Laboratoire des Signaux et Systemes

Gif-sur-Yvette, France

Laboratoire des Signaux et Systemes

Gif-sur-Yvette, France
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Detorakis G.I.,Laboratoire des signaux et systemes | Detorakis G.I.,University Paris - Sud | Chaillet A.,Laboratoire des signaux et systemes | Chaillet A.,University Paris - Sud | And 6 more authors.
Frontiers in Neuroscience | Year: 2015

Several disorders are related to pathological brain oscillations. In the case of Parkinson's disease, sustained low-frequency oscillations (especially in the β-band, 13-30Hz) correlate with motor symptoms. It is still under debate whether these oscillations are the cause of parkinsonian motor symptoms. The development of techniques enabling selective disruption of these β-oscillations could contribute to the understanding of the underlying mechanisms, and could be exploited for treatments. A particularly appealing technique is Deep Brain Stimulation (DBS). With clinical electrical DBS, electrical currents are delivered at high frequency to a region made of potentially heterogeneous neurons (the subthalamic nucleus (STN) in the case of Parkinson's disease). Even more appealing is DBS with optogenetics, which is until now a preclinical method using both gene transfer and deep brain light delivery and enabling neuromodulation at the scale of one given neural network. In this work, we rely on delayed neural fields models of STN and the external Globus Pallidus (GPe) to develop, theoretically validate and test in silico a closed-loop stimulation strategy to disrupt these sustained oscillations with optogenetics. First, we rely on tools from control theory to provide theoretical conditions under which sustained oscillations can be attenuated by a closed-loop stimulation proportional to the measured activity of STN. Second, based on this theoretical framework, we show numerically that the proposed closed-loop stimulation efficiently attenuates sustained oscillations, even in the case when the photosensitization effectively affects only 50% of STN neurons. We also show through simulations that oscillations disruption can be achieved when the same light source is used for the whole STN population. We finally test the robustness of the proposed strategy to possible acquisition and processing delays, as well as parameters uncertainty.

Laghrouche S.,University of Technology of Belfort - Montbéliard | Laghrouche S.,University of Burgundy | Harmouche M.,Actility | Chitour Y.,Laboratoire des Signaux et Systemes
IEEE Transactions on Automatic Control | Year: 2017

In this paper, we present a generalization of the super-twisting algorithm for perturbed chains of integrators of arbitrary order. This higher order super-twisting (HOST) controller is homogeneous with respect to a family of dilations and is continuous. It is built as a dynamic controller (with respect to the state variable of the chain of integrators) and the convergence analysis is performed by the use of a homogeneous strict Lyapunov function which is explicitly constructed. The effectiveness of the controller is finally illustrated with simulations for a chain of integrators of order four, first pure then perturbed, where we compare the performances of two HOST controllers. © 1963-2012 IEEE.

Doria-Cerezo A.,Polytechnic University of Catalonia | Bodson M.,University of Utah | Batlle C.,Polytechnic University of Catalonia | Ortega R.,Laboratoire des Signaux et Systemes
IEEE Transactions on Control Systems Technology | Year: 2013

In this brief, a new control scheme is presented for the doubly fed induction machine (DFIM). The proposed control algorithm offers the advantages of proven stability and remarkable simplicity. In contrast to the classical vector control method, where the DFIM is represented in a stator-flux-oriented frame, a model with orientation of the stator voltage is adopted. This approach allows the decomposition of the active and reactive powers on the stator side and their regulation on the rotor side. A main contribution of this brief is the use of the Hurwitz test for polynomials with complex coefficients that has had little prior application in control theory. This results in a proof that a proportional-integral (PI) control regulating the stator currents ensures global stability for a feedback-linearized DFIM. The specific condition that the PI gains must satisfy is derived as a simple inequality. The PI controller has a particular structure that directly relates the $d$-component of the rotor voltages to the $q$-component of the stator currents and vice versa. The feedback linearization stage only uses the direct measurement of the rotor and stator currents and is thus easily implementable. Furthermore, it is also shown that the PI controller (without the feedback linearization terms) is also stable for a large range of control gains and does not require the knowledge of the machine parameters. Finally, the control system is validated in simulations and in experiments. © 2013 IEEE.

Nuno E.,University of Guadalajara | Basanez L.,University of Barcelona | Ortega R.,Laboratoire des Signaux et Systemes
Automatica | Year: 2011

This tutorial revisits several of the most recent passivity-based controllers for nonlinear bilateral teleoperators with guaranteed stability properties. These schemes, which include scatteringbased, damping injection and adaptive controllers, ensure asymptotic stability in multiple situations that range from constant to variable time-delays, with or without scattering transformation and with or without position tracking capabilities. Although all controllers exploit the basic property of passivity of the teleoperators, they have been developed invoking various analysis and design tools, which complicates their comparison and relative performance assessment. The objective of this paper is to present a unified theoretical frameworkbased on a general Lyapunovlike functionthat, upon slight modification, allows to analyze the stability of all the schemes. © 2011 Elsevier Ltd. All rights reserved.

Liu X.,Beijing Jiaotong University | Liu X.,Zhejiang University | Ortega R.,Laboratoire des Signaux et Systemes | Su H.,Zhejiang University | Chu J.,Zhejiang University
Systems and Control Letters | Year: 2011

A new framework to design immersion and invariance adaptive controllers for nonlinearly parameterized, nonlinear systems was recently proposed by the authors. The key step is the construction of a monotone mapping, via a suitable selection of a controller tuning function, which has to satisfy some integrability conditionsthis translates into the need to solve a partial differential equation (PDE). In this paper this result is extended providing some answers to the questions of characterization of "monotonizable" systems and solvability of the PDE. First, adding to the design a nonlinear dynamic scaling, we obviate the need to solve the PDE. Second, for the case of factorizable nonlinearities, the following results are established. (i) It is shown that the monotonicity condition is satisfied if a linear matrix inequality is feasible. (ii) Directly verifiable involutivity conditions that ensure the solution of the PDE are presented. (iii) An explicit formula for the required tuning function is given, provided the regressor matrix satisfies some rank conditions. Hence, adding a dynamic scaling, this yields a constructive solution to the problem. © 2010 Elsevier B.V. All rights reserved.

Henriksson T.,Laboratoire des Signaux et Systemes | Henriksson T.,Mälardalen University | Joachimowicz N.,Laboratoire des Signaux et Systemes | Conessa C.,Laboratoire des Signaux et Systemes | Bolomey J.-C.,Laboratoire des Signaux et Systemes
IEEE Transactions on Instrumentation and Measurement | Year: 2010

Microwave imaging is recognized as a potential candidate for biomedical applications, such as breast tumor detection. In this context, the capability of a planar microwave camera to produce quantitative imaging of high-contrast inhomogeneous objects is investigated. The image reconstruction is achieved by means of an iterative NewtonKantorovich algorithm. Promising numerical simulation results indicate that the planar geometry is suitable for quantitative imaging, as long as the signal-to-noise ratio is higher than 40 dB. Such a requirement is satisfied with the camera due to appropriate data averaging. Furthermore, different calibration techniques are discussed, aiming to reduce the model error, which results from the limitations of the numerical model involved in the reconstruction to accurately reproduce the experimental setup. The experimental work also includes the development of a phantom using a new fluid tissue equivalent mixture based on Triton X-100. As a final result, this paper shows the first reconstructed quantitative images of a high-contrast inhomogeneous 2-D object obtained by using experimental data from the camera. © 2010 IEEE.

Borja P.,Laboratoire des Signaux et Systemes | Cisneros R.,Laboratoire des Signaux et Systemes | Ortega R.,Laboratoire des Signaux et Systemes
Automatica | Year: 2016

Equilibrium stabilization of nonlinear systems via energy shaping is a well-established, robust, passivity-based controller design technique. Unfortunately, its application is often stymied by the need to solve partial differential equations, which is usually a difficult task. In this paper a new, fully constructive, procedure to shape the energy for a class of port-Hamiltonian systems that obviates the solution of partial differential equations is proposed. Proceeding from the well-known passive, power shaping output we propose a nonlinear static state-feedback that preserves passivity of this output but with a new storage function. A suitable selection of a controller gain makes this function positive definite, hence it is a suitable Lyapunov function for the closed-loop. The resulting controller may be interpreted as a classical PI—connections with other standard passivity-based controllers are also identified. © 2016 Elsevier Ltd

Chen J.,Stanford University | Yang S.,Laboratoire des Signaux et Systemes | Ozgur A.,Stanford University | Goldsmith A.,Stanford University
IEEE Transactions on Information Theory | Year: 2016

We consider communication over heterogeneous parallel channels, where a transmitter is connected to two users via two parallel channels: a multiple-input multiple-output (MIMO) broadcast channel (BC) and a noiseless rate-limited multicast channel. We characterize the optimal degrees of freedom (DoF) region of this setting when the transmitter has delayed channel state information (CSIT) regarding the MIMO BC. Our results show that jointly coding over the two channels strictly outperforms simple channel aggregation and can even achieve the instantaneous CSIT performance with completely outdated CSIT on the MIMO BC in the sum DoF sense; this happens when the multicast rate of the second channel is larger than a certain threshold. The main idea is to send information over the MIMO BC at a rate above its capacity and then use the second channel to send additional side information to allow for reliable decoding at both receivers. We call this scheme a two-phase overload-multicast strategy. We show that such a strategy is also sum DoF optimal for the K-user MIMO BC with a parallel multicast channel when the rate of the multicast channel is high enough and can again achieve the instantaneous CSIT performance (optimal sum DoF) with completely outdated CSIT. For the regime where the capacity of the multicast channel is small, we propose another joint coding strategy, which is sum DoF optimal. © 2016 IEEE.

Harmouche J.,Laboratoire des Signaux et Systemes | Harmouche J.,Laboratoire Of Genie Electrique Of Paris | Delpha C.,Laboratoire des Signaux et Systemes | Diallo D.,Laboratoire Of Genie Electrique Of Paris
IEEE Transactions on Energy Conversion | Year: 2015

This research deals with the discrimination between conditions of faults in rolling element bearings based on a global spectral analysis. This global spectral analysis allows to obtain spectral features with significant discriminatory power. These features are extracted from the envelope spectra of vibration signals without prior knowledge of the bearings specific parameters and the characteristic frequencies. These extracted spectral features will then be the global spectral signature produced by the bearing faults. Since the signature produced by the faults in bearing balls is very weak, and hard to be detected and identified, this paper proposes the linear discriminant analysis as part of the global spectral analysis method in order to improve the diagnosis of ball faults. The application on experimental vibration data acquired from bearings containing different types of faults with different small sizes shows the proficiency of the overall method. The Bhattacharyya distance is used to confirm the efficiency of the obtained results. © 1986-2012 IEEE.

Benammar M.,Huawei | Piantanida P.,Laboratoire des Signaux et Systemes | Shamai S.,Israel Electric
IEEE International Symposium on Information Theory - Proceedings | Year: 2015

This work investigates the Multicast Cognitive Interference Channel (CIFC) where many secondary users are interested in the same cognitive message. The focus is to study the role that Multiple Description (MD) coding can play under simultaneous transmissions. Though for the very weak, very strong, and mixed very weak/strong interference regimes, resorting to a Common Description (CD) alone is capacity achieving, in the weak interference regime it becomes crucial to resort to a more evolved coding scheme relying on multiple descriptions that could each accommodate differently the interference experienced at the secondary users. A Gaussian example illustrates this claim and various capacity results are likewise reported. © 2015 IEEE.

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