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Age Effects on Upper Limb Kinematics Assessed by the REAplan Robotin Healthy School-Aged Children

The use of kinematics is recommended to quantitatively evaluate upper limb movements. The aims of this study were to determine the age effects on upper limb kinematics and establish norms in healthy children. Ninetythree healthy children, aged 3–12 years, participated in this study. Twenty-eight kinematic indices were computed from four tasks. Each task was performed with the REAplan, a distal effector robotic device that allows upper limb displacements in the horizontal plane. Twenty-four of the 28 indices showed an improvement during childhood. Indeed, older children showed better upper limb movements. This study was the first to use a robotic device to show the age effects on upper limb kinematics and establish norms in healthy children

Novel infinitely Variable Transmission allowing efficient transmission ratio variations at rest

Recent studies showed that Continuously Variable Transmissions (CVT) and Infinitely Variable Transmissions (IVT) can considerably improve the locomotion efficiency in legged robot. A CVT is a transmission whose ratio can be continuously varied and an IVT is a transmission whose ratio can be continuously varied from positive to negative values. However, efficient use of such transmissions in walking applications requires changing the transmission ratio at a minimal energy cost, even at rest, i.e. when the input shaft is not rotating. This contribution proposes a novel CVT and IVT principle which can achieve such ratio variations at rest. The presented CVT is a modified planetary gear, whose planets are conical and mounted on inclined shafts, and whose ring is made of contiguous diabolo-shaped rollers. This configuration enables the control of the transmission ratio by adjusting the point of contact between the cones and rollers that comprise the ring. A traditional planetary gear system can be added to the CVT to form an IVT

Bio-inspired design and validation of the Efficient Lockable Spring Ankle (ELSA) prosthesis

Over the last decade, active lower-limb prostheses demonstrated their ability to restore a physiological gait for transfemoral amputees by supplying the required positive energy balance during daily life locomotion activities. However, the added-value of such devices is significantly impacted by their limited energetic autonomy, excessive weight and cost, thus preventing their full appropriation by the users. There is thus a strong incentive to produce active yet affordable, lightweight and energy efficient devices. To address these issues, we developed the ELSA (Efficient Lockable Spring Ankle) prosthesis embedding both a lockable parallel spring and a series elastic actuator, tailored to the walking dynamics of a sound ankle. The first contribution of this paper concerns the developement of a bio-inspired, lightweight and stiffness-adjustable parallel spring, comprising an energy efficient ratchet and pawl mechanism with servo actuation. The second contribution is the addition of a complementary rope-driven series elastic actuator to generate the active push-off. The system produces a sound ankle torque pattern during flat ground walking. Up to 50% of the peak torque is generated passively at a negligible energetic cost (0.1 J/stride). By design, the total system is lightweight (1.2kg) and low cost

Improved constitutive equations of piezoelectric monomorphs: application to the preliminary study of a traveling-wave peristaltic pump

This article establishes the constitutive equations of a piezoelectric monomorph by separating the effects of the piezoelectric action from the effects of the external loads and by considering in both cases a static equilibrium of forces and moments. Unlike previous studies, our model explicitly incorporates the effects of transverse strains and electric field gradients in order to approach more faithfully the real strains and stresses in the monomorph. This model, which can be easily generalized to other types of benders and applied to complex study cases is used in this paper to analyse the impact of the characteristic parameters of an original traveling-wave peristaltic pump on its performance

Elaboration et application d'une approche multidisciplinaire pour la conception d'un actionneur électrique à rotor sphérique

Depuis ses débuts, la conception des convertisseurs électromécaniques se limitait à l'optimisation, par l'électrotechnicien, de la conversion d'énergie électrique en énergie mécanique. Cette énergie, alors fournie sous la forme quasi exclusive d'un mouvement à un seul degré de liberté, le plus souvent rotatif, devait ensuite être adaptée, par les mécaniciens, aux besoins du système à actionner. Aujourd'hui, grâce aux évolutions récentes dans des domaines aussi variés que l'électronique de puissance, l'informatique ou encore la conception et la fabrication assistées par ordinateur, il est devenu possible de concevoir de nouveaux actionneurs directement en fonction des besoins des applications auxquelles ils sont destinés. Ainsi, des actionneurs pouvant posséder plusieurs degrés de liberté, tant en rotation qu'en translation, ont été développés. Dans ce contexte, cette thèse poursuit deux objectifs. Le premier est de proposer une démarche de conception intégrant au mieux les aspects électriques et mécaniques de systèmes électromécaniques tels que ces nouveaux actionneurs. Plus largement, elle a pour vocation de s'appliquer à tous types de problèmes multidisciplinaires où la prise en compte des différentes disciplines et de leurs interactions est indispensable pour assurer les performances globales du produit final. Plus particulièrement, elle est adaptée aux cas de recherches qui, contrairement aux cas de développements, font parfois intervenir des concepts mal maîtrisés. Le second objectif est d'appliquer cette démarche à la conception d'un actionneur électrique dont le rotor, de forme sphérique, est actionné avec un débattement illimit?? selon deux des trois degrés de libertéqu'il possède en rotation. Suivant les différentes étapes constituant cette démarche, divers concepts de solution sont d'abord générés, tant pour les aspects électriques d'actionnement que pour les aspects mécaniques de guidage. Ces concepts sont ensuite caractérisés, via une série de modélisations et d'expérimentations, avant d'être combinés en vue de produire une solution globale, dimensionnée, fabriquée et validée sur un banc d'essai.From the outset, the design of electromechanical converters was limited to the optimization, by electrical engineers, of the conversion of electrical energy to mechanical energy. The latter was at that time nearly exclusively provided under the form of single degree of freedom motion, more often rotary, and had to be adapted, by mechanical engineers, to the needs of the system to be actuated. Today, thanks to recent evolutions in fields as various as power electronics, computer capabilities or computer-aided design and manufacturing (CAD-CAM), it has become possible to design new actuators by taking directly into account the needs of the applications they are intended for. As a result, actuators with several degrees of freedom, both in rotation and in translation, have been developed. Within this context, this thesis pursues two objectives. The first consists in proposing a new design method integrating as best as possible the electrical and mechanical aspects of electromechanical systems such as these new actuators. More broadly, its vocation is to be applicable to all multidisciplinary problems where taking into account each discipline and their interactions are necessary to ensure the global performances of the final product. More particularly, this method is adapted to the case of researches that, contrary to the case of other developments, sometimes includes badly mastered concepts. The second aim is to apply this approach to the design of an electrical motor with a spherical rotor actuated, with an unlimited angular range, along two of the three degrees of freedom it possesses in rotation. Following the basic steps involved in this approach, various solution concepts were first generated both for the electrical actuation aspects and the mechanical guiding aspects. These concepts were then characterized, via a number of modeling and experimentation phases, before being combined in order to obtain a global solution, which was then sized, manufactured and validated on a test bench.(FSA 3)--UCL, 200

[Downloaded 2013/05/15 at 12:19:52] Variable Stiffness Actuator Applied to an Active Ankle Prosthesis: Principle, Energy-Efficiency, and Control

Series elastic actuators are very popular in rehabilitation robotics. Among other advantages, elastic elements between the actuator and the load permit to store and release energy during the task completion, such that the energy balance is improved and the motor power peak is decreased. In rhythmic tasks like walking, this reduces to design the spring stiffness such that it works at resonance. To comply with different gaits and cadences, it is therefore necessary to design Variable Stiffness Actuators (VSA). This paper proposes three contributions: (i) we apply a particular concept of VSA to an active ankle prosthesis; (ii) we discuss the relevance of using VSA to change the stiffness also within the gait cycle; and (iii) we elaborate some control strategies for this device. Our guideline is to track a mechanical design and a controller maximizing energy efficiency. We establish that a promising approach is simply to control the amount of energy stored in the elastic element. Référence bibliographiqu

Magnet and method for designing a magnet

The invention relates to a magnet for guiding a beam of charged particles along a curved path in a path plane, comprising a first (210) and second (220) coil (pole coils) disposed symmetrically with respect to said path plane, at a first and second distance of said path plane, and adapted for producing a magnetic field in a direction perpendicular to said path plane along said path; a third (230) and fourth (240) coil (flux return coils) disposed along said path plane, at an inner and outer side respectively of said curved path and at a third and fourth distance thereof, and adapted for producing a magnetic field in same direction perpendicular to said path plane along said path. Said first (210) and said second coils (220) have an outer shape limited by a linear portion on a side towards the path plane, and parallel thereto, and a curved portion in the opposite direction. The invention also relate to a method for designing such a magnet

Pole Pitch Optimization of Permanent Magnet Electrodynamic Suspensions in High-Speed Transportation Systems

Permanent magnet electrodynamic suspensions are good candidates to enable ground transportation systems to reach very high speeds. In these suspensions, the pole pitch of the permanent magnet field source has a significant influence on their performance. This article, therefore, studies qualitatively the impact of performance criteria, whether partial, such as the lift-to-drag ratio, or global, such as the global cost, on the optimal pole pitch. It is shown that the latter depends both on the considered criteria and the operating conditions. In addition, it is pointed out that 3-D models considering the edge effects are essential to derive the optimal pole pitch