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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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controllability Issues Concerning Particle Size in Emulsion Polymerization

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IFAC Proceedings Volumes 1995年第9期28卷 299-304页

作者： Vincenzo Liotta Christos Georgakis Mohamed El-Aasser Lehigh University Process Modeling and Control Research Center Bethlehem Pennsylvania 18015 USA Lehigh University Emulsion Polymers Institiute Bethlehem Pennsylvania 18015 USA

The utility of the growth mechanism to influence polystyrene particle size distributions is investigated via a competitive growth framework. A dynamic competitive growth model, extrapolated from an experimentally validated unimodal model, is used to simulate the semi-batch growth of two monodisperse particle populations at 50°C. Results show that the greatest relative narrowing between the two populations occurs at the particle monomer concentration ([ M ] p ) saturation limit and decreases as [ M ] p is decreased towards a limited reaction lower bound. Simulations run at these limits provide the reachable regions starting from several initial diameter population pairs. The areas of these regions are found to be dependent on the magnitude of the initial diameter ratio and the individual particle sizes.

关键词： controllability reachability process control nonlinear systems

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Bilinear Identification of Nonlinear processes

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IFAC Proceedings Volumes 1994年第2期27卷 47-52页

作者： James F. Bartee Christos Georgakis Chemical Process Modeling and Control Research Center Department of Chemical Engineering Lehigh University Bethlehem Pennsylvania USA 18015 Fax: (610)758-5432 Internet

Identification of nonlinear processes using bilinear models is presented. To avoid direct estimation of the bilinear model parameters, a dynamically equivalent input/output model structure is developed through an analysis of the observability of the bilinear system. Calculation of the Volterra kernels from the input/output model parameters is presented and the overparameterization of the input/output model form is examined by comparison with the Volterra series model form. Constraint equations calculated from this guarantees the dynamic equivalence of the input/output and state-space forms. The input/output model parameters are estimated through an extended least-squares method. An example of a fluid catalytic cracking unit (FCCU) is presented.

关键词： Nonlinear Identification Bilinear Models Input/Output Models Volterra Kernels FCCU

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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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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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INFERENTIAL MODEL-BASED control OF MULTICOMPONENT BATCH DISTILLATION

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chemical ENGINEERING SCIENCE 1992年第4期47卷 887-898页

作者： QUINTEROMARMOL, E LUYBEN, WL Process Modeling and Control Center Department of Chemical Engineering Mountaintop Campus 111 Research Drive Lehigh University Bethlehem PA 18015 U.S.A.

Industrial interest in batch distillation has increased significantly in recent years as more batch processing is being used for low-volume high-value specialty chemicals. Most studies have concentrated on the determination of optimum operating strategies: optimum trajectories of reflux ratio and pressure during the batch and processing of the slop cuts that are produced. Little attention has been paid to the problems of control. If instantaneous and perfect analyzers were available, the control of batch distillation would be straightforward once the optimum policies are available. Switching from total-reflux operation to producing product and from this to slop-cut production could be performed when compositions in the reflux drum or in product tankage reached the desired values. However, in most industrial applications of batch distillation, perfect composition measurements are not available. This means that an inferential control system that relies on temperature and flow measurements must be used. Models of the batch distillation process can be used to provide estimates of the required compositions. This paper presents the results of a study of two types of model-based inferential control systems for multicomponent batch distillation. The results showed that both steady-state and dynamic estimators provide good estimation of the distillate compositions using only one temperature measurement.

关键词： Distillation columns

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Identification and control of Bilinear Systems

Identification and Control of Bilinear Systems

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American control Conference (ACC)

作者： James F. Bartee Christos Georgakis Chemical Process Modeling and Control Research Center and Department of Chemical-Engineering Lehigh University Bethlehem Pennsylvania Chemical Process Modeling and Control Research Center and Department of Chemical-Engineering Lehigh University Bethlehem PA USA

The research presented in this paper combines the problem of identifiction and control of nonlinear processes. This is done by approximating the process with a bilinear model and designing model-based control structures (Reference System controllers) based on the bilinear approximation. The identification of the bilinear model and the construction of the controller are described below. An example of the identification and control of an exothermic CSTR is also presented.

关键词： control systems Nonlinear systems control system synthesis Nonlinear control systems Linear systems process control chemical processes Continuous-stirred tank reactor control theory Algorithm design and analysis

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Issues in the Optimization, Estimation and control of Fed-batch Bioreactors Using Tendency Models

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IFAC Proceedings Volumes 1992年第2期25卷 71-76页

作者： P. Tsobanakis S.H. Lee J.A. Phillips C. Georgakis Bioprocessing Institute Chemical Process Modeling and Control Research Center and Department of Chemical Engineering Lehigh University Bethlehem PA 18015 USA

The tendency modeling approach for optimization, estimation, and control is applied to bioreactors. This approach uses a “tendency” or “grey” model based on the available fundamental knowledge of the process and emphasizes the incorporation of new process data. The technique is demonstrated on simulation studies and preliminary experimental results of the penicillin fermentation. The tendency model is based on reactor mass balances such as those proposed by Bajpai and Reuß (1980) while the number of overall reactions and their stoichiometry are derived by abstract factor analysis of experimental data. Actual process and equipment constraints, such as the power mounted to the fermentor, the oxygen transfer capacity, and the rheological characteristics of the broth, are added. The model can be updated periodically utilizing data collected both on-line and off-line. The updated model can be used off-line to develop optimal feeding policies. On-line, a Kalman filter can utilize the tendency model to estimate poorly, infrequently, or unmeasured states.

关键词： modeling tendency modeling factor analysis optimization estimation fermentation processes

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State estimation and control of spray etching processes

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Journal of process control 1992年第2期2卷 87-101页

作者： Kao, Alan S. Stenger, Harvey G. Georgakis, Christos Covert, Kathleen L. Chemical Process Modeling and Control Center Lehigh University Bethlehem PA 18015 Iacocca Hall United States The IBM Corporation Endicott NY 13760 1701 North Street United States

Several Kalman filter designs were developed and tested for controlling a spray etching process. A hybrid extended Kalman filter was found to yield biased estimates in the presence of process-model mismatch. This issue was resolved by augmenting the state vector with poorly known parameters and developing a proportional-integral Kalman filter. These parameters are treated as stochastic processes, through which the estimate bias of the extended Kalman filter is eliminated. The resulting filter designs are capable of providing accurate estimates of the etching species concentrations as well as making available frequent estimates of the etch profile characteristics, which are only measured at infrequent intervals. © 1992.

关键词： Kalman filters spray etching state estimation

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On-line Estimation of Reaction Rates in Batch Reactors

On-line Estimation of Reaction Rates in Batch Reactors

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American control Conference (ACC)

作者： Guillermo Elicabe Christos Georgakis Chemical Process Modeling and Control Research Center Department of Chemical Engineering Lehigh University Bethlehem PA USA

Very often one needs to know the current values of reaction rates in chemical reactors in order to control them effectively or in order to avoid unsafe operating conditions. ln this work state estimation techniques are used to estimate on-line reaction rates in well mixed isothermal batch reactors. The proposed scheme assumes the availability of on-line measurements of overall concentrations of the reactants, and the lack of knowledge on the reaction rate dependence with those concentrations. The state estimator used in this application is a Kalman filter based estimator. Relationships between the continuous and the discrete versions of the filter as well as a Laplace domain analysis were considered. The estimation scheme is applied to two examples of semi-continuous emulsion co-polymerization.

关键词： Inductors Equations chemical reactors Tellurium State estimation Content addressable storage Isothermal processes Kalman filters Phase estimation Steady-state

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