US3725762A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hybrid process controller operable in the automatic and manual
Assignee: Fischer and Porter Co
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Filing: 1971-08-05
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Granted: 1973-04-03
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Expires: 1991-08-05
Abstract
Abstract An electronic controller forming a part of a process control system in which a signal representative of a process variable is compared with a set point signal to produce an output signal to operate a final control element. The controller includes a hybrid digital-analog configuration which permits bumpless transfer between automatic and manual modes, in an arrangement which is drift-free in the manual mode and does not require a long resistor-capacitor time constant.
Inventors
- 👤 P Levesque
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:24
CPC Classifications
G; G05; G05B; G05B7/00; G05B7/02
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
307 words
An electronic controller for a process having a variable condition, the process being provided with a sensor responsive to said condition to produce a process variable signal and a final control element to govern the process, said controller being operable in either the manual or automatic mode and being transferable between modes without giving rise to a process bump, said controller comprising: A. means to produce a deviation voltage whose value depends on the difference between said process variable signal and a set point signal, B. a summing amplifier, C. a deviation voltage integrator and an output voltage integrator, each including means to convert an applied voltage into an analog voltage representing the time integral of the applied voltage, D. switching means in the automatic mode to apply said deviation voltage both as a positive first input to said summing amplifier and as an input to said deviation voltage integrator, and to apply the output voltage of said summing amplifier as an input to said output voltage integrator, the analog voltage developed by said deviation voltage integrator being fed as a positive second input to said summing amplifier, the analog voltage developed by said output voltage integrator being attenuated and applied as a negative third input to said summing amplifier, whereby said summing amplifier sums the first, second and third inputs applied thereto, E. switching means in the manual mode to apply said deviation voltage as an input to said summing amplifier, to connect said deviation voltage integrator between the input and output of said summing amplifier to form a closed feedback loop, and to connect a manual control voltage to the input of said output voltage integrator, and F. means in both the manual and automatic mode to apply the analog voltage developed by said output voltage integrator to said final control element to govern same.
Claim 2
Dependent Claim
307 words
An electronic controller for a process having a variable condition, the process being provided with a sensor responsive to said condition to produce a process variable signal and a final control element to govern the process, said controller being operable in either the manual or automatic mode and being transferable between modes without giving rise to a process bump, said controller comprising: A. means to produce a deviation voltage whose value depends on the difference between said process variable signal and a set point signal, B. a summing amplifier, C. a deviation voltage integrator and an output voltage integrator, each including means to convert an applied voltage into an analog voltage representing the time integral of the applied voltage, D. switching means in the automatic mode to apply said deviation voltage both as a positive first input to said summing amplifier and as an input to said deviation voltage integrator, and to apply the output voltage of said summing amplifier as an input to said output voltage integrator, the analog voltage developed by said deviation voltage integrator being fed as a positive second input to said summing amplifier, the analog voltage developed by said output voltage integrator being attenuated and applied as a negative third input to said summing amplifier, whereby said summing amplifier sums the first, second and third inputs applied thereto, E. switching means in the manual mode to apply said deviation voltage as an input to said summing amplifier, to connect said deviation voltage integrator between the input and output of said summing amplifier to form a closed feedback loop, and to connect a manual control voltage to the input of said output voltage integrator, and F. means in both the manual and automatic mode to apply the analog voltage developed by said output voltage integrator to said final control element to govern same.
Claim 3
Dependent Claim
56 words
An electronic controller as set forth in claim 1, wherein said deviation voltage integrator and said output voltage integrator each include means to convenrt said applied voltage to periodic pulses whose repetition rate is related to the applied voltage and to totalize the pulse to produce a count which is converted into a corresponding analog voltage.
Claim 4
Dependent Claim
28 words
A controller as set forth in claim 1, wherein said deviation voltage is produced by a deviation amplifier adapted to compare said process variable and set point signals.
Claim 5
Dependent Claim
40 words
A controller as set forth in claim 1, wherein the parameters of the arrangement in the automatic mode is such as to produce a summation of the first, second and third inputs to said amplifier which is equal to zero.
Claim 6
Dependent Claim
36 words
A controller as set forth in claim 1, wherein the parameters of the arrangement in the manual mode are such as to produce a summation of the inputs to the amplifier which is equal to zero.
Claim 7
Dependent Claim
57 words
An arrangement as set forth in claim 2, wherein said deviation voltage integrator is constituted by a voltage-to-frequency converter to produce said periodic pulses, a binary divider to divide down said pulses to produce counting pulses, an integrating totalizer to count said counting pulses, and a digital-to-analog converter to produce an analog voltage corresponding to said count.
Claim 8
Dependent Claim
36 words
An arrangement as set forth in claim 2, wherein said output voltage integrator is constituted by a voltage-to-frequency converter, a counter applied to the output of said converter and a digital-to-analog converter coupled to said counter.
Claim 9
Dependent Claim
28 words
An arrangement as set forth in claim 7, further including a gain attentuator interposed between the output of said output voltage integrator and the input of said amplifier.
References Cited (Backward Citations)
US3363157A
Cited
US3655992A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-02 | 1976-10-02 | 1977-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-02 | 1980-10-02 | 1981-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-02 | 1984-10-02 | 1985-04-03 | $7700.00 | Window Closed / Lapsed |