In this paper, we consider the use of a seismic sensor array for the localization and tracking of a wideband
moving source. The proposed solution consists of two steps: source Direction-Of-Arrival (DOA) estimation and
localization via DOA estimates. Three DOA estimation methods are considered. The Covariance Matrix Analysis
and the Surface Wave Analysis are previously published DOA estimation algorithms shown to be effective in the
localization of a stationary wideband source. This paper investigates their performance on moving wideband
sources. A novel DOA estimation algorithm, the Modified Kirlin's Method was also developed for the localization
of a moving source. The DOAs estimated by these algorithms are combined using a least-squares optimization
for source localization. The application of these algorithms to real-life data show the effectiveness of both the
Surface Wave Analysis and the Modified Kirlin's Method in locating and tracking a wideband moving source.
Distributed sensor networks have been proposed for a wide range of applications. In this paper, our goal is to locate a wideband source, generating both acoustic and seismic signals, using both seismic and acoustic sensors. For a far-field acoustic source, only the direction-of-arrival (DOA) in the coordinate system of the sensors is observable. We use the approximate Maximum-Likelihood (AML) method for DOA estimations from severalacoustic arrays. For a seismic source, we use data collected at a single tri-axial accelerometer to perform DOA estimation. Two seismic DOA estimation methods, the eigen-decomposition of the sample covariance matrix method and the surface wave method are used. Field measurements of acoustic and seismic signals generated by vertically striking a heavy metal plate placed on the ground in an open field are collected. Each acoustic array uses four low-cost microphones placed in a square configuration and separated by one meter. The microphone outputs of each array are collected by a synchronized A/D recording system and processed locally based on the AML algorithm for DOA estimation. An array of six tri-axial accelerometers arranged in two rows whose outputs are fed into an ultra low power and high resolution network-aware seismic recording system. Field measured data from the acoustic and seismic arrays show the estimated DOAs and consequent localizations of the source are quite accurate and useful.
A semi-analytic method is presented for analyzing the behavior of layered, circular piezoelectric cylinders under axisymmetric mechanical and electric loads. Discretization occurs in the radial direction so that any number of layers with distinct material properties and thickness can be accommodated. Axial and circumferential behaviors are obtained analytically. Mechanical loads include axial force, torque, longitudinal and circumferential surface shears, and arbitrary pressure distributions. Electric loads include voltage and charge distributions along the axis of the cylinder that may be applied on any layer’s surface. In the present approach, all loads are represented by power series in the axial coordinate. There are several advantages provided by the semi-analytic method. First, as part of the solution is analytic, it is more accurate than any fully discrete (e.g., finite element) method. It is also computationally more efficient than discrete methods as the dimension of the problem is reduced, essentially, by one order. Second, the method is more accurate than technical (beam, plate, shell) theories as the deformation of the cross-section is not constrained by any simplifying kinematic hypothesis. Third, it provides solutions for complex geometry and material distributions for which there are no analytic solutions. The method may be extended to general, nonhomogeneous cross-sectional geometries. Veracity of our implementation is demonstrated by comparing the results for various problems with those obtained via three-dimensional finite element methods. We also provide the analysis of a bimodal actuator to demonstrate the utility of the present technique for evaluating designs of smart structures with layered, axisymmetric geometries.