Analyse et commande de systèmes de mesure de courant tunnel

L'objet de la thèse était la commande d'un système de nano-positionnement par couranttunnel, avec application sur la plateforme expérimentale développée au laboratoire Gipsa-lab.Cette thèse s'inscrit dans le cadre de la commande des systèmes micro et nano-mécatronique,pour des applications en microscopie en champ proche ou dans des systèmes depositionnement ultra-précis. A l'échelle nanométrique, des problèmes de bruits de différentesnatures, vibrations, non-linéarités et instabilité influencent la précision et la qualité de mesuredu système. L'objectif était donc de pouvoir faire face à ces contraintes en utilisant destechniques modernes de commande robuste. Dans cette thèse, un système de mesure à couranttunnel a été modélisé et le problème de contrôle lié aux performances de mesure souhaitées aété formulé. Les performances souhaitées, à savoir la précision de la mesure et le rejet decertaines perturbations avec la robustesse adéquate, ont été atteints en utilisant des lois decommande robuste. Ces lois de commande ont été validées expérimentalement (àl'atmosphère ambiante) sur une plateforme du Gipsa-lab. À la fin de cette thèse, pour uneapplication de scanner de surface à l'échelle atomique, une modélisation dynamique MIMOdu système a été proposée et un régulateur MIMO afin de réduire l'erreur de positionnementdûe au couplage a été validé en simulations.The objective of this thesis was to control the nano-positioning system using tunneling current with the real-time validation over an experimental platform developed in Gipsa-lab. This thesis lies in the domain of control for micro and nano-mechatronics systems for the applications of scanning probe microscopy and ultra-precise positioning. At nanometer scale, the problems of noise, vibrations, nonlinearity and instability influence the precision of the measurement. The objective was to deal with these constraints by using the modern techniques of robust control. In this thesis, a system of tunneling current measurement has been modelled and the control problem has been formulated in terms of desired measurement performances. Then, robust control design laws are analyzed in order to achieve better performances in terms of measurement precision and rejection of certain disturbances with robustness. These control laws are experimentally validated (at ambient atmosphere) for a platform of Gipsa-lab. At the end of this thesis, a dynamic modelling of MIMO system for an application of scanning the surface with an atomic resolution has been proposed and a MIMO controller in order to reduce the positioning error due to coupling has been validated in simulations.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Contrôle nanoscopique du mouvement par courant tunnel (étude et réalisation)

Ce doctorat propose l utilisation d un capteur à courant tunnel pour manipuler un objet à dimensions nanoscopiques. L utilisation de ce capteur est motivée par ses propriétés uniques, à savoir sa précision, sa bande passante et le fait qu il puisse être miniaturisé à l échelle du nanomètre. Il peut donc être embarqué. De plus, dans un contexte de nano positionnement, sa mise en oeuvre ne peut se faire sans l application d outils de contrôle. Nous avons démontré que l utilisation du courant tunnel couplé à un actionnement électrostatique répond aux problématiques récentes dans le domaine du nano positionnement (correction de dérives, augmentation conjointe de la rapidité de manipulation et de la précision). Pour cela, une plateforme a été construite au GIPSA-Lab dans le cadre de ce doctorat. Cette plateforme a pour but de permettre le contrôle de déplacements d un micro objet par courant tunnel et actionnement électrostatique. En particulier, cette plateforme a permis le contrôle des déplacements d une micro poutre avec une précision de l ordre de la dizaine de picomètres et sans contact.The present work proposes to use the tunnel current as a sensor to manipulate an object with micrometric dimensions. The use of such a sensor is proposed as an alternative to optical sensors, commonly used to measure or control the position of objects at a micrometric or nanometric scale. This work shows that the tunnel current can be controlled simultaneously with an electrostatic actuator and a piezoelectric actuator to tackle difficulties relative to the reduction of scale, such as drifts or measurement noise. For that purpose, an experimental set-up has been built up at the GIPSA-Lab in the framework of this PhD. A robust control strategy has been implemented in this set-up to control the position of a micro cantilever with an accuracy below the angström at a speed higher than several hundred of Hertz.GRENOBLE1-BU Sciences (384212103) / SudocGRENOBLE-GIPSA-lab (384212301) / SudocSudocFranceF

Robust control design strategies applied to a DVD-video player

GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

On noncontact Atomic Force Microscopy control for interaction force and surface reconstruction

International audienceA control strategy is here investigated in order to improve the measurement performances in Atomic Force Microscopy (AFM), in particular with respect to thermal noise. This strategy is exemplified by an observer-controller scheme for topography detection and interaction force reconstruction. The proposed state feedback and observer designs are based on a simple low order model, but which includes nonlinearities due to interaction forces, as well as the strongly disturbing effects of thermal noise. Some corresponding simulation results are then presented as an illustration of the proposed approach

Observer-based parameter estimation in Liénard systems

International audienceA general excitation condition is provided for parameter identification in so-called Liénard second order nonlinear systems. This condition allows a quite simple observer design for asymptotic state and parameter estimation. Such a condition has already been very recently shown to be satisfied for Van der Pol ocillators, and is further checked here for nonlinear pendulum equations, for which illustrative simulation results are provided

Chaotic excitation-based convergence analysis of an adaptive observer for Lorenz system

International audienceA full convergence analysis is provided for a simple adaptive observer aiming at state and parameter estimation in the famous Lorenz system. This analysis mainly shows that owing to the chaotic nature of the dynamics, the appropriate excitation condition is guaranteed for such a problem. The result is illustrated in simulation

Observer approach for model and force estimation in Scanning Probe Microscopy

ISBN 978-1-4419-9945-

Pull-in control during nanometric positioning by near field position sensing

6 pagesInternational audienceThis paper deals with the pull-in control and the nanopositioning of an electrostatically actuated NEMS (Nano Electromechanical System) squeezed between two forces. It is shown that when a position sensor is driven close to a NEMS, pull-in occurs due to electrostatic forces, but also to near field forces acting at nanoscale, namely Casimir and Van der Waals forces. Pull-in conditions are investigated to find the minimum pull-in distance depending on the parameters of the system. This paper aims to demonstrate that the sensor can be driven below this minimum pull-in distance. To do so, a control strategy based on a nonlinear feedback design and on a robust pole placement/sensitivity function shaping is proposed. Furthermore, it is shown that the NEMS position can be controlled without contact while avoiding pull-in and decreasing its natural brownian motion

Robust H-Infinity Control of a Scanning Tunneling Microscope under Parametric Uncertainties

International audienceThis paper is devoted to the control system design for high performance scanning tunneling microscope (STM). A common approach by scanning probe community is to use conventional proportional integral (PI) control design to control the vertical movement of STM tip (z-direction). In this article, a modern Hinf control design is analyzed in order to obtain the dual purpose of ultrahigh positioning accuracy with high bandwidth. Uncertainty model, based on experimental analysis of tunneling characteristics and parametric description of the STM, and norm-bounded real perturbations are considered, and an Hinf controller is designed by following the desired control objectives. A performance and robustness analysis is finally performed to test robust stability and performance of STM

An observer design for nanoforce estimation with thermal noise attenuation

International audienceThe problem of estimating forces at a very low scale is considered through the example of an electromechanical sensor. The considered dynamical model of the sensor includes the effect of thermal noises generated by the measurement device itself, which are known to be a problem for an accurate measurement at such a scale. A nonlinear observer is proposed as a solution for an appropriate force estimation with noise attenuation. The success of the method is illustrated in a realistic simulation configuration