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Journal ArticleDOI

Static Decouplers with P-PI Dual Loop Controllers for Unstable System

02 Apr 2016-Indian Chemical Engineer (Taylor & Francis)-Vol. 58, Iss: 2, pp 172-185
TL;DR: In this article, the applicability of static decoupler followed by tuning of diagonal proportional integral controllers for unstable multivariable process is studied, where the need of static Decoupler for an unstable multi-input two-output system where the conventional decouplers becomes unstable is brought about by using three examples of a two-input-two-output processes.
Abstract: The applicability of static decoupler followed by tuning of diagonal proportional integral controllers for unstable multivariable process is studied. The need of static decouplers for an unstable multivariable system where the conventional decouplers becomes unstable is brought about by using three examples of a two-input two-output processes. Further, dual loop controllers are tuned for the approximated decoupled system. Use of P-PI (Proportional – Proportional and Integral) dual loop control system reduces the overshoot significantly.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors extended the biggest log modulus tuning (BLT) method to unstable two-input-two-output (TITO) systems and applied the Tanttu and Lieslehto method for centralized and decentralized PI controllers.
Abstract: The biggest log modulus tuning (BLT) method is extended to unstable systems. The method is modified to design (i) decentralized Proportional-Integral (PI) controllers and (ii) centralized PI controllers for two-input two-output (TITO) systems. A method is given to specify the value for The internal model controller using Tanttu and Lieslehto method is applied for centralized controller design. The detuning parameter (F) is selected for both the schemes (centralized controller and decentralized controller) to get the value of BLT as +12 dB. Simulation studies are carried out for two TITO systems to evaluate the performance of both the proposed schemes. The centralized controllers produce superior performances and decreased interactions over the decentralized PI controllers. The present method gives robust performances.

2 citations


Cites methods from "Static Decouplers with P-PI Dual Lo..."

  • ...BLT Method for PI Controllers of Unstable Systems 335 INDIAN CHEMICAL ENGINEER Vol. 60 No. 4 December 2018 [24] Dhanya Ram, V. and Chidambaram, M. “Simple Method of Designing Centralized PI Controllers for Multivariable Systems Based on SSGM”, ISA Trans., 56, pp. 252–260 (2015)....

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  • ...[7] Jacob, E.F. and Chidambaram, M., “Design of Controllers for Unstable First-Order Plus Time Delay Systems”, Comput....

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  • ...[25] Besta, C.S. and Chidambaram, M., “Centralized P/PI Control System Design Based on Equivalent Transfer Functions for Unstable TITO Process, in: Industrial and Information Systems, IEEE, Gwalior....

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  • ...[6] Govindakannan, J. and Chidambaram, M., “Two-Stage Multivariable PID Controllers for Unstable Plus Time Delay Systems”, Indian Chem....

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  • ...[30] Valentine, C.C. and Chidambaram, M., “PID Control of Unstable Time Delay System”, Chem....

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References
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Book
01 Jan 1993
TL;DR: This article presents bootstrap methods for estimation, using simple arguments, with Minitab macros for implementing these methods, as well as some examples of how these methods could be used for estimation purposes.
Abstract: This article presents bootstrap methods for estimation, using simple arguments. Minitab macros for implementing these methods are given.

37,183 citations

Journal ArticleDOI
07 Aug 2002
TL;DR: In this paper, the design of PI controllers for systems with interacting loops is discussed, and a new scheme based on modified scalar PI design and static decoupling is developed, in which the frequency characteristic of the coupling between the lower level loops is taken into account.
Abstract: The design of PI controllers for systems with interacting loops is discussed. It is advantageous to deal with the interaction at the loop level, because supervisory control seldom has sufficient bandwidth. A new scheme based on modified scalar PI design and static decoupling is developed, in which the frequency characteristic of the coupling between the lower-level loops is taken into account. This leads to a design method emphasising the trade-off between the individual loop performances and the interaction indices introduced in the paper. The controller is easily implemented, due to its simple configuration based on standard components. A useful observation is that the interaction can be reduced substantially by using set-point weighting. The method is applied to three examples, including a model of a new laboratory system called the quadruple-tank process.

130 citations

Journal ArticleDOI
TL;DR: In this paper, a comparative study of simplified, ideal and inverted decoupling methods is presented, and the stability, robustness and implementation of the three decoupled methods are studied.
Abstract: This paper presents a comparative study of simplified, ideal and inverted decoupling. The stability, robustness and implementation of the three decoupling methods are studied. The structured singular value (SSV) is used to carry out some comparisons. It is demonstrated that robust performance and robust stability of a nominally stable control system are equivalent for the three decoupling methods when the controllers are tuned to obtain identical nominal performance. A relation is derived between the presence of right-half plane (RHP) zeros of a process in series with its simplified decoupler and the instability of the ideal and inverted decouplers for the same process. This paper also describes a potential implementation problem related to the particular structure of the inverted decoupling. Finally, a recapitulative table of the main advantages and limitations of each decoupling method is presented.

115 citations


"Static Decouplers with P-PI Dual Lo..." refers background in this paper

  • ...The three conventional decouplers reported in literature [5] ideal, simplified and inverted are usually used....

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Journal ArticleDOI
TL;DR: In this paper, a method for the independent design of proportionalintegral/proportionalintegral derivative (PI/PID) controllers is proposed based on the equivalent transfer function (ETF) model of the individual loops and the simplified decoupler matrix.
Abstract: A method for the independent design of proportional-integral/proportional-integral derivative (PI/PID) controllers is proposed based on the equivalent transfer function (ETF) model of the individual loops and the simplified decoupler matrix. It is shown that the conventional effective open-loop transfer function (EOTF, derived from the dynamic relative gain array (DRGA)) is equivalent to the ETF (derived from the relative normalized gain array (RNGA) and relative average residence time array (RARTA)). This relation is used to approximate the decoupled process models as ETF models. The simplified decoupler is shown to decompose the multiloop systems into independent loops (multi-single loop systems) with the ETFs as the resulting decoupled process model. The concept of the ETF (perfect control approximation) is validated by introducing the decoupler. Based on the corresponding ETFs, the decentralized PI controllers are designed using the simplified internal model control (SIMC) method. Three simulation exa...

82 citations


"Static Decouplers with P-PI Dual Lo..." refers background in this paper

  • ...1 constituting of input U, output Y, process Gp, decoupler D and controller Gc can be modelled using transfer function model as follows: Y ðsÞ 1⁄4 GpðsÞDðsÞUðsÞ ð1Þ where the simplified decoupler is designed [7, 8] as: d12 ðsÞ 1⁄4 gp;12 ðsÞ gp;11 ðsÞ ; d21 ðsÞ 1⁄4 gp;21 ðsÞ gp;22 ðsÞ ð2Þ...

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  • ...This method is extended to unstable multivariable system by Hazarika and Chidambaram [8]....

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  • ...Double loop controllers for unstable systems using Tanttu and Lieslehto method [3], proposed by Govindakannan and Chidambaram [4], had interactions....

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  • ...Rajapandiyan and Chidambaram [7] designed a simplified decoupler for stable multivariable system based on effective transfer function method....

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Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method for designing multivariable controller is based on ideal decoupler D(s) and PID controller optimization under constraints on the robustness and sensitivity to measurement noise.

71 citations


"Static Decouplers with P-PI Dual Lo..." refers methods in this paper

  • ...Ideal decoupler with an optimization approach was proposed by Jevtovic and Matausek [6] for both stable and unstable systems....

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  • ...Example 2 Transfer function matrix having all elements unstable with equal poles, may contain a positive zero element and a stable pole [6] is considered: Gp 1⁄4 1 ð4s 1Þ ð 0:8s þ 1Þ ð2s þ 1Þ ð s þ 1Þ ðs þ 1Þ 3 ð1:2s þ 1Þe 2s ð1:4s þ 1Þ 2 4 3 5 ð11Þ Fig....

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