Flight Mechanics And Flight Control For A Multibody Aircraft
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Flight Mechanics And Flight Control For A Multibody Aircraft
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Author : Köthe, Alexander
language : en
Publisher: Universitätsverlag der TU Berlin
Release Date : 2019-06-26
Flight Mechanics And Flight Control For A Multibody Aircraft written by Köthe, Alexander and has been published by Universitätsverlag der TU Berlin this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-06-26 with Science categories.
Aircraft operating as so-called High Altitude Platform Systems (HAPS) have been considered as a complementary technology to satellites since several years. These aircraft can be used for similar communication and monitoring tasks while operating at a fraction of the cost. Such concepts have been successfully tested. Those include the AeroVironment Helios and the Airbus Zephyr, with an endurance of nearly 624 hours (26 days). All these HAPS aircraft have a high-aspect-ratio wing using lightweight construction. In gusty atmosphere, this results in high bending moments and high structural loads, which can lead to overloads. Aircraft crashes, for example from Google’s Solara 50 or Facebook’s Aquila give proof of that fact. Especially in the troposphere, where the active weather takes place, gust loads occur, which can lead to the destruction of the structure. The Airbus Zephyr, the only HAPS aircraft without flight accidents, provides only a very small payload. Thus it does not fully comply with the requirements for future HAPS aircraft. To overcome the shortcomings of such single-wing aircraft, so-called multibody aircraft are considered to be an alternative. The concept assumes multiple aircraft connected to each other at their wingtips. It goes back to the German engineer Dr. Vogt. In the United States, shortly after the end of World War II, he experimented with the coupling of manned aircraft. This resulted in a high-aspect-ratio wing for the aircraft formation. The range of the formation could be increased correspondingly. The engineer Geoffrey S. Sommer took up Vogt’s idea and patented an aircraft configuration consisting of several unmanned aerial vehicles coupled at their wingtips. However, the patent does not provide any insight into the flight performance, the flight mechanical modeling or the control of such an aircraft. Single publications exist that deal with the performance of coupled aircraft. A profound, complete analysis, however, is missing so far. This is where the present work starts. For the first time, a flying vehicle based on the concept of the multibody aircraft will be analyzed in terms of flight mechanics and flight control. In a performance analysis, the aircraft concept is analyzed in detail and the benefits in terms of bending moments and flight performance are clearly highlighted. Limits for operation in flight are shown considering aerodynamic optimal points. The joints at the wingtips allow a roll and pitch motion of the individual aircraft. This results in additional degrees of freedom for the design through the implementation of different relative pitch and bank angles. For example, using individual pitch angles for individual aircraft further decreases the induced drag and increases flight performance. Because the lift is distributed symmetrically, but not homogenously along the wingspan, a lateral trim of the individual aircraft in formation flight becomes necessary. The thesis presents a new method to implement this trim by moving the battery mass along half the wingspan, which avoids additional parasite drag. Further, a complete flight dynamics model is provided and analyzed for aircraft that are mechanically connected at their wingtips. To study this model in detail, a hypothetical torsional and bending spring between the aircraft is introduced. If the spring constants are very high, the flight dynamics model has properties similar to those of an elastic aircraft. Rigid-body and formation eigenmotions can be clearly distinguished. If the spring constants are reduced towards zero, which represents the case of the multibody aircraft, classical flight mechanics eigenmotions and modes resulting from the additional degrees of freedom are coupled. This affects the eigenstructure of the aircraft. Hence, normal motions with respect to the inertial space as known from a rigid aircraft cannot be observed anymore. The plant also reveals unstable behavior. Using the non-linear flight dynamics model, flight controllers are designed to stabilize the plant and provide the aircraft with an eigenstructure similar to conventional aircraft. Different controller design methods are used. The flight controller shall further maintain a determined shape of the flight formation, it shall control flight, bank and pitch angles, and it shall suppress disturbances. Flight control theories in the time domain (Eigenstructure assignment) and in the frequency domain (H-infinity loop-shaping) are considered. The resulting inner-control loops yield a multibody aircraft behavior that is similar to the one of a rigid aircraft. For the outer-control loops, classical autopilot concepts are applied. Overall, the flight trajectory of the multibody aircraft above ground is controlled and, thus, an actual operation as HAPS is possible. In the last step, the flight controller is successfully validated in non-linear simulations with complete flight dynamics. Flugzeuge in der Form von sogenannten Höhenplattformen (engl. High-Altitude Platform Systems, HAPS) werden seit einigen Jahren als kostengünstige Ergänzung zu teuren Satelliten betrachtet. Diese Flugzeuge können für ähnliche Kommunikations- und überwachungsaufgaben eingesetzt werden. Zu den gegenwärtigen Konzepten solcher Fluggeräte, die bereits erfolgreich im Flugversuch eingesetzt wurden, zählen der Helios von AeroVironment und der Airbus Zephyr, der eine Flugdauer von fast 624 Stunden (26 Tagen) erreicht hat. Alle diese HAPS-Flugzeuge besitzen einen Flügel langer Streckung, der in Leichtbauweise konstruiert ist. Hieraus resultieren in böiger Atmosphäre hohe Biegemomente und starke strukturelle Belastungen, die zu überbelastungen führen können. Flugunfälle beispielsweise von Googles Solara 50 oder Facebooks Aquila belegen dies. Insbesondere in der Troposphäre, in der das aktive Wetter stattfindet, treten Böenlasten auf, die die Struktur zerstören können. Der Airbus Zephyr, der bisher als einziges HAPS-Flugzeug frei von Flugunfällen ist, besitzt nur eine sehr geringe Nutzlast. Daher kann er die Anforderungen an zukünftige HAPS-Flugzeuge nicht vollständig erfüllen. Um die Schwachstellen solcher Ein-Flügel-Konzepte zu überwinden, wird in dieser Arbeit ein alternatives Flugzeugkonzept betrachtet, das als Mehrkörperflugzeug bezeichnet wird. Das Konzept geht von mehreren, an den Flügelspitzen miteinander verbundenen Flugzeugen aus und beruht auf Ideen des deutschen Ingenieurs Dr. Vogt. Dieser hatte in den USA kurz nach Ende des Zweiten Weltkrieges bemannte Flugzeuge aneinanderkoppeln lassen. Hierdurch ergab sich ein Flugzeugverbund mit einem Flügel langer Streckung. Damit konnte die Reichweite des Verbundes gesteigert werden. Geoffrey S. Sommer griff die Idee von Vogt auf und lies sich eine Flugzeugkonfiguration patentieren, die aus mehreren, unbemannten Flugzeugen besteht, die an den Enden der Tragflächen miteinander gekoppelt sind. Die Patentschrift gibt jedoch keinen Einblick in die Flugleistungen, die flugmechanische Modellierung oder die Regelung eines solchen Fluggerätes. Vereinzelt existieren Veröffentlichungen, die sich mit den Flugleistungen von gekoppelten Luftfahrzeugen beschäftigen. Eine tiefgreifende, vollständige flugmechanische Analyse fehlt jedoch bisher. Hier setzt die vorliegende Arbeit an. Ein Fluggerät basierend auf dem Konzept des Mehrkörperflug-zeugs wird erstmalig hinsichtlich der Flugmechanik und Flugregelung untersucht. In einer Flugleistungsbetrachtung wird das Flugzeugkonzept genau analysiert und die Vorteile hinsichtlich der Biegemomente und der Flugleistungen klar herausgestellt. Die Grenzen des Einsatzes im Flugbetrieb werden mithilfe aerodynamischer Optimalpunkte aufgezeigt. über die Lager an den Flügelspitzen, die eine relative Roll- und Nickbewegung der Flugzeuge untereinander ermöglichen, ergeben sich durch die Einstellung unterschiedlicher Längslage- und Hängewinkel zusätzliche Freiheitsgerade im Entwurf. Die Verwendung unterschiedlicher Nicklagewinkel der einzelnen Flugzeuge reduziert beispielsweise den induzierten Widerstand weiter und steigert die Flugleistung. Durch die symmetrische, entlang der Spannweite jedoch nicht homogene Auftriebsverteilung ist auch eine laterale Trimmung der einzelnen Flugzeuge in der Formation notwendig. Hier stellt die Arbeit eine neuartige Möglichkeit vor, um diese Trimmung ohne zusätzlichen parasitären Widerstand mittels Verschiebung der Batteriemasse entlang der Halbspannweite umzusetzen. Weiterhin wird ein vollständiges flugdynamisches Modell für über mechanische Lager verbundene Luftfahrzeuge aufgestellt und analysiert. Für diese Analyse wird eine hypothetische Torsions- und Biegefeder zwischen den Flugzeugen modelliert. Sind die Federsteifigkeiten hinreichend hoch, besitzt das flugdynamische Modell Eigenschaften, die einem elastischen Flugzeug entsprechen. Starrkörper- und elastische Eigenbewegungsformen sind in diesem Fall klar separiert. Bei immer weiterer Reduzierung, bis auf eine Federsteifigkeit von Null, kommt es zu Kopplungen zwischen den klassischen, flugmechanischen Eigenbewegungsformen und den Moden aus den zusätzlichen Freiheitsgraden. Dies stellt den Auslegungsfall für das Mehrkörperflugzeug dar. Hierbei verändert sich die Eigenstruktur (engl. eigenstructure) des Flugzeugs und normale, bei einem starren Flugzeug beobachtbare Bewegungen gegenüber dem inertialen Raum sind nicht mehr erkennbar. Zusätzlich zeigt die Strecke instabiles Verhalten. Basierend auf dem nichtlinearen, flugdynamischen Modell werden mit verschiedenen Methoden Regler entworfen, die die Regelstrecke stabilisieren und dem Flugzeug eine Streckenstruktur zuweisen, die derjenigen klassischer Flugzeuge ähnelt. Zudem soll durch die Regler eine vorgegebene Form des Flugzeugverbundes beibehalten werden, die Fahrt, der Längs- und Rolllagewinkel sollen geregelt und Störungen unterdrückt werden. Als Auslegungsverfahren werden Theorien der Zustandsregelungen im Zeitbereich (Eigenstrukturvorgabe) und Frequenzbereich (H-infinity loop-shaping) verwendet. Hierdurch wird durch die inneren Regelschleifen ein Verhalten des Mehrkörperflugzeugs erzielt, das dem eines starren Flugzeugs entspricht. Für die äußeren Regelschleifen werden anschließend klassische Konzepte von Autopiloten verwendet. Im Ergebnis ist eine Regelung des Flugweges über Grund des Mehrkörperflugzeugs und somit ein tatsächlicher Betrieb als HAPS möglich. Die Funktionalität des Reglers wird abschließend in nichtlinearen Simulationen mit vollständiger Flugdynamik verifiziert.
Advanced Flight Dynamics With Elements Of Flight Control
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Author : Nandan K. Sinha
language : en
Publisher: CRC Press
Release Date : 2017-06-27
Advanced Flight Dynamics With Elements Of Flight Control written by Nandan K. Sinha and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-06-27 with Science categories.
Advanced Flight Dynamics aim to integrate the subjects of aircraft performance, trim and stability/control in a seamless manner. Advanced Flight Dynamics highlights three key and unique viewpoints. Firstly, it follows the revised and corrected aerodynamic modeling presented previously in recent textbook on Elementary Flight Dynamics. Secondly, it uses bifurcation and continuation theory, especially the Extended Bifurcation Analysis (EBA) procedure devised by the authors, to blend the subjects of aircraft performance, trim and stability, and flight control into a unified whole. Thirdly, rather than select one control design tool or another, it uses the generalized Nonlinear Dynamic Inversion (NDI) methodology to illustrate the fundamental principles of flight control. Advanced Flight Dynamics covers all the standard airplane maneuvers, various types of instabilities normally encountered in flight dynamics and illustrates them with real-life airplane data and examples, thus bridging the gap between the teaching of flight dynamics/ control theory in the university and its practice in airplane design bureaus. The expected reader group for this book would ideally be senior undergraduate and graduate students, practicing aerospace/flight simulation engineers/scientists from industry as well as researchers in various organizations. Key Features: Focus on unified nonlinear approach, with nonlinear analysis tools. Provides an up-to-date, corrected, and unified presentation of aircraft trim, stability and control analysis including nonlinear phenomena and closed-loop stability analysis. Contains a computational tool and real-life example carried through the chapters. Includes complementary nonlinear dynamic inversion control approach, with relevant aircraft examples. Fills the gap in the market for a text including non-linear flight dynamics and continuation methods.
Flight Dynamics Principles
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Author : M. V. Cook
language : en
Publisher: Butterworth-Heinemann
Release Date : 2012-11-29
Flight Dynamics Principles written by M. V. Cook and has been published by Butterworth-Heinemann this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-11-29 with Science categories.
Previous ed.: 2007. - Includes index.
Airplane Flight Dynamics And Automatic Flight Controls
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Author : Jan Roskam
language : en
Publisher: Darcorporation
Release Date : 1998
Airplane Flight Dynamics And Automatic Flight Controls written by Jan Roskam and has been published by Darcorporation this book supported file pdf, txt, epub, kindle and other format this book has been release on 1998 with Aerodynamics categories.
Flight Dynamics Principles
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Author : Michael V. Cook
language : en
Publisher: Butterworth-Heinemann
Release Date : 2013-10-09
Flight Dynamics Principles written by Michael V. Cook and has been published by Butterworth-Heinemann this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-10-09 with Science categories.
Flight dynamicists today need not only a thorough understanding of the classical stability and control theory of aircraft, but also a working appreciation of flight control systems and consequently a grounding in the theory of automatic control. In this text the author fulfils these requirements by developing the theory of stability and control of aircraft in a systems context. The key considerations are introduced using dimensional or normalised dimensional forms of the aircraft equations of motion only and through necessity the scope of the text will be limited to linearised small perturbation aircraft models. The material is intended for those coming to the subject for the first time and will provide a secure foundation from which to move into non-linear flight dynamics, simulation and advanced flight control. Placing emphasis on dynamics and their importance to flying and handling qualities it is accessible to both the aeronautical engineer and the control engineer. Emphasis on the design of flight control systems Intended for undergraduate and postgraduate students studying aeronautical subjects and avionics, systems engineering, control engineering Provides basic skills to analyse and evaluate aircraft flying qualities
Introduction To Aircraft Flight Mechanics
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Author : Thomas R. Yechout
language : en
Publisher: AIAA
Release Date : 2003
Introduction To Aircraft Flight Mechanics written by Thomas R. Yechout and has been published by AIAA this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with Aerodynamics categories.
Based on a 15-year successful approach to teaching aircraft flight mechanics at the US Air Force Academy, this text explains the concepts and derivations of equations for aircraft flight mechanics. It covers aircraft performance, static stability, aircraft dynamics stability and feedback control.
Advanced Techniques For Clearance Of Flight Control Laws
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Author : Chris Fielding
language : en
Publisher: Springer
Release Date : 2003-07-01
Advanced Techniques For Clearance Of Flight Control Laws written by Chris Fielding and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003-07-01 with Technology & Engineering categories.
In this book recent results of the GARTEUR (Group for Aeronautical Research and Technology in Europe) Action Group FM (AG11) are presented. The book focuses on analysis techniques for the flight clearance of highly augmented aircrafts, including contributions of 20 European aeronautical organisations such as National Research Centers, Aerospace Industries and Universities. The tasks and requirements of the Industrial Clearance Process for Flight Control Laws are presented as well as classical and particularly new analysis methods. The different methods are evaluated and compared and their potential application to Civil Aircraft is demonstrated.
Automatic Flight Control Systems
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Author : Donald McLean
language : en
Publisher:
Release Date : 1990
Automatic Flight Control Systems written by Donald McLean and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with Automatic pilot (Airplanes) categories.
A treatment of automatic flight control systems (AFCS) for fixed wing and rotary wing aircraft. The text covers in detail the subject of stability and control theory. All the principal AFC modes are covered and the effects of atmospheric turbulance and structural flexibility are charted.
Introduction To Fly By Wire Flight Control Systems
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Author : David Kern
language : en
Publisher: Kern Aerospace, LLC
Release Date : 2021-12-18
Introduction To Fly By Wire Flight Control Systems written by David Kern and has been published by Kern Aerospace, LLC this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-12-18 with Transportation categories.
The #1 guide to understanding the "why and how" of fly-by-wire flight control systems. This book is an approachable and easily understandable must-read for aviation professionals! Why don't new aircraft designs allow the pilots a mechanical control connection? This book explains how fly-by-wire fixes the top 5 problems with mechanical controls for high performance aircraft. Rather than describe a particular aircraft’s design with confusing acronyms, readers will get a "behind the scenes" understanding for the critical concepts that apply to any modern aircraft. Because these design principles are easily described and understood, readers of this book will be armed with knowledge as they approach their flight manual procedures. Including: - Problems with mechanical flight controls - Advantages of fly-by-wire - How and why can fly-by-wire control systems fail? - Why are four computers better than one or two? - Explanations of the control laws used by business jets, fighters, and airliners - What sensors are needed, and how the system maintains control when sensors are lost - Design considerations for risk mitigation in case of component failures Buy this book to read on your next layover!
Introduction To Aircraft Flight Mechanics
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Author : Thomas R. Yechout
language : en
Publisher:
Release Date : 2003
Introduction To Aircraft Flight Mechanics written by Thomas R. Yechout and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with Aerodynamics categories.