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

• US 20050010350A1
• Filed: 07/06/2004
• Published: 01/13/2005
• Est. Priority Date: 07/07/2003
• Status: Active Grant

• Current Assignee: Subaru Corp.
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Hiwatashi, Yutaka
• Granted Patent: US 7,702,446 B2
• Time in Patent Office: Days
• 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 based on 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 setting as an initial value the road-surface friction coefficient thus specified, resetting the present value of the road-surface friction coefficient to the initial value and then starting estimation of the road-surface friction coefficient with the initial value as a standard.

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, 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.

7. The road-surface friction coefficient estimating device as claimed in claim 6, 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.

8. A road-surface friction coefficient estimating method for estimating a road-surface friction coefficient by updating the road-surface friction coefficient with time lapse based on an estimated present value of the road-surface friction coefficient, comprising:

a first step of 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

a second step of setting as an initial value the road-surface friction coefficient thus specified, resetting the present value of the road-surface friction coefficient to the initial value and then starting estimation of the road-surface friction coefficient with the initial value as a standard.

9. The road-surface friction coefficient estimating method as claimed in claim 8, wherein the first step includes a step of specifying 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.