Control‐system design for a chemical process by the root‐locus method

Ellingsen, Walter R.; Ceaglske, N. H.

doi:10.1002/aic.690050109

Cited by 9 publications

(6 citation statements)

References 2 publications

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“…The control of open-loop unstable reactors with P or PD controllers has been investigated by Ellingsen and Ceaglske (1959) and Cheung and Luyben (1979). For a first-order reactor model with temperature measurement lag (cqr) and heat removal lag (iqr) (eq 3), the system cannot be stabilized by P or PI controllers if…”

Section: The Open-loop Unstable Processmentioning

confidence: 99%

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Analysis of valve-position control for dual-input processes

Yu¹,

Luyben²

1986

Ind. Eng. Chem. Fund.

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Section: The Open-loop Unstable Processmentioning

confidence: 99%

“…Therefore, the value of cq and bl must be a fairly small fraction of the system time constant to be controllable (Ellingsen and Ceaglske, 1959; Luyben and Melcic, 1978).…”

Section: The Open-loop Unstable Processmentioning

confidence: 99%

Analysis of valve-position control for dual-input processes

Yu¹,

Luyben²

1986

Ind. Eng. Chem. Fund.

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“…The chemical reactor with an exothermic irreversible reaction is the most important and most frequently studied example. Ellingsen and Ceaglske (1959), in a pioneering paper, used root locus techniques in the s plane to study the control of an open-loop unstable process in a continuous system. They pointed out that neither proportional (P) nor proportionalintegral (PI) controllers can stabilize a second-order system with the transfer function given in eq 1 when b is greater than ^(S) = 7-vüh-jTu…”

mentioning

confidence: 99%

Sampled-Data Control of Second-Order Open-Loop Unstable Processes

Luyben¹

1972

Ind. Eng. Chem. Fund.

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Koppel (1966) studied sampled-data control of first-order processes that are open-loop unstable. This paper extends his work to the case where the open-loop unstable system is second order. When the ratio of stable to unstable time constant is less than unity, the zero in the pulse transfer function is located inside the unit circle in the z plane. Three types of controllers were studied for this case; proportional, pole-zero cancellation, and minimal prototype. When the ratio of the stable to unstable time constant is greater than unity, the zero is greater than 1. Neither proportional control nor pole-zero cancellation can be used in this case. The system can be made closed-loop stable by employing a sampled-data controller that is itself openloop unstable.Processes that are open-loop unstable (unstable when no feedback control is used) present intriguing control problems. These processes occur fairly frequently in the process industries. The chemical reactor with an exothermic irreversible reaction is the most important and most frequently studied example. Ellingsen and Ceaglske (1959), in a pioneering paper, used root locus techniques in the s plane to study the control of an open-loop unstable process in a continuous system. They pointed out that neither proportional (P) nor proportionalintegral (PI) controllers can stabilize a second-order system with the transfer function given in eq 1 when b is greater than ^(S) = 7-vüh-jTu

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“…The two types of solutions compared very well for small step upsets in the system. Aris and Amundson (7) investigated the controllability of the stirred-tank reactor.…”

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confidence: 99%

“…Root-locus methods were used by Ellingsen and Ceaglske (7) to design a control system for a stirred-tank reactor using the linearized reactor equations. They controlled their reactor about both stable and unstable steady states, using either temperature or concentration as the measured variable.…”

mentioning

confidence: 99%