Machine failure isolation in multiple machine configurations using qualitative physics

• US 5,537,644 A
• Filed: 04/26/1994
• Issued: 07/16/1996
• Est. Priority Date: 04/26/1994
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Rtx Corporation)
• Original Assignee: United Technologies Corporation (Rtx Corporation)
• Inventors: Clark, Robert T., Hamilton, Thomas P.
• Primary Examiner(s): Bayerl, Raymond J.
• Assistant Examiner(s): KATBAB, ABDOLLAH
• Application Number:
  US08/233,466
• Time in Patent Office: 812 Days
• Field of Search: 395/10, 364/551.01, 364/551.02
• US Class Current: 706/52
• CPC Class Codes: G06F 11/2257 using expert systems

Abstract

The presence of particular faults in a machine is determined using constraint suspension and Qualitative Physics by prompting a user to perform a machine test procedure and provide results where the test procedure causes a machine configuration change. The machine configuration change can be due to prompting the user to modify machine control inputs or by prompting the user to perform an invasive test. In response to the configuration change, the processor can save predictions for variables and results of performing test procedures and can restore predictions and results of performing test procedures that correspond to a configuration entered as a result of the configuration change. An initial set of assumed machine symptoms can be used to determine the presence of particular faults in the machine and to generate diagnostic logic trees.

Claims

1. A method of using a processor to determine the presence of particular faults in a machine, comprising the steps of:

the processor repeatedly prompting a user to perform one of a plurality of machine test procedures and provide results thereof to the processor;

the processor prompting the user to cause a machine configuration change that renders invalid at least one of said results;

the processor generating a plurality of pending hypotheses having associated therewith a set of confluences using variables and equations to describe operation of components of the machine which are assumed not to have failed, each hypothesis being based on a model of the machine that assumes failure of a unique subset of machine components;

the processor propagating values indicative of said test results through said confluences to produce a set of predictions for values of confluence variables;

the processor discarding hypotheses which produce an inconsistent set of predictions;

the processor saving hypotheses which produce a consistent set of predictions in which no variable is determined to equal two or more conflicting values; and

the processor indicating the presence of one or more particular machine faults in response to there remaining a single hypothesis corresponding to failure of one or more particular machine components.

2. A method of using a processor to determine the presence of particular faults in a machine, according to claim 1, wherein said machine configuration change is caused by prompting the user to modify machine control inputs.

3. A method of using a processor to determine the presence of particular faults in a machine, according to claim 1, wherein said machine configuration change is caused by prompting the user to perform an invasive test.

4. A method of using a processor to determine the presence of particular faults in a machine, according to claim 1, further comprising the step of:

following said propagating step, the processor saving predictions and results of performing test procedures in response to said configuration change.

5. A method of using a processor to determine the presence of particular faults in a machine, according to claim 4, further comprising the step of:

in response to said configuration change, the processor restoring predictions and results of performing test procedures that correspond to a configuration entered as a result of said configuration change.

6. A method of using a processor to determine the presence of particular faults in a machine, comprising the steps of:

inputting an initial set of machine symptoms, wherein said initial set contains less than all possible fault symptoms of the machine;

the processor providing a run-time system containing a set of precomputed hypotheses and precomputed predictions by generating a set of pending hypotheses having associated therewith a set of confluences using variables and equations to describe operation of components of the machine which are assumed not to have failed and by propagating said assumed machine symptoms through said pending hypotheses to discard at least one pending hypothesis that produces an inconsistent set of predictions, wherein said set of precomputed hypotheses is smaller than said set of pending hypotheses;

the processor prompting a user to perform one of a plurality of machine test procedures and provide results thereof to the processor;

the processor propagating said precomputed predictions and values indicative of said test results through confluences of said precomputed hypotheses to produce a second set of predictions for values of confluence variables;

the processor discarding precomputed hypotheses which produce an inconsistent second set of predictions;

the processor saving precomputed hypotheses which produce a consistent second set of predictions in which no variable is determine to equal two or more conflicting values; and

the processor indicating the presence of one or more particular machine faults in response to there remaining a single precomputed hypothesis corresponding to failure of one or more particular machine components.

7. A method of using first and second processors to determine the presence of particular faults in a machine, comprising the steps of:

inputting an initial set of machine symptoms, wherein sad initial set contains less than all possible fault symptoms of the machine;

using the first processor to provide a run-time system containing a set of precomputed hypotheses and precomputed predictions by generating a set of pending hypotheses having associated therewith a set of confluences using variables and equations to describe operation of components of the machine which are assumed not to have failed and by propagating said assumed machine symptoms through said pending hypotheses to discard at least one pending hypothesis which produces an inconsistent set of predictions, wherein said set of precomputed hypotheses is smaller than said set of pending hypotheses;

the second processor prompting a user to perform one of a plurality of machine test procedures and provide results thereof to the second processor;

the second processor propagating said precomputed predictions and values indicative of said test results through confluences of said precomputed hypotheses to produce a second set of predictions for values of confluence variables;

the second processor discarding precomputed hypotheses which produce an inconsistent second set of predictions;

the second processor saving precomputed hypotheses which produce a consistent second set of predictions in which no variable is determined to equal two or more conflicting values; and

the second processor indicating the presence of one or more particular machine faults in response to there remaining a single precomputed hypothesis corresponding to failure of one or more particular machine components.

8. A method of using first and second processors to determine the presence of particular faults in a machine, comprising the steps of:

inputting an initial set of machine symptoms, wherein said initial set contains less than all possible fault symptoms of the machine;

using the first processor to provide a set of precomputed hypotheses and precomputed predictions by generating a set of pending hypotheses having associated therewith a set of confluences using variables and equations to describe operation of components of the machine which are assumed not to have failed and by propagating said assumed machine symptoms through said pending hypotheses to discard at least one pending hypothesis which produces an inconsistent set of predictions, wherein said set of precomputed hypotheses is smaller than said set of pending hypotheses;

using the first processor to generate a plurality of diagnostic logic trees corresponding to said precomputed hypotheses and said precomputed predictions;

the second processor prompting a user to enter actual machine test procedure results;

the second processor traversing said diagnostic logic trees in response to the actual machine test procedure results entered by the user; and

the second processor indicating the presence of one or more particular machine faults in response to traversing to a leaf node of one of said diagnostic logic trees.