Laboratoire d’analyse et d’architecture des systèmes
O.LOPEZ SANTOS, L.MARTINEZ SALAMERO, G.GARCIA, H.VALDERRAMA-BLAVI, D.A.ZAMBRANO-PRADA
MAC, URV, Unibague
Revue Scientifique : IEEE Transactions on Power Electronics, Vol.32, N°3, pp.2253-2264, Mars 2017, DOI 10.1109/TPEL.2016.2557582 , N° 16132
The conduction modes of the quadratic boost converter are explored in the context of high DC gain applications. A complete analytical description of the steady-state behavior of the converter operating in four possible inductor current discontinuous conduction modes is presented. Boundaries between modes are determined together with the corresponding transitions. The study covers the operation of the converter using a pulse width modulator (PWM) for constant switching frequency, and employing a hysteresis comparator for variable switching frequency. Both cases are analyzed for the same set of converter parameters and different constant resistive loads, while the converter is fed by a low DC voltage ranging from 20 to 30 VDC. Several simulations are used to verify the waveforms and average values predicted by the theoretical analysis. Experimental results in a 60 W prototype are in good agreement with the theoretical predictions, and efficiency measurements reveal that one of the discontinuous conduction modes can compete with the continuous conduction mode in high DC gain applications.
A.BISOFFI, L.ZACCARIAN, M.DA LIO, D.CARNEVALE
Trento, MAC, Rome
Revue Scientifique : Automatica, Vol.77, pp.344-352, Mars 2017 , N° 17019
In AC/DC converters, a peculiar periodic nonsmooth waveform arises, the so-called ripple. In this paper we propose a novel model that captures this nonsmoothness by means of a hybrid dynamical system performing state jumps at certain switching instants, and we illustrate its properties with reference to a three phase diode bridge rectifier. As the ripple corrupts an underlying desirable signal, we propound two observer schemes ensuring asymptotic estimation of the ripple, the first with and the second without knowledge of the switching instants. Our theoretical developments are well placed in the context of recent techniques for hybrid regulation and constitute a contribution especially for our second observer, where the switching instants are estimated. Once asymptotic estimation of the ripple is achieved, the ripple can be conveniently canceled from the desirable signal, and thanks to the inherent robustness properties of the proposed hybrid formulation, the two observer schemes require only that the desirable signal is slowly time varying compared to the ripple. Exploiting this fact, we illustrate the effectiveness of our second hybrid observation law on experimental data collected from the Joint European Torus tokamak.
C.TESSIER, F.VIALLET, A.MARY, B.TONDU, L.BAUDOUIN, P.DUCOURNAU, I.QUEINNEC, G.MOCHEL, C.VARENNE, N.DESSENS
ONERA, EFTS, LIRCES, Nice, GEPETTO, MAC, LISST, Toulouse, URFIST-UFTMIP, TRACES, UT2J
Rapport LAAS N°17018, Février 2017, 56p.
Les écoles doctorales du site toulousain ont demandé fin 2015 que l’École Des Docteurs pilote un groupe de travail permettant de développer une formation à « l’Éthique de la Recherche et à l’intégrité scientifique ». Un groupe de chercheurs et d’enseignants-chercheurs, identifiés grâce à un appel à participation diffusé dans les écoles doctorales toulousaines, a développé un « kit de formation » comprenant : un diaporama support de cours, des propositions de dilemmes éthiques formatés et ce guide pratique à destination des formateurs. Ces documents sont inspirés du Cahier « Proposition de formation doctorale ; Initiation à l’éthique de la recherche scientifique » de la CERNA (Commission de réflexion sur l’Éthique de la Recherche en sciences et technologies du Numérique d’Allistene), des propositions des différents acteurs du groupe de travail, issus de disciplines diverses et du retour d’expérience des 8 premières journées de formation données à des groupes de doctorants issus de différentes écoles doctorales . L’Université de Toulouse est la première en France où cette formation est dispensée de manière transversale à tous les doctorants. Les échanges interdisciplinaires (entre formateurs et entre étudiants) sont particulièrement fructueux pour la dynamique de formation, qui se doit d’être participative. Cette formation est donnée en binôme, chaque binôme comprenant un intervenant issu des disciplines science, technologie, santé, ingénierie et un intervenant issu des sciences humaines et sociale, droit économie, gestion. Pendant l’année universitaire 2015-2016, cette formation a été testée lors de 4 sessions. Elle a été reconduite à plus grande échelle pour l’année universitaire 2016-2017, avec des binômes « ancien formateur/nouveau formateur », permettant ainsi d’assurer la formation des formateurs tout en conservant la cruciale complémentarité disciplinaire. À ce jour sur le site toulousain, ce sont donc une douzaine d’intervenants chercheurs, enseignants-chercheurs, ingénieurs et personnels techniques de recherche et de formation qui ont formé plus de 130 doctorants de disciplines et horizons différents.
G.VALMORBIDA, A.GARULLI, L.ZACCARIAN
L2S, DII Siene, MAC
Revue Scientifique : Automatica, Vol.76, pp.164-168, Février 2017 , N° 17020
Sufficient conditions are presented for regional stability and nonlinear L2mL2m gain analysis of linear systems subject to saturation, based on piecewise polynomial Lyapunov functions. The proposed conditions are formulated in terms of convex optimization problems and improve existing results both for the quadratic (L2L2 gain) and the polynomial (L2mL2m gain) cases.
Y.EBIHARA, D.PEAUCELLE, D.ARZELIER
Revue Scientifique : IEEE Transactions on Automatic Control, Vol.62, N°2, pp.652-667, Février 2017, doi 10.1109/TAC.2016.2558287 , N° 14557
This paper is concerned with the analysis and synthesis of interconnected systems constructed from heterogeneous positive subsystems and a nonnegative interconnection matrix. We first show that admissibility, to be defined in this paper, is an essential requirement in constructing such interconnected systems. Then, we clarify that the interconnected system is admissible and stable if and only if a Metzler matrix, which is built from the coefficient matrices of positive subsystems and the nonnegative interconnection matrix, is Hurwitz stable. By means of this key result, we further provide several results that characterize the admissibility and stability of the interconnected system in terms of the Frobenius eigenvalue of the interconnection matrix and the weighted L1-induced norm of the positive subsystems again to be defined in this paper. Moreover, in the case where every subsystem is SISO, we provide explicit conditions under which the interconnected system has the property of persistence, i.e., its state converges to a unique strictly positive vector (that is known in advance up to a strictly positive constant multiplicative factor) for any nonnegative and nonzero initial state. As an important consequence of this property, we show that the output of the interconnected system converges to a scalar multiple of the right eigenvector of a nonnegative matrix associated with its Frobenius eigenvalue, where the nonnegative matrix is nothing but the interconnection matrix scaled by the steady-stage gains of the positive subsystems. This result is then naturally and effectively applied to formation control of multi-agent systems with positive dynamics. This result can be seen as a generalization of a well-known consensus algorithm that has been basically applied to interconnected systems constructed from integrators.
P.BETTIOL, B.BONNARD, A.NOLOT, J.ROUOT
LM, Brest, IMB, Bourgogne, MAC
Rapport LAAS N°17008, Janvier 2017, 23p.
In , based on the observation of copepods, Takagi proposed a model to analyze the swimming of microorganisms using sinusoidal paddling or sequential paddling followed by a recovery stroke in unison, and they are compared with the concept of efficiency. Our aim is to provide an interpretation in the frame of optimal control theory and sub-Riemannian geometry. The Maximum principle is used to select two types of periodic control candidates as minimizers: sinusoidal up to time repa-rameterization and the sequential paddling, interpreted as an abnormal stroke in sub-Riemannian geometry. Geometric analysis combined with numerical simulations are decisive tools to compute the optimal solutions, refining Takagi computations. A family of simple strokes with small amplitudes emanating from a center is characterized as an invariant of SR-geometry and allow to identify the metric used by the swimmer.
MAC, Tel Aviv
Rapport LAAS N°17011, Janvier 2017, 15p.
Time-dependent Lyapunov functionals appeared to be very efficient for sampled-data systems. In , new Lyapunov functionals were constructed for sampled-data control in the presence of a constant input delay. The construction of these functionals was based on Wirtinger's inequality leading to simplified and efficient stability conditions in terms of Linear Matrix Inequalities (LMIs). In the present paper we extend the latter results to the discrete-time sampled-data systems. We show that the proposed approach is less conservative on some examples with a lower number of decision variables.
O.LOPEZ SANTOS, G.GARCIA, L.MARTINEZ SALAMERO, J.C.AVILA MARTINEZ, L.SEGUIER
MAC, URV, Unibague, I2C
Revue Scientifique : International Journal of Control, Vol.90, N°1, pp.90-109, Janvier 2017, doi 10.1080/00207179.2015.1116126 , N° 15294
This paper presents a proposal to control the output stage of a two-stage solar micro-inverter to inject real power into the grid. The input stage of the micro-inverter is used to extract the maximum available power of a photovoltaic module enforcing a power source behavior in the DC-link to feed the output stage. The work here reported is devoted to control a grid-connected Power Source Inverter (PSI) with a high power quality level at the grid side ensuring the power balance of the microinverter regulating the voltage of the DC-link. The proposed control is composed of a sinusoidal current reference generator and a cascade type controller composed by a current tracking loop and a voltage regulation loop. The current reference is obtained using a synchronized generator based on Phase Locked Loop (PLL) which gives the shape, the frequency and phase of the current signal. The amplitude of the reference is obtained from a simple controller regulating the DC-link voltage. The tracking of the current reference is accomplished by means of a first order sliding-mode control law. The solution takes advantage of the rapidity and inherent robustness of the sliding mode current controller allowing a robust behavior in the regulation of the DC-link using a simple linear controller. The analytical expression to determine the power quality indicators of the micro-inverter's output are theoretically solved giving expressions relating the converter parameters. The theoretical approach is validated using simulation and experimental results.
E.B.CHIN, J.B.LASSERRE, N.SUKUMAR
University of Califo, MAC
Rapport LAAS N°17003, doi 10.1002/nme.5436, Janvier 2017
In this paper, we model crack discontinuities in two-dimensional linear elastic continua using the extended nite element method without the need to partition an enriched element into a collection of triangles or quadrilaterals. For crack modeling in the X-FEM, the standard finite element approximation is enriched with a discontinuous function and the near-tip crack functions. Each element that is fully cut by the crack is decomposed into two simple (convex or nonconvex) polygons, whereas the element that contains the crack tip is treated as a nonconvex polygon. On using Euler's homogeneous function theorem and Stokes's theorem to numerically integrate homogeneous functions on convex and nonconvex polygons, the exact contributions to the stiness matrix from discontinuous enriched basis functions are computed. For contributions to the stiness matrix from weakly singular integrals (due to enrichment with asymptotic crack-tip functions), we only require a one-dimensional quadrature rule along the edges of a polygon. Hence, neither element-partitioning on either side of the crack discontinuity nor use of any cubature rule within an enriched element are needed. Structured finite element meshes consisting of rectangular elements, as well as unstructured triangular meshes, are used. We demonstrate the exibility of the approach and its excellent accuracy in stress intensity factor computations for two-dimensional crack problems.
M.CLAEYS, D.HENRION, M.KRUZIK
SABCA, MAC, CzechTech. Univ.
Revue Scientifique : ESAIM: Control, Optimisation and Calculus of Variations, Vol.23, N°1, pp.95-117, Janvier 2017 , N° 14653
Converging hierarchies of finite-dimensional semi-definite relaxations have been proposed for state-constrained optimal control problems featuring oscillation phe-nomena, by relaxing controls as Young measures. These semi-definite relaxations were later on extended to optimal control problems depending linearly on the con-trol input and typically featuring concentration phenomena, interpreting the control as a measure of time with a discrete singular component modeling discontinuities or jumps of the state trajectories. In this contribution, we use measures intro-duced originally by DiPerna and Majda in the partial differential equations litera-ture to model simultaneously, and in a unified framework, possible oscillation and concentration effects of the optimal control policy. We show that hierarchies of semi-definite relaxations can also be constructed to deal numerically with noncon-vex optimal control problems with polynomial vector field and semialgebraic state constraints.