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Closed-Loop Identification of State Space Models using Subspace Techniques

IFAC Proceedings Volumes 1997年第9期30卷 37-42页

作者： Hemant Jha Christos Georgakis Chemical Process Modeling and Control Research Center and Department of Chemical Engineering Lehigh University Bethlehem Pennsylvania 18015 Phone: (610)-758-5432 Fax:(610)-758-5297

The paper presents a subspace algorithm which identifies the process model from closed-loop data. The algorithm is based on the use of a closed-loop oblique projection for the direct identification of the plant dynamics. This closed-loop oblique projection is particularly useful because it eliminates the use of a minimal realization step after the identification has been performed. Similar to the open-loop algorithm, the proposed closed-loop algorithm is ideally suited for MIMO problems.

关键词： Closed-loop Identification Subspace Methods State Space Models Multivariable Systems Matrix Projection

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Digital Monitoring, Estimation and control of Emulsion Copolymerization

Digital Monitoring, Estimation and Control of Emulsion Copol...

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American control Conference (ACC)

作者： J. Dimitratos C. Georgakis M. S. El-Aasser A. Klein Chemical Process Modeling and Control Research Center & Emulsion Polymers Institute Lehigh University Bethlehem PA USA

The application of Kalman filtering theory to address the problem of composition control in emulsion copolymerization is investigated. Two different filter designs were implemented carrying out standard state and noise-adaptive state estimation. Satisfactory digital monitoring of the process was obtained with both schemes. The filter estimates were utilized by a deterministic controller regulating the monomer addition rates of the two monomers into a reactor operating in semicontinuous fashion. The quality control strategy was based on a model developed for the vinyl acetate (VAc)/ butyl acrylate (BuA) comonomer system. Real-time experiments demonstrated the efficiency of the approach to minimize drastically the compositional drift.

关键词： Monitoring Filters Inductors Open loop systems State estimation Statistics chemical processes process control Quality control Feeds

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A Method for Assessing the Effects of Design Parameters on controllability

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IFAC Proceedings Volumes 1994年第7期27卷 85-91页

作者： P.R. Lyman W.L. Luyben Chemical Process Modeling and Control Research Center Department of Chemical Engineering Lehigh University Bethlehem Pennsylvania USA 18015 Phone:(610)758-4256 Fax:(610)758-5297

A method is presented for identifying process design modifications that improve process controllability. The methodology includes the use of designed experimentation to examine multiple design and control factors simultaneously. Each trial within the designed experiment includes estimation of the capital and operating costs and quantification of the controllability. A recycle process is used in an example of the method. The method reveals that the size of the reactor has a large influence on the controllability and the control structures in combination with the other factori show potential for dynamic response improvement. Physical arguments are used to explain these observations.

关键词： Computer simulation control system analysis control system design dynamic response simulation sensitivity analysis

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Synthesis of stabilizing anti-windup controllers using piecewise quadratic Lyapunov functions

Synthesis of stabilizing anti-windup controllers using piece...

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American control Conference (ACC)

作者： E.F. Mulder M.V. Kothare Chemical Process Modeling and Control Research Center Department of Chem. Eng Lehigh University Bethlehem PA USA

We consider the problem of multivariable anti-windup bumpless transfer (AWBT) controller synthesis based on the general AWBT framework presented by Kothare et al. (1994). Specifically, we propose a method for synthesizing AWBT compensators which stabilize linear time-invariant systems subject to saturating actuators. Our synthesis approach takes advantage of the fact that the AWBT system is a piecewise affine system and thus, we can utilize piecewise quadratic Lyapunov function theory to determine a stabilizing control law. The synthesis problem is solved via iteration between a set of linear matrix inequalities. The utility of the approach is demonstrated on a simple example where our method is shown to be less conservative.

关键词： control system synthesis Stability analysis Lyapunov method process control Piecewise linear techniques control systems Symmetric matrices chemical processes Time invariant systems Linear matrix inequalities

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Multivariable Anti-Windup controller Synthesis incorporating Multiple Convex Constraints

Multivariable Anti-Windup Controller Synthesis incorporating...

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American control Conference (ACC)

作者： Pradeep Y. Tiwari Eric F. Mulder Mayuresh V. Kothare Chemical Process Modeling and Control Center Department of Chemical Engineering Lehigh University Bethlehem PA USA Exxon-Mobil Chemical Baytown TX USA

We study the problem of multivariable anti-windup controller synthesis that incorporates trade-offs between unconstrained linear performance and constrained anti- windup performance. In our previous work [13], we presented a framework for simultaneous design of a linear output feedback controller and a static anti-windup compensator using Linear Matrix Inequalities (LMIs). This framework deviated from the conventional two step paradigm of anti-windup by proposing a one-step synthesis while still maintaining the anti-windup structure. However, the work in [13] did not provide conclusive demonstration of the efficacy of this formulation through realistic practical examples. In this paper, we further study the framework in [13] and explicitly demonstrate its capability in providing effective constrained anti-windup controller performance for two benchmark problems, viz. a vibration isolation table and a multivariable model for the longitudinal dynamics of an F8 aircraft.

关键词： chemical processes chemical engineering Aircraft Design methodology process control Cities and towns Output feedback Linear feedback control systems Linear matrix inequalities Vibration control

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Independent Single-input-single Output control Schemes for Dual Composition control of Binary Distillation Columns

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IFAC Proceedings Volumes 1986年第15期19卷 249-253页

作者： A.C. Kridiotis Christos Georgakis Department of Chemical Engineering Massachusetts Institute of Technology Cambridge MA 02139 USA Chemical Process Modeling and Control Research Center Lehigh University Bethlehem PA 18106 USA

The steady-state interaction measure of dual composition control schemes for binary distillation columns is examined under the assumptions of constant relative volatility and constant molar overflow. An exhaustive enumeration is made of the control schemes that use column flows or their ratios as manipulated variables and product compositions as the controlled variables. Using a redundancy criterion, it is shown that 34 classes of dual composition control schemes have independent values for the interaction measure. This number reduces to 17 when the feed is a saturated liquid or gas. For high purity columns, the interaction measure of the above 34 control schemes approaches the values for the (L, V), (D, V), and (L3) control schemes. In this case none of the control schemes has a desirable interaction measure.

关键词： Distillation control Interaction Measure Multivarable control process control Decoupling

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Nonlinear reduced order models for separation processes via augmentation of linear subspace models

Nonlinear reduced order models for separation processes via ...

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American control Conference (ACC)

作者： W.A. Docter C. Georgakis Chemical Process Modeling and Control Research Center and Department of Chemical Engine Lehigh University Bethlehem PA USA D311 Iacocca Hal Bethlehem PA

This paper presents a general methodology for developing nonlinear low-order model (NLLOM) from data collected from large detailed nonlinear models. This methodology is divided into two tasks: development of an average linear low-order model (ALLOM) and augmentation of the ALLOM with selected nonlinear terms to form the NLLOM. The tools required for the augmentation step that is the focus of this paper include stepwise regression and nonlinear optimization. Results will be presented for the application of these techniques in the development of an NLLOM from a detailed high purity air separation distillation column model supplied by Praxair, Inc.

关键词： Separation processes Predictive models Solid modeling Integrated circuit modeling Discrete Fourier transforms chemical processes process control chemical engineering Distillation equipment Thermodynamics

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The Effects of Operational and Design Characteristics of Catalytic Cracking Reactors on the Closed-Loop Performance of Linear Model Predictive controllers

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IFAC Proceedings Volumes 1994年第7期27卷 209-214页

作者： Lokesh Kalra Christos Georgakis Chemical Process Modeling and Control Research Center and Department of Chemical Engineering Lehigh University Bethlehem Pennsylvania 18015 USA Phone:(610)758-543t Fax:(610)758-5t97

In closed-loop simulations of the catalytic cracker, it was observed that the model identified at a low throughput operating point, when used in MPC did a better job on the high throughput operating point than a model identified at the latter operating point. At the same time MPC utilising a model identified at a high throughput operating point did not perform well when used at the low throughput operating points. In this paper we examine this behavior through an analysis of the closed-loop catalytic cracker under unconstrained MPC. The persistent appearance of an upward spike in stack carbon monoxide concentrations immediately following a disturbance, despite extensive tuning efforts suggests that it is due to process rather than control system design characteristics. At high throughput operating points this phenomenon is of concern because it seriously impairs the ability of a control system to keep CO below its upper constraint. In the paper we trace the source of this dynamic behavior to the design of the catalytic cracker and suggest modifications that may favorably affect control performance.

关键词： Catalytic Cracking Model Predictive control Nonlinear control

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Studies in plant-wide controllability using the Tennessee Eastman Challenge problem, the case for multivariable control

Studies in plant-wide controllability using the Tennessee Ea...

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American control Conference (ACC)

作者： D.R. Vinson C. Georgakis J. Fossy Air Products and Chemicals Inc. Allentown PA USA Chemical Process Modeling and Control Research Center and Department of Chemical Engineering Lehigh University Bethlehem PA USA

The design and application of a new control structure for the Tennessee Eastman Challenge process is presented. This structure is primarily single-input single-output (SISO) but it has been augmented with the concept of extensive variable control to intuitively design multivariable structures for the regulation of the production rate and the product purities. A review of plant-wide control methodologies is provided to lay the basis for a discussion of SISO versus multivariable approaches.

关键词： controllability Computer aided software engineering control systems process design chemical products chemical processes process control Steady-state Recycling Production systems

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Robust synthesis of constrained linear state feedback using LMIs and polyhedral invariant sets

Robust synthesis of constrained linear state feedback using ...

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American control Conference (ACC)

作者： B. Pluymers M.V. Kothare J.A.K. Suykens B. De Moor Department of Electrical Engineering ESAT-SCD-SISTA Katholieke Universiteit Leuven Belgium Chemical Process Modeling and Control Research Center Lehigh University Bethlehem PA USA

This paper deals with the synthesis of linear feedback controllers for constrained discrete-time linear systems with polytopic uncertainty description. This problem was initially tackled using ellipsoidal robust invariant sets in the paper by Kothare (Kothare et al., Automatica, 1996) leading to an LMI-based optimization problem. The contribution of this paper is twofold. First the aforementioned method is extended to also take into account mixed state/input constraints and cross-terms between states and inputs in the objective function. Secondly, polyhedral invariant sets (Pluymers et al., ACC, 2005) are introduced in the synthesis algorithm in order to eliminate conservative constraint handling. This results in a provably more optimal feedback controller. The resulting method can either be used on-line in a receding horizon fashion to obtain a robust constrained controller or off-line in order to obtain a feedback controller with a guaranteed feasible region for use in dual-mode or other robust model-based predictive control algorithms. A numerical example is given to illustrate the new algorithm

关键词： Robustness State feedback Adaptive control control system synthesis Robust control Linear systems Uncertainty Predictive models Predictive control Prediction algorithms

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