Conception préliminaire d'un moteur rotatif continu à combustion induite par onde de choc

La conception et l'analyse d'un nouveau moteur utilisant des propulseurs supersoniques en rotation sont présentées dans le présent mémoire. L'objectif premier de ce moteur est de produire la plus grande puissance spécifique possible. Les propulseurs sont dérivés des statoréacteurs et RAMAC. Fixés à la périphérie d'un cerceau en fibres de carbone tournant à des vitesses tangentielles de Mach=2.5, les propulseurs génèrent de la poussée. Celle-ci est convertie en couple par le rayon du cerceau et produit par conséquent de la puissance de rotation. Contrairement aux moteurs à piston ou aux pulsoréacteurs, l'énergie est constamment fournie au système. Aussi, l'aspect rotatif ne comporte aucun mouvement oscillatoire, ce qui repousse les limites de régime actuellement atteignables avec les moteurs à piston. Les propulseurs sont réalisés en composite carbone/carbone pour assurer une masse minimale et une résistance thermique optimale. Leur démarrage est assuré par le principe des diffuseurs perforés qui permet de purger les gaz d'admission."--Résumé abrégé par UM

Dielectric elastomer actuators for binary robotics and mechatronics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections."February 2006."Includes bibliographical references (p. 145-153).Future robotics and mechatronics applications will require systems that are simple, robust, lightweight and inexpensive. A suggested solution for future systems is binary actuation. Binary actuation is the mechanical analogy to digital electronics, where actuators "flip" between two discrete states. Systems can be simple since low-level feedback control, sensors, wiring and electronics are virtually eliminated. However, conventional actuators, such as DC motors and gearbox are not appropriate for binary robotics because they are complex, heavy, and expensive. This thesis proposes a new actuation technology for binary robotics and mechatronics based on dielectric elastomer (DE) technology. DE actuators are a novel class of polymer actuators that have shown promising low-cost performance. These actuators were not well understood and, as a result, faced major reliability problems. Fundamental studies conducted in this thesis reveal that reliable, high performance DE actuation based on highly viscoelastic polymers can be obtained at high deformation rates, when used under fast, intermittent motion.(cont.) Also, analytical models revealed that viscoelasticity and current leakage through the film govern performance. These results are verified by an in-depth experimental characterizion of DE actuation. A new DE actuator concept using multi-layered diamond-shaped films is proposed. Essential design tools such as reliability/performance trade-offs maps, scaling laws, and design optimization metrics are proposed. A unit binary module is created by combining DE actuators with bistable structures to provide intermittent motion in applications requiring long-duration stateholding. An application example of binary robots for medical interventions inside Magnetic Resonance Imaging (MRI) systems illustrates the technology's potential.by Jean-Sébastien Plante.Ph.D

Genetic variants of the alpha-synuclein gene SNCA are associated with multiple system atrophy.

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterized by parkinsonism, cerebellar ataxia and autonomic dysfunction. Pathogenic mechanisms remain obscure but the neuropathological hallmark is the presence of alpha-synuclein-immunoreactive glial cytoplasmic inclusions. Genetic variants of the alpha-synuclein gene, SNCA, are thus strong candidates for genetic association with MSA. One follow-up to a genome-wide association of Parkinson's disease has identified association of a SNP in SNCA with MSA

Conception préliminaire d'un moteur rotatif continu à combustion induite par onde de choc

La conception et l'analyse d'un nouveau moteur utilisant des propulseurs supersoniques en rotation sont présentées dans le présent mémoire. L'objectif premier de ce moteur est de produire la plus grande puissance spécifique possible. Les propulseurs sont dérivés des statoréacteurs et RAMAC. Fixés à la périphérie d'un cerceau en fibres de carbone tournant à des vitesses tangentielles de Mach=2.5, les propulseurs génèrent de la poussée. Celle-ci est convertie en couple par le rayon du cerceau et produit par conséquent de la puissance de rotation. Contrairement aux moteurs à piston ou aux pulsoréacteurs, l'énergie est constamment fournie au système. Aussi, l'aspect rotatif ne comporte aucun mouvement oscillatoire, ce qui repousse les limites de régime actuellement atteignables avec les moteurs à piston. Les propulseurs sont réalisés en composite carbone/carbone pour assurer une masse minimale et une résistance thermique optimale. Leur démarrage est assuré par le principe des diffuseurs perforés qui permet de purger les gaz d'admission."--Résumé abrégé par UM

The Calibration of a Parallel Manipulator with Binary Actuation

Abstract This paper investigates how parameter identification can improve the calibration of elastically averaged parallel manipulators. The method developed is applied to a needle manipulator for intra-Magnetic Resonance Imaging (MRI) prostate cancer treatment. The device uses MRI-compatible Dielectric Elastomer Actuators to precisely guide a needle during its insertion for taking biopsy or implanting radioactive seeds in the prostate. Here, an analytical model of the device is presented and a sensitivity analysis identifies the key model parameters. Parameter identification is conducted with an optimization algorithm. The method is tested on both simulated parameter values and experimental data. The results show that the method can improve the device accuracy by at least one order of magnitude (on simulated parameters)

Sleeved Bending Actuators for Soft Grippers: A Durable Solution for High Force-to-Weight Applications

Soft grippers are known for their ability to interact with objects that are fragile, soft or of an unknown shape, as well as humans in collaborative robotics applications. However, state-of-the-art soft grippers lack either payload capacity or durability, which limits their use in industrial applications. In fact, high force density pneumatic soft grippers require high strain and operating pressure, both of which impair their durability. This work presents a new sleeved bending actuator for soft grippers that is capable of high force density and durability. The proposed actuator is based on design principles previously proven to improve the life of pneumatic artificial muscles, where a sleeve provides a uniform reinforcement that reduces local stresses and strains in the inflated membrane. The sleeved bending actuator features a silicone membrane and an external two-material sleeve that can support high pressures while providing a flexible grip. The proposed sleeved bending actuators are validated through two grippers, sized according to foreseen soft gripper applications: A small gripper for drone perching and lightweight food manipulation, and a larger one for the manipulation of heavy material (>5 kg) of various weights and sizes. Performance assessment shows that these grippers have payloads up to 5.2 kg and 20 kg, respectively. Durability testing of the grippers demonstrates that the grippers have an expected lifetime ranging from 263,000 cycles to more than 700,000 cycles. The grippers are tested in various settings, including the integration of a gripper into a Phantom 2 quadcopter, a perching demonstration, as well as the gripping of light and heavy food items. Experiments show that sleeved bending actuators constitute a promising avenue for durable and strong soft grippers

Handicap et trisomie : la parole des adultes. Configurations et itinéraires, implications et orientations

[No abstract