Browsing by Author "Alonso, Asier"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Acoustic emission characterisation of two pre-cracked specimens(British Institute of Non-Destructive Testing, 2022) Gálvez, Antonio; Galar, Diego; Alonso, Asier; Errasti-Alcalá, Borja; Bienvenido, Ismael; Ortego, Patxi; Juuso, Esko; Tecnalia Research & InnovationThis article contains the experiments carried-out to study the capabilities of Acoustic Emissions (AE) in a Ship To Shore (STS) crane. This solution studies the implementation of Structural Health Monitoring (SHM) in an STS crane based on acoustic emissions (AE) technique for detecting cracks and assessing their growth in steel elements subjected to fatigue. The first experiment is performed using a compact tension specimen (CT) made of steel S355 whose dimensions are 125x120x50 mm and its cracks and dimensions are defined based on ASTM and ISO standards. The CT is monitored using AE sensors, and then, the features are extracted from the raw data and used to train, test and validate an unsupervised model. The crack detection model obtains a remarkable accuracy; crack detection at sizing of 3 mm length. As the CT dimensions are small, it is difficult to evaluate the attenuation of AE signals, which is completely necessary for monitoring STS cranes. Therefore, a second experiment is performed using a panel made of steel S355, whose dimensions are 2120x200x8 mm; the panel contains a crack of 50x3 mm. This experiment is performed to analyse the AE signals that come from cracks; specifically, to assess signals attenuation, how the attenuation affects cracks detection in the panel, and features evolution while crack propagation. This is led by monitoring the crack growth with crack detection gauges and installing the AE sensors at different distances of the crack. The assessment is used to develop an unsupervised model to detect cracks and an algorithm for localizing them.Item A direct sampling digital receiver for multiple GNSS signals(2008-03-20) Alonso, Asier; Perre, Jean Michel; Arizaga, Iñigo; FACTORY; QuantumThe recent proliferation of different GNSS signals (GPS L2 & L5, Galileo, Glonass, etc.) offers new possibilities for designers, multiple constellations broadcasting interoperable open signals will result in improved geometry, increasing end user accuracy everywhere and improving service availability in environments where satellite visibility is often obscured. Receivers have to be adapted to be able to cope with different signals, but this may imply an increase of hardware elements. Using a SDR approach, the aim of this paper is to reduce the number of hardware components exploring the feasibility of a direct digitization wearable device, which can deal with different standards, concretely (GPS L1, L2 civilian signal & L5, and Galileo E5a, E5b, E6 & L1). A special digital signal processing had to be designed in order to employ a single front end for all the different frequency bands. Position awareness is fundamental for many pervasive computing applications. In an ubiquitous paradigm, mobile devices should know their location without the user telling them specifically and their behaviour may depend on where they are. Traditionally there have been different positioning techniques, concretely Global Navigation Satellite Systems (GNSS) systems, whose main representative is GPS L1, have been employed since more than twenty years. In recent years, the development of alternative GNSS signals, has open the way for advanced applications. The main advantage of this proliferation of standards, is the possibility of combining their capabilities, in order to obtain maximum coverage, creating a universal GNSS receiver. But there is an obvious inconvenient: such a device would require twice or three times more hardware than current GPS receivers, increasing considerably its size and reducing its flexibility. Software Defined Radio (SDR) is a technology which ideally aims to suppress all hardware elements in a radio receiver and replace them with software configurable elements such as FPGA's or DSP's. Due to GNSS low power signals, this is not feasible without RF amplification & filtering, and traditionally, an analog front-end has been used to move the signal from RF frequencies to one or two intermediate frequencies. The development of faster converters (up to 1Gsps) as well as high quality RF filters makes possible to suppress part of the analog system and bring the digital interface nearer to the aerial. The aim of this paper, is to present a Galileo-GPS receiver from the SDR point of view. The main problem of a conventional SDR receiver is that it requires an analog front-end and as the GNSS systems work in different bands, at least two RF channels are required for high accuracy receivers. In order to avoid this duplication of hardware a direct digitization approach will be used. The main idea is to choice an appropriate sampling frequency and signal processing algorithm, which will reduce the required input bandwidth to 50 MHz, so a single wideband front end will be required in order to condition GNSS signals. An specific digital signal processing is needed in order to separate and correctly acquire each different signal. In order to test the feasibility of such a receiver, different noisy signals will be used, also outband and inband jammering signals will be employed to test the tracking ability of the device in real conditions.Item M:VIA, smarter vehicles and roads by using new generation its concepts and IMS capabilities(2009) García, Laura; Pinart, Carolina; Lequerica, Iván; Alonso, Asier; Rodríguez, Jesús J.; González, Juan M.; Quesada, David; FACTORYThe m:Vía system combines advanced concepts of Intelligent Transport Systems and Services (ITS) with the capabilities of the IP Multimedia Subsystem (IMS) to offer enhanced communications and services in vehicular environments and to hide the complexity of offering value-added services. In the vehicle, the m:Vía communication unit manages connectivity, and several user services have been implemented in the m:Vía application unit. Services make use of IMS capabilities, through an IMS client embedded in the application unit. On the road, Road Side Units offer information and extra connectivity to Internet. Results showing the advantages of the proposed system are expected from ongoing field tests.