Rough Road Detection System Used in an On-Board Diagnostic System

• US 20080177437A1
• Filed: 01/19/2007
• Published: 07/24/2008
• Est. Priority Date: 01/19/2007
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Hrovat, Davor, Feldkamp, Timothy, Stephens, Craig, McConnell, Mitch, Varady, Arthur, Fridman, Moses, Asgari, Jahan
• Granted Patent: US 8,060,275 B2
• Time in Patent Office: Days
• US Class Current: 701/31
• CPC Class Codes: B60W 40/06 Road conditions
• CPC Class Codes: B60W 50/0205 Diagnosing or detecting failures; Failure detection models
• CPC Class Codes: B60W 50/045 Monitoring control system parameters

Abstract

An on-board diagnostic system of a vehicle comprises a diagnostic component configured to detect a vehicle operating condition and to produce an error output when the vehicle operating condition is determined to be abnormal; and a rough road detector configured to determine an average level of roughness of a road surface based on signals from wheel speed sensors, to compare the roughness with a predetermined threshold, and to disable the error output of the diagnostic component or switch to an alternate calibration for the diagnostic component if the roughness level has exceeded the predetermined threshold.

Claims

1. An on-board diagnostic system of a vehicle, comprising:

a diagnostic component configured to detect a vehicle operating condition and to produce an error output when the vehicle operating condition is determined to be abnormal; and

a rough road detector configured to determine an average level of roughness of a road surface based on signals from wheel speed sensors, to compare the roughness with a predetermined threshold, and to disable the error output of the diagnostic component or switch to an alternate calibration for the diagnostic component if the roughness level has exceeded the predetermined threshold.

2. The on-board diagnostic system of claim 1, wherein the rough road detector comprises:

a first filter configured to receive input signals of wheel speeds and determine changes of wheel speed such that outputs from the first filter correspond to levels of road roughness; and

a second filter configured to process the output of the first filter such that the levels of road roughness are averaged over a predetermined time interval to produce an average level of road roughness.

3. The on-board diagnostic system of claim 2, wherein the first filter comprises a second-order Butterworth high pass filter or a band pass filter.

4. The on-board diagnostic system of claim 3, wherein the second filter is a rolling average filter.

5. The on-board diagnostic system of claim 2, wherein the rough road detector further comprises a first computation component configured to square an output from the first filter.

6. The on-board diagnostic system of claim 1, wherein the rough road detector further comprises a second computation component configured to take square-root of an output from the second filter.

7. The on-board diagnostic system of claim 4, wherein the predetermined time interval is approximately two seconds.

8. The on-board diagnostic system of claim 1, wherein the rough road detector is configured to perform hysteresis on the output from the rolling average filter to inhibit undesired disabling of the error output of the diagnostic component.

9. The on-board diagnostic system of claim 1, wherein the rough road detector is configured to suspend the disabling of the error output of the diagnostic component by the rough road detector during a braking event.

10. The on-board diagnostic system of claim 1, wherein the rough road detector is configured to suspend the disabling of the error output of the diagnostic component by the rough road detector, if an anti-lock brake system is degraded.

11. The on-board diagnostic system of claim 1, wherein the diagnostic component is a misfire monitor configured to detect a misfire in a cylinder of an engine of the vehicle.

12. The on-board diagnostic system of claim 1, wherein the diagnostic component is a stability control monitor configured to detect whether a stability control system of the vehicle is operating normally.

13. A rough road detector for a vehicle, comprising:

a high pass filter configured to receive input of non-driven wheel speeds from wheel speed sensors, and to determine changes of wheel speed to produce an output indicating a current magnitude of roughness of a road surface;

a rolling average filter configured to process the output of the high pass filter such that an average roughness of the road surface is determined over a predetermined time interval; and

a comparator configured to compare an output from the rolling average filter to a first predetermined calibratable threshold to determine whether the average roughness of the road surface has exceeded the first threshold to determine a type of road surface;

wherein the rough road detector is configured to output a flag to disable an error output of a diagnostic component of the vehicle or switch to an alternate calibration for the diagnostic component, to reduce false errors of the diagnostic component.

14. The road surface condition detector of claim 13, wherein the determination of the changes of the wheel speeds by the high pass filter includes removing slowly changing components of the wheel speed signals.

15. The road surface condition detector of claim 13, wherein the wheel speeds include wheel speeds from at least one of non-driven wheel.

16. The road surface condition detector of claim 15, wherein the wheel speeds further include wheel speeds from at least one of the driven wheels.

17. The road surface condition detector of claim 13, wherein the predetermined time interval is approximately two seconds.

18. The road surface condition detector of claim 13, wherein the diagnostic component is a misfire monitor.

19. The road surface condition detector of claim 13, wherein the comparator further configured to compare an output from the rolling average filter to a second predetermined calibratable threshold to determine whether the average roughness of the road surface has exceeded the second threshold to determine a type of road surface;

20. A method to reduce false positive error determinations from a diagnostic component in a vehicle traveling on a road, comprising:

receiving input signals from wheel speed sensors;

determining changes of the input signals using a high pass filter so that output signals from the high pass filter indicates a current magnitude of external roughness of the road surface;

processing the output signals from the high pass filter using a rolling average filter so that a roughness level is determined over a predetermined time interval;

comparing the output signals from the rolling average filter to a predetermined threshold; and

disabling an error output of the diagnostic component if the roughness level has exceeded the predetermined threshold.

21. The method of claim 20, wherein the method further comprises instructing a misfire monitor of an on-board diagnostic system to disable the misfire output or switch to an alternate calibration for the diagnostic component when the roughness has exceeded the predetermined threshold.

22. The method of claim 20, wherein determining changes of the input signals using a high pass filter includes removing semi-steady state components of the wheel speed signals.

23. The method of claim 20, wherein the predetermined time interval used by the rolling average filter is approximately two seconds.