Road surface state estimating device

• US 6,640,623 B2
• Filed: 10/15/2001
• Issued: 11/04/2003
• Est. Priority Date: 10/16/2000
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Tanaka, Akira, Umeno, Takaji, Ono, Eiichi, Sawada, Mamoru, Yasui, Yoshiyuki, Sugai, Masaru
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): DICKENS, CHARLENE
• Application Number:
  US09/976,163
• Publication Number:
  US 20020059824A1
• Time in Patent Office: 750 Days
• Field of Search: 731/46, 731/462, 731/463, 731/465, 731/468, 340/442-448, 152/415, 152/419
• US Class Current: 73/146
• 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
• CPC Class Codes: B60T 8/173 Eliminating or reducing the effect of unwanted signals, e.g. due to vibrations or electrical noise
• 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

In order to estimate a braking force gradient in a low slip region including a steady travelling region, there is provided a device comprising a wheel speed sensor for detecting a wheel speed in a predetermined sampling period and outputting time series data of the wheel speed as a wheel speed signal, a break point frequency estimating section for estimating a break point frequency in a gain diagram that represents a frequency response of a first order lag model that approximates a transmission characteristics from road surface disturbances to wheel speed, and a braking force gradient estimating section for estimating a braking force gradient with respect to the estimated break point frequency on the basis of the map showing a relationship between braking force gradient and break point frequency stored in advance.

Claims

1. A road surface state estimating device comprising:

a wheel speed sensor for detecting wheel speed and outputting a wheel speed signal;

a wheel speed frequency characteristic quantity estimating section for estimating, on the basis of the wheel speed signal, a wheel speed frequency characteristic quantity that represents a difference between a characteristic quantity in a low frequency region and a characteristic quantity in a high frequency region that is higher than the low frequency region in a gain diagram representing a frequency response of transmission characteristics from a road surface disturbance to the wheel speed; and

a physical quantity estimating section for estimating a physical quantity that represents a road state, from the estimated wheel speed frequency characteristic quantity.

2. A road surface state estimating device according to claim 1, wherein the physical quantity that represents the road state is a physical quantity that represents slipperiness between a tire and a road surface, including at least one of a braking force gradient, a driving force gradient and a road surface μ

gradient.

3. A road surface state estimating device according to claim 1, wherein the characteristic quantity is a vibration level of the wheel speed signal.

4. A road surface state estimating device according to claim 1, wherein the wheel speed frequency characteristic quantity estimating section, comprises:

a low frequency characteristic quantity calculating section for extracting a wheel speed signal in a low frequency range, the low frequency characteristic quantity calculating section comprising a first band-pass filter;

a first vibration level calculating section for calculating a vibration level from the wheel speed signal after filtering;

a high frequency characteristic quantity calculating section for extracting a wheel speed signal in a high frequency range, the high frequency characteristic quantity calculating section comprising a second band-pass filter;

a second vibration level calculating section for calculating a vibration level from the wheel speed signal after filtering; and

a characteristic quantity calculating section for outputting a difference between a low frequency characteristic quantity calculated by the low frequency characteristic quantity calculating section and a high frequency characteristic quantity calculating section, to serve as the wheel speed frequency characteristic quantity.

5. A road surface state estimating device comprising:

a wheel speed sensor for detecting a wheel speed and outputting a wheel speed signal;

a wheel speed frequency characteristic quantity estimating section for estimating, on the basis of the wheel speed signal, a wheel speed frequency characteristic quantity that represents, in a transmission characteristics, which is from a road surface disturbance to the wheel speed, approximated to a low order model, a frequency, at which gain changes from a value in a predetermined range to a value out of the predetermined range, in a gain diagram representing a frequency response of the approximated low order model; and

a physical quantity estimating section for estimating a physical quantity that represents a road state, from the estimated wheel speed frequency characteristic quantity.

6. A road surface state estimating device according to claim 5, wherein the low order model is a first order lag model.

7. A road surface state estimating device according to claim 5, wherein the physical quantity that represents the road state is a physical quantity that represents slipperiness between a tire and a road surface, including at least one of a braking force gradient, a driving force gradient and a road surface μ

gradient.

8. A road surface state estimating device comprising:

a wheel speed sensor for detecting wheel speed and outputting a wheel speed signal;

a wheel speed frequency characteristic quantity estimating section for estimating, on the basis of the wheel speed signal, a physical quantity as a wheel speed frequency characteristic quantity, for each of a plurality of frequency regions which are divided in a gain diagram representing a frequency response of transmission characteristics from a road surface disturbance to the wheel speed; and

a physical quantity estimating section for estimating a physical quantity that represents a road state, from the plurality of the estimated wheel speed frequency characteristic quantities.

9. A road surface state estimating device according to claim 8, wherein the physical quantity that represents the road state is a physical quantity that represents slipperiness between a tire and a road surface, including at least one of a braking force gradient, a driving force gradient and a road surface μ

gradient.

10. A road surface state estimating device according to claim 8, wherein the characteristic quantity is a vibration level of the wheel speed signal.

11. A road surface state estimating device according to claim 8, wherein the frequency regions include frequency bands of 10-20 Hz, 20-30 Hz, 30-40 Hz, 40-50 Hz, 50-60 Hz and 60-70 Hz.

12. A road surface state estimating device comprising:

a wheel speed sensor for detecting a wheel speed and outputting a wheel speed signal;

a wheel speed frequency characteristic quantity estimating section for estimating, on the basis of the wheel speed signal, a wheel speed frequency characteristic quantity which is based on each characteristic quantity of a respective plurality of frequency regions in a gain diagram representing a frequency response of transmission characteristics from a road surface disturbance to the wheel speed; and

a physical quantity estimating section for estimating a physical quantity that represents a road state, from the estimated wheel speed frequency characteristic quantity.

13. A road surface state estimating device according to claim 12, wherein the plural frequency regions include

a first frequency region that is a lower frequency region than a frequency region at which a tire rotation resonance is generated, and

a second frequency region that is a higher frequency region than the first frequency region.