Method and apparatus for detecting faulty operation of a wheel speed sensor

• US 5,406,485 A
• Filed: 11/09/1993
• Issued: 04/11/1995
• Est. Priority Date: 11/09/1993
• Status: Expired due to Term

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delco Electronics Corporation (General Motors Company)
• Inventors: Wise, William D., Schousek, Brian W.
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US08/149,498
• Time in Patent Office: 518 Days
• Field of Search: 364/426.02, 364/426.04, 364/424.03, 364/424.04, 364/431.12, 364/551.01, 364/565, 364/571.01, 364/483, 324/161, 280/735, 303/92, 303/94, 303/100, 303/102, 303/106
• US Class Current: 701/29
• CPC Class Codes: B60T 2270/416 Wheel speed sensor failure
• CPC Class Codes: B60T 8/885 using electrical circuitry

Abstract

Faulty operation of a two-lead wheel speed sensor in a vehicle control system is detected and distinguished from transients by measuring a common mode voltage of the sensor and applying such voltage to a window comparator. Analog-to-digital conversion circuitry for capturing wheel speed signals is disabled so long as the measured voltage falls outside the comparator window. When the measured voltage is outside the comparator window for at least a given time limit, an open circuit fault condition is indicated. Additionally, the sensor lead voltages are compared to threshold voltages; when both voltages exceed the thresholds for at least a given time limit, a short circuit fault condition is indicated. The windows, thresholds and time limits are programmable by the vehicle control system computer.

Claims

1. Apparatus for detecting faulty operation of a wheel speed sensor which develops cyclic output signals on first and second output leads thereof, comprising:

means for establishing upper and lower voltage potentials;

bias means including a first resistor coupling the first output lead to said upper voltage potential, and a second resistor coupling the second output lead to said lower voltage potential;

measurement means including a voltage divider coupling said first and second output leads for measuring a voltage intermediate the output signals on said first and second output leads;

a window comparator for comparing said measured voltage with first and second threshold voltages defining a range of voltages within which said measured voltage lies during normal operation of said wheel speed sensor; and

means for producing a first abnormal operation signal indicative of a possible short circuit condition of said wheel speed sensor when said measured voltage is outside the range of voltages defined by said first and second threshold voltages.

2. The apparatus of claim 1, further comprising:

reference generating means for defining a plurality of selectable reference voltages; and

computer controlled means connected to said reference generating means for selecting the first and second threshold voltages of said window comparator form among said plurality of selectable reference voltages.

3. The apparatus of claim 1, wherein a short circuit fault condition is indicated when said first abnormal operation signal is produced for at least a first time interval.

4. The apparatus of claim 1, further comprising:

means for comparing the output signal on said first output lead with a third threshold voltage;

means for comparing the output signal on said second output lead with a fourth threshold voltage; and

means for producing a second abnormal operation signal indicative of a possible open circuit condition of said wheel speed sensor when said the output signal on said first output lead exceeds said third voltage and the output signal on said second output lead exceeds said fourth threshold voltage.

5. The apparatus of claim 4, wherein an open circuit fault condition is indicated when said second abnormal operation signal is produced for at least a second time interval.

6. The apparatus of claim 1, further comprising:

means for measuring a differential voltage according to a difference between the output signals on said first and second output leads;

a digital utilization circuit; and

an analog to digital conversion circuit for generating digital representations of the measured differential voltage for said digital utilization circuit, such conversion circuit including lockout means responsive to said first abnormal operation signal for suspending conversion so long as said first abnormal operation signal is produced.

7. A method for detecting faulty operation of a wheel speed sensor which develops cyclic output signals on first and second output leads thereof, when the first output lead is coupled to an upper voltage potential through a first resistor, and the second output lead is coupled to a lower voltage potential through a second resistor the method of comprising the steps of:

measuring a voltage intermediate the output signals on said first and second output leads;

comparing said measured voltage with first and second threshold voltages defining a range of voltages within which said measured voltage lies during normal operation of said wheel speed sensor; and

producing a first abnormal operation signal indicative of a possible short circuit condition of said wheel speed sensor when said measured voltage is outside said range of voltages defined by said first and second threshold voltages.

8. The method of claim 7, further including the steps of:

measuring a differential voltage according to a difference between the output signals on said first and second output leads;

converting said measured differential voltage to a digital signal for application to a digital utilization circuit; and

suspending conversion of said measured differential voltage so long as said first abnormal operation signal is produced.

9. The method of claim 7, further including the steps of:

setting a first time limit; and

indicating a short circuit fault condition of said wheel speed sensor when said first abnormal operation signal is produced for at least said first time limit.

10. The method of claim 7, further including the steps of:

comparing the output signal on said first output lead with a third threshold voltage;

comparing the output signal on said second output lead with a fourth threshold voltage; and

producing a second abnormal operation signal indicative of a possible open circuit condition of said wheel speed sensor when said the output signal on said first output lead exceeds said third threshold voltage and the output signal on said second output lead exceeds said fourth threshold voltage.

11. The method of claim 10, further including the steps of:

setting a second time limit; and

indicating an open circuit fault condition of said wheel speed sensor when said second abnormal operation signal is produced for at least said second time limit.