Hierarchical procedure for plantwide control system synthesis

Zheng, Alex; Mahajanam, Rama V.; Douglas, James M.

doi:10.1002/aic.690450611

Cited by 64 publications

(45 citation statements)

References 31 publications

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“…Because of the large number of variables and a combinatorial growth in the total number of possible control structures with respect to the number of variables, a complete dynamic evaluation of all alternative control structures is impractical for any realistic process. To deal with this disadvantage, several researchers decomposed the problem into a hierarchy of decisions, [206][207][208][209] motivated by Douglas's hierarchical procedure for conceptual process design. 210 In this approach, some alternatives are eliminated according to economic, environmental, or controllability considerations at each level of hierarchy.…”

Section: Sequential Design Methods For Improving the Plant-wide Contromentioning

confidence: 99%

An overview on controllability analysis of chemical processes

2011

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Controllability is one of the most important aspects of chemical process operability, because it can be used to assess the attainable operation of a given process and improve its dynamic performance. The purpose of this article is to outline the main methodologies that have been developed to deal with the assessment of process controllability and the improvement of its controllability characteristics. Several existing controllability assessment methods are reviewed and discussed. For improving the controllability characteristic of a process, there are two main design methods: the optimization-based method and the controllability indices-based anticipating sequential method. Advantages and disadvantages of these techniques are discussed. It has been emphasized that bifurcation analysis, as a powerful nonlinear analysis tool, could provide important guidance for making processes more controllable by eliminating or avoiding some undesirable behaviors of processes. Further challenges and developments in the field of process controllability are identified.

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Section: Sequential Design Methods For Improving the Plant-wide Contromentioning

confidence: 99%

An overview on controllability analysis of chemical processes

2011

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“…Some of these principles are attributed to the authors of this article. A plant-wide hierarchical control strategy has been reported recently in Zheng et al (1999). Its application to the Tennessee Eastman Challenge process (Tyreus, 1999b) very clearly illustrates the power of the method.…”

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confidence: 96%

On defining the partial control problem: concepts and examples

Kothare

Shinnar

Rinard

et al. 1998

Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207)

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Many complex chemical processes having a large number of process variables and poorly understood models can be controlled reasonably well by controlling only a small subset of process variables using an equally small number of manipulated uariables. This is the central premise of this article and is referred to as partial control. Knowing4 or unknowingly, this idea has been and continues to be applied to successfully control numerous complex industrial processes. Despite its widespread use, partial control has never been explicitly formulated. The partial control problem is defined. A number of terms is introduced such as process variable dominance, modelable responses, practicaldegrees of freedom, and sufficiency of partial control. The new framework allows incorporation of both engineering-based decisions and more rigorous theoretical tools to achieve the goals of partial control. A number of practical examples illustrate the applicability of these concepts. IntroductionThe chemical and petrochemical industry is characterized by processes which can be classified as highly complex. This complexity arises from several sources:Process model uncertainty: The development of detailed and accurate models for chemical processes is rarely possible or prohibitively expensive. For example, the kinetics and mechanisms of many chemical reactions are often far too complex to allow an exact mathematical description. As a consequence, the model of the chemical process, which is based on this imperfect understanding of the kinetics, is inherently imperfect and has a large uncertainty associated with it. Inherent process nonlinearity:The steady state and dynamic behavior of chemical processes is generally highly nonlinear, implying the potential existence of complex behavior such as multiple steady states, instabilities, and limit cycles. Linear models are rarely suitable for describing these processes except in an unrealistically narrow operating regime.Correspondence concerning this article should be addressed to M. V. Kotharr. 2456December 2000 ProceAs constraints: The manipulated variables are limited in magnitude due to equipment limitations such as pump and compressor throughput limits and actuator limits. On the other hand, the process states and outputs are constrained to lie between prespecified limits of their reference values; these limits are arising due to stringent product specifications dictated by market demands, safety limits, or environmental regulations on effluent concentrations. The need for minimizing material and energy costs has led to the use of multiple material recycle loops and complex energy management networks. As a result, chemical processes have evolved into highly integrated, and, at times, unmanageable, monolithic systems. Large-scale qstem aspects:The total number of controlled and manipulated process variables is generally large and typically, the former is significantly larger than the latter. It is important to have a methodology to decide which of the large number of process and state varia...

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“…A design that presents optimal steady-state operation at nominal point does not guarantee optimal operation in a real scenario with disturbances (Zheng, et al, 1999) and control design techniques that are based solely on steady-state information can result in poor performance in several cases (Skogestad, et al, 1990) and should be avoided.…”

Section: Motivationmentioning

confidence: 99%

“…Procedures in this category include those described by (Zheng, et al, 1999), (Jørgensen & Jørgensen, 2000), (Zhu, et al, 2000), (Larsson & Skogestad, 2000), (Skogestad, 2000a), (Skogestad, 2000b) (Robinson, et al, 2001), (Wang & McAvoy, 2001), (Vasbinder & Hoo, 2003), (Skogestad, 2004), (Ward, et al, 2006) and (Baldea, et al, 2008).…”

Section: Plantwide Control Design Techniquesmentioning

confidence: 99%

“…A hierarchical procedure for plantwide control synthesis was proposed in (Zheng, et al, 1999), in which the problem is solved not by evaluating all the possible alternatives (exhaustively or by optimization), but rather by its decomposition into a hierarchy of decisions based on process economics, in which the decisions with greater economic impact are considered first and then only the most economically attractive alternatives are kept for the next decisions.…”

Section: Hierarchical Procedures By Zheng Mahajanam and Douglas (1999)mentioning

confidence: 99%

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Plantwide control: a review and proposal of an augmented hierarchical plantwide control design technique.

Godoy¹

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The problem of designing control systems for entire plants is studied. A review of previous works, available techniques and current research challenges is presented, followed by the description of some theoretical tools to improve plantwide control, including the proposal of an augmented lexicographic multi-objective optimization procedure. With these, an augmented hierarchical plantwide control design technique and an optimal multi-objective technique for integrated control structure selection and controller tuning are proposed. The main contributions of these proposed techniques are the inclusion of system identification and optimal control tuning as part of the plantwide design procedure for improved results, support to multi-objective control specifications and support to any type of plant and controllers. Finally, the proposed techniques are applied to industrial benchmarks to demonstrate and validate its applicability.

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Hierarchical procedure for plantwide control system synthesis

Cited by 64 publications

References 31 publications

An overview on controllability analysis of chemical processes

An overview on controllability analysis of chemical processes

On defining the partial control problem: concepts and examples

Plantwide control: a review and proposal of an augmented hierarchical plantwide control design technique.

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