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Steady State Optimal Test Signal Design for Constrained Multivariable Systems

IFAC Proceedings Volumes 2000年第15期33卷 1213-1218页

作者： Qiang Zhan Christos Georgakis Chemical Process Modeling and Control Center and Dept. of Chemical Engineering Lehigh University Bethlehem PA 18015

A new input signal design method is proposed for constrained multivariable systems that aims to maximize the signal to noise ratio while also meeting certain input and output constraints. The proposed methodology utilizes an approximate steady state model that is assumed to be known a-priori. The steady state operability concepts are used to incorporate the steady state input and output constraints into the signal design. The input test signal design problem is formulated as a nonlinear optimization problem and it is shown that all the existing methods can be unified under this proposed design framework. It will be proven that the design method is D-optimal from a steady state perspective. For ill-conditioned systems, more energy will be automatically directed in the weak directions. An example will be given to demonstrate the superiority of the method.

关键词： Identification Input Signal Design Multivariable control

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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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Static anti-windup controller synthesis using simultaneous convex design

Static anti-windup controller synthesis using simultaneous c...

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05AIChE: 2005 AIChE Annual Meeting and Fall Showcase

作者： Tiwari, Pradeep Y. Mulder, Eric F. Kotharel, Mayuresh V. Chemical Process Modeling and Control Center Department of Chemical Engineering Lehigh University Bethlehem PA 18015 United States ExxonMobil Chemical 5000 Bayway Drive Baytown TX 77520

We present a method for the synthesis of a control law which incorporates both a traditional linear output-feedback controller as well as a static anti-windup compensator. Unlike traditional anti-windup controller design in which the linear controller and anti-windup compensator are designed sequentially, our method synthesizes all controller parameters simultaneously, thus providing a priori account of the effects of saturation on the closed-loop dynamics. Moreover, we derive sufficient conditions for the quadratic stability and (possibly) multiple performance bounds on the closed-loop dynamics such that the entire synthesis is cast as an optimization problem over linear matrix inequalitics (LMIs).

关键词： Feedback control

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Approximating switched continuous systems by rectangular automata

Approximating switched continuous systems by rectangular aut...

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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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Extended slug control for pipeline-riser systems

Extended slug control for pipeline-riser systems

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12th International Conference on Multiphase Production Technology '05

作者： Storkaas, Espen Godhavn, John-Morten Dept. of Chemical Engineering Norwegian University of Science and Engineering Norway Process Control Statoil R and D Norway

ISBN: (纸本)1855980649

control systems that prevent the development of riser slugging in pipeline-riser systems have in recent years been introduced on several offshore processing facilities. These control systems are based on active use of the topside choke valve to keep a pressure measured somewhere upstream of the riser constant. These control systems have been a great success, and are emerging as the standard method to avoid riser slugging in multiphase production pipelines. The active use of the topside choke valve for control purposes opens the door for several other interesting applications as there are other multiphase phenomena occurring in a pipeline-riser system that can cause operational problems for the downstream production facilities. Among these are surge waves. When the production rate in a gas-condensate pipeline is increased, the liquid holdup in the pipeline will go down. This means that during the transition period, an excess amount of liquid needs to be transported out of the pipeline before a new steady state can be reached. The excess liquid can cause the liquid rate out of the pipeline to exceed the liquid handling capacity of the receiving facilities. Start-up slugs occur when the pipeline is started up from shut-in conditions. These slugs are similar to surge waves as they are caused by an increase in the production rate. However, start-up slugs can be even more violent as they potentially can initiate riser slugs and thereby cause even larger peaks in the liquid production. In this paper we introduce a novel control structure that extends the scope of pipeline control by including suppression of surge waves and start-up slugs. The control system consists of a slug controller and individual flow controllers for each phase combined seamlessly through a minimum select function. The performance of the control system is illustrated with simulations from an industrial case study. © BHR Group 2005 Multiphase Production Technology 12.

关键词： Pipelines

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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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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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Reference system based model predictive control

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IFAC Proceedings Volumes 1996年第1期29卷 5923-5928页

作者： Lokesh Kalra Chriatos Georgakis Chemical Process Modeling and Control Research Center and Department of Chemical Engineering Lehigh University Bethlehem Pennsylvania USA

Despite recent advances in the field, the tuning of presently popular Model Predictive control formulations is largely a trial and error procedure. Motivated by this fact, a Reference System based tuning is explored through Reference System Model Predictive control. The RS-MPC algorithm is examined because of its potentially more intuitive approach to tuning. Under this methodology the tuning involves the selection of two parameters for each controlled variable. The first parameter adjusts the shape of the response and the second one affects the speed. Using these, instead of the weight-based tuning of conventional MPC, much of the trial and error is eliminated. The most important features of the controller arc elucidated through the performance of the STSO and MIMO cases for the Amoco Fluid Catalytic Cracker process simulation.

关键词： Multivariable Feedback control Predictive control Models Tuning Characteristics control Algorithms Simulators

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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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A Framework for Design of Scheduled Output Feedback Model Predictive control

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IFAC Proceedings Volumes 2004年第1期37卷 71-76页

作者： Zhaoyang Wan Mayuresh V. Kothare Chemical Process Modeling and Control Research Center Department of Chemical Engineering Lehigh University Bethlehem PA 18015

We present a stabilizing scheduled output feedback Model Predictive control (MPC) algorithm for constrained nonlinear systems with large operating regions. We design a set of local output feedback predictive controllers with their estimated regions of stability covering the desired operating region, and implement them as a single scheduled output feedback MPC which on-line switches between the set of local controllers and achieves nonliilear transitions with guaranteed stability. This algorithm provides a general framework for scheduled output feedback MPC design.

关键词： Model predictive control constrained nonlinear systems output feedback scheduling linear matrix inequalities

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