Showing papers by "J.M. Villadangos published in 2007"
TL;DR: The main advantage of this proposal is to permit the coexistence of an unlimited number of portable receivers, what is useful in applications like multirobot cooperation.
67 citations
01 Oct 2007
TL;DR: This work describes the design of a ultrasonic local positioning system (ULPS) with large covered area, designed with a cylindrical PVDF transducer to which a conical reflector has been connected to enlarge the covered area and to guarantee 3D indoor positioning.
Abstract: This work describes the design of a ultrasonic local positioning system (ULPS) with large covered area. The beacons have been designed with a cylindrical PVDF transducer (piezofilm transducer) to which a conical reflector has been connected to enlarge the covered area and to guarantee 3D indoor positioning. The proposed ULPS for mobile robots (MR) uses simultaneous emissions from ultrasonic beacons. In order to solve the problem of simultaneous emissions from ultrasonic beacons, the well-known technique, direct sequence code multiple division access (DS-CDMA), is used. This technique encodes the ultrasonic signal with a 255-bit Kasami code for every beacon. It implies the emitted signal by every beacon to have a wide bandwidth. PVDF-based transducers suitably guarantee this requirement. Their cylindrical or semi-cylindrical shape makes the emission pattern not suitable when using them as ultrasonic beacons, often located in the ceiling of an indoor room. To adapt the emission pattern and to increase the covered area in the ground, the design process of a conical reflector is described.
25 citations
01 Oct 2007
TL;DR: This work presents the development of a local positioning system (LPS), based on the transmission of ultrasonic signals, which have been previously encoded by loosely synchronous (LS) codes, if the relative time-offset of the codes are within the IFW.
Abstract: This work presents the development of a local positioning system (LPS), based on the transmission of ultrasonic signals, which have been previously encoded by loosely synchronous (LS) codes. The LPS consists of several ultrasonic emitters located at known positions in the environment, and of a portable receiver that computes its position by measuring the differences in times of arrival (DTOA) between a reference emitter and the others. LS codes exhibit an interference free window (IFW) in the auto-correlation and cross-correlation functions. Therefore, if the relative time-offset of the codes are within the IFW, it is possible to have simultaneous emissions without interference, as well as to reduce the multipath effect.
16 citations
04 Jun 2007
TL;DR: In this article, the design of a reflector for a PVDF-based ultrasonic transducer (Piezofilm transducers) to carry out a ultrasonic beacon system, where the covered area was improved and a 3D indoor positioning was guaranteed.
Abstract: This work describes the design of a reflector for a PVDF-based ultrasonic transducer (Piezofilm transducer) to carry out a ultrasonic beacon system, where the covered area be improved and a 3D indoor positioning be guaranteed. The proposed Local Positioning System (LPS) for Mobile Robots (MR) uses simultaneous emissions from ultrasonic beacons. In order to solve the problem of simultaneous emissions from ultrasonic beacons, the well-known technique Direct Sequence Code Multiple Division Access (DS-CDMA) is used. This technique encodes the ultrasonic signal with a 127-bit Gold code for every beacon. It implies the emitted signal by every beacon to have a wide bandwidth. PVDF-based transducers suitably guarantee this requirement. Their cylindrical or semi-cylindrical shape makes the emission pattern not suitable when using them as ultrasonic beacons, often located in the ceiling of an indoor room. To adapt the emission pattern and to increase the covered area in the ground, the design process of a conical reflector is described.
12 citations
04 Jun 2007
TL;DR: This work presents the development and implementation of an acoustic sensor network mainly proposed for relative positioning of mobile robots and autonomous modules, by using only acoustic emissions as ranging mechanism.
Abstract: This work presents the development and implementation of an acoustic sensor network mainly proposed for relative positioning of mobile robots and autonomous modules. The system consists of several objects to be located, each one of them with an acoustic sensor node. Every node has the required technology in order to compute its position, by using only acoustic emissions as ranging mechanism; this reduces the complexity in the hardware to be implemented. Direct Sequence Code Division Multiple Access (DS-CDMA) techniques are used to allow simultaneous emission from several objects, so spatial relations among objects can be measured in a shorter time. Using the data collected by the proposed ranging mechanism, a relative positioning algorithm is computed with the aim of obtaining the positions among objects.
2 citations
01 Oct 2007
TL;DR: The obtained results show that a sub-centimeter precision and accuracy can be obtained considering a centimeter error magnitude in the distance measurements with the proposed ranging mechanism.
Abstract: In this work, the performance of an acoustic relative positioning system is studied, by a Monte-Carlo analysis, with the aim of determining the obtained accuracy and precision. The system has been designed in order to be used in the relative positioning estimation of mobile objects which are not restricted to a particular environment and cannot depend on any external infrastructure. In the proposed system, the spatial relations among objects are computed by only using acoustic emissions with the aim of measuring the round-trip-time-of-flight of the acoustic signals emitted by every object. Then, using the data collected in the system, object positions are computed using the multidimensional scaling technique, and a closer solution is achieved by least-square algorithms. In this performance analysis, a Gaussian distribution of the errors has been considered. The obtained results show that a sub-centimeter precision and accuracy can be obtained considering a centimeter error magnitude in the distance measurements with the proposed ranging mechanism.
2 citations
04 Jun 2007
TL;DR: In this article, a prototype of an ultrasonic transducer based on electromechanical film (EMFi) is presented, which provides a wide bandwidth response, useful for robotic applications.
Abstract: This paper presents a prototype of an ultrasonic transducer based on electromechanical film (EMFi). This electromechanical film provides a wide bandwidth response, useful for robotic applications. Furthermore, its sensitivity is constant enough to allow echo-pulse measurement in the desired frequency range. The emission patterns are obtained for different configurations, verifying the correspondence between experimental data and theoretical piston-like model. Results suggest that the polymer can be suitably used as a broadband ultrasonic transducer, in order to improve performances in ultrasonic sensorial systems, where the emission encoding with binary sequences, and the used modulation schemes, require considerably large bandwidth.