Brake Pad Prognosis System

• US 20080236269A1
• Filed: 02/25/2008
• Published: 10/02/2008
• Est. Priority Date: 03/27/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Howell, Mark N., Salman, Mutasim A., Chin, Yuen-Kwok, Riefe, Mark T., Amatyakul, Phanu, Yen, Chih-Hung, Whaite, John P.
• Granted Patent: US 7,694,555 B2
• Time in Patent Office: Days
• US Class Current: 73/121
• CPC Class Codes: B60T 17/221 Procedure or apparatus for checking or keeping in a correct functioning condition of brake systems hydraulic pressure systems in general F15B19/00, F15B21/04; testing structures or apparatus G01M
• CPC Class Codes: F16D 2066/006 without direct measurement of the quantity monitored, e.g. wear or temperature calculated form force and duration of braking

Abstract

A method for providing an estimate of brake pad thickness. The method employs fusion of sensors, if used, and driver brake modeling to predict the vehicle brake pad life. An algorithm is employed that uses various inputs, such as brake pad friction material properties, brake pad cooling rate, brake temperature, vehicle mass, road grade, weight distribution, brake pressure, brake energy, braking power, etc. to provide the estimation. The method calculates brake work using total work minus losses, such as aerodynamic drag resistance, engine braking and/or braking power as braking torque times velocity divided by rolling resistance to determine the brake rotor and lining temperature. The method then uses the brake temperature to determine the brake pad wear, where the wear is accumulated for each braking event. A brake pad sensor can be included to provide one or more indications of brake pad thickness from which the estimation can be revised.

Claims

1. A method for determining the thickness of a vehicle brake pad, said method comprising:

providing vehicle parameters;

using the vehicle parameters to determine brake work;

using the brake work to determine brake pad temperature;

using the brake pad temperature to determine brake pad wear; and

accumulating the brake pad wear to provide an estimation of the brake pad thickness.

2. The method according to claim 1 wherein providing vehicle parameters includes providing brake pad friction material, brake pad cooling rate, vehicle mass, road grade, dynamic brake proportioning, vehicle weight distribution, vehicle speed, wheel speed and brake pressure.

3. The method according to claim 2 wherein providing vehicle parameters includes providing vehicle odometer reading, GPS location, map location and ambient temperature.

4. The method according to claim 1 wherein determining the brake work includes subtracting resistance values from total work.

5. The method according to claim 4 wherein determining the brake work includes using the equation:

6. The method according to claim 1 wherein determining the brake work includes determining braking force as brake pressure times brake pad area times brake pad coefficient of friction.

7. The method according to claim 1 wherein determining the brake work includes determining braking power as torque times velocity divided by the rolling radius of a vehicle wheel.

8. The method according to claim 1 wherein using the brake work to determine brake pad temperature and using the brake pad temperature to determine brake wear includes using look-up tables.

9. The method according to claim 1 further comprising providing a brake pad sensor that determines the thickness of the brake pad at one or more brake pad thickness levels.

10. The method according to claim 9 further comprising ramping out a difference between the estimated brake pad thickness and the actual brake pad thickness over the remaining thickness of the brake pad.

11. The method according to claim 9 wherein the sensor provides more than one indication of brake pad thickness.

12. The method according to claim 1 further comprising notifying a vehicle operator of the brake pad thickness estimation using telematics.

13. A method for determining the thickness of a vehicle brake pad, said method comprising:

providing vehicle parameters including brake pad friction material, brake pad cooling rate, vehicle mass, road grade, dynamic brake proportioning, vehicle weight distribution, vehicle speed, wheel speed and brake pressure;

using the vehicle parameters to determine brake work, wherein the brake work is determined in at least two ways including determining brake work based on braking energy and determining brake work based on braking power;

using the brake work to determine brake pad temperature;

using the brake pad temperature to determine brake pad wear;

accumulating the brake pad wear to provide an estimation of the brake pad thickness;

providing a brake pad sensor that determines the thickness of the brake pad at one or more brake pad thickness levels; and

ramping out a difference between the estimated brake pad thickness and the actual brake pad thickness over the remaining thickness of the brake pad.

14. The method according to claim 13 wherein providing vehicle parameters further includes providing vehicle odometer reading, GPS location, map location and ambient temperature.

15. The method according to claim 13 wherein determining the brake work includes subtracting resistance values from total work.

16. The method according to claim 13 wherein determining the brake work includes determining braking force as brake pressure times brake pad area times brake pad coefficient of friction.

17. The method according to claim 13 wherein determining the brake work includes determining braking power as torque times velocity divided by the rolling radius of a vehicle wheel.

18. The method according to claim 13 wherein using the brake work to determine brake pad temperature and using the brake pad temperature to determine brake wear includes using look-up tables.

19. The method according to claim 13 wherein the sensor provides more than one indication of brake pad thickness.

20. The method according to claim 13 further comprising notifying a vehicle operator of the brake pad thickness estimation using telematics.