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Internal Stability (internal + stability)

Distribution by Scientific Domains
Engineering66%

Selected Abstracts

Robust tracking control for a class of MIMO nonlinear systems with measurable output feedback

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2008
Ya-Jun Pan
Abstract This paper proposes a robust output feedback controller for a class of nonlinear systems to track a desired trajectory. Our main goal is to ensure the global input-to-state stability (ISS) property of the tracking error nonlinear dynamics with respect to the unknown structural system uncertainties and external disturbances. Our approach consists of constructing a nonlinear observer to reconstruct the unavailable states, and then designing a discontinuous controller using a back-stepping like design procedure to ensure the ISS property. The observer design is realized through state transformation and there is only one parameter to be determined. Through solving a Hamilton,Jacoby inequality, the nonlinear control law for the first subsystem specifies a nonlinear switching surface. By virtue of nonlinear control for the first subsystem, the resulting sliding manifold in the sliding phase possesses the desired ISS property and to certain extent the optimality. Associated with the new switching surface, the sliding mode control is applied to the second subsystem to accomplish the tracking task. As a result, the tracking error is bounded and the ISS property of the whole system can be ensured while the internal stability is also achieved. Finally, an example is presented to show the effectiveness of the proposed scheme. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Disturbance attenuation of a class of non-linear systems via output feedback

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 15 2003
Wei Lin
Abstract This paper studies the problem of disturbance attenuation with internal stability via output feedback for a family of non-linear systems. Using a feedback domination design which substantially differs from the separation principle, we explicitly construct a dynamic output compensator attenuating the disturbance's effect on the output to an arbitrary degree of accuracy in the L2 -gain sense, and achieving global asymptotic stability in the absence of disturbance. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Composition cascade control for chemical reactors

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 13 2002
Jose Alvarez-Ramirez
Abstract Eventhough the composition control of chemical reactors is an old, widely studied, and still relevant problem in chemical process control, it still presents some aspects that remain unexplored or unresolved. For instance, a unifying approach is needed to systematize the existing ad hoc controller constructions, to rigorously explain their remarkable robustness property, and to explore the possibility of improving their construction and functioning. In this paper, some aspects of these control problems are addressed by resorting to recently developed approaches in constructive non-linear control, yielding a systematic controller construction coupled to a simple tuning scheme that can be executed with standard tuning rules, a closed-loop stability criterion, and an explanation of the closed-loop dynamics behaviour. Specifically, a linear cascade (master/slave) control configuration is proposed, which leads to global internal stability of the controlled system with asymptotic regulation of the output-stream composition about a given desired setpoint. A simulation example is used to illustrate the results. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Evaluation of the intramolecular basis set superposition error in the calculations of larger molecules: [n]helicenes and Phe-Gly-Phe tripeptide

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2008
Haydée Valdés
Abstract Correlated ab initio calculations on large systems, such as the popular MP2 (or RI-MP2) method, suffer from the intramolecular basis set superposition error (BSSE). This error is typically manifested in molecules with folded structures, characterized by intramolecular dispersion interactions. It can dramatically affect the energy differences between various conformers as well as intramolecular stabilities, and it can even impair the accuracy of the predictions of the equilibrium molecular structures. In this study, we will present two extreme cases of intramolecular BSSE, the internal stability of [n]helicene molecules and the relative energies of various conformers of phenylalanyl-glycyl-phenylalanine tripeptide (Phe-Gly-Phe), and compare the calculated data with benchmark values (experimental or high-level theoretical data). As a practical and cheap solution to the accurate treatment of the systems with large anticipated value of intramolecular BSSE, the recently developed density functional method augmented with an empirical dispersion term (DFT-D) is proposed and shown to provide very good results in both of the above described representative cases. © 2007 Wiley Periodicals, Inc. J Comput Chem 2008 [source]

Positioning and the specific sequence of each 13-mer motif are critical for activity of the plasmid RK2 replication origin

MOLECULAR MICROBIOLOGY, Issue 5 2005
Lukasz Kowalczyk
Summary The minimal replication origin of the broad-host-range plasmid RK2, oriV, contains five iterons which are binding sites for the plasmid-encoded replication initiation protein TrfA, four DnaA boxes, which bind the host DnaA protein, and an AT-rich region containing four 13-mer sequences. In this study, 26 mutants with altered sequence and/or spacing of 13-mer motifs have been constructed and analysed for replication activity in vivo and in vitro. The data show that the replacement of oriV 13-mers by similar but not identical 13-mer sequences from Escherichia coli oriC inactivates the origin. In addition, interchanging the positions of the oriV 13-mers results in greatly reduced activity. Mutants with T/A substitutions are also inactive. Furthermore, introduction of single-nucleotide substitutions demonstrates very restricted sequence requirements depending on the 13-mer position. Only two of the mutants are host specific, functional in Pseudomonas aeruginosa but not in E. coli. Our experiments demonstrate considerable complexity in the plasmid AT-rich region architecture required for functionality. It is evident that low internal stability of this region is not the only feature contributing to origin activity. Our studies suggest a requirement for sequence-specific protein interactions within the 13-mers during assembly of replication complexes at the plasmid origin. [source]

Internal stabilization of standard sampled-data systems

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
B. P. Lampe Prof. Dr.
The paper presents necessary and sufficient conditions under which for a standard sampled-data system there exists a digital controller, that ensures the internal stability of the system. For the case of stabilizability a general expression for the set of all stabilizing controllers is given. The stabilizability conditions are formulated as divisibility of certain polynomials, controllability and observability concepts are not used. [source]