Method and system for controlling a multiple input/output process with minimum latency

• US 5,777,872 A
• Filed: 09/13/1996
• Issued: 07/07/1998
• Est. Priority Date: 09/13/1996
• Status: Expired due to Term

• Current Assignee: Honeywell-Measurex Corp. (Honeywell International Inc.)
• Original Assignee: Honeywell-Measurex Corp. (Honeywell International Inc.)
• Inventors: He, Xiaohua George
• Primary Examiner(s): RUGGIERO, JOSEPH F
• Application Number:
  US08/713,461
• Time in Patent Office: 662 Days
• Field of Search: 364/148, 364/149-151, 364/152, 364/157, 364/158, 364/164, 364/165, 364/176, 364/471.01, 364/471.02, 364/471.03, 318/561
• US Class Current: 700/29
• CPC Class Codes: G05B 11/32 with inputs from more than one sensing element; with outputs to more than one correcting element

Abstract

A control system regulates a controlled process. A first controller receives at least a first input variable and a second input variable and produces at least a first control variable and a second control variable. A delay unifier associated with the first controller introduces a first delay to one of the first and second control variables, the first delay being determined as a function of a second delay associated with another of the first and second control variables, and outputs first and second control variables with unified delay. A processor models effects of the controlled process. The processor receives the delayed first and second control variables output by the first controller and produces estimated process output variables. A second controller processes a difference between measured process output variables and the estimated process output variables to correct for disturbances. The processed difference is added to the delayed first and second control variables output by the first controller, and the sum is received by the processor and the process being controlled.

Claims

1. A control system for a process, comprising:

a first controller for receiving at least a first input variable and a second input variable and producing at least a first control variable and a second control variable, wherein said first controller introduces a first delay to one of the first and second control variables, the first delay being determined as a function of a second delay associated with another of the first and second control variables, and outputting first and second control variables with unified delay;

a processor for modelling effects of the process on the first and second control variables, said processor receiving the delayed first and second control variables output by said first controller, and producing estimated process output variables; and

a second controller for processing a difference between measured process output variables and the estimated process output variables to correct for disturbances, wherein the processed difference is added to the delayed first and second control variables output by said first controller, and the sum is received by said processor and the process being controlled.

2. The control system of claim 1, further comprising a filter means for filtering out particular frequencies of the difference between the measured process variables and the estimated process variables fed into said second controller.

3. The control system of claim 1, wherein said second controller corrects for disturbances introduced in the process being controlled.

4. The control system of claim 1, wherein the process is a sheetmaking process.

5. A method controlling a process, comprising the steps of:

receiving at least a first input variable and a second input variable;

producing at least a first control variable and a second control variable;

determining a first delay as a function of a second delay associated with one of the first and second control variables;

introducing the first delay to another of the first and second control variables to produce first and second control variables with unified delay;

measuring process output variables of the process;

modelling effects of the process on the first and second control variables in which the first delay has been introduced and producing estimated process output variables;

processing a difference between the measured process output variables and the estimated process output variables to correct for disturbances; and

adding the processed difference to said first and second control variables in which the first delay has been introduced, wherein said step of modelling is performed on the sum.

6. The method of claim 5, further comprising filtering out particular frequencies of the difference between the measured process output variables and the estimated process output variables before said step of processing.

7. The method of claim 5, wherein said step of processing corrects for disturbances introduced in the process being controlled.

8. The method of claim 5, wherein the process is a sheetmaking process.

9. A control system for a process, comprising:

a first controller for receiving at least a first input variable and a second input variable and producing at least a first control variable and a second control variable, said first controller unifying delay between the first control variable and the second control variable and outputting first and second control variables with unified delay;

a processor for modelling effects of the process on the delayed first and second control variables output by said first controller and producing estimated process output variables; and

a second controller for processing a mismatch between the estimated process output variables and measured process output variables to correct for disturbances, wherein the processed mismatch is added to the delayed first and second control variables, and the sum is received by said processor and the process being controlled.

10. The control system of claim 9, further comprising a filter means for filtering out particular frequencies of the mismatch between the estimated process output variables and the measured process output variables fed into said second controller.

11. The control system of claim 9, wherein said second controller corrects for disturbances introduced in the process being controlled.

12. The control system of claim 9, wherein the process is a sheetmaking process.

13. A method for controlling a process, comprising:

receiving at least a first input variable and a second input variable;

producing at least a first control variable and a second control variable;

unifying delay between the first control variable and the second control variable;

measuring process output variables of the process;

modelling effects of the process on the first and second control variables in which the delay has been unified and producing estimated process output variables;

processing a mismatch between the measured process output variables and the estimated process output variables to correct for disturbances; and

adding the processed mismatch to said first and second control variables in which the delay has been unified, wherein said step of modelling output is performed on the sum.

14. The method of claim 13, further comprising filtering out particular frequencies of the mismatch between the measured process output variables and the estimated process output variables.

15. The method of claim 13, wherein said step of processing corrects for disturbances in the process being controlled.

16. The method of claim 13, wherein the process is a sheetmaking process.