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International audience; A novel distributed consensus protocol, where only sampled position information is exchanged between neighboring agents, is designed for second-order multi-agent systems under a directed communication topology. This protocol allows to reach the consensus for asynchronous and aperiodic sampling periods, which means that every agent can send its measurements independently from its neighbors. Furthermore, the upper bound on the sampling periods can be chosen arbitrarily long by adapting the tuning parameters. This result is obtained by using a continuous-discrete time observer which allows to reconstruct the system state in real time from only discrete-time measurements. The feedback control gain is set according to the observer gain which is itself set according to the maximum sampling period.

International audience; While determining the order as well as the matrices of a black-box linear state-space model is now an easy problem to solve, it is well-known that the estimated (fully parameterized) state-space matrices are unique modulo a non-singular similarity transformation matrix. This could have serious consequences if the system being identified is a real physical system. Indeed, if the true model contains physical parameters, then the identified system could no longer have the physical parameters in a form that can be extracted easily. By assuming that the system has been identified consistently in a fully parameterized form, the question addressed in this paper then is how to recover the physical parameters from this initially estimated black-box form. Two solutions to solve such a parameterization problem are more precisely introduced. First, a solution based on a null-space-based reformulation of a set of equations arising from the aforementioned similarity transformation problem is considered. Second, an algorithm dedicated to nonsmooth optimization is presented to transform the initial fully parameterized model into the structured state-space parameterization of the system to be identified. A specific constraint on the similarity transformation between both system representations is added to avoid singularity. By assuming that the physical state-space form is identifiable and the initial fully parameterized model is consistent, it is proved that the global solutions of these two optimization problems are unique. The proposed algorithms are presented, along with an example of a physical system.

It is known that in general, \emph{frozen equivalent} (Linear Parameter-Varying) LPV models, \emph{i.e.}, LPV models which have the same input-output behavior for each constant scheduling signal, might exhibit different input-output behavior for non-constant scheduling signals. In this paper, we provide an analytic error bound on the difference between the input-output behaviors of two LPV models which are frozen equivalent. This error bound turns out to be a function of both the speed of the change of the scheduling signal and the discrepancy between the coherent bases of the two LPV models. In particular, the difference between the outputs of the two models can be made arbitrarily small by choosing a scheduling signal which changes slowly enough. An illustrative example is presented to show that the choice of the scheduling signal can reduce the difference between the input-output behaviors of frozen-equivalent LPV models.

R Reperes LES VEHICULES PROPRES Compensation active des pulsations de couple dans un vehicule hybride Par Slim TNANI, Patrick COIRAULT, Gerard CHAMPENOIS Laboratoire d'automatique et d'informatique industrielle, Ecole superieure d'ingenieurs, Poitiers Mots cles Filtreactif, Controle dynamique, Pulsations decouple, Vehicule hybride 1. Introduction Le moteur thermique est l'une des principales sources de vibration dans les vehicules. Depuis toujours, l'un des soucis des motoristes est d'attenuer cette nuisance vibra- toire et sonore. Pour cela ils agissent soit a la source en attenuant les pulsations de couple generees par le moteur thermique, soit en ameliorant l'isolation vibratoire des supports moteurs. Jusqu'a present, des solutions passives sont mises en oeuvre. Pour l'attenuation a la source, ces solutions sont basees sur des principes d'equilibrage du vilebrequin par des masselottes et par l'ajout d'un volant d'inertie sur l'arbre de transmission. Pour l'isolation vibratoire, les solutions consistent a optimiser les plots en caoutchouc supportant le moteur ; ils doivent etre a la fois raides pour maintenir le moteur, et souples pour l'isoler. Depuis 1

In this paper, we introduce and study important properties of the transformation of Affine Linear Parameter-Varying (ALPV) state-space representations into Linear Fractional Representations (LFR). More precisely, we show that (i) state minimal ALPV representations yield minimal LFRs, and vice versa, (ii) the input-output behavior of the ALPV representation determines uniquely the input-output behavior of the resulting LFR, (iii) structurally identifiable ALPV models yield structurally identifiable LFRs, and vice versa. We then characterize LFRs which correspond to equivalent ALPV models based on their input-output maps. As illustrated all along the paper, these results have important consequences for identification and control of systems described by LFRs.

International audience; This paper proposes an analysis of the static behavior of a SiC-MOSFET power transistor for temperature variations. The commercial transistor model (CMF10120D Cree 1200V/24A) is used. The approach consists to exploit the Spice electrical model provided by the constructor and to set its limits. Two main parameters: the threshold voltage and mobility are investigated to meet the needs of the static study and refine the temperature behavior of the Spice model. The obtained simulation results are compared to experimental measurements achieved in a static athermal mode.

In this paper we present a Kalman-style realization theory for linear parameter-varying state-space representations whose matrices depend on the scheduling variables in an affine way (abbreviated as LPV-SSA representations). We deal both with the discrete-time and the continuous-time cases. We show that such a LPV-SSA representation is a minimal (in the sense of having the least number of state-variables) representation of its input-output function, if and only if it is observable and span-reachable. We show that any two minimal LPV-SSA representations of the same input-output function are related by a linear isomorphism, and the isomorphism does not depend on the scheduling variable.We show that an input-output function can be represented by a LPV-SSA representation if and only if the Hankel-matrix of the input-output function has a finite rank. In fact, the rank of the Hankel-matrix gives the dimension of a minimal LPV-SSA representation. Moreover, we can formulate a counterpart of partial realization theory for LPV-SSA representation and prove correctness of the Kalman-Ho algorithm. These results thus represent the basis of systems theory for LPV-SSA representation., Comment: The main difference with respect to the previous version is as follows: typos have been fixed

International audience; In this paper, the challenging problem of determining the unknown parameters of an identifiable LTI state-space representation of a stable system is addressed by resorting to a specific H -norm-based optimization algorithm. More specifically, by assuming the availability of a reliable fully-parameterized representation of the system to identify, the algorithm developed herein consists in restructuring this initial black-box representation of the system dynamics via the optimization of a dedicated maximum eigenvalue-based criterion. This study shows that this H -norm-based approach can be seen as a good solution for the identification of gray-box LTI state-space representations and, by extension, as an interesting alternative or a reliable initialization step for the standard output-error techniques.

This paper deals with the design and evaluation of a single input single output H∞ voltage controller. The proposed approach is based on optimizing the system modeling in order to obtain a robust and high performance controller. The adopted methodology is realized in five steps: (1) modeling of the exciter machine, the main synchronous generator, and the rotating diode bridge; (2) linearization of the excitation system; (3) using of a fictitious three-phase capacitor to represent the variable synchronous generator load as exogenous input of the system; (4) linearization of the feedback control by using a SISO (single input/single output) controller; (5) application of H∞ control method associated with weighting functions. The performance of the controller has been evaluated by experimental tests under different operating points of the synchronous generator. In addition, the comparison with a standard industrial controller will allow us to highlight the efficiency of the proposed design approach.

Heat transfer problems in homogeneous medium obey to diffusion phenomenon. In this paper, we study heat conduction through a sphere which can be modelled with the help of fractional systems. We use models based on an original fractional integrator whose order 12 acts only over a limited spectral band. Simulations of front face thermal characterization consisting in measuring the inner surface temperature of the sphere where a random heat flux is applied are carried out. These simulations allow to validate the ability of the proposed estimation algorithms not only to rebuild the inner surface temperature but also to identify with a good accuracy the heat conductivity and diffusivity. Monte-Carlo simulations are also performed in order to provide statistical properties of the thermo-physical parameter estimates.

International audience; In this paper, a new approach for synchronization of dynamical networks with time-delays is proposed. It is based on stability theory of coupled time-delayed dynamical systems. Some new criteria for stability analysis which ensure the synchronization of the networks are analytically derived. Conditions for synchronization,in the form of Linear Matrix Inequality, are established. They use the Lyapunov and Krasovskii stability theories. In this approach, parameter uncertainties are introduced in the network model. Numerical simulations show the efficiency of the proposed synchronization analysis. A network of 4-GHz smart antenna array is used and analyzed in some details. This array provides a control of the direction of the radiation pattern.

Differential linear repetitive processes evolve over a subset of the upper-right quadrant of the 2D plane where the unique feature is a series of sweeps or passes through a set of dynamics governed by the solution of a linear matrix differential equation over a finite duration t ∈ [ 0 , α ] where α is termed the pass length or duration. On each pass an output, termed the pass profile, is produced, which acts as a forcing function on, and hence contributes to, the dynamics of the next pass profile. The result can be oscillations in the pass-to-pass direction that cannot be controlled by direct application of standard, or 1D linear systems theory. The existing stability theory demands a bounded-input bounded-output property uniformly, which in the case of the along-the-pass dynamics means for t ∈ [ 0 , ∞ ] and for ( k , t ) ∈ [ 0 , ∞ ] × [ 0 , ∞ ] ⊃ [ 0 , ∞ ] × [ 0 , α ] where the integer k ≥ 0 denotes the pass number or index. The pass length is always finite, however, and hence this stability theory could well be too strong in many cases and, in particular, impose very strong conditions in terms of control law design. This paper develops an alternative in such cases by relaxing the requirement for the bounded-input bounded-output property to hold when k → ∞ and t → ∞ simultaneously, provides an explanation of the implications of this in the frequency domain, and then develops control law design algorithms.

This paper, which deals with the stability of adaptive observers for induction motor in the regenerating mode, proposes a new approach that is consist of describing the error system in state space representation. With this formulation, it is possible to establish a cartography of unstable eigenvalues in the torque/speed plane, thus simplifying the stability analysis. Moreover, a new stability criterion is defined and used to realize stabilizing designs based on feedback gain as well as on the speed adaptation law.

In this paper, we present a direct power control (DPC) of three-phase pulsewidth modulation rectifier with constant switching frequency using space-vector modulation (SVM). The developed DPC scheme is based on the predictive control strategy to achieve direct control of instantaneous active and reactive power of the converter. For this purpose, at the beginning of each switching period, the required rectifier average voltage vector allowing the cancellation of active and reactive power tracking errors, at the end of the switching period, is calculated by means of predictive control algorithm in the sense of deadbeat control. The main advantages of the proposed control, compared to the works published in this subject, are that no need to use predefined switching table and voltage vector or virtual flux position, PI-based active and reactive power control loops are not necessary and constant-switching frequency. The proposed predictive direct power control was tested both in simulations and experimentally and compared with DPC using switching table. Results have proved excellent performance, and verify the validity of the proposed DPC scheme, which is much better than conventional DPC using switching table.

This research deals with a new modelling of a three-phase network in association with a parallel active filter with the help of linear state representation in closed loop. Using this approach the harmonics compensation of current networks is treated like a matter of disturbances rejection with the tools of linear control theory. This reasoning is different from common methods which are usually based on reference tracking control. The proposed strategy is validated firstly using simulation then using a test bench fitted with a three-phase shunt active filter whose control law is implemented in real time.

This paper proposes a novel and simple direct power control (DPC) scheme of a three-phase pulsewidth-modulated rectifier without the use of a predefined switching table. The converter switching state selection is based on fuzzy logic rules, using the instantaneous active and reactive power tracking errors as fuzzy logic variables. The basic idea of fuzzy rules synthesis is based on the knowledge of the instantaneous variation of active and reactive power. According to the input fuzzy variables and in a specific moment, the best switching state of the converter is chosen to restrict the instantaneous active and reactive power tracking errors simultaneously, for maintaining the DC-bus voltage close to the reference value and guarantying the unity-power-factor operation. The main advantages of the proposed DPC scheme, compared to the classical one, are that it is not necessary to use hysteresis comparators, and smooth control of active and reactive power is obtained during all sectors. Finally, the developed DPC was tested both in simulations and experimentally, and illustrative results are presented here. Results have proven excellent performance, and verify the validity of the proposed DPC scheme which is much better than the classical DPC.

This paper presents a neural approach to detect and locate automatically an interturn short-circuit fault in the stator windings of the induction machine. The fault detection and location are achieved by a feedforward multilayer-perceptron neural network (NN) trained by back propagation. The location process is based on monitoring the three-phase shifts between the line current and the phase voltage of the machine. The required data for training and testing the NN are experimentally generated from a three-phase induction motor with different interturn short-circuit faults. Simulation, as well as experimental, results are presented in this paper to demonstrate the effectiveness of the used method.

This paper deals with the problem of robust stability and robust stabilization for uncertain continuous singular systems with multiple time-varying delays. The parametric uncertainty is assumed to be norm bounded. The purpose of the robust stability problem is to give conditions such that the uncertain singular system is regular, impulse free, and stable for all admissible uncertainties. The purpose of the robust stabilization problem is to design a feedback control law such that the resulting closed-loop system is robustly stable. This problem is solved via generalized quadratic stability approach. A strict linear matrix inequality (LMI) design approach is developed. Finally, a numerical example is provided to demonstrate the application of the proposed method.

Heat transfer problems are subject to diffusion phenomenon, and can be modelled with the help of fractional systems. The simulation of these particular systems is based on a fractional integrator, where the non-integer behaviour occurs only within a limited spectral band. A first model, based on the use of one fractional integrator, has been already defined and tested on a thermal pilot. Starting from frequency considerations derived from the analysis of a diffusion problem, a more general approximation of the fractional system is proposed here. The new model is based on the use of two fractional integrator operators. This makes it possible to define a state-space model for simulation of transients, and to use an output-error technique in order to estimate the parameters of the model. Experimental results obtained for a thermal process illustrate the improvements obtained using the proposed model.

An original method for modelling heat transfer problems and particularly diffusion interfaces is presented in this communication. These interfaces can be approximated by fractional models, based on the use of the fractional integrator. Starting from frequency considerations, a more general approximation of the fractional system is proposed. It allows to define a statespace model for accurate simulation of transients, and to carry out an output-error technique in order to estimate the parameters of the model. Numerical simulations of the heat transfer problem are presented and used to illustrate the improvements of the proposed model in the linear case.

Numerical computation of the electric field strength and ionic space charge density in electrode systems consisting of ionizing wire and non-ionizing cylinder, connected to the same DC high-voltage supply and facing a grounded plate, is a difficult problem, which is of interest to several electrostatic processes applications. In a previous study a simple numerical method has been proposed to calculate the spatial distributions of electric field and ionic space charge in a case of a continuum and uniform corona discharge originating at the surface of the wire. The aim of the present paper is to improve the physical model of the corona discharge in this particular electrode configuration, by assuming a more realistic law of charge injection on the wire circumference. The computations were carried out for an ionizing wire of radius r =0.1 mm, located at different distances h from a metallic tubular support of radius R =13.4 mm.The initial conditions of the corona discharge took into account the non-uniformity of the charge injection around the ionizing wire electrode. The computational results were compared with those obtained under the assumption of uniform corona discharge. The comparison pointed out that neither the non-uniformity of the electric field nor that of the charge injection can be neglected. They depend on the geometry of the electrode system and affect the distribution of the electric field and of the space charge density in the inter-electrode gap.

International audience; In this chapter a new identification technique is introduced to estimate a linear fractional representation (LFR) of a linear parameter-varying (LPV) system from local experiments using a dedicated non-smooth optimization procedure. Having access to a reliable set of local models, this technique consists more specifically in optimizing an H∞-norm-based cost function measuring the fit between the local information (represented by the locally estimated LTI models) and the local behavior of a parameterized global LPV model. The method presented in this chapter results directly in an LPV model whose parametric matrices can be rational functions of the scheduling variables without any interpolation step (required usually by the local approach) and without writing the local fully parameterized LTI state-space models with respect to a coherent basis. On top of that, specific attention is paid to parameterized LPV models satisfying a fully parameterized or a physically structured linear fractional representation. This identification procedure is tested and validated with a simulation example.

In conventional internal combustion engines the periodic fuel combustion in cylinders and oscillating masses results in a pulsating engine torque. In hybrid power trains the electrical motor can be used to control such pulsations. In the paper, the authors propose a novel control strategy of torque pulsations on a hybrid vehicle. Using an active filter and an a.c. machine, which is mounted on the crankshaft to generate an inverse torque sequence, reduces the combustion engine pulsations. The control strategy is based on a multiobjective state feedback synthesis. A complete modelling of the hybrid propulsion of the vehicle is achieved. Simulation results highlight the interest of the control scheme.

This paper proposes a method to compute a static state feedback control law which achieves a non-strict pole assignment. The specification on the closed-loop poles is given in terms of a clustering region. The originality of this work is the choice of the region which can result from the union of disjoint and non-symmetric subregions. Such a choice is made possible by a technique that enables a partial pole placement via aggregation. The distribution of poles in various subregions can be chosen. The proposed conditions are formulated through an LMI approach and some robustness aspects are also considered from an analytical point of view.

This paper deals with the phenomenon of magnetic saturation in electrical machines. Taking magnetic saturation into account leads to non-linear models which need to develop parameter estimation techniques well adapted. At first, the study concerns an elementary model of saturated iron core coils and the physical parameter estimation of this non-linear model, thanks to a Non-linear Programming algorithm.

International audience; A new approach based on pattern recognition techniques and dedicated to the monitoring of non stationary systems is presented in this paper. More precisely, it consists of a recursive subspace identification algorithm combined with an adaptive classifier set for non stationary environment. The system identification method which provides a recursive estimation of a linear state space model is firstly described. Then, a feature vector representing the system functioning state is extracted from this estimated model. Next, the dynamical clustering algorithm which online learns the functioning modes and continuously determines the current mode of the system is introduced. Its auto adaptive and unsupervised abilities to take into account system modes evolutions are finally emphasized on simulation examples.

International audience; A new RF switched capacitor bandpass filter and its command circuit made up of a ring voltage controlled oscillator with 'XOR' gates are proposed. Implemented in a standard 0.35 m CMOS technology, this circuit is intended to be used in a subset of professional mobile phone applications [380-520 MHz]. Experiments carried out on a prototype show a tunable center frequency range of 260MHz [240-500 MHz], with a quality factor that can be as high as 300.

International audience; This paper describes a new association of a high-Q pseudo 8-path switched-capacitor (S-C) bandpass filter and its command circuit made up by a ring VCO with 'XOR' gates. The proposed circuit presents the possibility of tuning over a radio-frequency (RF) broadband allowing to sweep different channels with a high quality factor. Designed with CMOS process (0.35µm, for instance), this circuit is intended to replace the surface acoustic wave (SAW) filters in modern wireless receivers. Measurements carried out on a circuit demonstrator show a tunable center frequency range of 200MHz [300-500MHz], with a quality factor higher than 300.

This article deals with the estimation of physical parameters. This estimation is performed using an Output Error algorithm based on nonlinear optimization. Output Error techniques permit to obtain unbiased estimation and can be applied either to linear systems or nonlinear ones. The usual quadratic criterion is modified in order to include prior physical knowledge. A deterministic interpretation of this criterion is given in the linear parameter case and in the nonlinear parameter one. Estimation is also improved using direct optimization by physical parameters, owing to a generalized formulation of sensitivity functions. A real electrical engineering example illustrates the efficiency of this methodology.

This paper deals with the class of uncertain systems with multiple time delays. The stability and stabilizability of this class of systems are considered. Their robustness are also studied when the norm-bounded uncertainties are considered. Linear matrix inequality (LMIs) delay-dependent sufficient conditions for both stability and stabilizability and their robustness are established to check if a system of this class is stable and/or is stabilizable. Some numerical examples are provided to show the usefulness of the proposed results.

In this paper, the problem of robust matrix root-clustering is addressed. The studied matrices are subject to both polytopic and unstructured uncertainties. An original point is the large choice of clustering regions enabled by the proposed approach since these regions can be unions of possibly disjoint and non-symmetric subregions of the complex plane. The precise purpose is, considering a specified polytope, to determine the greatest robustness bound on the unstructured uncertainty such that robust matrix root-clustering is ensured. To reduce conservatism in the derivation of the bound, the reasoning relies on a framework based upon parameter-dependent Lyapunov functions. The bound value is computed by solving an ℒ ℳ ℐ problem. Copyright © 2003 John Wiley & Sons, Ltd.

The problem of robust stability of an induction motor is analysed in this paper. A classical feedback linearization (not detailed here) based on a nominal model is used to get a linear model to be studied. When uncertainty is taken into account, this model exhibits two features: first, it is subjected to a time-invariant polytopic uncertainty. Second, it has an additive nonlinear uncertainty. The main contribution of this paper lies in the stability analysis in the presence of both uncertainties. To enlarge the uncertainty domain, the size of the acceptable nonlinear uncertainty is maximized under stability constraints involving parameter-dependent Lyapunov functions.

The aim of this short communique is to adapt a result established by Bliman, related to the possible approximation of the solutions to real-parameter-dependent linear matrix inequalities (LMIs), to the special context of stability analysis of 2D discrete Roesser models. While Bliman considered the case of LMIs involving several real parameters, which is especially crucial for the analysis of linear systems against parametric deflections, the stability of Roesser models leads to consider LMIs with only one single complex parameter. Extending the results from real parameters to complex ones is not straightforward in our opinion. This is why the present note discusses precautions to be taken concerning this case before applying the results in a 2D context. Actually, it is shown that a well-known condition for structural stability of a 2D discrete Roesser can be relaxed into an LMI system whose solution polynomially depends on a single complex parameter over the unit circle., Comment: Updated version

International audience; This paper deals with the modeling of the gas flow supplied to a boiler in order to implement a soft sensor. This study is a part of ANR CHIC project which has an aim to minimize the measuring chain cost in the energy efficiency improvement programs. This implementation requires the estimation of a mathematical model that expresses the flow rate from the control signal of the solenoid valve and the gas pressure and temperature measurements. Two types of models are studied : LPV (Linear Parameter Varying) model with pressure and temperature as scheduling variables and a non-parametric model based on Gaussian processes.

International audience; In this paper, we propose as a first step a software solution to measure the electrical power consumed in an industrial furnace intended essentially for heat treatments. The soft sensor is constructed from the power physical measurement taken as the output of the set (dimmer + resistances), and the control signal measurement provided by a controller with an unknown structure. The second step consists in a detection of faults like a resistance disconnection, for instance. This phase requires the knowledge of the controller model and the furnace system. An overparametrization method was chosen for the controller estimation. An indirect closed-loop Input-Output (IO) identification approach was used for the furnace model estimation through a Tailor-Made and a decomposition of the closed-loop algorithms. A validation with two other experimental tests concludes the paper.

International audience; This paper proposes a multi-model based approach that estimates joint position and collision detection of a lightweight electric actuator dedicated to manipulation tasks. Taking advantage of an optimized back-drivable mechatronic design, the use of proprioceptive measures at the motor level enables the estimation of the unmeasured terminal position of the mechanical motor-to-joint transmission and force contact disturbance. A polytopic formulation is introduced based on an accurate model of the mechatronic transmission. Then, a multi-model observer-based estimator is synthesized using root-clustering for exteroceptive variables estimation without additional position/force sensor. The approach is experimentally validated with a single degree-of-freedom manipulator.

International audience; The tribo-aero-electrostatic separator achieves the selective sorting of mixed granular insulating materials in a fluidized bed affected by an electric field orthogonally oriented to the direction of the fluidization air. The aim of the present paper is to optimize the design and the operation of such a separator, i.e. maximize the total mass of the granules collected at the two electrodes that generate the electric field. The experiments were performed for four different electrode configurations. The granular mixtures to be separated were composed of Acrylonitrile Butadiene Styrene (ABS) and High Impact Polystyrene (HIPS) originating from the recycling of waste electric and electronic equipment (WEEE). The typical granule size was in the range 2 to 4.5 mm. The highest separation efficiency was obtained when the electric field in the active zone was intensified by the use of an additional electrode connected to the ground and when the collecting electrodes were covered by a thin insulating layer, preventing charge leakage from the particles in contact with them.

Lattice gas cellular automata (Lgca) are particular cellular automata that imitate the behavior of par- ticles moving on a lattice. We used a particular set of Lgca rules, called hpp, to mix bits in data blocks and obtain a symmetric cryptographic algorithm. The encryption and decryption keys are the positions of perturbation sites on the lattice (walls). Basically, this paper presents an original way to perform cryp- tographic operations, based on cellular automata. In this paper, we show several characteristics about our algorithm: typical block size (2^(2n-1) ), key-length (2^n ), number of rounds (2^(n+1) ). We also evaluate avalanche and strict avalanche properties with respect to key and plain text. Finally, we highlight the underbellies of our method and give clues to solve them.

This paper describes requirement for wireless transmission of Chaotic Code Division Multiplexed Access (Chaotic CDMA) and it focuses on real-time synchronization algorithm embedded into electronic programmable device. CDMA with quasi-orthogonal codes is used to allow multi-users to transmit simultaneously in the same channel. Since the channel is shared between all users, the receiver system has to cope with channel noise and overall with interference from other users. As a result, one of the main problems of communication with quasi-orthogonal chaotic codes is to implement a real time decoder in presence of noise. Even if set-membership algorithm are efficient in real time synchronization of chaotic discrete generators in the presence of noise, these algorithms require a large memory resource. In this paper, we propose an evolution of set-membership algorithm toward genetic algorithm to be implemented into electronic programmable device. The advantage of genetic algorithm compared with set-membership algorithm is that they require a fixed size of memory.

International audience; This paper presents a power amplifier (PA) cascade model, using two polynomial functions for amplitude and phase variations and multiple delay taps. This model allows an accurate modeling of the output envelope distortion and spectral asymmetries. To extract the model coefficients and delays for each non linearity order, an analytical method is developed. This method uses the Fourier transform of the output gain and phase to calculate all the parameters. To demonstrate the performances of this modeling approach, comparison between measured and simulated data has been performed.

International audience; This paper considers the analysis and the design of an array of two NMOS differential oscillators coupled through a resistor. A new writing of the nonlinear equations proposed by R. York to describe the oscillators' locked states but limited for the specific case of a resistive coupling is presented. The new system permits the calculation of the free-running frequencies of the oscillators when a specific phase shift is desired. This has led to the modeling of the two coupled NMOS differential oscillators as two coupled differential Van der Pol oscillators, with a resistive coupling network. A good agreement between the circuit, the model and the theory was found, giving some design considerations for a network of two differential oscillators coupled through one resistor.

International audience; In the present paper, the nonlinear Internal Model Control (IMC) method is introduced and applied to linearize high frequency power amplifiers (PAs). The IMC is based on the description of a process model and of a controller. It is shown that baseband frequency descriptions are suitable for the model and the controller. Their description parameters are derived from input and output modulation signals processed in Cartesian form. Simulation results are given to illustrate the design procedure and to demonstrate the performances of the IMC linearizer.

International audience; In this paper, a new linearization algorithm of Power Amplifier, based on Kalman filtering theory is proposed for obtaining fast convergence of the adaptive digital predistortion. The proposed method uses the real-time digital processing of baseband signals to compensate the nonlinearities and memory effects in radio-frequency Power Amplifier. To reduce the complexity of computing in classical Kalman Filtering, a sliding time-window has been inserted which combines off-line measurement and on-line parameter estimation with high sampling time to track the changes in the PA characteristics. We evaluated the performance of the proposed linearization scheme through simulation and experiments. Using digital signal processing, experimental results with commercial power amplifier are presented for multicarrier signals to demonstrate the effectiveness of this new approach.

Lyapunov stability of fractional differential equations is addressed in this paper. The key concept is the frequency distributed fractional integrator model, which is the basis for a global state space model of FDEs. Two approaches are presented: the direct one is intuitive but it leads to a large dimension parametric problem while the indirect one, which is based on the continuous frequency distribution, leads to a parsimonious solution. Two examples, with linear and nonlinear FDEs, exhibit the main features of this new methodology.

This paper deals with the robust S -regularity of an uncertain linear matrix pencil E λ - A and its applicability to the analysis of uncertain linear descriptor models of the form E x ˙ = Ax (for the continuous case) or Ex k + 1 = Ax k (for the discrete case). LMI (Linear Matrix Inequality)-based conditions for the robust S -regularity of E λ - A are established when both A and E are affected by LFT (Linear Fractional Transform)-based uncertainties. These conditions, though sufficient, are also necessary in numerous cases of practical interest. Moreover, the relevance of the conditions for the analysis of the D -admissibility of descriptor models ( D -stability and impulse freeness or causality) is also discussed.

This paper presents an analysis and a modeling approach to obtain a small-signal model design and the digital implementation of a linear control technique for single-phase boost power factor correctors (PFC). Such converters present nonlinear characteristics and approximations of them are used to drive the models. The proposed circuit significantly improves the dynamic response of the converter to load steps without the need of a high crossover frequency of the voltage loop by adding low-pass filter. So, a low distortion of the input current is easily achieved. This controller has been verified via simulation in Simulink using a continuous time plant model and a discrete time controller. Real-time implementation is performed on an experimental test bench utilizing a rapid prototyping tool. The controller is experimentally confirmed for steady-state performance and transient response.

Heat transfer in homogeneous media obeys to diffusion phenomenon which can be modelled with the help of fractional systems. In this paper, we use a parsimonious black box model based on an original fractional integrator whose order 12 acts only over a limited spectral band. We carried out simulations of front face thermal experimentations which consist in measuring the temperature at the surface of a material where a random heat flux is applied. We consider the characterization of the thermal behaviour of a wall or a sphere. These simulations show the ability of the fractional model, thanks to an output error identification technique, to obtain accurate estimation of diffusion interface temperature evolution as well as frequency response using time data series for the two considered geometries. Experimental results are given in the case of the sphere.

National audience; Cet article présente un modèle d'amplificateur utilisant plusieurs cellules de retard afin de modéliser les asymétries spectrales des raies d'intermodulation. L'asymétrie spectrale est caractérisée par une distorsion de l'amplitude et de la phase de l'enveloppe du signal de sortie. L'analyse des déformations d'enveloppe est utilisée pour obtenir les coefficients et les retards du modèle. Des simulations sous ADS sont utilisées pour montrer l'intérêt du modèle.