Road surface condition estimating apparatus and variation reduction processing apparatus

• US 6,324,461 B1
• Filed: 06/29/1998
• Issued: 11/27/2001
• Est. Priority Date: 06/27/1997
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Umeno, Takaji, Ono, Eiichi, Asano, Katsuhiro, Yamaguchi, Hiroyuki, Sugai, Masaru
• Primary Examiner(s): Nguyen, Tan
• Assistant Examiner(s): Tran, Dalena
• Application Number:
  US09/106,342
• Time in Patent Office: 1,247 Days
• Field of Search: 701/80, 701/1, 701/36, 701/73, 701/71, 701/79, 303/149, 303/150, 303/163, 303/160, 303/194, 180/197, 73/105, 340/514
• US Class Current: 701/80
• CPC Class Codes: B60T 2210/12 Friction
• 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

Abstract

Disclosed is a road surface condition estimating apparatus including: a converting portion having a table showing a relation among a vehicle speed, a braking force and a resonance gain for each road surface condition and converting a detected value of the input vehicle speed and braking force into a resonance gain on the basis of the table, a subtracting device for computing each of differences between the resonance gain for each road surface condition converted by each of the converting portions and the detected value of the input resonance gain, and a minimum value selecting portion selecting the minimum value among the computed values in the subtracting device and outputting an information of the road surface condition corresponding to the converting portion giving the minimum value.

Claims

1. A road surface condition estimating apparatus, comprising:

a first detector configured to detect a first physical amount related to a braking condition of a wheel of a vehicle;

a second detector configured to detect a vehicle speed of said vehicle;

a third detector configured to detect a second physical amount which represents a slipperiness of said wheel and which is determined in accordance with a road surface condition based on a road surface on which said wheel runs, said first physical amount, and said vehicle speed;

a calculator configured to calculate a calculated second physical amount for each of a plurality of predetermined road surface conditions based on said first physical amount and said vehicle speed;

a comparator configured to compare a detected track of said second physical amount detected by said third detector with a plurality of calculated tracks of said calculated second physical amounts calculated for each of the plurality of predetermined road surface conditions by said calculator; and

an estimator configured to estimate a road surface condition corresponding to a calculated track closest to said detected track selected from said plurality of calculated tracks based on a result provided by said comparator, wherein;

said first physical amount is one of a braking force on the wheel and a slip speed; and

said second physical amount is one of a gradient of a coefficient of friction μ

between the road surface and the wheel with respect to a slip speed, a gradient of a braking torque on the wheel with respect to the slip speed, and a gradient of a braking force on the wheel with respect to the slip speed.

2. A road surface condition estimating apparatus according to claim 1, wherein:

said first detector, said second detector, and said third detector respectively detect the first physical amount, the vehicle speed, and the second physical amount at predetermined time intervals from a start time of braking on said wheel;

said calculator calculates the second physical amount for each of said plurality of predetermined road surface conditions at each predetermined time interval that the first physical amount changes by a predetermined amount relative to an initial first physical amount detected at the start time of braking on the wheel; and

said comparator compares the second physical amount detected at said predetermined time intervals with each of the second physical amounts calculated for each of the plurality of predetermined road surface conditions at each predetermined time interval that the first physical amount changes by a predetermined amount from the start time of braking on said wheel.

3. A road surface condition estimating apparatus comprising:

a first detector configured to detect a first physical amount related to one of a brake condition and a driving condition of a wheel of a vehicle;

a second detector configured to detect a vehicle speed of said vehicle;

a third detector configured to detect a second physical amount which represents a slipperiness and which is determined in accordance with a road surface condition corresponding to a road surface on which said wheel runs, said first physical amount, and said vehicle;

a reduction processor configured to reduce variations in the second physical amount detected by said third detector in accordance with a change in said first physical amount and to yield a variation-reduced second physical amount;

a calculator configured to calculate a calculated second physical amount for each of a plurality of predetermined road surface conditions based on the first physical amount and the vehicle speed;

a comparator configured to compare a detected track of the variation-reduced second physical amount with each of a plurality of calculated tracks of the calculated second physical amount; and

an estimator configured to estimate a road surface condition corresponding to a calculated track selected from said plurality of calculated tracks closest to said detected track among said calculated tracks as being an actual road surface condition corresponding to said road surface on which said wheel runs based on a comparison result of said comparator.

4. A road surface condition estimating apparatus according to claim 3, wherein said reduction processor is configured to perform one of filter variations in said second physical amount at a time said first physical amount changes by a predetermined amount and calculate an average of said second physical amount over the time said first physical amount changes by said predetermined amount.

5. A road surface condition estimating apparatus according to claim 3, wherein said first physical amount is one of a braking force on the wheel and a slip speed.

6. A road surface condition estimating apparatus according to claim 3, wherein said second physical amount is one of a gradient of a coefficient of friction between the road surface and the wheel with respect to a slip speed, a gradient of braking torque on the wheel with respect to the slip speed, and a gradient of braking force on the wheel with respect to the slip speed.

7. A road surface condition estimating apparatus according to claim 3, wherein:

said first detector, said second detector, and said third detector respectively detect the first physical amount, the vehicle speed, and the second physical amount at a predetermined interval from a start time of braking on the wheel;

said calculator calculates the second physical amount for each of said plurality of predetermined road surface conditions at each predetermined time interval that the first physical amount changes by a predetermined amount relative to an initial first physical amount detected at the start time of braking on the wheel; and

said comparator compares the second physical amount detected at said predetermined time intervals with each of the second physical amounts calculated at each of the second physical amounts calculated at each time the first physical amount changes by a predetermined amount, at each predetermined time interval that the first physical amount changes by said predetermined amount from the start time of braking on the wheel.

8. A road surface condition estimating apparatus, comprising:

means for detecting a plurality of wheel motion amounts, one of said wheel motion amounts related to one of a characteristic of a gradient of a coefficient of friction μ

between a wheel and a road surface with respect to a slip speed, a gradient of a braking torque on the wheel with respect to the slip speed, and a gradient of a braking force on the wheel with respect to the slip speed;

means for correlating at least one detected wheel motion amount of said plurality of wheel motion amounts with a converted wheel motion amount for each of a plurality of road surface conditions based on a correlation between said at least one detected wheel motion amount and each of a plurality of road surface conditions; and

means for estimating a road surface condition through comparison of said converted wheel motion amount with a further detected wheel motion amount of the plurality of wheel motion amounts.

9. A device for estimating a road condition, comprising:

a plurality of inputs configured to receive a plurality of detected wheel motion amounts describing the behavior of a vehicle during operation;

correlation information describing a relationship between at least one of said plurality of detected wheel motion amounts and a plurality of possible road conditions, said correlation information being characteristic of a gradient of a coefficient of friction between a tire and a road surface;

a storage device configured to store said correlation information;

a processor configured to process said some of said plurality of detected wheel motion amounts in light of said correlation information to yield a processed wheel motion amount for each of said possible road conditions;

a comparator configured to compare each of said processed wheel motion amounts with a particular detected wheel motion amount selected from said plurality of detected wheel motion amounts and output a plurality of comparison results; and

a selector configured to select a most relevant comparison result from said plurality of comparison results and to output a signal that indicates a most relevant road condition based upon said most relevant comparison result.

10. The apparatus of claim 9, wherein said particular detected wheel motion amount is a resonance gain.