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ESEO spacecraft: FMEA (Failure Mode and Effects Analysis) and FDIR (Fault Detection Isolation and Recovery) / FMEA (Failure Mode Effects Analysis) ed FDIR (Fault Detection Isolation and Recovery) per la piattaforma satellitare E.S.E.O.Ferroni, Matteo Alberto <1985> 06 May 2016 (has links)
The purpose of the present doctoral activities concern the reliability of electronic systems and their fault tolerance. The main field of application whose is addressed this research is the aerospace industry, in particular it has been developed around the E.S.E.O. (European Student Earth Orbiter) spacecraft/mission. The implementation of COTS (Components Off The Shell) electronic components, military industrial grade, ensured a considerable saving in terms of costs with minimal impact on the final performance of the system. In order to reach the objective: the mission success (operative spacecraft for at least six months), it has been performed an FMEA analysis at system and subsystem level and a full test campaign useful to define and develop the hierarchical and distributed FDIR strategy here exposed.
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Meccanismi piani con gioco: luoghi ad errore di posizione massimo costanteCocconcelli, Marco <1977> 22 May 2007 (has links)
No description available.
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Analisi e sintesi di meccanismi spaziali per lo studio del moto passivo del ginocchio umanoOttoboni, Andrea <1977> 22 May 2007 (has links)
No description available.
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Progetto e realizzazione del sistema di navigazione guida e controllo per un elicottero con capacità di volo autonomoPretolani, Roberto <1976> 15 June 2007 (has links)
No description available.
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Progetto e realizzazione del sistema di gestione autonoma del volo e controllo in remoto per un velivolo UAV ad ala rotanteTeodorani, Barbara <1969> 15 June 2007 (has links)
This PhD thesis presents the results, achieved at the Aerospace Engineering Department
Laboratories of the University of Bologna, concerning the development of a small scale
Rotary wing UAVs (RUAVs).
In the first part of the work, a mission simulation environment for rotary wing UAVs was
developed, as main outcome of the University of Bologna partnership in the CAPECON
program (an EU funded research program aimed at studying the UAVs civil applications and
economic effectiveness of the potential configuration solutions). The results achieved in
cooperation with DLR (German Aerospace Centre) and with an helicopter industrial partners
will be described.
In the second part of the work, the set-up of a real small scale rotary wing platform was
performed. The work was carried out following a series of subsequent logical steps from
hardware selection and set-up to final autonomous flight tests.
This thesis will focus mainly on the RUAV avionics package set-up, on the onboard
software development and final experimental tests.
The setup of the electronic package allowed recording of helicopter responses to pilot
commands and provided deep insight into the small scale rotorcraft dynamics, facilitating the
development of helicopter models and control systems in a Hardware In the Loop (HIL)
simulator. A neested PI velocity controller1 was implemented on the onboard computer and
autonomous flight tests were performed. Comparison between HIL simulation and experimental results showed good agreement.
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Fault detection in rotating machines by vibration signal processing techniquesD'Elia, Gianluca <1980> 17 April 2008 (has links)
Machines with moving parts give rise to vibrations and consequently noise. The setting up and
the status of each machine yield to a peculiar vibration signature. Therefore, a change in the
vibration signature, due to a change in the machine state, can be used to detect incipient
defects before they become critical. This is the goal of condition monitoring, in which the
informations obtained from a machine signature are used in order to detect faults at an early
stage. There are a large number of signal processing techniques that can be used in order to
extract interesting information from a measured vibration signal.
This study seeks to detect rotating machine defects using a range of techniques including
synchronous time averaging, Hilbert transform-based demodulation, continuous wavelet
transform, Wigner-Ville distribution and spectral correlation density function. The detection
and the diagnostic capability of these techniques are discussed and compared on the basis of
experimental results concerning gear tooth faults, i.e. fatigue crack at the tooth root and tooth
spalls of different sizes, as well as assembly faults in diesel engine. Moreover, the sensitivity
to fault severity is assessed by the application of these signal processing techniques to gear
tooth faults of different sizes.
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A new approach for the dynamic modelling of the human kneeSancisi, Nicola <1979> 17 April 2008 (has links)
Mathematical models of the knee joint are important tools which have both
theoretical and practical applications. They are used by researchers to fully understand
the stabilizing role of the components of the joint, by engineers as an aid for
prosthetic design, by surgeons during the planning of an operation or during the
operation itself, and by orthopedists for diagnosis and rehabilitation purposes.
The principal aims of knee models are to reproduce the restraining function of
each structure of the joint and to replicate the relative motion of the bones which
constitute the joint itself. It is clear that the first point is functional to the second
one. However, the standard procedures for the dynamic modelling of the knee
tend to be more focused on the second aspect: the motion of the joint is correctly
replicated, but the stabilizing role of the articular components is somehow lost.
A first contribution of this dissertation is the definition of a novel approach —
called sequential approach — for the dynamic modelling of the knee. The procedure
makes it possible to develop more and more sophisticated models of the
joint by a succession of steps, starting from a first simple model of its passive motion.
The fundamental characteristic of the proposed procedure is that the results
obtained at each step do not worsen those already obtained at previous steps, thus
preserving the restraining function of the knee structures.
The models which stem from the first two steps of the sequential approach are
then presented. The result of the first step is a model of the passive motion of
the knee, comprehensive of the patello-femoral joint. Kinematical and anatomical
considerations lead to define a one degree of freedom rigid link mechanism, whose
members represent determinate components of the joint. The result of the second
step is a stiffness model of the knee. This model is obtained from the first one, by
following the rules of the proposed procedure. Both models have been identified
from experimental data by means of an optimization procedure. The simulated
motions of the models then have been compared to the experimental ones.
Both models accurately reproduce the motion of the joint under the corresponding
loading conditions. Moreover, the sequential approach makes sure the results
obtained at the first step are not worsened at the second step: the stiffness model
can also reproduce the passive motion of the knee with the same accuracy than the
previous simpler model.
The procedure proved to be successful and thus promising for the definition of
more complex models which could also involve the effect of muscular forces.
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Topological analysis of singularity loci for serial and parallel manipulatorsPaganelli, Davide <1979> 17 April 2008 (has links)
Singularities of robot manipulators have been intensely studied in the last
decades by researchers of many fields. Serial singularities produce some local loss of
dexterity of the manipulator, therefore it might be desirable to search for singularityfree
trajectories in the jointspace. On the other hand, parallel singularities are very
dangerous for parallel manipulators, for they may provoke the local loss of platform
control, and jeopardize the structural integrity of links or actuators. It is therefore
utterly important to avoid parallel singularities, while operating a parallel machine.
Furthermore, there might be some configurations of a parallel manipulators that are
allowed by the constraints, but nevertheless are unreachable by any feasible path.
The present work proposes a numerical procedure based upon Morse theory,
an important branch of differential topology. Such procedure counts and identify the
singularity-free regions that are cut by the singularity locus out of the configuration
space, and the disjoint regions composing the configuration space of a parallel
manipulator. Moreover, given any two configurations of a manipulator, a feasible or
a singularity-free path connecting them can always be found, or it can be proved that
none exists.
Examples of applications to 3R and 6R serial manipulators, to 3UPS and
3UPU parallel wrists, to 3UPU parallel translational manipulators, and to 3RRR
planar manipulators are reported in the work.
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Path planning for image based visual servoingFioravanti, Duccio <1979> 17 April 2008 (has links)
This thesis deals with Visual Servoing and its strictly connected disciplines like projective
geometry, image processing, robotics and non-linear control. More specifically the
work addresses the problem to control a robotic manipulator through one of the largely
used Visual Servoing techniques: the Image Based Visual Servoing (IBVS). In Image
Based Visual Servoing the robot is driven by on-line performing a feedback control loop
that is closed directly in the 2D space of the camera sensor. The work considers the case
of a monocular system with the only camera mounted on the robot end effector (eye
in hand configuration). Through IBVS the system can be positioned with respect to a
3D fixed target by minimizing the differences between its initial view and its goal view,
corresponding respectively to the initial and the goal system configurations: the robot
Cartesian Motion is thus generated only by means of visual informations.
However, the execution of a positioning control task by IBVS is not straightforward because
singularity problems may occur and local minima may be reached where the reached
image is very close to the target one but the 3D positioning task is far from being fulfilled:
this happens in particular for large camera displacements, when the the initial and the
goal target views are noticeably different.
To overcame singularity and local minima drawbacks, maintaining the good properties of
IBVS robustness with respect to modeling and camera calibration errors, an opportune
image path planning can be exploited. This work deals with the problem of generating
opportune image plane trajectories for tracked points of the servoing control scheme (a
trajectory is made of a path plus a time law). The generated image plane paths must be
feasible i.e. they must be compliant with rigid body motion of the camera with respect
to the object so as to avoid image jacobian singularities and local minima problems. In
addition, the image planned trajectories must generate camera velocity screws which are
smooth and within the allowed bounds of the robot. We will show that a scaled 3D motion
planning algorithm can be devised in order to generate feasible image plane trajectories.
Since the paths in the image are off-line generated it is also possible to tune the planning
parameters so as to maintain the target inside the camera field of view even if, in some
unfortunate cases, the feature target points would leave the camera images due to 3D
robot motions.
To test the validity of the proposed approach some both experiments and simulations
results have been reported taking also into account the influence of noise in the path
planning strategy. The experiments have been realized with a 6DOF anthropomorphic
manipulator with a fire-wire camera installed on its end effector: the results demonstrate
the good performances and the feasibility of the proposed approach.
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Design, implementation and tests of Real-time Feed-forward controller and navigation system for a small scale UAV helicopterZanetti, Filippo <1973> 17 April 2009 (has links)
No description available.
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