Sensor error detection in a dual sensor system

• US 6,485,114 B2
• Filed: 04/23/2001
• Issued: 11/26/2002
• Est. Priority Date: 08/23/2000
• Status: Expired due to Fees

• Current Assignee: Siemens VDO Automotive Corporation (Siemens AG)
• Original Assignee: Siemens VDO Automotive Corporation (Siemens AG)
• Inventors: Green, Tim E., Marlett, Brian J.
• Primary Examiner(s): Lavinder, Jack
• Assistant Examiner(s): BARTZ, CLIFFORD T
• Application Number:
  US09/840,708
• Publication Number:
  US 20020024254A1
• Time in Patent Office: 582 Days
• Field of Search: 303/122.08, 303/122.04, 303/122.05, 303/122.07, 303/168, 303/169, 303/173, 340/425.5, 340/441, 340/453, 340/463, 731/21, 701/34, 701/76
• US Class Current: 303/168
• CPC Class Codes: B60T 2270/403 Brake circuit failure
• CPC Class Codes: B60T 2270/406 Test-mode; Self-diagnosis
• CPC Class Codes: B60T 2270/413 Plausibility monitoring, cross check, redundancy
• CPC Class Codes: B60T 2270/416 Wheel speed sensor failure
• CPC Class Codes: B60T 8/171 Detecting parameters used in the regulation; Measuring values used in the regulation
• CPC Class Codes: B60T 8/885 using electrical circuitry
• CPC Class Codes: G01P 21/02 of speedometers
• CPC Class Codes: G01P 3/44 for measuring angular speed G01P3/56 takes precedence

Abstract

A method and system for determining the operating integrity of a dual sensor system takes in signals from each of the sensors in the dual sensor system. The signals are preferably generally on the same cycle, and the control evaluates whether a single sensor has sent two consecutive cycle signals to the control without a corresponding cycle from the other of the sensors. If so, an indication is made that the other of the sensors may be failing, or is intermittent. Preferably the sensors are associated with wheel speed indicators and the control is an ABS control.

Claims

1. A method of testing a pair of sensors providing signals on an approximately equal cycle comprising the steps of:

1) providing a pair of sensors each sending cyclic signals to a control;

2) receiving a signal from one of said sensors, and storing an indication of said one of said sensors being the last sensor to send a signal, and changing the stored indication when a signal is received from the other of said sensors;

3) providing a first level of warning that one of said sensors has a problem should said control identify a signal cycle from one of said sensors without a corresponding signal cycle from the other of said sensors for a predetermined number of signal cycles; and

4) said predetermined number of signals is 2, and a second higher level of warning is sent if a greater predetermined number of consecutive signal cycles from one of said sensors without a signal cycle from the other of said sensors being received.

2. A method as set forth in claim 1, wherein said predetermined number of signal cycles is greater than 2.

3. A system as recited in claim 1, wherein said sensors are vehicle wheel rotation sensors.

4. A method as set forth in claim 1, wherein said predetermined number of signal cycles is 2, and a second higher level of warning is sent if a greater predetermined number of consecutive signal cycles from one of said sensors without a signal cycle from the other of said sensors being received.

6. A method as set forth in claim 1, wherein said signal having edges and said edges of said signal are identified to provide said receiving function of Step (2).

5. A method of testing a pair of sensors providing signals on an approximately equal cycle comprising the steps of:

1) providing a pair of sensors each sending cyclic signals to a control;

2) receiving a signal from one of said sensor, and storing an indication of said one of said sensors being the last sensor to send a signal cycle, and changing the stored indication when a signal cycle is received from the other of said sensors;

3) providing an indication that one of said sensors has a problem should said control identify a signal cycle from one of said sensors without a corresponding signal cycle from the other of said sensors for a predetermined number of signal cycles; and

4) the stored indication of Step (2) is reset when a vehicle associated with said sensors has its travel direction reversed.

7. A system for providing sensor information to a control unit to make a decision comprising:

a pair of sensors each sending signals to a control unit, said signals being cyclic and on the same cycle;

said control unit for receiving said signals and utilizing said signals to make a determination of a control unit output, said control unit evaluating said signals to determine whether consecutive cycles of the said signal of one of said sensors are received without a corresponding signal being received from the other of said sensors, and said control unit providing an indication that one of said sensors may be failing if consecutive signals are received from one of said sensors without a corresponding signal from the other of said sensors; and

said control unit indication being reset to zero should a vehicle associated with said system have its travel direction reversed.

8. The system as set forth in claim 7, wherein said sensors arc associated with vehicle wheels, and said control associated with an ABS braking system.

9. The system as set forth in claim 7, wherein a counter is provided as part of said control unit for counting receipt of a signal from one of said sensors, and for counting the number of consecutive signals.

10. A system as set forth in claim 7, wherein said signals having edges and said control looks for said edges of said signal.