SIMPLIFIED PROCEDURE FOR TUNING PID CONTROLLERS

• US 3,826,887 A
• Filed: 12/29/1971
• Issued: 07/30/1974
• Est. Priority Date: 12/29/1971
• Status: Expired due to Term

• Current Assignee: Applied Automation, Inc. (Massman Automation Designs LLC)
• Original Assignee: Troy J. Pemberton
• Inventors: Pemberton, Troy J.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Bell, F. E.
• Application Number:
  US05/213,699
• Time in Patent Office: 944 Days
• Field of Search: 219/497,499,501 318/609,610,621
• US Class Current: 219/497
• CPC Class Codes: G05B 6/02 electric

Abstract

Simplified procedures for tuning a PID controller are disclosed wherein variable circuit elements in the reset and rate networks are mechanically ganged together to permit simultaneous and proportionate control of the circuit parameters in those two networks.

Claims

1. A controller apparatus for use in a control system and operative to regulate the value of a controlled variable in said system and comprising:

signal generation means for generating a controller output signal related to the difference between the value of said controlled variable and a set point value of said controlled variable;

reset means coupled to said signal generation means for altering said controller output signal in response to a time integral of said difference between the value of said controlled variable and the set point value of said controlled variable;

reset adjustment tuning means for altering the integration constant of said reset means;

rate means coupled to said signal generation means for altering said controller output signal in response to a time derivative of said difference between the value of said controlled variable and the set point value of said controlled variable;

rate adjustment tuning means for altering the differentiation constant of said rate means; and

ganging means for coupling said reset adjustment tuning means and said rate adjustment tuning means and providing simultaneous alteration of said reset means integration constant and said rate means differentiation constant.

2. The controller apparatus of claim 1 wherein said ganging means further provides for simultaneous alteration of said integration and differentiation constants in proportionate amounts.

3. A controller apparatus for use in a control system and operative to regulate a controlled variable in said system and comprising:

signal generation means for generating a controller output signal related to the difference between the value of said controlled variable and a set point value of said controlled variable;

reset means coupled to said signal generation means for improving the steady state error characteristics of said control system;

reset adjustment tuning means coupled to said reset means for altering the response characteristics of said reset means;

rate means coupled to said signal generation means for improving the transient response of said control system;

rate adjustment tuning means coupled to said rate means for altering the response characteristics of said rate means; and

ganging means coupling said reset adjustment tuning means and said rate adjustment tuning means for simultaneously altering the response characteristics of said reset means and said rate means.

4. An electronic controller apparatus for use in a control system and operative to regulate a controlled variable in said system and comprising:

amplifier means for receiving an error signal related to the difference between the value of said controlled variable and a setpoint value of said controlled variable and generating a controller output signal in response to said error signal;

reset circuit means coupled to said amplifier means for generating a signal related to a time integral of said error signal;

reset adjustment tuning means for altering a time constant of said reset circuit means;

rate circuit means coupled to said amplifier means for generating a signal related to a time derivative of said error signal;

rate adjustment tuning means for altering a time constant of said rate circuit means;

coupling means for coupling said reset adjustment tuning means to said rate adjustment Tuning means so that said time constants of said reset circuit means and said rate circuit means are altered simultaneously.

5. The controller apparatus of claim 4 wherein said coupling means comprises ganging means mechanically coupling said reset adjustment tuning means and said rate adjustment tuning means so that said time constants of said reset circuit means and said rate circuit means are simultaneously altered in proportionate amounts.

6. An electronic PID controller apparatus for use in a control system and operative to regulate a controlled variable in said system and comprising:

amplifier means for receiving an error signal related to the difference between the value of said controlled variable and generating a controller output signal in response to said error signal;

reset circuit means coupled to said amplifier means for altering said controller output signal in response to a time integral of said error signal and comprising a first resistive impedance element and a first reactive impedance element;

reset adjustment tuning means coupled to said reset circuit means for altering the relative circuit values of said first impedance elements;

rate circuit means coupled to said amplifier means for altering said controller output signal in response to a time derivative of said error signal and comprising a second resistive impedance element and a second reactive impedance element;

rate adjustment tuning means coupled to said rate circuit means for altering the relative circuit values of said second impedance elements; and

coupling means between said reset adjustment tuning means and said rate adjustment tuning means and providing for the simultaneous alteration of the relative values of said first and second impedance elements by proportionate amounts.

7. The electronic PID controller apparatus of claim 6 wherein said first and second resistive impedance elements are first and second resistors, said first and second reactive impedance elements are first and second capacitors, said reset and rate adjustment tuning means are adjustable taps on said first and second resistors, and said coupling means comprises apparatus for mechanically ganging said first and second adjustable taps together.

8. The electronic PID controller apparatus of claim 7 further comprising means for adjusting the relative values of said first and second reactive impedance devices.

9. The method of tuning the reset and rate parameters of a PID controller in a control system comprising the steps of:

placing said reset and rate parameters in a fixed ratio;

tuning one of said parameters to improve the operation of said control system; and

tuning the other of said parameters so as to maintain said reset and rate parameters in said fixed ratio.

10. The method of tuning the reset, rate and gain parameters of a PID controller in a control system comprising the steps of:

placing said reset and rate parameters in a fixed ratio;

tuning said reset parameter to optimize the operation of said control system;

tuning said rate parameter so as to maintain said reset and rate parameters in said fixed relationship; and

tuning said gain parameter to optimize the operation of said control system.

11. The method of tuning the reset and rate parameters of a PID controller in a control system to optimize the operation of said control system in accord with a predetermined definition of optimization, said definition yielding a fixed relationship between said reset and rate parameters, comprising the steps of:

setting said reset and rate parameters to said fixed relationship;

tuning said reset parameter to optimize the operation of said control system; and

tuning said rate parameter so as to maintain said reset and rate parameters in said fixed relationship.

12. The controller apparatus of claim 2 further comprising proportionality adjustment means for altering the ratio of the rate time to the reset time.

13. The controller apparatus of claim 5 further comprising proportionality adjustment means for altering the ratio of the rate time to the reset time.

14. The controller apparatus of claim 5 wherein the ratio of the rate time to the reset time is 0.25.

15. The controller apparatus of claim 13 wherein said proportionality adjustment means alters the ratio of the rate time to the reset time over a plurality of values within the range of 0.125 and 0.60.