System And Method For Correcting Brake Knockback In A Vehicle

• US 20090326776A1
• Filed: 06/30/2008
• Published: 12/31/2009
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: Weber, Steven J., Tomlinson, Charles M.
• Granted Patent: US 8,812,212 B2
• Time in Patent Office: Days
• US Class Current: 701/72
• CPC Class Codes: B60T 13/662 characterised by specified functions of the control system components
• 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

Abstract

A system and method for correcting brake knockback in a vehicle disk brake system. Brake knockback can occur when a vehicle is driven through an aggressive turn or in other environments that exert a significant amount of lateral force on the vehicle'"'"'s wheels. This can cause the rotors to deflect and push brake pistons into retracted positions, where they remain even after the vehicle exits the turn. According to one embodiment, the present method first estimates or predicts brake knockback by using lateral acceleration readings from the vehicle and a brake knockback model, and then corrects brake knockback by generating command signals for a hydraulic pump.

Claims

1. A system for correcting brake knockback in a vehicle, comprising:

a sensor having an output that provides a lateral acceleration signal, and the lateral acceleration signal includes information regarding a lateral acceleration of the vehicle;

an electronic module having an input coupled to the sensor output, an electronic processing device, and an output that provides a command signal; and

a hydraulic pump for pressurizing hydraulic fluid in a vehicle disk brake system according to the command signal, wherein the electronic module uses the lateral acceleration signal to predict brake knockback and uses the command signal to correct brake knockback.

2. The system of claim 1, wherein the electronic module uses a first-order low-pass filter to process the lateral acceleration signal.

3. The system of claim 1, wherein the electronic module includes an additional input that is coupled to at least one of the sensors selected from the group consisting of:

a wheel speed sensor, an accelerator pedal sensor, and a brake pedal sensor.

4. The system of claim 1, wherein the electronic module is an electronic brake control module (EBCM).

5. The system of claim 1, wherein the electronic module further includes a memory device with a brake knockback model stored thereon, and the electronic module uses the lateral acceleration signal and the brake knockback model to predict brake knockback.

6. The system of claim 5, wherein the brake knockback model is based on a lateral acceleration reference value that was obtained during a previous braking event.

7. The system of claim 5, wherein the brake knockback model includes a flat segment, a first sloped segment, and a second sloped segment.

8. A method for correcting brake knockback in a vehicle, comprising the steps of:

(a) receiving lateral acceleration readings that are representative of a lateral acceleration of the vehicle;

(b) comparing the lateral acceleration readings to a brake knockback model, and estimating brake knockback based on the results of this comparison; and

(c) using the estimated brake knockback to generate a command signal for a hydraulic pump, wherein the hydraulic pump works with a disk brake system on the vehicle.

9. The method of claim 8, wherein step (a) further comprises receiving the lateral acceleration readings and using a first-order low-pass filter to process the lateral acceleration readings before performing step (b).

10. The method of claim 8, wherein the brake knockback model of step (b) is based on a lateral acceleration reference value that was obtained during a previous braking event.

11. The method of claim 8, wherein the brake knockback model of step (b) includes a flat segment, a first sloped segment extending from a first end of the flat segment, and a second sloped segment extending from a second end of the flat segment.

12. The method of claim 11, wherein the flat segment is a dead band that surrounds a lateral acceleration reference value and takes into account small lateral accelerations that will not likely result in brake knockback that is discernable to the driver.

13. The method of claim 11, wherein the first sloped segment is representative of lateral acceleration in a driver'"'"'s side direction, and the second sloped segment is representative of lateral acceleration in a passenger'"'"'s side direction.

14. The method of claim 8, wherein step (b) further comprises comparing the lateral acceleration readings from step (a) with a previously saved lateral acceleration extremity and if the lateral acceleration readings are greater in magnitude than the lateral acceleration extremity, then saving the lateral acceleration readings as a new lateral acceleration extremity.

15. The method of claim 14, wherein step (b) further comprises adding an estimated brake knockback from a first lateral acceleration extremity to an estimated brake knockback from a second lateral acceleration extremity to determine a total brake knockback estimate.

16. The method of claim 14, wherein step (b) further comprises comparing the total brake knockback estimate to a threshold, and if the total brake knockback estimate is greater than the threshold then performing step (c).

17. The method of claim of claim 16, wherein the threshold can be calibrated or modified based on a vehicle mode setting.

18. The method of claim of claim 8, further comprising the step of:

(d) receiving at least one of an accelerator pedal position signal and a brake pedal position signal, and disabling step (c) based on the at least one signal.