US5742503A
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Use of saturation relay feedback in PID controller tuning
Assignee: National Science and Technology Council
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Filing: 1996-03-25
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Granted: 1998-04-21
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Expires: 2016-03-25
Abstract
Abstract A method and an apparatus are provided for autotuning a parameter of a PID controller which is employed in a transfer function. The method includes steps of (a) providing a first specific value for the transfer function; (b) computing a first ultimate parameter of the transfer function in response to the first specific value; (c) modifying the first specific value in response to the first ultimate parameter in order to obtain a second specific value; (d) generating a second ultimate parameter for a characteristic of the transfer function in a specified range in response to the second specific value; (e) obtaining a precise parameter of the PID controller in response to the second ultimate parameter. The autotuning apparatus includes; a controlled device outputting a first ultimate parameter and a second ultimate parameter, respectively in response to a first input signal and a second input signal; a nonlinear element connected to the controlled device, and outputting a first specific signal and a second specific signal in response to a first ultimate parameter; and a control unit connected to the nonlinear element, wherein the nonlinear element outputs the second input signal to cause the controlled device to output to the PID controller the second ultimate parameter for a specific characteristic of the controlled device in a specific range in order to obtain a precise parameter for the PID controller.
Inventors
- 👤 Cheng-ching Yu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 06:04
CPC Classifications
G; G05; G05B; G05B11/00; G05B11/44; G05B11/48; G05B11/52; G05B11/01; G05B11/36; G05B11/42; G05B13/00; G05B13/02; G05B13/04; G05B13/042
Claims Analysis
Total Claims: 49
Claim 1
Independent Claim
110 words
A method for finding the ultimate properties of a transfer function employed in the autotuning of a PID controller, comprising steps of (a) providing a first specific value for said transfer function; (b) computing a first ultimate parameter of said transfer function in response to said first specific value; (c) modifying said first specific value in response to said first ultimate parameter in order to obtain a second specific value; (d) generating a second ultimate parameter for a characteristic of said transfer function in a specified range in response to said second specific value; (e) obtaining a precise parameter of said PID controller in response to said second ultimate parameter.
Claim 2
Independent Claim
110 words
A method for finding the ultimate properties of a transfer function employed in the autotuning of a PID controller, comprising steps of (a) providing a first specific value for said transfer function; (b) computing a first ultimate parameter of said transfer function in response to said first specific value; (c) modifying said first specific value in response to said first ultimate parameter in order to obtain a second specific value; (d) generating a second ultimate parameter for a characteristic of said transfer function in a specified range in response to said second specific value; (e) obtaining a precise parameter of said PID controller in response to said second ultimate parameter.
Claim 3
Dependent Claim
27 words
A method according to claim 1, wherein said transfer function is denoted by G(s), which is a function obtained by Laplace-transformation and defined in a frequency domain.
Claim 4
Dependent Claim
25 words
A method according to claim 1, wherein said first specific value is an amplitude of a square-wave, which is generated from a first nonlinear element.
Claim 5
Dependent Claim
15 words
A method according to claim 3, wherein said first nonlinear element is an on/off relay.
Claim 6
Dependent Claim
26 words
A method according to claim 4, wherein said first ultimate parameter includes by a rough ultimate gain and a rough ultimate frequency of said transfer function.
Claim 7
Dependent Claim
19 words
A method according to claim 5, wherein said first ultimate parameter is obtained according to a continuous cycling calculation.
Claim 8
Dependent Claim
26 words
A method according to claim 3, wherein said second specific value is an amplitude of a sine-wave-like wave, which is generated from a second nonlinear element.
Claim 9
Dependent Claim
15 words
A method according to claim 7, wherein said second nonlinear element is a saturation relay.
Claim 10
Dependent Claim
24 words
A method according to claim 8, wherein said sine-wave-like wave is obtained by appropriate selecting a slope of a ramp portion of a signal.
Claim 11
Dependent Claim
34 words
A method according to claim 8, wherein said slope is less than a bounded value K max in order to make a performance of said saturation relay different from that of said on/off relay.
Claim 12
Dependent Claim
17 words
A method according to claim 8, wherein said saturation relay is described by a describing function N(a).
Claim 13
Dependent Claim
19 words
A method according to claim 11, wherein said second ultimate parameter is obtained by employing said describing function N(a).
Claim 14
Dependent Claim
22 words
A method according to claim 12, wherein said describing function is obtained by employing a first term coefficient of a Fourier expansion.
Claim 15
Dependent Claim
25 words
A method according to claim 8, wherein said second ultimate parameter includes a precise ultimate gain and a precise ultimate frequency of said transfer function.
Claim 16
Dependent Claim
43 words
A method according to claim 14, wherein said sine-wave-like wave generated from said saturation relay is transmitted to said transfer function and said precise ultimate gain and said precise ultimate frequency of said transfer function are obtained according to said limit cycle calculation.
Claim 17
Dependent Claim
19 words
A method according to claim 14, wherein said second ultimate parameter is obtained according to a limit cycle calculation.
Claim 18
Dependent Claim
17 words
A method according to claim 16, wherein a period of said limit cycle is P u .
Claim 19
Dependent Claim
17 words
A method according to claim 16, wherein a first existing condition for said limit cycle is 1+G(jω)N(a)=0.
Claim 20
Dependent Claim
36 words
A method according to claim 16, wherein a second existing condition for said limit cycle is that said slope of said sine-wave-like wave generated from said saturation relay is greater than a value K min .
Claim 21
Dependent Claim
33 words
A method according to claim 7, wherein said first ultimate parameter of said transfer function is transmitted to said second nonlinear element by employing a signal feedback means including a signal feedback line.
Claim 22
Dependent Claim
32 words
A method according to claim 8, wherein said second ultimate parameter of said transfer function is transmitted to said PID controller by employing a signal feedback means including a signal feedback line.
Claim 23
Dependent Claim
44 words
A method according to claim 21, wherein a selecting switch is employed for switching from causing a feedback by said first ultimate parameter of said transfer function to said nonlinear element into causing a feedback by said second ultimate parameter to said PID controller.
Claim 24
Dependent Claim
32 words
A method according to claim 22, wherein said an another selecting switch is also employed for said transfer function in order to replace said first specific value by said second specific value.
Claim 25
Dependent Claim
26 words
A method according to claim 23, wherein said first specific value and said second specific value are represented by a square-wave and a sine-wave-like wave, respectively.
Claim 26
Dependent Claim
45 words
A method according to claim 1, characterized in that an intersection c located at negative real axis of a complex-plane, is obtained by intersecting the locus of G(jω) derived from said transfer function G(s) with a locus of -1/N(a) derived from said describing function N(a).
Claim 27
Dependent Claim
35 words
A method according to claim 25, wherein said specified range is that said locus of G(jω) has to enclose a starting point b of said -1/N(a) locus located at negative real axis of said complex-plane.
Claim 28
Dependent Claim
27 words
A method according to claim 1, wherein said first ultimate parameter obtained by computation is used as a reference in order to compute said second ultimate parameter.
Claim 29
Dependent Claim
12 words
A method according to claim 1, being used for a system identification.
Claim 30
Dependent Claim
132 words
An autotuning apparatus used to modulate a parameter of a PID controller which is employed for controlling a controlled device, comprising; said controlled device outputting a first ultimate parameter and a second ultimate parameter, respectively in response to a first input signal and a second input signal; a nonlinear element connected to said controlled device, and outputting a first specific signal and a second specific signal in response to a first ultimate parameter; and a control unit connected to said nonlinear element, and by means of said nonlinear element outputting said second input signal to cause said controlled device to output to said PID controller said second ultimate parameter for a specific characteristic of said controlled device in a specific range in order to obtain a precise parameter for said PID controller.
Claim 31
Dependent Claim
132 words
An autotuning apparatus used to modulate a parameter of a PID controller which is employed for controlling a controlled device, comprising; said controlled device outputting a first ultimate parameter and a second ultimate parameter, respectively in response to a first input signal and a second input signal; a nonlinear element connected to said controlled device, and outputting a first specific signal and a second specific signal in response to a first ultimate parameter; and a control unit connected to said nonlinear element, and by means of said nonlinear element outputting said second input signal to cause said controlled device to output to said PID controller said second ultimate parameter for a specific characteristic of said controlled device in a specific range in order to obtain a precise parameter for said PID controller.
Claim 32
Dependent Claim
19 words
An autotuning apparatus according to claim 29, wherein said controlled device is a device used in a distillation process.
Claim 33
Dependent Claim
23 words
An autotuning apparatus according to claim 29, wherein said first input signal is a square-wave signal which is generated form said nonlinear element.
Claim 34
Dependent Claim
15 words
An autotuning apparatus according to claim 31, wherein said nonlinear element is an on/off relay.
Claim 35
Dependent Claim
23 words
An autotuning apparatus according to claim 31, wherein said second input signal is a sine-wave-like signal which is generated from said nonlinear element.
Claim 36
Dependent Claim
15 words
An autotuning apparatus according to claim 33, wherein said nonlinear element is a saturation relay.
Claim 37
Dependent Claim
22 words
An autotuning apparatus according to claim 29, wherein said first ultimate parameter includes a rough ultimate gain and a rough ultimate frequency.
Claim 38
Dependent Claim
25 words
An autotuning apparatus according to claim 35, wherein said rough ultimate gain and said rough ultimate frequency are obtained according to a continuous cycle calculation.
Claim 39
Dependent Claim
22 words
An autotuning apparatus according to claim 34, wherein said second ultimate parameter includes a precise ultimate gain and a precise ultimate frequency.
Claim 40
Dependent Claim
20 words
An autotuning apparatus according to claim 37, wherein said second ultimate parameter is obtained according to a limit cycle calculation.
Claim 41
Dependent Claim
44 words
An autotuning apparatus according to claim 38, wherein a sine-wave-like signal generated from said saturation relay is transmitted to said controlled device and said precise ultimate gain and said precise ultimate frequency of said controlled device are obtained according to said limit cycle calculation.
Claim 42
Dependent Claim
32 words
An autotuning apparatus according to claim 29, wherein said first ultimate parameter of said controlled device is transmitted to said nonlinear element by a signal feedback apparatus including a signal feedback line.
Claim 43
Dependent Claim
32 words
An autotuning apparatus according to claim 29, wherein said second ultimate parameter of said controlled device is transmitted to said PID controller by a signal feedback apparatus including a signal feedback line.
Claim 44
Dependent Claim
45 words
An autotuning apparatus according to claim 29, wherein a selecting switch is employed for switching from causing a feedback by said first ultimate parameter of said controlled device to said nonlinear element into causing a feedback by said second ultimate parameter to said PID controller.
Claim 45
Dependent Claim
31 words
An autotuning apparatus according to claim 42, wherein said selecting switch is also employed for said controlled device in order to replace said first specific signal by said second specific signal.
Claim 46
Dependent Claim
28 words
An autotuning apparatus according to claim 43, wherein said first specific signal and said second specific signal are represented by a square-wave signal and a sine-wave-like signal, respectively.
Claim 47
Dependent Claim
67 words
A autotuning apparatus according to claim 29, characterized in that an intersection c located at negative real axis of a complex-plane, is obtained by intersecting the locus of G(ω) function derived from said controlled device with a locus of -1/N(a) derived from said describing function N(a), wherein G(jω) is the transfer function of said controlled device and N(a) is a describing function employed for said nonlinear element.
Claim 48
Dependent Claim
37 words
A autotuning apparatus according to claim 45, wherein said specified range is that said the locus of G(jω) has to enclose a starting point b of said -1/N(a) locus located at negative real axis of said complex-plane.
Claim 49
Dependent Claim
35 words
An autotuning apparatus according to claim 29, wherein said autotuning apparatus is implemented one selected from a group consisting of a distributed control system (DCS), a single station controller control, and a microcomputer control system.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-04-20 | 2001-10-20 | 2002-04-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-04-20 | 2005-10-20 | 2006-04-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-04-20 | 2009-10-20 | 2010-04-21 | $7700.00 | Window Closed / Lapsed |