Method and apparatus for estimating road surface state and tire running state, ABS and vehicle control using the same
First Claim
1. A method of estimating the condition of a road and the running state of a tire, comprising:
- detecting a vibration of a tire, a wheel or a suspension of a running car; and
detecting a vibration level of a vibration spectrum obtained by analyzing the frequency of the detected vibration to estimate the condition of the road at the time of running, and the running state of the tires,wherein the bandwidth of the frequency band for detecting the vibration level is 1 to 100% of that of a detection frequency band, andwherein the vibration level at a frequency band of at least 10 to 10,000 Hz of the vibration spectrum is detected.
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Accused Products
Abstract
The frequency of an information signal indicative of a-vibration of a wheel detected by an acceleration sensor mounted to a wheel; or a change in the pressure of a gas in a tire detected by a pressure sensor installed in the tire, is analyzed. The band value of the obtained vibration spectrum or pressure change spectrum is detected, and a vibration level or pressure change level at the detected frequency band is compared with: a vibration level table showing the relationship between road friction coefficient μ and vibration level; or a pressure change level table showing the relationship between road friction coefficient μ and pressure change level, to estimate a road friction coefficient μ. Therefore, it is possible to estimate the value of road friction coefficient μ accurately and improve the safety of a car.
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Citations
91 Claims
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1. A method of estimating the condition of a road and the running state of a tire, comprising:
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detecting a vibration of a tire, a wheel or a suspension of a running car; and detecting a vibration level of a vibration spectrum obtained by analyzing the frequency of the detected vibration to estimate the condition of the road at the time of running, and the running state of the tires, wherein the bandwidth of the frequency band for detecting the vibration level is 1 to 100% of that of a detection frequency band, and wherein the vibration level at a frequency band of at least 10 to 10,000 Hz of the vibration spectrum is detected. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of estimating the condition of a road and the running state of a tire, comprising:
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detecting a change in the pressure of a gas filled in the tire of a running car; and detecting a pressure change level of a pressure change spectrum obtained by analyzing the frequency of the detected pressure change to estimate the condition of the road at the time of running, and the running state of the tire. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A road condition and tire running state estimation apparatus comprising:
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vibration detection means for detecting a vibration of a tire or a wheel of a running car; means for detecting a vibration level in a frequency band in a frequency range of at least 10 to 10,000 Hz of a frequency spectrum obtained by analyzing the frequency of the detected vibration; and means for estimating a condition of a road at the time of running, and a running state of the tire, from the detected vibration level wherein the vibration detection means is mounted on the same substrate, or in the same housing, as a pressure sensor for monitoring a pressure of a gas filled in the tire. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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43. A road condition and tire running state estimation apparatus comprising:
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vibration detection means for detecting a vibration of the suspension of a running car; means for detecting a vibration level in a frequency band in a frequency range of at least 10 to 10,000 Hz of a frequency spectrum obtained by analyzing the frequency of the detected vibration; and means for estimating a condition of a road at the time of running, and a running state of the tire, from the detected vibration level. - View Dependent Claims (44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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55. A road condition and tire running state estimation apparatus comprising:
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pressure change detection means for detecting a change in the pressure of a gas filled in a tire of a running car; means for detecting a pressure change level in a frequency band in a frequency range of at least 10 to 10,000 Hz of a pressure change spectrum obtained by analyzing the frequency of the detected pressure change; and means for estimating a condition of a road at the time of running, and a running state of the tire, from the detected pressure change level. - View Dependent Claims (56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66)
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67. A road condition estimation method for:
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
detecting the vibration level of a vibration spectrum or the pressure change level of a pressure change spectrum obtained by analyzing the frequency of the vibration or the pressure change,wherein, an ON/OFF state of a brake switch is detected, and when it is judged that the brake is stepped on, updating of the estimated value of the road friction coefficient is suspended. - View Dependent Claims (68)
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
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69. A road condition estimation method for:
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
detecting the vibration level of a vibration spectrum or the pressure change level of a pressure change spectrum obtained by analyzing the frequency of the vibration or the pressure change,wherein, a slip ratio is calculated by detecting a speed of a driving wheel and a speed of a coupled driving wheel, and when the slip ratio exceeds a preset threshold value, updating of the estimated value of road friction coefficient is suspended. - View Dependent Claims (70)
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
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71. A road condition estimation method for:
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
detecting the vibration level of a vibration spectrum or the pressure change level of a pressure change spectrum obtained by analyzing the frequency of the vibration or the pressure change,wherein, an engine speed is detected, and when the engine speed exceeds a preset threshold value, updating of the estimated value of the road friction coefficient is suspended. - View Dependent Claims (72, 73, 74)
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
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75. A road condition estimation apparatus for:
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
detecting the vibration level of a vibration spectrum or the pressure change level of a pressure change spectrum obtained by analyzing the frequency of the vibration or the pressure change,wherein, the apparatus comprises means for detecting an ON/OFF state of a brake switch, and when it is judged that the brake is stepped on, updating of the estimated value of the road friction coefficient is suspended. - View Dependent Claims (76)
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
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77. A road condition estimation apparatus for:
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
detecting the vibration level of a vibration spectrum or the pressure change level of a pressure change spectrum obtained by analyzing the frequency of the vibration or the pressure change,wherein, the apparatus comprises means for detecting speeds of a driving wheel and a coupled driving wheel and means of calculating a slip ratio from the detected speeds of the driving wheel and the coupled driving wheel, and when the slip ratio exceeds a preset threshold value, updating of the estimated value of road friction coefficient is suspended. - View Dependent Claims (78)
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
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79. A road condition estimation apparatus for:
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
detecting the vibration level of a vibration spectrum or the pressure change level of a pressure change spectrum obtained by analyzing the frequency of the vibration or the pressure change,wherein, the apparatus comprises means for detecting an engine speed, and when the engine speed exceeds a preset threshold value, updating of the estimated value of the road friction coefficient is suspended. - View Dependent Claims (80, 81, 82)
- estimating a value of a road friction coefficient by detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of the tire; and
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83. An ABS brake control method comprising:
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detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of a tire; detecting a vibration level of a vibration spectrum or a pressure change level of a pressure change spectrum obtained by analyzing the frequency of the vibration or the pressure change to estimate a road friction coefficient continuously; and changing a threshold value of an oil pressure of a brake for shifting to ABS control according to the estimated value of road friction coefficient right before a driver steps on the brake. - View Dependent Claims (84)
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85. An ABS brake control method comprising:
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detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of a tire; detecting a vibration level of a vibration spectrum, or a pressure change level of a pressure change spectrum, obtained by analyzing the frequency of the vibration or the pressure change to estimate a road friction coefficient continuously; and adjusting a change in the oil pressure of an ABS brake according to the estimated value of road friction coefficient right before a driver steps on the brake. - View Dependent Claims (86)
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87. An ABS brake control apparatus comprising:
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means for detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of a tire; means for detecting a vibration level of a vibration spectrum or a pressure change level of a pressure change spectrum obtained by analyzing the frequency of an information signal indicative of the detected vibration or the detected pressure change to calculate the estimated value of a road friction coefficient continuously as=1/[1+exp{−
(a0+a1x1+a2x2+ . . . +anxn)}], wherein a0 is a constant, a1, a2, . . . and an are coefficients and xi is a vibration level or pressure change level at a frequency band (fi);means for detecting the ON/OFF state of a brake switch; and means for changing a threshold value of an oil pressure of a brake for shifting to ABS control according to the estimated value of the road friction coefficient right before a driver steps on the brake. - View Dependent Claims (88, 89)
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90. An ABS control apparatus comprising:
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means for detecting at least one of a tire vibration, a wheel vibration, a suspension vibration and a change in the inside pressure of a tire; means for detecting a vibration level of a vibration spectrum or a pressure change level of a pressure change spectrum obtained by analyzing the frequency of an information signal indicative of the detected vibration or the detected pressure change to calculate the estimated value of a road friction coefficient continuously as=1/[1+exp{−
(a0+a1x1+a2x2+ . . . +anxn)}], wherein a0 is a constant, a1, a2, . . . and an are coefficients and xi is a vibration level or pressure change level at a frequency band (fi);means for detecting the ON/OFF state of a brake switch; and means for adjusting a change in the oil pressure of an ABS brake according to the estimated value of the road friction coefficient right before a driver steps on the brake. - View Dependent Claims (91)
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Specification