A Feature Selection Method for Multivariate Performance Measures

Feature selection with specific multivariate performance measures is the key to the success of many applications, such as image retrieval and text classification. The existing feature selection methods are usually designed for classification error. In this paper, we propose a generalized sparse regularizer. Based on the proposed regularizer, we present a unified feature selection framework for general loss functions. In particular, we study the novel feature selection paradigm by optimizing multivariate performance measures. The resultant formulation is a challenging problem for high-dimensional data. Hence, a two-layer cutting plane algorithm is proposed to solve this problem, and the convergence is presented. In addition, we adapt the proposed method to optimize multivariate measures for multiple instance learning problems. The analyses by comparing with the state-of-the-art feature selection methods show that the proposed method is superior to others. Extensive experiments on large-scale and high-dimensional real world datasets show that the proposed method outperforms $l_1$-SVM and SVM-RFE when choosing a small subset of features, and achieves significantly improved performances over SVM$^{perf}$ in terms of $F_1$-score

Sparse Iterative Learning Control with Application to a Wafer Stage: Achieving Performance, Resource Efficiency, and Task Flexibility

Trial-varying disturbances are a key concern in Iterative Learning Control (ILC) and may lead to inefficient and expensive implementations and severe performance deterioration. The aim of this paper is to develop a general framework for optimization-based ILC that allows for enforcing additional structure, including sparsity. The proposed method enforces sparsity in a generalized setting through convex relaxations using $\ell_1$ norms. The proposed ILC framework is applied to the optimization of sampling sequences for resource efficient implementation, trial-varying disturbance attenuation, and basis function selection. The framework has a large potential in control applications such as mechatronics, as is confirmed through an application on a wafer stage.Comment: 12 pages, 14 figure

Signal and System Approximation from General Measurements

In this paper we analyze the behavior of system approximation processes for stable linear time-invariant (LTI) systems and signals in the Paley-Wiener space PW_\pi^1. We consider approximation processes, where the input signal is not directly used to generate the system output, but instead a sequence of numbers is used that is generated from the input signal by measurement functionals. We consider classical sampling which corresponds to a pointwise evaluation of the signal, as well as several more general measurement functionals. We show that a stable system approximation is not possible for pointwise sampling, because there exist signals and systems such that the approximation process diverges. This remains true even with oversampling. However, if more general measurement functionals are considered, a stable approximation is possible if oversampling is used. Further, we show that without oversampling we have divergence for a large class of practically relevant measurement procedures.Comment: This paper will be published as part of the book "New Perspectives on Approximation and Sampling Theory - Festschrift in honor of Paul Butzer's 85th birthday" in the Applied and Numerical Harmonic Analysis Series, Birkhauser (Springer-Verlag). Parts of this work have been presented at the IEEE International Conference on Acoustics, Speech, and Signal Processing 2014 (ICASSP 2014

Modeling and Analysis of SOGI-PLL/FLL-based Synchronization Units: Stability Impacts of Different Frequency-feedback Paths

— Second-order Generalized Integrator (SOGI)-based quadrature-signal-generator (QSG) together with either a phaselocked-loop (PLL) or a frequency-locked-loop (FLL) constitute two types of typical synchronization units (i.e., SOGI-PLL and - FLL) that have been widely used in grid-tied converter systems. This paper will reveal and clarify the stability issue of these two synchronization units arising from different implementations of the frequency-feedback-path (FFP) connecting the SOGI-QSG and the PLL/FLL. In this regard, four types of FFP implementations that are frequently seen in the literature will be discussed. Although different implementations of the FFP will not affect the steady-state frequency adaptation, their dynamical effects on the small-signal stability of SOGI-PLL/FLL remain concealed. To this end, this paper will present a comprehensive stability assessment and comparative analysis of SOGI-PLL/FLL focusing on the FFP issue. To extend the applicability and accuracy of discussions, all the analyses will be fulfilled by using a parameter space-oriented stability assessment method formulated in the linear-time periodic (LTP) framework. The obtained results are verified by time-domain simulations, and the main findings are further interpreted by using appropriate analytical models. Index Terms— FLL, PLL, synchronization, SOGI, stability, LTP, frequency feedback.acceptedVersio

Controller Stability and Low-frequency Interaction Analysis of Railway Train-Network Systems

In electrified railways, low-frequency oscillations (LFO) are commonly observed as a result of the widespread implementation of electric trains incorporating power electronic converters. While the impedance method has been employed in current stability studies for train-network systems, there is a requirement to extend stability modeling and analysis studies for the train-network system considering multiple trains having different control strategies. Hence, this paper establishes a unified impedance model in the dq-frame for the aforementioned system. Subsequently, an improved stability criterion, namly the dominant eigenvalue frequency response criterion (DEFRC), is proposed to assess system stability and unveil the mechanism of LFO. Furthermore, the interaction between different trains is clarified by analysis and case studies. Finally, the theoretical analysis is verified for accuracy based on time domain simulations

A new algorithm for dual-rate systems frequency response computation in discrete control systems

This paper addresses an easy computation of the multiple components of the response to a sinusoidal input of a dual-rate linear time-invariant discrete system from the Bode diagram of LTI systems arising from a lifted representation. Based on those results, a generalized Bode diagram is suggested. Some new conclusions derived from this conceptual interpretation are introduced. This diagram provides a better insight in the frequency-response issues in multivariable control than the standard singular value decomposition of the lifted model. As an application, the output ripple suppression in a multirate control scheme is presented.The work of J. Salt was supported in part by the Spanish Ministerio de Economia y Competitividad under Grant TEC2012-31506, and that of A. Sala by grant DPI2011-27845-C02-01 by the same institution.Salt Llobregat, JJ.; Sala Piqueras, A. (2014). A new algorithm for dual-rate systems frequency response computation in discrete control systems. Applied Mathematical Modelling. 38(23):5692-5704. https://doi.org/10.1016/j.apm.2014.04.054S56925704382

Advancements of MultiRate Signal processing for Wireless Communication Networks: Current State Of the Art

With the hasty growth of internet contact and voice and information centric communications, many contact technologies have been urbanized to meet the stringent insist of high speed information transmission and viaduct the wide bandwidth gap among ever-increasing high-data-rate core system and bandwidth-hungry end-user complex. To make efficient consumption of the limited bandwidth of obtainable access routes and cope with the difficult channel environment, several standards have been projected for a variety of broadband access scheme over different access situation (twisted pairs, coaxial cables, optical fibers, and unchanging or mobile wireless admittance). These access situations may create dissimilar channel impairments and utter unique sets of signal dispensation algorithms and techniques to combat precise impairments. In the intended and implementation sphere of those systems, many research issues arise. In this paper we present advancements of multi-rate indication processing methodologies that are aggravated by this design trend. The thesis covers the contemporary confirmation of the current literature on intrusion suppression using multi-rate indication in wireless communiquE9; networks