Centro Universitario Of La Defensa Cud

Zaragoza, Spain

Centro Universitario Of La Defensa Cud

Zaragoza, Spain
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Nunez J.M.,Centro Universitario Of La Defensa Cud | Araujo M.G.,University of Vigo | Garcia-Tunon I.,University of Vigo
Sensors (Switzerland) | Year: 2017

A telemetry system for real-time monitoring of the motions, position, speed and course of a ship at sea is presented in this work. The system, conceived as a subsystem of a radar cross-section measurement unit, could also be used in other applications as ships dynamics characterization, on-board cranes, antenna stabilizers, etc. This system was designed to be stand-alone, reliable, easy to deploy, low-cost and free of requirements related to stabilization procedures. In order to achieve such a unique combination of functionalities, we have developed a telemetry system based on redundant inertial and magnetic sensors and GPS (Global Positioning System) measurements. It provides a proper data storage and also has real-time radio data transmission capabilities to an on-shore station. The output of the system can be used either for on-line or off-line processing. Additionally, the system uses dual technologies and COTS (Commercial Off-The-Shelf) components. Motion-positioning measurements and radio data link tests were successfully carried out in several ships of the Spanish Navy, proving the compliance with the design targets and validating our telemetry system. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.


Altabas J.A.,Aragon Institute of Engineering Research | Izquierdo D.,Aragon Institute of Engineering Research | Izquierdo D.,Centro Universitario Of La Defensa Cud | Lazaro J.A.,Polytechnic University of Catalonia | And 3 more authors.
Optics Express | Year: 2016

1Gbps full-duplex optical links for 6.25GHz ultra dense WDM frequency slots are demonstrated and optimized for cost-effective metroaccess networks. The OLT-ONU downlinks are based on 1Gbps Nyquist- DPSK using MZM and single-detector heterodyne reception obtaining a sensitivity of -52dBm. The ONU-OLT uplinks are based on 1Gbps NRZDPSK by directly phase modulated DFB and also single-detector heterodyne reception obtaining same sensitivity of -52dBm. The power budget of full-duplex link is 43dB. These proposed links can provide service to 16 (32) users at each 100 (200) GHz WDM channel. © 2016 Optical Society of America.


Priolo A.,Third University of Rome | Gasparri A.,Third University of Rome | Montijano E.,Centro Universitario Of La Defensa Cud | Sagues C.,University of Zaragoza
Proceedings of the American Control Conference | Year: 2013

In this work we propose a decentralized algorithm for balancing a strongly connected weighted digraph. This algorithm relies on the decentralized estimation of the left eigenvector associated to the zero structural eigenvalue of the Laplacian matrix. The estimation is performed through the distributed computation of the powers of the Laplacian matrix itself. This information can be locally used by each agent to modify the weights of its incoming edges so that their sum is equal to the sum of the weights outgoing this agent, i.e., the weighted digraph is balanced. Simulation results are proposed to corroborate the theoretical results. © 2013 AACC American Automatic Control Council.


Montijano E.,Centro Universitario Of La Defensa Cud | Montijano J.I.,University of Zaragoza | Sagues C.,University of Zaragoza
IEEE Transactions on Signal Processing | Year: 2013

In this paper we analyze the use of Chebyshev polynomials in distributed consensus applications. It is well known that the use of polynomials speeds up the convergence to the consensus in a significant way. However, existing solutions only work for low degree polynomials and require the topology of the network to be fixed and known. We propose a distributed algorithm based on the second order difference equation that describes the Chebyshev polynomials of first kind. The contributions of our algorithm are three: (i) Since the evaluation of Chebyshev polynomials is stable, there is no limitation in the degree of the polynomial. (ii) Instead of the knowledge of the whole network topology, it only requires a partial knowledge or an approximation to it. (iii) It can be applied to time varying topologies. In the paper we characterize the main properties of the algorithm for both fixed and time-varying communication topologies. Theoretical results, as well as experiments with synthetic data, show the benefits of using our algorithm compared to existing methods.© 2012 IEEE.


Priolo A.,Third University of Rome | Gasparri A.,Third University of Rome | Montijano E.,Centro Universitario Of La Defensa Cud | Montijano E.,University of Zaragoza | Sagues C.,University of Zaragoza
Automatica | Year: 2014

In this work we propose a distributed algorithm to solve the discrete-time average consensus problem on strongly connected weighted digraphs (SCWDs). The key idea is to couple the computation of the average with the estimation of the left eigenvector associated with the zero eigenvalue of the Laplacian matrix according to the protocol described in Qu et al. (2012). The major contribution is the removal of the requirement of the knowledge of the out-neighborhood of an agent, thus paving the way for a simple implementation based on a pure broadcast-based communication scheme. © 2014 Elsevier Ltd. All rights reserved.


Montijano E.,Centro Universitario Of La Defensa Cud | Zhou D.,Boston University | Schwager M.,Boston University | Sagues C.,University of Zaragoza
Proceedings of the American Control Conference | Year: 2014

This paper presents a decentralized controller to drive a team of agents to reach a desired formation in the absence of a global reference frame. Each agent is able to measure its relative position and orientation with respect to its neighbors. The different orientations imply that the relative positions between pairs of agents are sensed differently for each agent. In order to reach the desired configuration, the agents use two simultaneous consensus controllers, one to control their relative orientations, and another for their relative positions. The convergence to the desired configuration is shown by comparing the system with time-varying orientations with the equivalent approach with fixed rotations, showing that their difference vanishes as time goes to infinity. While the analysis in the paper is performed in a 2-dimensional space with orientations belonging to SO(2), our approach can be extended to handle 3 dimensions and orientations in SO(3). Simulation results, as well as hardware experiments with two quadrotor UAVs, corroborate the theoretical findings of the paper. © 2014 American Automatic Control Council.


Montijano E.,Centro Universitario Of La Defensa Cud | Montijano J.I.,University of Zaragoza | Sagues C.,University of Zaragoza | Martinez S.,University of California at San Diego
Automatica | Year: 2014

This paper deals with the problem of average consensus of a set of time-varying reference signals in a distributed manner. We propose a new class of discrete time algorithms that are able to track the average of the signals with an arbitrarily small steady-state error and with robustness to initialization errors. We provide bounds on the maximum step size allowed to ensure convergence to the consensus with error below the desired one. In addition, for certain classes of reference inputs, the proposed algorithms allow arbitrarily large step size, an important issue in real networks, where there are constraints in the communication rate between the nodes. The robustness to initialization errors is achieved by introducing a time-varying sequence of damping factors that mitigates past errors. Convergence properties are shown by the decomposition of the algorithms into sequences of static consensus processes. Finally, simulation results corroborate the theoretical contributions of the paper. © 2014 Elsevier Ltd. All rights reserved.


Montijano E.,Centro Universitario Of La Defensa Cud | Priolo A.,Third University of Rome | Gasparri A.,Third University of Rome | Sagues C.,University of Zaragoza
Proceedings of the IEEE Conference on Decision and Control | Year: 2013

In this paper we address the entrapment problem for a multi-robot system under the assumption of uncertainty in the knowledge of the target position. More precisely, we assume each robot models its knowledge of the location of the target through a Gaussian distribution, that is, with an expected value of the target location and the related covariance matrix. Motivated by this probabilistic modeling of the knowledge of the target location, we propose a novel algorithm where elliptical orbits are considered for the entrapment rather than circular ones, as in a classical entrapment formulation. A theoretical analysis of the entrapment algorithm properties is provided. In particular, we show this formulation to be a generalization of the classical entrapment scenarios. Simulation results are proposed to corroborate the theoretical analysis. © 2013 IEEE.


Montijano E.,Centro Universitario Of La Defensa Cud | Cristofalo E.,Boston University | Schwager M.,Stanford University | Sagues C.,University of Zaragoza
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2016

In this paper we consider the problem of controlling a team of non-holonomic robots to reach a desired formation. The formation is described in terms of the desired relative positions and orientations the robots need to keep with respect to each other, and it is assumed that the robots do not have a common shared reference frame. In other words, the robots can use only on-board sensing to achieve the formation. We first consider a holonomic framework, using a well known distance-based approach to reach a formation for the positions. We then include a control law for the orientations. We further discuss the problem of mirror configurations that appear when different desired relative orientations can satisfy the same distance-based constraints through different formations. Exploiting the concept of chirality, we present a relabeling strategy to reassign the robots' roles to reach the desired pattern when a mirror configuration occurs. The distance-based holonomic control is then transformed to cope with the non-holonomic constraints using a piecewise-smooth function. Simulation results, as well as hardware experiments with five m3pi robots demonstrate the applicability of our approach. © 2016 IEEE.


Tardioli D.,Centro Universitario Of La Defensa Cud | Montijano E.,Centro Universitario Of La Defensa Cud | Mosteo A.R.,Centro Universitario Of La Defensa Cud
IEEE International Conference on Intelligent Robots and Systems | Year: 2015

The performance of any cooperative task that involves two or more robots will be determined by their capacity to recognize common information of the environment. Vision sensors are very effective for this particular goal, but the cost of transmitting the visual information represents a real issue, even more if communication must be performed in narrow bandwidth networks and/or over a multi-hop path. Visual vocabularies provide a dimensionality reduction that has been effectively used in computer vision to reduce the computational load of performing searches in large volumes of data. In this paper we propose to exploit the same technique to decrease the volume of information that is exchanged in the network. This way, robots do not need to send the full descriptors associated to the features they observe, but only the word indices of the corresponding features in the vocabulary. Experiments with a wide variety of vocabularies are used to evaluate the quality of the association given by the algorithm. Finally, real experiments in a wireless network with a limited bandwidth are reported, showing the advantages of the proposed method compared to the communication of full images or feature descriptors. © 2015 IEEE.

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