Brake system control method responsive to measured vehicle acceleration

• US 6,125,319 A
• Filed: 08/17/1998
• Issued: 09/26/2000
• Est. Priority Date: 08/17/1998
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Busshardt, Joachim, Majeed, Kamal Naif, Hac, Aleksander Boguslaw, Chen, Hsien Heng, Hoying, John Francis
• Primary Examiner(s): Zanelli, Michael J.
• Application Number:
  US09/134,951
• Time in Patent Office: 771 Days
• Field of Search: 701/72, 701/79, 701/80, 701/83, 303/146, 303/150, 303/155, 303/189, 303/192
• US Class Current: 701/80
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 8/17636 Microprocessor-based systems

Abstract

A brake system control method, comprising the steps of: determining a maximum acceleration of a vehicle on a high coefficient of adhesion road surface; measuring an acceleration of the vehicle; determining a ratio between the measured acceleration of the vehicle and the maximum acceleration of the vehicle on the high coefficient of adhesion road surface; responsive to the ratio, determining a signal indicative of present coefficient of adhesion; determining a brake actuator command responsive to the signal; and providing the brake actuator command to a brake actuator, wherein an accurate estimation of coefficient of friction between the vehicle wheels and the road surface is used in the brake system control.

Claims

1. A brake system control method, comprising the steps of:

determining a maximum acceleration of a vehicle on a high coefficient of adhesion road surface;

measuring an acceleration of the vehicle;

determining a ratio between the measured acceleration of the vehicle and the maximum acceleration of the vehicle on the high coefficient of adhesion road surface;

responsive to the ratio, determining a signal indicative of present coefficient of adhesion;

determining a brake actuator command responsive to the signal; and

providing the brake actuator command to a brake actuator.

2. A brake system control method according to claim 1, wherein the maximum acceleration and the measured acceleration are in a lateral direction of the vehicle, wherein the signal is indicative of the present coefficient of adhesion in the lateral direction.

3. A brake system control method according to claim 1, also comprising the steps of:

monitoring a plurality of vehicle conditions;

responsive to the plurality of conditions, determining whether the vehicle is in a non-linear mode of operation; and

updating the signal indicative of present coefficient of adhesion only when the vehicle is in the non-linear mode of operation.

4. A brake system control method according to claim 1, wherein the plurality of vehicle conditions include desired lateral acceleration, measured yaw rate and desired yaw rate.

5. A brake system control method according to claim 3, also comprising the steps of:

responsive to the plurality of conditions, determining a desired vehicle lateral acceleration, wherein

the signal is updated only when the desired vehicle lateral acceleration has a same lateral direction as the measured acceleration.

6. A brake system control method according to claim 5, wherein the signal is updated also only when the desired vehicle lateral acceleration is larger than the measured acceleration by a predetermined threshold.

8. A brake system control method according to claim 1, also comprising the steps of:

monitoring a plurality of vehicle conditions;

responsive to the plurality of conditions, determining a desired vehicle lateral acceleration, wherein

the signal is updated only when the desired vehicle lateral acceleration is larger than the measured acceleration of the vehicle by a sufficient margin.

9. A brake system control method according to claim 1, also comprising the steps of:

monitoring a plurality of vehicle conditions;

responsive to the plurality of conditions, determining a desired vehicle lateral acceleration, wherein

the signal is updated only when the desired vehicle lateral acceleration has a same lateral direction as the measured acceleration.

7. A brake system control method, comprising the steps of:

setting a signal representing a surface coefficient of adhesion between vehicle wheels and a road surface equal to a default value;

monitoring a set of vehicle conditions;

responsive to the set of vehicle conditions, determining whether the vehicle is in a non-linear mode of operation;

if the vehicle is in a non-linear mode of operation, reducing the signal to a value determined responsive to a measured vehicle lateral acceleration and a maximum lateral acceleration for the vehicle on a high coefficient of adhesion road surface;

responsive to the value, determining a control command; and

applying the control command to a brake system actuator.