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International audience; Developing electronic medical devices is challenging. Simulations or in vivo experiments are not sufficient to obtain pertinent comparisons between potential design options. This paper presents a new artificial tool allowing objective comparisons between electronic device topologies. The main idea is to build a tool which is sensitive to targeted biological parameters only. These tools are generally called phantoms. The phantom presented in this paper is dedicated to IntraOcular Pressure (IOP) Measurement devices used in glaucoma diagnosis and treatment. It is called Biomechanical Eye Emulator (BEE). The BEE emulates the main biomechanical parameters influencing the IOP measurements. Because it is not sensitive to the living context, the BEE is the most efficient tool to investigate the best sensor design. BEE specifications are defined to be as close as possible to chosen models (humans or animals). Its efficiency is shown with a case study on rabbits. The results clearly demonstrate the BEE phantoms efficacy in providing objective assessment metrics during the sensor design process.

International audience; In the context of high performance systems and critical applications, the general objective of the SACSO project is to design Self-Adaptive Systems, which are able of monitoring the surrounding environment and adapt themselves to different scenarios and requirements. In other words, a Self-Adaptive System must be able to provide the required high performances regardless the application mode and despite the changing environmental conditions. The fundamental concept of self-adaptation by itself is not completely new: self-calibration techniques applied after manufacturing have been developed to deal with the many sources of technological variations and self-compensation techniques applied during the lifetime of the system have been developed to deal with the ageing effects. In this project, we address two non-classical cases of self-adaptability: self-adaptation to the application and self-adaptation to the environment.In order to develop a generic methodology, the project is based on three demonstrators covering wide part of possible contexts. One the demonstrators, a sensor for Intra-Ocular Pressure measurement, illustrates both active front-end and medical contexts. For all these case studies, we highlight the different bottlenecks to achieve self-adaptation system and we define generic strategy suitable in all context.

International audience; This paper presents a study of dependability in the specific case of microstimulator implanted in the human body. In spite of the critical nature of this kind of application, there is no general study or standard of dependability for it. Based on real circuits developed in the DEMAR project, this paper illustrates the general attributes of dependability applied to medical implants. This kind of systems consists in generating an electrical signal (Functional Electrical Stimulation) into a nerve or a muscle to activate it and restore some lost abilities for para or tetraplegia. In this context, this paper highlights some key points of such system to enhance the general dependability.

International audience

Many researches have been made on the modeling of transmission lines. Nowadays, it takes place in the realm of distributed parameter systems. Nevertheless, while the analytical solutions get more sophisticated, approximate models need to be developed for applications such as the protection of high voltage lines.Thus we study rational approximations of functions thanks to the Mittag-Leffler's theorem and to the continued fraction expansions. These methods allow the generalization of the Foster and Cauer's syntheses to infinite order impedances. Some examples are given as applications in different physical domains.Eventually, we put in evidence how this approach can be extended to matrix functions, that gives a method to model polyphase lines with few constraints. This result allows to propose a fault identification algorithm on an electrical power transmission line., La modélisation des lignes électriques a donné lieu à de nombreux travaux. De nos jours, elle s'inscrit dans le contexte plus large de l'étude des systèmes à paramètres répartis. Cependant, au fur et à mesure que se raffinent les solutions analytiques, des modèles approchés doivent être développés pour des applications telles que la protection des lignes à haute tension.Nous étudions donc des approximations rationnelles de fonctions grâce au théorème de Mittag-Leffler et au développement en fractions continues. Ces approches permettent de généraliser les synthèses de Foster et Cauer aux impédances d'ordre infini. Des exemples d'applications dans différents domaines de la physique sont donnés.Nous montrons enfin que cette approche peut s'étendre aux fonctions matricielles et fournir une méthode peu contraignante de modélisation des lignes polyphasées. Ce dernier résultat permet de proposer un algorithme d'identification de défauts sur une ligne de transport d'énergie électrique.

International audience

International audience; Functional Electrical Stimulation (FES) is an attractive solution to restore some lost or failing physiological functions. Obviously, the FES system may be hazardous for patient and the reliability and dependability of the system must be maximal. Unfortunately, the present context, where the associated systems are more and more complex and their development needs very cross-disciplinary experts, is not favorable to safety. Moreover, the direct adaptation of the existing dependability techniques from domains such as space or automotive is not suitable. Firstly, this paper proposes a strategy for risk management at system level for FES medical implant. The idea is to give a uniform framework where all possible hazards are highlighted and associated consequences are minimized. Then, the paper focuses on critical parts of the FES system: analog micro-circuit which generates the electrical signal to electrode. As this micro-circuit is the closest to the human tissue, any failure might involve very critical consequences for the patient. We propose a concurrent top-down and bottom-up approach where the critical elements are highlighted and an extended risk analysis is performed.

International audience; In the context of functional electrical stimulation it is of high interest to have an objective measure of the effect of stimulation and to get a sensitive feedback from afferent neural signal. Many studies aim to detect or record this information from inside the nerve but they have to overcome several difficulties. In chronic implants, measure of the nerve activity has to be little invasive making the use of a cuff electrode very suitable. The main issues with this kind of electrode are parasitic noise and poor selectivity of the recorded signal. In this paper, we propose an optimized layout for multipolar recording electrode. The main idea is to find the best value for the inter-pole distance and the most relevant processing in order to both improve selectivity in the nerve and to reject external parasitic signals. In this study, we put emphasis on simulation of action potential as a method to help the electrode specification. The amplitude of the expected signal is evaluated in both spatial and frequency domains, with respect to axons variability. Then, the selectivity of the proposed design is compared to state-of-art electrode layout. The proposed design, with the associated pre-processing shows a real improvement of the electrode selectivity and a very efficient parasitic signal rejection. The drawback is a decrease of the sensitivity that nevertheless remains compatible with integrated micro-circuit amplifiers.

International audience; A nerve is an enclosed, cable-like bundle of peripheral axons. Each axon or set of axons carries neural afferent or efferent information. Many applications need to detect or record these specific nervous data inside the nerve but it is a big challenge. The main issue is to achieve a good selectivity inside the nerve without being invasive. In this context, we propose a new layout of multipolar electrode allowing a very high level of spatial selectivity. This electrode has a flat-interface electrode with an array of poles. The idea is to find the best value for the inter-pole distance and the most suitable post processing in order to both improve selectivity in the nerve and reject external parasitic signals. In this preliminary work, we put emphasis on the simulation of the action potential as a method to help the electrode specification.

Ce papier étudie la sûreté de fonctionnement (SdF) d'un microstimulateur implanté dans le corps humain. Bien qu'il s'agisse d'une application critique, il n'existe pas d'étude standard dans ce domaine contrairement à l'aérospatiale, l'automobile,...Ce papier illustre les caractéristiques générales de la SdF appliqués aux implants médicaux. Ces systèmes délivrent un signal électrique (Stimulation Electrique Fonctionnel) aux nerfs ou aux muscles afin de restaurer des capacités endommagées.

National audience; En cas de dysfonctionnement du système nerveux, la stimulation électrique fonctionnelle, qui consiste à provoquer des contractions musculaires artificielles par stimulations électriques, a prouvé son efficacité dans l'aide à la restauration de fonctions neurales. Les informations sensorielles, provenant de capteurs naturels et se propageant sur les fibres nerveuses afférentes, pourraient être utilisées comme informations de retour pour un système de stimulation électrique fonctionnelle contrôlé en boucle fermée. Dans le but de faire l'acquisition de ces informations, nous proposons une nouvelle structure d'électrode cuff multipolaire, ainsi qu'un système d'amplification adapté.

Many researches have been made on the modeling of transmission lines. Nowadays, it takes place in the realm of distributed parameter systems. Nevertheless, while the analytical solutions get more sophisticated, approximate models need to be developed for applications such as the protection of high voltage lines.Thus we study rational approximations of functions thanks to the Mittag-Leffler's theorem and to the continued fraction expansions. These methods allow the generalization of the Foster and Cauer's syntheses to infinite order impedances. Some examples are given as applications in different physical domains.Eventually, we put in evidence how this approach can be extended to matrix functions, that gives a method to model polyphase lines with few constraints. This result allows to propose a fault identification algorithm on an electrical power transmission line.; La modélisation des lignes électriques a donné lieu à de nombreux travaux. De nos jours, elle s'inscrit dans le contexte plus large de l'étude des systèmes à paramètres répartis. Cependant, au fur et à mesure que se raffinent les solutions analytiques, des modèles approchés doivent être développés pour des applications telles que la protection des lignes à haute tension.Nous étudions donc des approximations rationnelles de fonctions grâce au théorème de Mittag-Leffler et au développement en fractions continues. Ces approches permettent de généraliser les synthèses de Foster et Cauer aux impédances d'ordre infini. Des exemples d'applications dans différents domaines de la physique sont donnés.Nous montrons enfin que cette approche peut s'étendre aux fonctions matricielles et fournir une méthode peu contraignante de modélisation des lignes polyphasées. Ce dernier résultat permet de proposer un algorithme d'identification de défauts sur une ligne de transport d'énergie électrique.

Many researches have been made on the modeling of transmission lines. Nowadays, it takes place in the realm of distributed parameter systems. Nevertheless, while the analytical solutions get more sophisticated, approximate models need to be developed for applications such as the protection of high voltage lines.Thus we study rational approximations of functions thanks to the Mittag-Leffler's theorem and to the continued fraction expansions. These methods allow the generalization of the Foster and Cauer's syntheses to infinite order impedances. Some examples are given as applications in different physical domains.Eventually, we put in evidence how this approach can be extended to matrix functions, that gives a method to model polyphase lines with few constraints. This result allows to propose a fault identification algorithm on an electrical power transmission line.; La modélisation des lignes électriques a donné lieu à de nombreux travaux. De nos jours, elle s'inscrit dans le contexte plus large de l'étude des systèmes à paramètres répartis. Cependant, au fur et à mesure que se raffinent les solutions analytiques, des modèles approchés doivent être développés pour des applications telles que la protection des lignes à haute tension.Nous étudions donc des approximations rationnelles de fonctions grâce au théorème de Mittag-Leffler et au développement en fractions continues. Ces approches permettent de généraliser les synthèses de Foster et Cauer aux impédances d'ordre infini. Des exemples d'applications dans différents domaines de la physique sont donnés.Nous montrons enfin que cette approche peut s'étendre aux fonctions matricielles et fournir une méthode peu contraignante de modélisation des lignes polyphasées. Ce dernier résultat permet de proposer un algorithme d'identification de défauts sur une ligne de transport d'énergie électrique.

International audience; In the context of functional electrical stimulation (FES), it would be of great interest to get reliable sensitive information directly from the nerve signals. To achieve the chronic recording of electrical activity of the axons it is necessary to develop the electrode and the associated implantable integrated circuit ASIC. In this paper, we have proposed a novel design of multipolar cuff electrodes. This design is closely linked to a low-level analog signal processing assigned to a dedicated preamplifier. This paper presents the system-oriented development of this biosignal sensor, from the modeling of the neurons and the electrode to the microcircuit design. We put emphasis on the simulation of the action potential to assist the sensor specification.

The aim of model reduction is to obtain the simplest model while reflecting as far as possible the dynamic behaviour of a system. First, we present the reduction method based on a complex admittance matrix [ Y(s) ] of the whole initial model. From which we obtain by two inversions, the matrix , which can be interpreted as a reduced network. We give an example of application of the numeric reduction method. The same method is applied with success to analytical expression of impedances kept from the quadrupole representation of heat conduction. In order to simulate easily the transient responses of analytical models, we present the development of analytical impedance in the form of an equivalent network, which is proved to be very efficient during simulations. The first application is done with a heterogeneous system made of two bars of different materials, one is made of copper and the other is made of steel. The second application is done with a more complex thermal system constituting a cooler with 7 branches. This cooler is reduced to 1, 2 and 3 nodes to obtain the simplest model while reflecting as far as possible the dynamic behaviour. This document presents a generalisation of the method of network reduction in the case where the models' impedances have analytical expressions. In this case, we show that contrary to the numerical reduction, which approximates admittances to the first order, we are free to choose the model order, whatever the kept nodes, in such a manner that the model's bandwidth is considered as sufficient. The resulting equivalent networks allow easy simulations of the transient responses thanks to standard electric network softwares. Beyond the dealt examples of analytical reduction, for industrial systems non analytically calculable but governed by an equation of heat diffusion, the structures (topologies) of the reduced models would be the same. That opens prospects to obtain thermal reduced models from an automated networking realised in CAD.

A special issue of the IEEE Transactions on Biomedical Circuits and Systems (http://ewh.ieee.org/soc/cas/tbcas/) will be edited based on the very best papers of the conference.; International audience; Cuff electrodes have several advantages for in situ recording of ENG signal. They are easy to implant and not very invasive for the patient. Nevertheless, they are subject to parasitic background noise, especially the EMG generated by the muscles. We show that the use of large numbers of poles can increase the sensitivity of cuff electrodes as well as their selectivity with respect to a efficient noise rejection. We investigate several configurations and compare the performances of a tripolar cuff electrode versus a multipolar one in numerical simulation. One the other hand the use of cuff electrodes leads to the recording of the sum of the signals generated by all the axons within the nerve. This puts in evidence the need of signal separation techniques that require a large amount of information. Again, we show that multipolar electrodes can solve this problem since poles can be switched one to another, provided that they are distributed along a regular tessellation. Finally, we present the structure of an ASIC preamplifier aimed to obtain the Laplacian of the potential by spatial filtering and rejecting low-frequency noise.