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Editorial

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Open AccessEditorial

Sensorial Systems Applied to Intelligent Spaces

by José Luis Lázaro-Galilea, Ignacio Bravo-Muñoz and Alfredo Gardel-Vicente

Sensors 2012, 12(8), 10707-10712; https://doi.org/10.3390/s120810707 - 6 Aug 2012

Viewed by 5289

Abstract

The definition of “Intelligent Space” (IS) was formerly proposed for an environmental system capable of offering humans informative and physical support. Currently an IS denotes a space containing human and artificial systems, the space itself being considered an intelligent system. Human and artificial [...] Read more.

The definition of “Intelligent Space” (IS) was formerly proposed for an environmental system capable of offering humans informative and physical support. Currently an IS denotes a space containing human and artificial systems, the space itself being considered an intelligent system. Human and artificial systems become clients of the IS and simultaneously the artificial systems become agents of the IS. Since the whole space is an intelligent system, it is able to monitor and provide services to many different clients with ease. For example, an IS uses electronic displays to provide information to humans, then robots are used to offer physical services to them as physical agents. [...] Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

Research

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810 KiB

Open AccessArticle

Error Estimation for the Linearized Auto-Localization Algorithm

by Jorge Guevara, Antonio R. Jiménez, Jose Carlos Prieto and Fernando Seco

Sensors 2012, 12(3), 2561-2581; https://doi.org/10.3390/s120302561 - 24 Feb 2012

Cited by 1 | Viewed by 6957

Abstract

The Linearized Auto-Localization (LAL) algorithm estimates the position of beacon nodes in Local Positioning Systems (LPSs), using only the distance measurements to a mobile node whose position is also unknown. The LAL algorithm calculates the inter-beacon distances, used for the estimation of the [...] Read more.

The Linearized Auto-Localization (LAL) algorithm estimates the position of beacon nodes in Local Positioning Systems (LPSs), using only the distance measurements to a mobile node whose position is also unknown. The LAL algorithm calculates the inter-beacon distances, used for the estimation of the beacons’ positions, from the linearized trilateration equations. In this paper we propose a method to estimate the propagation of the errors of the inter-beacon distances obtained with the LAL algorithm, based on a first order Taylor approximation of the equations. Since the method depends on such approximation, a confidence parameter τ is defined to measure the reliability of the estimated error. Field evaluations showed that by applying this information to an improved weighted-based auto-localization algorithm (WLAL), the standard deviation of the inter-beacon distances can be improved by more than 30% on average with respect to the original LAL method. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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529 KiB

Open AccessArticle

Ultrasonic Array for Obstacle Detection Based on CDMA with Kasami Codes

by Cristina Diego, Álvaro Hernández, Ana Jiménez, Fernando J. Álvarez, Rebeca Sanz and Joaqúın Aparicio

Sensors 2011, 11(12), 11464-11475; https://doi.org/10.3390/s111211464 - 2 Dec 2011

Cited by 16 | Viewed by 8777

Abstract

This paper raises the design of an ultrasonic array for obstacle detection based on Phased Array (PA) techniques, which steers the acoustic beam through the environment by electronics rather than mechanical means. The transmission of every element in the array has been encoded, [...] Read more.

This paper raises the design of an ultrasonic array for obstacle detection based on Phased Array (PA) techniques, which steers the acoustic beam through the environment by electronics rather than mechanical means. The transmission of every element in the array has been encoded, according to Code Division for Multiple Access (CDMA), which allows multiple beams to be transmitted simultaneously. All these features together enable a parallel scanning system which does not only improve the image rate but also achieves longer inspection distances in comparison with conventional PA techniques. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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631 KiB

Open AccessArticle

Modeling the Behavior of an Underwater Acoustic Relative Positioning System Based on Complementary Set of Sequences

by Joaquín Aparicio, Ana Jiménez, Fernando J. Álvarez, Jesús Ureña, Carlos De Marziani and Cristina Diego

Sensors 2011, 11(12), 11188-11205; https://doi.org/10.3390/s111211188 - 28 Nov 2011

Cited by 8 | Viewed by 8023

Abstract

The great variability usually found in underwater media makes modeling a challenging task, but helpful for better understanding or predicting the performance of future deployed systems. In this work, an underwater acoustic propagation model is presented. This model obtains the multipath structure by [...] Read more.

The great variability usually found in underwater media makes modeling a challenging task, but helpful for better understanding or predicting the performance of future deployed systems. In this work, an underwater acoustic propagation model is presented. This model obtains the multipath structure by means of the ray tracing technique. Using this model, the behavior of a relative positioning system is presented. One of the main advantages of relative positioning systems is that only the distances between all the buoys are needed to obtain their positions. In order to obtain the distances, the propagation times of acoustic signals coded by Complementary Set of Sequences (CSS) are used. In this case, the arrival instants are obtained by means of correlation processes. The distances are then used to obtain the position of the buoys by means of the Multidimensional Scaling Technique (MDS). As an early example of an application using this relative positioning system, a tracking of the position of the buoys at different times is performed. With this tracking, the surface current of a particular region could be studied. The performance of the system is evaluated in terms of the distance from the real position to the estimated one. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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2284 KiB

Open AccessArticle

Fuzzy Mobile-Robot Positioning in Intelligent Spaces Using Wireless Sensor Networks

by David Herrero and Humberto Martínez

Sensors 2011, 11(11), 10820-10839; https://doi.org/10.3390/s111110820 - 17 Nov 2011

Cited by 16 | Viewed by 7288

Abstract

This work presents the development and experimental evaluation of a method based on fuzzy logic to locate mobile robots in an Intelligent Space using Wireless Sensor Networks (WSNs). The problem consists of locating a mobile node using only inter-node range measurements, which are [...] Read more.

This work presents the development and experimental evaluation of a method based on fuzzy logic to locate mobile robots in an Intelligent Space using Wireless Sensor Networks (WSNs). The problem consists of locating a mobile node using only inter-node range measurements, which are estimated by radio frequency signal strength attenuation. The sensor model of these measurements is very noisy and unreliable. The proposed method makes use of fuzzy logic for modeling and dealing with such uncertain information. Besides, the proposed approach is compared with a probabilistic technique showing that the fuzzy approach is able to handle highly uncertain situations that are difficult to manage by well-known localization methods. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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5238 KiB

Open AccessArticle

Analysis of Doppler Effect on the Pulse Compression of Different Codes Emitted by an Ultrasonic LPS

by José A. Paredes, Teodoro Aguilera, Fernando J. Álvarez, Jesús Lozano and Jorge Morera

Sensors 2011, 11(11), 10765-10784; https://doi.org/10.3390/s111110765 - 15 Nov 2011

Cited by 27 | Viewed by 7954

Abstract

This work analyses the effect of the receiver movement on the detection by pulse compression of different families of codes characterizing the emissions of an Ultrasonic Local Positioning System. Three families of codes have been compared: Kasami, Complementary Sets of Sequences and Loosely [...] Read more.

This work analyses the effect of the receiver movement on the detection by pulse compression of different families of codes characterizing the emissions of an Ultrasonic Local Positioning System. Three families of codes have been compared: Kasami, Complementary Sets of Sequences and Loosely Synchronous, considering in all cases three different lengths close to 64, 256 and 1,024 bits. This comparison is first carried out by using a system model in order to obtain a set of results that are then experimentally validated with the help of an electric slider that provides radial speeds up to 2 m/s. The performance of the codes under analysis has been characterized by means of the auto-correlation and cross-correlation bounds. The results derived from this study should be of interest to anyone performing matched filtering of ultrasonic signals with a moving emitter/receiver. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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892 KiB

Open AccessArticle

LPS Auto-Calibration Algorithm with Predetermination of Optimal Zones

by Francisco Daniel Ruiz, Jesús Ureña, Juan C. García, Ana Jiménez, Álvaro Hernández and Juan J. García

Sensors 2011, 11(11), 10398-10414; https://doi.org/10.3390/s111110398 - 31 Oct 2011

Cited by 5 | Viewed by 7213

Abstract

Accurate coordinates for active beacons placed in the environment are required in Local Positioning Systems (LPS). These coordinates and the distances (or differences of distances) measured between the beacons and the mobile node to be localized are inputs to most trilateration algorithms. As [...] Read more.

Accurate coordinates for active beacons placed in the environment are required in Local Positioning Systems (LPS). These coordinates and the distances (or differences of distances) measured between the beacons and the mobile node to be localized are inputs to most trilateration algorithms. As a first approximation, such coordinates are obtained by means of manual measurements (a time-consuming and non-flexible method), or by using a calibration algorithm (i.e., automatic determination of beacon coordinates from ad hoc measurements). This paper presents a method to calibrate the beacons’ positions in a LPS using a mobile receiver. The method has been developed for both, spherical and hyperbolic trilateration. The location of only three test points must be known a priori, while the position of the other test points can be unknown. Furthermore, the paper describes a procedure to estimate the optimal positions, or approximate areas in the coverage zone, where the test-points necessary to calibrate the ultrasonic LPS should be placed. Simulation and experimental results show the improvement achieved when these optimal test-points are used instead of randomly selected ones. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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661 KiB

Open AccessArticle

Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation

by José Manuel Villladangos, Jesús Ureña, Juan Jesús García, Manuel Mazo, Álvaro Hernández, Ana Jiménez, Daniel Ruíz and Carlos De Marziani

Sensors 2011, 11(11), 10326-10342; https://doi.org/10.3390/s111110326 - 31 Oct 2011

Cited by 28 | Viewed by 10184

Abstract

In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. [...] Read more.

In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the Generalized Cross-Correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the Time Differences of Arrival (TDOA) between a reference beacon and the others. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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8981 KiB

Open AccessArticle

PDR with a Foot-Mounted IMU and Ramp Detection

by Antonio R. Jiménez, Fernando Seco, Francisco Zampella, José C. Prieto and Jorge Guevara

Sensors 2011, 11(10), 9393-9410; https://doi.org/10.3390/s111009393 - 29 Sep 2011

Cited by 57 | Viewed by 11813

Abstract

The localization of persons in indoor environments is nowadays an open problem. There are partial solutions based on the deployment of a network of sensors (Local Positioning Systems or LPS). Other solutions only require the installation of an inertial sensor on the person’s [...] Read more.

The localization of persons in indoor environments is nowadays an open problem. There are partial solutions based on the deployment of a network of sensors (Local Positioning Systems or LPS). Other solutions only require the installation of an inertial sensor on the person’s body (Pedestrian Dead-Reckoning or PDR). PDR solutions integrate the signals coming from an Inertial Measurement Unit (IMU), which usually contains 3 accelerometers and 3 gyroscopes. The main problem of PDR is the accumulation of positioning errors due to the drift caused by the noise in the sensors. This paper presents a PDR solution that incorporates a drift correction method based on detecting the access ramps usually found in buildings. The ramp correction method is implemented over a PDR framework that uses an Inertial Navigation algorithm (INS) and an IMU attached to the person’s foot. Unlike other approaches that use external sensors to correct the drift error, we only use one IMU on the foot. To detect a ramp, the slope of the terrain on which the user is walking, and the change in height sensed when moving forward, are estimated from the IMU. After detection, the ramp is checked for association with one of the existing in a database. For each associated ramp, a position correction is fed into the Kalman Filter in order to refine the INS-PDR solution. Drift-free localization is achieved with positioning errors below 2 meters for 1,000-meter-long routes in a building with a few ramps. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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1218 KiB

Open AccessArticle

An Architecture for Performance Optimization in a Collaborative Knowledge-Based Approach for Wireless Sensor Networks

by Manuel Angel Gadeo-Martos, Jose Angel Fernandez-Prieto, Joaquin Canada-Bago and Juan Ramon Velasco

Sensors 2011, 11(10), 9136-9159; https://doi.org/10.3390/s111009136 - 27 Sep 2011

Cited by 9 | Viewed by 7446

Abstract

Over the past few years, Intelligent Spaces (ISs) have received the attention of many Wireless Sensor Network researchers. Recently, several studies have been devoted to identify their common capacities and to set up ISs over these networks. However, little attention has been paid [...] Read more.

Over the past few years, Intelligent Spaces (ISs) have received the attention of many Wireless Sensor Network researchers. Recently, several studies have been devoted to identify their common capacities and to set up ISs over these networks. However, little attention has been paid to integrating Fuzzy Rule-Based Systems into collaborative Wireless Sensor Networks for the purpose of implementing ISs. This work presents a distributed architecture proposal for collaborative Fuzzy Rule-Based Systems embedded in Wireless Sensor Networks, which has been designed to optimize the implementation of ISs. This architecture includes the following: (a) an optimized design for the inference engine; (b) a visual interface; (c) a module to reduce the redundancy and complexity of the knowledge bases; (d) a module to evaluate the accuracy of the new knowledge base; (e) a module to adapt the format of the rules to the structure used by the inference engine; and (f) a communications protocol. As a real-world application of this architecture and the proposed methodologies, we show an application to the problem of modeling two plagues of the olive tree: prays (olive moth, Prays oleae Bern.) and repilo (caused by the fungus Spilocaea oleagina). The results show that the architecture presented in this paper significantly decreases the consumption of resources (memory, CPU and battery) without a substantial decrease in the accuracy of the inferred values. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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837 KiB

Open AccessArticle

Weighted Least Squares Techniques for Improved Received Signal Strength Based Localization

by Paula Tarrío, Ana M. Bernardos and José R. Casar

Sensors 2011, 11(9), 8569-8592; https://doi.org/10.3390/s110908569 - 2 Sep 2011

Cited by 118 | Viewed by 11987

Abstract

The practical deployment of wireless positioning systems requires minimizing the calibration procedures while improving the location estimation accuracy. Received Signal Strength localization techniques using propagation channel models are the simplest alternative, but they are usually designed under the assumption that the radio propagation [...] Read more.

The practical deployment of wireless positioning systems requires minimizing the calibration procedures while improving the location estimation accuracy. Received Signal Strength localization techniques using propagation channel models are the simplest alternative, but they are usually designed under the assumption that the radio propagation model is to be perfectly characterized a priori. In practice, this assumption does not hold and the localization results are affected by the inaccuracies of the theoretical, roughly calibrated or just imperfect channel models used to compute location. In this paper, we propose the use of weighted multilateration techniques to gain robustness with respect to these inaccuracies, reducing the dependency of having an optimal channel model. In particular, we propose two weighted least squares techniques based on the standard hyperbolic and circular positioning algorithms that specifically consider the accuracies of the different measurements to obtain a better estimation of the position. These techniques are compared to the standard hyperbolic and circular positioning techniques through both numerical simulations and an exhaustive set of real experiments on different types of wireless networks (a wireless sensor network, a WiFi network and a Bluetooth network). The algorithms not only produce better localization results with a very limited overhead in terms of computational cost but also achieve a greater robustness to inaccuracies in channel modeling. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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819 KiB

Open AccessArticle

Infrared Sensor System for Mobile-Robot Positioning in Intelligent Spaces

by Ernesto Martín Gorostiza, José Luis Lázaro Galilea, Franciso Javier Meca Meca, David Salido Monzú, Felipe Espinosa Zapata and Luis Pallarés Puerto

Sensors 2011, 11(5), 5416-5438; https://doi.org/10.3390/s110505416 - 18 May 2011

Cited by 89 | Viewed by 12887

Abstract

The aim of this work was to position a Mobile Robot in an Intelligent Space, and this paper presents a sensorial system for measuring differential phase-shifts in a sinusoidally modulated infrared signal transmitted from the robot. Differential distances were obtained from these phase-shifts, [...] Read more.

The aim of this work was to position a Mobile Robot in an Intelligent Space, and this paper presents a sensorial system for measuring differential phase-shifts in a sinusoidally modulated infrared signal transmitted from the robot. Differential distances were obtained from these phase-shifts, and the position of the robot was estimated by hyperbolic trilateration. Due to the extremely severe trade-off between SNR, angle (coverage) and real-time response, a very accurate design and device selection was required to achieve good precision with wide coverage and acceptable robot speed. An I/Q demodulator was used to measure phases with one-stage synchronous demodulation to DC. A complete set of results from real measurements, both for distance and position estimations, is provided to demonstrate the validity of the system proposed, comparing it with other similar indoor positioning systems. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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Review

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Open AccessReview

Local Positioning Systems in (Game) Sports

by Roland Leser, Arnold Baca and Georg Ogris

Sensors 2011, 11(10), 9778-9797; https://doi.org/10.3390/s111009778 - 19 Oct 2011

Cited by 80 | Viewed by 12868

Abstract

Position data of players and athletes are widely used in sports performance analysis for measuring the amounts of physical activities as well as for tactical assessments in game sports. However, positioning sensing systems are applied in sports as tools to gain objective information [...] Read more.

Position data of players and athletes are widely used in sports performance analysis for measuring the amounts of physical activities as well as for tactical assessments in game sports. However, positioning sensing systems are applied in sports as tools to gain objective information of sports behavior rather than as components of intelligent spaces (IS). The paper outlines the idea of IS for the sports context with special focus to game sports and how intelligent sports feedback systems can benefit from IS. Henceforth, the most common location sensing techniques used in sports and their practical application are reviewed, as location is among the most important enabling techniques for IS. Furthermore, the article exemplifies the idea of IS in sports on two applications. Full article

(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

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