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US3705978A
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Time shared digital and analog process control
Assignee: Agfa Gevaert NV
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Filing: 1970-09-09
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Granted: 1972-12-12
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Expires: 1990-09-09
Abstract
Abstract A digital computer is used in a time sharing technique to control a plurality of control circuits. The frequency of sampling fs may be low in comparison with the frequency of sampling in conventional direct digital control, and the capacity of the digital computer correspondingly be increased, if each variable in the process is controlled according to an analog control, and the analog reference value in the analog control is derived from a digital reference value which is sequentially corrected in accordance with a correction value which is obtained from the comparison of said digital reference value with a digital value derived from the process.
Inventors
- 👤 Lucien Amede De Schamphelaere
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:58
CPC Classifications
G; G05; G05B; G05B15/00; G05B15/02; G05B2219/00; G05B2219/30; G05B2219/34; G05B2219/34239; G05B2219/42; G05B2219/42076
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
151 words
A method for controlling a plurality of variables in a process which comprises: a. sequentially comparing a digital reference value (rd) for each variable in the process with a digital value (md) observed in the process in order to produce a control error (e1), b. feeding each control error (e1)sequentially to a digital computer in order to produCe a corresponding correction value (u1), c. correcting each digital reference value (rd) sequentially in accordance with the corresponding correction value (u1), d. deriving a corresponding analog reference value (r''a) from each corrected digital reference value, e. continuously measuring the actual value (ma) of each variable in the process according to an analog measurement and comparing it with the corresponding derived analog reference value (r''a) to produce a control error (e2), and f. feeding the control error (e2) resulting from such comparison to an analog controller which controls the corresponding variable in the process.
Claim 2
Independent Claim
151 words
A method for controlling a plurality of variables in a process which comprises: a. sequentially comparing a digital reference value (rd) for each variable in the process with a digital value (md) observed in the process in order to produce a control error (e1), b. feeding each control error (e1)sequentially to a digital computer in order to produCe a corresponding correction value (u1), c. correcting each digital reference value (rd) sequentially in accordance with the corresponding correction value (u1), d. deriving a corresponding analog reference value (r''a) from each corrected digital reference value, e. continuously measuring the actual value (ma) of each variable in the process according to an analog measurement and comparing it with the corresponding derived analog reference value (r''a) to produce a control error (e2), and f. feeding the control error (e2) resulting from such comparison to an analog controller which controls the corresponding variable in the process.
Claim 3
Dependent Claim
16 words
Method according to claim 1, wherein the digital value (md) is directly measured in the process.
Claim 4
Dependent Claim
29 words
Method according to claim 1, wherein the digital value (md) is obtained by converting an analog measured value of a variable in the process into a corresponding digital value.
Claim 5
Dependent Claim
36 words
Method according to claim 1, wherein the correction value (u1) is an analog signal and the digital reference value (rd) is converted into an analog signal (ra) before it is corrected by the analog signal (u1).
Claim 6
Dependent Claim
20 words
Method according to claim 1, wherein each correction value (u1) is stored during the sequential operations of the digital computer.
Claim 7
Dependent Claim
22 words
Method according to claim 1, wherein each corresponding analog reference value (r''a) is stored during the sequential operations of the digital computer.
Claim 8
Independent Claim
222 words
A device for controlling a plurality of variables in a process which comprises: a. an analog controller (C2) for each variable in the process b. a generator (R) which produces a digital reference value (rd) for each variable, c. means which produces a digital measured value (md) for each variable in the process, d. comparator means (S1) which compares the digital reference value (rd) with the digital measured value (md) of a variable and which produces an error signal (e1), e. a digital controller (C1) and means for connecting sequentially the difference error signals (e1) to the input of said controller to produce correction output signals (u1), f. means for connecting the correction output signals (u1) produced by the digital controller sequentially to summers one summer being provided for each variable in the process, and each summer adding the correction signal (u1) to the corresponding digital reference value (rd) to produce a corrected reference value (r''d), g. convertor means which converts each said corrected digital reference value into a corresponding analog value (r''a) h. means for producing an analog measured value (ma) for each variable in the process, and i. comparator means (S2) which compares said derived analog value (r''a) with the measured analog value (ma) for each variable, and which produces an error signal which controls the corresponding analog controller C2.
Claim 9
Independent Claim
222 words
A device for controlling a plurality of variables in a process which comprises: a. an analog controller (C2) for each variable in the process b. a generator (R) which produces a digital reference value (rd) for each variable, c. means which produces a digital measured value (md) for each variable in the process, d. comparator means (S1) which compares the digital reference value (rd) with the digital measured value (md) of a variable and which produces an error signal (e1), e. a digital controller (C1) and means for connecting sequentially the difference error signals (e1) to the input of said controller to produce correction output signals (u1), f. means for connecting the correction output signals (u1) produced by the digital controller sequentially to summers one summer being provided for each variable in the process, and each summer adding the correction signal (u1) to the corresponding digital reference value (rd) to produce a corrected reference value (r''d), g. convertor means which converts each said corrected digital reference value into a corresponding analog value (r''a) h. means for producing an analog measured value (ma) for each variable in the process, and i. comparator means (S2) which compares said derived analog value (r''a) with the measured analog value (ma) for each variable, and which produces an error signal which controls the corresponding analog controller C2.
Claim 10
Dependent Claim
17 words
A device according to claim 7, wherein said digital controller C1 is a general purpose digital computer.
Claim 11
Dependent Claim
47 words
A device according to claim 7, wherein said means for producing a digital measured value (md) for each variable in the process comprises an analog to digital converter (ADC) which converts an analog value (ma) of a variable measured in the process into a corresponding digital value.
Claim 12
Dependent Claim
34 words
A device according to claim 7, wherein a memory circuit is provided for each variable to be controlled which stores the correction output signal (u1) produced by the digital controller C1 for each variable.
Claim 13
Dependent Claim
46 words
A device according to claim 7, wherein a memory circuit is provided for each variable to be controlled in the process, and each said memory circuit stores the analog value (r''a), corresponding with the corrected digital reference value, which is fed to a corresponding comparator S2.
References Cited (Backward Citations)
US2932471A
Cited
US3483362A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-12-12 | 1976-06-12 | 1976-12-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-12 | 1980-06-12 | 1980-12-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-12 | 1984-06-12 | 1984-12-12 | $7700.00 | Window Closed / Lapsed |