Robust 3D registration and tracking with RGBD sensors

This thesis investigates the utilisation of cheap RGBD sensors in rigid body tracking and 3D multiview registration for augmented and Virtual reality applications. RGBD sensors can be used as an affordable substitute for the more sophisticated, but expensive, conventional laser-based scanning and tracking solutions. Nevertheless, the low-cost sensing technology behind them has several drawbacks such as the limited range, significant noisiness and instability. To deal with these issues, an innovative adaptation of Kalman filtering scheme is first proposed to improve the precision, smoothness and robustness of raw RGBD outputs. It also extends the native capabilities of the sensor to capture further targets. The mathematical foundations of such an adaptation are explained in detail, and its corrective effect is validated with real tracking as well as 3D reconstruction experiments. A Graphics Processing Unit (GPU) implementation is also proposed with the different optimisation levels in order to ensure real-time responsiveness. After extensive experimentation with RGBD cameras, a significant difference in accuracy was noticed between the newer and ageing sensors. This decay could not be restored with conventional calibration. Thus, a novel method for worn RGBD sensors correction is also proposed. Another algorithm for background/foreground segmentation of RGBD images is contributed. The latter proceeds through background subtraction from colour and depth images separately, the resulting foreground regions are then fused for a more robust detection. The three previous contributions are used in a novel approach for multiview vehicle tracking for mixed reality needs. The determination of the position regarding the vehicle is achieved in two stages: the former is a sensor-wise robust filtering algorithm that is able to handle the uncertainties in the system and measurement models resulting in multiple position estimates; the latter algorithm aims at merging the independent estimates by using a set of optimal weighting coefficients. The outcome of fusion is used to determine vehicle’s orientation in the scene. Finally, a novel recursive filtering approach for sparse registration is proposed. Unlike ordinary state of the art alignment algorithms, the proposed method has four advantages that are not available altogether in any previous solution. It is able to deal with inherent noise contaminating sensory data; it is robust to uncertainties related to feature localisation; it combines the advantages of both L2 , L (infinity) norms for a higher performance and prevention of local minima; it also provides an estimated rigid body transformation along with its error covariance. This 3D registration scheme is validated in various challenging scenarios with both synthetic and real RGBD data

Estimation de la bande passante disponible en sans fil : train de paires de paquets

This article looks at traditional method to estimate bandwidth in wired network and their application to wireless network

Evaluation des performances de SloPS : technique d'estimation de la bande passante dans les réseaux sans fil 802.11b

Over the past few years several algorithms have been created to actively measure the end-to-end available bandwidth of a network path (TOPP, SLoPS, Spurce, VPS ). These algorithms are dedicated to wired Ethernet network; however the bandwidth estimation in wireless network field remains a challenge. In the present work we evaluate the performance of Self-Loading Periodic Stream (SLoPS) method to estimate the available bandwidth in the IEEE 802.11b wireless network. By using different probe packet sizes and different Cross-Traffics, we show that the available bandwidth measurements are affected by the varying Cross-Traffic in both Ethernet and wireless IEEE 802.11b network. The variation of probe packet size affects the available bandwidth measurements only in the wireless network and not in Ethernet network case. Also SLoPS technique provides less accurate measurements in the IEEE 802.11b wireless network. The simulation is built in NS-2. The results are analysed by MatLab software

Expérimentations sur la plateforme PAVIN du protocole de communication inter véhicule (CIVIC)

International audienceThis paper describes a cooperative MANET protocol dedicated to intelligent transportation systems and its new experiment results in mobile scenarios. The protocol is named CIVIC (Communication Inter Véhicule Intelligente et Coopérative). It is an auto-configuration inter-vehicle communication protocol, which supports ad-hoc and infrastructure networks, contains reactive and proactive routing components, and adapts different wireless standards. It is also a location-based and context-aware protocol reacting to vehicle status, road traffic, and geographic environment. The CIVIC protocol has been implemented on the LiveNode sensor developed by our laboratory. The new experiments of CIVIC protocol are carried out on PAVIN platform (Plate-forme d'Auvergne pour Véhicules Intelligents) supported by the TIMS (Technologies de l'Information de la Mobilité et de la Sûreté) research federation. These experiments demonstrate the feasibility and reliability of CIVIC in mobility scenarios. In addition, an application project named MobiPlus will be introduced

Caractéristiques et conception de réseaux sans fil intelligents

The contention-based multi access schemes of wireless networks impose difficulties in achieving predictable service quality, especially in multi-hop deployments. In order to offer advanced network services such as flow admission control, the residual capacity of the wireless links should be accurately estimated. In this report, we discuss two proposals as solutions to this problem. The first proposal developed by SABU is a passive residual capacity estimation algorithm that can be implemented in all Wi-Fi (802.11b/g) based platforms. With this algorithm it is possible to obtain more efficient and reliable admission control and routing decisions in wireless access and mesh networks. The second proposal developed by UBP is an intrusive method, more tuned towards WSNs and MANETs, which require active resource estimation methods. Another improvement by SABU presented here is a novel and practical load-based association scheme for WiFi access networks, so that available bandwidth resources are used optimally, in a more balanced and fair manner

Evaluation des performances de SLOPS : technique d'estimation de la bande passante dans les réseaux sans fil IEEE 802.11b

Extrait de documentOver the past few years, to actively measure the end-to-end available bandwidth of a network path several algorithms have been created (TOPP, SLoPS, Spurce, VPS ldots). These algorithms are dedicated to wired Ethernet network; however the bandwidth estimation in wireless network field remains a challenge. In the present work we evaluate the performance of Self-Loading Periodic Stream (SLoPS) method to estimate the available bandwidth in the IEEE 802.11b wireless network. By using different probe packet sizes and different Cross-Traffics, we show that the available bandwidth measurements are affected by the varying Cross-Traffic in both Ethernet and wireless IEEE 802.11b network. The variation of probe packet size affects only the available bandwidth measurements in the wireless network and not in Ethernet network case. Also SLoPS technique provides less accurate measurements in the IEEE 802.11b wireless network. The simulation is built in NS-2. The results are analyzed by MatLab softwar

Synthesis and photoluminescence properties of nanostructured mullite/α- Al2O3Al_2O_3

Phase transformation of α-Al2O3 to mullite was observed by correlated X-ray diffraction and low-temperature (7 K) time- and energy-resolved photoluminescence methods. The aluminosilicate solids with different Si:Al ratios were prepared after thermal treatment (1400 °C) of ultraporous alumina (UPA) monoliths impregnated with vapour of silica precursors at room temperature. The initial dispersion of Si is homogeneous on a size-scale of 5 nm raw UPA fibres, which grow in size during the thermal treatment stage up to ∼50–100 nm. Three phases were resolved in the considered SiO2/Al2O3 system: silica, α-Al2O3 and their interaction product 2:1 mullite (2Al2O3:SiO2). The 2:1 mullite mass increases and α-Al2O3 mass decreases with an increase of the initial silica content. At the SiO2 content in the initial system above 20 mol.%, the phase transformation to 2:1 mullite is complete and no α-Al2O3 was observed. No mullite phases with either lower or higher Si content were observed. The fundamental absorption onset energy 7.55 eV of 2:1 mullite was measured

Un estimateur de bande passante non invasif pour les MANET

Thanks to the tremendous advances in wireless network and mobile ad hoc network new applications are now possible: inter vehicle communication, telemedicine etc. However many problems such as quality of service and security are still unsolved. Our work is focused on the implementation of a MANET bandwidth estimator enables to improve routing protocol and by the way the quality of service. In fact, two types of techniques exist to estimate network bandwidth: invasive and non invasive. In this paper, we present a non-invasive technique based on Round Trip Time or One-Way Trip Time. The performance of our estimator will be presented and discussed

Résultats des simulations et des tests de performance en laboratoire ( projet Netadded )

This document provides the performance analysis of the developed intelligent wireless mesh networking protocols according to the definition of tests given in AD02. According to the Technical Annex of Net-added project, the objective of WP 4.3.2 was defining, developing and evaluating new and more flexible algorithms dedicated to wireless mesh network operation. Both SABU and UBP investigated methods to estimate the residual bandwidth in wireless mesh networks. The residual bandwidth is defined as the difference between the network link/path capacity and the current throughput of the system. The proposed SABU algorithm is a passive estimation algorithm, which listens to the channel and uses analytical techniques to calculate the residual channel bandwidth. On the contrary, the proposed UBP method is an active algorithm which injects dummy packets into the channel to saturate the channel and thus, determine the channel capacity accordingly.The performance evaluation of passive algorithm is performed by realistic simulations on OPNET network simulator. The active algorithm is first verified on NS-2 network simulator, and later, it is implemented on LiveNode hardware platform developed by CEMA and UBP under NETADDED project. The LiveNode platform was especially developed for agricultural and environment monitoring applications. Both algorithms were tested with extensive numerical simulation experiments and they are shown to have much better accuracy than those previously proposed in the literature. The performance gains with intelligent networking applications using residual bandwidth as their decision metric are also demonstrated to be significant

Métrique et définition de tests ( projet Netadded)

This document discusses the metrics and tests performed for evaluating the performance of wireless mesh networks. The solutions of two important research challenges in wireless mesh networks were analyzed in these tests. The first of the research challenge addressed was the estimation of residual bandwidth in wireless mesh networks. The residual bandwidth is defined as the difference between the network link/path capacity and the current throughput of the system. The residual bandwidth identifies the additional user demand that can still be satisfied under current conditions. If the residual bandwidth is accurately estimated, it can be used to improve the quality of service perceived by the users. Two different residual bandwidth estimation algorithms were developed in NETADDED project. The current report gives the test and simulation scenarios considered in the performance evaluation of these algorithms. The second challenge was to develop hardware for agricultural and environmental monitoring system based on wireless mesh networks. This hardware should be modular and satisfy the requirements of agricultural users. The hardware combines sensors and different communication interfaces such as Zigbee and 802.11 in order to both provide energy-efficient and long-term communications. This report gives details on the configurations of real network implementations and test scenarios used to evaluate the performance of the developed hardware