Road-surface friction coefficient estimating device and road-surface friction coefficient estimating method

• US 7,702,446 B2
• Filed: 07/06/2004
• Issued: 04/20/2010
• Est. Priority Date: 07/07/2003
• Status: Expired due to Fees

• Current Assignee: Subaru Corp.
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Hiwatashi, Yutaka
• Primary Examiner(s): Black; Thomas G
• Assistant Examiner(s): LOUIE, WAE LENNY
• Application Number:
  US10/883,686
• Publication Number:
  US 20050010350A1
• Time in Patent Office: 2,114 Days
• Field of Search: 701/73, 701/80, 701/70, 340/140, 340/150, 340/149, 73/9, 731/46, 73/10, 731/05
• US Class Current: 701/80
• CPC Class Codes: B60G 2400/822 Road friction coefficient determination affecting wheel traction
• CPC Class Codes: B60G 2800/702 Improving accuracy of a sensor signal
• 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: B60W 10/14 Central differentials for dividing torque between front and rear axles
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 2552/40 Coefficient of friction
• CPC Class Codes: B60W 40/064 Degree of grip
• CPC Class Codes: B60W 40/068 Road friction coefficient
• CPC Class Codes: G08G 1/096716 where the received information does not generate an automatic action on the vehicle control
• CPC Class Codes: G08G 1/096758 where no selection takes place on the transmitted or the received information
• CPC Class Codes: G08G 1/096783 where the origin of the information is a roadside individual element

Abstract

A road surface μ is updated with time on the basis of a present value (an estimation value E) of the road surface μ estimated to estimate the road surface μ. In this case, if there is acquired road-surface information in a vehicle travel direction that is detected by a road-side infrastructure, a specifying unit 11 specifies a road-surface friction coefficient based on the road-surface information. An estimating unit 12 sets the road surface μ (μinf) thus specified as an initial value, resets the present value of the road surface μ to the initial value, and then starts estimation of the road-surface friction coefficient based on this initial value. Accordingly, estimation precision of a road-surface friction coefficient is enhanced by using an initial value having high reliability in autonomous estimation of the road-surface friction coefficient.

Claims

1. A road-surface friction coefficient estimating device for estimating a road-surface friction coefficient by updating the road-surface friction coefficient with time lapse by using an estimated present value of the road-surface friction coefficient as a standard for a next estimation of the road-surface friction coefficient, comprising:

a specifying unit for specifying the road-surface friction coefficient based on road-surface information detected by a road-side infrastructure in a traveling direction of a vehicle when the road-surface information is acquired; and

an estimating unit for setting the specified road-surface friction coefficient as an initial value, resetting the estimated present value of the road-surface friction coefficient to the initial value and then starting next estimation of the road-surface friction coefficient with the initial value as a standard for a next estimation of the road-surface friction coefficient,

wherein the specifying unit previously stores plural road-surface friction coefficients corresponding to plural pieces of road-surface information, and

wherein the specifying unit specifies the road-surface friction coefficient corresponding to the acquired road-surface information from the plural road-surface friction coefficients associated with the plural pieces of road-surface information.

2. The road-surface friction coefficient estimating device as claimed in claim 1, further comprising:

an acquiring device for acquiring service information that includes the road-surface information from the road-side infrastructure; and

a computer for outputting the road-surface information to the specifying unit in synchronization with an arrival timing at which the vehicle arrives at a point corresponding to the road-surface information specified by the acquired service information.

3. The road-surface friction coefficient estimating device as claimed in claim 1, wherein the estimating unit estimates cornering power based on a dynamic equation of the vehicle by using a vehicle speed, a steering angle and a yaw rate, and estimating the present value of the road-surface friction coefficient based on cornering power of front and rear wheels regarding a predetermined road-surface friction coefficient and the cornering power of the front and rear wheels thus estimated.

4. The road-surface friction coefficient estimating device as claimed in claim 3, wherein the specifying unit specifies the road-surface friction coefficient corresponding to the acquired road-surface information from plural road-surface friction coefficients associated with plural pieces of road-surface information.

5. The road-surface friction coefficient estimating device as claimed in claim 3, further comprising:

an acquiring device for acquiring service information that includes the road-surface information from the road-side infrastructure; and

a computer for outputting the road-surface information to the specifying unit in synchronization with an arrival timing at which the vehicle arrives at a point corresponding to the road-surface information specified by the acquired service information.

6. The road-surface friction coefficient estimating device as claimed in claim 1, further comprising:

an acquiring device for acquiring service information that includes the road-surface information from the road-side infrastructure; and

a computer for outputting the road-surface information to the specifying unit in synchronization with an arrival timing at which the vehicle arrives at a point corresponding to the road-surface information specified by the acquired service information.

7. The road-surface friction coefficient estimating device as claimed in claim 1, wherein said road-surface friction coefficient is estimated based on a vehicle speed, a steering angle, and a yaw rate.

8. The road-surface friction coefficient estimating device as claimed in claim 1, wherein the road surface information comprises information related to at least one of a dry condition, a wet condition, a water film condition, a snow condition, and an ice condition.

9. The road-surface friction coefficient estimating device as claimed in claim 1, wherein the estimating unit gives the initial value with interruption.

10. The road-surface friction coefficient estimating device as claimed in claim 1, wherein said estimating unit receives said road-surface information from the road-side infrastructure and detections signals from at least one on-vehicle sensor.

11. The road-surface friction coefficient estimating device as claimed in claim 10, wherein said at least one on-vehicle sensor detects a vehicle speed, a steering angle, and a yaw rate.

12. The road-surface friction coefficient estimating device as claimed in claim 10, wherein said estimating unit receives actuating signals from at least one of a traction controlling unit, an anti-lock brake controlling unit, a brake-force controlling unit, a skid detecting unit, and a transmission controlling unit.

13. The road-surface friction coefficient estimating device as claimed in claim 12, wherein the transmission controlling unit inputs a signal indicating a selected one of a plurality of travel patterns, the plurality of travel patterns including a normal pattern and a pattern having a broader travel area than the normal pattern under a low gear.

14. The road-surface friction coefficient estimating device as claimed in claim 1, wherein said road-surface friction coefficient is estimated based on cornering powers of wheels of the vehicle.

15. A road-surface friction coefficient estimating method for estimating a road-surface friction coefficient by updating the road-surface friction coefficient with time lapse by using an estimated present value of the road-surface friction coefficient as a standard for a next estimation of the road-surface friction coefficient, comprising:

specifying the road-surface friction coefficient based on road-surface information detected by a road-side infrastructure in a traveling direction of a vehicle when the road-surface information is acquired; and

setting the specified road-surface friction coefficient as an initial value, resetting the estimated present value of the road-surface friction coefficient to the initial value and then starting next estimation of the road-surface friction coefficient with the initial value as a standard for a next estimation of the road-surface friction coefficient,

wherein plural road-surface friction coefficients corresponding to plural pieces of road-surface information are previously stored, and

wherein the road-surface friction coefficient is specified corresponding to the acquired road-surface information from the plural road-surface friction coefficients associated with the plural pieces of road-surface information.

16. The method according to claim 15, wherein said setting is performed with interruption.

17. A road-surface friction coefficient estimating method, comprising:

setting a specified road-surface friction coefficient as an initial value of the road-surface friction coefficient;

resetting a present value of the road-surface friction coefficient to the initial value; and

estimating the road-surface friction coefficient with the initial value as a standard for a next estimation of the road-surface friction coefficient.

18. The method according to claim 17, wherein said setting is performed with interruption.

19. A road-surface friction coefficient estimating device for estimating a road-surface friction coefficient by updating the road-surface friction coefficient with a time lapse by using an estimated present value of the road-surface friction coefficient, comprising:

a specifying unit for specifying the road-surface friction coefficient based on road-surface information detected by a road-side infrastructure in a traveling direction of a vehicle when the road-surface information is acquired; and

an estimating unit for estimating a present value of the road-surface friction coefficient based on an estimated previous value of the road-surface friction coefficient when the road-surface information is not acquired, and for estimating the present value of the road-surface friction coefficient as a specified road-surface friction coefficient when the road-surface information is acquired.