Perspectives on the synthesis of plant-wide control structures

George Stephanopoulos, Christine Ng

Research output: Contribution to journalConference articlepeer-review

94 Scopus citations


The synthesis of plant-wide control structures has resurfaced as the most important design problem in process control. In this paper we provide a comparative analysis of various approaches, with an emphasis on how well they address the inherent theoretical and practical issues associated with the design of such control systems. Starting with a formal statement of the problem, which corresponds to a multi-objective optimization problem, this paper argues that the central issue to be resolved is the translation of implicit operating objectives to sets of feedback-controlled variables. The principle of the Optimizing Feedback Control Structures is proposed as the formal medium for the identification of controlled variables. Furthermore, it is shown that the selection of the best sets of input (manipulated) and output (measured) variables for the formation of the controllers' structures is governed by classical control-theoretical aspects, such as; open-loop gains, model uncertainty, and nonminimum-phase process characteristics. Hierarchical viewing of a plant is proposed as an effective mechanism to contain the complexities of the problem by streamlining the (i) specification of control objectives at different time-scales, (ii) modeling needs and model uncertainties, (iii) selection of measured and manipulated variables, and (iv) formation of the control structures.

Original languageEnglish (US)
Pages (from-to)97-111
Number of pages15
JournalJournal of Process Control
Issue number2
StatePublished - Apr 2000
Externally publishedYes
EventThe 5th IFAC Symposium on the Dynamics and Control of Process Systems (DYCOPS-5) - Corfu, Greece
Duration: Jun 8 1998Jun 10 1998

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Modeling and Simulation
  • Computer Science Applications
  • Industrial and Manufacturing Engineering

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