

Claims

1. A vehicle running state estimation method comprising the steps of:

detecting the vibration level of a portion below the spring of a running vehicle; and

estimating at least one of the condition of a road surface on which the vehicle is running and the running state of each tire based on the detected vibration level to estimate the running state of the vehicle.

2. The vehicle running state estimation method according to claim 1, wherein the waveform of time changes in the vibration level is detected and the condition of a road surface on which the vehicle is running is estimated from a vibration level at a predetermined position of this waveform or for a predetermined time range.

3. The vehicle running state estimation method according to claim 1, wherein the frequency of the detected vibration level is analyzed to calculate a vibration level at a predetermined frequency band and the condition of a road surface on which the vehicle is running is estimated from the calculated vibration level.

4. The vehicle running state estimation method according to claim 1, wherein the frequency of the above detected vibration level is analyzed, at least two vibration levels at different frequency bands are calculated, an operation is carried out on the above calculated vibration levels, and the condition of a road surface on which the vehicle is running is estimated from the computed value.

5. The vehicle running state estimation method according to claim 1, wherein the vibration levels of at least two points of a portion below the spring of a running vehicle are detected to calculate the vibration transmission level of the portion below the spring of the vehicle, and the condition of a road surface on which the vehicle is running is estimated from the calculated vibration transmission level.

6. A vehicle running state estimation apparatus comprising:

means of detecting the vibration level of a portion below the spring of a running vehicle;

means of computing the waveform of time changes in the vibration level; and

road surface condition estimation means for estimating the condition of a road surface on which the vehicle is running from a vibration level at a predetermined position of the waveform or for a predetermined time range.

7. The vehicle running state estimation apparatus according to claim 6 which further comprises means of calculating the vibration level of at least one of a tire leading edge portion, tire ground contact portion and tire trailing edge portion of the waveform.

8. A vehicle running state estimation apparatus comprising:

means of detecting the vibration level of a portion below the spring of a running vehicle;

means of calculating a vibration level at a predetermined frequency band by analyzing the frequency of the detected vibration level; and

road surface condition estimation means for estimating the condition of a road surface on which the vehicle is running from the calculated vibration level.

9. A vehicle running state estimation apparatus comprising:

means of detecting the vibration level of a portion below the spring of a running vehicle; and

road surface condition estimation means for estimating the condition of a road surface on which the vehicle is running from a value obtained by carrying out an operation on at least two vibration levels at different frequency bands by analyzing the frequency of the above detected vibration level.

10. A vehicle running state estimation apparatus comprising:

means of detecting the vibration levels of at least two points of a portion below the spring of a running vehicle;

means of calculating a vibration transmission level at a predetermined frequency band between the at least two of the vibration detection points; and

road surface condition estimation means for estimating the condition of a road surface on which the vehicle is running from the calculated vibration transmission level.

11. The vehicle running state estimation apparatus according to claim 10, wherein a vibration buffer member is interposed between the at least two vibration detection points.

12. The vehicle running state estimation apparatus according to any one of claims 8 to 11, wherein the relationship between road surface friction coefficient μ

obtained from the braking distances of a vehicle under various road conditions at different speeds and the vibration level at a predetermined frequency band, the computed value of vibration level or vibration transmission level is obtained previously and the road surface friction coefficient μ

at the time of running is estimated based on the relationship.

13. The vehicle running state estimation apparatus according to any one of claims 8 to 12, wherein the frequency band is a band including the frequency of natural vibration of a tire tread land portion.

14. The vehicle running state estimation apparatus according to any one of claims 8 to 13, wherein a threshold value is set for the vibration level and the surface of a road is estimated to be in a low friction condition when the calculated vibration level exceeds the threshold value.

15. The vehicle running state estimation apparatus according to claim 14, wherein the threshold value can be changed.

16. The vehicle running state estimation apparatus according to any one of claims 6 to 15 which further comprises vehicle speed detection means to estimate the condition of a road surface based on vehicle speed.

17. A vehicle running state estimation apparatus comprising the vehicle running state estimation apparatus of any one of claims 6 to 16, means of judging the slipperiness of a road surface based on the condition of the road surface estimated by the road surface condition estimation means and warning means for giving a warning when it is judged that the condition of the road surface is slippery.

18. The vehicle running state estimation apparatus according to claim 17 which further comprises vehicle speed detection means to change decision on the slipperiness of a road surface and warning level based on vehicle speed.

20. The vehicle running state estimation apparatus according to claim 19 which further comprises tire pressure monitoring means for monitoring the pressure of each tire while running using the estimated air pressure of the tire.

21. The vehicle running state estimation apparatus according to claim 20 which further comprises warning means for warning a passenger of a reduction in the pressure of the tire when the air pressure monitored by the tire pressure monitoring means falls below a predetermined value.

25. The vehicle running state estimation apparatus according to any one of claims 6 to 24 which further comprises a transmitter for transmitting the output of the vibration detection means for calculating a time change in vibration level or a vibration level at a predetermined frequency band.

26. The vehicle running state estimation apparatus according to any one of claims 6 to 25 further comprising a power generating unit which is mounted to a tire wheel, generates power by the rolling of each tire and supplies power for driving the vibration detection means or power for amplifying the output of the vibration detection means.

27. A vehicle control apparatus comprising vehicle control means for controlling the running state of a vehicle based on the condition of a road surface estimated by the vehicle running state estimation apparatus of any one of claims 6 to 26 and/or the running state of each tire.

32. The vehicle control apparatus according to claim 27 or 28, wherein the vehicle control means controls the idling state of each wheel.

34. A tire wheel comprising the vehicle running state estimation apparatus for estimating the running state of a vehicle by detecting the vibration level of a portion below the spring of a running vehicle as set forth in claims 6 to 26 and a power generating unit for generating power by the rolling of each tire and supplying power to the vehicle running state estimation apparatus.

19. A vehicle running state estimation apparatus comprising:

means of detecting the vibration level of a portion below the spring of a running vehicle;

means of estimating the air pressure of each tire by calculating the frequency of natural vibration of the tire from a vibration level at a frequency band of 200 Hz or less of the detected vibration level; and

tire running state estimation means for estimating the condition of each tire while running from the estimated air pressure of the tire.

22. A vehicle running state estimation apparatus comprising:

means of detecting the vibration level of a portion below the spring of a running vehicle;

tire revolution speed detection means;

tire running state estimation means for estimating the state of each tire while running by calculating the average value of vibration level changing by the revolution speed of the tire at a frequency band of 100 Hz or less of the detected vibration level; and

tire trouble detection means for judging that the tire is abnormal when the calculated average value of vibration level exceeds a preset reference value.

23. The vehicle running state estimation apparatus according to claim 22, wherein the reference value is set to a range of 1.2 to 5 times the vibration level at a reference decision frequency Fn when the vehicle runs at a predetermined speed V while the tire is not abnormal:

reference decision frequency Fn=n×

V/(2π

r)

wherein r is the rolling radius of the tire, and n is 1, 2, 3, . . .

24. The vehicle running state estimation apparatus according to claim 23, wherein the reference value can be changed.

28. The vehicle control apparatus according to claim 27 which comprises vehicle speed detection means to control the running state of a vehicle based on vehicle speed.

29. The vehicle control apparatus according to claim 27 or 28, wherein the vehicle control means controls the locked state of each wheel.

30. The vehicle control apparatus according to claim 27 or 28, wherein the vehicle control means controls the attitude of a vehicle.

31. The vehicle control apparatus according to claim 27 or 28, wherein the vehicle control means controls the air pressure of each tire.

33. The vehicle control apparatus according to claim 27 or 28, wherein the vehicle control means changes the inter-vehicle distance set value of an automatic driving system.

35. The tire wheel according to claim 34, wherein the vehicle running state estimation apparatus is mounted to the tire wheel.

36. The tire wheel according to claim 34 or 35, wherein the power generating unit comprises a rotor magnetized and rotated by the rolling of each tire, a stator made from a high magnetic permeability material and adjacent to the rotor and a power generating coil installed within a magnetic circuit including the rotor and the stator.

37. The tire wheel according to claim 36, wherein the power generating unit comprises means of accumulating electromotive force generated in the power generating coil.

38. The tire wheel according to claim 36 or 37, wherein the rotor is turned by rotating an unbalance weight the gravity center of the rotary cone of which is eccentric to a rotary shaft by the rolling of each tire.

39. The tire wheel according to claim 36 or 37, wherein an air stream generated by the rolling of each tire is introduced into the power generating unit and the rotor is turned by the introduced air stream.