Passivity based controller and observer of exothermic chemical reactors (original) (raw)
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The problem of controlling exothermic continuous chemical reactors with non-monotonic reaction rate and temperature measurement is addressed within a dissipativity-passivity theoretical framework, yielding an output-feedback dynamic controller made of a nonlinear passive state-feedback controller combined with a nonlinear dissipative observer. The proposed approach is put in perspective with previous nonlinear controllers and is illustrated with a representative example through simulations.
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Annual Reviews in Control, 2013
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Output-feedback dissipative control of exothermic continuous reactors
7th IFAC International Symposium on Advanced Control of Chemical Processes (2009), 2009
The problem of controlling a (possibly open-loop unstable) continuous exothermic reactor with temperature measurements and manipulation of reactant feed and heat exchange rates is addressed within a passivity-dissipativity framework. The combination of a nonlinear passive state-feedback (SF) controller with a dissipative observer yields the dissipative outputfeedback (OF) controller closed-loop stability conditions with: (i) the identification of the underlying gain-behavior interplay, and (ii) simple tuning guidelines. The approach is tested through numerical simulations, with a representative worst-case example: an exothermic reactor with Langmuir-Hinshelwood nonmonotonic kinetics, which must be regulated about an openloop unstable steady-state which is not observable.
A finite dimensional nonlinear observer for an exothermic stirred-tank reactor
Chemical Engineering Science, 1989
A finite dimensional nonlinear observer is constructed to provide an exponentially convergent estimate of reactant concentration from temperature measurements in an exothermic stirred-tank reactor &th a single, first-order, irreversible reaction. The observer is suitable for batch or continuous reactor operation when the reactor is subject to measured time-varying feed and coolant temperature fluctuations. The construction of a nonlinear observer for this process is an unexpected result due to the very narrow class of nonlinear systems for which such observers are known to exist. The paper presents explicit.formulae for the observer. The required nonlinear observer gains are obtained by straightforward numerical quadratures. Preliminary simulation results demonstrate the utility of the observer in implementing nonlinear state feedback controt. Extension to other reaction systems or to the case of unmeasured time-varying feed concentration will require additional theoretical development.
Nonlinear adaptive observation of an exothermic stirred-tank reactor
Chemical Engineering Science, 1991
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Lyapunov based control for non isothermal continuous stirred tank reactor
IFAC Proceedings Volumes, 2008
In this contribution we apply the approach of passivity proposed by Ydstie [M. Ruszkowski, V. Garcia-Osorio, and B.E. Ydstie. AIChE Journal, 2005] for physico-chemical processes. The originality of this work lies in the fact we consider a thermodynamically nonlinear consistent model for a continuous stirred tank reactor to built the appropriate Lyapunov function for stabilization purpose. Indeed the kinetics of reaction modelled by Arhenius law leads to non linear model with multiple steady state. We propose to stabilize the reactor around the unstable point. In order to apply the Ydstie approach, we assume that the fluid remains homogeneous. This assumption permits to use the concavity property of the entropy function to build the Lyapunov function. We propose feedback laws in order to ensure the closed loop properties of the Lyapunov function. Finally we propose some simulation results.
Feedforward output-feedback control for continuous exothermic reactors with isotonic kinetics
Journal of Process Control, 2012
The robust feedforward (FF) output-feedback (OF) control problem of (possibly open-loop unstable) continuous exothermic jacketed reactors with isotonic kinetics with respect to reactant concentration is considered. The volume, temperature, and concentration must be regulated by manipulating the feed, exit and coolant flowrates on the basis of volume and temperature measurements. The problem is addressed as an interlaced controller-observer design within a constructive control framework. The result is a quasi linear-decentralized (qLD) FF-OF dynamic controller which: (i) recovers (up to observer convergence) the behavior of a robust nonlinear FF-SF controller, (ii) has closed-loop stability conditions coupled with conventional-like tuning guidelines, and (iii) constitutes an add-on to the PI control scheme commonly employed in industrial reactors. The approach is tested with an open-loop unstable reactor example through simulations. Interlaced estimator-control design for continuous exothermic reactors with nonmonotonic kinetics", IFAC-DYCOPS 2007 Preprints (III): 43-48 (2007). j Jacket density (kg/L) m Reactor mixture density (kg/L) Volumetric contraction rate (L/min) where States:
Transactions of the Institute of Measurement and Control
Exothermic chemical reaction taking place in continuous stirred tank reactor is considered. Heat release from the chemical reaction, non-linear dynamic behavior of the process and uncertainty in parameters are the main factors motivating the use of robust control design. Viewing temperature and molar concentration as variables both accessible in real time, PI and optimal state-feedback controllers driven by temperature and concentration error signals are proposed to regulate the system over reactor’s steady-state working points by counteracting undesired disturbances. Since access to concentration value has proved beneficial for the reactor’s performance, estimation techniques are examined to compensate for the problematic nature of the concentration’s measurement. A linear reduced-order observer is first proposed to estimate the concentration value using temperature measurements. In addition, assuming concentration measurement is available with a relatively short delay via sample a...
Nonlinear Observer Design with Application to Chemical Reactors
Dynamics and Control of Chemical Reactors, Distillation Columns and Batch Processes (Dycord'95), 1995
This study concerns the problem of nonlinear state observer design. It presents a non linear observer design approach , which allows to adjust the rate of the decay of observer error and is easy to use. Furthermore, in many chemical engineering cases, it is straightforward to prove that the observer-error dynamics is globally asymptotically stable. Two classes of chemical reactors (classical chemical reactors with parallel reactions and free-radical polymerization reactors) are considered to illustrate the application of the observer design approach. The global asymptotic stability of the observer-error dynamics is proved for the two classes of processes.
Journal of Process Control, 2012
In this paper, the thermodynamic availability function is used as a Lyapunov function for the practical derivation of non linear control laws for the stabilization of a large class of CSTRs far from the equilibrium. The strict convexity of the availability function is guaranteed as long as one of the extensive variables is fixed. In this study, we consider liquid mixture with constant volume, the constraint on the volume being insured by perfect regulation of the outlet flow of the CSTR. Several control laws are then derived which insure global asymptotic stability, exponential stability or simple asymptotic stability. These control laws are discussed regarding the magnitude and the dynamic variations of the control variable. It is shown that the availability function can be split into two parts: one corresponds to the mixing term and depends on mole numbers only and the other depends on both temperature and mole numbers. The two parts are positive and the second one is chosen as a new Lyapunov function. The use of this new Lyapunov function insures smooth variations of the control variable. An exothermal, first order chemical reaction leading to multiple steady-state operating points of the CSTR illustrates the proposed theory.