System for estimating vehicle body speed and road surface friction coefficient
First Claim
1. A system for estimating a vehicle operating variable of a vehicle provided with a set of road wheels, the system comprising:
- a sensor group for sensing vehicle operating conditions of the vehicle to determine values of wheel speed, wheel load and wheel longitudinal force of each wheel of at least two of the road wheels; and
an estimating unit for determining a relationship among the wheel speed, wheel load and wheel longitudinal force in accordance with the values of the wheel speed, load and longitudinal force and for estimating the vehicle operating variable from the relationship, the vehicle operating variable being one of a body speed and a road surface friction coefficient;
wherein the estimating unit is configured to determine a value of a per-unit-load longitudinal force by dividing the value of the wheel longitudinal force by the value of the wheel load for each wheel, to form a data pair of the values of the per-unit-load longitudinal force and wheel speed of each of said at least two of the road wheels, to identify a regression line from a plurality of the data pairs, and to estimate the vehicle operating variable from the regression line.
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Accused Products
Abstract
A system for a wheeled vehicle includes sensors for determining wheel speed, wheel load and wheel longitudinal driving or braking force of each wheel, and an estimating or controlling unit for estimating a vehicle body speed and/or a road surface friction coefficient from sensor output signals. The estimating unit determines a coordinate pair of a wheel speed value and a longitudinal force coefficient value for each wheel, and plots the coordinate pairs of the individual wheels as a set of points in a plane rectangular coordinate axis. The unit determines a regression line closely fit to the point set and obtains the estimates of the vehicle body speed and friction coefficient from the intercept of the regression line on the coordinate axis of the wheel speed and the slope of the regression line.
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Citations
23 Claims
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1. A system for estimating a vehicle operating variable of a vehicle provided with a set of road wheels, the system comprising:
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a sensor group for sensing vehicle operating conditions of the vehicle to determine values of wheel speed, wheel load and wheel longitudinal force of each wheel of at least two of the road wheels; and an estimating unit for determining a relationship among the wheel speed, wheel load and wheel longitudinal force in accordance with the values of the wheel speed, load and longitudinal force and for estimating the vehicle operating variable from the relationship, the vehicle operating variable being one of a body speed and a road surface friction coefficient; wherein the estimating unit is configured to determine a value of a per-unit-load longitudinal force by dividing the value of the wheel longitudinal force by the value of the wheel load for each wheel, to form a data pair of the values of the per-unit-load longitudinal force and wheel speed of each of said at least two of the road wheels, to identify a regression line from a plurality of the data pairs, and to estimate the vehicle operating variable from the regression line. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A system for estimating a vehicle operating variable of a vehicle, the system comprising:
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a sensor group for sensing vehicle operating conditions to determine values of a wheel speed, a wheel load and a wheel longitudinal force of each of wheels of the vehicle; and an estimating unit for determining a value of a per-unit-load longitudinal force of each of the wheels, for forming a data pair of the values of the wheel speed and the per-unit-load longitudinal force of each of the wheels, for identifying a regression line from at least two of the data pairs, and for estimating the vehicle operating variable from the regression line, the vehicle operating variable being one of a vehicle body speed and a road surface friction coefficient, the per-unit-load longitudinal force being determined in accordance with a quotient obtained by dividing the wheel longitudinal force by the wheel load.
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23. A process for estimating a vehicle operating variable of a vehicle provided with a set of wheels, comprising:
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a preparing step of determining values of wheel speed, wheel load and wheel longitudinal force of each wheel; an estimating step of estimating the vehicle operating variable by analyzing the values of the wheel speed, load and longitudinal force, the vehicle operating variable being one of a vehicle body speed and a road surface friction coefficient; wherein the estimating step comprises a step of assigning each wheel uniquely a coordinate pair of a value of a first variable and a value of a second variable, determining a functional relationship between the first and second variables in accordance with a plurality of the coordinate pairs of the wheels, determining a value of the first variable corresponding to a zero value of the second variable according to the relationship and a rate of increase of the second variable with respect to the first variable according to the relationship, and estimating the vehicle body speed from the value of the first variable corresponding to the zero value of the second variable, and the friction coefficient from the rate of increase of the second variable with respect to the first variable, the first variable being indicative of the wheel speed, the second variable being indicative of a ratio of the wheel longitudinal force to the wheel load; wherein the preparing step comprises, a wheel longitudinal force determining step of determining a calculated driving torque value and a calculated braking torque value of each wheel and determining a calculated longitudinal force value by subtraction between the calculated driving torque value and braking torque value for each wheel, and a per-unit-load longitudinal force determining step of determining a calculated per-unit-load longitudinal force value by dividing the longitudinal force value by the wheel load value of each wheel, the value of the second variable being determined from the per-unit-load longitudinal force value for each wheel; and wherein the process further comprises a selecting step of determining a wheel slip rate of each wheel and disregarding the coordinate pair of each wheel in determining the relationship if the wheel slip rate is in a predetermined range.
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Specification