Single variable priority constraint fuzzy control system

• US 6,430,544 B1
• Filed: 08/11/1998
• Issued: 08/06/2002
• Est. Priority Date: 08/11/1998
• Status: Expired due to Term

• Current Assignee: Dynamic Energy Systems LLC
• Original Assignee: Ronald Childress
• Inventors: Childress, Ronald
• Primary Examiner(s): Davis, George B.
• Application Number:
  US09/132,480
• Time in Patent Office: 1,456 Days
• Field of Search: 706/1, 706/8, 706/4, 706/900, 706/903
• US Class Current: 706/1
• CPC Class Codes: G05B 13/0275 using fuzzy logic only
• CPC Class Codes: Y10S 706/90 Fuzzy logic
• CPC Class Codes: Y10S 706/903 Control

Abstract

A fuzzy logic controller system comprising a plurality of fuzzy logic controller units cascadably coupled to one another, each controller having a membership processor for receiving a single input signal corresponding to a sensed parameter from a controlled system and performing fuzzy inference operations based on the input signal for outputting an incremental output signal indicative of a requested change in a controlled output from a current level, a permissions processor for scaling the incremental output signal in response to a fulfillment signal from another controller, a processor responsive to the membership processor and to the permissions processor for providing a fulfillment signal to another controller indicative of a permissible range of freedom for scaling the incremental output signal of the another controller in the cascading sequence, an adder for summing each of the incremental output signals from the plurality of controllers and applying the sum to the controlled output for providing a correction to the current level of the controlled output, wherein the fulfillment signal output from the controller operates to constrain the incremental output signal and influence of subsequent downstream controllers.

Claims

1. A fuzzy logic controller system comprising:

a plurality of fuzzy logic controllers cascadably coupled to one another to form a sequence, each controller having;

membership processing means for receiving a separate input variable from a controlled system and performing fuzzy inference operations for outputting an incremental output signal according to associated membership functions and rules, said incremental output signal indicative of a request from each controller to change a controlled output from a current level; and

downstream fulfillment means responsive to said membership processing means and to at least one previous controller in said sequence of cascadably coupled controllers for providing a fulfillment signal indicative of a permissible range of freedom for scaling an incremental output signal of another one of said controllers in said cascading sequence, wherein said fulfillment signal operates to constrain the incremental output signal and influence of a subsequent downstream controller.

2. The control system according to claim 1, each said controller further comprising permission means responsive to said membership processing means and to an upstream controller for receiving a fulfillment signal from said upstream controller indicative of the degree of permission from said upstream controller to increase the incremental output for scaling said incremental output signal, wherein said permission means is coupled to said fulfillment means for each controller.

3. The control system according to claim 2, further comprising adding means responsive to an incremental output signal from each of said plurality of cascading fuzzy logic controllers for summing together each said incremental output signal and applying said sum to said controlled output for providing a correction to said current level of said controlled output.

4. The control system according to claim 3, wherein said membership processing means includes a processor having a plurality of said membership functions and rules associated with said separate input variable for providing a first signal indicative of a low range associated with a first membership and rule function, a second signal indicative of a normal range associated with a second membership and rule function, and a third signal indicative of a high range associated with a third membership and rule function.

5. The control system according to claim 4, wherein said membership processing means further comprises combining means for combining at least two of said first, second, and third signals to produce said incremental output signal for input to said permission means.

6. The control system according to claim 5, wherein said combining means comprises:

first multiplying means for multiplying said first signal with a first movement signal;

second multiplying means for multiplying said third signal with a second movement signal; and

adder means for adding said multiplied first and third signals to provide said incremental output signal,

wherein said first and second movement signals each have a magnitude and polarity opposite one another and indicative of a desired amount of change of said single input variable.

7. The control system according to claim 6, wherein said combining means further comprises gain means coupled between said adder means and said permission means for adjusting the magnitude of said incremental output signal.

8. The control system according to claim 4, wherein for each controller said fulfillment means comprises a multiplier for multiplying said second signal indicative of a normal range value with a fulfillment signal from an upstream controller to provide said fulfillment signal to a subsequent controller in said sequence.

9. The control system according to claim 3, further comprising bypass means associated with each said fuzzy logic controller for bypassing a particular fuzzy logic controller in said cascading sequence to eliminate said bypassed controller influence on said controlled output and on said downstream controllers.

10. The control system according to claim 1, wherein said fulfillment signal indicative of a permissible range of freedom for scaling said incremental output signal of another controller has a value ranging between 0 and 1.

11. The control system according to claim 1, wherein for a given one of said plurality of controllers, when said fulfillment signal for said given controller is unity, said given controller outputting said fulfillment signal and a downstream controller receiving said fulfillment signal have equal priority.

12. A fuzzy logic controller system comprising:

a plurality of fuzzy logic controller units cascadably coupled to one another to form a sequence, each controller unit having;

membership processing means for receiving a single input signal corresponding to a sensed parameter from a controlled system and performing fuzzy inference operations based on said input signal for outputting an incremental output signal indicative of a requested change in a controlled output from a current level,

permission means for scaling said incremental output signal in response to a fulfillment signal from another controller unit;

fulfillment means responsive to said membership processing means and to said permission means for providing a fulfillment signal to another downstream controller unit indicative of a permissible range of freedom for scaling an incremental output signal of said another downstream controller unit in said cascading sequence; and

summing means for summing each incremental output signal from said plurality of controller units and applying said sum to said controlled output for providing a correction to said current level of said controlled output;

wherein said fulfillment signal output from a particular controller unit operates to constrain the incremental output signal and influence of subsequent downstream controller units.

13. The system according to claim 12, wherein said membership processing means comprises a processor having a plurality of membership functions and rules associated with said single input signal and operable to output a plurality of membership value signals associated with said membership functions and rules according to a value associated with said single input signal.

14. The system according to claim 13, wherein said permission means comprises:

increase permission means for receiving one of said plurality of membership value signals and a fulfillment signal from an upstream controller indicative of a degree of permission to increase the incremental output signal and scaling said received membership value signal by said degree to provide a scaled membership value signal;

decrease permission means for receiving another of said plurality of membership value signals and a fulfillment signal from an upstream controller indicative of a degree of permission to decrease the incremental output signal and scaling said received another membership value signal by said degree to provide a scaled membership value signal; and

means for summing said scaled membership value signals from said increase and decrease permission means to provide said incremental output signal.

15. The system according to claim 14, wherein said membership processing means further comprises a first inverter for inverting one of said plurality of membership value signals, and a second inverter for inverting another of said plurality of membership value signals, and wherein said fulfillment means comprises:

increase fulfillment means coupled to said increase permission means and said first inverter for receiving a fulfillment signal from an upstream controller and said inverted membership signal for providing an increase fulfillment signal to a downstream controller indicative of the degree of permission in which to increase the incremental output signal of said downstream controller; and

decrease fulfillment means coupled to said decrease permission means and said second inverter for receiving a fulfillment signal from an upstream controller for providing a decrease fulfillment signal to a downstream controller indicative of the degree of permission in which to decrease the incremental output signal of said downstream controller.

16. The control system according to claim 15, wherein said increase and decrease fulfillment means associated with a riven one of said plurality of controller units operate independent of one another to permit said given controller unit to constrain an incremental output signal of a downstream controller unit in only one direction.

17. The control system according to claim 14, wherein said plurality of membership value signals comprise a first signal indicative of a low range associated with a first membership function of said single input signal, a second signal indicative of a normal range associated with a second membership function of said single input signal, and a third signal indicative of a high range associated with a third membership function of said single input signal.

18. The control system according to claim 12, wherein each said processor is operable according to said membership functions and rules in a first direct control mode such that a directional change in said single input signal resulting in a change in truth values of said membership functions operates to cause a corresponding directional change in said incremental output signal in a same direction as said directional change in said single input signal, and in a second reverse control mode such that a directional change in said single input signal resulting in a change in truth values of said membership functions operates to cause a corresponding directional change in said incremental output signal in a direction opposite that of said directional change in said single input signal.

19. The control system according to claim 12, further comprising external gain means coupled to said permission means for adjusting the magnitude of said incremental output signal based on an input variable from an external source.

20. The control system according to claim 12, wherein a first controller unit in said cascading sequence has priority over all other subsequent controllers when said fulfillment signal associated with said first controller has a value less than unity.

21. The system according to claim 12, wherein when a particular controller has an associated fulfillment signal equal to unity, said particular controller and a next downstream controller in said cascade sequence have equal priority.

22. A method for operating a fuzzy controller group control system, including a plurality of fuzzy controllers, for controlling an output parameter, comprising the steps of:

for each of said plurality of fuzzy controllers, receiving a separate single input variable from a controlled system and performing fuzzy inference operations for outputting from each of said plurality of fuzzy controllers a corresponding incremental output indicative of a requested change in said output parameter from a current level;

adaptively scaling said corresponding incremental output from each fuzzy controller of said plurality of fuzzy controllers by an at least one signal output from a previous controller indicative of a permissible range of freedom for varying said corresponding incremental output; and

summing each said adaptively scaled incremental output from each of said plurality of fuzzy controllers and applying the sum to said output parameter to obtain an updated output parameter.

23. The method according to claim 22, wherein said at least one signal output from a previous controller indicative of a permissible range of freedom for varying said incremental output further comprises an increase permission signal from said previous controller indicative of a permissible range of freedom for increasing said incremental output.

24. The method according to claim 23, wherein said at least one signal output from a previous controller indicative of a permissible range of freedom for varying said incremental output further comprises a decrease permission signal from said previous controller indicative of a permissible range of freedom for decreasing said incremental output.

25. The method according to claim 22, further comprising the step of coupling each of said plurality of fuzzy controllers in a cascading manner to form a sequence.

26. The method according to claim 25, further comprising the step of bypassing at least one of said plurality of fuzzy logic controllers in said cascaded sequence to eliminate said at least one bypassed controller from influence on subsequent downstream controllers and on said requested change in said output parameter.

27. A single variable fuzzy logic controller comprising:

membership processing means for receiving an analog input process signal comprising a single input variable indicative of a measured parameter from a controlled system and performing fuzzy inference operations for outputting an incremental output signal indicative of a requested change in a controlled output from a current level,

an input terminal for receiving a permission signal indicative of a permissible range of freedom for varying said incremental output signal;

scaling means for adaptively scaling said incremental output signal of said controller by said permission signal.

28. The single variable fuzzy logic controller according to claim 27, wherein said membership processing means comprises a processor having a plurality of membership functions and rules associated with said single input variable for providing a first signal indicative of a low range associated with a first membership and rule function, a second signal indicative of a normal range associated with a second membership and rule function, and a third signal indicative of a high range associated with a third membership and rule function.

29. The single variable fuzzy logic controller according to claim 28, further comprising a multiplier for scaling said second signal by said permission signal to provide an output fulfillment signal corresponding to a controlling factor associated with said controller.

30. The fuzzy logic controller according to claim 27, wherein said single variable fuzzy logic controller is coupled to another controller at said multiplier for providing said fulfillment signal to said another controller indicative of a level of control exercised by said controller over said another controller.

31. The fuzzy logic controller according to claim 30, wherein said single variable fuzzy logic controller is coupled at said input terminal to another controller for receiving said permission signal.

32. A single variable fuzzy logic controller comprising:

a membership processor for receiving an input variable indicative of a parameter from a controlled system and performing fuzzy inference operations thereon for outputting an incremental output signal indicative of a requested change in a controlled output from a current level;

an input terminal for receiving a control signal indicative of a permissible range of freedom for varying said incremental output signal; and

a processor for adaptively scaling said incremental output signal of said controller according to said control signal.

33. The fuzzy logic controller according to claim 32, further comprising a processor responsive to said control signal for providing an output control signal to a downstream controller for constraining variation of an incremental output signal output from said downstream controller.