Journal of Professor & SPaC member

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Last Updated : 03/2016
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  • Scheduled-step-size affine projection algorithm

    Chang Hee Lee, PooGyeon Park

    Circuits and Systems I: Regular Papers, IEEE Transactions on

    Abstract An approach for scheduling the step sizes of an adaptive filter using the affine projection algorithm (APA) is proposed so that its mean-square deviation (MSD) learning curve can be guided along a pre-designed trajectory. This approach eliminates the parameter-tuning process and does not require estimating unmeasurable stochastic quantities. Furthermore, a step-size lower bound is derived in random-walk-modeled environments that leads the adaptive filter to achieve the smallest steady-state MSD, while in stationary environments, the closer to zero the step size is, the smaller the steady-state MSD. For efficient memory usage in practice, the schedule is modified from full-table step sizes to a few down-sampled step sizes without performance degradation. In a simulation, the scheduled-step-size APA exhibits fast convergence and produces small steady-state error not only for a white signal but also for various colored input signals for a properly chosen projection order. The proposed algorithm also demonstrates greater robustness over different signal-to-noise ratios than the existing variable-step-size APAs.
  • Improved affine projection sign algorithm for sparse system identification

    JinWoo Yoo, JaeWook Shin, Hyun-Tack Choi, PooGyeon Park

    Electronics letters

    Abstract Proposed is a novel affine projection sign algorithm with L0-norm cost to improve the convergence rate in a sparse system. The proposed algorithm is robust to impulsive noise due to L1-norm minimisation. It also ensures improved performance in terms of convergence rate owing to the L0-norm cost. The simulation results demonstrate that the proposed algorithm improves the filter performance of sparse system identification.
  • Optimal step-size affine projection algorithm

    Chang Hee Lee, PooGyeon Park

    Signal Processing Letters, IEEE

    Abstract This letter describes how to set up the step size of the affine projection algorithm (APA) based on mean-square deviation analysis. The analysis considers the cross-correlation between the current weight error vector and the prior measurement noises associated with the reused inputs vectors for better prediction of the learning behavior of the APA. With the predetermined step size based on the analysis, the proposed approach eliminates the parameter-tuning process and the derived algorithm achieves both the fast convergence rate and the low steady-state error. Simulation results show that the proposed algorithm performs better than previous algorithms.
  • Improved approach to robust stability and {\ mathcal {H}} _\ infty performance analysis for systems with an interval time-varying delay

    Changki Jeong, PooGyeon Park, Sung Hyun Kim

    Applied Mathematics and Computation

    Abstract An improved delay-and range-dependent robust stability and { mathcal {H}} _ infty performance analysis criterion for systems with an interval time-varying delay is investigated. A novel Lyapunov-Krasovskii functional containing triple-integral terms is established, and an extended free-weighting matrix method, double-integral inequality method is subsequently proposed. Numerical examples validate the effectiveness of the proposed double-integral inequality method and show that our approach is less conservative than existing methods.
  • Stabilization for Takagi-Sugeno fuzzy systems based on partitioning the range of fuzzy weights

    Jeong Wan Ko, Won Il Lee, PooGyeon Park


    Abstract In this note, the state-feedback stabilization for continuous-time Takagi?Sugeno (T?S) fuzzy systems is addressed, where the fuzzy weighting functions are assumed to be differentiable and their ranges of variation are possibly bounded by some parameters. By utilizing the matrix elimination lemma and introducing a polyhedral partition to the range of the fuzzy weights, the quadratically parameterized condition is transformed to being piecewise linear in both the fuzzy weights and their derivatives. Then, a switching control based on the partition is considered, by utilizing the extreme points in each partition to address the constraints of the fuzzy weights and their derivatives. The simulation shows that finer subdivision in the partition leads to better stability and stabilization margins.
  • Affine projection algorithm with decremental projection order and optimally-designed step size

    NW Kong, Jae Won Shin, PooGyeon Park

    Electronics letters

    Abstract The proposed algorithm introduces a novel scheme for obtaining an optimal step size and proposes a criterion for decrementing the projection order, which would lead to fast convergence and a small steady-state estimation error with low computational complexity. The scheme is based on an analysis of the mean square deviation (MSD) for the tap weight and its estimated value at each iteration. The criterion is obtained by calculating the steady-state MSD. Experimental results show that the proposed algorithm has faster convergence and a smaller steady-state error than the existing affine projection algorithms with a variable step size or variable projection order.
  • Variable step-size affine projection sign algorithm

    Jeyong Shin, Jerald Yoo, Pyeongyeol Park

    Electronics letters

    Abstract Proposed is a variable step-size affine projection sign algorithm (APSA) based on the minimisation of mean-square deviation. Because the proposed algorithm calculates the optimum step size in every iteration, it ensures an improved performance in terms of convergence rate and misalignment, compared to conventional APSAs. The proposed algorithm is tested in a system identification scenario that includes impulsive noise.
  • Normalised subband adaptive filter with variable step size

    JaeWook Shin, NamWoong Kong, PooGyeon Park

    Electronics letters

    Abstract Proposed is a normalised subband adaptive filter algorithm with a variable step size based on the mean-square deviation (MSD) analysis. Since the spectrum of each input signal in subbands is close to that of white noise, the MSD can be approximated. The step size in this study is chosen such that the MSD undergoes the largest decrease from one iteration to the next, which leads to a fast convergence rate and a small misalignment. Simulation results confirm that the proposed algorithm outperforms existing algorithms in the literature.
  • Reciprocally Convex Approach for the Stability of Networked Control Systems

    Jeong Wan Ko, PooGyeon Park

    Intelligent Control and Innovative Computing

    Abstract This chapter deals with the problem of stability analysis for networked control systems via the time-delayed system approach. The network-induced delays are modeled as two additive time-varying delays in the closed-loop system. To check the stability of such particular featured systems, an appropriate Lyapunov?Krasovskii functional is proposed and the Jensen inequality lemma is applied to the integral terms that are derived from the derivative of the Lyapunov?Krasovskii functional. Here, the cascaded structure of the delays in the system enables one to partition the domain of the integral terms into three parts, which produces a linear combination of positive functions weighted by inverses of convex parameters. This is handled efficiently by the authors’ lower bounds lemma that handles the so-called reciprocally convex combination.
  • Acoustic source localization based on the extended Kalman filter for an underwater vehicle with a pair of hydrophones

    B Kang, Jeawook Shin, Ju-man Song, H Choi, P Park

    World Academy of Science, Engineering and Technology

    Abstract In this study, we consider a special situation that only a pair of hydrophone on a moving underwater vehicle is available to localize a fixed acoustic source of far distance. The trigonometry can be used in this situation by using two different DOA of different locations. Notice that the distance between the two locations should be measured. Therefore, we assume that the vehicle is sailing straightly and the moving distance for each unit time is measured continuously. However, the accuracy of the localization using the trigonometry is highly dependent to the accuracy of DOAs and measured moving distances. Therefore, we proposed another method based on the extended Kalman filter that gives more robust and accurate localization result.