1,720,962 research outputs found
Kineto-dynamic modeling of human upper limb for robotic manipulators and assistive applications
Full text linkThe sensory-motor architecture of human upper limb and hand is characterized by a complex inter-relation of multiple elements, such as ligaments, muscles, and joints. Nonetheless, humans are able to generate coordinated and meaningful motor actions to interact-and eventually explore-the external environment. Such a complexity reduction is usually studied within the framework of synergistic control, whose focus has been mostly limited on human grasping and manipulation. Little attention has been devoted to the spatio-temporal characterization of human upper limb kinematic strategies and how the purposeful exploitation of the environmental constraints shapes human execution of manipulative actions. In this chapter, we report results on the evidence of a synergistic control of human upper limb and during manipulation with the environment. We propose functional analysis to characterize main spatio-temporal coordinated patterns of arm joints. Furthermore, we study how the environment influences human grasping synergies. The effect of cutaneous impairment is also evaluated. Applications to the design and control of robotic and assistive devices are finally discussed
Contact with Sliding over a Rotating Ridged Surface: The Turntable Illusion
Full text linkThe mechanical interaction between the skin and the environment is important in shaping our knowledge of object properties. In addition, the response of cutaneous mechanoreceptors also contributes to our sense of limb position and motion. In previous papers, we demonstrated a striking motor error during self-paced hand movements over a ridged stationary surface, with the hand out of sight, which depended on the orientation of the ridges. Tactile feedback, combined with muscular-skeletal proprioception and the forward model of hand motion, produced a bias in the perceived hand displacement, which triggers a corrective motion in a direction towards the long axis of the ridges. Here, we found a similar effect when participants are required to slide over a rotating surface with ridges. Instead, in a control condition where participants were required to slide over a rotating smooth plate, they tend to deviate toward the same direction of the plate rotation. This is in agreement with our previous results, and well-explained by the fact that the bias induced by tactile feedback increases in absolute angular value during task execution, due to ridge rotation. We propose a Kalman filter to model the dynamic integration of touch and proprioception for the estimation of the perceived hand displacement
Design and Validation of the Readable Device: A Single-Cell Electromagnetic Refreshable Braille Display
No full textBlindness represents one of the major disabling societal causes, impacting the life of visually impaired people and their families. For what concerns the access to written information, one of the main tools used by blind people is the traditional Braille code. This is the reason why in the recent years, there has been a technological effort to develop refreshable Braille devices. These consist of multiple physical dots that dynamically change their configuration to reproduce different sequences of the letters in Braille code. Although promising, these approaches have many drawbacks, which are mainly related to costs, design complexity, portability, and power consumption. Of note, while many solutions have been proposed for multi-cell devices, the investigation of the potentialities of single-cell refreshable systems has received little attention so far. This investigation could offer effective and viable manners to overcome the aforementioned drawbacks, likely fostering a widespread adoption of such assistive technologies with end-users. In this article, we present the design and characterization of a new cost-effective single-cell Electromagnetic Refreshable Braille Display, the Readable system. We also report on tests performed with blindfolded and blind expert Braille code readers. Results demonstrate the effectiveness of our device in correctly reproducing alphanumeric content, opening promising perspectives in every-day life applications
The interaction between motion and texture in the sense of touch
Full text linkBesides providing information on elementary properties of objects, like texture, roughness, and softness, the sense of touch is also important in building a representation of object movement and the movement of our hands. Neural and behavioral studies shed light on the mechanisms and limits of our sense of touch in the perception of texture and motion, and of its role in the control of movement of our hands. The interplay between the geometrical and mechanical properties of the touched objects, such as shape and texture, the movement of the hand exploring the object, and the motion felt by touch, will be discussed in this article. Interestingly, the interaction between motion and textures can generate perceptual illusions in touch. For example, the orientation and the spacing of the texture elements on a static surface induces the illusion of surface motion when we move our hand on it or can elicit the perception of a curved trajectory during sliding, straight hand movements. In this work we present a multiperspective view that encompasses both the perceptual and the motor aspects, as well as the response of peripheral and central nerve structures, to analyze and better understand the complex mechanisms underpinning the tactile representation of texture and motion. Such a better understanding of the spatiotemporal features of the tactile stimulus can reveal novel transdisciplinary applications in neuroscience and haptics
A User-Centered Approach to Artificial Sensory Substitution for Blind People Assistance
Full text linkArtificial sensory substitution plays a crucial role in different domains, including prosthetics, rehabilitation and assistive technologies. The sense of touch has historically represented the ideal candidate to convey information on the external environment, both contact-related and visual, when the natural action-perception loop is broken or not available. This is particularly true for blind people assistance, in which touch elicitation has been used to make content perceivable (e.g. Braille text or graphical reproduction), or to deliver informative cues for navigation. However, despite the significant technological advancements for what concerns both devices for touch-mediated access to alphanumeric stimuli, and technology-enabled haptic navigation supports, the majority of the proposed solutions has met with scarce acceptance in end users community. Main reason for this, in our opinion, is the poor involvement of the blind people in the design process. In this work, we report on a user-centric approach that we successfully applied for haptics-enabled systems for blind people assistance, whose engineering and validation have received significant inputs from the visually-impaired people. We also present an application of our approach to the design of a single-cell refreshable Braille device and to the development of a wearable haptic system for indoor navigation. After a summary of our previous results, we critically discuss next avenues and propose novel solutions for touch-mediated delivery of information for navigation, whose implementation has been totally driven by the feedback collected from real end-users
Controlling Hand Movements Relying on Tactile Illusions: A Model Predictive Control Framework
Full text linkIn recent studies, we demonstrated that when a blindfolded participant slides her/his finger-pad on a ridged plate to reach a target, tactile feedback induces the illusory perception of bending towards the direction perpendicular to the ridges. The contribution of tactile motion estimate is hence optimally integrated in a Bayesian way, with the estimate of muscular-skeletal proprioception and motor command. As a consequence, a systematic deviation of hand trajectories in the opposite direction with respect to the one estimated by touch can be observed. The goal of this paper is to exploit the aforementioned tactile illusion to guide the user's finger, moving on a ridged plate, towards an arbitrary desired point A, while she/he is instructed to move towards another target B. To this aim, we designed a Model Predictive Control strategy in a simulated environment to estimate at each time instant the optimal ridge orientation that minimizes a proper cost function. We simulated fifty trials for different positions of points A and B, also varying the level of the noise associated with the motor command and to tactile cue. Results show that the final positions of the simulated trajectories are in a range of ±1.5° with respect to the position of the desired final goal for ~ 80% of the cases. These results open promising applications in the framework of haptic retargeting where only one real object is used and the other items of the scene are virtual
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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