Process control system with action logging

• US 4,907,167 A
• Filed: 09/30/1987
• Issued: 03/06/1990
• Est. Priority Date: 09/30/1987
• Status: Expired due to Term

• Current Assignee: Pavilion Technologies Incorporated (Rockwell Automation, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Skeirik, Richard D.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Black, Thomas G.
• Application Number:
  US07/103,118
• Time in Patent Office: 888 Days
• Field of Search: 364/496, 364/513, 364/131, 364/132, 364/148, 364/300, 364/550, 364/138-139
• US Class Current: 700/10
• CPC Class Codes: G05B 13/028 using expert systems only
• CPC Class Codes: G06N 5/04 Inference or reasoning models
• CPC Class Codes: Y10S 706/906 Process plant
• CPC Class Codes: Y10S 706/914 Process plant

Abstract

An integrated system for process control in which a process supervisor procedure defines parameters for one or more controller systems (or control procedures). The supervisor procedure changes control parameters only in discrete changes, and the decision to act is sufficiently constrained that every change must be a significant change. Every change is logged (or otherwise reported out to human experts). Since every change is significant, the history of changes will provide a meaningful record which can be reviewed by human experts.

Claims

1. A computer-based method for operating a substantially continuous process, comprising the steps of:

(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuators connected to change conditions in the process;

(2) controlling one or more of said actuators with a process controller in accordance with signals received from said sensors and in accordance with control parameters, said control parameters indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action; and

(3) repeatedly running a process supervisor procedure for selectively defining one or more of said control parameters for said process controller;

(4) wherein, for each of said control parameters, said process supervisor procedure is constrained not to make changes to said control parameters unless the indicia for action exceed said respective threshold; and

(5) wherein said process supervisor procedure reports every instance where it changes a control parameter.

2. The method of claim 1, wherein said process controller of step (2) uses a cycling step, and said process supervisor procedure of step (3) uses a cycling step.

3. The method of claim 1, wherein said process supervisor procedure uses a cycling step, and said process controller of step (2) operates in substantially real-time.

4. The method of claim 1, wherein said process supervisor procedure of step (3) comprises the step of being implemented using a computer running one or more programs, including a cycling process which repeatedly samples a plurality of signals corresponding t inputs, forms inferences from said inputs according to a stored knowledge base, and provides outputs in accordance with said inferences, and then goes into a dormant state having a duration limited by timing;

wherein said duration of said dormant state is sufficiently large that said process does not on average occupy more than 50% of the available CPU time of the computer;

and wherein said duration of said dormant state is selected to be sufficiently short that process fluctuations cannot diverge to an out-of-control situation during the periods when said process is dormant.

5. The method of claim 1, wherein said process supervisor procedure of step (3) comprises the step of defining parameters including parameters for a feedback control relation including a deadband on said control parameters.

6. The method of claim 1, wherein said process supervisor procedure of step (3) comprises the step of having a maximum iteration period significantly longer than the maximum iteration period of said process controller of step (2).

7. The method of claim 1, wherein said process controller of step (2) uses analog logic for controlling.

8. The method of claim 1, wherein said step of repeatedly running a process supervisor procedure comprises the step of running said process supervisor procedure using a cycling step.

9. The method of claim 1, wherein said control parameters of step (2) comprises the step of including goals of said process controller.

11. The method of claim 1, wherein said respective thresholds on said indicia for action of step (2) comprise the step of being different for at least some of said control parameters.

12. The method of claim 1, wherein said process controller of step (2) and said process supervisor procedure of step (3) comprise processes running on the safe computer system.

13. The method of claim 1, wherein said process controller of step (2) and said process supervisor procedure of step (3) are both respective parts of the same software system.

10. The method of claim I, wherein said respective threshold on said indicia for action of step (2) comprise the step of being dependent on the particular action in prospect.

14. A computer-based method for operating a substantially continuous process, comprising the steps of:

(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuator connected to change conditions in the process;

(2) controlling one or more of said actuators with a process controller in accordance with signals received from said sensors and in accordance with control parameters; and

(3) repeatedly running a process supervisor procedure for selectively defining one or more of said control parameters for said process controller;

(4) wherein, for each of said control parameters, said process supervisor procedure is constrained not to make changes to said control parameters unless the amount of the change would exceed a certain threshold.

15. The method of claim 14, wherein said process supervisor procedure of step (3) uses a cycling step, and said process controller of step (2) operates in substantially real-time.

16. The method of claim 14, wherein said process supervisor procedure of step (3) comprises the step of implementing a feedback control relation including a deadband on at least some of said control parameters.

17. The method of claim 14, wherein said process supervisor procedure of step (3) comprises the step of having a maximum iteration period significantly longer than the maximum iteration period of said process controller of step (2).

18. The method of claim 14, wherein said process controller uses analog logic for controlling.

19. The method of claim 14, wherein said control parameters of step (2) comprise the step of including goals of said process controller.

20. The method of claim 14, wherein said certain thresholds of step (2) comprise the step of being different for at least some of said control parameters.

21. The method of claim 14, wherein said process controller of step (2) and said process supervisor procedure of step (3) comprise processes running on the same computer system.

22. The method of claim 14, wherein said process controller of step (2) and said process supervisor procedure of step (3) are both respective parts of the same software system.

23. A computer-based method for operating a substantially continuous process, comprising the steps of:

(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuators connected to change conditions in the process;

(2) controlling one or more of said actuators with a process controller in accordance with signals received form said sensors and in accordance with control parameters, said control parameters indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action; and

(3) repeatedly running a process supervisor procedure for selectively defining one or more of said control parameters for said process controller;

(4) wherein, for each of said control parameters, said process supervisor procedure is constrained not to make changes to said control parameters unless the indicia for action exceed said respective threshold.

24. The method of claim 23, wherein, for each of said control parameters, said process supervisor procedure of step (3) comprises the step of being constrained not to make changes to said control parameters unless the amount of the change would exceed said respective threshold;

and wherein said process supervisor procedure reports every instance where it changes a control parameter.

25. The method of claim 23, wherein, for each of said control parameters, said process supervisor procedure of step (3) comprises the step of being constrained not to make changes to said control parameters unless the amount of the change would exceed said respective threshold.

26. The method of claim 23, wherein said process supervisor procedure of step (3) comprises the step of implementing at least one feedback control relation including a deadband on at least some of said control parameters.

27. The method of claim 23, wherein said process supervisor procedure of step (3) comprises the step of having a maximum iteration period significantly longer than the maximum iteration period of said process controller of step (2).

28. The method of claim 23, wherein said process controller of step (2) uses analog logic for controlling.

29. The method of claim 23, wherein said control parameters of step (2) comprise the step of including goals of said process controller.

30. The method of claim 23, wherein said respective thresholds on said indicia for action of step (2) comprise the step of being different for at least some of said control parameters.

31. The method of claim 23, wherein said process controller of step (2) and said process supervisor procedure of step (3) comprise processes running on the same computer system.

32. The method of claim 23, wherein said process controller of step (2) and said process supervisor procedure of step (3) are both respective part of the same software system.

33. A computer-based method for operating a substantially continuous process, comprising the steps of:

(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuators connected to change conditions in the process;

(2) controlling one or more of said actuators in accordance with signals received from said sensors and in accordance with control parameters;

(3) repeatedly running a process supervisor procedure for selectively defining one or more of said control parameters; and

(4) wherein at least some of said actuators are controlled in a feedforward relation to respective measured variables, and

wherein said feedforward relation includes a deadband.

34. The method of claim 33, wherein said process supervisor procedure of step (3) uses a cycling step, and said step (2) operates in substantially real-time.

35. The method of claim 33, wherein said process supervisor procedure of step (3) implements at least one feedback control relation including a deadband on at least some of said control parameters.

36. The method of claim 33, wherein said process supervisor procedure of step (3) has a maximum iteration period significantly longer than the maximum iteration period of said step (2) for controlling.

37. The method of claim 33, wherein said step (2) uses analog logic for controlling.

38. The method of claim 33, wherein said control parameters comprise the step of indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action, wherein said respective thresholds on said indicia for action comprise the step of being different for at least some of said control parameters.

39. The method of claim 33, wherein said respective feedforward relation of step (4) comprises the step of including a deadband applied to a measured variable.

40. The method of claim 33, wherein said step (2) for controlling and said process supervisor procedure of step (3) comprise processes running on the same computer system.

41. The method of claim 33, wherein said step (2) for controlling and said process supervisor procedure of step (3) are both respective parts of the same software system.

42. A computer-based method for operating a substantially continuous process, comprising the steps of:

(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuators connected to change conditions in the process; and

(2) controlling one or more of said actuators in accordance with signals received from said sensors;

(3) wherein at least some of said actuators are controlled in a feedback relation with respective corresponding measured variables,

and said feedback relation includes the use of statistical filtering, and/or a deadband; and

(4) wherein at least some of said actuators are controlled in a feedforward relation to respective measured variables,

wherein said feedforward relation includes a deadband.

43. The method of claim 42, further comprising a process supervisor procedure step implementing at least one feedback control relation including a deadband on at least some of said control parameters.

44. The method of claim 42, further comprising a process supervisor procedure step having a maximum iteration period significantly longer than the maximum iteration period of said step (2) for controlling.

45. The method of claim 42, wherein said step (2) uses analog logic for controlling.

46. The method of claim 42, wherein said step (2) further comprises the step of using said control parameters comprise the step of indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action, wherein said respective thresholds on said indicia for action comprise the step of being different for at least some of said control parameters.

47. The method of claim 42, further comprising process supervisor procedure step, wherein said step (2) or controlling and said process supervisor procedure step comprise processes running on the same computer system.

48. The method of claim 42, further comprising a process supervisor procedure step, wherein said step (2) for controlling and said process supervisor procedure step are both respective parts of the same software system.

49. A computer-based process control system, comprising:

(a) one or more sensors connected to sense conditions in materials being processed, and one or more actuators connected to change conditions in the process;

(b) a plurality of process controllers, each connected to control one or more of said actuators in accordance with signals received from said sensors and in accordance with respective control parameters; and

(c) a process supervisor means for selectively defining one or more of said control parameters for said process controllers;

(d) wherein, for each of said control parameters, said process supervisor means is constrained not to make changes to said control parameters unless the amount of the change would exceed a certain threshold; and

(e) wherein said process supervisor means reports every instance where it changes a control parameter.

50. The system of claim 49, wherein said process supervisor means reports said control parameter change instances by means including voice messaging.

51. The system of claim 49, wherein said process supervisor means implements at least one feedback control relation including a deadband on at least some of said control parameters.

52. The system of claim 49, wherein said process supervisor means of element (c) has a maximum iteration period significantly longer than the maximum iteration period of said process controller of element (b).

53. The system of claim 49, wherein at least one said process controller of eleven (b) is an analog controller.

54. The system of claim 49, wherein one or more of said control parameters of element (b) goals of said process controller.

55. The system of claim 49, wherein said certain thresholds of element (d) are different for at least some of said control parameters of element (b).

56. The system of claim 49, wherein said process controller of element (b) and said process supervisor means of element (c) comprise processes running on the same computer system.

57. The system of claim 49, wherein said process controller of element (b) and said process supervisor means of element (c) are both respective parts of the same software system.

58. A computer-based process control system, comprising:

(a) one or more sensors connected to sense conditions in materials being processed, and one or more actuators connected to change conditions in the process;

(b) a plurality of process controllers, each connected to control one or more of said actuators in accordance with signals received from said sensors and in accordance with respective control parameters, said control parameters indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action; and

(c) a process supervisor means for selectively defining one or more of said control parameters for said process controllers;

(d) wherein, for substantially all of said control parameters said process supervisor means is constrained not to make changes to said control parameters unless the indicia for action exceed said respective threshold; and

(e) wherein said process supervisor means reports every instance where it changes a control parameter.

59. The system of claim 58, wherein said process supervisor means of element (c) has a maximum iteration period significantly longer than the maximum iteration period of said process controller of element (b).

60. The system of claim 58, wherein at least one said process controller of element (b) is an analog controller.

61. The system of claim 58, wherein said respective thresholds on said indicia for action of element (b) are different for at least some of said control parameters of element (b).