In this study, we present a novel relaxed-intensified exploration algorithm (RIEA) to synthesize large-aperture sensorarrays producing good array sparsity and optimal weight vector of the sparse sensor arrays for sen...
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In this study, we present a novel relaxed-intensified exploration algorithm (RIEA) to synthesize large-aperture sensorarrays producing good array sparsity and optimal weight vector of the sparse sensor arrays for sensing unmanned aerial vehicles (UAVs) in airspace. The proposed algorithm is based on the compressed-sensing framework integrated with a kind of relaxed-intensified optimization thought, which comprises two core stages: the relaxed optimization stage and the intensified reoptimization stage. The relaxed-intensified exploration algorithm (RIEA) is tailored to accelerate array synthesis efficiency and promote global optimization. For the proposed algorithm, the ability to approach the global convergence is embodied in two key stages. The first stage aims to generate an optimal sparsesensor array with arbitrary upper mask constraints, whose upper mask is slightly relaxed to expand the solution space for further enhancing the array sparsity. Meanwhile, direction dimension reduction is further conducted to relax the radiating direction matrix for reducing massive computational cost. For the intensified reoptimization stage, the "relaxed" upper mask is first readjusted back to the strictly constrained strength and the weight vector of the designed sparsesensor array in the previous stage is then further optimized to approach the global optimal solution. Finally, the presence of element pattern for an individual sensor and array beam-scanning capability are also considered and investigated in synthesizing the sparse sensor arrays for precise positioning and sensing of UAVs. Several representative examples of the small/large-aperture sparse sensor arrays are performed to demonstrate the superiority, effectiveness, and robustness of the proposed RIEA.
Ultrasonic guided waves offer the possibility of inspecting large areas of structures from a small number of sensor positions. However, inspection of complex structures is difficult as the reflections from different f...
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Ultrasonic guided waves offer the possibility of inspecting large areas of structures from a small number of sensor positions. However, inspection of complex structures is difficult as the reflections from different features overlap. Estimating the number and amplitude of the wave packets in ultrasonic time traces is crucial for the development of a guided wave inspection system, in order to detect and locate damage. Deconvolution has been extensively used in geophysical applications to resolve overlapping echoes in the recorded signals. The main objective of this work was to evaluate the applicability of the deconvolution approach for enhancing the resolution of ultrasonic time traces in structural health monitoring (SHM). Numerical simulations on strongly overlapping signals were carried out to evaluate the performance of the two techniques that have been considered: (i) Wiener filter, (ii) single most likely replacement. It was shown that the relatively narrow bandwidth of the input signals and phase shifts between different reflections limit the benefits obtained from deconvolution and it was concluded that deconvolution is unlikely to be useful for guided wave SHM applications.
An l(0)-norm constrained normalized LMS algorithm (L-0-CNLMS) is proposed to find out the solution of the thinned array adaptive beamforming. The proposed L-0-CNLMS integrates an additional l(0)-norm penalty on the fi...
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ISBN:
(纸本)9781538671023
An l(0)-norm constrained normalized LMS algorithm (L-0-CNLMS) is proposed to find out the solution of the thinned array adaptive beamforming. The proposed L-0-CNLMS integrates an additional l(0)-norm penalty on the filter coefficients compared with the constrained NLMS (CNLMS) algorithm, which aims to seek the solution towards sparsity and finally thinned array. To reduce the computation burden, an approximating l(0)-norm method is presented and integrated into the CNLMS algorithm. The simulation experiments are created to show that the L-0-CNLMS algorithm is effective in sparse adaptive beamforming.
sparse array processing methods are typically used to improve the spatial resolution of sensorarrays for the estimation of direction of arrival (DOA). The fundamental assumption behind these methods is that signals t...
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ISBN:
(纸本)0819453404
sparse array processing methods are typically used to improve the spatial resolution of sensorarrays for the estimation of direction of arrival (DOA). The fundamental assumption behind these methods is that signals that are received by the sparsesensors (or a group of sensors) are coherent. However, coherence may vary significantly with the changes in environmental, terrain, and, operating conditions. In this paper canonical correlation analysis is used to study the variations in coherence between pairs of sub-arrays in a sparse array problem. The data set for this study is a subset of an acoustic signature data set, acquired from the US Army TACOM-ARDEC, Picatinny Arsenal, NJ. This data set is collected using three wagon-wheel type arrays with five microphones. The results show that in nominal operating conditions, i.e. no extreme wind noise or masking effects by trees, building, etc., the signals collected at different sensorarrays are indeed coherent even at distant node separation.
The problem of detection, tracking and localization of multiple wideband sources (ground vehicles) using unattended passive acoustic sensors is considered in this paper. Existing methods typically fail to detect, reso...
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ISBN:
(纸本)0819453404
The problem of detection, tracking and localization of multiple wideband sources (ground vehicles) using unattended passive acoustic sensors is considered in this paper. Existing methods typically fail to detect, resolve and track multiple closely spaced sources in tight formations, especially in the presence of clutter and wind noise. In this paper, several existing wideband direction of arrival (DOA) estimation algorithms are extended and applied to this problem. A modified version of the Steered Covariance Matrix (STCM) algorithm is presented that uses a two-step search process. To overcome the problems of existing DOA estimation methods, new wideband versions of the narrowband Capon beamforming method are proposed that use various algorithms for combining power spectra from different frequency bins. These methods are then implemented and benchmarked on a real acoustic signature data set that contains multiple ground targets moving in tight formations.
This paper introduces a constrained normalized adaptive sparse array beamforming algorithm based on approximate L-0-norm and logarithmic cost (L-0-CNLMLS). The proposed algorithm can control the sparsity of the array ...
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This paper introduces a constrained normalized adaptive sparse array beamforming algorithm based on approximate L-0-norm and logarithmic cost (L-0-CNLMLS). The proposed algorithm can control the sparsity of the array by introducing an approximate function of L-0-norm. In addition, the introduction of logarithmic cost improves the stability of the algorithm as well as the convergence rate of the algorithm. The sparsity of the array can be controlled when adjusting related parameter in the proposed algorithm. Simulation results show the better performance of L-0-CNLMLS compared with some conventional algorithms.
We detail in this paper an L-1-norm Linearly constrained normalized least-mean-square (L-1-CNLMS) algorithm and its weighted version (L-1-WCNLMS) applied to solve problems whose solutions have some degree of sparsity,...
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We detail in this paper an L-1-norm Linearly constrained normalized least-mean-square (L-1-CNLMS) algorithm and its weighted version (L-1-WCNLMS) applied to solve problems whose solutions have some degree of sparsity, such as the beam-forming problem in uniform linear arrays, standard hexagonal arrays, and (non-standard) hexagonal antenna arrays. In addition to the linear constraints present in the CNLMS algorithm, the L-1-WCNLMS and the L-1-CNLMS algorithms take into account an L-1-norm penalty on the filter coefficients, which results in sparse solutions producing thinned arrays. The effectiveness of both algorithms is demonstrated via computer simulations. When employing these algorithms to antenna array problems, the resulting effect due to the -norm constraint is perceived as a large aperture array with few active elements. Although this work focuses the algorithm on antenna array synthesis, its application is not limited to them, i.e., the L-1-CNLMS is suitable to solve other problems like sparse system identification and signal reconstruction, where the weighted version, the L-1-WCNLMS algorithm, presents superior performance compared to the L-1-CNLMS algorithm.
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