Patent ID: 8244432
Filing Date: 2012-08-14
Classification: B60W

Abstract:
1. A road-surface friction-coefficient estimating device for a vehicle, for estimating a friction coefficient of a road surface on which the vehicle is traveling, comprising: a vehicle-speed detecting unit configured to detect a vehicle speed; a vehicle-wheel slip-angle detecting unit configured to detect a slip angle of a wheel; a restoring-speed setting unit configured to set a restoring speed at which a road-surface friction coefficient is to be restored to a preliminarily set value based on the vehicle speed and the slip angle of the wheel; and a road-surface friction-coefficient estimating unit configured to estimate the road-surface friction coefficient by allowing a previously estimated value of the road-surface friction coefficient to be restored to the set value at the restoring speed, wherein the road-surface friction-coefficient estimating unit includes: a presumptive rack-thrust-force estimating portion configured to estimate a presumptive rack thrust force presumably being generated in actuality; a reference rack-thrust-force estimating portion configured to estimate a reference rack thrust force expected to be generated; a tire-force estimating portion configured to estimate a tire force acting on the wheel; a friction-circle utilization-rate calculating portion configured to calculate a friction-circle utilization rate on the basis of the tire force; and a road-surface friction-coefficient estimating portion configured to set the friction-circle utilization rate as the road-surface friction coefficient when an absolute value of deviation between the presumptive rack thrust force and the reference rack thrust force is above a preliminarily set threshold value, and to estimate the road-surface friction coefficient by allowing a previously estimated value of the road-surface friction coefficient to be restored to the set value at the restoring speed when the absolute value of deviation is below the threshold value.