Road-surface condition estimating device

• US 20080319683A1
• Filed: 06/24/2008
• Published: 12/25/2008
• Est. Priority Date: 06/25/2007
• Status: Active Grant

• Current Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Ogawa, Hiroshi
• Granted Patent: US 7,620,504 B2
• Time in Patent Office: Days
• US Class Current: 702/41
• CPC Class Codes: B60G 2400/822 Road friction coefficient determination affecting wheel traction
• CPC Class Codes: B60G 2800/014 Pitch; Nose dive
• CPC Class Codes: B60G 2800/0192 longitudinal with regard to vehicle
• CPC Class Codes: B60G 2800/21 Traction, slip, skid or slide control
• 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 2040/1307 Load distribution on each wheel suspension
• CPC Class Codes: B60W 2510/0657 Engine torque
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 40/068 Road friction coefficient

Abstract

A driving-torque difference value, an inertial-force difference value of the vehicle, and an inertial-force change-amount difference value of the vehicle are calculated. Subsequently, a first determination coefficient by which the inertial-force difference value is to be multiplied or a second determination coefficient by which the driving-torque difference value is to be multiplied is estimated on the basis of a state equation having the inertial-force difference value as a state variable and the driving-torque difference value as an input variable. Subsequently, a road-surface condition is determined on the basis of a comparison between a threshold value and the first determination coefficient or the second determination coefficient.

Claims

1. A road-surface condition estimating device, comprising:

driving-torque detecting means that detects a driving torque of an engine;

longitudinal-acceleration detecting means that detects a longitudinal acceleration of the vehicle;

driving-torque difference-value calculating means that calculates a difference between a currently detected driving torque of the engine and a previously detected driving torque of the engine as a driving-torque difference value;

inertial-force difference-value calculating means that calculates a difference between a current inertial force of the vehicle and a previous inertial force of the vehicle as an inertial-force difference value on the basis of the longitudinal acceleration;

inertial-force change-amount difference-value calculating means that calculates a difference between a current amount of change in inertial force of the vehicle and a previous amount of change in inertial force of the vehicle as an inertial-force change-amount difference value on the basis of the longitudinal acceleration;

determination-coefficient calculating means that calculates at least one of a first determination coefficient and a second determination coefficient on the basis of a state equation related to the inertial-force change-amount difference value, the state equation being formed by adding a first arithmetic term to a second arithmetic term, the first arithmetic term being obtained by multiplying the inertial-force difference value by the first determination coefficient, the second arithmetic term being obtained by multiplying the driving-torque difference value by the second determination coefficient; and

road-surface-condition determining means that determines a road-surface condition on the basis of the at least one of the first determination coefficient and the second determination coefficient.

3. The road-surface condition estimating device according to claims 1, wherein the road-surface-condition determining means determines the road-surface condition on the basis of the at least one of the determination coefficients by comparing the at least one of the determination coefficients with a determination threshold value that is preliminarily adjustably set in accordance with a vehicle speed.

2. A road-surface condition estimating device, comprising:

driving-torque detecting means that detects a driving torque of an engine;

longitudinal-acceleration detecting means that detects a longitudinal acceleration of the vehicle;

driving-torque difference-value calculating means that calculates a difference between a currently detected driving torque of the engine and a previously detected driving torque of the engine as a driving-torque difference value;

inertial-force difference-value calculating means that calculates a difference between a current inertial force of the vehicle and a previous inertial force of the vehicle as an inertial-force difference value on the basis of the longitudinal acceleration;

determination-coefficient calculating means that calculates at least one of a third determination coefficient and a fourth determination coefficient on the basis of a pulse transfer function related to the inertial-force difference value, the pulse transfer function being formed by adding a first arithmetic term to a second arithmetic term, the first arithmetic term being obtained by multiplying the inertial-force difference value by the third determination coefficient, the second arithmetic term being obtained by multiplying the driving-torque difference value by the fourth determination coefficient; and

road-surface-condition determining means that determines a road-surface condition on the basis of the at least one of the third determination coefficient and the fourth determination coefficient.

4. The road-surface condition estimating device according to claims 2, wherein the road-surface-condition determining means determines the road-surface condition on the basis of the at least one of the determination coefficients by comparing the at least one of the determination coefficients with a determination threshold value that is preliminarily adjustably set in accordance with a vehicle speed.