Method and apparatus for determining vehicle brake effectiveness

• US 6,332,354 B1
• Filed: 03/26/1999
• Issued: 12/25/2001
• Est. Priority Date: 07/29/1997
• Status: Expired due to Fees

• Current Assignee: Insurance Corporation of British Columbia (Government of The Province of British Columbia), Norcorp Technologies, Inc.
• Original Assignee: Tom Lalor
• Inventors: Lalor, Tom, Luker, Craig, Loam, John
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US09/269,179
• Time in Patent Office: 1,005 Days
• Field of Search: 731/21, 731/28, 731/29, 701/29, 701/33, 701/36, 701/45, 701/48, 701/70, 701/71, 701/74, 701/75
• 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: B60T 8/00 Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force by changing number of effective brake cylinders in power brake systems B60T17/10
• CPC Class Codes: G01L 5/28 for testing brakes
• CPC Class Codes: G01L 5/286 Measuring deceleration

Abstract

This invention relates to a method and apparatus for determining the effectiveness of a vehicle braking system and for measuring changes in the mass of a wheeled vehicle. The method and apparatus include manually or automatically measuring and inputting vehicle mass to a computer, measuring and inputting brake system pressure during deceleration of the vehicle in a normal operating mode, measuring and inputting road slope, measuring and inputting air friction and engine friction of the vehicle, determining a predicted deceleration of the vehicle, measuring actual deceleration of the vehicle, and providing and using a computer to calculate the effectiveness of the vehicle braking system from data representing actual deceleration of the vehicle, road slope, air friction, engine friction, brake system pressure, vehicle mass, and predicted deceleration for the vehicle under comparable circumstances, and generating a signal representative of the effectiveness of the vehicle braking system. The invention also includes a mechanism to record and store data.

Claims

1. An apparatus for calculating effectiveness of a vehicle braking system during deceleration of the vehicle, comprising:

a computer;

a means for inputting a baseline deceleration rate of the vehicle to the computer;

a means for inputting the mass of the vehicle to the computer;

a low-g accelerometer for measuring a deceleration rate of the vehicle and means for inputting the deceleration rate of the vehicle to the computer;

a slope compensating means for generating a slope adjusted deceleration rate of the vehicle, and means for inputting the slope adjusted deceleration rate of the vehicle to the computer to automatically compensate for the effect of road slope during deceleration, and

a means for measuring brake system pressure of the vehicle during deceleration of the vehicle and for inputting the brake system pressure of the vehicle to the computer,

the computer having means for calculating the effectiveness of the vehicle braking system from data representing the baseline deceleration rate of the vehicle, the slope adjusted deceleration rate of the vehicle, the brake system pressure of the vehicle during deceleration of the vehicle, and the mass of the vehicle, and generating a signal representative of the effectiveness of the vehicle braking system.

2. The apparatus according to claim 1, wherein the baseline deceleration rate of the vehicle is a deceleration rate calculated for a constant predetermined brake system pressure and vehicle test mass at a time when the vehicle braking system is functioning at 100% braking effectiveness.

3. The apparatus according to claim 2, wherein the baseline deceleration rate of the vehicle is calculated by conducting and averaging data obtained during a plurality of test decelerations of the vehicle.

4. The apparatus according to claim 3, further comprising means for rejecting data obtained during one of the test decelerations of the vehicle if the data obtained does not meet predetermined test criteria.

5. The apparatus according to claim 4, wherein the predetermined test criteria comprise:

average brake pressure application rate of the vehicle during a test deceleration;

instantaneous brake pressure application rate of the vehicle during a test deceleration; and

reaching a predetermined brake system pressure of the vehicle before the speed of the vehicle drops below 5 miles per hour during a test deceleration.

6. The apparatus according to claim 5, wherein the average brake system pressure application rate of the vehicle is between 2 psi per second and 6 psi per second, the instantaneous brake pressure application rate of the vehicle is from −

10 psi per second to +40 psi per second, and the predetermined brake system pressure of the vehicle, before the speed of the vehicle drops below 5 miles per hour, is 65 psi.

7. The apparatus according to claim 6, wherein the vehicle test mass is between ¾

maximum and maximum vehicle load, and the constant predetermined brake system pressure is 60 psi.

8. The apparatus according to claim 1, further comprising means for automatically inputting the mass of the vehicle to the computer.

9. The apparatus according to claim 1, wherein the computer comprises memory means and storage means for storing data representing the baseline deceleration rate of the vehicle, the deceleration rate of the vehicle, the brake system pressure of the vehicle during deceleration of the vehicle, and the effectiveness of the vehicle braking system.

10. The apparatus according to claim 1, further comprising an output indicating device connected to the computer and responsive to the signal representative-of vehicle brake system effectiveness, for immediately indicating the vehicle brake system effectiveness during deceleration of the vehicle to the vehicle operator.

11. The apparatus according to claim 1, wherein the means for measuring the brake system pressure of the vehicle during deceleration of the vehicle is a brake line pressure transducer connected to the vehicle braking system.

12. The apparatus according to claim 1, further comprising:

an automatic braking control system connected to the computer for providing a signal representative of vehicle wheel based speed; and

a display means connected to the computer for displaying the signal representative of vehicle wheel based speed to the vehicle operator.

13. The apparatus according to claim 11, further comprising an output interface connected to the computer for providing external access to data accumulated in the memory and storage of the computer representing baseline deceleration rate of the vehicle, brake system effectiveness of the vehicle, the deceleration rate of the vehicle, and the brake system pressure of the vehicle during deceleration of the vehicle.

14. The apparatus according to claim 7, further comprising means for rejecting data obtained during deceleration of the vehicle if the data does not meet predetermined deceleration criteria.

15. The apparatus according to claim 14, wherein the predetermined deceleration criteria comprise:

the average brake pressure application rate of the vehicle during deceleration of the vehicle;

the instantaneous brake pressure application rate of the vehicle during deceleration of the vehicle; and

reaching a predetermined brake system pressure of the vehicle before the speed of the vehicle drops below 5 miles per hour during deceleration of the vehicle.

16. The apparatus according to claim 15, wherein the average brake system pressure application rate is between 2 psi per second and 6 psi per second, the instantaneous brake pressure application rate is from −

10 psi per second to +40 psi per second, and the predetermined brake system pressure, before the speed of the vehicle drops below 5 miles per hour, is 65 psi.

20. The apparatus according to claim 1, wherein the slope compensating means includes a low-g accelerometer.

17. A method for calculating effectiveness of a vehicle braking system in a vehicle having a brake pedal during deceleration of the vehicle, comprising:

providing a baseline deceleration rate for the vehicle;

providing the mass of the vehicle;

accelerating the vehicle;

applying pressure to the vehicle brake pedal to decelerate the vehicle;

determining brake system pressure of the vehicle during deceleration of the vehicle;

determining a deceleration rate of the vehicle using a low-g accelerometer;

generating a slope adjusted deceleration rate of the vehicle to automatically compensate for the effect of road slope during deceleration of the vehicle;

calculating the effectiveness of the vehicle braking system from data representing the baseline deceleration rate of the vehicle, the slope adjusted deceleration rate of the vehicle, the brake system pressure of the vehicle during deceleration of the vehicle, and the mass of the vehicle; and

generating a signal representative of the effectiveness of the vehicle braking system.

18. The method of claim 17, wherein the baseline deceleration- rate of the vehicle is a deceleration rate calculated for a constant predetermined brake system pressure and vehicle test mass at a time when the vehicle braking system is functioning at 100% braking effectiveness.

21. The method of claim 17, wherein a low-g accelerometer is used in the step of generating a slope adjusted deceleration rate of the vehicle.

19. An apparatus for calculating effectiveness of a vehicle braking system during deceleration of the vehicle, comprising:

a computer;

a means for inputting the mass of the vehicle to the computer;

a means for measuring brake system pressure of the vehicle during deceleration of the vehicle and for inputting the brake system pressure to the computer;

a means for measuring road slope during deceleration of the vehicle and for inputting the road slope to the computer, said means including a low-g accelerometer;

a means to measuring air friction of the vehicle and engine friction of the vehicle during deceleration of the vehicle and for inputting the air friction and the engine friction to the computer;

a means for determining predicted deceleration of the vehicle and for inputting the predicted deceleration of the vehicle to the computer;

a means for measuring deceleration of the vehicle and for inputting the deceleration of the vehicle to the computer;

the computer having means for calculating the effectiveness of the vehicle braking system, from data representing the deceleration of the vehicle, the road slope, the air friction of the vehicle, the engine friction of the vehicle, the brake system pressure during deceleration of the vehicle, the mass of the vehicle, and the predicted deceleration of the vehicle under comparable conditions, and generating a signal representative of the effectiveness of the vehicle braking system; and

a means connected to the computer for recording and storing data.