1,721,166 research outputs found
[Preface] : Safety, Fault Diagnosis and Fault Tolerant Control in Aerospace Systems
No full textModern technological and safety-critical systems rely on sophisticated control solutions to meet increased performance
in faulty conditions, reliability and safety requirements. A conventional feedback control design for a complex system
may result in an unsatisfactory performance, or even instability, in the event of malfunctions in actuators, sensors or other
system components. To overcome this limitation, new approaches to control system design have been developed in order
to tolerate component malfunctions while maintaining desirable stability and performance properties. This feature is
particularly important for safety-critical systems, such as aircrafts and spacecrafts. In such plants, the consequences of a
minor (abrupt or incipient) fault in a system component can be catastrophic. Therefore, the demand on reliability, safety,
availability and fault tolerance is generally high. It is necessary to design control strategies that are capable of tolerating
potential faults in order to improve the reliability, safety and availability, while providing desirable performances. These
types of control systems are known as fault tolerant control systems. Particularly, they consist of control systems possessing
the ability to automatically accommodate component faults. They are also capable of maintaining overall system
stability and acceptable performance in the event of such faults. In other words, a closed-loop control system which can
tolerate component malfunctions while maintaining desirable performance and stability properties is considered to be a
fault tolerant control system
Estimation of the Power Coefficient Map for a Wind Turbine System
No full textSince the energy generation capacity of installed wind turbine is increasing, the
interest in optimising the efficiency of these wind turbines is growing, as well. The optimal
operating points for the power and speed control of the turbines depends on a mapping to
the power conversion ratio from tip speed ratio and blade pitch angles. This mapping usually
is not known in analytical form, but in general represented by approximated two–dimensional
maps (i.e. look–up tables). Another issue can derive from the accuracy of the map itself. It
might be correct but uncertain. The main problem of the methods available in the literature is
that the power conversion ratio is represented as two–dimensional map. Therefore, this paper
suggests a scheme to estimate this power conversion ratio in an analytical form, described
as two–dimensional polynomial, whose degree has to be optimised as well. This estimated
analytical relation can subsequently be used to design optimal controller, as well as for robust
fault diagnosis applications
Identification–oriented control designs with application to a wind turbine benchmark
No full textWind turbines are complex dynamic systems forced by stochastic wind disturbances, gravitational, centrifugal, and gyroscopic loads. Since their aerodynamics are nonlinear, wind turbine modelling is thus challenging. Therefore, the design of control algorithms for wind turbines must account for these complexities, but without being too complex and unwieldy. Therefore, the main contribution of this study consists of providing two examples of robust and viable control designs with application to a wind turbine simulator. Due to the description of the considered process, extensive simulations of this test case and Monte–Carlo analysis are the tools for assessing experimentally the achieved features of the suggested control schemes, in terms of reliability, robustness, and stability, in the presence of modelling and measurement errors. These developed control methods are finally compared with different approaches designed for the same benchmark, in order to evaluate the properties of the considered control techniques
Fault Diagnosis for Aircraft System Models: An Introduction from Fault Detection to Fault Tolerance
No full textSafety in aircraft systems is a concern of rising importance, especially due to the sophisticated control devices exploited to improve the overall system performance, including both digital designs and complex hardware (input-output sensors, actuators, and components). Thus, control systems must include automatic supervision tasks to diagnose incipient malfunctions, as early as possible. This book focuses on the design of robust linear and nonlinear dynamic filters, obtained via model-based and analytical approaches for fault diagnosis and identification. The problem is treated in all its aspects covering: nonlinear modelling of aircraft systems; design of disturbance decoupled dynamic filters for residual generation; fault detection and estimation, fault tolerant control. Sample case studies are used to demonstrate the application of these techniques to high fidelity flight simulators. This book will be of interest to researchers in aircraft fault tolerant control, fault detection and diagnosis. Aircraft control engineers interested in applying the latest methods in fault detection and diagnosis will benefit from the simulation examples
A Nonlinear Guidance and Active Fault Tolerant Control System for a Fixed Wing Unmanned Aerial Vehicle
No full textBy using an interactive architecture of
independently designed guidance and active fault tolerant
control systems, this work proposes the development of a novel
Guidance and Active Fault Tolerant Control Scheme
(GAFTCS) for a fixed wing Unmanned Aerial Vehicle (UAV).
As to the guidance segment, an approach, of the Feedback
Linearisation (FL) type, has been exploited for developing,
directly on the dynamic model of the fixed wing UAV, the
guidance system. With reference to the control segment, this
paper proposes an AFTCS methodology based on Adaptive
Filters designed by means of the Non Linear Geometric
Approach (AF-NLGA). The aim of the AF-NLGA is to provide
a fault estimate, which is used in a further control loop, thus
avoiding a logic-based switching controller. The simulation
results show good tracking capabilities, asymptotic fault
accommodation, and control objective recovery for the overall
GAFTCS
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
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
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