Fault detecting apparatus and method

• US 5,742,624 A
• Filed: 02/23/1995
• Issued: 04/21/1998
• Est. Priority Date: 08/24/1992
• Status: Expired due to Fees

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Soma, Hiroshi, Ishiguro, Susumu, Irie, Atsushi, Tabata, Naohiro, Nishidai, Hajime
• Primary Examiner(s): CHUNG, PHUNG M
• Application Number:
  US08/387,846
• Time in Patent Office: 1,153 Days
• Field of Search: 371/48, 395/185.01, 395/185.02, 395/185.03, 395/185.04
• US Class Current: 714/799
• CPC Class Codes: G05B 19/058 Safety, monitoring
• CPC Class Codes: G05B 2219/1181 Detection of I-O faults, shut down of I-O

Abstract

A control system for detecting a potentially faulty detector which may be causing faulty actuation of an actuator of a controlled system has an input-signal memory for storing the state of an input signal from the detector, an auxiliary input-signal memory for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to the actuator in accordance with predetermined logic in conformity with the states of the input signals stored in the input-signal memory and auxiliary input-signal memory, and an output-signal memory for storing the state of an output signal generated by the arithmetic-logic unit. An identification code of an abnormal output signal corresponding to the abnormal actuator which is designated, and an input signal that has influenced a logical operation, performed by the arithmetic-logic unit, and which gave rise to the designated abnormal output signal, is extracted. If the extracted input signal is the signal that has been stored in the input-signal memory, an identification code of this input signal is stored in a storage device.

Claims

1. An apparatus for detecting a fault in a detector through a control apparatus, which controls a controlled system including one or two or more detectors and one or two or more actuators, having an input-signal memory for storing the state of an input signal from said detector, an auxiliary input-signal memory for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the states of the input signals stored in said input-signal memory, and auxiliary input-signal memory and an output-signal memory for storing the state of the output signal generated by said arithmetic-logic unit;

wherein when there is an actuator not operating normally in said controlled system, a dector that is possibly faulty in said controlled system is detected through said control apparatus, said apparatus for detecting the fault comprising;

a designation input unit for designating an identification code of an abnormal output signal corresponding to the actuator not operating normally;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal designated by said designation input unit;

a determining unit for determining whether the input signal extracted by said input-signal extractor is the signal that has been stored in said input-signal memory; and

a storage device which, if result of the determination by said determining unit is that the extracted input signal is the signal that has been stored in the input-signal memory, stores an identification code of this input signal.

2. The apparatus for detecting a fault in a detector according to claim 1, further comprising a display unit for displaying the identification code of the input signal that has been stored in said storage device.

3. The apparatus for detecting a fault in a detector according to claim 1, wherein in a case where the result of determination by said determining unit is that the extracted input signal is the signal that has been stored in the auxiliary input-signal memory and that it is controlled by the state of the output signal of the control apparatus, said input-signal extractor repeats extraction of the input signal that has influenced the logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal that controls the state of said extracted input signal.

4. The apparatus for detecting a fault in a detector according to claim 3, further comprising a degree-of-priority calculator which, in a case where a plurality of input signals have been extracted, calculates a degree of priority of each input signal;

said input-signal extractor ending extraction processing when the number of input signals stored in said storage device becomes larger than a predetermined prescribed number or when there are no longer any input signals to be extracted; and

in a case where extraction processing by said input-signal extractor has not ended, said determining unit performs the determination processing in regular order starting from the input signal for which the degree of priority is calculated to be high by said degree-of-priority calculator when a plurality of input signals have been extracted, and performs the determination processing with regard to one input signal when one input signal has been extracted.

5. The apparatus for detecting a fault in a detector according to claim 4, wherein said degree-of-priority calculator calculates a degree of priority by obtaining features of each extracted input signal and executing fuzzy reasoning based upon these features.

6. An apparatus for detecting a fault in a detector according to claim 1, wherein said control apparatus is constituted by a programmable logic controller;

the state of the input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

7. The apparatus for detecting a fault in a detector according to claim 1, wherein said apparatus for detecting a fault in a detector is implemented by a computer system.

8. An apparatus for detecting a fault in an actuator through a control apparatus, which controls a controlled system including one or two or more detectors and one or two or more actuators, having an input-signal memory for storing the state of aninput signal from said detector, an auxiliary input-signal memory means for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the states of the input signals stored in said input-signal memory and auxiliary input-signal memory, and an output-signal memory for storing the state of the output signal generated by said arithmetic-logic unit;

wherein when there is an actuator not operating normally in said controlled system, the actuator is detected through said control apparatus, said apparatus for detecting the fault comprising;

a first determining unit for determining whether a prescribed condition for generation of an output signal to be applied to the actuator has been established;

a second determining unit for determining whether the state of said output signal is normal; and

a third determining unit which, in a case where it has been determined by said first determining unit and second determining unit that the state of the output signal has not become normal even upon elaspe of a prescribed time from establishment of said prescribed condition, determines that the actuator to which this output signal is to be applied is faulty.

9. An apparatus for detecting a fault in an actuator according to claim 8, wherein said control apparatus is constituted by a programmable logic controller;

the state of said input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

10. An apparatus for detecting a fault in an actuator according to claim 9, wherein said first determining unit, second determining unit and third determining unit are provided in the programmable logic controller.

11. The apparatus for detecting a fault in an actuator according to claim 8, wherein said apparatus for detecting a fault in an actuator is implemented by a computer system.

12. An apparatus for detecting a fault in an actuator and a detector through a control apparatus, which controls a controlled system including one or two or more detectors and one or two or more actuators, having an input-signal memory for storing the state of an input signal from said detector, an auxiliary input-signal memory for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the states of the input signals stored in said input-signal memory and auxiliary input-signal memory, and an output-signal memory for storing the state of the output signal generated by said arithmetic-logic unit;

wherein when there is an actuator not operating normally in said controlled system, the actuator is detected through said control apparatus and a detector that is possibly faulty in said controlled system and a cause of failure of the actuator is detected through said control apparatus, said apparatus for detecting the fault comprising;

a first determining unit for determining whether a prescribed condition for generation of an output signal to be aplied to the actuator has been established;

a second determining unit for determining whether the state of said output signal is normal;

a third determining unit which, in a case where it has been determined by said first determining unit and second determining unit that the state of the output signal has not become normal even upon elaspe of a prescribed time from establishment of said prescribed condition, determines that the actuator to which this output signal is to be applied is faulty;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic means, which gave rise to the abnormal output signal determined by said third determining unit;

a fourth determining unit for determining whether the input signal extracted by said input-signal extractor is the signal that has been stored in said input-signal memory; and

a storage device which, if result of the determination by said fourth determining unit is that the extracted input signal is the signal that has been stored in the input-signal memory, stores an identification code of this input signal.

13. The apparatus for detecting a fault in an actuator and a detector according to claim 12, further comprising a display unit for displaying the identification code of the input signal that has been stored in said storage device.

14. The apparatus for detecting a fault in an actuator and a detector according to claim 12, wherein in a case where the result of determination by said fourth determining unit is that the extracted input signal is the signal that has been stored in the auxiliary input-signal memory and that it is controlled by the state of the output signal of the control apparatus, said input-signal extractor repeats extraction of the input signal that has influenced the logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal that controls the state of said extracted input signal.

15. The apparatus for detecting a fault in an actuator and a detector according to claim 14, further comprising a degree-of-priority calculator which, in a case where a plurality of input signals have been extracted, calculates a degree of priority of each input signal;

said input-signal extractor ending extraction processing when the number of input signals stored in said storage device becomes larger than a predetermined prescribed number or when there are no longer any input signals to be extracted; and

in a case where extraction processing by said input-signal extractor has not ended, said fourth determining unit performs the determination processing in regular order starting from the input signal for which the degree of priority is calculated to be high by said degree-of-priority calculator when a plurality of input signals have been extracted, and performs the determination processing with regard to one input signal when one input signal has been extracted.

16. The apparatus for detecting a fault in an actuator and a detector according to claim 15, wherein said degree-of-priority calculator calculates a degree of priority by obtaining features of each extracted input signal and executing fuzzy reasoning based upon these features.

17. The apparatus for detecting a fault in an actuator and a detector according to claim 12, wherein said control apparatus is a programmable logic controller;

the state of said input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

18. The apparatus for detecting a fault in an actuator and a detector according to claim 17, wherein said first determining unit, said second determining unit and third determining unit are provided in the programmable logic controller.

19. The apparatus for detecting a fault in an actuator and a detector according to claim 12, wherein said apparatus for detecting a fault in an actuator and a detector is implemented by a computer system.

20. An apparatus for detecting a fault in an input signal;

wherein a control apparatus, which controls a controlled system including one or two or more detectors and one or two or more actuators, has an input-signal memory for storing the state of an input signal from said detector, an auxiliary input-signal memory for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the states of the input signals stored in said input-signal memory and auxiliary input-signal memory, and an output-signal memory for storing the state of the output signal generated by said arithmetic-logic unit; and

wherein when there is an actuator not operating normally in said controlled system, an input signal that is possibly abnormal is detected, said apparatus for detecting the fault comprising;

a designation input unit for designating an identification code of an abnormal output signal corresponding to the actuator not operating normally;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by the arithmetic-logic unit, which gave rise to the abnormal output signal designated by said designation input unit; and

a storage device for storing an identification code of the input signal extracted by said input-signal extractor.

21. The apparatus for detecting a fault in an input signal according to claim 20, further comprising a display unit for displaying the identification code of the input signal that has been stored in said storage device.

22. The apparatus for detecting a fault in an input signal according to claim 20, wherein in a case where said extracted input signal is the signal that has been stored in the auxiliary input-signal memory and is controlled by the state of the output signal of the control apparatus, said input-signal extractor repeats extraction of the input signal that has influenced the logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal that controls the state of said extracted input signal.

23. The apparatus for detecting a fault in an input signal according to claim 22, further comprising a degree-of-priority calculator which, in a case where a plurality of input signals have been extracted, is for calculating a degree of priority of each input signal;

said input-signal extractor ending extraction processing when the number of input signals stored in said storage device becomes larger than a predetermined prescribed number or when there are no longer any input signals to be extracted.

24. The apparatus for detecting a fault in an input signal according to claim 23, wherein said degree-of-priority calculator calculates a degree of priority by obtaining features of each extracted input signal and executing fuzzy reasoning based upon these features.

25. The apparatus for detecting a fault in an input signal according to claim 20, wherein said apparatus for detecting a fault in an input signal is constituted by a programmable logic controller;

the state of the input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

26. The apparatus for detecting a fault in an input signal according to claim 20, wherein said apparatus for detecting a fault in an input signal is implemented by a computer system.

27. A method of detecting a fault in a detector through a control apparatus, which controls a controlled system including one or two or more detectors and one or two or more actuators, having an input-signal memory for storing the state of an input signal from said detector, an auxiliary input-signal memory for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the states of the input signals stored in said input-signal memory and auxiliary input-signal memory, and an output-signal memory for storing the state of the output signal generated by said arithmetic-logic unit;

wherein when there is an actuator not operating normally in said controlled system, a detector that is possibly faulty in said controlled system is detected through said control apparatus, said method of detecting the fault comprising the steps of;

extracting, on the basis of a designated abnormal output signal corresponding to the actuator not operating normally, an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to this abnormal output signal;

determining whether said extracted input signal is the signal that has been stored in said input-signal memory; and

if result of said determination is that the extracted input signal is the signal that has been stored in the input-signal memory, storing an identification code of this input signal in a storage device.

28. The method of detecting a fault in a detector according to claim 27, further comprising a step of displaying the identification code of the input signal that has been stored in said storage device.

29. The method of detecting a fault in a detector according to claim 27, wherein in a case where the result of said determination is that the extracted input signal is the signal that has been stored in the auxiliary input-signal memory and that it is controlled by the state of the output signal of the control apparatus, extraction of the input signal that has influenced the logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal that controls the state of said extracted input signal is repeated.

30. The method of detecting a fault in a detector according to claim 29, further comprising steps of:

calculating a degree of priority of each input signal in a case where a plurality of input signals have been extracted;

ending extraction of said input signal when the number of input signals stored in said storage device becomes larger than a predetermined prescribed number or when there are no longer any input signals to be extracted; and

in a case where extraction has not ended, performing said determination in regular order starting from the input signal for which the degree of priority is calculated to be high when a plurality of input signals have been extracted, and performing said determination with regard to one input signal when one input signal has been extracted.

31. The method of detecting a fault in a detector according to claim 30, further comprising a step of calculating said degree of priority by obtaining features of each extracted input signal and executing fuzzy reasoning based upon these features.

32. The method of detecting a fault in a detector according to claim 27, wherein said control apparatus is constituted by a programmable logic controller;

the state of said input signal corresponds to the state of a contact of the programmable logic controller; and

the state of the said output signal corresponds to the state of a relay of the programmable logic controller.

33. A method of detecting a fault in an actuator through a control apparatus, which controls a controlled system including one or two or more detectors and one or two or more actuators, having an input-signal memory for storing the state of an input signal from said detector, an auxiliary input-signal memory for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the states of the input signals stored in said input-signal memory and auxiliary input-signal memory, and an output-signal memory for storing the state of the output signal generated by said arithmetic-logic unit;

wherein when there is an actuator not operating normally in said controlled system, the actuator is detected through the control apparatus, the method of detecting the fault comprising the steps of;

performing a first determination as to whether a prescribed condition for generation of an output signal to be applied to the actuator has been established;

performing a second determination as to whether the state of said output signal is normal; and

in a case where it has been determined that the state of the output signal has not become normal even upon elapse of a prescribed time from establishment of said prescribed condition, performing a third determination that the actuator to which this output signal is to be applied is faulty.

34. The method of detecting a fault in an acutator according to claim 33, wherein said control apparatus is constituted by a programmable logic controller;

the state of said input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

35. The method of detecting a fault in an actuator according to claim 34, wherein the programmable logic controller performs said first, second and third determinations.

36. A method of detecting a fault in an actuator and a detector through a control apparatus, which controls a controlled system including one or two or more detectors and one or two or more actuators, having an input-signal memory for storing the state of an input signal from said detector, an auxiliary input-signal memory for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the states of the input signals stored in said input-signal memory and auxiliary input-signal memory, and an output-signal memory for storing the state of the output signal generated by said arithmetic-logic unit;

wherein when there is an actuator not operating normally in said controlled system, the actuator is detected through the control apparatus and a detector that is possibly faulty in the controlled system and a cause of failure of the actuator is detected through said control apparatus, the method of detecting the fault comprising the steps of;

performing a first determination as to whether a prescribed condition for generation of an output signal to be applied to the actuator has been established;

performing a second determination as to whether the state of said output signal is normal;

in a case where it has been determined that the state of the output signal has not become normal even upon elapse of a prescribed time from establishment of said prescribed condition, performing a third determination that the actuator to which this output signal is to be applied is faulty;

extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal for which said fault has been determined;

performing a fourth determination as to whether said extracted input signal is the signal that has been stored in said input-signal memory; and

if result of said fourth determination is that the extracted input signal is the signal that has been stored in the input-signal memory, storing an identification code of this input signal.

37. The method of detecting a fault in an actuator and a detector according to claim 36, further comprising a step of displaying the identification code of the input signal that has been stored in said storage device.

38. The method of detecting a fault in an actuator and a detector according to claim 36, wherein in a case where the result of said fourth determination is that the extracted input signal is the signal that has been stored in the auxiliary input-signal memory and that it is controlled by the state of the output signal of the control apparatus, extraction of the input signal that has influenced the logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal that controls the state of said extracted input signal is repeated.

39. The method of detecting a fault in an actuator and a detector according to claim 38, further comprising steps of

calculating a degree of priority of each input signal in a ease where a plurality of input signals have been extracted;

ending extraction of said input signal when the number of input signals stored in said storage device becomes larger than a predetermined prescribed number or when there are no longer any input signals to be extracted; and

in a case where extraction has not ended, performing the determination, as to whether the extracted input signal has been stored in said input-signal memory means, in regular order starting from the input signal for which the degree of priority is calculated to be high when a plurality of input signals have been extracted, and performing the determination, as to whether the extracted input signal has been stored in said input-signal memory when one input signal has been extracted.

40. The method of detecting a fault in an actuator and a detector according to claim 39, further comprising a step of calculating said degree of priority by obtaining features of each extracted input signal and executing fuzzy reasoning based upon these features.

41. The method of detecting a fault in an actuator and a detector according to claim 36, wherein said control apparatus is constituted by a programmable logic controller;

the state of said input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

42. The method of detecting a fault in an actuator and a detector according to claim 41, wherein the programmable logic controller performs said first, second and third determinations.

43. A method of detecting a fault in an input signal;

wherein a control apparatus, which controls a controlled system including one or two or more detectors and one or two or more actuators, having an input-signal memory for storing the state of an input signal from said detector, an auxiliary input-signal memory for storing the state of an input signal provided by an auxiliary-signal generator, an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the states of the input signals store in said input-signal memory and auxiliary input-signal memory, and an output-signal memory for storing the state of the output signal generated by said arithmetic-logic unit; and

wherein when there is an actuator not operating normally in said controlled system, an input signal that is possibly abnormal is detected, the method of detecting the fault comprising the steps of;

extracting, on the basis of a designated abnormal output signal corresponding to the actuator not operating normally, an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to this abnormal output signal; and

storing an identification code of said extracted input signal in a storage device.

44. The method of detecting a fault in an input signal according to claim 43, further comprising a step of displaying the identification code of the input signal that has been stored in said storage device.

45. A control apparatus, which is equipped with a function for detecting a fault in a detector, for controlling a controlled system including one or two or more detectors and one or two or more actuators, said control apparatus comprising:

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a designation input unit which, when there is an actuator not operating normally in said controlled system, designates an identification code of an abnormal output signal corresponding to the actuator not operating normally;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal designated by said designation input unit; and

a storage device which, if the input signal extracted by said input-signal extractor is from said detector, stores an identification code of this input signal.

46. The control apparatus equipped with a function for detecting a fault in a detector according to claim 45, wherein in a case where the extracted input signal is an auxiliary input signal and is controlled by the state of the output signal of the control apparatus, said input-signal extractor repeats extraction of the input signal that has influenced the logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal that controls the state of said extracted input signal.

47. The control apparatus equipped with a function for detecting a fault in a detector according to claim 46, further comprising a degree-of-priority calculating means which, in a case where a plurality of input signals have been extracted, calculates a degree of priority of each input signal;

said input-signal extractor ending extraction processing when the number of input signals stored in said storage device becomes larger than a predetermined prescribed number or when there are no longer any input signals to be extracted;

wherein when a plurality of input signals have been extracted, it is determined whether the input signals are from the detector in regular order starting from the input signal for which the degree of priority is calculated to be high by said degree-of-priority calculating means;

when one input signal has been extracted, it is determined whether this input signal is from the detector; and

if the extracted input signal is from the detector, said storage device stores an identification code of this input signal.

48. The control apparatus equipped with a function for detecting a fault in a detector according to claim 47, wherein said degree-of-priority calculating means calculates degree of priority by obtaining features of each extracted input signal and executing fuzzy reasoning based upon these features.

49. The control apparatus equipped with a function for detecting a fault in a detector according to claim 45, wherein said control apparatus is implemented by a programmable logic controller;

the state of said input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

50. The control apparatus equipped with a function for detecting a fault in a detector according to claim 45, wherein said control apparatus is implemented by a computer system;

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

51. A control apparatus, which is equipped with a function for detecting a fault in an actuator and a detector, for controlling a controlled system including one or two or more detectors and one or two or more actuators, said control apparatus comprising:

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a determining unit which, when there is an actuator not operating normally in said controlled system, determines that the actuator to which the output signal is to be applied is faulty in a case where the state of the output signal has not become normal even upon elapse of a prescribed time from establishment of a condition for generation of an output signal to be applied to the actuator;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to an abnormal output signal determined by said determining unit; and

a storage device which, if the input signal extracted by said input-signal extractor is from said detector, stores an identification code of this input signal.

52. The control apparatus equipped with a function for detecting a fault in an actuator and a detector according to claim 51, wherein in a case where the extracted input signal is an auxiliary input signal and is controlled by the state of the output signal of the control apparatus, said input-signal extractor repeats extraction of the input signal that has influenced the logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal that controls the state of said extracted input signal.

53. The control apparatus equipped with a function for detecting a fault in an actuator and a detector according to claim 52, further comprising a degree-of-priority calculating means which, in a case where a plurality of input signals have been extracted, calculates a degree of priority of each input signal;

said input-signal extractor ending extraction processing when the number of input signals stored in said storage device becomes larger than a predetermined prescribed number or when there are no longer any input signals to be extracted;

wherein when a plurality of input signals have been extracted, it is determined whether the input signals are from the detector in regular order starting from the input signal for which the degree of priority is calculated to be high by said degree-of-priority calculating means;

when one input signal has been extracted, it is determined whether this input signal is from the detector; and

if the extracted input signal is from the detector, said storage device stores an identification code of this input signal.

54. The control apparatus equipped with a function for detecting a fault in an actuator and a detector according to claim 53, wherein said degree-of-priority calculating means calculates degree of priority by obtaining features of each extracted input signal and executing fuzzy reasoning based upon these features.

55. The control apparatus equipped with a function for detecting a fault in an actuator and a detector according to claim 51, wherein said control apparatus is constituted by a programmable logic controller;

the state of said input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

56. The control apparatus equipped with a function for detecting a fault in an actuator and a detector according to claim 51, wherein said control apparatus is implemented by a computer system.

57. A control apparatus, which is equipped with a function for detecting a fault in an input signal, for controlling a controlled system including one or two or more detectors and one or two or more actuators, said control apparatus comprising:

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a designation input unit which, when there is an actuator not operating normally in said controlled system, designates an identification code of an abnormal output signal corresponding to the actuator not operating normally;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal designated by said designation input unit; and

a storage device for storing an identification code of the input signal extracted by said input-signal extractor.

58. The control apparatus equipped with a function for detecting a fault in an input signal according to claim 57, wherein in a case where the extracted input signal is an auxiliary input signal and is controlled by the state of the output signal of the control apparatus, said input-signal extractor repeats extraction of the input signal that has influenced the logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal that controls the state of said extracted input signal.

59. The control apparatus equipped with a function for detecting a fault in an input signal according to claim 58, further comprising a degree-of-priority calculating means which, in a case where a plurality of input signals have been extracted, calculates a degree of priority of each input signal;

said input-signal extractor ending extraction processing when the number of input signals stored in said storage device becomes larger than a predetermined prescribed number or when there are no longer any input signals to be extracted.

60. The control apparatus equipped with a function for detecting a fault in an input signal according to claim 59, wherein said degree-of-priority calculating means calculates degree of priority by obtaining features of each extracted input signal and executing fuzzy reasoning based upon these features.

61. The control apparatus equipped with a function for detecting a fault in a detector according to claim 57, wherein said control apparatus is constituted by a programmable logic controller;

the state of said input signal corresponds to the state of a contact of the programmable logic controller; and

the state of said output signal corresponds to the state of a relay of the programmable logic controller.

62. The control apparatus equipped with a function for detecting a fault in an input signal according to claim 57, wherein said control apparatus is implemented by a computer system.

63. A control method for detecting a fault in a detector, said control method controlling a controlled system including one or two or more detectors and one or two or more actuators, said control method comprising the steps of:

generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an auxiliary input signal;

when there is an actuator not operating normally in said controlled system, extracting, on the basis of a designated abnormal output signal corresponding to the actuator not operating normally, an input signal that has influenced said logical operation, which gave rise to this abnormal output signal; and

in a case whets said extracted input signal is from said detector, storing an identification code of this input signal in a storage device.

64. A control method for detecting a fault in an actuator and a detector, said control method controlling a controlled system including one or two or more detectors and one or two or more actuators, said control method comprising the steps of:

generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

when there is an actuator not operating normally in said controlled system, determining that the actuator to which the output signal is to be applied is faulty in a case where the state of the output signal has not become normal even upon elapse of a prescribed time from establishment of a condition for generation of an output signal to be applied to the actuator;

extracting an input signal that has influenced said logical operation, which gave rise to said determined abnormal output signal; and

in a case where said extracted input signal is from said detector, storing an identification code of this input signal in a storage device.

65. A control method for detecting a fault in an input signal, said control method controlling a controlled system including one or two or more detectors and one or two or more actuators, said control method comprising the steps of:

generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

.

when there is an actuator not operating normally in said controlled system, extracting, on the basis of a designated abnormal output signal corresponding to the actuator not operating normally, an input signal that has influenced said logical operation, which gave rise to this abnormal output signal; and

storing an identification code of said extracted input signal in a storage device.

66. A programmable logic controller, which is equipped with a function for detecting a fault in a detector, for controlling a controlled system including one or two or more detectors and one or two ore more actuators, said controller comprising:

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a designation input unit which, when there is an actuator not operating normally in said control led system, designates an identification code of an abnormal output signal corresponding to the actuator not operating normally;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal designated by said designation input unit; and

a storage device which, if the input signal extracted by said input-signal extractor is from said detector, stores an identification code of this input signal.

67. A computer system, which is equipped with a function for detecting a fault in a detector, for controlling a controlled system including one or two or more detectors and one or two or more actuators, said computer system comprising:

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a designation input unit which, when there is an actuator not operating normally in said controlled system, designates an identification code of an abnormal output signal corresponding to the actuator not operating normally;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal designated by said designation input unit; and

a storage device which, if the input signal extracted by said input-signal extractor is from said detector, stores an identification code of this input signal.

68. A programmable logic controller, which is equipped with a function for detecting a fault in an actuator and a detector, for controlling a controlled system including one or two or more detectors and one or two or more actuators, said controller comprising;

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a determining unit which, when there is an actuator not operating normally in said controlled system, determines that the actuator to which the output signal is to be applied is faulty in a case where the state of the output signal has not become normal even upon elapse of a prescribed time from establishment of a condition for generation of an output signal to be applied to the actuator;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to an abnormal output signal determined by said determining unit; and

a storage device which, if the input signal extracted by said input-signal extractor is from said detector, stores an identification code of this input signal.

69. A computer system, which is equipped with a function for detecting a fault in an actuator and a detector, for controlling a controlled system including one or two or more detectors and one or two or more actuators, said computer system comprising:

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a determining unit which, when there is an actuator not operating normally in said controlled system, determines that the actuator to which the output signal is to be applied is faulty in a case where the state of the output signal has not become normal even upon elapse of a prescribed time from establishment of a condition for generation of an output signal to be applied to the actuator;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to an abnormal output signal determined by said determining unit; and

a storage device which, if the input signal extracted by said input-signal extracting means is from said detector, stores an identification code of this input signal.

70. A programmable logic controller, which is equipped with a function for detecting a fault in an input signal, for controlling a controlled system including one or two or more detectors and one or two or more actuators, said controller comprising:

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a designation input unit which, when there is an actuator not operating normally in said controlled system, designates an identification code of an abnormal output signal corresponding to the actuator not operating normally;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to the abnormal output signal designated by said designation input unit; and

a storage device for storing an identification code of the input signal extracted by said input-signal extractor.

71. A computer system, which is equipped with a function for detecting a fault in an input signal, for controlling a controlled system including one or two or more detectors and one or two or more actuators, said computer system comprising:

an arithmetic-logic unit for generating an output signal to be applied to said actuator in accordance with predetermined logic in conformity with the state of an input signal from said detector and the state of an auxiliary input signal;

a designation input unit which, when there is an actuator not operating normally in said controlled system, designates an identification code of an abnormal output signal corresponding to the actuator not operating normally;

an input-signal extractor for extracting an input signal that has influenced a logical operation, performed by said arithmetic-logic unit, which gave rise to an abnormal output signal designated by said designation input unit; and

a storage device for storing an identification code of the input signal extracted by said input-signal extractor.