Control method and apparatus using two neural networks

• US 5,566,275 A
• Filed: 02/18/1994
• Issued: 10/15/1996
• Est. Priority Date: 08/14/1991
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kano, Makoto
• Primary Examiner(s): Downs, Robert W.
• Assistant Examiner(s): Katbab, A.
• Application Number:
  US08/199,014
• Time in Patent Office: 970 Days
• Field of Search: 395/96, 395/21, 395/22, 395/81, 395/9, 395/80, 395/84, 395/23, 382/153, 382/157
• US Class Current: 700/246
• CPC Class Codes: B25J 9/161 Hardware, e.g. neural networks, fuzzy logic, interfaces, processor

Abstract

A control method of controlling a controlled system according to the invention comprises the first step of inputting a current and future target controlled variable to a first neural network model which performs learning using a past target controlled variable for the controlled system as an input signal and a past manipulated variable as a teacher signal, thereby obtaining a current virtual manipulated variable, the second step of causing a second neural network model, which have learnt to predict a behavior of the controlled system, to receive the virtual manipulated variable obtained in the first step and a controlled variable obtained from the controlled system at a current time, thereby obtaining a predicted controlled variable, the third step of obtaining an error of the predicted controlled variable obtained in the second step with respect to the target controlled variable, the fourth step of obtaining a correction amount for the virtual manipulated variable in accordance with a back propagation calculation of the second neural network model, using the error obtained in the third step, thereby correcting the virtual manipulated variable with the correction amount, and the fifth step of outputting the virtual manipulated variable corrected in the fourth step to the controlled system.

Claims

1. A control method of controlling a controlled system, comprising:

the first step of inputting current and future target controlled variables to a first neural network model and causing the first neural network model to execute a forward calculation to output a virtual manipulated variable initial value;

the second step of causing a second neural network model to receive the virtual manipulated variable initial value obtained in the first step as a virtual manipulated variable and a controlled variable obtained from said controlled system at a current time, and causing the second neural network model to execute a forward calculation to output a predicted controlled variable;

the third step of obtaining an error of the predicted controlled variable obtained in the second step with respect to the future target controlled variable;

the fourth step of obtaining a correction amount for the virtual manipulated variable in accordance with a back propagation calculation of said second neural network model, using the error obtained in the third step, thereby correcting the virtual manipulated variable in accordance with the correction amount;

the fifth step of outputting the virtual manipulated variable corrected in the fourth step to the controlled system as a manipulated variable; and

the sixth step of causing the first neural network model to perform learning in an error back propagation learning method, using as a teacher signal the virtual manipulated variable output to the controlled system.

2. A method according to claim 1, wherein the third step includes the step of obtaining an error of the predicted controlled variable with respect to the future target controlled variable on the basis of at least one of a predicted controlled variable after one sampling period and a predicted controlled variable after two sampling periods.

3. A method according to claim 1, wherein the fifth step includes the step of outputting the corrected virtual manipulated variable to the controlled system after the second to fourth steps are repeated by a predetermined number of times.

4. A method according to claim 1, wherein the fifth step includes the step of outputting the corrected virtual manipulated variable to said controlled system after the second to fourth steps are repeated until the error of the predicted controlled variable with respect to the future target controlled variable reaches not more than a predetermined value.

5. A control method of controlling a controlled system, comprising:

the first step of providing a second neural network model having learnt to predict a behavior of the controlled system;

the second step of inputting current and future target controlled variables to a first neural network model and causing the first neural network model to execute a forward calculation to output a virtual manipulated variable initial value;

the third step of causing the second neural network model to receive the virtual manipulated variable initial value obtained in the first step as a virtual manipulated variable and a controlled variable obtained from said controlled system at a current time, and causing the second neural network model to execute a forward calculation to output a predicted controlled variable;

the fourth step of obtaining an error of the predicted controlled variable obtained in the third step with respect to the future target controlled variable;

the fifth step of obtaining a correction amount for the virtual manipulated variable in accordance with a back propagation calculation of said second neural network model, using the error obtained in the fourth step, thereby correcting the virtual manipulated variable with the correction amount;

the sixth step of outputting the virtual manipulated variable corrected in the fifth step to the controlled system as a manipulated variable; and

the seventh step of causing the first neural network model to perform learning in an error back propagation learning method, using as a teacher signal the virtual manipulated variable output to the controlled system.

6. A method according to claim 5, wherein the fourth step includes the step of obtaining an error of the predicted controlled variable with respect to the future target controlled variable on the basis of at least one of a predicted controlled variable after one sampling period and a predicted controlled variable after two sampling periods.

7. A method according to claim 5, wherein the sixth step includes the step of outputting the corrected virtual manipulated variable to the controlled system after the second to fifth steps are repeated by a predetermined number of times.

8. A method according to claim 5, wherein the sixth step includes the step of outputting the corrected virtual manipulated variable to said controlled system after the second to fifth steps are repeated until the error of the predicted controlled variable with respect to the future target controlled variable reaches not more than a predetermined value.

9. A control apparatus for controlling a controlled system, comprising:

a first neural network model for receiving current and future target controlled variables to obtain a current virtual manipulated variable initial value;

a second neural network model for receiving a current controlled variable obtained from the controlled system and a virtual manipulated variable whose initial value is the virtual manipulated variable initial value obtained from the first neural network model, for outputting a predicted controlled variable, and for calculating a correction amount for the virtual manipulated variable by executing an error back propagation calculation on the basis of an error between the predicted controlled variable and the future target controlled variable; and

means for correcting the virtual manipulated variable using the correction amount and the virtual manipulated variable and outputting the corrected virtual manipulated variable to the controlled system.

10. An apparatus according to claim 9, further comprising a subtracter for subtracting the predicted controlled variable obtained in said second neural network model from the future target controlled variable and outputting a difference to said second neural network model.

11. An apparatus according to claim 9, further comprising:

an integrator for accumulating the virtual manipulated variable and the correction amount;

a first switch for establishing connection to the first neural network model so as to receive the virtual manipulated variable initial value output from the first neural network model as an initial value of the virtual manipulated variable, and then establishing connection to the second neural network model so as to receive the virtual manipulated variable correction amount computed by the second neural network model; and

a second switch for supplying an output from said integrator to the controlled system under a predetermined condition.

12. An apparatus according to claim 9, wherein said first neural network model calculates a correction amount of a coupling weight value by performing a learning calculation which uses the manipulated variable as a teacher signal after the manipulated variable is supplied to the controlled system at each sampling time, and corrects the coupling weight value after completion of a sequence of control operations.

13. An apparatus according to claim 9, wherein said second neural network model has been previously trained to predict a behavior of the controlled system.

14. An apparatus according to claim 9, wherein said second neural network model includes:

means for receiving the virtual manipulated variable and the current controlled variable to obtain a predicted controlled variable;

means for obtaining an error of the predicted controlled variable with respect to the future target controlled variable; and

means for obtaining a correction amount for the virtual manipulated variable using the error.

15. An apparatus according to claim 14, wherein said means of obtaining an error includes means for obtaining an error of the predicted controlled variable with respect to the future target controlled variable on the basis of at least one of a predicted controlled variable after one sampling period and a predicted controlled variable after two sampling periods.

16. An apparatus according to claim 14, wherein said second neural network model included means for outputting the virtual manipulated variable to the controlled system when the error reaches not more than a predetermined value.