Commande robuste d'une pince microfabriquée à actionnement électrostatique.

International audienceL'élaboration des lois de commande pour les MEMS se heurte à de nombreuses difficultés liées à la forte miniaturisation. Ces systèmes sont très sensibles aux conditions envrionnementales (températeur, humidité, etc...) ainsi qu'aux perturbations. Les rapports signal/bruit sont très défavorables en raison des très faibles amplitudes des signaux utiles. L'intégration de capteurs est rendue difficile par une accessibilité souvent limitée ou par l'inexistence de capteurs de faibles dimensions. Tous ces éléments font que les MEMS constituent un champ exploratoire et applicatif nouveau pour l'automatique. Dans cet article, nous présentons la synthèse d'une loi de commande robuste fondée sur la méthode H pour l'asservissement de la position de l'extrémité d'une pince microfabriquée sur un substrat de silicium. L'incertitude de modélisation ainsi que l'effet du bruit de mesure ont été pris en compte lors de la synthèse

Une étude sur les spécificités de la commande dans le micromonde.

National audienceThe development of micro and nanotechnologies requires the design of microrobots and Microsystems able to handle submillimetric objects. Many micromanipulation systems have been built. However, improvement of the performances requires the use of advanced control methods. In this paper, we present the main characteristics of the microworld from a control point of view and some control strategies adapted to the microsystems

Voltage/frequency proportional control of stick-slip micropositioning systems.

International audienceA new control type for stick-slip micropositioning system is proposed in this paper : the voltage/frequency (U/f) proportional control. It gives more precise results relatively to the classical control algorithm. It is also an assembly of two classical controllers : the sign and the classical proportional controllers. A high stroke model of a stick-slip micropositioning system is first given. Then, we will theoretically analyse the performances of the closed loop process with the U/f controller. Finally, we will give some experimental results obtained with different values of the proportional gains

Plurilinear Modeling and discrete μ-Synthesis Control of a Hysteretic and Creeped Unimorph Piezoelectric Cantilever.

International audienceFirst, we present a survey on modeling and control of bending piezoelectric microactuators. Second, a simple model for nonlinear piezoelectric actuators (hysteresis and creep) is presented. It is based on the multilinear approximation. This model requires low computing power and is well adapted for embedded systems. Finally, a μ-synthesis controller is implemented. Experiments show that the obtained performances are compatible with the requirements of micromanipulation tasks

Design, development and experiments of a high stroke-precision 2DoF (linear-angular) microsystem

International audienceThis paper presents the design, the development and the experiments on a two degrees of freedom (2DoF) microsystem. The originality of the microsystem is its ability to do angular and linear motions independently with a very high stroke and a submicrometric precision. The target performances are first presented. Afterwards the stick-slip piezoelectric microactuators that are used are presented. Then, their integration inside the microsystem is detailed. Finally, results of experiments are given

Nonlinear modeling and estimation of force in a piezoelectric cantilever.

International audienceThis paper deals with the estimation of force in a piezoelectric cantilever. The nonlinearities, i.e. hysteresis and creep, are taken into account. A nonlinear model relating the force, the voltage and the resultant deflection is first developped. The proposed estimator has been experimented and compared with the classical linear estimator. The results confirm the interest of the proposed method in term of accuracy

Characterization and control of a monolithically fabricated bistable module for microrobotic applications.

International audienceMicrorobots are widely used for microassembly and micromanipulation. However achieving performances compatible with the work in the microworld requires the use of bulky and expensive systems for measurement, signal processing and real time control. In this paper, we present the characterization and the control of a bistable module that can be used to build microrobots. This bistable module is fabricated monolithically using microfabrication technology. It offers two stable and blocked positions. High resolutions can be reached using this approach. Static and dynamic characteristics of the bistable module are studied and an open-loop control strategy is proposed in order to switch smoothly from one position to the other. The presented bistable module is the basic module for building digital microrobots

Quadrilateral modelling and robust control of a nonlinear piezoelectric cantilever.

International audiencePiezocantilevers are commonly used for the actuation of micromechatronic systems. These systems are generally used to perform micromanipulation tasks which require high positioning accuracy. However, the nonlinearities, i.e. the hysteresis and the creep, of piezoelectric materials and the influence of the environment (vibrations, temperature change, etc.) create difficulties for such a performance to be achieved. Various models have been used to take into account the nonlinearities but they are often complex. In this paper, we study a one degree of freedom piezoelectric cantilever. For that, we propose a simple new model where the hysteresis curve is approximated by a quadrilateral and the creep is considered to be a disturbance. To facilitate the modelling, we first demonstrate that the dynamic hysteresis of the piezocantilever is equivalent to a static hysteresis, i.e. a varying gain, in series with a linear dynamic part. The obtained model is used to synthesize a linear robust controller, making it possible to achieve the performances required in micromanipulation tasks. The experimental results show the relevance of the combination of the developed model and the synthesized robust H∞ controller

TRING-module : a high-range and high-precision 2DoF microsystem dedicated to a modular micromanipulation station.

International audienceAs part of a microfactory concept, a micromanipulation station is made up of two independant microsystems having each one two degrees of freedom (rotation and linear motions). That allows the station to manipulate microparts with a high range of dimensions, from 10 microns to some millimeters (2 mm). This paper presents one of these microsystems called TRING-module

Development, modelling and control of a micro/nano positioning 2DoF stick-slip device.

International audienceThe works presented in this article are motivated by the high performances required in micromanipulation/ microassembly tasks. For that, this paper presents the developement, the modelling and the control of a 2 degrees of freedom (in linear and angular motion) micropositioning device. Based on the stick-slip motion principle, the device is characterized by unlimited strokes and submicrometric resolutions. First, experiments were carried out to characterize the performances of the micropositioning device in resolution and in speed. After that, a state-space model was developed for the sub-step functioning. Such functioning is interesting for a highly accurate task like nanopositioning. The model is validated experimentally. Finally, a controller was designed and applied to the micropositioning device. The results show good robustness margins and a response time of the closed-loop system