Modelling of a MEMS-based microgripper : application to dexterous micromanipulation.

International audienceMEMS-based microgrippers with integrated force sensor have proved their efficiency to perform dexterous micromanipulation tasks through gripping forces sensing and control. For force control, knowledge based models are more relevant and gives better physical significance than the use of black box models. However this approach is often limited by many problems commonly encountered in the MEMS (micro electromechanical systems) structures such as: complex architectures, nonlinear behaviors and parameters uncertainties due to fabrication process at the micrometer scale. For these reasons theoretical approaches must be compared with experiments. This paper describes a modelling approach of a MEMS-based microgripper with integrated force sensor while handling micro-glass balls of 80μm diameter. Therefore, a state space representation is developed to couple both the dynamics of the actuation and sensing subsystems of the gripper through the stiffness of the manipulated object. A knowledge based model is obtained for small displacements at the tip of the gripper arms (small gripping forces) and is compared with experimental approaches. Good agreements are observed allowing interesting perspectives for the control

Gain scheduled control strategies for a nonlinear electrostatic microgripper: Design and real time implementation

International audienceThis paper deals with the accurate and fast positioning control of a nonlinear electrostatically actuated microgripper. Considering the importance of nonlinearities, performances are achieved through the design of gain scheduled controllers. To this end, a nonlinear model of the studied system is proposed and is reformulated into a polynomial LPV (Linear Parameter Varying) model. Controllers are designed considering the particular polynomial parametric dependence of the LPV model. In a first instance, a controller is synthesized using an affine LPV descriptor representation of the system and LMI (Linear Matrix Inequality) constraints. In a second instance, to deal with real time implementation constraints, a second controller is designed based on an iterative procedure using the eigenstructure assignment methodology and a worst case analysis. For embedded applications, requiring simplecontroller structures, we show experimentally the interest of the iterative procedure which can achieve good results relatively with the ones obtained using recent advances of robust controllers based on LMI conditions

Microrobotique et Micromécatronique pour la Réalisation de Tâches de Micro-Assemblage Complexes et Précises.

Ce document présente une synthèse de mes contributions scientifiques aux domaines de la microrobotique et de la micromécatronique ainsi que des transferts effectués, tant à destination de l’industrie que de l’enseignement. Les travaux conduits sont orientés vers la réalisation de tâches de micro-assemblage complexes, précises et automatisées par approche microrobotique et sont plus particulièrement appliqués aux MOEMS.L’échelle micrométrique considérée induit de nombreuses spécificités qui se traduisent par un déficit notable de connaissances du comportement des systèmes à cette échelle. Pour cela, une première partie des travaux est dédiée à l’étude et à la modélisation multiphysique des systèmes microrobotiques et micromécatroniques. Cette connaissance a conduit, dans une seconde partie des travaux, à la proposition de nouveaux principes de mesure et d’actionnement mais également au développement de microsystèmes complexes, instrumentés et intégrés (micro-banc-optique, micropince, plateformes compliantes). Enfin, des lois de commandes et des stratégies d’assemblage originales ont été proposées notamment une commande dynamique hybride force-position combinant une commande hybride externe et une commande en impédance. Celle-ci permet de maîtriser la dynamique des transitions contact/non-contact critique à l’échelle micrométrique mais également d’automatiser des processus de micro-assemblage complexes. L’ensemble de ces travaux ont fait l’objet de validations expérimentales permettant de quantifier précisément les performances obtenues (exactitude de positionnement, temps de cycle, robustesse…). Les perspectives de ces travaux portent sur la proposition de systèmes microrobotiques et micromécatroniques compacts et intégrés utiles au micro-assemblage haute dynamique ainsi qu’à l’assemblage de composants nanophotoniques

Vision guided automation for intra-cytoplasmic sperm injection

Biological cell injection is an effective technique in which a foreign material is directly introduced into the target cell. Intracytoplasmic Sperm Injection (ICSI) is a microinjection technique which is used for infertility treatment. In this technique, a single sperm cell is directly injected into an oocyte using micropipettes. The operations in this application are manually controlled by an embryologist and more importantly, this reduces the accuracy, repeatability, and consistency of the operation. Therefore, the full automation is a prerequisite for microinjection operations, particularly in ICSI application. This thesis focuses on enhancing the microinjection procedure by developing vision-guided processes prior to and during the operation. Initially, a vision-controlled technique was proposed to align the injection and holding pipettes in three orthogonal axes which is essential for successful microinjection. To conduct reliable injection, the vibrational displacement of the injection pipette’s tip needs to be evaluated and improved before the operations continue further. A novel vision-based sensor was developed to measure the displacement changes at the tip in three orthogonal axes. By employing the developed vision sensor, the effect of injection speed on vibrational displacement creation was analysed to determine the value of various injection parameters, such as force fluctuation, and penetration force on cell damages. An ultimate automation task is required in microinjection to position the randomly located biological cell within the Petri dish to the system’s field of view. The proposed technique fills a gap in the literature by proposing a real-time cell recognising and positioning system that can be employed with different types of biological cells at various maturation stages, as well as with different microscope types that are being used in microinjection applications