Commande sans capteur du moteur pas-à-pas à base de modes glissants d'ordre supérieur

International audienceNous proposons une commande robuste du moteur pas-à-pas sans capteur de position ni de vitesse, et ne nécessitant que des mesures des courants et des tensions. Nous présentons dans un premier temps des observateurs basés sur des modes glissants du 2ème ordre estimant la position et la vitesse du rotor, puis nous établissons une loi de commande robuste, elle même basée sur des modes glissants, et faisant intervenir ces estimations. La stabilité des observateurs et de la loi de commande est ensuite traitée. Des résultats obtenus en simulation démontrent l'intérêt et la robustesse de ces méthodes

Sensorless Control of a Stepper Motor Based on Higher Order Sliding Modes

International audienceA robust control for a stepper motor with no position nor velocity sensors and only needing current and voltage measurements is designed. Second order sliding mode based observers are realized to estimate both rotor angular position and velocity. Moreover, a robust control law, which is also based on second order sliding modes and which uses the estimates of the observer, is designed. The stability of the observer based control loop is discussed. The results obtained in simulations indicate the usefulness and the robustness of the method

Adding expert knowledge and exploration in Monte-Carlo Tree Search

International audienceWe present a new exploration term, more efficient than clas- sical UCT-like exploration terms and combining efficiently expert rules, patterns extracted from datasets, All-Moves-As-First values and classi- cal online values. As this improved bandit formula does not solve several important situations (semeais, nakade) in computer Go, we present three other important improvements which are central in the recent progress of our program MoGo: { We show an expert-based improvement of Monte-Carlo simulations for nakade situations; we also emphasize some limitations of this modification. { We show a technique which preserves diversity in the Monte-Carlo simulation, which greatly improves the results in 19x19. { Whereas the UCB-based exploration term is not efficient in MoGo, we show a new exploration term which is highly efficient in MoGo. MoGo recently won a game with handicap 7 against a 9Dan Pro player, Zhou JunXun, winner of the LG Cup 2007, and a game with handicap 6 against a 1Dan pro player, Li-Chen Chien

Relay Control Design using Attractive Ellipsoids Method

International audienceBased on the attractive ellipsoids method the problem of rejection of both matched and mismatched exogenous disturbances is studied for a linear plants controlled by the generalized relays. Some existing results about local stabiliz-ability as well as matching condition are refined for the system under consideration. The procedure of robust control design for optimal rejection of bounded exogenous disturbances is proposed. The theoretical results are supported with numerical simulations

L2-stability criterion for systems with decentralized asynchronous controllers

International audienceThis paper deals with the stability analysis of decentralized sampled-data Linear Time Invariant (LTI) control systems with asynchronous sensors and actuators. We consider the case where each controller in the decentralized setting has its own sampling and actuation frequency which translates to asynchrony between sensors and actuators. The errors induced due to sampling and asynchronicity are modelled using two different operator approaches, leading to simple L2-stability criteria for the overall decentralized control system. The simplicity of the obtained criteria is illustrated by an example and simulation results exhibit the effectiveness of the approach

Stabilization by a relay control using non-quadratic Lyapunov functions

International audienceIn this article we consider the stabilization problem by a relay control using non-quadratic Lyapunov functions. First, a general result is proposed for the case of nonlinear systems. A full state relay feedback controller is designed in order to ensure the local asymptotic stability of the closed-loop system. Then, the result is applied to the particular case of LTI systems. A constructive method based on LMI conditions is given in order to design nonlinear switching surfaces and provide an estimation of a non-ellipsoidal domain of attraction. In addition, the approach is extended to observer-based relay feedback. Both linear and nonlinear switching surfaces dependent on the estimated state are designed while using a Luenberger observer. Finally, illustrative examples are proposed in order to show the efficiency of the proposed methods and simulations are performed for a Buck converter structure

Echantillonnage dépendant de l'état : une approche discrète

International audienceCe travail concerne l'adaptation des instants d'échantillonnage pour des systèmes différentiels linéaires stationnaires contrôlés par retour d'état. De façon complémentaire à de nombreux travaux qui garantissent la stabilisation indépendamment des variations de la cadence d'échantillonnage, il s'agit ici de concevoir des séquences d'instants d'échantillonnage stabilisantes. Ici, on adapte dynamiquement les ressources nécessaires au calcul des lois de commande en agissant sur leurs instants d'échantillonnage qui ne sont plus périodiques. La solution proposée détermine une séquence d'échantillonnage en fonction de la valeur mesurée de l'état. On développe un algorithme d'ordonnancement dynamique optimisant, sur un horizon d'échantillonnage donné, une séquence parmi un ensemble discret de solutions. Nos preuves sont inspirées des techniques de systèmes hybrides à commutations, alliant fonctions de Lyapunov et optimisation LMI. L'étude théorique est ensuite illustrée par une implémentation algorithmique sous Matlab/TRUETIME simulant l'interaction commande/ordonnancement

A Robust Polytopic Approach for State-Dependent Sampling

International audienceThis work aims at decreasing the number of sampling instants in state feedback control for perturbed linear time invariant systems. The approach is based on linear matrix inequalities obtained thanks to Lyapunov-Razumikhin stability conditions and convexification arguments that guarantee the exponential stability for a chosen decay-rate. First, the method enables to perform a robust stability analysis regarding time-varying sampling and to maximize a lower-bound estimate of the maximal allowable sampling interval, by computing the adequate Lyapunov-Razumikhin function. Then, it makes it possible to design a state-dependent sampling control scheme that enlarges even further the maximal allowable sampling intervals

State-Dependent Sampling for Perturbed Time-Delay Systems

International audienceIn this work we present a state-dependent sampling control that allows for enlarging the sampling intervals of state-feedback control. We consider the case of perturbed linear time-invariant systems with input-delay and guarantee their L2-stability. The approach is based on a novel class of switched Lyapunov-Krasovskii functionals with state-dependent matrices. It results in an LMI problem that allows for enlarging the sampling interval according to the system state. Then, a mapping of the state space is designed offline: it computes for each state of the state space a lower-bound estimation of the maximum allowable sampling interval, which makes it possible to reduce the number of actuations during the real-time control of the system

State dependent sampling: an LMI based mapping approach

International audienceThe uprising use of embedded systems and Networked Control Systems (NCS) requires reductions of the use of processor and network loads. In this work, we present a state dependent sampling control that maximizes the sampling intervals of state feedback control. We consider linear time invariant systems and guarantee the exponential stability of the system origin for a chosen decay rate alpha. The proof of the alpha-stability is based on a quadratic Lyapunov function which is computed, thanks to LMIs, so as to optimize some performance criterion on the sampling intervals. A mapping of the state space is then designed offline: it computes for each state of the state space the maximum allowable sampling interval, which makes it possible to reduce the number of actuations during the real-time control of the system