System for estimating the road surface friction
First Claim
1. A road friction estimating system, comprisinga yaw rate sensor for detecting an actual yaw rate of a vehicle;
- standard yaw rate computing means for computing a standard yaw rate according to a yaw rate response model of said vehicle and vehicle operating data including a steering wheel steering angle and a vehicle speed assuming that said vehicle is equipped with standard tires and traveling over a standard road surface, said yaw rate model being expressed by a transfer function including a variation term;
identification means which determines a parameter of said variation term of said transfer function according to a deviation of said actual yaw rate detected by said yaw rate sensor from said standard yaw rate computed by said standard yaw rate; and
converting means for converting said parameter determined by said identification means into a value representing a frictional property between a road surface and said tires.
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Abstract
The road friction is determined from the deviation of the estimated yaw rate under a standard condition from the actually measured yaw rate. The system for determining the road friction includes a parameter identification unit which determines a parameter of a variation term defined in the transfer function of the model for the vehicle response. The variation term may consist of a zero-th order or a first-order transfer function which would not cause any large computation load, and may not depend on the vehicle speed. The determined road friction may be used for controlling the rear wheel steering angle of a four wheel steering vehicle.
27 Citations
9 Claims
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1. A road friction estimating system, comprising
a yaw rate sensor for detecting an actual yaw rate of a vehicle; -
standard yaw rate computing means for computing a standard yaw rate according to a yaw rate response model of said vehicle and vehicle operating data including a steering wheel steering angle and a vehicle speed assuming that said vehicle is equipped with standard tires and traveling over a standard road surface, said yaw rate model being expressed by a transfer function including a variation term; identification means which determines a parameter of said variation term of said transfer function according to a deviation of said actual yaw rate detected by said yaw rate sensor from said standard yaw rate computed by said standard yaw rate; and converting means for converting said parameter determined by said identification means into a value representing a frictional property between a road surface and said tires. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification