Patent US5329443A successfully refreshed from Google Patents.
US5329443A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Two-phase method for real time process control
Assignee: Praxair Technology Inc
•
Filing: 1992-06-16
•
Granted: 1994-07-12
•
Expires: 2012-06-16
Abstract
Abstract A method of process control using linear programming models to implement the control of one or more controlled variables to maintain a desired target value over a given time horizon. The controlled variables are controlled by a process controller which adjusts manipulated variables in real time. The method uses two linear programming models with the second model computed from the solution of the first in which the absolute value of the deviation for each controlled variable from its target value over a specified time horizon is computed. This permits the controlled variables to be adjusted with the changes in the manipulated variables held to a minimum over the time horizon under control.
Inventors
- 👤 Dante P. Bonaquist
- 👤 Michael D. Jordan
- 👤 Mark H. Karwan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:38
CPC Classifications
G; G05; G05B; G05B13/00; G05B13/02; G05B13/04; G05B13/048; F; F25; F25J; F25J3/00; F25J3/02; F25J3/04; F25J3/044; F25J3/04763; F25J3/04769; F25J3/04848; G05B13/042; F25J2290/00; F25J2290/10
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
279 words
A method for controlling a process for separating air into high purity gas streams having one or more manipulated variables in which one manipulated variable is an air flow stream and one or more controlled variables with one of the controlled variables being the degree of purity of a discharge gas stream and having target values which depend upon the adjusted value of said manipulated variables, with the process controlled in real time using a process controller under the operation of a computer comprising the steps of: establishing a first performance index to compute the absolute value of the deviation for each controlled variable in the process from its target value over a specified time horizon: generating a first linear programming model the solution of which will minimize said first performance index; solving said first linear programming model; establishing a second performance index to compute the absolute change in the value of each manipulated variable from its previous value over a specified time interval; generating a second linear programming model the solution of which will minimize said second performance index; incorporating at least one dynamic constraint in said second linear programming model computed from the solution of said first linear programming model and being equal to a value above zero and of no greater than the value of the solution of said first linear programming model plus a predetermined amount; solving said second linear programming model with said dynamic constraint; and adjusting the manipulated variables in response to the solution of said second linear programming model to drive said controlled variables toward their target values and thereby causing the air to be separated into a high purity gas stream.
Claim 2
Independent Claim
279 words
A method for controlling a process for separating air into high purity gas streams having one or more manipulated variables in which one manipulated variable is an air flow stream and one or more controlled variables with one of the controlled variables being the degree of purity of a discharge gas stream and having target values which depend upon the adjusted value of said manipulated variables, with the process controlled in real time using a process controller under the operation of a computer comprising the steps of: establishing a first performance index to compute the absolute value of the deviation for each controlled variable in the process from its target value over a specified time horizon: generating a first linear programming model the solution of which will minimize said first performance index; solving said first linear programming model; establishing a second performance index to compute the absolute change in the value of each manipulated variable from its previous value over a specified time interval; generating a second linear programming model the solution of which will minimize said second performance index; incorporating at least one dynamic constraint in said second linear programming model computed from the solution of said first linear programming model and being equal to a value above zero and of no greater than the value of the solution of said first linear programming model plus a predetermined amount; solving said second linear programming model with said dynamic constraint; and adjusting the manipulated variables in response to the solution of said second linear programming model to drive said controlled variables toward their target values and thereby causing the air to be separated into a high purity gas stream.
Claim 3
Dependent Claim
129 words
A method defined in claim 1 further comprising: using said second performance index for defining an objective function for said first performance index as follows: ______________________________________
Minimize
##STR6##
Minimize
##STR7##
wherein:
α.sup.p .sub.t+n
= positive deviation of controlled variable
p from target at time t + n;
β.sup.p .sub.t+n
= negative deviation of controlled variable
p from target at time t + n;
s.sup.p .sub.t+n
= weight on deviation of controlled variable
p from target at time t + n;
u.sup.r .sub.t+ n
= positive change in manipulated variable
r at time t + n;
v.sup.r .sub.t+n
= negative change in manipulated variable
r at time t + n; and
w.sup.r .sub.t+n
= weight on changes in manipulated variable
r at time t + n
ε > 0.
______________________________________
Claim 4
Dependent Claim
27 words
A method as defined in claim 2 wherein said predetermined value is a fraction of the value of the solution of the first phase linear programming value.
Claim 5
Dependent Claim
60 words
A method as defined in claim 2 wherein said predetermined value is computed as follows: ΔIAE.sup.P =(N)Δ.sup.P ( 119) Where: N number of time intervals considered in the controller time horizon Δ P increase in the contribution to phase one performance index from deviations from the target value of controlled variable p per time interval allowed for phase two solution.
Claim 6
Independent Claim
18 words
A method as defined in 3 wherein said specified time horizon covers a predetermined number of time intervals.
Claim 7
Independent Claim
18 words
A method as defined in 3 wherein said specified time horizon covers a predetermined number of time intervals.
Claim 8
Dependent Claim
38 words
A method as defined in claim 5 further comprising implementing only the manipulated variable charge corresponding to the first element in the time sequence of manipulated variable changes derived from the solution of said second linear programming model.
Claim 9
Dependent Claim
31 words
A method as defined in claim 6 further comprising measuring the current state of the process . defined by the most recent values for all variables including controlled and manipulated variables.
Claim 10
Dependent Claim
25 words
A method as defined in claim 7 wherein external unmeasured disturbances in each time interval will cause the state of the process to be modified.
Claim 11
Dependent Claim
36 words
A method as defined in claim 8 wherein the steps of solving said first linear programming model and said second linear programming model are repeated each time interval based on the updated state of the process.
Claim 12
Dependent Claim
52 words
A method as defined in claim 9 wherein the process being controlled is a process for separating air into high purity gas streams with one of the controlled variables being the degree of purity of a discharged gas stream and wherein one of the manipulated variables is the air flow feed stream.
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) | 1997-07-11 | 1998-01-10 | 1998-07-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-07-11 | 2002-01-10 | 2002-07-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-07-11 | 2006-01-10 | 2006-07-12 | $7700.00 | Window Closed / Lapsed |