Fuzzy logic ladder diagram program for a machine or process controller

• US 5,285,376 A
• Filed: 10/24/1991
• Issued: 02/08/1994
• Est. Priority Date: 10/24/1991
• Status: Expired due to Term

• Current Assignee: Allen-Bradley Company (Rockwell Automation, Inc.)
• Original Assignee: Allen-Bradley Company (Rockwell Automation, Inc.)
• Inventors: Cieslak, Greggory, Dummermuth, Ernst, Struger, Odo J.
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): OAKES, BRIAN
• Application Number:
  US07/782,851
• Time in Patent Office: 838 Days
• Field of Search: 364/147, 364/146, 364/140, 395/3, 395/900, 395/12, 395/76
• US Class Current: 700/18
• CPC Class Codes: G05B 19/056 Programming the PLC
• CPC Class Codes: Y10S 706/90 Fuzzy logic

Abstract

Fuzzy logic programming is provided for machine and process controllers. New input and output instructions are devised for ladder diagram programming, as well as methods of downloading fuzzy logic instructions from a programming terminal to a programmable controller processor and methods for executing such instructions in the programmable controller processor.

Claims

1. A method of operating a programming computer to display a controller program based on fuzzy logic for downloading and execution in a programmable controller processor, the method comprising:

in response to a plurality of user inputs, displaying on the screen of the programming computer a ladder diagram representing a programmable controller ladder program based on fuzzy logic, wherein the displaying step further comprises

a) displaying fuzzy logic program input instructions with an input variable related to data in a programmable controller data table, an input membership function and an actual value representing evaluation of the input data with respect to a respective input membership function;

b) displaying fuzzy logic program output instructions with an output variable related to data in a programmable controller data table, an output membership function and an actual value representing a contribution of a respective output membership function to a resulting output;

c) displaying portions of rungs representing control rules for associating input instructions with each other and for associating input instructions with a related output instruction; and

d) displaying links between parallel rung branches representing a rule for relating the contributions of the respective output membership functions in parallel rung branches to an individual result; and

translating the displayed ladder diagram based on fuzzy logic into first and second portions, the first portion comprising a set of instruction codes to be executed by the programmable controller and the second portion comprising knowledge base data organized in a plurality of tables for access during execution of the instruction codes in the programmable controller.

2. The method of claim 1, further comprising the step of storing microprocessor-level instructions in programmable controller including:

a) a plurality of instructions for executing input and output membership functions;

b) a plurality of inference instructions for applying control rules for associating input instructions with each other and for associating input instructions with a related output instruction; and

c) a plurality of defuzzification instructions for reducing the plurality of program outputs to a single resulting output; and

downloading the set of knowledge base data organized in a plurality of tables and the set of instruction codes for invoking the microprocessor-level instructions stored in the programmable controller.

3. The method of claim 1, wherein the displaying of rungs with a plurality of input instructions displays a fuzzy logic "AND" function between the plurality of input instructions.

4. The method of claim 1, wherein the displaying of links between parallel rung branches displays a fuzzy logic "OR" function.

5. The method of claim 1, wherein the displaying of fuzzy logic input instructions further comprises displaying a symbol "/F " distinguishing the fuzzy logic input instructions from other ladder diagram instructions, and wherein the displaying of the fuzzy logic output instructions further comprises displaying the symbol " D/" for defuzzification.

6. The method of claim 1, further comprising the step of identifying the input variables and membership functions by alphanumeric labels.

7. The method of claim 1, wherein

the translating step further comprises compiling the ladder diagram program to generate a lop program in a source code in another programming language;

and

compiling the source code into an executable code for a microprocessor in the programmable controller processor.

8. The method of claim 7, wherein the step of compiling the ladder diagram into the source code further comprises compiling the ladder diagram into instructions in the C programming language.

9. A method of operating a programming computer to display a controllable program based on fuzzy logic for downloading and execution in a programmable controller processor, the method comprising:

in response to a plurality of user inputs, displaying on the screen of the programming computer a ladder diagram graphical display representing a programmable controller program based on fuzzy logic, wherein the displaying step further comprises

a) displaying fuzzy logic program input instructions with an input variable related to data in a programmable controller data table, an input membership function and an actual value representing evaluation of the input data with respect to a respective input membership function;

b) displaying fuzzy logic program output instructions with an output variable related to data in a programmable controller data table, an output membership function and an actual value representing a contribution of a respective output membership function to a resulting output;

c) displaying portions of rungs representing control rules for associating input instructions with each other and for associating input instructions with a related output instruction; and

d) displaying links between parallel rung branches representing control rules for relating the contributions of the respective output membership functions in parallel rung branches to an individual result; and

compiling the displayed program based on fuzzy logic into first and second portions, the first portion comprising a loop program for execution in the programmable controller and the second portion comprising knowledge base data organized in a plurality of tables for access during execution of the loop program.

10. The method of claim 9, further comprising

the step of downloading the loop program and the knowledge base data to a programmable controller processor;

and

further comprising the step of executing the loop program in the programmable controller to access the knowledge base data and carry out the ladder diagram program based on fuzzy logic.

11. The method of claim 9, further comprising

the step of programming the programmable controller processor with an instruction to initiate execution of the loop program and with an instruction to return from the loop program upon completion of the execution of the ladder diagram program based on fuzzy logic;

and

further comprising the step of executing instruction to initiate execution of the loop program during execution of a ladder diagram program based on Boolean logic.

12. A method of entering a controller program based on fuzzy logic for downloading and execution in a programmable controller processor, the method comprising:

in response to a plurality of user inputs, displaying on the screen of the programming computer a programmable controller program based on fuzzy logic, wherein the displaying step further comprises

a) in response to user inputs, displaying a plurality of propositions, membership functions and input data variables and output data variables for executing fuzzy logic operations; and

b) in response to user inputs, displaying a plurality of inference instructions to generate a plurality of program outputs;

storing a set of instructions for execution in the programmable controller to evaluate membership functions, to apply inference instructions and to generate an individual output from a plurality of program outputs;

translating the displayed program based on fuzzy logic to knowledge base data organized in a plurality of tables for access during execution of the set of instructions in the programmable controller; and

storing the set of instructions and the knowledge base data for execution in the programmable controller.

13. The method of claim 12, wherein the displaying step further comprises displaying the programmable controller program based on fuzzy logic as a ladder diagram program.

14. The method of claim 12, wherein the storing step further comprises downloading a first portion of the knowledge base data from a first programming computer to a programmable controller, and downloading a second portion of the knowledge based data and the set of instructions from a second programming computer to the programmable controller.

15. A method of entering a controller program based on fuzzy logic for a programmable controller that controls outputs in response to inputs on a controlled system, the method comprising:

in response to a plurality of user inputs to a programming computer, displaying on the screen of the programming computer a ladder diagram graphical display representing a programmable controller program based on fuzzy logic, wherein the displaying step further comprises

a) displaying a plurality of propositions, membership functions and input data variables for executing fuzzy logic operations;

b) displaying a plurality of inference instructions to generate a plurality of program outputs; and

c) displaying a plurality of defuzzification instructions for reducing the plurality of program outputs to a single resulting output; and

translating the programmable controller program based on fuzzy logic into first and second portions, the first portion comprising a coded program and the second portion comprising knowledge base tables which are executable by a microprocessor within a programmable controller processor.

16. The method of claim 15, further comprising the step of downloading the coded program and knowledge base tables to a programmable controller.

17. The method of claim 16, further comprising the step of programming the programmable controller with an instruction to invoke and execute the translated programmable controller program based on fuzzy logic, and with an instruction to return from execution of the coded program based on fuzzy logic to execute other ladder diagram instructions.