An Iterative Co-Saliency Framework for RGBD Images

As a newly emerging and significant topic in computer vision community, co-saliency detection aims at discovering the common salient objects in multiple related images. The existing methods often generate the co-saliency map through a direct forward pipeline which is based on the designed cues or initialization, but lack the refinement-cycle scheme. Moreover, they mainly focus on RGB image and ignore the depth information for RGBD images. In this paper, we propose an iterative RGBD co-saliency framework, which utilizes the existing single saliency maps as the initialization, and generates the final RGBD cosaliency map by using a refinement-cycle model. Three schemes are employed in the proposed RGBD co-saliency framework, which include the addition scheme, deletion scheme, and iteration scheme. The addition scheme is used to highlight the salient regions based on intra-image depth propagation and saliency propagation, while the deletion scheme filters the saliency regions and removes the non-common salient regions based on interimage constraint. The iteration scheme is proposed to obtain more homogeneous and consistent co-saliency map. Furthermore, a novel descriptor, named depth shape prior, is proposed in the addition scheme to introduce the depth information to enhance identification of co-salient objects. The proposed method can effectively exploit any existing 2D saliency model to work well in RGBD co-saliency scenarios. The experiments on two RGBD cosaliency datasets demonstrate the effectiveness of our proposed framework.Comment: 13 pages, 13 figures, Accepted by IEEE Transactions on Cybernetics 2017. Project URL: https://rmcong.github.io/proj_RGBD_cosal_tcyb.htm

Beam Training and Tracking with Limited Sampling Sets: Exploiting Environment Priors

Beam training and tracking (BTT) are key technologies for millimeter wave communications. However, since the effectiveness of BTT methods heavily depends on wireless environments, complexity and randomness of practical environments severely limit the application scope of many BTT algorithms and even invalidate them. To tackle this issue, from the perspective of stochastic process (SP), in this paper we propose to model beam directions as a SP and address the problem of BTT via process inference. The benefit of the SP design methodology is that environment priors and uncertainties can be naturally taken into account (e.g., to encode them into SP distribution) to improve prediction efficiencies (e.g., accuracy and robustness). We take the Gaussian process (GP) as an example to elaborate on the design methodology and propose novel learning methods to optimize the prediction models. In particular, beam training subset is optimized based on derived posterior distribution. The GP-based SP methodology enjoys two advantages. First, good performance can be achieved even for small data, which is very appealing in dynamic communication scenarios. Second, in contrast to most BTT algorithms that only predict a single beam, our algorithms output an optimizable beam subset, which enables a flexible tradeoff between training overhead and desired performance. Simulation results show the superiority of our approach

CSI-Free Geometric Symbol Detection via Semi-supervised Learning and Ensemble Learning

Symbol detection (SD) plays an important role in a digital communication system. However, most SD algorithms require channel state information (CSI), which is often difficult to estimate accurately. As a consequence, it is challenging for these SD algorithms to approach the performance of the maximum likelihood detection (MLD) algorithm. To address this issue, we employ both semi-supervised learning and ensemble learning to design a flexible parallelizable approach in this paper. First, we prove theoretically that the proposed algorithms can arbitrarily approach the performance of the MLD algorithm with perfect CSI. Second, to enable parallel implementation and also enhance design flexibility, we further propose a parallelizable approach for multi-output systems. Finally, comprehensive simulation results are provided to demonstrate the effectiveness and superiority of the designed algorithms. In particular, the proposed algorithms approach the performance of the MLD algorithm with perfect CSI, and outperform it when the CSI is imperfect. Interestingly, a detector constructed with received signals from only two receiving antennas (less than the size of the whole receiving antenna array) can also provide good detection performance

Modellierung, Simulation und Entwurf biomimetischer Roboter basierend auf apedaler undulatorischer Lokomotion

Abstract zur Dissertation Autor: Jianjun Huang Titel: Modellierung, Simulation und Entwurf biomimetischer Roboter basierend auf apedaler undulatorischer Lokomotion _____________________________________________________________________________________________ This dissertation presented is contributing to the current research in the interdisciplinary field of Biomechatronics. In order to develop a technical locomotion system on the basis of rigid multi body system inspired by biological systems (earthworm), the concepts of the undulatory locomotion has been described and implemented technically into the prototypes. Compared to other natural motion patterns, e.g. legged walking, the biomimetic robot based on the peristaltic principle is of great interest to the engineer because of (1) the ability of miniaturization of compliant structures; (2) the ability to move on various terrain; (3) the ability to simplify the movement apparatus. According to the research of MILLER and STEIGENBERGER two aspect of worm like motion are defined: (1) unsymmetrical friction and (2) periodic internal deformations and its interactions with the environment. For this reason, in the theoretically mechanical part of this dissertation, these specific principles have been studied with analytical and computer aided methods. Control algorithm (gaits) for robots with worm like locomotion that are based on more than two DOF spring mass models and are realizing a forward velocity are proposed. The computer simulation of the dynamic behavior of these models and the prototypes have been achieved with the multi body dynamics package ALASKA. In most cases, the experimental evaluation of the numerical results have proven equality between the theory and the experiment. For the technical testing of the developed principle of locomotion and control algorithm two prototypes, which use the electromechanical motor and imbalance system have been designed and tested to produce an internal periodical excitation. The third prototype uses a piezo actuator as a motor and a flexible mechanisms as transmission element. Potential applications of robots with worm like motions are found in all fields of micro and nanotechniques. For these constraint dimensions locomotion systems that have classical motion principles, e.g. the wheeled mobile systems or legged systems, are not suitable for future potential application environments characterized by special terrains and tight space. Apedale peristaltic principle of locomotion may play an important role in the development of new apparatuses in micro technology. The development of applications in minimally invasive surgery has been encouraged by many national and international research institutes. The theoretical and experimental investigation have shown that future research is necessary.Die vorgelegte Arbeit soll einen Beitrag zur Forschung im interdisziplinären Gebiet der Biomechatronik leisten. Es wurde ein Konzept zur Umsetzung einer undulatorischen Lokomotion zur Entwicklung technischer Bewegungssysteme nach biologischem Vorbild (Regenwurm), basierend auf Starrkörpersystemen mathematisch beschrieben und in Prototypen technisch umgesetzt. Gegenüber anderen Bewegungsformen in der Natur, wie z.B. dem Laufen mit Beinen liegt das ingenieurtechnische Interesse für biomimetische Roboter nach dem Peristaltik-Prinzip des Regenwurmes in (1) der Miniaturisierbarkeit der nachgiebigen Strukturen; (2) der Bewegungsmöglichkeit auf vielgestaltigem Untergrund; (3) der Einfachheit des Bewegungsapparates. Ausgehend von den Arbeiten von MILLER und STEIGENBERGER wurden die zwei Aspekte (1) nichtsymmetrische Reibung und (2) periodische interne Deformationen und ihre Auskopplung über Wechselwirkungen mit der Umwelt als wesentlich für eine wurmartige Fortbewegung definiert. Im mathematisch-mechanischen Teil der Arbeit wurden deshalb speziell diese Phänomene mit analytischen und computergestützten Methoden untersucht. Es sind Ansteueralgorithmen (gaits) für wurmartige Roboter, basierend auf Feder-Masse-Modellen mit dem Freiheitsgrad grösser zwei vorgeschlagen worden, die eine maximale Vortriebsgeschwindigkeit realisieren. Die Computersimulation des dynamischen Verhaltens dieser Modelle bzw. der entwickelten Prototypen erfolgte mit dem System ALASKA. Die experimentelle Evaluierung der numerischen Ergebnisse ergab in vielen Fällen gute qualitative und quantitative Übereinstimmung zwischen Theorie und Experiment. Zur praktischen Erprobung der gefundenen Bewegungsprinzipien und der Steuer-algorithmen wurden zwei Prototypen mit elektromechanischem Antrieb und Unwuchtsystem zur Erzeugung der internen periodischen Erregung konstruiert und getestet. Ein dritter miniaturisierter Prototyp arbeitet mit einem Piezoaktuator als Antrieb und einem nachgiebigen Mechanismus als Übertragungselement. Potentielle Einsatzgebiete für wurmartige Roboter sind vor allem im Bereich der Mikro- und Nanotechnik zu erwarten. In diesen Dimensionen sind Bewegungssysteme in ihrer klassischen Form, wie z.B. als "wheeled locomotion systems" und "legged locomotion systems", nicht geeignet für zukünftige potentielle Einsatzumgebungen, die u.a. durch das spezielle Terrain oder eingeschränkte Raumbedingungen gekennzeichnet sind. Apedale peristaltische Bewegungsprinzipien können bei der Entwicklung neuartiger Bewegungssysteme im Mikrobereich eine grosse Rolle spielen. Erste Entwicklungen für die minimal-invasive Chirurgie werden von mehreren Forschergruppen national und international vorangetrieben. Die theoretischen und experimentellen Untersuchungen haben deutlich gemacht, dass weitere Forschungen notwendig sind