Synthesis control system

Operability analysis and control system synthesis for an entire chemical plant Mathematical modeling of transport and chemical reactions of combustion-generated air pollutants... 

Truxal, J. G. Automatic Feedback Control System Synthesis (McGraw-Hill, New York, 1955). 

H.P. Huang, C.C. Chen, Control system synthesis for open-loop unstable processes with time delay, IEE Control Theory Appl. 144 (1997) 334-338. 

Umeda, T., Kuriyama, T., and Ichikawa, A. (1978). A logical structure for process control system synthesis. In Proceedings of the IF AC Congress, Helsinki. 

Zheng, A., Mahajanam, R. V., and Douglas, J. M. (1999). Hierarchical procedure for plantwide control system synthesis. AIChE J., 45, 1255-1265. 

Control System Synthesis. The synthesis problem for control systems is to select the controllers needed to meet specified control goals for a fixed plant configuration. The designer selects his goals by stating which variables he wishes controlled. The synthesis algorithm selects which variables to measure, which to manipulate and what type of controllers to use. 

Umeda and Kuriyama (1978) describe a two level approach to control system synthesis. At the inner level control schemes are developed for each unit in the flowsheet. While these schemes would work for the unit in isolation, they likely will fight each other if used together. Thus an outer level coordinating step examines and modifies these schemes to eliminate undesirable interactions. The two levels of activity are repeated until they both give the same structure. 

Arkun, Stephanopoulos and Morari (1978) have added a new twist to control system synthesis. They developed the theory and then demonstrated on two example problems how to move from one control point to another for a chemical process. They note that the desirable control point is likely at the intersection of a number of inequality constraints, the particular set being those that give optimal steady-state performance for the plant. Due to process upsets or slow changes with time, the point may move at which one wishes to operate. Also, the inequality constraints themselves may shift relative to each other. Arkun, Stephanopoulos and Morari provide the theory to decide when to move, and then develop alternative paths along which to move to the new... 

Govind, R. and Powers, G.J., "Control System Synthesis Strategies," 82nd National Meeting, AIChE, Atlantic City, N. J., August 1976. 

Umeda, T. and Kuriyama, T., "A Logical Structure for Process Control System Synthesis," Proc. IFAC Congress, Helsinki, Finland, 1978. 

In the production laboratory all synthesis and purification processes are carried out in remote-operated fully automated computer-controlled systems (synthesis modules, see Figure 7) located in heavily shielded hot cells (see Figure 8). Dispensing of individual doses is in many cases also carried out by automated systems. 

This is, in essence, the realm of control system synthesis for an entire plant. What issues do we need to consider What is of essential importance within this immense amount of detail How does the dynamic behavior of the interconnected plant differ from that of the individual unit operations What, if anything, do we need to model or test How do we even begin ... 

This book addresses each of these questions and explains the fundamental ideas of control system synthesis. As its core, the book presents a general heuristic design procedure that generates an effective plantwide base-level regulatory control structure for an entire, complex process flowsheet and not simply individual units. 

Answering these questions is not at all a trivial matter. But these issues lie at the foundation of control system synthesis for an entire plant. The plantwide control problem is extremely complex and very much open-ended. There are a combinatorial number of possible choices and alternative strategies. And there is no unique correct" solution. 

Vidyasagar, M., Control System Synthesis A Factorization Approach. MIT Press, Cambridge, MA (1985). 

Truxal, J. G. (1955). Automatic Feedback Control System Synthesis, McGraw-Hill, New York. Umbarger, H. E. (1956). Evidence for a negative-feedback mechanism in the biosynthesis of isoleucine. Science 123, 848. 

By the start of World War II, a new approach to control system synthesis was being developed from Nyquist s theoretical treatment (Nl) of feedback amplifiers in 1932. This approach utilized the response of components and systems to steady-state sinusoidal excitation or frequency response as it is more usually called. The frequency response approach provides an important basis for present-day methods of handling control problems by affording a simply manipulable characterization which avoids the need for obtaining the complete solutions of system equations. 

Control System Synthesis from Frequency Response Characteristics... 

In the absence of other specifications, the problem of control system synthesis is one of adjusting the characteristics of the various loop components until the recommended frequency response characteristics are obtained. All the control components including measuring elements should have negligible lagging and attenuation characteristics over the range of frequencies which are of importance for the control system. The... 

We are only beginning to characterize chemical engineering processes in ways useful for control system synthesis. Only very simple processes have been analyzed with success, and much more work is needed not only in analyzing complex processes but also in developing improved and simplified methods of analysis. Most of the important industrial processes involve distributed parameters, interacting components, and nonlinearities, all of which make the applicability of servomechanism techniques at best an approximation. 

R. Govind and G. J. Powers, Control System Synthesis Strategies, presented at the 82nd AIChE... 

R. Govind, "Control System Synthesis Strategies, Ph.D. Dissertation, Camegie-Mellon Uni-... 

Figure 15.7 Root locus of the reactor in Example 15.7. Reproduced from J.M. Douglas, Process Dynamics and Control. Control Systems Synthesis, Vol. 2, (c) 1972, p. 112. Reprinted by permission of Prentice-Hall, Inc., Englewood Cliffs, N.J.

A Logical Structure for Process Control System Synthesis, by T. Umeda, T. Kuriyama, and A. Ichikawa, in A Link between Science and Applications of Automatic Control, A. Niemi (ed.), Pergamon Press Ltd., Oxford (1979). 

This chapter reviews the philosophy of overall column control system synthesis, examines common practices, outlines their pitfalls, supplies guidelines for avoiding these pitfalls, and discusses the pros and cons of the common control philosophies and their effects on column operation and stability. 

Some ground rules for control system synthesis. The essence of control system s3mthesis is suitable pairing of the five control variables with the five manipulated streams. Theoretically, 5 (= 120) pairing combinations are possible, but only a handful of these are commonly used. The following ground rules can be applied for initial screening out of undesirable combinations ... 

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