Road-Surface Condition Estimating Device

• US 20080319626A1
• Filed: 06/12/2008
• Published: 12/25/2008
• Est. Priority Date: 06/21/2007
• Status: Active Grant

• Current Assignee: Subaru Corp.
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Ogawa, Hiroshi
• Granted Patent: US 9,037,376 B2
• Time in Patent Office: Days
• 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

A front-wheel speed is calculated as a wheel speed of driving wheels, a rear-wheel speed is calculated as a wheel speed of driven wheels, a rear-wheel acceleration is calculated as a wheel acceleration of the driven wheels, a front-wheel-speed difference value is calculated as a driving-wheel-speed difference value, a rear-wheel-speed difference value is calculated as a driven-wheel-speed difference value, a rear-wheel-acceleration difference value is calculated as a driven-wheel-acceleration difference value, and a front-wheel ground load is calculated as a ground load acting on the driving wheels. Based on these calculated values, a gradient of a tire-characteristic curve indicating an amount of change in road-surface friction coefficient with respect to an amount of change in slip rate is calculated, and the calculated gradient of the tire-characteristic curve is compared with preset threshold values, whereby a road-surface friction coefficient as a road-surface condition can be determined.

Claims

1. A road-surface condition estimating device comprising:

driving-wheel-speed detecting means that detects a speed of a driving wheel;

driven-wheel-speed detecting means that detects a speed of a driven wheel;

driven-wheel-acceleration detecting means that detects an acceleration of the driven wheel;

driving-wheel-speed difference calculating means that calculates a difference between a currently detected driving wheel speed and a previously detected driving wheel speed as a driving-wheel-speed difference

driven-wheel-speed difference calculating means that calculates a difference between a currently detected driven wheel speed and a previously detected driven wheel speed as a driven-wheel-speed difference ;

acceleration difference calculating means that calculates a difference between a currently detected driven-wheel acceleration and a previously detected driven-wheel acceleration as a driven-wheel-acceleration difference;

ground-load calculating means that calculates a ground load acting on the driving wheel;

characteristic calculating means that calculates an amount of change in a road-surface friction coefficient with respect to an amount of change in a slip rate in a characteristic curve that indicates a relationship between the road-surface friction coefficient and the slip rate, the calculation being performed on the basis of the driving wheel speed, the driven wheel speed, the driving-wheel-speed difference value, the driven-wheel-speed difference value, the driven-wheel-acceleration difference, and the ground load; and

road-surface-condition determining means that determines a road-surface condition on the basis of the amount of change in the road-surface friction coefficient.

2. The road-surface condition estimating device according to claim 1, wherein the characteristic calculating means calculates the amount of change in the road-surface friction coefficient on the basis of a value divided a difference of a driving force by a product of the amount of change in the slip rate and the driving-wheel ground load.

3. The road-surface condition estimating device according to claims 1, wherein the road-surface-condition determining means compares a preset threshold value with the amount of change in the road-surface friction coefficient so as to estimate a road-surface friction coefficient.

4. The road-surface condition estimating device according to claims 2, wherein the road-surface-condition determining means compares a preset threshold value with the amount of change in the road-surface friction coefficient so as to estimate a road-surface friction coefficient.