Anti-lock brake control method having adaptive initial brake pressure reduction
AssigneeGeneral Motors Corporation
InventorsAllen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
Life of this patent
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Abstract
An improved anti-lock brake control method in which the brake pressure reduction initiated upon detection of insipient wheel lock is adaptively determined based on a periodically updated characterization of the relationship between brake pedal position and vehicle deceleration. The brake torque and vehicle weight are estimated based on the characterization data, corrected for variation in brake heating, and used to compute the surface coefficient of friction, which in turn, is used to schedule the initial anti-lock brake pressure reduction for optimal braking system performance.
Claims9
A method of operation for a vehicle anti-lock braking system including a driver activated brake pedal and a modulator controlled to initially reduce a braking pressure by a determined initial pressure reduction amount upon detection of an insipient wheel lock condition, the method comprising the steps of:
- periodically measuring vehicle deceleration and a brake pedal position during activation of the braking system;
- constructing and periodically updating a brake system characterization table representing a relationship between the measured vehicle deceleration and measured brake pedal position;
- estimating a road surface coefficient of friction based on the characterization table and changes in the characterization table due to the periodic updating;
- revising said initial pressure reduction amount based on the estimated road surface coefficient of friction upon detection of the insipient wheel lock condition;
- periodically determining a brake temperature;
- and
- compensating the estimated road surface coefficient of friction for variations in the determined brake temperature.
A method of operation for a vehicle anti-lock braking system including a driver activated brake pedal and a modulator controlled to initially reduce a braking pressure by a determined initial pressure reduction amount upon detection of an insipient wheel lock condition, the method comprising the steps of:
- periodically measuring vehicle deceleration and a brake pedal position during activation of the braking system;
- constructing and periodically updating a brake system characterization table representing a relationship between the measured vehicle deceleration and measured brake pedal position;
- estimating a road surface coefficient of friction based on the characterization table and changes in the characterization table due to the periodic updating;
- revising said initial pressure reduction amount based on the estimated road surface coefficient of friction upon detection of the insipient wheel lock condition;
- wherein the step of estimating the road surface coefficient of friction includes the steps of:
- estimating a braking torque during activation of the braking system based on said characterization table and the measured brake pedal position;
- periodically updating a vehicle weight estimate based on said changes in the characterization table;
- and
- estimating the road surface coefficient of friction based on the estimated braking torque and the vehicle weight estimate.
Dependencies are inferred from the claim text.