Speed sensor instability detection

• US 7,236,872 B2
• Filed: 11/24/2003
• Issued: 06/26/2007
• Est. Priority Date: 11/24/2003
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Scelers, Herve
• Primary Examiner(s): Camby; Richard M.
• Application Number:
  US10/720,624
• Publication Number:
  US 20050114008A1
• Time in Patent Office: 1,310 Days
• Field of Search: 701/93, 701/36, 701/92, 701 82- 91, 701 94- 96, 303/141
• US Class Current: 701/92
• CPC Class Codes: B60T 2270/413 Plausibility monitoring, cross check, redundancy
• CPC Class Codes: B60T 8/885 using electrical circuitry

Abstract

A speed sensor instability detection and correction system for use with a vehicle includes a speed sensor output variation extractor monitoring and recording change in output of a speed sensor over time. A speed sensor output variation comparison module detects speed sensor instability based on a comparison between the speed sensor output variation and a predetermined threshold. An output speed determination module selectively determines output speed in alternative ways based on whether speed sensor instability is detected.

Claims

1. A method for detecting wheel slippage based on output speed of a wheeled vehicle, comprising:

determining whether output speed instability is detected;

generating a median filtered output speed when output speed instability is detected; and

determining whether wheel slippage is present based on the median filtered output speed when output speed instability is detected.

2. The method of claim 1 wherein said determining whether output speed instability is detected includes monitoring change in a pulley speed sensor output signal over time.

3. The method of claim 2 wherein said determining whether output speed instability is detected further includes making a comparison between change in pulley speed over time and a predetermined threshold.

4. The method of claim 3 wherein said determining whether output speed instability is detected further includes detecting instability based on results of the comparison over time.

5. The method of claim 1 wherein said generating a median filtered output speed further includes filtering an output signal of a pulley speed sensor with a median filter.

6. The method of claim 1 wherein said determining whether wheel slippage is present includes calculating speed ratio based on the median filtered output speed.

7. The method of claim 6 wherein said determining whether wheel slippage is present further includes calculating wheel axle torque based on the speed ratio.

8. The method of claim 7 wherein said determining whether wheel slippage is present further includes:

calculating an output derivative based on the median filtered output speed; and

calculating an expected derivative based on the wheel axle torque.

9. The method of claim 8 wherein said determining whether wheel slippage is present further includes comparing the output derivative to the expected derivative.

10. The method of claim 1 further comprising:

generating a Kalman filtered output speed when output speed instability is not detected; and

determining whether wheel slippage is present based on the Kalman filtered output speed when output speed instability is not detected.