Coherent l1‐SVD method for DOA estimation of wideband signals

The l₁‐SVD is an efficient method for spatial sparsity based direction of arrival (DOA) estimation of narrowband signals. We propose a coherent strategy for extension of the l₁‐SVD method to wideband signals. In this method, focusing matrices are used for transferring different frequency bins data to the reference bin, and then the transformed data are combined. Finally the l₁‐SVD is applied for the combined data. The proposed method outperforms the non‐coherent strategy with a lower computational burden. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于CS阵列的DOA估计

基于目标在空域分布稀疏的性质,通过引入压缩感知(Compressive Sensing或Compressive Sampling,CS)理论的思想,提出一种基于奇异值分解的压缩采样阵列(SVD-CSA)DOA估计算法。首先建立DOA压缩感知模型,根据阵列结构建立过完备原子库,然后对压缩采样阵列结构输出的数据矩阵进行奇异值分解,最后基于范数约束的最优化问题的目标函数将信号子空间分解到最佳基向量上,实现了空域信号DOA的高分辨估计。相对于已有算法,该算法减少了硬件复杂度,具有较低的运算量,且能够对相干信号进行有效DOA估计。实验仿真验证了其有效性。     

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.     

相干信源DOA估计算法研究

相干信源DOA估计是阵列信号处理的一个研究热点。而空间平滑技术是目前一种较有效的降维类解相干处理算法,但它是通过牺牲阵列有效阵元数来换取解相干能力的,阵列孔径有一定的损失。本文提出了一种新的平滑去相干算法,该算法基于传感器阵列数据快照的基础上,采用前后向平移技术,使用同一几何阵列构造三个虚拟子阵,没有物理孔径损失,该算法对三个子阵列的数据协方差矩阵进行前后向平均,再采用传统的MUSIC算法进行DOA估计。仿真结果表明该算法比传统的平滑算法有更好的估计性能。     

基于稀疏加权重构的互耦阵列方位估计算法

为降低阵元互耦对目标方位估计的影响,提高估计精确度,提出了一种基于稀疏信号加权重构的多目标方位估计算法.该算法将空间以1.为间隔,划分为网格.利用空域目标方位的稀疏性,给出了基于Capon谱函数的加权值选取方法.然后,运用稀疏重构方法和奇异值分解方法对信号进行降维处理.最后,通过L1范数约束优化模型进行DOA估计.仿真结果表明,相比于传统算法,所提出的算法具有更高的方位估计精度、更低的均方根误差,能更好地抑制阵元互耦对目标方位估计的影响.     

对数螺旋阵列的相干信号 DOA 估计研究

在对数螺旋阵相干信号DOA估计的研究中,本文提出一种VA-MMUSIC算法,把对数螺旋阵虚拟成均匀线阵,推导出虚拟后阵列的协方差矩阵,再将协方差矩阵应用到MMUSIC算法中,对相干信号进行DOA估计。仿真结果表明,VA-MMUSIC算法,能够实现对相干信号的DOA估计,且在信噪比为10 dB,信号间隔在5°以内时,VA-MMUSIC算法依然能准确地估计出相干信号源的方位角,误差始终保持在0.5°内,验证了此方法的有效性。并在实际实验条件下利用对数螺旋阵列接收相干信号源数据,验证了实际环境下VA-MMUSIC算法的有效性。     

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.     

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.     

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.     

Performance analysis of velocity–pressure smoothing for direction‐of‐arrival estimation of coherent signals

In this paper, we consider the problem of direction‐of‐arrival (DOA) estimation of coherent signals by using a number of identically oriented acoustic vector‐sensors, wherein source decorrelation can be achieved by velocity–pressure smoothing. We examine the effect of velocity–pressure smoothing on the performance of MUSIC‐type methods in terms of the overall root mean‐square errors (RMSE) of DOA estimates. The closed‐form expression for the overall RMSE is derived and analyzed. We also compare velocity–pressure smoothing with the conventional spatial smoothing technique. Simulation results are given to confirm the analyses. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

基于模式空间处理的宽带测向算法

基于模式空间处理方法提出了一种不需要角度预估计的宽带空间谱估计算法,将总体最小二乘相干信号子空间算法(TLS-CSM)中的聚焦矩阵的构造方法和频率加权聚焦方法引入模式空间宽带空间谱估计算法中,结合了模式空间算法不需要角度预估计的优点和酉聚焦的无聚焦信噪比损失的特性,大大减小了聚焦过程中的信噪比损失,从而进一步提高了算法的性能。     

Order and parameter estimation of time‐varying system by subspace method

This paper proposes an identification algorithm for time‐varying systems. We apply subspace method for estimation, since it is known to be useful when the input–output (I/O) data are observed by multi‐input multi‐output (MIMO) systems. Among many proposed techniques of subspace methods, we use MOESP (MIMO Output‐Error State Space model identification) in this paper, which assures arithmetic stability by RQ factorization and singular value decomposition (SVD). Generally, subspace methods can be applied after I/O data collection, so that we introduce updated steps of matrices for PI‐MOESP, which uses past inputs for instrumental variables. We propose a recursive update algorithm of PI‐MOESP, including estimation step of the system order, and consider some parameters inherent to the algorithm, namely, initial number of data, estimation step of the order, and forgetting factor. A numerical example shows the usefulness of the proposed method. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 57–64, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20169     

Operating methods for two‐way behavior shape memory polymer actuators without using external stress

Operating methods for two‐way behavior shape memory polymer (SMP) actuators have been developed and characterized. Since the shape memory effect of the SMP is one way, an external force to deform the SMP has also been used in conventional SMP actuators. We propose two operating methods: the double SMP layer method and the single SMP layer method. The double SMP layer method uses the shape memory effects of two kinds of SMPs with different glass transition temperatures (T_g1 and T_g2, T_g1 < T_g2). In this method, after a memory shape relating to T_g1 is formed, the generated memory shape relating to T_g2 cancels the previous memory shape at T_g2, i.e. the memory shape of T_g2 is set to the reverse shape of the memory shape of T_g1. The single SMP layer method uses the shape memory effect and thermal contraction of the SMP while it is cooling. In this method, a generated memory shape above T_g is returned to the pre‐memory shape by thermal shrinkage of the SMP when the SMP is cooled down below T_g. SMPs of the polyurethane series are chosen for these actuators. We confirmed that the proposed operating principles functioned experimentally by using prototype actuators of a cantilever beam and examining their fundamental characteristics. These operating methods need only a temperature cycle of heating and cooling and are suitable for small actuators such as microelectromechanical systems (MEMS). © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A cascade‐connected neural model for improved 2D DOA estimation of an EM signal

This article proposes a neural network‐based approach to increase accuracy of two‐dimensional direction of arrival (DOA) estimation of an electromagnetic signal. The proposed method combines two neural networks developed using simulated and small amount of empirical data, respectively. The output of the simulation‐based neural network represents approximate information on DOAs. It is then considered as a priori knowledge for the small empirical network that is crucial for obtaining more accurate DOA estimates. The developed cascade‐connected model is validated using real data from a rectangular antenna array. Improvements in terms of accuracy and reliability are obtained and compared with the MUSIC algorithm. Copyright © 2015 John Wiley & Sons, Ltd.     

Estimation of metabolite <Emphasis Type="Italic">T</Emphasis><Subscript>1</Subscript> relaxation times using tissue specific analysis,signal averaging and bootstrapping from magnetic resonance spectroscopic imaging data

Object A novel method of estimating metabolite T ₁ relaxation times using MR spectroscopic imaging (MRSI) is proposed. As opposed to conventional single-voxel metabolite T ₁ estimation methods, this method investigates regional and gray matter (GM)/white matter (WM) differences in metabolite T ₁ by taking advantage of the spatial distribution information provided by MRSI. Material and methods The method, validated by Monte Carlo studies, involves a voxel averaging to preserve the GM/WM distribution, a non-linear least squares fit of the metabolite T ₁ and an estimation of its standard error by bootstrapping. It was applied in vivo to estimate the T ₁ of N-acetyl compounds (NAA), choline, creatine and myo-inositol in eight normal volunteers, at 1.5 T, using a short echo time 2D-MRSI slice located above the ventricles. Results WM-T _1,NAA was significantly (P < 0.05) longer in anterior regions compared to posterior regions of the brain. The anterior region showed a trend of a longer WM T ₁ compared to GM for NAA, creatine and myo-Inositol. Lastly, accounting for the bootstrapped standard error estimate in a group mean T ₁ calculation yielded a more accurate T ₁ estimation. Conclusion The method successfully measured in vivo metabolite T ₁ using MRSI and can now be applied to diseased brain.     

Simulation on locating Partial Discharge source occurring on distribution line by estimating the DOA of emitted EM waves

A new method for locating the position of partial discharge (PD), which occurs on distribution line, is presented. The method uses the direction‐of‐arrival (DOA) of electromagnetic (EM) waves emitted from PD source. The DOAs of EM waves in azimuth and elevation angles are estimated by using the two‐dimensional improved coherent signal subspace method (2D I‐CSM). The position of PD can be located as the intersection of DOAs estimated at two points. In this paper, the finite difference time domain (FDTD) method is applied to simulate the propagation of EM waves emitted from PD, which occurs on distribution line. The proposed method is applied to locate the position of PD based on the simulation results. The method is shown to be useful for locating the position of PD in multipath environment. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

H∞ filtering for continuous‐time singular systems with time‐varying delay

This paper focuses on H_∞ filter design for continuous‐time singular systems with time‐varying delay. A delay‐dependent H_∞ performance analysis result is first established for error systems via a novel estimation method. By combining a well‐known inequality with a delay partition technique, the upper bound of the derivative of the Lyapunov functional is estimated more tightly and expressed as a convex combination with respect to the reciprocal of the delay rather than the delay. Based on the derived H_∞ performance analysis results, a regular and impulse‐free H_∞ filter is designed in terms of linear matrix inequalities (LMIs). A numerical example is given to demonstrate the merits of the proposed method. Copyright © 2010 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.     

An example of dB/dt characteristics of the dynamic magnetic loss parameter

Ferrite cores are used for power electronics circuits operating under excitation conditions of frequency ranging from hundreds of kilohertz to several tens of megahertz. Development of a mathematical model enabling the estimation of the power loss of ferrites in high‐frequency regions, contributes to the designing of power circuits. The power loss in high‐frequency regions consists of hysteresis and dynamic magnetic losses. Although hysteresis loss does not depend on the excitation frequency, the dynamic magnetic loss increases with increasing excitation frequency. The dynamic magnetic loss parameter, λ_f, has been introduced for identifying the power loss in high‐frequency regions. In this study, λ_f − dB/dt characteristics are experimentally obtained by a newly introduced hysteresis model that uses a normal distribution function. It is found that the λ_f − dB/dt characteristics do not depend on the size of B − H loops. The instantaneous power loss of a ferrite core in the high‐frequency region can be calculated using the λ_f − dB/dt characteristics. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.