1,721,023 research outputs found
Progetto e realizzazione di una piattaforma scalabile per la robotica mobile
No full textThe main objective of my activity, was to create a mobile platform with a focus on two aspects: teaching
and some particular applications in the real world. Regarding education, the fundamental choice has been
to develop internally most of the components rather than acquire them from third parties; this choice has
encouraged the full knowledge of every single part of the mobot, whether mechanical, hw or sw, leaving
open any future development and replication of the system. The result is a device on which you can
conduct research in mobile robotics and articial intelligence, enabling students to gain experience in the
field of automatic controls at various levels of development: sw, fw, hw and mechanic. As regards the
real world applications, special attention was paid to two areas of employ of these devices: the mobot for
service (i.e trays door mobot, surveillance staff,...) and assistance to disabled and elderly people.
Following are reported some of the main aspects that have characterized SabotOne development.
- The name SabotOne Sabot is the acronym for Scalable mobot (i.e mobile robots). The main focus
which drive the design of each component, was to create a modular system allowing expandability of
mobot.
- Machanics The design of the mechanical parts has been made through the 3D-CAD modeling. All
the parts were then made from aluminum and assembled to form the entire SabotOne device. The
platforms are modular, providing accommodation of the electronics in the lower levels, leaving the
higher ones to specific uses depending on field of use of the mobot. The kinematics of the mobot,
reects the unicycle physical model which provides mobility of the device even in tight spaces and is
very similar to that of wheelchairs for the disabled people.
- Electronics It has been designed and realized a board for electrical axis control in position loop. The
board can control two direct current motors used in the mobot traction. It was realized firmware and
designed the communication protocols in order to make this card appropriate in robotics applications
in which it was used. The board has been equipped with signal condition electronic to provide
acquisition of sensory signals (A/D converter, GPIO). Moreover, three communication protocols
are made available on the board: CAN, TCP/IP (802.11b/g, RJ45) and Modbus on RS485. On
the ethernet interface a web server is available to set conguration parameters board, while the
serial interface enable the board to exchange information with a smart unit such as an embedded-pc
equipped with an operating system.
- Software
{ Development of Sabot Workbench It is a tool that is used to remote monitoring all Sabots
connected to a network. It was developed using the modern framework Eclipse Java-RCP. This
framework has enabled the modeling of all the features of the Workbench through the paradigm
of the plugin. This allows to add functionality to the application without having to modify the
application core.
{ Design of Communication protocol between Workbench and Sabot It is based on Jabber/XMPP protocol and the specification SensML/SWE (designed by Open Geospatial Consor-
tium). It is designed to integrate XMPP (used as information carrier) and SensML/SWE that defines the ontologies for describing measurable phenomena and relative sensors. It has been
dened the concept of identity of a controlled system and integrated within XMPP protocol.
The SensML specification has been extended to support the concept of actuator. The protocol
designed, was denoted with the acronym ControlML.
{ Development of trajectory control, path planning and autolocalization algorithms
Path planning has been developed in C++ implementing LPN algorithm. It was built a sim-
ulator to verify the algorithm efficiency and completeness. It has seen that the algorithm is
complete (can always and a path toward a target qual'ora this exists) and is efficient (planning
a course in less than 100ms over a space partitioned into 10.000 cells). The trajectory control
was achieved by implementing two different algorithms, the first based on pseudoinversion of
dynamic system characterized from non-holonomic constraints, the second conducted by the dy-
namic feedback linearization. It was built a simulator to verify the tracking error of controllers
and we have seen that both controllers are able to undo the following error. For autolocalization,
it has been acquired an inertial platform on which was implemented a Kalman Filter for the
\fusion" of various sensory data (accelerometers, gyroscopes and magnetometers). It has seen
that the inertial data should have to be \merged" with references to absolute position (feature
extracted from images or RFID tag) because of the intrinsic drift of inertial sensors.
{ Development of SabotSabot smart unit software architecture It has been designed and
developed an abstaction of operating system using object oriented paradigm (design pattern)
to decouple the application-level from O.S adopted in this application (linux). It has developed
an architecture that can realize the concept of run-time plugin by lazy-loading of libraries in
linux. In this framework are integrated the algorithms for planning trajectory, for autolocalizing
and avoiding obstacle. The communication protocol ControlML takes care to keep in touch
the Sabots and the control stations with Workbench. The framework was designed in UML
language using strategies oriented to Items and criteria for \Design Pattern" and \Real time
design pattern" inertial sensors
Threshold optimization of all-solid-state Cr:forsterite lasers
No full textThe pumping threshold of a Cr:forsterite laser is lowered by optimizing a double-pass pumping in a sufficiently short crystal. This solution for the first time allows nearly room-temperature Cr:forsterite cw operation with a threshold as low as 330-mW at 1064 nm and permits the laser to be pumped with a single transverse mode vanadate minilaser delivering only 900 mW
Influence of thermal effects in Kerr-lens modelocked femtosecond Cr4+:forsterite lasers
No full textWe report the characterization of a synchronously-pumped Kerr-lens mode-locked (KLM) femtosecond Cr4+:forsterite laser, generating 66 fs pulses at 1240 nm, with 200 mW output power. The influence of the induced thermal lensing on the fast Kerr modulation is analysed by a simple model, which shows that the conventional criteria employed for KLM optimization of Ti:sapphire must be revised when considering the strong thermal effects induced in the Cr4+:forsterite crystal. Indications from our simple model agree with the experimental results
SaBot: a Scalable Architecture for Web-enabled Mobile Robots
No full textThe paper presents the architecture of an experimental mobile robotic platform, which has been designed specifying interoperability between multiple robots as a main objective. In particular, novel software technologies based onWeb services have been exploited in order to support mobile robots with efficient and extensible messaging, data-sharing and distributed task management capabilities. The basic components of the proposed architecture have been implemented and tested on a demonstrative robotic setup, that will be fully described in the paper. However, the aim of the proposal is to contribute to future Web-based interoperability between mobile robots employed in either industrial or human service applications
Efficient all-solid-state tunable source based on a passively Q-switched high-power Nd:YAG Laser
No full textA compact and efficient diode-pumped high power
passively Q-switched Nd:YAG laser has been used to pump
an optical parametric oscillator (OPO) employing periodically
poled lithium niobate (PPLN). The OPO exhibits a threshold
as low as 6.9 uJ, generates 30-ns pulses with energy of
31.7 uJ (pump-to-signal conversion efficiency 30%, pump
depletion 78%) at a 3.8-kHz repetition rate, and is tunable
from 1.46 to 1.56 um
All-solid-state picosecond tunable source of near infrared radiation
No full textA quasi-cw diode-pumped Nd:YAG laser, mode locked by a nonlinear mirror and stabilized by an acousto-optic modulator, has been developed that generates 31-ps, 23-μJ pulses. Employing this source with a periodically poled lithium niobate crystal in a traveling-wave geometry, we obtained extracavity frequency conversion with pump depletion of as much as 62% in the near infrared (1.46– 1.56 μm) with a pulse spectral width of 1.5nm and a beam quality M2=1.7
Intrinsic Electric Oscillations of Ovonic Devices towards the TeraHerz limit
No full textThe time-dependent response of Ovonic devices to an electric potential ramp signal
is analysed by means of an enhanced version of a previously published time-dependent charge-
transport model proposed by the authors. Depending on the inevitable parasitics of the system,
either stable or oscillating solutions are found according to the position of the load line. The
model also allows for speculations on the potential of Ovonic materials in the design of high-
frequency oscillating circuits close to the terahertz range
Transport scaling limits of ovonic Devices: a simulative approach
Full text linkThe transport scaling limits of Ovonic devices are studied by means of a numerical solution of a time- and space-dependent transport models based on a set of equations that provide a good physical grasp of the microscopic process at hand. The predictivity of the approach has been confirmed through the comparison with recent experimental results where the parasitic effects have been reduced by the use of top-technology measuring equipments. The present analysis is performed for the AgInSbTe chalcogenide, since this material exibits a steep threshold-switching dynamics which makes it promising for high-speed non-volatile memory applications
A fifth-order method for 1D device solution
No full textThe so called Numerov process provides an inexpensive, accurate discretization scheme for second-order equations. In this paper the Numerov process has been made applicable to practical cases with typical applications to numerical solution of the coupled Schroedinger Poisson equations. Here the feasibility of the 5-th order method is proved for the longitudinal part of the wave equation
Implementing physical unclonable functions using PCM arrays
Full text linkThe stochastic nature of the switching mechanism of amorphous phase-change memory (PCM) arrays can fruitfully be exploited to implement primitives for hardware security. This paper tackles, by means of PCM, the feasibility of Reconfigurable Physical Unclonable Functions, that constitute one of the two building blocks of cryptographic applications
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