Analysis of Multi-Loop Control Structures of Dividing-Wall Distillation Columns Using a Fundamental Model

A method of controller restructuring is introduced for improved closed-loop control of nonlinear plants. In this method, an initial controller, potentially the linear controller designed according to the linearized model of the plant, is expanded into several candidate nonlinear control structures that are subsequently shaped to achieve a desired closed-loop response. The salient feature of the proposed method is a metric for quantifying structural perturbations to the controllers, which it uses to scale the structural Jacobian for improving its condition number. This improved Jacobian underlies shaping of candidate controllers through gradient-based search. Results obtained from three case studies indicate the success of the proposed restructuring method in finding nonlinear controllers that improve not only the closed-loop response of the nonlinear plant but also its robustness to modeling uncertainty.

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Multi-Loop Model Reference Proportional Integral Derivative Controls: Design and Performance Evaluations

Algorithms ◽

10.3390/a13020038 ◽

2020 ◽

Vol 13 (2) ◽

pp. 38

Author(s):

Baris Baykant Alagoz ◽

Aleksei Tepljakov ◽

Eduard Petlenkov ◽

Celaleddin Yeroglu

Keyword(s):

Pid Control ◽

Disturbance Rejection ◽

Control Performance ◽

Model Reference ◽

Loop Control ◽

Control Structures ◽

Set Point ◽

Control Loops ◽

Point Control ◽

Set Point Control

Due to unpredictable and fluctuating conditions in real-world control system applications, disturbance rejection is a substantial factor in robust control performance. The inherent disturbance rejection capacity of classical closed loop control systems is limited, and an increase in disturbance rejection performance of single-loop control systems affects the set-point control performance. Multi-loop control structures, which involve model reference control loops, can enhance the inherent disturbance rejection capacity of classical control loops without degrading set-point control performance; while the classical closed Proportional Integral Derivative (PID) control loop deals with stability and set-point control, the additional model reference control loop performs disturbance rejection control. This adaptive disturbance rejection, which does not influence set-point control performance, is achieved by selecting reference models as transfer functions of real control systems. This study investigates six types of multi-loop model reference (ML-MR) control structures for PID control loops and presents straightforward design schemes to enhance the disturbance rejection control performance of existing PID control loops. For this purpose, linear and non-linear ML-MR control structures are introduced, and their control performance improvements and certain inherent drawbacks of these structures are discussed. Design examples demonstrate the benefits of the ML-MR control structures for disturbance rejection performance improvement of PID control loops without severely deteriorating their set-point performance.

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Alternative Control Structures for Distillation Columns with Partial Condensers

Industrial & Engineering Chemistry Research ◽

10.1021/ie040146x ◽

2004 ◽

Vol 43 (20) ◽

pp. 6416-6429 ◽

Cited By ~ 7

Author(s):

William L. Luyben

Keyword(s):

Alternative Control ◽

Distillation Columns ◽

Control Structures

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COMPOSITION LINEAR CONTROL IN STIRRED TANK CHEMICAL REACTORS

New Mathematics and Natural Computation ◽

10.1142/s1793005707000859 ◽

2007 ◽

Vol 03 (03) ◽

pp. 385-398 ◽

Cited By ~ 1

Author(s):

A. REGALADO MÉNDEZ ◽

J. ÁLVAREZ-RAMÍREZ

Keyword(s):

Stirred Tank ◽

Chemical Reactors ◽

Loop Control ◽

Control Structures ◽

Composition Control ◽

Reference Implementation ◽

Continuous Stirred Tank ◽

Large Acceptance ◽

Continuous Chemical ◽

Control Composition

This work studies loop control composition in continuous chemical reactors with simple structures, due to its large acceptance in chemical industry. A linear cascade composition control (master/slave) is proposed, designed with basic control structures based on Laplace tools. Two configurations are designed, which were evaluated in a dynamic model of continuous stirred tank. From a stability analysis it is noted that, for such configurations, system assent time is 7 to 8 times reduced if compared to the assent time without loop control. Besides, the system shows a good performance when coming to the asked reference. Implementation of such control configurations can solve the problem of loop control composition.

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Formal Specification of the Assurance Point Web Service Composition Model

International Journal of Cooperative Information Systems ◽

10.1142/s0218843014500075 ◽

2014 ◽

Vol 23 (04) ◽

pp. 1450007

Author(s):

Le Gao ◽

Susan D. Urban ◽

Jonathan Rodriguez ◽

Abhijit Warkhade

Keyword(s):

Web Service ◽

Service Composition ◽

Formal Specification ◽

Web Service Composition ◽

Loop Control ◽

Control Structures ◽

Critical Data ◽

Recovery Techniques ◽

Program Flow ◽

Multiple Levels

This paper presents a formal specification of the Assurance Point (AP) web service composition model. The AP model provides a flexible way of checking constraints and responding to execution errors in service composition. An AP is a combined logical and physical checkpoint, providing an execution milestone that stores critical data and interacts with integration rules (IRs) to alter program flow and to invoke different forms of recovery depending on the execution status. In this paper, the execution and recovery semantics of assurance points have been fully defined in the context of if-else, parallel, and loop control structures. The activities and complex control structures of the AP model have been formalized and tested in the Yet Another Workflow Language (YAWL) engine. By doing so, the correctness of the execution and recovery semantics in the AP model has been verified, demonstrating that YAWL nets of the AP model satisfy the soundness property. Different from existing web service composition models, the AP model presented by this research provides multiple levels of protection against service execution failure with a combination of forward and backward recovery techniques.

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Comparison of Two Types of Two-Temperature Control Structures for Reactive Distillation Columns

Industrial & Engineering Chemistry Research ◽

10.1021/ie058012m ◽

2005 ◽

Vol 44 (13) ◽

pp. 4625-4640 ◽

Cited By ~ 38

Author(s):

Devrim B. Kaymak ◽

William L. Luyben

Keyword(s):

Temperature Control ◽

Reactive Distillation ◽

Distillation Columns ◽

Control Structures ◽

Two Temperature

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Comparing Composition Control Structures for Kaibel Distillation Columns

Processes ◽

10.3390/pr8020218 ◽

2020 ◽

Vol 8 (2) ◽

pp. 218 ◽

Cited By ~ 2

Author(s):

Yang Yuan ◽

Kejin Huang ◽

Haisheng Chen ◽

Xing Qian ◽

Lijing Zang ◽

...

Keyword(s):

Control Systems ◽

Distillation Column ◽

Tight Control ◽

Distillation Columns ◽

Control Structures ◽

Control Loops ◽

Composition Control ◽

Equipment Investment ◽

Quaternary Mixture ◽

Operation Cost

Although Kaibel distillation columns are superior to conventional distillation sequences owing to smaller equipment investment and operation cost, they display high nonlinearity and this greatly increases the difficulty of achieving their tight control. To overcome this problem, four decentralized composition control structures, i.e., the CSR/QR, CSR/B, CSD/QR, and CSD/B structures, are proposed and compared based on the control of a Kaibel distillation column fractionating a methanol/ethanol/propanol/butanol quaternary mixture. These four composition control structures all include five composition control loops. While the four of them are employed to maintain the purity of the top, upper sidestream, lower sidestream, and bottom products, the remaining one is employed to minimize the energy consumption of the Kaibel distillation column by maintaining the composition of propanol at the first stage of the prefractionator. Dynamic simulation results show the CSR/QR and CSR/B structures can tightly maintain the purity of the controlled products with a small overshoot and short settling time after facing various disturbances in feed conditions, but the CSD/QR and CSD/B structures lead to oscillatory responses (the latter even shows divergent responses under individual disturbances). At the end of the article, some effective guides for developing composition control systems are given.

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