Forces armées des États-Unis

Les forces armées des États-Unis (en anglais United States Armed Forces), souvent appelées Armée américaine dans le langage courant français, abrégées en anglais par « » ou « », sont les armées entretenues par les États-Unis. Au , elle compte 1 281 900 militaires actifs ; si les garde-côtes sont exclus du décompte, il s'agit, en effectifs, de la deuxième ou troisième armée mondiale, derrière l'Armée populaire de libération chinoise, et pratiquement à égalité avec les Forces armées indiennes. Le département de la Défense des États-Unis (DoD ou DOD) emploie également, au , dont . En termes de budget (environ de dollars en 2013 soit 36 % du budget officiel de la Défense dans le monde), de force de frappe et de capacité de déploiement, il s'agit de la première armée mondiale. Une partie relativement importante de l'armée des États-Unis est déployée hors du territoire national. Elle joue un grand rôle dans la politique étrangère du pays. L'Armée américaine comprend six composantes

A Haptic Knob with a Hybrid Ultrasonic Motor and Powder Clutch Actuator

Hannes Bleuler, Etienne Burdet, Dominique Chapuis, Xavier Michel

In haptics, the forces to be displayed vary widely in terms of magnitude and bandwidth. A single actuator can hardly comply with these requirements. It has thus been proposed to combine electrical motors and passive devices in a hybrid actuator to cover a larger range of displayable forces. In this paper, different hybrid actuators are reviewed and a novel hybrid USM/clutch actuator is presented. It has been developed for haptic applications and its principle is adaptable to MR compatible robots. The complementary dynamic properties of the USM, which is a velocity source, and a torque controlled clutch, lead to a simple mechanism offering more control modes and lower power consumption than previous hybrid actuators. A haptic knob is designed and realized to test this approach. It includes a differential gear that allows the powder brake to mimic the behavior of a clutch. Haptic effects such as springs or walls have been implemented and successfully tested on the prototype.

2007

Buckling of an elastic rod embedded on an elastomeric matrix: planar vs. non-planar configurations

Jia Liu, Pedro Miguel Nunes Pereira de Almeida Reis

We investigate the buckling of a slender rod embedded in a soft elastomeric matrix through a combination of experiments, numerics and theory. Depending on the control parameters, both planar wavy (2D) or non-planar coiled (3D) configurations are observed in the post-buckling regime. Our analytical and numerical results indicate that the rod buckles into 2D configurations when the compression forces associated to the two lowest critical modes are well separated. In contrast, 3D coiled configurations occur when the two buckling modes are triggered at onset, nearly simultaneously. We show that the separation between these two lowest critical forces can be controlled by tuning the ratio between the stiffness of the matrix and the bending stiffness of the rod, thereby allowing for specific buckling configurations to be target by design.

Royal Society of Chemistry2014

mano: A Wearable Hand Exoskeleton for Activities of Daily Living and Neurorehabilitation

Inaki Asier Iturrate Gil, Serafeim Perdikis, Luca Randazzo

Hand sensorimotor impairments are among the most common consequences of injuries affecting the central and peripheral nervous systems, leading to a drastic reduction in the quality of life for affected individuals. Combining wearable robotic exoskeletons and human-machine interfaces is a promising avenue for the restoration and substitution of lost and impaired functions for these users. In this study, we present a novel hand exoskeleton, mano, designed to assist and restore hand functions of people with motor disabilities during activities of daily living (ADL) and in neurorehabilitative scenarios. Compared to state-of-the-art devices, our system is fully wearable, portable and minimally obtrusive on the hand. The exoskeleton can actively control flexion and extension of all fingers, while allowing natural somatosensorial interactions with the environment surrounding the users. We evaluated the device from four different perspectives. A mechanical characterization, showing that the exoskeleton can cover more than 70% of healthy hand workspace and it can achieve forces at the fingertips sufficient for ADL. A functional characterization, where we showed how two users who suffered from spinal cord injuries were able to perform several ADL for the first time since their accidents. Thirdly, we evaluated the system from a neuroimaging perspective, showing that the device can elicit EEG brain patterns typical of natural hand motions. We finally exemplified the control of the hand exoskeleton within an exemplar framework, a brain-machine interface scenario, showing how motor intention can be successfully decoded for a continuous control of the device. Overall, our results showed that the device represents an ecological solution for use both in ADL and in scenarios aimed at promoting sensorimotor recovery.

Ieee-Inst Electrical Electronics Engineers Inc2018

mano: A Wearable Hand Exoskeleton for Activities of Daily Living and Neurorehabilitation

Inaki Asier Iturrate Gil, Serafeim Perdikis, Luca Randazzo

Ieee-Inst Electrical Electronics Engineers Inc2018