1,720,965 research outputs found
Trajectory tracking for a Non-Conventional UAV
No full textThe aim of the present paper is the design of a
flight control system for a Tandem – Canard
UAV, useful in the whole flight envelope, both
Out of Ground Effect (OGE) and In Ground
Effect (IGE) conditions. Because of the
particular arrangement of the studied aircraft, a
general mathematical model has been built in
order to obtain non-linear analytical equations
for longitudinal aerodynamic coefficients both
in OGE and in IGE flight. So the dynamic
behaviour of the UAV may be studied during
every flight phases i.e. in the whole range of
altitude. To consider the strong variation of
aerodynamic parameters due to the ground
effect presence, a robust control technique
(LQG/LTR) has been used to design the control
system. Because Phugoid mode is strongly
affected by ground effect, a Stability
Augmentation System has been implemented in
order to increase Phugoid damping. The
controller has shown suitability to track both
out of ground effect and in ground effect
trajectories. Besides, it possesses robustness
properties either in presence of wind
disturbances
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
I WIG’s: MEZZI INNOVATIVI PER IL TRASPORTO CIVILE Un’ipotesi di impiego per i collegamenti a medio raggio nel Mediterraneo
No full textDynamic Stability in Ground Effect of a non Conventional UAV in Antisubmarine Surveillance Operations
No full text
A Non Conventional UAV In Ground Effect: Synthesis of a Robust Flight Control System,
No full textABSTRACT
This paper discusses the synthesis of an Extended Kalman Filter (EKF) to perform both wind velocities and state
estimation for a non conventional UAV flying in ground effect. Since, in IGE flight, motions into the symmetry
plane are of primary concern, the study focuses on the longitudinal aircraft dynamics. The proposed estimator
requires measurement of few flight variables, easily obtainable by means of conventional sensors; besides, it
does not use Inertial Measurement Unit (IMU). To simulate a low cost sensing equipment, the model outputs are
corrupted by white noise of relatively high standard deviation. Furthermore, to cope with the low rate of the
GPS with respect to the other sensors, the EKF algorithm is modified to allow for a dual rate measurement
model. State propagation is obtained by means of an accurate, highly non-linear mathematical model of the
UAV dynamics which allows to cope with both the non conventional configuration and ground effect. Combined
estimation of the UAV state and wind velocity is obtained by augmenting the system state vector with the wind
velocity components. Numerical simulations show the effectiveness of the proposed method in widely different
maneuvering conditions mixing IGE and OGE flight stages and in presence of largely dissimilar wind
disturbance characteristics. The performance advantages with respect to a classical, computationally simpler
estimation scheme are also highlighted. Closed loop simulations have shown the suitability of the obtained state
estimates for control purposes
A NON CONVENTIONAL UAV IN GROUND EFFECT: ESTIMATION OF STATE AND TURBULENCE VIA EXTENDED KALMAN FILTER
No full textABSTRACT
This paper discusses the synthesis of an Extended Kalman Filter (EKF) to perform both wind velocities and state
estimation for a non conventional UAV flying in ground effect. Since, in IGE flight, motions into the symmetry plane are
of primary concern, the study focuses on the longitudinal aircraft dynamics. The proposed estimator requires
measurement of few flight variables, easily obtainable by means of conventional sensors; besides, it does not use
Inertial Measurement Unit (IMU). To simulate a low cost sensing equipment, the model outputs are corrupted by white
noise of relatively high standard deviation. Furthermore, to cope with the low rate of the GPS with respect to the other
sensors, the EKF algorithm is modified to allow for a dual rate measurement model. State propagation is obtained by
means of an accurate, highly non-linear mathematical model of the UAV dynamics which allows to cope with both the
non conventional configuration and ground effect. Combined estimation of the UAV state and wind velocity is obtained
by augmenting the system state vector with the wind velocity components. Numerical simulations show the effectiveness
of the proposed method in widely different maneuvering conditions mixing IGE and OGE flight stages and in presence
of largely dissimilar wind disturbance characteristics. The performance advantages with respect to a classical,
computationally simpler estimation scheme are also highlighted. Closed loop simulations have shown the suitability of
the obtained state estimates for control purposes
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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