Patent US3697768A successfully refreshed from Google Patents.
US3697768A
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Control systems
Assignee: Emerson Process Management Ltd
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Filing: 1971-02-10
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Granted: 1972-10-10
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Expires: 1991-02-10
Abstract
Abstract A multi-point control system suitable for applications where a large number of processes, typically in excess of 100, are all required to be stabilized at the same operating conditions. The control system comprises on-off controllers fed with a common set-point signal. The controllers being adapted to function as time-proportional controllers by the perturbation of either the set-point signal or the process parameter signal by a periodic waveform. Other signals may be combined with the perturbing signal to provide, for example, compensation for a fluctuating power supply, or for environmental conditions affecting the deviations at the inputs of controllers. Such a system has economical advantages and by slight modifications to the controllers, the system can be used for differing applications.
Inventors
- 👤 James Stewart Johnston
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 08:35
CPC Classifications
G; G05; G05B; G05B11/00; G05B11/01; G05B11/32; G05D; G05D23/00; G05D23/19; G05D23/1906; G05D23/1909; G05D23/20; G05D23/22
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
211 words
A control system for individually controlling the application of a power supply whereby each of a number of processes can be controlled in accordance with the deviation of the value of a sensed variable parameter of each process from a common set-point for the processes, which system comprises a multi-line bus, a controller for each process in the form of a unit connected to said bus, a common power supply source for the controllers feeding common power supply lines in said bus, a common set-point signal source feeding a set-point line in said bus, a common perturbation signal source supplying a periodically varying electrical signal to a perturbation line in said bus, each controller comprising a high gain differential amplifier having a first input, a second input and an output, a sensing device providing a process variable parameter signal, means for connecting said variable parameter signal to said first input via a first resistance, means for connecting said perturbation line to said first input via a second resistance, said second input being connected to said set-point line in said bus, and switching means for controlling the application of said power supply for one of said processes, said switching means having a control input fed by the output of said differential amplifier.
Claim 2
Dependent Claim
211 words
A control system for individually controlling the application of a power supply whereby each of a number of processes can be controlled in accordance with the deviation of the value of a sensed variable parameter of each process from a common set-point for the processes, which system comprises a multi-line bus, a controller for each process in the form of a unit connected to said bus, a common power supply source for the controllers feeding common power supply lines in said bus, a common set-point signal source feeding a set-point line in said bus, a common perturbation signal source supplying a periodically varying electrical signal to a perturbation line in said bus, each controller comprising a high gain differential amplifier having a first input, a second input and an output, a sensing device providing a process variable parameter signal, means for connecting said variable parameter signal to said first input via a first resistance, means for connecting said perturbation line to said first input via a second resistance, said second input being connected to said set-point line in said bus, and switching means for controlling the application of said power supply for one of said processes, said switching means having a control input fed by the output of said differential amplifier.
Claim 3
Dependent Claim
59 words
A control system as defined in claim 1 wherein there are provided means for sensing a disturbance of said power supply for said processes and for feeding a first common correction signal to a correction signal line in said bus, and means for connecting said correction signal line to the first input of each controller via a third resistance.
Claim 4
Dependent Claim
63 words
A control system as defined in claim 1 wherein there are provided means for averaging said deviations, for deriving a second common correction signal from said averaged deviations, and for feeding said second common correction signal to another correction signal line in said bus, and means for connecting said correction signal line to the first input of each controller via another third resistance.
Claim 5
Dependent Claim
98 words
A control system as defined in claim 1 wherein there is provided for at least one controller a variable resistance sensor having one of its two ends connected via a fourth resistance to one of said common power supply lines, its other end connected via a fifth resistance to another of said common power supply lines, and a sixth resistance connected between one end of the or each sensor resistance and said first input of the or each ampliFier, so that the output of the or each amplifier is of the required sense for control of said parameter.
Claim 6
Dependent Claim
97 words
A control system as defined in claim 4 wherein said set-point signal source comprises a potentiometer having one of its ends connected by a seventh resistor to said one of said common power supply lines and its other end connected by an eighth resistance to said another of said common power supply lines, the common set-point signal being fed to the set-point line in said bus from a slider of the potentiometer, and wherein said other end of the or each sensor is connected to said other end of said potentiometer via a line in said bus.
Claim 7
Dependent Claim
54 words
A control system as defined in claim 1 wherein there is provided for at least one controller a thermocouple having at least one hot and cold junction, the thermocouple having an output voltage fed to the first input of the amplifier, and means for combining a cold junction compensation voltage with said set-point signal.
Claim 8
Dependent Claim
51 words
A control system as defined in claim 1 wherein said switching means comprises a semiconductor switch having an input, and triggering means having an output for supplying a firing signal to the input of the semiconductor switch, said triggering means having an input fed by the output of a differential amplifier.
Claim 9
Dependent Claim
16 words
A control system as defined in claim 7 wherein said triggering means comprises a blocking oscillator.
Claim 10
Dependent Claim
19 words
A control system as defined in claim 7 wherein said triggering means comprises a circuit incorporating a reed relay.
Claim 11
Dependent Claim
17 words
A control system as defined in claim 7 wherein said power supply has an A.C. voltage waveform.
Claim 12
Dependent Claim
89 words
A control system as defined in claim 10 wherein there is provided a common gating signal source feeding a gating signal line in said bus, and wherein there is provided for each controller an AND gate having a first input connected to the output of the amplifier and an out-put connected to the input of said triggering means, said gate having a second input connected to said gating signal line, said gating signal comprising a short enable pulse at the start of each half-cycle of said mains power supply.
Claim 13
Dependent Claim
51 words
A control system as defined in claim 10 wherein the period of said periodically varying electrical signal is equal to a half-period of the A.C. voltage waveform of said power supply, and the waveforms are synchronized so that phase angle control of the firing of each semi-conductor switch can be obtained.
Claim 14
Dependent Claim
67 words
A control system as defined in claim 1 wherein said switching means comprises a relay having a relay coil and relay contacts, one end of said relay coil being connected to an amplifier the other end of the relay coil being connected to a common power supply line, there being provided means for permitting the relay coil to be energized for only one sense of said deviation.
Claim 15
Dependent Claim
28 words
A control system as defined in claim 13 wherein said means permitting the energizing of said relay coil comprises a diode connected in series with said relay coil.
Claim 16
Dependent Claim
197 words
A control system for individually controlling the application of a power supply whereby each of a number of processes can be controlled in accordance with the deviation of the value of a sensed variable parameter of each process from a common set-point for the processes, which system comprises a multi-line bus, a controller for each process in the form of a unit connected to said bus, a common power supply source for the controllers feeding common power supply lines in said bus, a common set-point signal source, a common perturbation signal source, summing means for combining said set-point signal and said perturbation signal and for feeding a combined signal onto a set-point line in said bus, each controller comprising a high gain differential amplifier having a first input, a second input, and an output, a sensing device providing a process variable parameter signal, means for connecting said variable parameter signal to said first input said second input being connected to said set-point line in said bus, and switching means for controlling the application of said power supply to one of said processes, said switching means having a control input fed by the output of said differential amplifier.
Claim 17
Dependent Claim
197 words
A control system for individually controlling the application of a power supply whereby each of a number of processes can be controlled in accordance with the deviation of the value of a sensed variable parameter of each process from a common set-point for the processes, which system comprises a multi-line bus, a controller for each process in the form of a unit connected to said bus, a common power supply source for the controllers feeding common power supply lines in said bus, a common set-point signal source, a common perturbation signal source, summing means for combining said set-point signal and said perturbation signal and for feeding a combined signal onto a set-point line in said bus, each controller comprising a high gain differential amplifier having a first input, a second input, and an output, a sensing device providing a process variable parameter signal, means for connecting said variable parameter signal to said first input said second input being connected to said set-point line in said bus, and switching means for controlling the application of said power supply to one of said processes, said switching means having a control input fed by the output of said differential amplifier.
Claim 18
Dependent Claim
36 words
A control system as defined in claim 15 wherein there are provided means for sensing a disturbance of said power supply for said processes and for feeding a first common correction signal to said summing means.
Claim 19
Dependent Claim
40 words
A control system as defined in claim 15 where there are provided means for averaging said deviations, for deriving a second common correction signal from said averaged deviations and for feeding said second common correction signal to said summing means.
Claim 20
Dependent Claim
40 words
A control system as defined in claim 16 wherein there are provided means for averaging said deviations, for deriving a second common correction signal from said averaged deviations and for feeding said second common correction signal to said summing means.
Claim 21
Dependent Claim
30 words
A control system as defined in claim 15 wherein there is additionally provided for at least one controlled process a further controller having its switching means connected to an alarm.
Claim 22
Dependent Claim
19 words
A control system as defined in claim 1 wherein said periodically varying electrical signal is a triangular voltage waveform.
References Cited (Backward Citations)
US3514691A
Cited
US3629562A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-10 | 1976-04-10 | 1976-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-10 | 1980-04-10 | 1980-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-10 | 1984-04-10 | 1984-10-10 | $7700.00 | Window Closed / Lapsed |