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1999 European control Conference, ECC 1999

作者： Stursberg, O. Kowalewski, S. Process Control Laboratory Chemical Engineering Dept. University of Dortmund DortmundD-44221 Germany

ISBN: (纸本)9783952417355

An approximation procedure is presented for a class of hybrid systems in which switching occurs only when the continuous state trajectory crosses thresholds defined by a rectangular partitioning of the state space. The result of the approximation are rectangular automata, a class of hybrid automata for which a numerically robust approximative analysis algorithm exists. Thus, the approximation procedure can be applied when we are interested in the reachability set of a switched continuous system for which a direct analysis is infeasible. The approach is illustrated by application to a simple physical example. As an extension, an algorithm is presented to adjust the accuracy of the approximation to the continuous dynamics by choosing a state space partitioning according to the variation of the vector field. © 1999 EUCA.

关键词： Hybrid systems

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An Industrial Approach to Implementing MPC in Speciality chemical Plant

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IFAC Proceedings Volumes 1999年第2期32卷 6603-6608页

作者： Qiang Zhan Vincent G. Grassi Chemical Process Modeling and Control Center Dept. of Chemical Engineering Lehigh University Bethlehem PA 18015 USA Chemical Process Modeling Center Air Products and Chemicals Inc. 7201 Hamilton Boulevard Allentown PA 18195 USA

Model Predictive control Technology has been successfully applied to industry for more than two decades. Most of the applications appear in refining and petrochemical industry. Relatively few applications could be found in the chemical industry. In this paper, the approach to evaluate the benefit that could be obtained by implementing MPC as a supervisory controller to a specialty chemical plant is explained in detail. The process and the basic plantwide control structures are simulated in Speedup. The plant pie-testing and plant testing are both done in Speedup. DMC+ commercial software is used to identify the linear model from the plant, build the controller, and tune the controller. By using the interface software between Speedup and DMC+, the process operating under DMC+ can be successfully simulated. The benefits from DMC+ can also be clearly identified in the simulation study. Some important issues in this approach are also pointed out.

关键词： Model based control industrial control chemical industry simulation

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A control Performance Index Based on Minimum and Open-Loop Output Variance

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IFAC Proceedings Volumes 1999年第2期32卷 6704-6709页

作者： Stella Bezergianni Christos Georgakis Chemical Process Modeling and Control Research Center and Department of Chemical Engineering Lehigh University 111 Research Drive Bethlehem PA 18015 USA

The need to achieve reliable and effective automatic control systems has directed numerous research efforts towards the development of monitoring and assessment methods of the closed-loop performance. A new controller assessment index, called Relative Variance Index or RVI, is introduced in this work, according to which the closed loop performance is compared with the theoretically best control action (minimum variance control) and no control action. For the estimation of RVI, an identification method is employed to extract the system models and an estimate of the process unit delays. The proposed index, RVI, is in agreement with the classical deterministic closed-loop assessment measures and thus can be utilized for the controller performance evaluation more effectively.

关键词： controller Performance Assessment minimum variance control principal component analysis structure target factor analysis

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Dynamic matrix control of a specialty chemical plant with different plantwide control structures

Dynamic matrix control of a specialty chemical plant with di...

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American control Conference (ACC)

作者： Qiang Zhan V.G. Grassi Chemical Process Modeling and Control Center Department of Chemical Engineering Lehigh University Bethlehem PA USA Chemical Process Modeling Center Air Products and Chemicals Inc. Allentown PA USA

Model predictive control technology has been successfully applied within the industry for more than 20 years. Most of the applications appear in the refining and petrochemicals industry, with few in specialty chemical plant. In this paper DMC+ commercial multivariable control software is evaluated for a specialty chemical process using offline simulation. The relative benefit that can be obtained from DMC+ above and beyond advanced regulatory plantwide control is carefully studied. In this study, DMC+ is built as a supervisory controller on the decentralized SISO plantwide control structure. DMC+ uses the setpoints of PI controllers as the manipulated variables. In this paper, different plantwide control structures are used and the performance of DMC+ on top of all these different plantwide control structures are compared. It will be shown that a well designed regulatory plantwide control structure is necessary to stabilize and linearize the process around some operating point. Good plantwide control design will give a better performance for DMC+.

关键词： chemical industry Predictive models Predictive control chemical technology Industrial control Application software Refining Petrochemicals chemical processes control design

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Pseudolinear neural networks based nonlinear system modeling and control

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IFAC Proceedings Volumes 1999年第2期32卷 5519-5524页

作者： Yongji Wang Gregor Fernholz Sebastian Engell Dept. of Automatic Control Huazhong University of Science and Technology 430074 Wuhan P. R. China Process Control Laboratory Chemical Engineering Department D-44221 Dortmund University Germany

Pseudo-linear neural networks (PNN) based modeling and control strategy for a class of nonlinear dynamic systems is proposed. The training of the PNN is implemented by using a recursive prediction error (RPE) algorithm. The control strategy is based on one-step-ahead prediction, in which a direct controller design for an affine nonlinear system and the second order based optimization for a general nonlinear system are adopted. The stability of the closed loop control system is investigated, and some sufficient conditions for the local asymptotic stability are derived. The some simulated examples showed the good results of proposed control strategies in this paper.

关键词： neural networks predictive control learning algorithms nonlinear system asymptotic stability

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Timed approximations of hybrid processes for controller verification

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IFAC Proceedings Volumes 1999年第2期32卷 4782-4787页

作者： Olaf Stursberg Sebastian Engell Stefan Kowalewski Process Control Laboratory Chemical Engineering Dept. University of Dortmund D-44221 Dortmund Phone: +49 (0)231 9700 351 Fax: +49 (0)231 7555129 (Germany)

The task of verifying the correct (with respect to a given specification) behaviour of discrete event controllers for continuous processes requires to combine model types of continuous and of discrete nature. In this contribution, the verification problem is treated by approximating the continuous dynamics using automata models, and by carrying out a reachability analysis in the discrete domain. The focus is on different methods to generate timed automata and hybrid automata from switched continuous systems. Furthermore, some model properties and their effects on the analysis results are discussed.

关键词： Automata Hybrid systems Discretization Model approximation Linear programming Reachability Verification

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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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1998 American control Conference, ACC 1998

作者： Docter, William A. Georgakis, Christos Chemical Process Modeling and Control Research Center Department of Chemical Engineering Lehigh University 111 Research Drive Bethlehem PA 18015 United States

ISBN: (纸本)0780345304

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. © 1998 AACC.

关键词： Nonlinear programming

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Nonlinear Term Selection and Parameter Estimation in the Identification of Nonlinear Reduced Order State Space Models

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IFAC Proceedings Volumes 1998年第11期31卷 335-340页

作者： William Docter Christos Georgakis Chemical Process Modeling and Control Research Center and Department of Chemical Engineering Lehigh University Bethlehem Pennsylvania USA

This paper presents a general methodology for the development of Nonlinear Low Order Models (NLLOM) from data collected from detailed nonlinear simulation models. This methodology is divided into two tasks: development of a Average Linear Low Order Model (ALLOM) and augmentation of the ALLOM to form a NLLOM, the latter task being the focus of this paper. The tools examined for the nonlinear augmentation of the ALLOM include stepwise regression and nonlinear optimization. Results will be presented for the application of these techniques towards the development of an NLLOM from a detailed high purity distillation simulation.

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A New Measure of process Output controllability

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IFAC Proceedings Volumes 1998年第11期31卷 663-672页

作者： David R. Vinson Christos Georgakis Chemical Process Modeling and Control Research Center and Department of Chemical Engineering Lehigh University Bethlehem PA 18015

A steady state, multivariable, and nonlinear measure is presented for assessing the input-output, open-loop controllability of a process. This measure is ascertaining the inherent controllability of the process, as it is calculated in the absence of any regulatory control structure. It is also independent of the inventory control structure that might be assumed present in order to keep the inventory levels constant. This measure evaluates the ability of a design to reach all points of the desired output space and to reject the expected disturbances utilizing input action not exceeding the available input space. Besides being applicable to a SISO case, its multivariable character is shown to be more accurate than existing measures such as RGA, minimum singular value, and condition number.

关键词： control theory controllability Distillation columns Inputs Nonlinear gain Output Polygons

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State Estimation of Baker's Yeast Fed-Batch Cultivation by Extended Kalman Filter Using Alternative Models 1

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IFAC Proceedings Volumes 1998年第11期31卷 601-606页

作者： P. Hrnčiřík J. Náhlík V. Havlena Dept. of Computing and Control Engineering Institute of Chemical Technology Prague Czech Republic Trnka Laboratory for Automatic Control Czech Technical University Prague and Honeywell Technology Center Prague Czech Republic

The implementation of a new estimation method with alternative process models for the state estimation of the baker’s yeast fermentation is presented. Some of the implementation issues are discussed using the data ob... 详细信息

关键词： Estimation Extended Kalman Filter Fermentation processes Nonlinear model

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