US5159547A
Expired / Lapsed
US
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Self-monitoring tuner for feedback controller
Assignee: Boeing North American Inc
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Filing: 1990-10-16
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Granted: 1992-10-27
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Expires: 2010-10-16
Abstract
Abstract An automatic tuner is provided for continuous, on-line tuning of proportional, integral, and derivative (PID) feedback controllers. The tuner compares the system input signals with the system response to generate estimates of system damping, frequency, and steady-state error, and then applies a set of if-then rules derived from mathematical and/or empirical analysis of the system parameters. The tuner represents each parameter of the rule-set by a "fuzzy" membership function, and an inference mechanism uses fuzzy logic for computing system outputs from the input values. The tuner also incorporates a self-monitoring mechanism to adjust the tuner output based on past performance. At each running cycle, the tuner computes a Euclidean distance between present values and desired values in the parameter-space represented by damping, frequency, and steady-state error. The output of the tuner is then scaled by a "reward factor" that is a function of the tuner effectiveness and consistency. If tuner effectiveness degrades, the self-monitoring mechanism diminishes the output of the tuner. If the tuner is operating with consistency, the self-monitoring mechanism increases the output of the tuner. Thus, the self-monitoring mechanism improves performance and robustness of the tuner by scaling the output to produce faster slew rates when the tuner is performing well and by reducing tuner output when performance is poor.
Inventors
- 👤 Sujeet Chand
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:29
CPC Classifications
G; G05; G05B; G05B13/00; G05B13/02; G05B13/0265; G05B13/0275; Y; Y10; Y10S; Y10S706/00; Y10S706/90; Y10S706/902; Y10S706/903; Y10S706/906
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
126 words
A method of feedback control, comprising the steps of: connecting a feedback controller to a controlled system for receiving an input signal, providing a gain signal to said controlled system, and receiving a response signal from said controlled system; connecting a tuner to said controller for comparing said input signal with said system response signal and for applying incremental gain value adjustments to said controller; converting selected parameters of said compared signals to fuzzy logic parameters; applying if-then rules to said fuzzy logic parameters for computing said incremental gain value adjustments; measuring effectiveness and consistency of previously applied gain value adjustments; scaling said computed incremental gain value adjustments based on said measured effectiveness and consistency; and applying said scaled incremental gain value adjustments to said controller.
Claim 2
Independent Claim
126 words
A method of feedback control, comprising the steps of: connecting a feedback controller to a controlled system for receiving an input signal, providing a gain signal to said controlled system, and receiving a response signal from said controlled system; connecting a tuner to said controller for comparing said input signal with said system response signal and for applying incremental gain value adjustments to said controller; converting selected parameters of said compared signals to fuzzy logic parameters; applying if-then rules to said fuzzy logic parameters for computing said incremental gain value adjustments; measuring effectiveness and consistency of previously applied gain value adjustments; scaling said computed incremental gain value adjustments based on said measured effectiveness and consistency; and applying said scaled incremental gain value adjustments to said controller.
Claim 3
Dependent Claim
42 words
The method of claim 1, wherein the step of converting selected parameters further comprises the steps of: computing parameters of system damping, frequency, and steady-state error; and transforming said parameters of system damping, frequency, and steady-state error to corresponding fuzzy membership functions.
Claim 4
Dependent Claim
112 words
The method of claim 2, wherein the step of measuring effectiveness and consistency further comprises the steps of: defining a system state-space having coordinates of damping, frequency, and steady-state error; mapping said computed parameters of system damping, frequency, and steady-state error into said state-space; defining an equilibrium point in said state-space comprising desired values of system damping, frequency, and steady-state error; measuring a distance between said mapped parameters and said equilibrium point in said state-space; computing effectiveness as a difference between two successive measurements of said distance divided by a moving average of said differences; and computing consistency as an inverse of variance of tuner effectiveness over three successive computations of effectiveness.
Claim 5
Dependent Claim
57 words
The method of claim 3, wherein the step of scaling said computed incremental gain value adjustments further comprises the steps of: defining a reward factor as a function of effectiveness and consistency; defining an effectiveness multiplier as a function of effectiveness; and multiplying said computed incremental gain value adjustments by said reward factor and said effectiveness multiplier.
Claim 6
Independent Claim
95 words
A method of adjusting gain of signals provided to a controlled system by a feedback controller, comprising the steps of: comparing a system input signal with a response of the controlled system; transforming system parameters of damping, frequency, and steady-state error to fuzzy logic membership functions; computing gain value adjustments by applying if-then rules to said fuzzy logic membership functions; measuring effectiveness and consistency of previously applied gain value adjustments; scaling said computed gain value adjustments based on said measurements of effectiveness and consistency; and applying said scaled gain value adjustments to the feedback controller.
Claim 7
Independent Claim
95 words
A method of adjusting gain of signals provided to a controlled system by a feedback controller, comprising the steps of: comparing a system input signal with a response of the controlled system; transforming system parameters of damping, frequency, and steady-state error to fuzzy logic membership functions; computing gain value adjustments by applying if-then rules to said fuzzy logic membership functions; measuring effectiveness and consistency of previously applied gain value adjustments; scaling said computed gain value adjustments based on said measurements of effectiveness and consistency; and applying said scaled gain value adjustments to the feedback controller.
Claim 8
Dependent Claim
112 words
The method of claim 5, wherein the step of measuring effectiveness and consistency further comprises the steps of: defining a system state-space having coordinates of damping, frequency, and steady-state error; mapping said system parameters of damping, frequency, and steady-state error into said state-space; defining an equilibrium point in said state-space comprising desired values of system damping, frequency, and steady-state error; measuring a Euclidian distance between said mapped parameters and said equilibrium point in said state-space; computing effectiveness as a difference between two successive measurements of said Euclidian distance divided by a moving average of said differences; and computing consistency as an inverse of variance of effectiveness over three successive computations of effectiveness.
Claim 9
Dependent Claim
54 words
The method of claim 6, wherein the step of scaling said gain value adjustments further comprises the steps of: computing a reward factor as a function of effectiveness and consistency; computing an effectiveness multiplier as a function of effectiveness; and multiplying said computed gain value adjustments by said reward factor and said effectiveness multiplier.
Claim 10
Dependent Claim
107 words
A tuner for applying incremental gain value adjustments to a proportional, integral, and derivative controller, comprising: means for comparing an input signal with a response of a system controlled by the controller; means for transforming system parameters of damping, frequency, and steady-state error to fuzzy membership functions; means for computing the incremental gain value adjustments by applying if-then rules to said fuzzy membership functions; means for measuring effectiveness and consistency of previously applied incremental gain value adjustments; means for scaling said computed incremental gain value adjustments based on said measurements of effectiveness and consistency; and means for applying said scaled incremental gain value adjustments to said controller.
Claim 11
Dependent Claim
107 words
A tuner for applying incremental gain value adjustments to a proportional, integral, and derivative controller, comprising: means for comparing an input signal with a response of a system controlled by the controller; means for transforming system parameters of damping, frequency, and steady-state error to fuzzy membership functions; means for computing the incremental gain value adjustments by applying if-then rules to said fuzzy membership functions; means for measuring effectiveness and consistency of previously applied incremental gain value adjustments; means for scaling said computed incremental gain value adjustments based on said measurements of effectiveness and consistency; and means for applying said scaled incremental gain value adjustments to said controller.
Claim 12
Dependent Claim
112 words
The tuner of claim 8, wherein the means for measuring effectiveness and consistency further comprises: a system state-space defined with coordinates of damping, frequency, and steady-state error; system parameters of damping, frequency, and steady-state error mapped into said state-space; an equilibrium point comprising desired values of system damping, frequency, and steady-state error defined in said state-space; a Euclidian distance measured between said mapped parameters and said equilibrium point in said state-space; means for computing effectiveness as a difference between two successive measurements of said Euclidian distance divided by a moving average of said differences; and means for computing consistency as an inverse of variance of effectiveness over three successive computations of effectiveness.
Claim 13
Dependent Claim
57 words
The tuner of claim 9, wherein the means for scaling said gain value adjustments further comprises: means for computing a reward factor as a function of effectiveness and consistency; means for computing an effectiveness multiplier as a function of effectiveness; and means for multiplying said computed gain value adjustments by said reward factor and said effectiveness multiplier.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-10-27 | 1996-04-27 | 1996-10-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-10-27 | 2000-04-27 | 2000-10-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-10-27 | 2004-04-27 | 2004-10-27 | $7700.00 | Window Closed / Lapsed |