569 research outputs found
Modelling the Physical Human-Exoskeleton Interface
No full textL'abstract è presente nell'allegato / the abstract is in the attachmen
Modelling friction at the mechanical interface between the human and the exoskeleton
No full textIn virtual assessments of exoskeletons, often, friction is not modelled even though the actual interface consists of straps or moulded surfaces, where friction could play a significant role. In this work, the human-exoskeleton interaction during the use of a passive lower limb exoskeleton is modelled in three test cases through two different interface models. In particular, a model introducing friction at the human-exoskeleton interface is compared with a more conventional model that uses a kinematic joint to simulate the interface forces. Both the models show a good match between the empirical and predicted distribution of body weight between the subject and the exoskeleton. However, the results also show different trends of the moment required at the assisted joint by the different interface models, highlighting the importance of a realistic interface model to investigate the effectiveness of the exoskeleton in virtual assessments
An observational method for Postural Ergonomic Risk Assessment (PERA)
No full textMonotonous, repetitive work characterizes production lines. Repetitive movements and awkward postures are the most prominent physical risk factors in the workplace. Various legislations have been enacted along with technical standards for ergonomic risk evaluation to ensure the safety of the operators. There are numerous methods to assess the ergonomic risk at work. However, most methods are not meant to be used for assessing cyclic work. This paper proposes a method, Postural Ergonomic Risk Assessment (PERA), which is suitable to evaluate the postural ergonomic risk of short cyclic assembly work. Its key features are simplicity and compliance with standards. The added value of the method is that it provides an analysis of every work task in the work cycle, which facilitates the identification of sources of high risk to the operator. The method has been verified on nine work cycles, constituted by 88 work tasks, and it demonstrates accordance with the European Assembly Worksheet (EAWS), which has been developed to comply with the relevant standards and is one of the most comprehensive tools for ergonomic risk assessment. Industrial relevance: The simplicity and the compliance with standards of the proposed method would allow for a quick check of every work task of the work cycle and identification of problem areas. With further work, it would be possible to integrate the method along with work design tools used in the industry
Subhash Chander Sahdev interviewed by Gurpreet Grewal-Santini, 5 June 2013
No full textTells of moving around Uganda for his father's job, inter-racial marriages and what the hardest thing for him to leave behind was
Simulating the dynamics of a human-exoskeleton system using kinematic data with misalignment between the human and exoskeleton joints
No full textMusculoskeletal model-based simulation can be a powerful tool in the design and evaluation of exoskeletons. They are used extensively during the virtual prototyping stage using motion data of the human without the exoskeleton. An ideal exoskeleton model, perfectly aligned with the human joint axes, can be used to co-simulate the human and exoskeleton dynamics. However, misalignment between the human and exoskeleton joints is commonly observed during the use of an exoskeleton, potentially leading to a loss in the effective assistance received by the user. Motion data collected with the user wearing the exoskeleton should, normally, be able to capture the misalignment between the human and exoskeleton joints. Using misaligned motion data in the combined human-exoskeleton model can lead to complications in the virtual model and unrealistic outputs. One way to tackle these complications is to assume alignment between the human and exoskeleton joints in the model by kinematically constraining it.
This work presents a new method that facilitates the analysis of misaligned human-exoskeleton systems. This is achieved by introducing artificial segments between the human and exoskeleton models. These artificial segments, the so-called dummy segments, ensure kinetic alignment between the human and exoskeleton joints in the model without altering the observed kinematics from the actual trial. The method is demonstrated using an active lower-limb exoskeleton that aims to assist the elderly in stair negotiation. A single subject performed eight trials with the exoskeleton in a laboratory. Motion data of both the subject and exoskeleton were recorded using an optical marker-based motion capture system. Further, the measured ground reaction force and the exoskeleton assistive force were used as inputs in the combined human-exoskeleton model. The outputs from the inverse dynamics analysis of the model with the dummy segments were compared to those from a reference model, where the measured external forces were applied directly to the human model at the corresponding reference points, bypassing the human-exoskeleton interface model completely. The results of the knee compression force, knee flexion moment, and activation of vastus lateralis from the model with the dummy segments showed good agreement with the reference model. The use of the dummy segments allows the study of aligned kinetics and misaligned kinematics from the same model
Influence of the Microstructural and Mechanical Properties of Reinforced Graphene in Magnesium Matrix Fabricated by Friction Stir Processing
No full textThe aim of the present researchwork is to find out the influence of uniform dispersion of different volume percentages of graphene nanoparticles into magnesium matrix, fabricated by friction stir processing (FSP). These composites can be used in various applications, particularly in electrical, automobile and aerospace industries due to its lightweight and good electrical and mechanical properties. The friction processed surface of pure magnesium and composites were characterized through X-ray diffraction (XRD). Mechanical properties such as tensile test of the friction stir processed (FSPed) composites were performed in universal testing machine and the specimen was prepared according to standard dimension by wire EDM. The initial properties of the material were compared to the FSPed pure magnesium matrix composites. The role of various volume percentages of reinforcement by FSP resulted in grain refinements as well as improved the mechanical properties of the FSPed composite.Nazish Alam, Md. Manzar Iqbal, Chander Prakash, Subhash Singh, and Animesh Basa
Physical and Virtual Assessment of a Passive Exoskeleton
No full textThe paper describes the testing activity carried out on a commercial
passive lower limb exoskeleton: the Chairless Chair, a wearable sitting support
that allows workers to switch between a standing and a sitting posture. Tests
were carried out with FCA workers who volunteered for the study. Laboratory
trials served to familiarize the users and to obtain an initial feedback on the
usability of the device in the assembly line. At a second step, virtual modelling
of a few static postures was carried out, reproducing the anthropometry and the
postural angles of the worker while using the exoskeleton. A main output of the
model is the estimate of what forces are exchanged between the subject and the
exoskeleton. In the case of the lower limb exoskeleton, an important parameter
to consider is the percentage of the subject’s weight that is sustained by the
exoskeleton frame. The higher is this percentage, the lower will be the strain on
the subject’s lower limbs. First comparison between experimental and simulated
results showed good agreement and auspicious advantages of exoskeletons in
relieving the strain on workers
The Electronic Silk Road: How the Web Binds the World in Commerce
No full textOn the ancient Silk Road, treasure-laden caravans made their arduous way through deserts and mountain passes, establishing trade between Asia and the civilizations of Europe and the Mediterranean. Today’s electronic Silk Roads ferry information across continents, enabling individuals and corporations anywhere to provide or receive services without obtaining a visa. But the legal infrastructure for such trade is yet rudimentary and uncertain. If an event in cyberspace occurs at once everywhere and nowhere, what law applies? How can consumers be protected when engaging with companies across the world?
In this accessible book, cyber-law expert Anupam Chander provides the first thorough discussion of the law that relates to global Internet commerce. Addressing up-to-the-minute examples, such as Google’s struggles with China, the Pirate Bay’s skirmishes with Hollywood, and the outsourcing of services to India, the author insightfully analyzes the difficulties of regulating Internet trade. Chander then lays out a framework for future policies, showing how countries can dismantle barriers while still protecting consumer interests
Manu Samriti Chander\u27s Brown Romantics: Poetry and Nationalism in the Global Nineteenth Century
No full textThe last decade has witnessed increasing critical interest in questions of race, nation, and empire during the Romantic era. Manu Samriti Chander\u27s Brown Romantics: Poetry and Nationalism in the Global Nineteenth Century contributes to this discussion by examining the extensive international impact of Romantic poetry on writers beyond Britain. Part of Bucknell University Press\u27s Transits: Literature, Thought, and Culture series, his work provides a fascinating and unique perspective on global literary relations. He demonstrates how Henry Derozio of India, Egbert Martin of British Guiana, and Henry Lawson of Australia adopted the role of the Romantic author to shape nationalist movements in their countries and mediate their colonial relationship with England. By reading British writers in relation to those of other nations, Brown Romantics questions the privileging of a Eurocentric canon and challenges us to widen our definition of ‘Romantic’ literature
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