Method and circuit configuration for determining a frictional value
First Claim
1. A method for determined a frictional value between a motor vehicle tire and a road surface, which comprises:
- ascertaining values of vehicle speed, angular acceleration of a vehicle wheel, and brake pressure;
calculating a wheel slip from the values;
approximating a dependency of a coefficient of friction between a road surface and a vehicle tire from the wheel slip with a non-linear approximately equation;
estimating a current estimation value for the coefficient of friction with a recursive estimation algorithm from measurement values previously ascertained during a preceding measuring instant; and
determining a frictional value between the motor vehicle tire and the road surface from the coefficient of friction estimated with the recursive estimation algorithm.
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Accused Products
Abstract
A frictional value between a motor vehicle tire and a road surface is determined for use in an ABS system or a traction control system. Various sensors at the automobile ascertain the vehicle speed and the brake pressure at individual wheels. The angular acceleration of the wheel is calculated from the angular velocity thereof. A wheel slip is calculated from the vehicle speed and from the angular acceleration. The dependency of the coefficient of friction is approximated from the wheel slip with a non-linear approximation equation. The current estimation value for the coefficient of friction is estimated with a recursive estimation algorithm from measurement values previously ascertained during a preceding measuring instant.
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Citations
12 Claims
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1. A method for determined a frictional value between a motor vehicle tire and a road surface, which comprises:
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ascertaining values of vehicle speed, angular acceleration of a vehicle wheel, and brake pressure; calculating a wheel slip from the values; approximating a dependency of a coefficient of friction between a road surface and a vehicle tire from the wheel slip with a non-linear approximately equation; estimating a current estimation value for the coefficient of friction with a recursive estimation algorithm from measurement values previously ascertained during a preceding measuring instant; and determining a frictional value between the motor vehicle tire and the road surface from the coefficient of friction estimated with the recursive estimation algorithm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A circuit configuration for determining a coefficient of friction between a motor vehicle tire and a road surface, comprising:
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a plurality of sensors disposed at a motor vehicle for continuously measuring an angular speed of a wheel and a braking pressure at a wheel; an evaluation circuit connected to said sensors and receiving the signals from the sensors, said evaluation circuit being programmed to calculate and angular acceleration from the angular speed measured by a respective one of said sensors; and to evaluate a coefficient of friction between a motor vehicle tire and a road surface from the angular acceleration and from the braking pressure with a recursive estimation algorithm. - View Dependent Claims (10, 11)
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12. In an anti-lock brake system or a traction control system in which a coefficient of friction between a motor vehicle tire and a road surface is utilized as a control parameter, an improved circuit configuration for determining the coefficient of friction between the motor vehicle tire and the road surface, the improvement which comprises:
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a plurality of sensors disposed at the motor vehicle for continuously measuring a vehicle travel speed, an angular speed of a wheel, and a braking pressure at a wheel; an evaluation circuit connected to said sensor and receiving the signals from said sensors, the evaluation circuit being programmed for calculating an angular acceleration from the angular speed measured by a respective one of said sensors; for calculating a wheel slip from the vehicle travel speed and from the angular acceleration; for approximately a dependency of the coefficient of friction between the tire and the road surface from the wheel slip with a non-linear approximation equation; and for determining a current estimated value of the coefficient of friction between the motor vehicle tire and the road surface from measurement values ascertained in an immediately preceding instant with a recursive estimation algorithm.
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Specification