Control arithmetic apparatus and method

• US 6,754,542 B1
• Filed: 10/18/2000
• Issued: 06/22/2004
• Est. Priority Date: 10/18/1999
• Status: Active Grant

• Current Assignee: Yamatake Corporation
• Original Assignee: Yamatake Corporation
• Inventors: Tanaka, Masato
• Primary Examiner(s): PATEL, RAMESH B
• Application Number:
  US09/691,828
• Time in Patent Office: 1,343 Days
• Field of Search: 700/28, 700/37, 700/40-45, 700/89, 700/52, 700/53, 700/73, 700/74, 700/34, 700/46, 714/6, 714/746, 714/751, 708/7, 708/505, 708/501, 708/523, 708/530
• US Class Current: 700/42
• CPC Class Codes: G05B 11/42 for obtaining a characteristic which is both proportional and time-dependent, e.g. P. I., P. I. D.
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 5/01 electric

Abstract

A control arithmetic device includes a subtracting section, disturbance application detecting section, error correction amount calculating section, error correction amount convergence calculating section, and control arithmetic section. The subtracting section calculates the error of a controlled variable on the basis of a controlled variable and set point for a controlled system. The disturbance application detecting section detects, in control cycles, on the basis of the error output whether a disturbance is applied. The error correction amount calculating section calculates an error correction amount on the basis of the magnitude of the error when application of a disturbance is detected. The error correction amount convergence calculating section performs a convergence operation. A control arithmetic method is also presented.

Claims

1. A control arithmetic apparatus comprising:

first calculation means for calculating an error of a controlled variable on the basis of a controlled variable and set point for a controlled system;

detection means for detecting, in control cycles, on the basis of the error output from said first calculation means whether a disturbance is applied;

second calculation means for calculating an error correction amount on the basis of a magnitude of the error output from said first calculation means when application of a disturbance is detected;

convergence operation means for performing convergence operation such that the error correction amount output from said error correction amount calculation means gradually converges to 0; and

control arithmetic means for calculating a manipulated variable on the basis of the error output from said first calculation means and an error correction amount after the convergence operation which is output from said convergence operation means, wherein overshoot suppression processing is performed without depending on an adjustment of a proportional plus integral plus derivation (PID) parameter.

2. An apparatus according to claim 1, wherein said first calculation means comprises subtraction means for calculating an error by subtracting a controlled variable of the controlled system from a set point.

3. An apparatus according to claim 1, wherein said disturbance application detection means detects application of a disturbance when an absolute value of the error output from said first calculation means increases.

4. An apparatus according to claim 3, wherein said disturbance application detection means detects application of a disturbance if Er>

0 and Er>

Er′

where Er is an error and Er′

is an error preceding one control cycle.

5. A apparatus according to claim 3, wherein said disturbance application detection means detects application of a disturbance if Er<

0 and Er<

Er′

where Er is an error and Er′

is an error preceding one control cycle.

6. An apparatus according to claim 1, wherein said second calculation means calculates an error correction amount by multiplying the error output from said first calculation means by a predetermined coefficient.

7. An apparatus according to claim 1, wherein said control arithmetic means performs one of PID (Proportional, Integrational and Differential) operation and IMC (Internal Model Control) operation.

8. An apparatus according to claim 1, wherein said apparatus further comprises;

controlled variable input means to which a controlled variable of a controlled system is input; and

set point input means to which a set point is input, and said first calculation means calculates an error of a controlled variable by using the controlled variable for the controlled system which is output from said controlled variable input means and the set point output from said set point input means.

9. An control arithmetic method comprising the steps of:

calculating an error of a controlled variable on the basis of a controlled variable and set point for a controlled system;

detecting, in control cycles, on the basis of the calculated error whether a disturbance is applied;

calculating an error correction amount on the basis of a magnitude of the calculated error when application of a disturbance is detected;

performing convergence operation to make the calculated error correction amount gradually converge to 0 according to a predetermined rule;

calculating a manipulated variable on the basis of the calculated error and an error correction amount after the convergence operation, and outputting the manipulated variable to the controlled system,

performing overshoot suppression processing without depending on an adjustment of a proportional plus integral plus derivation (PID) parameter.

10. A method according to claim 9, wherein the step of calculating the error comprises the step of calculating the error by subtracting the controlled variable of the controlled system from the set point.

11. A method according to claim 9, wherein the step of detecting the application of the disturbance comprises the step of detecting the application of the disturbance when an absolute value of the calculated error increases.

12. A method according to claim 11, wherein the step of detecting application of the disturbance comprises the step of detecting application of a disturbance if Er>

0 and Er>

Er′

where Er is an error and Er′

is an error preceding one control cycle.

13. A method according to claim 11, wherein the step of detecting application of the disturbance comprises the step of detecting application of a disturbance if Er<

0 and Er<

Er′

where Er is an error and Er′

is an error preceding one control cycle.

14. A method according to claim 9, wherein the step of calculating the error correction amount comprises the step of calculating an error correction amount by multiplying a calculated error by a predetermined coefficient.

15. A method according to claim 9, wherein the step of calculating the manipulated variable comprises the step of calculating a manipulated variable of performing one of PID (Proportional, Integrational and Differential) operation and IMC (Internal Model Control) operation.

16. A method according to claim 9, wherein the method further comprises the steps of:

inputting a controlled variable for a controlled system; and

inputting a set point, and the step of calculating the error comprises the step of calculating an error of a controlled variable by using the input controlled variable and input set point of the controlled system.