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Soft actuators can be classified into five categories: tendon-driven actuators, electroactive polymers, shape-memory materials, soft fluidic actuators (SFAs), and hybrid actuators. The characteristics and potential challenges of each class are explained at the beginning of this review. Furthermore, recent advances especially focusing on SFAs are illustrated. There are already some impressive SFA designs to be found in the literature, constituting a fundamental basis for design and inspiration. The goal of this review is to address the latest innovative designs for SFAs and their challenges and improvements with respect to previous generations, and to help researchers to select appropriate materials for their application. We suggest seven influential designs: pneumatic artificial muscle, PneuNet, continuum arm, universal granular gripper, origami soft structure, vacuum-actuated muscle-inspired pneumatic, and hydraulically amplified self-healing electrostatic. The hybrid design of SFAs for improved functionality and shape controllability is also considered. Modeling SFAs, based on previous research, can be classified into three main groups: analytical methods, numerical methods, and model-free methods. We demonstrate the latest advances and potential challenges in each category. Regarding the fact that the performance of soft actuators is dependent on material selection, we then focus on the behaviors and mechanical properties of the various types of silicone that can be found in the SFA literature. For a better comparison of the different constitutive models of silicone materials proposed and tested in the literature, ABAQUS software is here employed to generate the engineering and true strain-stress data from the constitutive models, and compare them with standard uniaxial tensile test data based on ASTM412. Although the figures presented show that in a small range of stress–strain data, most of these models can predict the material model acceptably, few of them predict it accurately for large strain-stress values. Sensor technology integrated into SFAs is also being developed, and has the potential to increase controllability and observability by detecting a wide variety of data such as curvature, tactile contacts, produced force, and pressure values.

There is a growing body of evidences that brain surrogates will be of great interest for researchers and physicians in the medical field. They are currently mainly used for education and training purposes or to verify the appropriate functionality of medical devices. Depending on the purpose, a variety of materials have been used with specific and accurate mechanical and biophysical properties, More recently they have been used to assess the biocompatibility of implantable devices, but they are still not validated to study the migration of leaching components from devices. This minireview shows the large diversity of approaches and uses of brain phantoms, which converge punctually. All these phantoms are complementary to numeric models, which benefit, reciprocally, of their respective advances. It also suggests avenues of research for the analysis of leaching components from implantable devices.

In this article we define the criteria and present the methodology to choose a smart material in order to actuate a soft neurosurgery robot. These criteria are defined with the experience of a neurosurgeon.

In this article, we introduce a new soft finger with a pneumatic-actuated movable joint that is optimized and characterized in terms of the degrees of freedom (DoF), workspace, and fingertip force. The finger consists of one soft link as the body and the bending pneumatic joint as the actuator. Due to the additional translation and rotation movement capabilities of the joint, carried out by two stepper motors, the finger can bend in any direction while having different lengths, thanks to a configurable bending point. This results in more dexterity for the finger when dealing with a target inside its 3D workspace by increasing the number of configurations it can use to reach the target and exert force. The finite element method (FEM) and the Nondominated Sorting Genetic Algorithm II (NSGA-II) algorithm are applied to optimize the joint geometry and so maximize the bending angle and minimize the joint dimensions. Furthermore, the variations of each design parameter and consequent effects on the optimization objectives are analyzed. The optimal geometrical parameters are used to fabricate a prototype with silicone rubber. Tests on the bending angle and tip force variability are conducted on the prototype to validate the numerical modeling. The experimental results show that the finger exerts force up to 650 mN with a response time of fewer than 3 s. The stiffness of the finger can be changed by applying pneumatic pressure in the hollow space inside the link. This consequently varies the amount of applied force at the tipping point of the finger up to two times.

International audience; This paper deals with the specific hysteretic effects of a multi-antagonistic shapememory alloy (SMA) actuation system in which each wire can be thermally activated individually (one or more at a time). A planar system with six SMA wires organized in a ternary rotational symmetry is studied numerically, via finite element calculation software. The objective is to analyze the functional characteristics of such mechanism, whose response during a thermal activation sequence is multi-antagonistic and hysteretic. Important points are highlighted, such as the avoidance of buckling and plasticity, the possibility of locking a configuration without energy input, and the "attraction" effect of any heating step on the following steps. The feasibility of reaching a given target in the workspace is also illustrated. Finally, the analysis shows the necessity to consider these multi-antagonistic and hysteretic aspects of the actuation in the future design and control of such type of mechanisms. The latter could be of interest as hollow shaft rotary actuators with additional (small) translation degrees of freedom in applications requiring long-term and stable positioning at ambient temperature.

In robotics, static stiffness maps are used as tools for the performance analysis of robots employed in production tasks, such as pick-and-place or manufacturing. This paper evaluates the relevance of a numerical tool built from a commercial finite element package to generate stiffness maps for any type of robot (serial, parallel, hybrid or compliant). The key points are the spatial resolution, the precision, and the calculation time of a stiffness map. The method for obtaining the 36 static stiffness maps of a 3-D robotic structure in its operational space is presented. The mechanical model is based on a finite element calculation using beam elements for the links and spring elements for the joints. The approach is first applied to a rigid-body mechanism. Numerical results show that a good compromise can be obtained between spatial resolution, precision, and calculation time. Then, the method is applied to a compliant structure requiring processing in a large displacement framework for the relevant estimation of a stiffness map. The numerical tool opens new prospects for the design of robotic structures, in terms of both optimization and use of various material behaviors.

A plane strain problem for an interface electrically charged thin electrode in a bimaterial piezoelectric space is considered. Remote in-plane mechanical loading and an electrical field parallel to the electrode faces are applied. The known solution of this problem demonstrates the electromechanical field singularities at the electrode tips. To remove these singularities the dielectric breakdown model is applied. Using the presentations of electromechanical quantities via sectional analytic functions the Riemann-Hilbert problem with discontinuous right side is formulated and solved exactly. The dielectric breakdown zone lengths are found from the electric field finiteness at the end points of these zones. It is shown that this length depends on the external electric field and the electrode net charge. The variations of electromechanical characteristics along the electrode and its continuation are presented in graphical form. Particular cases of an uncharged electrode and homogeneous material are considered and compared with previously obtained results. A verification of the obtained solutions by means of the ABAQUS code is carried out and good agreement of analytical and numerical results is revealed.

Although the wheeled locomotion proved to be very efficient on smooth grounds, it still encounters great difficulties in natural environments, where the ground is subject to wide variations in term of geometry (irregular surface, presence of obstacles...) and material properties (cohesion, grip condition...). This chapter presents recent developments and original systems that improve the capacities of wheeled mobile service robots on natural ground. First is considered the case of low speed motion. Section 2 presents recent results on reconfigurable suspensions that have two states and can decrease lateral friction and energy consumption during turns for skid-steering vehicles. Section 3 presents an original hybrid kinematics that combines wheels with an articulated frame for creating a mobile-wheeled robot with high obstacle-climbing capacities, using only one supplemental actuator. Other advances deal with high-speed motion. Section 4 describes a new device dedicated to vehicle dynamic stability, which improves lateral stability on fast mobile robots during turns and contributes to rollover prevention. Finally, Section 5 introduces innovative suspensions with two DOF for fast obstacle crossing. They damp vertical shocks, such as ordinary suspensions, but also horizontal ones, contributing to tip-over prevention on irregular grounds that feature many steep obstacles.

OBJECTIVES: This study sought to assess the hemodynamic and cardiac effects of two dose levels of mibefradil in patients with varying degrees of ischemic left ventricular dysfunction. BACKGROUND: Mibefradil is a new, selective T-type and L-type calcium channel blocking agent. Because L-type channel blockade may depress myocardial performance, an invasive hemodynamic study was performed to assess the safety of this agent. METHODS: We performed an open label study, examining the effects of two intravenous doses of mibefradil, selected to produce plasma levels comparable to those measured after oral administration of 50 mg (dose 1: 400 ng/ml) or 100 mg (dose 2: 800 ng/ml) of the drug. Variables studied included the indexes of left ventricular function and neurohormone levels. Patients were stratified according to ejection fraction (EF) (> or = 40%, n = 26; < 40%, n = 24) and the presence (n = 15) or absence (n = 35) of heart failure. RESULTS: In patients with preserved systolic function, dose 1 had no clinically significant hemodynamic effects, but dose 2 decreased mean aortic pressure and systemic vascular resistance (-8.5 mm Hg, -12%, both p < 0.01) and also reduced end-systolic stress and volume, thus improving EF (52% to 58%, p < 0.01). Heart rate tended to decrease. In patients with depressed EF, heart rate decreased significantly with both doses. The effects of dose 1 mimicked those observed after dose 2 in patients with preserved EF. Dose 2 (plasma levels 1,052 +/- 284 ng/ml) still decreased left ventricular systolic wall stress and improved EF (24.0% to 28.5%, p < 0.05) but also significantly depressed the maximal first derivative of left ventricular pressure. Examination of individual pressure-volume loops in two patients with heart failure showed a clear rightward shift of the loop despite a decrease in systolic pressure, suggesting negative inotropy. Neurohormone levels were unchanged at both dose levels and in all subgroups. CONCLUSIONS: Intravenous mibefradil was well tolerated and produced an overall favorable cardiovascular response. However, high plasma concentrations might produce myocardial depression in patients with heart failure, and caution should be exerted in this setting.

This document is a multiple-article format dissertation investigating the design, optimization, and fabrication of soft pneumatic actuators (SFAs) for soft robotic applications. Introduced as a novel technology in recent years, soft robotics broadens new horizons in robotics thanks to promising characteristics such as adaptability, lightweight, less assembly, and low cost to perform complicated configurations in various environments. Even though there is a large diversity of applications for SFAs, many challenges remain in this field, including stiffness and bending shape control. To illustrate the current methodological and theoretical applications of soft robotic systems, the first article presents a systematic review of soft fluidic actuators that tried to address the critical challenges in soft and active materials, processing methods, gripper architectures, sensors, and control methods. Different constitutive models of silicone materials proposed and tested in the literature are regenerated by ABAQUS software to compare the engineering and true strain-stress data from the constitutive models with standard uniaxial tensile test data based on ASTM412. This paper shows that most of these models can predict the material model acceptably in a small range of stress-strain data. But for large strain-stress values, a few of them predict the behavior of the silicone material accurately. The second article presents a novel type of soft finger with a pneumatic-actuated movable joint based on bending point control and variable stiffness. The proposed finger is more flexible than previous solutions in terms of the attainable 3D space and applicable contact forces at the fingertip by changing the position of its joint, and thus, the bending point. The finite element method (FEM) and NSGA-II algorithm are applied to optimize the joint geometry to maximize the bending angle and minimize the joint dimensions. The third article in this dissertation is focused on developing a new type of dexterous soft gripper with three reconfigurable fingers and an active palm enhancing in-hand manipulation capabilities. In each finger, the bending point and the effective manipulation length can be changed and controlled by moving a stiff rod inserted inside the center hole of the finger. The in-hand manipulation capability of this soft robotic gripper is validated by different experimental tests, including rotation, regrasping, and rolling. Therefore, two types of vacuum palms (suction cup and granular particles) are utilized to guarantee a wide range of object manipulation tasks that previously suggested soft grippers cannot completely perform. In the final chapter of this dissertation, the fourth article proposed a low-cost, easy fabrication tactile sensor for soft robot application. It is very flexible and easy use which make it an appropriate choice for soft robot application. Most of the materials (conductive ink, silicone, control board) used in the fabrication of this sensor are inexpensive and can be found easily in the market. The proposed capacitive sensor can detect the position and applied force by measuring the electric charge of the electrodes. Due to the uncertainties and noises, an Artificial neural network is suggested to calibrate the force corresponding to the produced voltage., Ce manuscrit de thèse est une dissertation en format multi-articles sur la conception, l'optimisation et la fabrication d'actionneurs pneumatiques souples pour des applications robotiques souples. Introduite comme une nouvelle technologie ces dernières années, la robotique souple ouvre de nouveaux horizons dans le domaine de la robotique grâce à des caractéristiques prometteuses telles que l'adaptabilité, la légèreté, la facilité d'assemblage et le faible coût pour réaliser des configurations complexes dans divers environnements. Même s'il existe une grande diversité d'applications pour les SFA, de nombreux défis subsistent dans ce domaine, notamment le contrôle de la rigidité et de la flexion. Pour illustrer les applications méthodologiques et théoriques actuelles des systèmes robotiques souples, le premier article présente une revue systématique des actionneurs fluidiques souples qui ont relèvent les défis critiques en matière de matériaux souples et actifs, de méthodes de traitement, d'architectures de préhension, de capteurs et de méthodes de contrôle. Différents modèles constitutifs de matériaux en silicone proposés et testés dans la littérature sont régénérés par le logiciel ABAQUS afin de comparer les données de déformation et de contrainte réelles issues des modèles constitutifs avec les données d'essai de traction standard basées sur la norme ASTM412. Cet article montre que la plupart de ces modèles peuvent prédire le modèle du matériau de manière acceptable dans une petite gamme de données de contrainte-déformation. Mais pour de grandes valeurs de contrainte-déformation, quelques-uns d'entre eux prédisent le comportement du matériau silicone avec précision. Le deuxième article présente un nouveau type de doigt souple avec une articulation mobile à commande pneumatique basée sur le contrôle du point de flexion et une rigidité variable. Le doigt proposé est plus performant que les solutions précédentes en termes d'espace 3D atteignable et de forces de contact applicables au bout du doigt en changeant la position de son articulation, et donc, le point de flexion. La méthode des éléments finis et l'algorithme NSGA-II sont appliqués pour optimiser la géométrie de l'articulation afin de maximiser l'angle de flexion et de minimiser les dimensions de l'articulation. Le troisième article de cette thèse se concentre sur le développement d'un nouveau type de préhenseur souple dextre avec trois doigts reconfigurables et une paume active améliorant les capacités de manipulation dextre. Dans chaque doigt, le point de flexion et la longueur de manipulation effective peuvent être modifiés et contrôlés en déplaçant une tige rigide insérée dans le trou central du doigt. La capacité de manipulation dextre de préhenseur robotique souple est validée par différents tests expérimentaux, notamment la rotation, les saisies multiples et le roulement. Par conséquent, deux types de paume artificiel à vide (ventouse et particules granulaires) sont utilisés pour garantir une large gamme de tâches de manipulation d'objets que les préhenseurs souples proposés précédemment ne peuvent pas complètement réaliser. Dans le dernier chapitre de cette thèse, le quatrième article propose un capteur tactile peu coûteux et facile à fabriquer pour des applications en robotique. Il est très flexible et facile à utiliser, ce qui en fait un choix approprié pour les applications de robots souples. La plupart des matériaux (encre conductrice, silicone, carte de contrôle) utilisés dans la fabrication de ce capteur sont peu coûteux et peuvent être trouvés facilement sur le marché. Le capteur capacitif proposé peut détecter la position et la force appliquée en mesurant la charge électrique des électrodes. En raison des incertitudes et des bruits, un réseau neuronal artificiel est proposé pour calibrer la force correspondant à la tension produite.

This thesis manuscript describes the modeling, design and experimentation of a plane-parallel prestressed mechanism whose actuators are shape memory alloy (SMA) components working in an antagonistic way. The integration of this type of active materials in robotic systems is becoming more and more important due to their remarkable properties for metals: superelasticity, high damping capacities, as well as different shape memory effects depending on the applied thermomechanical conditions. The so-called "one-way" shape memory effect is particularly interesting from an application point of view for the creation of new generation actuators. Linear and rotary SMA-based actuators are widely developed in the literature. However, several obstacles hinder the development of such systems: difficulty in coupling thermal/electrical insulation and mechanical fixity; complexity in modeling the behavior due to a nonlinear and hysteretic response; strong thermomechanical couplings; need for restoring forces to create a two-way actuation. This last point is even more complex to manage in the presence of several SMA components working in parallel in a mechanism: the multi-antagonistic character of the actuation, coupled with a non-linear hysteretic response of each SMA, is the main focus of this scientific research. In practice, a finite element model of a plane parallel prestressed mechanism with three degrees of freedom and driven by six SMA wires has been developed. These wires are binary actuated independently in the first approach, but they all interact together, making the prediction of the actuation complex. Different cases of study have been treated: discrete workspace, configurations to be avoided, variable stiffness, attraction and hysteresis effects acting on the workspace. A physical demonstrator was also designed and tested. A key point was the thermomechanical "preparation" of the SMA wires before their use, as well as the implementation of a specific procedure for anchoring the wires in the mechanism thanks to a judicious choice of the phase transformation temperatures of the selected nickel-titanium alloy. The experimental results showed the efficiency of the system implementation, and the good qualitative agreement of the measurements with the simulations makes it possible to control the system. The study brings elements of understanding of the complex phenomena involved, which allows to consider the design of innovative actuators with new architectures of arrangement of the SMA components., Ce manuscrit de thèse décrit la modélisation, conception et expérimentation d’un mécanisme précontraint parallèle plan dont les actionneurs sont des composants en alliage à mémoire de forme (AMF) travaillant de manière antagoniste. L'intégration de ce type de matériaux actifs dans des systèmes robotiques prend de plus en plus d'ampleur du fait de leurs propriétés remarquables pour des métaux : superélasticité, grandes capacités d’amortissement, ainsi que différents effets de mémoire de forme dépendant des conditions thermomécaniques appliquées. L’effet mémoire de forme dit « simple-sens » est particulièrement intéressant d’un point de vue applicatif pour la création d’actionneurs de nouvelle génération. Les actionneurs linéaires et rotatifs à base d’AMF sont largement développés dans la littérature. Plusieurs verrous freinent toutefois le développement de tels systèmes : difficulté à coupler isolation thermique/électrique et fixité mécanique ; complexité à modéliser le comportement du fait d’une réponse non-linéaire et hystérétique ; couplages thermomécaniques forts ; nécessité de forces de rappel pour créer un actionnement à double-sens. Ce dernier point est d’autant plus complexe à gérer en présence de nombreux composants AMF travaillant en parallèle dans un mécanisme : le caractère multi-antagoniste de l’actionnement, couplé à une réponse non-linéaire hystérétique de chaque AMF, est le verrou scientifique sur lequel ce travail de recherche s’est focalisé. En pratique, un modèle par éléments finis a été développé sur un mécanisme précontraint parallèle plan à trois degrés de liberté et piloté par six fils AMF. Ceux-ci sont actionnés indépendamment de manière binaire en première approche, mais interagissent tous ensemble, rendant complexe la prédiction de l’actionnement. Différents cas d’étude ont été traités : espace de travail discret, configurations à éviter, rigidité variable, effet d’attraction et d’hystérésis agissant sur l’espace de travail. Un démonstrateur physique a également été conçu et testé. Un point clé a été la « préparation » thermomécanique des fils AMF avant leur utilisation, ainsi que la mise en place d’une procédure spécifique d’ancrage des fils dans le mécanisme grâce à un choix judicieux des températures de transformation de phase de l’alliage nickel-titane sélectionné. Les résultats expérimentaux ont montré l’efficacité de mise en œuvre du système, et le bon accord qualitatif des mesures par rapport aux simulations rend envisageable une commande du système. L’étude apporte des éléments de compréhension des phénomènes complexes impliqués, ce qui permet d’envisager la conception d’actionneurs innovants avec de nouvelles architectures d’arrangement des composants AMF.