1,720,970 research outputs found
Glove Exoskeleton for Extra-Vehicular Activities: Analysis of Requirements and Prototype Design
Full text linkThe objective of the thesis is the development of a prototype of a lightweight hand exoskeleton designed to be embedded in the gloved hand of an astronaut and to overcome the stiffness of the pressurized space suit. The system should be able to provide force and precision to the hand grip. The project involves various elements, in particular the analysis of the characteristics of the hand and of the EVA glove. Moreover solutions related to sensor and actuator should be investigated. Finally the study and the design of an appropriate robotic structure able to fullfit the requirements have to be performed
Stiffness of an EVA glove: objective evaluation and testing procedures
No full textHand fatigue is one of the major problems of astronauts during Extravehicular Activity (EVA), due to the stiffness of the space suit, in particular of the glove. In order to evaluate the stiffness of EVA gloves, different methods have been proposed in the past, mainly focused on the effects of wearing an EVA glove on hand performance when executing test protocols. In this paper, an objective method for the evaluation of the stiffness of EVA gloves is proposed, by means of a tendon-actuated finger probe. The finger probe is equipped with accelerometers, to measure the angles of its phalanges. These are actuated by applying different torques using the finger probe tendons. The EVA glove is tested in both pressurized and non pressurized conditions, thanks to a hypobaric glove box. An Orlan-DM EVA glove is tested and stiffness results are presented. This setup can be used for different kinds of gloves, not necessarily for EVA application, and allows direct, numerical measurement of their stiffnes
A comparison of sEMG temporal and spatial information in the analysis of continuous movements
No full textMuch effort has recently been devoted to the analysis of continuous movements with the aim of promoting EMG signal acceptance in several fields of application. Moreover, several studies have been performed to optimize the temporal and spatial parameters in order to obtain a robust interpretation of EMG signals. Resulting from these perspectives, the investigation of the contribution of EMG temporal and spatial information has become a relevant aspect for signal interpretation. This paper aims to evaluate the effects of the two types of information on continuous motions analysis. In order to achieve this goal, the spatial and temporal information of EMG signals were separated and applied as input for an offline Template Making and Matching algorithm. Movement recognition was performed testing three different methods. In the first case (the Temporal approach) the RMS time series generated during movements was the only information employed. In the second case (the Spatial approach) the mean RMS amplitude measured on each channel was considered. Finally, in the third case (the Spatio-Temporal approach) a combination of the information from both the previous approaches was applied. The experimental protocol included 14 movements, which were different from each other in the muscular activation and the execution timing. Results show that the recognition of continuous movements cannot disregard the temporal information. Moreover, the temporal patterns seem to be relevant also for distinguishing movements which differ only in the muscular areas they activate
Towards a Hand Exoskeleton for a Smart EVA Glove
Full text linkIn this paper we investigate the key factors associated with the realization of a hand exoskeleton that could be embedded in an astronaut glove for EVA (Extra Vehicular Activities). Such a project poses several and varied problems, mainly due to the complex structure of the human hand and to the extreme environment in which the glove operates. This work provides an overview of existing exoskeletons and their related technologies and lays the ground for the forthcoming prototype realization, by presenting a preliminary analysis of possible solutions in terms of mechanical structure, actuators and sensor
Analysis and optimization of a wire actuated, single effect n-R robotic structure
No full textThis paper investigates the kinematics and the optimization of a generic robotic structure composed by N serial rotary joints and actuated with a mono-directional tendon system. In the first part of the paper, the specific case that brought us to develop this study is introduced; the main motivations and the scenario with its specific constraints and design choices have been described. Since a complete and detailed analysis of an n-R serial structure with this kind of characteristics could not be found in the literature, the study of the kinematics and the parameter optimization of such a structure is treated as generally as possible, in order to make the procedure and the results applicable for any similar structure. Finally, in the last part, through the introduction of specific constraints and the definition of the parameters, the general analysis has been applied to the specific case of study: the preliminary study of a finger exoskeleton for an astronaut suit
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Embedding an exoskeleton hand in the astronaut's EVA glove: feasibility and ideas
No full textThis paper investigates the key factors associated to the realization of a hand exoskeleton to be embedded in an astronaut's EVA glove, in order to overcome the stiffness of the pressurized space suit. An overview regarding the main constraints related to the realization of a hand exoskeleton for EVA suits is provided, as well as a preliminary concept analysis of possible solutions in terms of mechanical structure, actuators and sensors. Furthermore, analyses of human hand kinematics and of the characteristics of the EVA glove's stiffness are presented, as a basis for design and dimensioning of the exoskeleton. The future exoskeleton will be a complex mechatronic system detecting the operator's movement through sensors, processing the acquired data and generating the motion through its actuation syste
A new method of measuring the stiffness of astronauts' EVA gloves
No full textHand fatigue is one of the most important problems of astronauts during their missions to space. This fatigue is due to the stiffness of the astronauts' gloves known as Extravehicular Activity (EVA) gloves. The EVA glove has a multilayered, bulky structure and is pressurized against the vacuum of space. In order to evaluate the stiffness of EVA gloves, different methods have been proposed in the past. In particular, the effects of wearing an EVA glove on the performance of the hands have been published by many researchers to represent the stiffness of the EVA glove. In this paper, a new method for measuring the stiffness of EVA gloves is proposed. A tendon-actuated finger probe is designed and used as an alternative to the human index finger in order to be placed inside an EVA glove and measure its stiffness. The finger probe is equipped with accelerometers, which work as tilt sensors, to measure the angles of its phalanges. The phalanges are actuated by applying different amount of torque using the tendons of the finger probe. Moreover, a hypobaric glove box is designed and realized to simulate the actual operating pressure of the EVA glove and to measure its stiffness in both pressurized and non-pressurized conditions. In order to prove the right performance of the proposed finger probe, an Orlam-DM EVA glove is used to perform a number of tests. The equation of stiffness for the PIP joint of this glove is extracted from the results acquired from the tests. This equation presents the torque required to flex the middle phalanx of the glove. Then, the effect of pressurization on the stiffness is highlighted in the last section. This setup can be used to measure the stiffness of different kinds of EVA gloves and allows direct, numerical comparison of their stiffnes
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