Abstract/Details

Robust control of large-scale nonlinear constrained systems


2002 2002

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Abstract (summary)

Current applications of nonlinear model predictive control algorithms are restricted to small-scale processes, due mainly to the computational difficulties encountered when trying to solve the non-convex nonlinear optimization problem on-line. Also, there is no complete procedure in synthesizing a nonlinear model predictive controller that guarantees stability when there is model uncertainty and when the state is not completely measured. Although there are plenty of results available for the nominal closed-loop stability of various NMPC algorithms, few results are available on the robust stability of constrained nonlinear systems. We have proposed a cascade NMPC algorithm for large-scale systems. This control algorithm consists of two levels where the low-level controller guarantees robust stability while the high-level controller optimizes nominal performance subject to robust stability constraint. The low-level controller is an output feedback controller while the high-level controller is a state feedback controller. There are several characteristics to be noticed about this algorithm: it is computationally efficient and is always feasible to be implemented on-line; it uses a closed-loop control strategy; it guarantees robust asymptotic stability with various kinds of model uncertainties, if such a controller exists.

For model uncertainty description, we consider both parametric and structural uncertainty. We develop an uncertainty description that can handle both parametric and structural uncertainties in a uniform manner. We have applied the proposed algorithm to an industrial system consisting of a co-polymerization reactor with recycle. It is a reasonably complex, highly nonlinear and poorly modeled (i.e., uncertain) process. Simulation results show the feasibility of implementing this algorithm on realistic industrial systems where model uncertainties always exist.

Indexing (details)


Subject
Chemical engineering
Classification
0542: Chemical engineering
Identifier / keyword
Applied sciences; Constrained systems; Nonlinear model predictive control; Nonlinear-constrained; Robust control
Title
Robust control of large-scale nonlinear constrained systems
Author
Zhang, Weihua
Number of pages
102
Publication year
2002
Degree date
2002
School code
0118
Source
DAI-B 63/10, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780493882161, 0493882162
Advisor
Zheng, Alex Z. Q.
University/institution
University of Massachusetts Amherst
University location
United States -- Massachusetts
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3068605
ProQuest document ID
305586700
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305586700
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