Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2001-03-29
2002-05-07
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S070000, C701S071000, C280S005514
Reexamination Certificate
active
06385525
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus mounted on a vehicle for detecting a condition of a road surface while the vehicle is traveling.
2. Description of the Related Art
U.S. Pat. No. 5,719,565 corresponding to Japanese patent application publication number 9-20223 discloses an apparatus mounted on a vehicle for detecting a condition of a road surface while the vehicle is traveling. In the apparatus of U.S. Pat. No. 5,719,565, the speeds of wheels of the vehicle are calculated based on wheel speed signals from wheel speed sensors. The accelerations of the wheels are calculated based on the calculated wheel speeds. High frequency components of the calculated wheel accelerations are filtered using high-pass filters to obtain the frequency components of the wheel accelerations which are due only to the road-surface condition. A variance among a limited number of temporally-spaced samples of each filtering-resultant wheel acceleration is calculated, and a determination is made as to whether or not the road-surface condition is bad by referring to the calculated variance. Specifically, when the calculated variance is equal to or greater than a reference value, it is determined that the road-surface condition is bad.
A typical wheel speed sensor includes a rotor which rotates together with a related vehicle wheel. The rotor has teeth. The typical sensor also includes a fixed portion for sensing every projection or every groove in the rotor teeth and thereby generating a wheel speed signal during the rotation of the rotor. In the case where the typical sensor is used by the apparatus of U.S. Pat. No. 5,719,565, a variation in shape and position among the projections or the grooves in the rotor teeth affects the calculated variance. Thus, the variation in shape and position among the projections or the grooves in the rotor teeth lowers the accuracy of the determination as to whether or not the road-surface condition is bad.
Japanese patent application publication number 6-80044 discloses an apparatus mounted on a vehicle for detecting a condition of a road surface while the vehicle is traveling. In the apparatus of Japanese application 6-80044, vehicle wheel speed data are derived from the output signal of a vehicle wheel speed sensor. A differential value of the vehicle wheel speed data is calculated for every unit time. Factors of a sequence of samples of data representing the calculated differential values are calculated as feature quantities related to the vehicle wheel speed. Specifically, with respect to the sample sequence, a mean amplitude, a relative amplitude variation, a histogram variance, and the number of data pieces in an amplitude value specified interval are calculated for every unit time. A fuzzy inference is implemented while the calculated feature quantities are used as input parameters. A determination is made as to whether the road-surface condition is good or bad on the basis of the result of the fuzzy inference.
U.S. Pat. No. 5,760,682 corresponding to Japanese patent application publication number 10-258618 discloses a method for detecting a deflated tire on a vehicle. In the method of U.S. Pat. No. 5,760,682, wheel speed values for each of four wheels are collected and analyzed for a statistical variation which would indicate low tire pressure. Prior to analysis, and following reset of the system, calibration factors are determined for each of the wheels to compensate rolling radius variations, and subsequently used to correct all wheel speed values. The corrected speed values are then filtered to exclude values which represent wheel slippage, rough road fluctuations, vehicle cornering, and uphill or downhill travel. When a sufficient number of values have been collected, an F-value is calculated substantially according to the statistical method “analysis of the variance”, and the F-value is compared to an empirically determined value corresponding to a predetermined pressure loss. This comparison can provide the basis for a driver warning. Since a larger F-value indicates a larger statistical difference in wheel speeds, the value can be rechecked after a further interval for additional pressure loss.
U.S. Pat. No. 4,651,290 corresponding to Japanese patent application publication number 6-318297 discloses an apparatus mounted on a vehicle for detecting a condition of a road surface while the vehicle is traveling. In the apparatus of U.S. Pat. No. 4,651,290, the speed of a wheel of the vehicle is calculated based on the output signal of a wheel speed sensor. The acceleration of the wheel is calculated based on the calculated wheel speed. The performance criterion of the road-surface condition is computed based on the calculated wheel acceleration. The computed performance criterion is compared with a setting value to determine wether the road-surface condition is good or bad. A first example of the performance criterion depends on a variance among a predetermined number of temporally-spaced samples of the wheel acceleration. A second example of the performance criterion depends on the number of samples of the wheel acceleration which exceed a reference value for every predetermined time interval. A third example of the performance criterion depends on the difference between the maximum and the minimum among the values indicated by temporally-spaced samples of the wheel acceleration for every predetermined time interval.
Japanese patent application publication number 5-126571 discloses an apparatus mounted on a vehicle for measuring the shape of a road surface. The apparatus of Japanese application 5-126571 includes a distance detector for detecting the distance between the road surface and a main body of the vehicle. The apparatus also includes an acceleration detector for detecting the vertical acceleration of the main body of the vehicle. The detected vertical acceleration is integrated on a second-order basis to calculate the amount of vertical vibration of the main body of the vehicle for every time interval corresponding to a predetermined distance traveled by the vehicle. The detected distance between the road surface and the main body of the vehicle is corrected in response to the calculated amount of vertical vibration. The shape of the road surface is detected on the basis of the correction resultant distance.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an apparatus for accurately detecting a condition of a road surface even in the case where there is a variation in shape and position among the projections or the grooves in teeth of a rotor of a wheel speed sensor.
A first aspect of this invention provides an apparatus for detecting a condition of a road surface. The apparatus comprises vehicle wheel speed detecting means for outputting a vehicle wheel speed signal representing a speed of a wheel of a vehicle; vehicle wheel speed summating means for summating variations in the vehicle wheel speed represented by the vehicle wheel speed signal during every time period corresponding to one revolution of the vehicle wheel, and for generating a summation value representing a result of said summating; and road-surface condition detecting means for detecting a road-surface condition on the basis of a difference between a current summation value and a previous summation value generated by the vehicle wheel speed summating means.
A second aspect of this invention is based on the first aspect thereof, and provides an apparatus further comprising vehicle wheel acceleration calculating means for calculating an acceleration of the vehicle wheel from the vehicle wheel speed signal outputted from the vehicle wheel speed detecting means; and means provided in the vehicle wheel speed summating means for summating variations in the vehicle wheel acceleration calculated by the vehicle wheel acceleration calculating means, and for using a result of summating the variations in the vehicle wheel acceleration as a result of summating the variations in the vehicle wheel speed.
A third aspect of
Masaki Shoichi
Watanabe Takashi
Cuchlinski Jr. William A.
Denso Corporation
Law Offices of David G. Posz
Marc-Coleman Marthe Y.
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