Murviel-lès-Montpellier, France
Murviel-lès-Montpellier, France

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Wong W.-K.,Hong Kong Polytechnic University | Yang B.,Shandong University of Science and Technology | Liu C.,LIRMM | Poignet P.,LIRMM
IEEE/ASME Transactions on Mechatronics | Year: 2013

Recently, model-based visual-tracking techniques have been developed for measuring physiological motion in robot-assisted minimally invasive surgery. However, the tracking of living tissue surfaces in 3-D space is very challenging. Linear models are difficult to fit complex tissue dynamics, while current nonlinear models generally suffer from complex implementation and excessive computational burden. Instrument occlusion is another challenging issue which often causes tracking failure. In this study, we propose a novel deformable model suitable for real-time 3-D tissue tracking based on a quasi-spherical triangle. The model is parameterized by three vertices of the triangle with a curving parameter so that the warped surface can be computed efficiently using matrix operations. An efficient second-order minimization technique is employed to estimate model parameters, and the Jacobian matrix associated with the proposed model is derived. To alleviate the effects of illumination, a triangle-based illumination model is incorporated into the tracking scheme. A new motion prediction algorithm is developed by exploring the peak-valley characteristics of motion signals to handle the occlusion problem. The performance of the proposed method is validated using phantom heart data and in vivo videos acquired by the daVinci surgical robotic platform. © 1996-2012 IEEE.


Berry A.,French National Center for Scientific Research | Pogorelcnik R.,French National Center for Scientific Research | Simonet G.,LIRMM
Algorithms | Year: 2010

This paper is a review which presents and explains the decomposition of graphs by clique minimal separators. The pace is leisurely, we give many examples and figures. Easy algorithms are provided to implement this decomposition. The historical and theoretical background is given, as well as sketches of proofs of the structural results involved. © 2010 by the authors.


Bibuli M.,CNR Institute of Neuroscience | Caccia M.,National Research Council Italy | Lapierre L.,LIRMM | Bruzzone G.,National Research Council Italy
IEEE Robotics and Automation Magazine | Year: 2012

Virtual target-based path-following techniques are extended to execute the task of vehicle following in the case of unmanned surface vehicles (USVs). Indeed, vehicle following is reduced to the problem of tracking a virtual target moving at a desired range from a master vessel, while separating the spatial and temporal constraints, giving priority to the former one. The proposed approach is validated experimentally in a harbor area with the help of the prototype USVs ALANIS and Charlie, developed by Consiglio Nazionale delle Ricerche-Istituto di Studi sui Sistemi Intelligenti per lAutomazione (CNR-ISSIA). © 2012 IEEE.


Koriche F.,LIRMM | Zanuttini B.,University of Caen Lower Normandy
Artificial Intelligence | Year: 2010

Conditional preference networks (CP-nets) have recently emerged as a popular language capable of representing ordinal preference relations in a compact and structured manner. In this paper, we investigate the problem of learning CP-nets in the well-known model of exact identification with equivalence and membership queries. The goal is to identify a target preference ordering with a binary-valued CP-net by interacting with the user through a small number of queries. Each example supplied by the user or the learner is a preference statement on a pair of outcomes. In this model, we show that acyclic CP-nets are not learnable with equivalence queries alone, even if the examples are restricted to swaps for which dominance testing takes linear time. By contrast, acyclic CP-nets are what is called attribute-efficiently learnable when both equivalence queries and membership queries are available: we indeed provide a learning algorithm whose query complexity is linear in the description size of the target concept, but only logarithmic in the total number of attributes. Interestingly, similar properties are derived for tree-structured CP-nets in the presence of arbitrary examples. Our learning algorithms are shown to be quasi-optimal by deriving lower bounds on the VC-dimension of CP-nets. In a nutshell, our results reveal that active queries are required for efficiently learning CP-nets in large multi-attribute domains. © 2010 Elsevier B.V. All rights reserved.


Zhang Q.,Huazhong University of Science and Technology | Zhang Q.,Tokyo University of Agriculture and Technology | Lapierre L.,LIRMM | Xiang X.,Huazhong University of Science and Technology
IEEE Transactions on Industrial Informatics | Year: 2013

This paper addresses the problem of coordinated path tracking for networked nonholonomic mobile vehicles, while building and keeping a desired formation. The control laws proposed are categorized into two envelopes by integrating individual path tracking and global virtual structure approaches. One is steering individual vehicles to track virtual vehicles moving along predefined paths, generated by a formation reference vehicle (FRV) of a time-varying desired virtual structure. The other is ensuring paths to be well tracked in order to build a geometric formation, through the distributed feedback law for path parameters related to the virtual vehicles, such that the physical vehicles are on the desired placements of the formation structure. Within this framework, geometric path tracking is achieved via nonlinear control theory, where an approaching angle is injected as a heading guidance design. The distributed feedback law is analyzed under communication constraints using algebraic graph theory. It is formally shown that the path tracking error of each vehicle is reduced to zero, and vehicles in the networked team globally asymptotically converge to a desired formation with equal path parameters. Simulation results illustrate the effectiveness of the proposed control design. © 2005-2012 IEEE.


Kaci S.,LIRMM
Proceedings of the 25th International Florida Artificial Intelligence Research Society Conference, FLAIRS-25 | Year: 2012

Most of preference representation languages developed in the literature are based on comparative preference statements. The latter offer a simple and intuitive way for expressing preferences. They can be interpreted following different semantics. This paper presents a postulate-based analysis of the different semantics describing their behavior w.r.t. three criteria: coherence, syntax independence and inference. Copyright © 2012, Association for the Advancement of Artificial Intelligence. All rights reserved.


Preller A.,LIRMM
Electronic Proceedings in Theoretical Computer Science, EPTCS | Year: 2014

The paper relates two variants of semanticmodels for natural language, logical functionalmodels and compositional distributional vector space models, by transferring the logic and reasoning from the logical to the distributional models. The geometrical operations of quantum logic are reformulated as algebraic operations on vectors. A map from functional models to vector space models makes it possible to compare the meaning of sentences word by word. © Anne Preller.


Bo A.P.,LIRMM
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2011

In this paper, we explore the combined use of inertial sensors and the Kinect for applications on rehabilitation robotics and assistive devices. In view of the deficiencies of each individual system, a new method based on Kalman filtering was developed in order to perform online calibration of sensor errors automatically whenever measurements from Kinect are available. The method was evaluated on experiments involving healthy subjects performing multiple DOF tasks.


Chein M.,LIRMM | Mugnier M.-L.,LIRMM | Croitoru M.,LIRMM
Knowledge Engineering Review | Year: 2013

This paper presents a graph-based knowledge representation and reasoning language. This language benefits from an important syntactic operation, which is called a graph homomorphism. This operation is sound and complete with respect to logical deduction. Hence, it is possible to do logical reasoning without using the language of logic but only graphical, thus visual, notions. This paper presents the main knowledge constructs of this language, elementary graph-based reasoning mechanisms, as well as the graph homomorphism, which encompasses all these elementary transformations in one global step. We put our work in context by presenting a concrete semantic annotation application example. Copyright © Cambridge University Press 2013.


Richa R.,LIRMM | Bo A.P.L.,LIRMM | Poignet P.,LIRMM
Medical Image Analysis | Year: 2011

In the context of minimally invasive cardiac surgery, active vision-based motion compensation schemes have been proposed for mitigating problems related to physiological motion. However, robust and accurate visual tracking remains a difficult task. The purpose of this paper is to present a robust visual tracking method that estimates the 3D temporal and spatial deformation of the heart surface using stereo endoscopic images. The novelty is the combination of a visual tracking method based on a Thin-Plate Spline (TPS) model for representing the heart surface deformations with a temporal heart motion model based on a time-varying dual Fourier series for overcoming tracking disturbances or failures. The considerable improvements in tracking robustness facing specular reflections and occlusions are demonstrated through experiments using images of in vivo porcine and human beating hearts. © 2010 Elsevier B.V.

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