A Novel Index to Compare the Representation Quality of Objects Approximated with Spheres

Practical collision detection problems require very fast algorithms. The quality of the object representation plays a key role in the efficiency of these algorithms. In this paper a new index is presented which makes it possible to compare in terms of quality of representation different algorithms that approximate an object by means of spheres. Comparative results with other indexes are provided

Nuovo codice di calcolo per lo studio del contatto tra elementi elastici ed elementi rigidi

This paper presents a new tool to find the spatial configuration of a mechanical system which comprises elastic fibres interacting both with each other and/or with rigid bodies. The configuration is determined by means of the principle of the minimum elastic potential energy of the system. Coulomb friction is neglected at the contacts. The paper gives an overview on the optimal representation of the rigid body shapes in the collison detection problem. In particular, the paper presents an elastic fiber model and describes the rigid body representation adopted. Both have been implemented in the tool. Finally an application of the tool to the biomechanical field is presented which makes it possible to find the spatial configuration of the human ligaments at the ankle joint complex

Sulla qualità di rappresentazione di oggetti approssimati mediante primitive sferiche

Nell’ambito della verifica di collisione fra corpi l’efficienza degli algoritmi gioca un ruolo fondamentale congiuntamente alla precisione nella valutazione dei contatti. Molte delle tecniche adottate in letteratura per risolvere tale problematica si basano sull’approssimazione degli oggetti in studio mediante l’uso di primitive elementari quali, ad esempio, sfere. Efficienza e precisione degli algoritmi sono aspetti strettamente correlati alla qualità di rappresentazione degli oggetti. In questo lavoro viene presentato un nuovo indice che confronta, in termini di qualità di rappresentazione, i differenti algoritmi che approssimano un oggetto mediante primitive sferiche. La validazione dei risultati viene ottenuta attraverso l’analisi ed il confronto con altri indici presenti in letteratura. La validità dell’indice proposto viene infine messa in luce da un’applicazione ad un corpo a geometria complessa quale è la tibiotarsica umana. Both algorithm efficiency and contact evaluation accuracy play a key role when dealing with the problem of Collision Detection. Several techniques from the literature used to solve this problem are based on the object representation by means of spheres. Efficiency and precision of the algorithms are closely connected to the quality of the representation of the objects. In this report, a new index which evaluates the approximation quality of the representation of the object with spheres is presented. Comparing the proposed index with other indexes from previous researches proves its correctness. Finally, as an example of application to a complex geometry bone, from the human ankle highlights the efficiency of the index

Synthesis of Prosthesis Architectures and Design of Prosthetic Devices for Upper Limb Amputees

This chapter presents a procedure for the Determination of the Optimal Prosthesis Architecture for upper limb amputees (DOPA). The presented approach can consistently manage both the clinical aspects and the technical issues involved in the design of electromechanically actuated prostheses. The procedure is composed on one hand of algorithms useful for analyzing the patients\u2019 requirements and on the other hand of algorithms that perform kinematic and kinetostatic simulations of several architectures of artificial arms attempting to fulfil important activities of daily living. The systematic evaluation of the prosthesis models\u2019 performance can methodically guide designers in the synthesis of the optimal prosthesis that best suits the patients\u2019 requirements

State-of-the-Art of Hand Exoskeleton Systems

This paper deals with the analysis of the state-of-the-art of robotic hand exoskeletons (updated at May 2011), which is intended as the first step of a designing activity. A large number of hand exoskeletons (both products and prototypes) that feature some common characteristics and many special peculiarities are reported in the literature. Indeed, in spite of very similar functionalities, different hand exoskeletons can be extremely different for the characteristics of their mechanism architectures, control systems and working principles. The aim of this paper is to provide the reader with a complete and schematic picture of the state-of-the-art of hand exoskeletons. The focus is placed on the description of the main aspects that are involved in the exoskeleton design such as the system kinematics, the actuator systems, the transmission parts and the control schemes. Additionally, the critical issues provided by the literature analysis are discussed in order to enlighten the differences and the common features of different practical solutions. This paper may help to understand both the reasons why certain solutions are proposed for the different applications and the advantages and drawbacks of the different designs proposed in the literature. The motivation of this study is the need to design a new hand exoskeleton for rehabilitation purposes

Theoretical Models for Classical Cepheids: IV. Mean Magnitudes and Colors and the Evaluation of Distance, Reddening and Metallicity

We discuss the metallicity effect on the theoretical visual and near-infrared PL and PLC relations of classical Cepheids, as based on nonlinear, nonlocal and time--dependent convective pulsating models at varying chemical composition. In view of the two usual methods of averaging (magnitude-weighted and intensity-weighted) observed magnitudes and colors over the full pulsation cycle, we briefly discuss the differences between static and mean quantities. We show that the behavior of the synthetic mean magnitudes and colors fully reproduces the observed trend of Galactic Cepheids, supporting the validity of the model predictions. In the second part of the paper we show how the estimate of the mean reddening and true distance modulus of a galaxy from Cepheid VK photometry depend on the adopted metal content, in the sense that larger metallicities drive the host galaxy to lower extinctions and distances. Conversely, self-consistent estimates of the Cepheid mean reddening, distance and metallicity may be derived if three-filter data are taken into account. By applying the theoretical PL and PLC relations to available BVK data of Cepheids in the Magellanic Clouds we eventually obtain Z \sim 0.008, E(B-V) \sim 0.02 mag, DM \sim 18.63 mag for LMC and Z \sim 0.004, E(B-V) \sim 0.01 mag., DM \sim 19.16 mag. for SMC. The discrepancy between such reddenings and the current values based on BVI data is briefly discussed.Comment: 16 pages, 11 postscript figures, accepted for publication on Ap

Integrated process of images and acceleration measurements for damage detection

The use of mobile robots and UAV to catch unthinkable images together with on-site global automated acceleration measurements easy achievable by wireless sensors, able of remote data transfer, have strongly enhanced the capability of defect and damage evaluation in bridges. A sequential procedure is, here, proposed for damage monitoring and bridge condition assessment based on both: digital image processing for survey and defect evaluation and structural identification based on acceleration measurements. A steel bridge has been simultaneously inspected by UAV to acquire images using visible light, or infrared radiation, and monitored through a wireless sensor network (WSN) measuring structural vibrations. First, image processing has been used to construct a geometrical model and to quantify corrosion extension. Then, the consistent structural model has been updated based on the modal quantities identified using the acceleration measurements acquired by the deployed WSN. © 2017 The Authors. Published by Elsevier Ltd