Journal of Professor & SPaC member

If you click the title of the journal, you can get more information about the journal.
Last Updated : 03/2016
all           2017           2016           2015           2014           2013           2012           ~2011          
  • H∞ control for singular Markovian jump systems with incomplete knowledge of transition probabilities

    Nam Kyu Kwon, In Seok Park, PooGyeon Park

    Applied Mathematics and Computation

    AbstractThis paper proposes a H∞ state-feedback control for singular Markovian jump systems with incomplete knowledge of transition probabilities. Different from the previous results where the transition rates are completely known or the bounds of the unknown transition rates are given, a more general situation where the transition rates are partly unknown and the bounds of the unknown transition rates are also unknown is considered. Moreover, in contrast to the singular Markovian jump systems studied recently, the proposed method does not require any tuning parameters that arise when handling non-convex terms related to the mode-dependent Lyapunov matrices and the corresponding self-mode transition rates. Also, this paper uses all possible slack variables related to the transition rates into the relaxation process which contributes to reduce the conservatism. Finally, two numerical examples are provided to demonstrate the performance of H∞ mode-dependent control.
  • A combined reciprocal convexity approach for stability analysis of static neural networks with interval time-varying delays

    Won Il Lee, Seok Young Lee, PooGyeon Park

    Neurocomputing

    AbstractThis paper proposes a novel approach called a combined reciprocal convexity approach for the stability analysis of static neural networks with interval time-varying delays. The proposed approach deals with all convex-parameter-dependent terms in the time derivative of the Lyapunov-Krasovskii functional non-conservatively by extending the idea of the conventional reciprocal convexity approach. Based on the proposed technique and a new Lyapunov-Krasovskii functional, two improved delay-dependent stability criteria are derived in terms of linear matrix inequalities(LMIs). Some numerical examples are given to demonstrate the proposed results.

  • Polynomials‐based summation inequalities and their applications to discrete‐time systems with time‐varying delays

    Seok Young Lee, Won Il Lee, PooGyeon Park

    International Journal of Robust and Nonlinear Control

    AbstractThis paper proposes a novel summation inequality, say a polynomials-based summation inequality, which contains well-known summation inequalities as special cases. By specially choosing slack matrices, polynomial functions, and an arbitrary vector, it reduces to Moon’s inequality, a discrete-time counterpart of Wirtinger-based integral inequality, auxiliary function-based summation inequalities employing the same-order orthogonal polynomial functions. Thus, the proposed summation inequality is more general than other summation inequalities. Additionally, this paper derives the polynomials-based summation inequality employing first-order and second-order orthogonal polynomial functions, which contributes to obtaining improved stability criteria for discrete-time systems with time-varying delays.

  • Improved stability criteria for linear systems with interval time-varying delays: Generalized zero equalities approach

    Seok Young Lee, Won Il Lee, PooGyeon Park

    Applied Mathematics and Computation

    AbstractThis paper suggests first-order and second-order generalized zero equalities and constructs a new flexible Lyapunov–Krasovskii functional with more state terms. Also, by applying various zero equalities, improved stability criteria of linear systems with interval time-varying delays are developed. Using Wirtinger-based integral inequality, Jensen inequality and a lower bound lemma, the time derivative of the Lyapunov–Krasovskii functional is bounded by the combinations of various state terms including not only integral terms but also their interval-normalized versions, which contributes to make the stability criteria less conservative. Numerical examples show the improved performance of the criteria in terms of maximum delay bounds.

  • Polynomials-based integral inequality for stability analysis of linear systems with time-varying delays

    Seok Young Lee, Won Il Lee, PooGyeon Park

    Journal of the Franklin Institute

    Abstracthttps://scholar.google.co.kr/citations?view_op=view_citation&hl=ko&user=ktTQiqsAAAAJ&sortby=pubdate&citation_for_view=ktTQiqsAAAAJ:HtS1dXgVpQUC

  • New stability analysis for discrete time-delay systems via auxiliary-function-based summation inequalities

    PooGyeon Park, Seok Young Lee, Won Il Lee

    Journal of the Franklin Institute

    AbstractFor the stability analysis of discrete time-delay systems, Jensen inequality has been widely used as the method supporting inequalities for summation quadratic functions. It not only requires a smaller number of decision variables than other approaches but also achieves identical or comparable performance behavior. Based on the analysis for the conservatism of Jensen inequality, however, this paper suggests a new summation inequality say an auxiliary-function-based summation inequality. It is verified that the proposed inequality is a generalized form of the novel summation inequality reported recently. Also, an application to stability analysis for discrete time-delay systems is provided.

  • Improved H∞ state-feedback control for continuous-time Markovian jump fuzzy systems with incomplete knowledge of transition probabilities

    Nam Kyu Kwon, Bum Yong Park, PooGyeon Park, In Seok Park

    Journal of the Franklin Institute

    AbstractThis paper proposes the improved H∞ state-feedback control for Markovian jump fuzzy systems (MJFSs) with incomplete knowledge of transition probabilities. From the fundamental first-order properties of the transition rates, two second-order properties are introduced without information on the lower and upper bounds of the transition rates, differently from other approaches in the literature. Based on these properties, this paper uses all possible slack variables into the relaxation process which contributes to reduce the conservatism. Finally, two numerical examples are provided to illustrate the effectiveness of the proposed method.

  • A Variable Step-Size Normalized Subband Adaptive Filter with a Step-Size Scaler against Impulsive Measurement Noise

    Junwoong Hur, Insun Song, PooGyeon Park

    IEEE Transactions on Circuits and Systems II: Express Briefs

    AbstractThis letter introduces a variable step-size (VSS) normalized subband adaptive filter (NSAF) using a step-size scaler to improve the robustness against impulsive measurement noise. When impulsive measurement noise appears, the step size of the proposed VSS NSAF is scaled down by the step-size scaler, which is suitable for application in the NSAF. This removes a possibility of updating weight estimates based on defective information of the subband output errors due to impulsive measurement noise. In the proposed VSS NSAF, the equations for updating the step size are constructed by interpreting the behavior of the mean square deviation (MSD) of the conventional NSAF and applying the step-size scaler. The step-size scaler utilizes the sum of the subband output errors, which can be influenced by impulsive measurement noise. Simulations using the proposed VSS NSAF show an excellent transient and steady-state behavior with colored input in impulsive-noise environments.

  • A combined first-and second-order reciprocal convexity approach for stability analysis of systems with interval time-varying delays

    Won Il Lee, Seok Young Lee, PooGyeon Park

    Journal of the Franklin Institute

    AbstractFor the interval time-varying delay systems, Jensen inequality lemma yields some terms with the inverse of convex and squared convex parameters, which often makes it difficult to find their bounds. Recently, reciprocal and second-order reciprocal convexity approaches have been proposed to handle the difficulties with a set of convex parameters and a set of squared convex parameters, respectively, but these approaches do not investigate the relation between the two sets. This paper offers much tighter bounds of those terms utilizing the relations among the two sets with the lower bound lemma. Based on the new approach and Lyapunov theory, less conservative stability criteria for time delay systems are developed. To show the effectiveness of the new approach, two numerical examples are given.

  • Auxiliary function-based integral/summation inequalities: Application to continuous/discrete time-delay systems

    PooGyeon Park, Won Il Lee, Seok Young Lee

    International Journal of Control, Automation and Systems

    AbstractIn the field of stability analysis for time-delay systems, finding precise bounds of integral/summation forms of quadratic functions plays a key role in reducing the conservatism. Consequently, there have been many attempts to develop inequalities yielding much tighter bounds. This paper develops novel inequalities using intermediate terms called auxiliary functions, which includes the existing inequalities as special cases. The stability conditions for continuous/discrete time-delay systems are derived in terms of linear matrix inequalities (LMIs) by using the proposed inequalities with simple numerical examples.