Unitary coherent strategy for spatial sparsity‐based DOA estimation of wideband signals

The coherent l₁‐singular value decomposition (l₁‐SVD) uses a non‐unitary coherent strategy for transferring different frequency bin data to a reference bin, which decreases the signal‐to‐error ratio (SER) in transferring, thereby leading to a decrease in accuracy in the direction of arrival (DOA) estimation. To cope with this problem, in this paper we propose a unitary coherent strategy that uses unitary focusing matrices for transferring data. Simulation results show that the proposed method outperforms the coherent l₁‐SVD method in accurate DOA estimation. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Exponential l2 − l∞ filtering for discrete‐time switched systems under a new framework

In this paper, a robust exponential l₂ ? l_∞ filtering problem is addressed for discrete‐time switched systems with polytopic uncertainties. The purpose of robust exponential l₂ ? l_∞ filtering is to design a filter such that the resulting filtering error system is robustly exponentially stable with a decay rate and a prescribed exponential l₂ ? l_∞ performance index. The robust exponential l₂ ? l_∞ filtering problem is solved via an average dwell time approach. Sufficient conditions in terms of strict LMI are derived for checking the robust exponential stability of a filter. An explicit expression for the desired robust exponential filter is also given. Finally, a numerical example is provided to demonstrate the potential and effectiveness of the proposed method. Copyright © 2011 John Wiley & Sons, Ltd.     

Fault detection filter design for discrete‐time switched linear systems with mode‐dependent average dwell‐time

This paper is concerned with the problem of the fault detection (FD) filter design for discrete‐time switched linear systems with mode‐dependent average dwell‐time. The switching law is mode‐dependent and each subsystem has its own average dwell‐time. The FD filters are designed such that the augmented switched systems are asymptotically stable, and the residual signal generated by the filters achieves a weighted l₂‐gain for some disturbances and guarantees an H _? performance for the fault. By the aid of multiple Lyapunov functions combined with projection lemma, sufficient conditions for the design of the FD filters are formulated by linear matrix inequalities, furthermore, the filters gains are characterized in terms of the solution of a convex optimization problem. Finally, an application to boost convertor is given to illustrate the effectiveness and the applicability of the proposed design method. Copyright © 2013 John Wiley & Sons, Ltd.     

Mixed norm regularized recursive total least squares for group sparse system identification

A mixed l_p,0‐regularized recursive total least squares (RTLS) algorithm is considered for group sparse system identification. Regularized recursive least squares (RLS) has been successfully applied to group sparse system identification; however, the estimation performance in regularized RLS‐based algorithms deteriorates when both input and output are contaminated by noise (the error‐in‐variables problem). We propose an l_p,0‐RTLS algorithm to handle group sparse system identification with errors‐in‐variables. The proposed algorithm is an RLS‐like solution that utilizes l_p,0‐regularization. The proposed algorithm provides excellent performance as well as reduces the required complexity by effective inversion matrix handling. Simulations demonstrate the superiority of the proposed l_p,0‐regularized RTLS for a group sparse system identification setting. Copyright © 2015 John Wiley & Sons, Ltd.     

Estimating power-frequency characteristics in power systems by means of spectral analysis techniques

This paper shows that normal power system operating data may be used to determine the power-frequency characteristics in power systems. Data are processed as random signals using spectral analysis techniques, and the results estimate the generator and load power-frequency characteristics as transfer functions. The generator characteristics K_g are determined as a transfer function of the system in which input signals are frequency fluctuation ΔF and generator power setting signal ΔP_g, and output signal is generator power output ΔP_e, To estimate the load characteristics K_l, a difficulty arises. There is a relation ΔP_/ = ΔL_o + K_lΔF between actual load ΔP_l, ideal load under the state of nominal frequency ΔL_o, and fluctuation of system frequency ΔF. Because it is impossible to measure ΔL_o directly, ΔL_o and K_lΔF cannot be separated. With regard to a partial system, when its capacity is small enough compared with the total system capacity, the contribution of ΔL_o in a partial system to ΔF of the total system may be ignored, that is, ΔF and ΔL_o are considered as independent phenomena. Thus the cross spectrum of ΔF and ΔL_o decreases to zero according to the increase of data in number, and K_l of the partial system can be estimated.     

On the improvement of l2‐performance by controller resets

In this paper, we propose a state reset algorithm that minimizes the upper bound of the l₂‐norm of an output signal at an arbitrary sampling time. By this means, we attempt to improve the l₂‐performance of a control system. It is shown that the system with the proposed reset algorithm is finite gain l₂‐stable and also asymptotically stable. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Pseudopassive two-dimensional recursive digital filters for image processing

This paper describes the theory of two-dimensional digital filters that are pseudopassive with respect to the l_p-norm of the state vector. As the classical pseudopassive digital filters are a subclass of these filters, the respective theorems referred to stability are also generalized. It is shown that this theory is useful for the two-dimensional filters that answer with non-negative-valued responses to non-negative-valued excitations. Such systems are especially suitable for image processing. the synthesis of the l₁-pseudolossless systems is proposed as a tool to guarantee stability of such filters. A technique to obtain local state-space models for such two-dimensional l₁-pseudolossless recursive filters with prescribed spatial responses is given. A ‘Gaussian filter’ design illustrates the technique and shows that the proposed two-dimensional l₁-pseudolossless filters are able to match useful spatial responses.     

Novel combination schemes of individual weighting factors sign subband adaptive filter algorithm

To improve the performance of the recently presented individual weighting factors sign subband adaptive filter (IWF‐SSAF) algorithm, its 2 combination algorithms using different step sizes are proposed. The first algorithm is to convexly combine the weight vectors of a large step‐size IWF‐SSAF filter and a small step‐size one; and the second algorithm is to obtain a time‐varying step size for the IWF‐SSAF by combining a large step size and a small one. The minimization of the sum of the l₁‐norm of subband errors is used to indirectly update the mixing parameters in these 2 algorithms through a modified sigmoidal function. Moreover, in the first algorithm, to implement a smooth transition from the large step‐size IWF‐SSAF filter to the small step‐size one, the component filters receive a cyclic feedback of the combined weight vector. Both proposed algorithms have almost the same convergence performance, but the second algorithm saves computational cost. Simulation results in impulsive noise scenarios demonstrate the superiority of our proposed algorithms.     

Fault‐tolerant control for wireless networked control systems with an integrated scheduler

This paper addresses a study of fault‐tolerant control (FTC) for wireless networked control systems (WNCSs) in industrial automatic processes. The WNCSs is composed of many subsystems, which operate with different sampling cycles. In order to meet the real‐time requirements and ensure a deterministic data transmission, the time division multiple access (TDMA) mechanism is adopted in WNCSs. The data in WNCSs are transmitted following a TDMA‐based scheduler. According to the periodicity, WNCSs integrated with the scheduler is first formulated as discrete linear time periodic systems (LTPSs). Afterwards, a fault estimation method for LTPSs is developed under a H_∞ performance specification with a regional pole constraint. With the achieved state observer and fault estimator, an FTC strategy for LTPSs is explored. Finally, the proposed methods are verified on a physical experimental WiNC platform. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of geometry parameters of saw‐tooth surface on the feeding velocity of microparts

In this paper, we study experimentally the effect of the geometry parameters of a saw‐tooth surface and a micropart on the motion of the micropart. The experiments are performed for a range of the saw‐tooth pitch p, micropart length l, and exciting frequency f applied to the surface. By the use of particle tracking velocimetry method, we obtain the time‐dependent velocity and then the ensemble‐averaged velocity of the microparts. The results show that the velocity of the micropart increases up to a certain value of pf and then decreases with increasing pf. The widths of the profiles are similar for the same value of the relative scale l/p but the peaks of the profiles are slightly larger and the profiles are shifted leftward for larger pitches of the saw‐tooth surface. It implies that the motion of the micropart depends more on the characteristic surface velocity pf than on the relative scale l/p and that a larger pitch of the sawtooth creates a larger asymmetric force on the micropart. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Digital filter design with state space method for 1‐bit signal processing based on delta‐sigma modulation

One‐bit signal processing based on delta‐sigma modulation has been studied for hardware implementation of signal processing systems. In the 1‐bit signal processing, finite word‐length problems such as overflow and coefficient quantization error occur. To solve the problems, a new design method with state space is proposed in this paper. Digital filters are designed to show the feasibility of the method. First, the L₁/L₂‐sensitivity is shown to evaluate coefficient quantization error and L₂ scaling constraints to prevent overflow. Second, a state space equation is presented and the L₁/L₂‐sensitivity and L₂‐scaling constraints are extended to take the filter structure and oversampling effects into account. Finally, the proposed method is shown to attain a higher SNR than conventional ones. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 48–56, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21075     

Delay‐dependent model reduction for continuous‐time switched state‐delayed systems

This paper studies the problem of exponential H_∞ model reduction for continuous‐time switched delay system under average dwell time (ADT) switching signals. Time delay under consideration is interval time varying. Our attention is focused on the construction of the desired reduced order models, which guarantee that the resulting error systems under ADT switching signals are exponentially stable with an H_∞ norm bound. By introducing a block matrix and making use of the ADT approach, delay‐dependent sufficient conditions for the existence of reduced order models are derived and formulated in terms of strict linear matrix inequalities (LMIs). Owing to the absence of non‐convex constraints, it is tractable to construct an admissible reduced order model. The effectiveness of the proposed methods is illustrated via two numerical examples. Copyright © 2011 John Wiley & Sons, Ltd.     

An equivalent‐circuit modelling on vertical and horizontal integrations for MOS flat‐band voltage simulation

The fixed oxide charge will cause the MOS capacitor (MOS‐C) flat‐band voltage to shift. We can observe the potential distribution to determine the MOS‐C flat‐band voltage. However, the potential distribution can be obtained from the integration of the electric field distribution. The integration of the electric field distribution is classified into the vertical and horizontal integrations. In this paper, we use the equivalent‐circuit model to demonstrate the flat‐band voltage of the non‐ideal MOS‐C. The equivalent‐circuit model of Poisson's equation includes two fixed charges Q′_f1 and Q′_f2 in the oxide layer region. Because the horizontal integration method is the superposition method, the equivalent‐circuit model for the horizontal integration is divided into 3 types. Hence, the flat‐band voltage for the horizontal integration is equal to the sum of the V_G1, V_G2, and V_G3 for the flat‐band condition. By comparison, the simulation results of the horizontal integration method approximate to the vertical integration method. Copyright © 2006 John Wiley & Sons, Ltd.     

Complex two‐dimensional TNIPM for l1 norm‐based sparse optimization to collocated MIMO radar

In collocated multiple‐input multiple‐output (MIMO) radar, because of the sparse nature of the received signal in the three dimensions of range, angle, and Doppler, accurate estimates of range/angle/Doppler parameters can be achieved using a sparse signal recovery. In this paper, we develop a complex two‐dimensional truncated Newton interior point method (2D TNIPM) for l₁‐norm‐based sparse optimization. Because of the 2D sparse representation of received signal in collocated MIMO radar systems, the performance of proposed algorithm is investigated in order to estimate the target position and velocity. Simulation results show that the 2D TNIPM requires much lower computations compared to the 1D one. Also, it outperforms some other 2D algorithms in the estimation of range, angle, and Doppler parameters under low signal‐to‐noise ratios. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Robust l2−l∞ dynamic output feedback control design for uncertain discrete-time switched systems with random time-varying delay

This article deals with the problem of robust output feedback control design for a class of switched systems with uncertainties and random time-varying delay. Our purpose is focused on designing a full order dynamic output feedback controller and an appropriate switching rule to ensure the exponential mean square stability of the resulting closed-loop switching system with an l₂−l_∞ performance level. The appealing aspects of the proposed control scheme include: (a) the development of LMI based delay-dependent sufficient conditions for the exponential stability analysis of the stochastic hybrid systems using the appropriate choice of the augmented Lyapunov–Krasovskii functional, the partitioning technique and the average dwell time, (b) conservatism reduction of the unified design conditions, and (c) the controller designed exhibiting robustness with l₂−l_∞ performance against uncertainties and external disturbance. Finally, representative examples are given to demonstrate the validity and the merit of the proposed design technique.     

An approach to digital implementation of continuous backstepping adaptive control for linear systems

This paper presents a solution to the problem of digitally implementing backstepping adaptive control for linear systems. The continuous‐time system to be controlled is given a discrete‐time representation in the δ‐operator. A discrete adaptive backstepping controller is then designed for such a discrete‐time model. The effect of the modelling error, generated by the sampling process, is accounted for in the parameter update law by a σ‐modification. It is shown that all the signals (discrete and continuous) of the closed loop are uniformly bounded, with a region of attraction which is a K_∞ function of the sampling rate. An upper bound on the asymptotic tracking error is then given, and shown to be proportional to the sampling period. Copyright © 1999 John Wiley & Sons, Ltd.     

An approximation for the input conductivity function of the non‐linear resistive grid

The 2‐term approximations for the input conductivity functions, i_in=f_in(v_in), of a grid of similar weakly non‐linear (parabolic) conductors, and the grid's symmetric cuts, measured between two close nodes, are derived, using a semi‐empirical method; the results of a relevant PSpice simulation are presented. The functions f_in(v_in) of the grid's symmetric cuts possess a common analytical feature. Simulation results show that the error in the calculation of the non‐linear terms in the input functions is less than 1 per cent. Copyright © 2001 John Wiley & Sons, Ltd.     

Accurate one‐terminal fault location algorithm based on the principle of short‐circuit calculation

An alternative method to find the line fault distance in a transmission network employing only one‐terminal measured data is presented. The proposed method applies Z_bus for short‐circuit calculation to find the fault location on a transmission line without the necessity to know the fault type a priori. The well‐known drawback of the standard simple‐reactance one‐terminal algorithm, which neglects the effect of fault impedance, will be minimized by estimating the voltage drop at the fault location by employing the Z_bus technique. Accuracy the proposed method is demonstrated using the short‐circuit simulation of the modified IEEE‐14 bus test system on MATLAB/Simulink and the Simpower Toolbox. Compared to the accuracy obtained from the standard one‐terminal algorithm, test results confirm substantially improved accuracy of the proposed method in all cases of the four types of fault categories: single line‐to‐ground fault; double line‐to‐ground fault; line‐to‐line fault; and balance three‐phase fault. While the accuracy has been significantly improved, especially for the case with a relatively high fault impedance, also the simplicity in the involved computation is well preserved when compared to other iterative‐based techniques. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analytical synthesis of odd/even‐nth‐order elliptic Cauer filter structures using OTRAs

The operational transresistance amplifier (OTRA), the dual of the well‐known operational transconductance amplifier, is an attractive element for use in circuit design. One odd‐nth‐order and two even‐nth‐order OTRA‐R‐C or OTRA‐MOS‐C elliptic Cauer filter structures are presented using new analytical synthesis methods (ASMs). Because it is assumed in the synthesis procedure that the transresistance R_m → ∞, but in view of the fact that R_m is finite in practice, the more the number of OTRAs employed, the worse the precision of the output signals. By studying the sensitivity of the output to component variations, more precise output may be obtained by selecting one or two appropriate capacitance(s)/resistance(s) and adjusting their values suitably. H‐spice simulations are given to validate and demonstrate the theoretical predictions. Copyright © 2012 John Wiley & Sons, Ltd.     

Current‐mode dual‐output ICCII‐based tunable universal biquadratic filter with low‐input and high‐output impedances

A new tunable current‐mode (CM) biquadratic filter with three inputs and three outputs using three dual‐output inverting second‐generation current conveyors, three grounded resistors and two grounded capacitors is proposed. The proposed circuit exhibits low‐input impedance and high‐output impedance which is important for easy cascading in the CM operations. It can realize lowpass, bandpass, highpass, bandreject and allpass biquadratic filtering responses from the same topology. The circuit permits orthogonal controllability of the quality factor Q and resonance angular frequency ω_o, and no component matching conditions or inverting‐type input current signals are imposed. All the passive and active sensitivities are low. Hspice simulation results are based on using TSMC 0.18 µm 1P6M process complementary metal oxide semiconductor technology and supply voltages ±0.9 V to verify the theoretical analysis. Copyright © 2012 John Wiley & Sons, Ltd.