Diagnosing intermittent faults

• US 8,024,610 B2
• Filed: 11/15/2007
• Issued: 09/20/2011
• Est. Priority Date: 05/24/2007
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: de Kleer, Johan
• Primary Examiner(s): BONZO, BRYCE P
• Application Number:
  US11/940,493
• Publication Number:
  US 20080294578A1
• Time in Patent Office: 1,405 Days
• Field of Search: 714/26, 714/33
• US Class Current: 714/26
• CPC Class Codes: G06F 11/2257 using expert systems

Abstract

A method and system for diagnosing any combination of persistent and intermittent faults. The behavior of a system under test is obtained by measuring or probing the system at a particular location(s). The predicted behavior of a modeled system corresponding to the system under test is investigated by drawing inferences based on at least conditional probabilities, prior observations and component models. The predictions are compared to their corresponding points in the system under test. A determination is made if a conflict exists between the measured behavior and the predicted behavior, and the conditional probabilities are adjusted to more and more accurately reflect the action fault(s) in the system under test. The conflicts or deviations between the obtained predicted behavior and the actual behavior are used to isolate the components of the system causing the faults.

Claims

1. A method for diagnosing any combination of persistent and intermittent faults or intermittent faults in a system, comprising:

obtaining a measured behavior of a system by measuring and/or probing the system at particular points;

investigating a predicted behavior of a modeled system of the system by drawing inferences based on at least conditional probabilities, prior observations and component models of the modeled system;

comparing the predictions to their corresponding points in the system;

determining if conflicts and/or deviations exist between the measured behavior and the predicted behavior;

adjusting the conditional probabilities to more and more accurately reflect action faults in the system, so they will accept a possibility that a subsequent measuring and/or probing will produce a different value or output; and

using the conflicts or deviations between the predicted behavior and the actual behavior to obtain a final result based on a new value or output,

wherein intermittent failures arise from a stochastic physical process which is intermittent at any level of abstraction of the system model, and wherein the intermittent failures diagnosed by adjusting conditional probabilities so that they continue to accept the possibility the subsequent measuring and/or probing will produce a different value acts to avoid irreconcilable inconsistencies in the system.

2. The method of claim 1 further including, generating an error output when the final result is not reached within a predetermined number of measurements and/or probes.

3. The method according to claim 1 wherein the final result includes isolating the component causing the fault or faults.

4. The method according to claim 1 further including a next stage of measuring and/or probing, which includes determining a next location and/or point to measure and/or probe.

5. The method according to claim 1 wherein the system model, models the dynamic behavior of the system.

6. The method according to claim 5 wherein the dynamic behavior of the system is viewed as a sequence of non-temporal events.

20. The method of claim 1, wherein the system includes components, the components having inputs and at least some of the particular points which are measured and/or probed are the inputs of the components and ones of the multiple inputs of the system which are measured and/or probed.

21. The method according to claim 1, wherein the faults are at least one of multiple simultaneous persistent faults and multiple simultaneous intermittent faults.

7. A method of troubleshooting a real world system having multiple components, and containing any combination of intermittent or non-intermittent faults, the method comprising:

generating a model of the real world system, the system model including multiple model components;

associating with each model component of the system model, two probabilities, (1) a probability the real world component deviates from its design such that it may exhibit a malfunction, and (2) a conditional probability the faulted component malfunctions when observed;

recalculating the conditional probabilities associated with possible fault causes, to guide a next stage of observation and/or measurement;

undertaking a next stage of observation and/or measurement;

determining when enough data has been obtained; and

reaching a final result.

8. The method of claim 7 further including, generating an error output when an acceptable final result is not reached within a predetermined number of measurements and/or observations.

9. The method according to claim 7 wherein reaching the final result includes isolating the component causing the fault or faults.

10. The method according to claim 7 wherein the step of undertaking the next stage of observation and/or measurement includes determining a next location to observe and/or take a measurement.

11. The method according to claim 7 wherein the system model, models the dynamic behavior of the system.

12. The method according to claim 11 wherein the dynamic behavior of the system is viewed as a sequence of non-temporal events.

13. The method according to claim 7 wherein intermittent failures arise from a stochastic physical process which is intermittent at any level of abstraction of the system model.

14. A troubleshooting system implemented by a computing device which includes a processor, a memory an input and a display the troubleshooting system comprising:

a diagnostic section configured to diagnose any combination of persistent and intermittent faults or intermittent faults in a real world multi-component system by,

a probe section configured to obtain measured behaviors of the real world multi-component system by measuring or probing the real world multi-component system at particular points;

an inference section configured to investigate predicted behaviors of a modeled system of the real world multi-component system by drawing inferences based on at least conditional probabilities, prior observations and component models;

a comparison section configured to compare the predicted behaviors to their corresponding points in the real world multi-component system;

determining if conflicts or deviations exist between the measured behaviors and the predicted behaviors;

adjusting the conditional probabilities to more and more accurately reflect actual faults in the real world multi-component system, so they will accept a possibility that a subsequent measurement will produce a different value; and

using the conflicts and/or deviations between the predicted behaviors and the actual measured behaviors to obtain a final result based on a new value or output,

wherein intermittent failures arise from a stochastic physical process which is intermittent at any level of abstraction of the system model, and wherein the intermittent failures diagnosed by adjusting conditional probabilities so that they continue to accept the possibility the subsequent measuring and/or probing will produce a different value acts to avoid irreconcilable inconsistencies in the real world multi-component system.

15. The system according to claim 14 further including,

generating an error output when an acceptable final result is not reached within a predetermined number of measurements and/or probes.

16. The system according to claim 14 wherein obtaining the final result includes isolating the component causing the fault or faults.

17. The system according to claim 14 wherein the step of undertaking a next stage of observation and/or measurement includes determining a next location to observe and/or take a measurement.

18. The system according to claim 14 wherein the system model, models the dynamic behavior of the system.

19. The system according to claim 18 wherein the dynamic behavior of the system is viewed as a sequence of non-temporal events.