Model-free adaptation of a process controller
AssigneeFisher-Rosemount Systems, Inc.
InventorsWilhelm K. Wojsznis, Terrence L. Blevins, Dirk Thiele, John A. Gudaz
Life of this patent
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Abstract
An adaptive process controller drives a process variable to be substantially equivalent to a set point and adapts the controller gain, the controller reset, and/or the controller rate, based on model free adaptation. The adaptive controller combines a controller gain computed from an oscillation index with a controller gain computed from a steady state estimate and that adapts the controller reset/rate by forcing the ratio of two of the controller proportional, integral or derivative terms to be equal to a predetermined value.
Claims50
A tuner for use in tuning a process controller which uses a set point and a process variable to generate a process control signal, the tuner comprising:
- a first module which develops an error signal representative of the difference between the set point and the process variable;
- a
- a gain adaptation module which uses the error signal to develop a gain for use in tuning the process controller, wherein the gain adaptation module calculates the gain as a combination of an oscillation index gain and of a gain calculated from a process steady state gain;
- and
- a second module which monitors the process variable to detect when the process variable oscillates, and upon detection of the process variable oscillating, modifies the gain to prevent the process variable from oscillating.
A tuner for use in tuning a process controller which uses a set point and a process variable to generate a process control signal, the tuner comprising:
- a first module which develops an error signal representative of the difference between the set point and the process variable;
- an adaptation module which uses the error signal to calculate at least two of a proportional term, an controller integral time, and a derivative term for use in tuning the process controller, wherein the adaptation module calculates a first and a second of the proportional, integral and derivative terms so that a ratio of a change in the first term and of a change in the second term is equal to a preset constant;
- and
- a second module which monitors the process variable to detect when the process variable oscillates, and upon detection of the process variable oscillating, modifies at least one of the proportional term, the controller integral time, and the derivative term to prevent the process variable from oscillating.
A tuner for use in tuning a process controller which uses a set point and a process variable to generate a process control signal, the tuner comprising:
- a first module which develops an error signal representative of the difference between the set point and the process variable;
- a gain adaptation module which uses the error signal to develop a gain for use in tuning the process controller, wherein the gain adaptation module calculates the gain as a combination of an oscillation index gain and of a gain calculated from a process steady state gain;
- and
- an adaptation module which uses the error signal to calculate at least two of a proportional term, an controller integral time, and a derivative term for use in tuning the process controller, wherein the adaptation module calculates a first and a second of the proportional, integral, and derivative terms so that a ratio of a change in the first term and of a change in the second term is equal to a preset constant.
A method of tuning a process controller which uses a set point and a process variable to generate a process control signal, the method comprising the steps of:
- developing an error signal representative of the difference between the set point and the process variable;
- and
- calculating at least two of a proportional term, an controller integral time, and a derivative term for use in tuning the process controller, wherein a ratio of a change in first term and of a change in the second term is equal to a preset constant.
A tuning system for tuning a process controller which uses a set point and a process variable to generate a process control signal, the tuning system comprising:
- a memory;
- a first logic routine stored in the memory and executed on a processor to S develop an error signal representative of the difference between the set point and the process variable;
- and
- a second logic routine stored in the memory and executed on a processor to develop a gain for use in tuning the process controller, wherein the gain is a combination of a gain calculated from an oscillation index gain and of a gain calculated from a process steady state gain.
A process control system comprising:
- a process controller which uses a set point and a process variable to generate a process control signal;
- a tuner for tuning the process controller;
- a first module which develops an error signal representative of the difference between the set point and the process variable;
- and
- a gain adaptation module which uses the error signal to develop a gain for use in tuning the process controller, wherein the gain adaptation module calculates the gain as a combination of a gain calculated from an oscillation index gain and of a gain calculated from a process steady state gain.
Dependencies are inferred from the claim text.