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Studies on plantwide control
, 2000
"... Most (if not all) available control theories assume that a control structure is given at the outset. They therefore fail to answer some basic questions that a control engineer regularly meets in practice (Foss 1973): “Which variables should be controlled, which variables should be measured, which i ..."
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Most (if not all) available control theories assume that a control structure is given at the outset. They therefore fail to answer some basic questions that a control engineer regularly meets in practice (Foss 1973): “Which variables should be controlled, which variables should be measured, which inputs should be manipulated, and which links should be made between them? ” These are the question that plantwide control tries to answer. There are two main approaches to the problem, a mathematically oriented approach (control structure design) and a process oriented approach. Both approaches are reviewed in the paper. Emphasis is put on the selection of controlled variables, and it is shown that the idea of “selfoptimizing control ” provides a link between steadystate optimization and control. We also provide some definitions of terms used within the area of plantwide control. This paper is an unpublished internal report which was written as part of the European Union CAPE.NET
Plantwide control – A review and a new design procedure
, 2000
"... Most (if not all) available control theories assume that a control structure is given at the outset. They therefore fail to answer some basic questions that a control engineer regularly meets in practice (Foss 1973): “Which variables should be controlled, which variables should be measured, which in ..."
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Cited by 4 (3 self)
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Most (if not all) available control theories assume that a control structure is given at the outset. They therefore fail to answer some basic questions that a control engineer regularly meets in practice (Foss 1973): “Which variables should be controlled, which variables should be measured, which inputs should be manipulated, and which links should be made between them? ” These are the questions that plantwide control tries to answer. There are two main approaches to the problem, a mathematically oriented approach (control structure design) and a process oriented approach. Both approaches are reviewed in the paper. Emphasis is put on the selection of controlled variables (“outputs”), and it is shown that the idea of “selfoptimizing control ” provides a link between steadystate optimization and control. We also provide some definitions of terms used within the area of plantwide control.
A Neurocontrol Paradigm for Intelligent Process Control using Evolutionary Reinforcement Learning
"... I, the undersigned, hereby declare that the work contained in this thesis is my own original work and has not previously in its entirety or in part been submitted at any university for a degree. Alex van Eck Conradie December 2004 © Copyright University of Stellenbosch, 2004 iiNow to Him who is able ..."
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I, the undersigned, hereby declare that the work contained in this thesis is my own original work and has not previously in its entirety or in part been submitted at any university for a degree. Alex van Eck Conradie December 2004 © Copyright University of Stellenbosch, 2004 iiNow to Him who is able to keep us from stumbling, And to bring us faultless Before the presence of His glory with exceeding joy, To God our Saviour, Who alone is wise, Be glory and majesty, Dominion and power, Both now and forever. Amen.
Improved Branch and Bound Method for Control Structure Screening
"... The main aim of this paper is to present an improved algorithm of “Branch and Bound ” method for control structure screening. The new algorithm uses a bestfirst search approach, which is more efficient than other algorithms based on depthfirst search approaches. Detailed explanation of the algorit ..."
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The main aim of this paper is to present an improved algorithm of “Branch and Bound ” method for control structure screening. The new algorithm uses a bestfirst search approach, which is more efficient than other algorithms based on depthfirst search approaches. Detailed explanation of the algorithms is provided in this paper along with a case study on TennesseeEastman process to justify the theory of Branch and Bound method. The case study uses the Hankel Singular Value to screen control structure for stabilization. The branch and bound method provides a global ranking to all possible input and output combinations. Based on this ranking an efficient control structure with least complexity for stabilizing control is detected which leads to a decentralized proportional controller.
modeling, identification and control, 2000, vol.21, no.4, 209–240 Plantwide control—A review and a new design procedure
"... challenge process Most (if not all) available control theories assume that a control structure is given at the outset. They therefore fail to answer some basic questions that a control engineer regularly meets in practice (Foss 1973): ‘Which variables should be controlled, which variables should be ..."
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challenge process Most (if not all) available control theories assume that a control structure is given at the outset. They therefore fail to answer some basic questions that a control engineer regularly meets in practice (Foss 1973): ‘Which variables should be controlled, which variables should be measured, which inputs should be manipulated, and which links should be made between them? ’ These are the questions that plantwide control tries to answer. There are two main approaches to the problem, a mathematically oriented approach (control structure design) and a process oriented approach. Both approaches are reviewed in the paper. We also provide some definitions of terms used within the area of plantwide control. 1
Interaction of Design and Control: Optimization with Dynamic Models
, 1997
"... Process design is usually approached by considering the steadystate performance of the process based on an economic objective. Only after the process design is determined are the operability aspects of the process considered. This sequential treatment of the process design problem neglects the fact ..."
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Process design is usually approached by considering the steadystate performance of the process based on an economic objective. Only after the process design is determined are the operability aspects of the process considered. This sequential treatment of the process design problem neglects the fact that the dynamic controllability of the process is an inherent property of its design. This work considers a systematic approach where the interaction between the steadystate design and the dynamic controllability is analyzed by simultaneously considering both economic and controllability criteria. This method follows a process synthesis approach where a process superstructure is used to represent the set of structural alternatives. This superstructure is modeled mathematically by a set of differential and algebraic equations which contains both continuous and integer variables. Two objectives representing the steadystate design and dynamic controllability of the process are considered. T...
Control of Reactor and Separator, with Recycle
, 1999
"... This paper looks at control of a plant that consists of a reactor, separator and recycle of unreacted reactant. This configuration is very common in industry, and includes both liquid phase and gas phase systems. Some examples of gas phase systems are ammonia and methanol plants. For example, consid ..."
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This paper looks at control of a plant that consists of a reactor, separator and recycle of unreacted reactant. This configuration is very common in industry, and includes both liquid phase and gas phase systems. Some examples of gas phase systems are ammonia and methanol plants. For example, consider a CSTR reactor where component A is converted to a product and the amount converted is given by k(T)Mz [moleA=s]. To increase the conversion one then has three options: 1. Increase the temperature which increases the reaction constant k 2. Increase the fraction of A in the reactor, z. This can be done indirectly by increasing the amount of recycle of A. 3. Increase the reactor holdup M. In a liquid phase system the reactor holdup is determined by the reactor level, and in a gas phase system by the reactor pressure. Here we will assume that the temperature is constant. Since at steadystate with given product specifications the conversion of A in the reactor is given by the feed rate, it follows that only one of the two remaining variables mentioned above can be controlled independently (or more generally, one variables that influences these variables), and we must let the second variable ”float ” and
T. Larsson, S. Skogestad, C.C. Yu Control of reactor, separator with recycle.
"... Control of reactor, separator with recycle. Liquid phase system gas phase systems methanol synthesis loop ..."
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Control of reactor, separator with recycle. Liquid phase system gas phase systems methanol synthesis loop
Author's personal copy Available online at www.sciencedirect.com Computers and Chemical Engineering 32 (2008) 1373–1384 A path constrained method for integration of process design and control
, 2007
"... Integration of process design and control (IPDC) has been the holy grail of process systems engineering since the introduction of heat and mass integration. A proper combination of these separate yet connected tasks carries the promise of achieving superior designs that cannot be realized with conve ..."
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Integration of process design and control (IPDC) has been the holy grail of process systems engineering since the introduction of heat and mass integration. A proper combination of these separate yet connected tasks carries the promise of achieving superior designs that cannot be realized with conventional procedures. In this work, a bilevel dynamic optimization approach is introduced for achieving IPDC in its true sense. The principal idea proposed here is to utilize an optimal controller (a modified linear quadratic regulator) to practically evaluate the best achievable control performance for each candidate design during process design. The evaluation of complete, closedloop system dynamics can then be meshed with a superstructurebased process design algorithm, thus enabling considering both cost and controllability in design of a process. The practicality of the introduced approach enables a solution of this complex dynamic optimization problem within reasonable computational requirements, as demonstrated in an evaporator case study. © 2007 Elsevier Ltd. All rights reserved.