CNRS Systems and Information Sciences Lab LSIS

Marseille, France

CNRS Systems and Information Sciences Lab LSIS

Marseille, France
Time filter
Source Type

Auzias G.,Aix - Marseille University | Auzias G.,CNRS Systems and Information Sciences Lab LSIS | Brun L.,Aix - Marseille University | Deruelle C.,Aix - Marseille University | And 2 more authors.
NeuroImage | Year: 2015

Recent interest has been growing concerning points of maximum depth within folds, the sulcal pits, that can be used as reliable cortical landmarks. These remarkable points on the cortical surface are defined algorithmically as the outcome of an automatic extraction procedure. The influence of several crucial parameters of the reference technique (. Im et al., 2010) has not been evaluated extensively, and no optimization procedure has been proposed so far. Designing an appropriate optimization framework for these parameters is mandatory to guarantee the reproducibility of results across studies and to ensure the feasibility of sulcal pit extraction and analysis on large cohorts.In this work, we propose a framework specifically dedicated to the optimization of the parameters of the method. This optimization framework relies on new measures for better quantifying the reproducibility of the number of sulcal pits per region across individuals, in line with the assumptions of one-to-one correspondence of sulcal roots across individuals which is an explicit aspect of the sulcal roots model (. Régis et al., 2005). Our procedure benefits from a combination of improvements, including the use of a convenient sulcal depth estimation and is methodologically sound. Our experiments on two different groups of individuals, with a total of 137 subjects, show an increased reliability across subjects in deeper sulcal pits, as compared to the previous approach, and cover the entire cortical surface, including shallower and more variable folds that were not considered before. The effectiveness of our method ensures the feasibility of a systematic study of sulcal pits on large cohorts.On top of these methodological advances, we quantify the relationship between the reproducibility of the number of sulcal pits per region across individuals and their respective depth and demonstrate the relatively high reproducibility of several pits corresponding to shallower folds. Finally, we report new results regarding the local pit asymmetry, providing evidence that the algorithmic and conceptual approach defended here may contribute to better understanding of the key role of sulcal pits in neuroanatomy. © 2015 Elsevier Inc.

Bideault G.,CNRS Systems and Information Sciences Lab LSIS | Herault R.,CNRS Systems and Information Sciences Lab LSIS | Seifert L.,University of Rouen
Journal of Science and Medicine in Sport | Year: 2013

Objectives: In accordance with dynamical systems theory, which assumes that motor behaviour emerges from interacting constraints (task, organismic, environmental), this study explored the functional role of inter-individual variability in inter-limb coordination. Design: 63 front crawl swimmers with a range of characteristics (gender, performance level, specialty) performed seven intermittent graded speed bouts of 25. m in front crawl. Methods: Each bout was video-taped with a side-view camera from which speed, stroke rate, stroke length and index of arm coordination (IdC) were analysed for three cycles. Cluster analysis was used to classify the swimmers through speed and IdC values. Results: Cluster analysis and validation showed four profiles of IdC management expressing the swimmers' characteristics as cluster 1: mainly national distance male swimmers, cluster 2: mainly international male sprinters, cluster 3: distinguished by female characteristics, and cluster 4: swimmers with the lowest level of performance. Conclusions: These profiles generated different IdC-speed regression models, which (i) showed how the swimmers adapted their motor behaviour to overcome task constraints and (ii) supported the key idea that there is not a single ideal expert model to be imitated, but rather adapted behaviour emerging from individually encountered constraints. © 2012 Sports Medicine Australia.

Khlaief A.,CNRS Systems and Information Sciences Lab LSIS | Boussak M.,CNRS Systems and Information Sciences Lab LSIS | Chaari A.,Unite de Recherche en Commande
Electric Power Systems Research | Year: 2014

In this paper, model reference adaptive system (MRAS) technique has been used for speed estimation in sensorless speed control of interior permanent magnet synchronous motor (IPMSM) with space vector pulse width modulation (SVPWM). Most of the current researches studying the MRAS technique are based on non-saliency PMSM model and ignore the difference between d- and q-axes inductances. This paper studies a novel MRAS observer, considering the saliency of PMSM. However, this sensorless speed control shows great sensitivity to stator resistance and system noise, particularly, during low-speed operation. A novel stator resistance estimator is incorporated into the sensorless drive to compensate the effects of stator resistance variation. A stability-analysis method of this novel MRAS estimator is shown. Stable and efficient estimation of rotor speed at low region will be guaranteed by simultaneous identification of IPMSM. The stability of proposed stator resistance estimator is checked through Popov's hyperstability theorem. The proposed observer is experimentally tested using a 1.1-kW motor drive; stable operation at very low speeds under different loading conditions is demonstrated. The real time implementation concept on the digital signal processor (DSP) board of the VFOC design and SVPWM inverter technique are illustrated. Results show that the proposed MRAS technique can satisfactorily estimate the position and speed of PMSM with saliency. © 2013 Elsevier B.V. All rights reserved.

Khlaief A.,Unite de Recherche en Commande | Khlaief A.,CNRS Systems and Information Sciences Lab LSIS | Bendjedia M.,CNRS Systems and Information Sciences Lab LSIS | Boussak M.,CNRS Systems and Information Sciences Lab LSIS | Gossa M.,Unite de Recherche en Commande
IEEE Transactions on Power Electronics | Year: 2012

This paper aims to provide a high-performance sensorless control of interior permanent magnet synchronous motor (IPMSM) based on nonlinear position and speed observer. The proposed nonlinear observer is constructed using the flux linkage as new state variable without speed dependence. The nonlinear observer gives estimation of the rotor position using a trigonometric function and the speed estimation is obtained from estimated position using proportional-integral (PI) tracking controller. This observer is stable easy to implement and does not require a large computing time. At standstill, we used the voltage pulses method to detect the initial rotor position. Short voltage pulses are applied to the stator winding and the initial rotor position is estimated from the measured peak current. High-dynamic performance is obtained using the vector field-oriented control and the space vector pulsewidth modulation techniques. Experimental results with 1.1-kW IPMSM have validated the effectiveness of the proposed sensorless speed control using nonlinear observer. The experimental implementation is carried out on powerful dSpace DS1103 controller board based on the DSP TMS320F240. © 2006 IEEE.

Bendjedia M.,CNRS Systems and Information Sciences Lab LSIS | Ait-Amirat Y.,University of Franche Comte | Walther B.,Haute Ecole Arc Engineering | Berthon A.,University of Franche Comte
IEEE Transactions on Power Electronics | Year: 2012

In this paper, the experimental results of position control of the hybrid stepper motor without a mechanical sensor are exhibited. Use of the steady-state extended Kalman filter to estimate the mechanical variables of the motor is shown. With this method the computing time is reduced. The initial rotor position is estimated by the impulse voltage technique. For position control, a simple state feedback control that can compensate the load torque variations was designed. The robustness against the motor parameters variation was also studied. A field-oriented control strategy is chosen. It is known that the mechanical position is crucially important to achieve this strategy. Finally, favorable experimental results are shared. © 2011 IEEE.

Graton G.,CNRS Systems and Information Sciences Lab LSIS | Outbib R.,CNRS Systems and Information Sciences Lab LSIS
2009 European Control Conference, ECC 2009 | Year: 2015

This paper deals with a model-based approach to stabilize the engine speed around a defined value. The engine speed is modeled as a non-linear model containing explicitly the expression of the fuel conversion efficiency. Generally speaking, in literature, the modeling of this quantity obtained from experiments has two main expressions defined as polynomial or exponential forms. This paper focuses on the engine speed stabilization when the fuel conversion efficiency is modeled with the exponential form which is more realistic. This work proposes a new smooth stabilization law around a desired engine speed value. Simulation results are proposed to highlight the closed-loop control accuracy. © 2009 EUCA.

Ounnar F.,CNRS Systems and Information Sciences Lab LSIS | Pujo P.,CNRS Systems and Information Sciences Lab LSIS
Journal of Intelligent Manufacturing | Year: 2012

Faced with international competition, industrial production increasingly requires implementation conditions which, in some cases, lead to seek new techniques for workshop control. This is the casewhen it is asked to establish Just in Time management in a Job Shop having the characteristics of working with small series. A new approach for the organization of the 'control' function in such a context is presented here. This approach relies on the use of the holonic paradigm on an isoarchic architecture and on a decision-making capacity based on a multicriteria analysis. The various concepts of this approach are addressed first. Then, the multicriteria decision mechanisms that are used are detailed, as well as the implementation and instrumentation phases. The first results that were obtained are presented. © Springer Science+Business Media, LLC 2009.

Sebesta K.D.,Boston University | Boizot N.,CNRS Systems and Information Sciences Lab LSIS
IEEE Transactions on Industrial Electronics | Year: 2014

The authors demonstrate the practical application of the adaptive high-gain extended Kalman filter (EKF) (AEKF) onboard a quadcopter unmanned aerial vehicle (UAV). The AEKF presents several advantages in state estimation, as it combines good filtering properties with an increased sensitivity to large perturbations. It does this by varying the high-gain parameter according to a metric called innovation. Unlike many adaptive observers, the AEKF is mathematically proven to globally converge, a significant advantage over the traditional EKF when considering robust controls. The AEKF is implemented on the UAV's inertial navigation system (INS). Full INSs can have problems when sensors are noisy and limited, particularly in the case of highly dynamically unstable systems such as a quadcopter. Simulation and experimental data show that the AEKF is suitable for this INS. © 1982-2012 IEEE.

Micouin P.,CNRS Systems and Information Sciences Lab LSIS
Systems Engineering | Year: 2014

The purpose of this paper is to contribute to the definition of a Model Based Systems Engineering (MBSE) approach which would meet the objective laid out by INCOSE in its Systems Engineering Vision 2020. After briefly presenting the tools used and summarizing a state-of-the-art system design process, we show how it is possible to define property-based requirements (PBRs) as features of specification models and to apply the design process to this specification model in order to develop design models. Then, we show how it is possible to perform a simulation-based verification process of design models in order to detect and remove design errors, to substitute the initial requirements of the system with derived requirements gradually assigned to the subentities of the system, to perform a simulation-based validation process of specification models in order to detect and remove specification errors. Additionally, we show how we define safety PBRs to prevent the consequences of failure conditions and verify mitigation means, such as redundancy or dissimilarity, introduced in design models to meet these safety PBRs. Thus, we consider that our proposals improve MBSE current practices making them safer for the development of present and future systems. © 2013 Wiley Periodicals, Inc.

Mohapatra P.,IIT | Benyoucef L.,CNRS Systems and Information Sciences Lab LSIS | Tiwari M.K.,IIT
International Journal of Production Research | Year: 2013

Setup planning is one of the crucial exercises that affects process planning, scheduling and their integration. In a reconfigurable environment where more than one machine is available to process a part, setup planning assumes an important position which involves a complex optimisation problem facing several constraints. In this research machining features are sequenced and grouped into certain setup based on tool approach direction (TAD). Therefore considering the criteria such as machine utilisation, cost and makespan, near optimal solutions are selected to satisfy the requirements of the scheduling system. We have also addressed in this paper adaptive characteristics of process plan associated with setup, i.e. a cross machine setup planning to capture the different configuration of machines. Exploiting the stress of the immune system, a well known intelligent search technique known as artificial immune system (AIS) has been applied to solve two problems associated with the research issue discussed here. The proposed AIS based approach is demonstrated to resolve an example problem. It is found that the proposed approach is successfully applicable to machines having several configurations and accommodative to different setup requirements from a scheduling system where the frequent changes in machines are witnessed. By the way of combining the setup for alternative machines with process planning, we can demonstrate clearly a true relation of integration of functionalities of process planning and scheduling. © 2013 Taylor & Francis Group, LLC.

Loading CNRS Systems and Information Sciences Lab LSIS collaborators
Loading CNRS Systems and Information Sciences Lab LSIS collaborators