Gramian-based optimal design of a dynamic stroke amplifier compliant micro-mechanism.

International audienceThis paper presents a new method developed for the optimal design of microrobotic compliant mechanisms. It is based on a flexible building block method, called FlexIn, which uses an evolutionary approach, to optimize a truss-like structure made of building blocks. From the first design step, in addition to conventional mechanical criteria, dynamic gramian-based metrics can be considered in the optimization procedure to fit expected frequency responses of the synthetized mechanisms. A planar monolithic compliant coupling structure is obtained by the optimal design method to act as a stroke amplifier for piezoelectric stacked actuators, to operate in both static and dynamic motions, and to passively filter out undesirable vibrations. Finally, performance comparisons between some of the pseudo-optimal FlexIn synthetized compliant mechanisms demonstrate the interests of the proposed optimization method for the design of dynamic operating smart microrobotic structures

Redesign of the MMOC microgripper piezoactuator using a new topological optimization method.

International audienceThis paper presents a new method developed for the optimal design of piezoactive compliant mechanisms. It is based on a flexible building blocks method, called FlexIn, which uses an evolutionary approach, to optimize a truss-like structure made of passive and active piezoelectric building blocks. An electromechanical approach, based on a mixed finite element method, is used to establish the model of the piezoelectric blocks. A planar monolithic compliant microactuator is synthetized by the optimization method, based on the specifications drawn from a piezoelectric microgripper prototype (MMOC). Finally, some performances comparisons between the optimally FlexIn synthetized gripper and the previous gripping system demonstrate the interests of the proposed optimization method for the design of microactuators, microrobots, and more generally for adaptronic structrures

Potentialities of optimal design methods and associated numerical tools for the development of new micro- and nanointelligent systems based on structural compliance - An example -

11 pagesInternational audienceThis paper deals with the interest and potential use of intelligent structures mainly based on compliant mechanisms (and optionally including smart materials), for the development of new micro- and nano-robotics devices. The state of the art in optimal design methods for the synthesis of intelligent compliant structures is briefly done. Then, we present the optimal method developed at CEA LIST, called FlexIn, and its new and still in development functionalities, which will be illustrated by a few simple design examples. An opening will be given about the possibility to address the field of Nanorobotics, while adding functionalities to the optimal design method

Modeling and robust control strategy for a control-optimized piezoelectric microgripper.

International audienceIn this paper, modeling and robust control strategy for a new control-optimized piezoelectric microgripper are presented. The device to be controlled is a piezoelectric flexible mechanism dedicated to micromanipulation. It has been previously designed with an emphasis to control strategy, using a new topological optimization method, by considering innovative frequency-based criteria. A complete non-linear model relating the voltage and the resulting deflection is established taking into account hysteresis as a plurilinear model subjected to uncertainties. The approach used for controlling the actuator tip is based on a mixed High Authority Control (HAC) / Low Authority Control (LAC) strategy for designing a wide-band regulator. It consists of a Positive Position Feedback (PPF) damping controller approach combined with a low-frequency integral controller which is shown to have robustness performances as good as a RST-based robust pole placement approach for the microgripper. The rejection of the vibrations, naturally induced by the flexible structure, and the control of the tip displacement have been successfully performed. Because we had taken into account frequency-based criteria from the first designing step of our device, we demonstrate that the tuning of the HAC/LAC can be easily performed and leads to low regulator order

Mechanical and control-oriented design of a monolithic piezoelectric microgripper using a new topological optimisation method.

International audienceThis paper presents a new method developed for the optimal design of piezoactive compliant micromechanisms. It is based on a flexible building block method, called FlexIn, which uses an evolutionary approach, to optimize a truss-like planar structure made of passive and active building blocks, made of piezoelectric material. An electromechanical approach, based on a mixed finite element formulation, is used to establish the model of the active piezoelectric blocks. From the first design step, in addition to conventional mechanical criteria, innovative control-based metrics can be considered in the optimization procedure to fit the open-loop frequency response of the synthetized mechanisms. In particular, these criteria have been drawn here to optimize modal controllability and observability of the system, which is particularly interesting when considering control of flexible structures. Then, a planar monolithic compliant micro-actuator has been synthetized using FlexIn and prototyped. Finally, simulations and experimental tests of the FlexIn optimally synthetized device demonstrate the interests of the proposed optimization method for the design of micro-actuators, microrobots, and more generally for adaptronic structures

Synthèse et commande robuste d'une micropince piézoélectrique intégrée.

National audienceWe have developed a new method to make the synthesis of monolithic flexible structures for designing integrated actuators. Our synthesis method is based on the optimal placement of building blocks. These elementary blocks can be made in passive materials or in active piezoelectric ceramics. Thanks to a dynamic representation of the input/output behavior of these mechanisms, some new specifications which can guaranty interesting performances for the identification and control of these systems are taken into account, from the first designing step. These last criteria helped us to draw an original design strategy for their robust control. MOTS-CLÉS : structure flexible, piézoélectricité, optimisation topologique multi-critères, grammiens, commandabilité, observabilité

Comparative Review of Endoscopic Devices Articulations Technologies Developed for Minimally Invasive Medical Procedures

This study introduces a comparative performance analysis of the technological solutions that have been used to build distal active articulations for minimally invasive medical procedures. The aim is to provide a practical and concise database and classification tool for anyone that wants to learn more about the technologies involved in minimally invasive medical devices, or for any designer interested in further improving these devices. A review of the different articulations developed in this field is therefore performed and organized by both actuation technology and structural architecture. Details are presented concerning the mechanical structures as well as the actuation and the mechanical transmission technologies available. The solutions are evaluated keeping as a reference some chosen required performances and characteristics for minimally invasive surgical procedures. Finally, a quantified comparison chart of these devices is given regarding selected criteria of interest for minimally invasive surgical application

Méthode des blocs sensitifs pour la synthèse optimale de mécanismes flexibles à mesure piézoélectrique intégrée.

National audienceCet article présente une méthode de synthèse optimale pour la conception préliminaire de mécanismes flexibles monolithiques piézoélectriques. La construction d'un tel mécanisme, selon cette méthode baptisée FlexIn, est basée sur l'agencement de blocs flexibles piézoélectriques élémentaires qui peuvent être structurels, actionneurs et/ou capteurs, sélectionnés respectivement dans trois bibliothèques. Cet article décrit plus particulièrement l'approche utilisée pour établir le modèle aux éléments finis multi-physiques des blocs capteurs piézoélectriques, de type treillis de poutre, en vue de son intégration dans le logiciel de synthèse optimale. Les résultats obtenus présentent un écart de quelques pourcents avec ceux issus d'un code aux éléments finis commercial. A titre d'exemple, le modèle capteur est appliqué à une micropince monolithique existante ; le résultat de mesure est d'un ordre de grandeur satisfaisant. Ces résultats permettent de dresser les perspectives de la méthode de synthèse optimale proposée dans le cadre général de la conception de structures intelligentes pour la microrobotique

Etude et réalisation d'un module de locomotion pour microrobot d'inspection intratubulaire. Actionnement par fils AMF d'un cadre forcé en post-flambement à deux états d'équilibre stable

The work presented here constitutes an outline of the various studies necessary to develop a new autonomous in-tube exploration microrobot. Constituted by five identical locomotion modules, the future microrobot shall inspect networks of industrial tubes, of diameter lower than 15 mm, and presenting bends and forks. Judicious actuation of the various modules will allow its progression inside the tube, with the manner of the earth-worm. Our efforts focused on the study, the manufacture and the development of the locomotion module, while seeking to optimize the parameter 'displacement speed' of the future microrobot. This actuator, of original design, is constituted by a postbuckled frame, presenting two states of stable equilibrium, and whose rock up from one state to the other is controlled by shape memory alloy wires (SMA). A theoretical study of the equilibrium state and a simplified static model using the finite elements method, taking into account large postbuckling displacements, during the loading driving to the rock, helped us to size the frame and to choose the material. Then, mechanical characterization tests carried out on a higher scale prototype of the module, were necessary to adjust educated SMA wires. Joule effect being the means of heating which was retained to generate the shortening of these wires, we evoke some aspects related to the module control, and to the checking of SMA transformation by the measurement of their electric resistance. Lastly, an experimental study of the contact behavior of one module allows us to evaluate the influence of various parameters on the support conditions of the robot inside a vertical tube. We then deduce the possibilities of embarked load by the future microrobot, in the purpose to fit it with sensors and electric power generators necessary to its autonomy.Le travail présenté dans ce mémoire constitue une ébauche des différentes études nécessaires au développement d'un microrobot d'exploration intratubulaire autonome inédit. Constitué d'un assemblage de cinq modules locomoteurs identiques, le futur microrobot devra inspecter des réseaux de tubes industriels de diamètre inférieur à 15 mm, présentant des coudes et des bifurcations. L'actionnement judicieux des différents modules permettra sa progression dans le tube, à la manière du lombric. Nos efforts se sont portés sur l'étude, la fabrication et la mise au point du module locomoteur, en cherchant à optimiser le paramètre 'vitesse de déplacement' du futur microrobot. Cet actionneur, de conception originale, est constitué d'un cadre forcé en postflambement, à deux états d'équilibre stable, dont le basculement d'un état à l'autre est commandé par des fils en Alliage à Mémoire de Forme (AMF). Une étude théorique à l'état d'équilibre, puis un modèle statique simplifié aux éléments finis, prenant en compte les grands déplacements de post-flambement lors du chargement menant au basculement, ont facilité le dimensionnement du cadre et le choix du matériau. Ensuite, des tests de caractérisation mécanique réalisés sur un prototype du module, à une échelle supérieure, ont été nécessaires pour l'adaptation de fils AMF éduqués. L'effet Joule étant le moyen de chauffage qui a été retenu pour engendrer la contraction de ces fils, nous évoquons quelques aspects liés à la commande d'un module, et au contrôle de la transformation des AMF par la mesure de leur résistance électrique. Enfin, une étude expérimentale du comportement au contact d'un module nous permet d'évaluer l'influence de différents paramètres sur les conditions de maintien du robot dans un tube vertical. Nous en déduisons alors les possibilités de charge embarquée par le futur microrobot, dans l'optique de le munir de capteurs et de sources d'énergie nécessaires à son autonomie

Outil d'aide à la conception de structures flexibles à actionnement intégré pour la microrobotique.

National audienceDans le cadre de la microrobotique, une méthode de synthèse optimale a été développée pour la conception de structures à déformations et actionnement répartis. Les mécanismes compliants sont décrits par l'assemblage de sous-structures élémentaires appelés "blocs" (voir figure), considérant la répartition de matériaux actifs piézoélectriques sous forme distribuée pour l'actionnement. Les paramètres optimaux définissant totalement les structures sont déterminés par un algorithme génétique multicritères, dont la plupart des fonctions objectif sont obtenues par la méthode des éléments finis. Outre des critères purement mécaniques, la liste des critères d'optimisation disponibles est complétée par des critères liés à la commande des systèmes pour placer, par exemple, de manière optimale les blocs actifs d'actionnement, et ultérieurement de mesure, dans la structure (maximisation de la commandabilité de la partie effectrice et maximisation de l'observabilité mécanique externe)