US3566091A
Expired / Lapsed
US
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Method and apparatus for controlling a process variable by manipulation of a selected one of two variables
Assignee: Leeds and Northrup Co
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Filing: 1966-09-02
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Granted: 1971-02-23
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Expires: 1986-09-02
Abstract
Abstract A method and means for controlling a rotary kiln so as to maintain the desired temperature in the burning zone utilizes a selected one of two variables to effect the control. The burning zone temperature is controlled by controlling the speed of the kiln or by controlling the firing rate. The system is specifically designed to provide an arrangement for determining whether the control will be effected by a change in firing rate. Also, the amount of proportional action which is utilized in the control and the decision as to whether or not rate and reset action will be applied is determined by the logic of the system. An anticipatory control from CO is provided. The control system is so organized that proportional action may be doubled when the burning zone temperature is above or below a predetermined limit. Also, rate action is incorporated in the control only when the burning zone temperature is decreasing below a certain high limit or increasing above a certain low limit and reset action is utilized only within predetermined limits.
Inventors
- 👤 Theodosios Bay
- 👤 Charles W Ross
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 06:27
CPC Classifications
F; F27; F27B; F27B7/00; F27B7/20; F27B7/42; G; G05; G05B; G05B11/00; G05B11/01; G05B11/36; G05B11/42
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
266 words
The method for controlling a process in which at least two manipulated variables may be used to control a single measured variable and in which there are constraints on allowable variations of the process conditions modified by the manipulated variables comprising the steps of; producing an error signal representative of the deviation of said measured variable from its desired value, producing from said error signal another signal representative of the rate of change of said error signal, producing from said rate of change signal a control signal of magnitude indicative of the magnitude of the control action required for a preferred one of said manipulated variables to reduce said error signal to zero, producing a selection signal for effecting a selection of the variable to be controlled, said selection signal being such that a variable other than said preferred variable is selected when the control action called for by said control signal is of magnitude and direction such that control of the preferred variable could cause conditions of the process, subject to variations by changes in the preferred variable, to exceed preestablished constraints or when control of said other variable would cause the other variable to be controlled toward its set point, producing from said rate of change signal a control signal of magnitude indicative of the magnitude of the control action required for said other variaBle to reduce said error signal to zero when said selection signal is operative to select said other variable, and controlling the selected manipulated variable in response to that one of said control signals produced for the selected manipulated variable.
Claim 2
Independent Claim
266 words
The method for controlling a process in which at least two manipulated variables may be used to control a single measured variable and in which there are constraints on allowable variations of the process conditions modified by the manipulated variables comprising the steps of; producing an error signal representative of the deviation of said measured variable from its desired value, producing from said error signal another signal representative of the rate of change of said error signal, producing from said rate of change signal a control signal of magnitude indicative of the magnitude of the control action required for a preferred one of said manipulated variables to reduce said error signal to zero, producing a selection signal for effecting a selection of the variable to be controlled, said selection signal being such that a variable other than said preferred variable is selected when the control action called for by said control signal is of magnitude and direction such that control of the preferred variable could cause conditions of the process, subject to variations by changes in the preferred variable, to exceed preestablished constraints or when control of said other variable would cause the other variable to be controlled toward its set point, producing from said rate of change signal a control signal of magnitude indicative of the magnitude of the control action required for said other variaBle to reduce said error signal to zero when said selection signal is operative to select said other variable, and controlling the selected manipulated variable in response to that one of said control signals produced for the selected manipulated variable.
Claim 3
Dependent Claim
48 words
The method of claim 1 in which the process under control includes a rotary cement kiln and in which the measured variable is the burning zone temperature of the kiln; the manipulated variables are fuel feed rate and the kiln speed, the preferred variable being fuel feed rate.
Claim 4
Dependent Claim
20 words
The method of claim 2 in which the preestablished constraints include the unavailability of measurement of the kiln exit oxygen.
Claim 5
Dependent Claim
46 words
The method of claim 2 in which the preestablished constraints include a low limit on the burning zone temperature and a kiln speed above its set point when the control action called for by the control signal for the fuel feed rate calls for an increase.
Claim 6
Dependent Claim
42 words
The method of claim 2 in which the preestablished constraints include a low limit on the concentration of oxygen in the kiln exit when the control action called for by the control signal for the fuel feed rate calls for an increase.
Claim 7
Dependent Claim
32 words
The method of claim 2 in which the preestablished constraints include a high limit on the fuel feed rate when the control signal for the fuel feed rate calls for an increase.
Claim 8
Dependent Claim
42 words
The method of claim 2 in which the preestablished constraints include a high limit for the carbon monoxide concentration in the kiln exit when the control action called for by the control signal for the fuel feed rate calls for an increase.
Claim 9
Dependent Claim
49 words
The method of claim 2 in which the preestablished constraints include a low limit for the fuel feed rate when the computed desired kiln speed is below a high limit and the control action called for by the control signal for the fuel feed rate calls for a decrease.
Claim 10
Independent Claim
269 words
A system for controlling a process in which at least two manipulated variables may be used to control a single measured variable and in which there are constraints on allowable variation of the process conditions modified by the manipulated variables comprising: means for producing an error signal representative of the deviation of said measured variable from its desired value, means for producing from said error signal another signal representative of the rate of change of said error signal, means for producing from said rate of change signal a control signal of magnitude indicative of the magnitude of the control action required for a preferred one of said manipulated variables to reduce said error signal to zero, means for producing a selection signal for effecting a selection of the variable to be controlled, said means for producing a selection signal being operative to select a variable other than said preferred variable when the control action called for by said control signal is of magnitude and direction such that control of the preferred variable would cause conditions of the process, subject to variations by changes in the preferred variable, to exceed preestablished constraints and when control of said other variable would cause the other variable to be controlled toward its set point, means for producing from said rate of change signal a control signal of magnitude indicative of the magnitude of the control action required for said other variable to reduce said error signal to zero when said selection signal is operative to select said other variable, and means for controlling the selected manipulated variable in response to said control signal.
Claim 11
Independent Claim
269 words
A system for controlling a process in which at least two manipulated variables may be used to control a single measured variable and in which there are constraints on allowable variation of the process conditions modified by the manipulated variables comprising: means for producing an error signal representative of the deviation of said measured variable from its desired value, means for producing from said error signal another signal representative of the rate of change of said error signal, means for producing from said rate of change signal a control signal of magnitude indicative of the magnitude of the control action required for a preferred one of said manipulated variables to reduce said error signal to zero, means for producing a selection signal for effecting a selection of the variable to be controlled, said means for producing a selection signal being operative to select a variable other than said preferred variable when the control action called for by said control signal is of magnitude and direction such that control of the preferred variable would cause conditions of the process, subject to variations by changes in the preferred variable, to exceed preestablished constraints and when control of said other variable would cause the other variable to be controlled toward its set point, means for producing from said rate of change signal a control signal of magnitude indicative of the magnitude of the control action required for said other variable to reduce said error signal to zero when said selection signal is operative to select said other variable, and means for controlling the selected manipulated variable in response to said control signal.
Claim 12
Dependent Claim
44 words
The system of claim 9 in which the process under control includes a rotary cement kiln and in which the measured variable is burning zone temperature and the manipulated variables are fuel feed rate and kiln speed, the preferred variable being fuel feed rate.
Claim 13
Dependent Claim
20 words
The system of claim 10 in which the preestablished constraints include the unavailability of measurement of the kiln exit oxygen.
Claim 14
Dependent Claim
46 words
The system of claim 10 in which the pReestablished constraints include a low limit on the burning zone temperature and a kiln speed above its set point when the control action called for by the control signal for the fuel feed rate calls for an increase.
Claim 15
Dependent Claim
42 words
The system of claim 10 in which the preestablished constraints include a low limit on the concentration of oxygen in the kiln exit when the control action called for by the control signal for the fuel feed rate calls for an increase.
Claim 16
Dependent Claim
32 words
The system of claim 10 in which the preestablished constraints include a high limit on the fuel feed rate when the control signal for the fuel feed rate calls for an increase.
Claim 17
Dependent Claim
42 words
The system of claim 10 in which the preestablished constraints include a high limit for the carbon monoxide concentration in the kiln exit when the control action called for by the control signal for the fuel feed rate calls for an increase.
Claim 18
Dependent Claim
49 words
The system of claim 10 in which the preestablished constraints include a low limit for the fuel feed rate when the computed desired kiln speed is below a high limit and the control action called for by the control signal for the fuel feed rate calls for a decrease.
Claim 19
Independent Claim
130 words
The method of controlling the temperature of the clinker in the burning zone in a rotary cement kiln comprising the steps of: establishing an error signal representative of the difference between the desired value for said temperature and its measured value, establishing from said error signal separate signals representing respectively a proportional control signal, a reset signal and a rate control signal, selecting one of the temperature changing manipulated variables, fuel feed rate and kiln speed variable, to be the controlled variable said selection being made in accordance with the conditions of said kiln and the direction of temperature change necessary, and controlling the selected one of the temperature changing manipulated variables in response to said control signals so as to tend to return said temperature to its desired value.
Claim 20
Independent Claim
130 words
The method of controlling the temperature of the clinker in the burning zone in a rotary cement kiln comprising the steps of: establishing an error signal representative of the difference between the desired value for said temperature and its measured value, establishing from said error signal separate signals representing respectively a proportional control signal, a reset signal and a rate control signal, selecting one of the temperature changing manipulated variables, fuel feed rate and kiln speed variable, to be the controlled variable said selection being made in accordance with the conditions of said kiln and the direction of temperature change necessary, and controlling the selected one of the temperature changing manipulated variables in response to said control signals so as to tend to return said temperature to its desired value.
Claim 21
Dependent Claim
32 words
The method of control as called for in claim 17 in which the proportional control signal is enhanced by a predetermined factor whenever said error signal is beyond a predetermined limit value.
Claim 22
Dependent Claim
31 words
A method of control as called for in claim 17 in which the response to said reset control signal is discontinued when said error signal is outside a predetermined limit value.
Claim 23
Dependent Claim
59 words
The method of control as called for in claim 17 in which the response to said rate action is effective only when said error signal is increasing in value and said error signal is below a predetermined high limit value as well as when said error signal is decreasing in value and is above a predetermined low limit value.
Claim 24
Dependent Claim
90 words
The method called for in claim 17 in which the proportional control response is enhanced by a predetermined factor whenever said error signal is beyond predetermined high and low limit values; the response to said reset control signal is discontinued when said error signal is outside predetermined high and low limits and the response to said rate action is effective only when said error signal is increasing and is below a predetermined high limit as well as when said error signal is decreasing and is above a predetermined low limit.
Claim 25
Dependent Claim
168 words
A control system for controlling the temperature in the burning zone of a rotary cement kiln comprising: means for producing an error signal in response to the deviation of said temperature from its desired value, means responsive to said error signal for producing as separate signals a proportional control signal, a reset control signal and a rate control signal, means for selectively enhancing said proportional control signal by adding a signal which is a predetermined factor multiplied by said proportional control signal, when said error signal is below a predetermined limiting value, and means for normally controlling the fuel flow to said kiln in response to said proportional, reset and rate control sIgnals when such control of the fuel flow will not adversely affect other conditions of the kiln, and for controlling kiln speed in response to said proportional, reset and rate control signals when said other conditions of the kiln will be adversely affected by a change in the fuel flow in response to said control signals.
Claim 26
Dependent Claim
168 words
A control system for controlling the temperature in the burning zone of a rotary cement kiln comprising: means for producing an error signal in response to the deviation of said temperature from its desired value, means responsive to said error signal for producing as separate signals a proportional control signal, a reset control signal and a rate control signal, means for selectively enhancing said proportional control signal by adding a signal which is a predetermined factor multiplied by said proportional control signal, when said error signal is below a predetermined limiting value, and means for normally controlling the fuel flow to said kiln in response to said proportional, reset and rate control sIgnals when such control of the fuel flow will not adversely affect other conditions of the kiln, and for controlling kiln speed in response to said proportional, reset and rate control signals when said other conditions of the kiln will be adversely affected by a change in the fuel flow in response to said control signals.
Claim 27
Independent Claim
97 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: controlling one of the group of manipulated variables consisting of fuel feed rate and kiln speed to tend to maintain said temperature at a desired value, measuring the carbon monoxide in the exit gases of said kiln, and decreasing said fuel feed rate and decreasing said kiln speed by comparable amounts in response to an increase in the carbon monoxide in the exit gases of said kiln for preventing dangerous conditions in said kiln without substantially modifying said temperature.
Claim 28
Independent Claim
97 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: controlling one of the group of manipulated variables consisting of fuel feed rate and kiln speed to tend to maintain said temperature at a desired value, measuring the carbon monoxide in the exit gases of said kiln, and decreasing said fuel feed rate and decreasing said kiln speed by comparable amounts in response to an increase in the carbon monoxide in the exit gases of said kiln for preventing dangerous conditions in said kiln without substantially modifying said temperature.
Claim 29
Independent Claim
170 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: developing a control signal indicative of the magnitude and direction of change necessary for the fuel feed rate to tend to maintain said temperature at its desired value, controlling said fuel feed rate in response to said control signal when the conditions of the kiln process are such that upon a change in fuel feed rate in the direction called for, no undesirable results will occur, measuring the concentration of oxygen in the exit gases of the kiln, and controlling the kiln speed in response to said control signal when the conditions of the kiln process are such that, with the direction of change called for, undesirable results may occur if control is effected by changing the fuel feed rate, said conditions including the unavailability of said oxygen measurement at the kiln exit when the change called for is one which tends to result in an increase in temperature of said material.
Claim 30
Independent Claim
170 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: developing a control signal indicative of the magnitude and direction of change necessary for the fuel feed rate to tend to maintain said temperature at its desired value, controlling said fuel feed rate in response to said control signal when the conditions of the kiln process are such that upon a change in fuel feed rate in the direction called for, no undesirable results will occur, measuring the concentration of oxygen in the exit gases of the kiln, and controlling the kiln speed in response to said control signal when the conditions of the kiln process are such that, with the direction of change called for, undesirable results may occur if control is effected by changing the fuel feed rate, said conditions including the unavailability of said oxygen measurement at the kiln exit when the change called for is one which tends to result in an increase in temperature of said material.
Claim 31
Independent Claim
200 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: developing a control signal indicative of the magnitude and direction of change necessary for the fuel feed rate to tend to maintain said temperature at its desired value, controlling said fuel feed rate in response to said control signal when the conditions of the kiln process are such that upon a change in fuel feed rate in the direction called for, no undesirable results will occur, measuring the concentration of oxygen in the exit gases of the kiln, and controlling the kiln speed in response to said control signal when the conditions of the kiln process are such that, with the direction of change called for, undesirable results may occur if control is effected by changing the fuel feed rate, said conditions including the coincident occurrence of a computed value for the desired kiln speed which is less than the present high limit for said speed and the unavailability of said oxygen measurement at the kiln exit when the change in fuel feed rate called for is one which is intended to result in a decrease in the temperature of said material.
Claim 32
Independent Claim
200 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: developing a control signal indicative of the magnitude and direction of change necessary for the fuel feed rate to tend to maintain said temperature at its desired value, controlling said fuel feed rate in response to said control signal when the conditions of the kiln process are such that upon a change in fuel feed rate in the direction called for, no undesirable results will occur, measuring the concentration of oxygen in the exit gases of the kiln, and controlling the kiln speed in response to said control signal when the conditions of the kiln process are such that, with the direction of change called for, undesirable results may occur if control is effected by changing the fuel feed rate, said conditions including the coincident occurrence of a computed value for the desired kiln speed which is less than the present high limit for said speed and the unavailability of said oxygen measurement at the kiln exit when the change in fuel feed rate called for is one which is intended to result in a decrease in the temperature of said material.
Claim 33
Dependent Claim
179 words
A control system for controlling the temperature in the burning zone of a rotary cement kiln comprising: means for producing an error signal in response to the deviation of said temperature from its desired value, means responsive to said error signal for producing as separate signals a proportional control signal, a reset control signal and a rate control signal, means for selectively enhancing said proportional control signal by adding a signal which is a predetermined factor multiplied by said proportional control signal, when said error signal is below a predetermined limiting value, measuring the concentration of oxygen in the exit gases of the kiln, and means for normally controlling the fuel flow to said kiln in response to said proportional, reset and rate control signals when such control of the fuel flow wIll not adversely affect other conditions of the kiln, and for controlling kiln speed in response to said proportional, reset and rate control signals when a control of the fuel flow would cause an increase in the fuel flow and the kiln exit oxygen measurement is unavailable.
Claim 34
Dependent Claim
179 words
A control system for controlling the temperature in the burning zone of a rotary cement kiln comprising: means for producing an error signal in response to the deviation of said temperature from its desired value, means responsive to said error signal for producing as separate signals a proportional control signal, a reset control signal and a rate control signal, means for selectively enhancing said proportional control signal by adding a signal which is a predetermined factor multiplied by said proportional control signal, when said error signal is below a predetermined limiting value, measuring the concentration of oxygen in the exit gases of the kiln, and means for normally controlling the fuel flow to said kiln in response to said proportional, reset and rate control signals when such control of the fuel flow wIll not adversely affect other conditions of the kiln, and for controlling kiln speed in response to said proportional, reset and rate control signals when a control of the fuel flow would cause an increase in the fuel flow and the kiln exit oxygen measurement is unavailable.
Claim 35
Independent Claim
163 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: developing a control signal indicative of the magnitude and direction of change necessary for the fuel feed rate to tend to maintain said temperature at its desired value, measuring the oxygen concentration in the exit gases of said kiln, controlling said fuel feed rate in response to said control signal when the conditions of the kiln process are such that upon a change in fuel feed rate in the direction called for, no undesirable results will occur, and controlling the kiln speed in response to said control signal when the measured oxygen concentration in the kiln exit gases is less than a preset low limit established for that concentration when the change in fuel feed rate called for is one which would tend to result in an increase in the temperature of said material, whereby undesirable results from changing the fuel feed rate are avoided.
Claim 36
Independent Claim
163 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: developing a control signal indicative of the magnitude and direction of change necessary for the fuel feed rate to tend to maintain said temperature at its desired value, measuring the oxygen concentration in the exit gases of said kiln, controlling said fuel feed rate in response to said control signal when the conditions of the kiln process are such that upon a change in fuel feed rate in the direction called for, no undesirable results will occur, and controlling the kiln speed in response to said control signal when the measured oxygen concentration in the kiln exit gases is less than a preset low limit established for that concentration when the change in fuel feed rate called for is one which would tend to result in an increase in the temperature of said material, whereby undesirable results from changing the fuel feed rate are avoided.
Claim 37
Independent Claim
164 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: developing a control signal indicative of the magnitude and direction of change necessary for the fuel feed rate to tend to maintain said temperature at its desired value, measuring the carbon monoxide concentration in the exit gases of said kiln, controlling said fuel feed rate in response to said control signal when the conditions of the kiln process are such that upon a change in fuel feed rate in the direction called for, no undesirable results will occur, and controlling the kiln speed in response to said control signal when the carbon monoxide concentration in the exit gases of the kiln are of magnitude above a predetermined limit value when the change in the fuel feed rate called for is one which is intended to result in an increase in the temperature of said material, whereby undesirable results from changing the fuel feed rate are avoided.
Claim 38
Independent Claim
164 words
The method for controlling the temperature of material being processed in a rotary kiln comprising the steps of: developing a control signal indicative of the magnitude and direction of change necessary for the fuel feed rate to tend to maintain said temperature at its desired value, measuring the carbon monoxide concentration in the exit gases of said kiln, controlling said fuel feed rate in response to said control signal when the conditions of the kiln process are such that upon a change in fuel feed rate in the direction called for, no undesirable results will occur, and controlling the kiln speed in response to said control signal when the carbon monoxide concentration in the exit gases of the kiln are of magnitude above a predetermined limit value when the change in the fuel feed rate called for is one which is intended to result in an increase in the temperature of said material, whereby undesirable results from changing the fuel feed rate are avoided.
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) | 1974-02-22 | 1974-08-24 | 1975-02-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-02-22 | 1978-08-24 | 1979-02-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-02-22 | 1982-08-24 | 1983-02-23 | $7700.00 | Window Closed / Lapsed |