1,721,174 research outputs found
Natural interface for interactive virtual assembly in augmented reality using Leap Motion Controller
No full textIn this paper, an augmented reality methodology based on the use of a low-invasiveness hand tracking device is presented.
The developed methodology, allows the user to be visually immersed into an augmented scene by means of a head-mounted
display. He can interact with the virtual objects without any wearable sensor using the Leap Motion Controller that is able to
acquire the pose of each finger of both hands by optical triangulation without markers. In this way, the interaction between
the user and the scene can be considered “natural”. The interaction between hands and objects and the assembling among
objects is achieved by the modification of the Object Active Feature–Grasping Active Feature methodology, based on the
use of algebraic kinematic constraint equations. The approach has been adapted to take into account the specific information
coming from the tracking device. An example of implementation is reported and an experimental usability study discussed
Classic Matrix Decompositions in Clifford Algebra with Applications to Kinematic Analysis
No full textOne of the advantages of dual algebra is the capability to express in elegant and
compact notation operations and transformations on geometric algebra objects.
This capability proved to be useful in different areas of engineering such as
kinematics, dynamics, robot vision and computer graphics.
This paper addresses the problem of extending the QR, SVD and LU matrix
decompositions to the field of dual numbers. The availability of these new
computational tools should give the possibility of a wider use of Clifford algebra
in engineering.
The results herein presented are based on the solution of Sylvester type of
linear matrix equations. The need of new variable types or overload operators
is avoided. Only standard linear algebra library routines are required.
Although they have a general validity, the algorithms herein presented are
applied to screw motion estimation from body points coordinates and to kinematic
synthesis of the function generator RCCC spatial linkage.
For a ready use of the matrix algorithms herein proposed, MATLAB source
code is listed in the Appendix
Accuracy in fingertip tracking using Leap Motion Controller for interactive virtual applications
No full textThe paper deals with an experimental assessment
of the Leap Motion Controller®. This device is able to
track the user’s hands in a real environment. Due to lowinvasiveness
and easiness of use, it is promising for the
integration in virtual or augmented reality, research and entertainment
scenarios. The assessment is performed in a real
context using volunteers that were asked to point with the
fingertips to a set of predefined locations in space. A specific
test rig has been designed and built. It is comprised of a transparent
plate supported by adjustable pillars and mounted over
the Leap. The data are processed to assess the errors in tracking
the five fingertips of the right hand. Results show that
the accuracy and precision of the Leap is suitable for robust
tracking of the user’s hand. The results also unveil that there
are preferable zones in which the tracking performance is
better
Kinematics and Enumeration of Combined Harmonic Drive Gearing
No full textThe combined harmonic drive (HD) gearing is a class of differential gears composed of
traditional and HD gears. In this paper, the kinematic analysis and enumeration of these
less known gear devices are discussed. In particular, a new graph-based method of kinematic
analysis has been developed. In order to stimulate the diffusion and applications of
combined HD gearing, an atlas of structurally nonisomorphic gear trains has been
compiled
Modellazione interattiva integrando realtà aumentata, morphing geometrico e interfacce aptiche
No full textL’articolo discute i principali risultati del progetto di ricerca RBF4ARTIST. L’obiettivo del progetto è lo studio e l’implementazione di una metodologia per permettere la modifica interattiva delle forme geometriche con funzionalità. Tale metodologia combina le potenzialità della realtà aumentata, di efficienti algoritmi di deformazione geometrica e l’uso di interfacce aptiche a ritorno di forza. La metodologia può essere impiegata per affrontare la modifica di geometrie in problemi di ingegneria come la prototipazione virtuale e l’ottimizzazione. Lo strumento permette al progettista di modificare interattivamente delle geometrie esistenti mediante il contatto con le relative rappresentazioni virtuali, potendo sentire un feedback tattile. Il cuore della metodologia si basa sull’impiego di un modellatore basato sulle radial basis functions (RBF) ottimizzato per funzionare in tempo reale. Tali algoritmi numerici sono integrati in un ambiente di realtà aumentata che ne conferisce il carattere realistico e immersivo e sono coadiuvati dall’uso di un dispositivo aptico che permette l’interazione tattile
An improved three-dimensional multibody model of the human spine for vibrational investigations
No full textIn this paper, a three dimensional numerical model of the human spine, specialized
for vibrational investigations, is presented. The model has been built using multibody
dynamics techniques and includes the entire set of vertebrae, considered as rigid bodies. The
interaction between vertebrae has been simulated using six component bushings, without the
need of any kinematic constraint. This methodology allows a very relevant flexibility, and
the fully three-dimensional deformation modes of the spine may be studied. The investigation
has been focused on the assessment of the vibration modes and the computation of the
transmissibility functions buttocks-to-head for acceleration inputs along three main directions.
It has been observed that the first torsional modes with a relevant mass participation
factors are present at very low frequencies. Most of the relevant modes, which involve the
deformation of the spine with relevant participation factor, are within the range 0÷5 Hz.
These peaks are also visible in the transmissibility functions. Results have been also compared
to those of other experimental and numerical studies
Elasto-kinematic comparison of flexure hinges undergoing large displacement
No full textThe design of precision compliant mechanisms requires the assessment of the elasto-kinematic
characteristics of the flexure hinges connecting bulky parts. Due to geometrical nonlinearities, a
comprehensive analysis requires the functional properties to be evaluated within the feasible
range of relative displacement. This investigation proposes the use of kinematic invariants to
characterize the main features of a compliant mechanism. In particular, this paper offers the
comparison of five common flexure hinges in terms of the relative motion kinematic invariants.
By using the dynamic spline formulation, for each hinge typology, a flexible multibody model is
developed to obtain the fixed and moving centrodes and the diameter of the inflection circle of
the relative motion. In order to fully characterize the elasto-kinematic behaviour, the simulative
models are also used to compute the equivalent stiffness as a function of the rotation angle. The
results show that the differences among the various types of hinges is relevant in terms of both
kinematic and compliance characteristics. The findings and the methodology herein outlined are
new tools for the optimal design and synthesis of flexure joints
Some Considerations on the Setup of Pseudo-Rigid Body Models for Single-Leaf Flexure Hinges in Compliant Mechanisms
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