1,720,978 research outputs found
Differential geometry based active fault tolerant control for aircraft
No full textThis work shows how to use a differential geometry tool to design a novel nonlinear active fault tolerant flight control system for aircraft. The proposed control scheme consists of two main subsystems: a controller, which is designed for the nominal plant, and a fault detection and diagnosis module, which
provides fault estimation. A further feedback loop exploits the fault estimation to accommodate faults affecting the system. The estimate convergence and the stability of the active fault tolerant flight controller are theoretically proved. Finally, high fidelity simulations show the effectiveness of the scheme
Fault Tolerant Control Schemes for Nonlinear Models of Aircraft and Spacecraft: Preliminary Results
No full textThis paper explains the design method of an innovative active fault tolerant control
scheme and the achieved results regarding its application to aerospace nonlinear models. The
proposed method keeps the already in–place control and guidance laws and adds a feedback
loop that accommodates the fault. The kernel of this active fault tolerant control consists in
the fault detection and diagnosis module projected by using the non–linear geometric approach.
Thanks to this approach fault estimate are analytically decoupled from both other faults and
disturbances. The novel active fault tolerant control has been tested by using high fidelity
simulators of aircraft and spacecraft systems and the performance show the method’s robustness
with respect to disturbance effects and measurement errors. The results obtained demonstrate
how the proposed design methodology could be a successful approach for the reliable design of
fault tolerant control schemes in real aircraft and spacecraft applications
Fault Tolerant Control Schemes for Nonlinear Models of Aircraft and Spacecraft Systems
No full textThis paper explains the design method of an innovative active fault tolerant control
scheme and the achieved results regarding its application to aerospace nonlinear models. The
proposed method keeps the already in–place control and guidance laws and adds a feedback
loop that accommodates the fault. The kernel of this active fault tolerant control consists of
the fault detection and diagnosis module designed by using the nonlinear geometric approach.
Thanks to this approach fault estimates are analytically decoupled from both the other
faults and disturbances. The novel active fault tolerant control has been tested by using high
fidelity simulators of aircraft and spacecraft systems, whilst the performances show the method
robustness with respect to disturbance effects and measurement errors. The results obtained
demonstrate how the proposed design methodology could be a successful approach for the
reliable design of fault tolerant control schemes in real aircraft and spacecraft application
Active Fault Tolerant Control of Nonlinear Systems: the Cart–Pole example
No full textThis paper describes an active fault tolerant control scheme that is developed
for nonlinear systems. The methodology is based on a fault detection and diagnosis procedure
relying on adaptive filters designed via the nonlinear geometric approach. The controller
reconfiguration exploits directly the on–line estimate of the fault signal. The classical model
of an inverted pendulum on a cart is considered as an application example, in order to highlight
the feasibility and the efficiency of the proposed approach
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Satellite Attitude Active FTC Based On Geometric Approach and RBF Neural Network
No full textThis paper proposes a novel satellite attitude Active Fault Tolerant Control System. The Active Fault Tolerant Control System is based on a Fault Detection and Diagnosis module providing fault estimates decoupled from the aerodynamic disturbance thanks to the application of the NonLinear Geometric Approach. The diagnosis module is a bank of adaptive filters based on a Radial Basis Function Neural Network. The controller reconfiguration exploits directly the on-line estimates of the fault signals. To the authors' knowledge, the joint use of the NonLinear Geometric Approach and Radial Basis Function Neural Network is not
present in literature. The use of a Radial Basis Function Neural Network allows to design generalized fault estimation filters which do not need any a priori
information about the fault internal model. The use of the NonLinear Geometric Approach allows to obtain very accurate fault estimates, independently from
the knowledge of the aerodynamic disturbance parameters. Extensive simulation results based on a detailed nonlinear satellite attitude model embedding
disturbance description are given. The obtained results highlight that the proposed satellite Active Fault Tolerant Control System can deal with reaction
wheel faults of different types (i.e. step faults, ramp faults, sinusoidal faults) thus obtaining good attitude control performances
Active Fault Tolerant Control System for a High Accuracy Planet–Image and Stellar–Pointing Satellite
No full textThis paper focuses on the problem of nonlinear fault detection, diagnosis, and fault tolerant control for a satellite model through the construction of disturbance decoupled
adaptive filters designed via the nonlinear geometric approach. Each filter of the bank is sensitive
to all but one fault, and decoupled from aerodynamic disturbances. In order to fulfil the
requirements of the proposed mission, the disturbance decoupling represents the key point,
since the aerodynamic model is often uncertain. To the authors’ knowledge, this is the first
work presenting the solution of the aerodynamic disturbance decoupling problem. The controller
reconfiguration logic exploits a further control loop depending on the on–line estimate of the
fault signals. Simulations results for the case of a nonlinear satellite model with aerodynamic,
gravitational, magnetic, and solar pressure disturbances are presented with reference to a
pointing mission. The suggested approach allows to achieve better performances with respect
to control schemes simply designed to be robust with respect to the considered disturbance
contributions
Variations on the Author
Full text link“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
Fault Diagnosis and Control Reconfiguration in Earth Satellite Model Engines
No full textThis paper presents the design strategies used to develop a supervision scheme for
the attitude control system of an earth satellite model. The main point regards the handling of
faults affecting the satellite engines, i.e. how to detect and isolate faults, and how to prevent
propagation into failures with potential mission loss as a consequence. Thus, this work develops
a comprehensive scheme for fault detection, isolation and recovery of the engines for a spacecraft
attitude control, based on the earth satellite model. As the present study focuses on an earth
satellite model, robustness is achieved by exploiting almost known disturbance models and an
explicit disturbance de–coupling method. The achieved results demonstrate how the proposed
methodology can constitute a successful approach for real application in future spacecraf
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