Juan J. Villacorta

A configurable sensor network applied to ambient assisted living.

The rising older people population has increased the interest in Ambient Assisted Living systems. This article presents a system for monitoring the disabled or older persons developed from an existing surveillance system. The modularity and adaptability characteristics of the system allow an easy adaptation for a different purpose. The proposed system uses a network of sensors capable of motion detection that includes fall warning, identification of persons and a configurable control system which allows its use in different scenarios.

Performance Evaluation of a Biometric System Based on Acoustic Images

An acoustic electronic scanning array for acquiring images from a person using a biometric application is developed. Based on pulse-echo techniques, multifrequency acoustic images are obtained for a set of positions of a person (front, front with arms outstretched, back and side). Two Uniform Linear Arrays (ULA) with 15 λ/2-equispaced sensors have been employed, using different spatial apertures in order to reduce sidelobe levels. Working frequencies have been designed on the basis of the main lobe width, the grating lobe levels and the frequency responses of people and sensors. For a case-study with 10 people, the acoustic profiles, formed by all images acquired, are evaluated and compared in a mean square error sense. Finally, system performance, using False Match Rate (FMR)/False Non-Match Rate (FNMR) parameters and the Receiver Operating Characteristic (ROC) curve, is evaluated. On the basis of the obtained results, this system could be used for biometric applications.

Design and Evaluation of a Scalable and Reconfigurable Multi-Platform System for Acoustic Imaging

This paper proposes a scalable and multi-platform framework for signal acquisition and processing, which allows for the generation of acoustic images using planar arrays of MEMS (Micro-Electro-Mechanical Systems) microphones with low development and deployment costs. Acoustic characterization of MEMS sensors was performed, and the beam pattern of a module, based on an 8 × 8 planar array and of several clusters of modules, was obtained. A flexible framework, formed by an FPGA, an embedded processor, a computer desktop, and a graphic processing unit, was defined. The processing times of the algorithms used to obtain the acoustic images, including signal processing and wideband beamforming via FFT, were evaluated in each subsystem of the framework. Based on this analysis, three frameworks are proposed, defined by the specific subsystems used and the algorithms shared. Finally, a set of acoustic images obtained from sound reflected from a person are presented as a case study in the field of biometric identification. These results reveal the feasibility of the proposed system.

Acoustic Biometric System Based on Preprocessing Techniques and Linear Support Vector Machines.

Drawing on the results of an acoustic biometric system based on a MSE classifier, a new biometric system has been implemented. This new system preprocesses acoustic images, extracts several parameters and finally classifies them, based on Support Vector Machine (SVM). The preprocessing techniques used are spatial filtering, segmentation—based on a Gaussian Mixture Model (GMM) to separate the person from the background, masking—to reduce the dimensions of images—and binarization—to reduce the size of each image. An analysis of classification error and a study of the sensitivity of the error versus the computational burden of each implemented algorithm are presented. This allows the selection of the most relevant algorithms, according to the benefits required by the system. A significant improvement of the biometric system has been achieved by reducing the classification error, the computational burden and the storage requirements.

Analysis and design of multifunction radar task schedulers based on queue

Inside the set of systems that constitute the avionics, the radar on board is one of the principal systems, both for the commercial and the military aircraft. For a few years ago, the technologies of electronic exploration arrays are used in the radar design, and specially, in the combat fighters, where the detection and tracking of multiple targets is a fundamental requirement. In this type of environments, it is required to use multifunction radar, MFAR (Multi-Function Array Radar), which joins inside the same system, and simultaneously, so much the classic functions of tracking and surveillance, as all the functions related to the communication, countermeasures, calibration, etc. Thus, the functions are implemented according to specific tasks. The principal ones are: surveillance, tracking, confirmation of false alarm, backscanning, reacquisition and communications plane-missile. Therefore, it is required to work with, specialized subsystems inside the radar. They are called task schedulers. The task scheduler is a key element of the radar, since it does the planning and distribution of energy and time resources to be shared and used by all tasks. This paper analyzes the features of the task schedulers based on tasks queues. Radar time is divided in time intervals that are called scheduling intervals. They allow realizing the task scheduling in a flexible and automatic way, planning individually each interval. Therefore, the task scheduler constitutes, for every scheduling interval, the corresponding queue or queues with the tasks planned to execute in that interval. Then, the tasks that are going to execute are selected from those tasks queues. Therefore, the scheduler includes and applies two scheduling policies: the policy for the constitution of the tasks queues, and the policy of scheduling, which is applied for planning every scheduling interval. Several schedulers have been designed and studied, and it has been made a comparative analysis of different performed schedulers. The tests and experiments have been done by means of system software simulation. Finally a suitable set of radar characteristics has been selected to evaluate the behavior of the task scheduler working.

Analysis of Directive Sensor Influence on Array Beampatterns

Over the past few years, a large number of pattern synthesis techniques of antenna arrays have been studied and developed. Such techniques may be classified into two categories: techniques that optimize the excitation (amplitude and phase) of each element in a uniform array (Van Veen & Buckley, 1988), and techniques that adjust the positions of the elements with uniform excitation, resulting in a non-uniform geometry (“Unz, 1960”, ”Harrington, 1961”, ”Skolnik et al., 1964”, ”Haupt, 1994”). Despite of this classification, both categories are not exclusive; so, it is possible to develop techniques that optimize both the excitations and the positions of the elements (”Akdagli & Guney, 2003”, “Kurup et al., 2003”, “Kumar & Branner, 2005”). It has been also observed that many of these techniques make a beampattern synthesis only in the case of an array pointing to the broadside. Only a few techniques are designed taking into account other angles further than the broadside (“Bae et al., 2005”, “Bray et al., 2002”, “Feng & Chen, 2005”), which is the basis of beamforming. The reason is that, these techniques work on the assumption that the array is formed by omnidirectional sensors. In this case, working with the array pattern in the u domain (u=sen(θ)), a variation of the pointing angle only implies that a shift in the beampattern, without variation of the characteristics of neither the main lobe, nor the sidelobes (Mailloux, 2005). Thus, representing the pattern in the u-u

Using a Planar Array of MEMS Microphones to Obtain Acoustic Images of a Fan Matrix

This paper proposes the use of a signal acquisition and processing system based on an planar array of MEMS (Microelectromechanical Systems) microphones to obtain acoustic images of a fan matrix. A matrix of PC fans has been implemented to perform the study. Some tests to obtain the acoustic images of the individual fans and of the whole matrix have been defined and have been carried out inside an anechoic chamber. The nonstationary signals received by each MEMS microphone and their corresponding spectra have been analyzed, as well as the corresponding acoustic images. The analysis of the acoustic signals spectra reveals the resonance frequency of the individual fans. The obtained results reveal the feasibility of the proposed system to obtained acoustic images of a fan matrix and of its individual fans, in this last case, in order to estimate the real position of the fan inside the matrix.

Security System Technologies Applied to Ambient Assisted Living

The increasing elderly population has increased interest in the Ambient Assisted Living systems. This article presents a system for monitoring the disabled or elderly developed from an existing surveillance system. The modularity and adaptability characteristics of the system allow an easy adaptation for a different purpose. The proposed system uses a network of sensors capable of motion detection that includes fall warning, identification of persons and a configurable control system which allows its use in different scenarios.

VIGICOP: Autonomous surveillance robots with sodar detection and autonomous navigation

The main goal of the project described in this paper is to create a security system using autonomous surveillance robots that use SODAR-like detection system sensors, working with acoustic signals in air environment and navigation base on Geographic Information System and Markovs models. The surveillance system based on SONAR provides great information from the environment, even lets you see behind objects (rebounds effects) whose manipulation offers a great added value to surveillance The guide system will implement in one hand a local navigation module directed to avoid obstacles based on classical techniques and using the new SODAR sensor. On the other hand a global navigation module will be implemented using preset trajectories and gradient techniques and an auto-location system. One of the greatest challenges obtained is the definition of the VIGICOPVar variable that defines, depending on the environment and safety parameters, the probability of intrusion. Surveillance experts of GRUPO NORTE (multinational company with security expertise of more than 38 years) have worked In the definition and validation of the model. The monitoring robots will be controlled in a centralized way from an alarm center from where you can manage all information relating to intrusion detected. VIGICOP is the low cost surveillance robot which provides new/full information interactive surveillance information.

Implementation of a Virtual Microphone Array to Obtain High Resolution Acoustic Images

Using arrays with digital MEMS (Micro-Electro-Mechanical System) microphones and FPGA-based (Field Programmable Gate Array) acquisition/processing systems allows building systems with hundreds of sensors at a reduced cost. The problem arises when systems with thousands of sensors are needed. This work analyzes the implementation and performance of a virtual array with 6400 (80 × 80) MEMS microphones. This virtual array is implemented by changing the position of a physical array of 64 (8 × 8) microphones in a grid with 10 × 10 positions, using a 2D positioning system. This virtual array obtains an array spatial aperture of 1 × 1 m2. Based on the SODAR (SOund Detection And Ranging) principle, the measured beampattern and the focusing capacity of the virtual array have been analyzed, since beamforming algorithms assume to be working with spherical waves, due to the large dimensions of the array in comparison with the distance between the target (a mannequin) and the array. Finally, the acoustic images of the mannequin, obtained for different frequency and range values, have been obtained, showing high angular resolutions and the possibility to identify different parts of the body of the mannequin.