Spelling suggestions: "subject:"airplanes -- 7control"" "subject:"airplanes -- bcontrol""
31 |
Integrated multi-disciplinary design of a sailplane wingStrauch, Gregory J. 14 November 2012 (has links)
The objective of this research is to investigate the techniques and payoffs of integrated aircraft design. Lifting line theory and beam theory are used for the analysis of the aerodynamics and the structures of a composite sailplane wing. The wing is described by 33 - 34 design variables which involve the planform geometry, the twist distribution, and thicknesses of the spar caps, spar webs, and the skin at various stations along the wing. The wing design must satisfy 30 â 31 aeroelastic, structural, aerodynamic, and performance constraints.
Two design procedures are investigated. The first, referred to as the iterative, sequential procedure, involves optimizing the aerodynamic design for maximum average cross-country speed at E1 constant structural weight, and then optimizing the the structural design of the resulting wing geometry for minimum weight. This value is then used in another aerodynamic optimization, and the process continues iteratively until the weight converges. The other procedure, the integrated one, simultaneously optimizes the aerodynamic and the structural design variables for either maximum average cross-country speed or minimum weight.
The integrated procedure was able to improve the value of the objective function obtained by the iterative procedure in all cases. This shows The objective of this research is to investigate the techniques and payoffs of integrated aircraft design. Lifting line theory and beam theory are used for the analysis of the aerodynamics and the structures of a composite sailplane wing. The wing is described by 33 - 34 design variables which involve the planform geometry, the twist distribution, and thicknesses of the spar caps, spar webs, and the skin at various stations along the wing. The wing design must satisfy 30 â 31 aeroelastic, structural, aerodynamic, and performance constraints. Two design procedures are investigated. The first, referred to as the iterative, sequential procedure, involves optimizing the aerodynamic design for maximum average cross-country speed at E1 constant structural weight, and then optimizing the the structural design of the resulting wing geometry for minimum weight. This value is then used in another aerodynamic optimization, and the process continues iteratively until the weight converges. The other procedure, the integrated one, simultaneously optimizes the aerodynamic and the structural design variables for either maximum average cross-country speed or minimum weight.
The integrated procedure was able to improve the value of the objective function obtained by the iterative procedure in all cases. This shows that definite benefits can be gained from taking advantage of aerodynamic/structural interactions during the design process. / Master of Science
|
32 |
Effects of stimulus class on short-term memory workload in complex information display formatsTan, Kay Chuan 28 July 2008 (has links)
The objective of this research effort was to identify opportunities and demonstrate methods to reduce aircraft crew member cognitive workload (CWL) by reducing short-term memory (STM) demand. Two experiments qualitatively and quantitatively compared memory loading as a function of stimulus class. Experiment 1 employed a dual-task paradigm where the primary task was compensatory tracking used to load STM and the secondary task was item recognition using the Sternberg paradigm. Experiment 2 employed a singletask paradigm using a modified version of the Sternberg task. Digits, letters, colors, words, and geometrical shapes were tested as memory-set (MSET) items in the Sternberg task. Recognition latency and error rate served as objective measures of STM performance while the Subjective Workload Assessment Technique (SWAT) was employed as a Subjective second measure. Root Mean Square error was used to gauge tracking performance.
Analyses of the experiments' results revealed that recognition latency and SWAT ratings Statistically varied as functions of stimulus class, MSET size, and the interaction between stimulus class and MSET size. Error rate was not statistically different across stimulus class or MSET size. Post-hoc analyses found SWAT to be a more sensitive STM measurement instrument than recognition latency or error rate. No statistically significant degree of secondary task intrusion on the tracking task was found.
In addition to the commonly used classes of digits and letters, this research demonstrated that colors, words, and geometrical shapes could also be utilized as MSET items in short-term memory workload investigations. This research has, more importantly, provided further support for the vital link between STM demand and perceived workload.
The main conclusion of this research is that stimulus class optimization can be a feasible method for reducing STM demand. Differences in processing rate among stimulus classes are large enough to impact visual display design. For many context-specific applications, it should be possible to determine the most efficient stimulus class in which to portray the needed information. The findings of this research are especially applicable in situations of elevated STM demand (e.g., aviation systems operations). In general, however, the results provide helpful information for visual display designers. / Ph. D.
|
33 |
Using Multiplayer Differential Game Theory to Derive Efficient Pursuit-Evasion Strategies for Unmanned Aerial VehiclesReimann, Johan Michael 16 May 2007 (has links)
In recent years, Unmanned Aerial Vehicles (UAVs) have been used extensively in military conflict situations to execute intelligence, surveillance and reconnaissance missions. However, most of the current UAV platforms have limited collaborative capabilities, and consequently they must be controlled individually by operators on the ground. The purpose of the research presented in this thesis is to derive algorithms that can enable multiple UAVs to reason about the movements of multiple ground targets and autonomously coordinate their efforts in real-time to ensure that the targets do not escape. By improving the autonomy of multivehicle systems, the workload placed on the command and control operators is reduced significantly.
To derive effective adversarial control algorithms, the adversarial scenario is modeled as a multiplayer differential game. However, due to the inherent computational complexity of multiplayer differential games, three less computationally demanding differential pursuit-evasion game-based algorithms are presented. The purpose of the algorithms is to quickly derive interception strategies for a team of autonomous vehicles. The algorithms are applicable to scenarios with different base assumptions, that is, the three algorithms are meant to complement one another by addressing different types of adversarial problems.
|
34 |
Robust multi-H2 output-feedback approach to aerial refuelling automation of large aircraft via linear matrix inequalitiesClaase, Etienne H. 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In recent years the aviation industry has shown an interest in the airborne refuelling
of large transport aircraft to enable increased payload mass at take-off and
to extend aircraft range. Due to the large volume of fuel to be transferred, a boom
and receptacle refuelling system with a larger fuel transfer rate is employed. The
refuelling operation is particularly difficult and strenuous for the pilot of the receiver
aircraft, because the position of the receptacle relative to the tanker aircraft must
be maintained within a narrow window for a relatively long period of time. The
airborne refuelling of a large aircraft is typically much more difficult than that of a
fighter aircraft, since the large aircraft is more sluggish, takes much longer to refuel,
and has a relatively large distance between its refuelling receptacle and its centre of
mass. These difficulties provide the motivation for developing flight control laws for
Autonomous In-Flight Refuelling (AIFR) to alleviate the workload on the pilot.
The objective of the research is to design a flight control system that can regulate
the receptacle of a receiver aircraft to remain within the boom envelope of a tanker
aircraft in light and medium turbulence. The flight control system must be robust
to uncertainties in the aircraft dynamic model, and must obey actuator deflection
and slew rate limits.
Literature on AIFR shows a wide range of approaches, including Linear Quadratic
Regulator (LQR), μ-synthesis and neural-network based adaptive control, none of
which explicitly includes constraints on actuator amplitudes, actuator rates and
regulation errors in the design/synthesis. A new approach to designing AIFR flight
control laws is proposed, based on Linear Matrix Inequality (LMI) optimisation.
The relatively new LMI technique enables optimised regulation of stochastic systems
subject to time-varying uncertainties and coloured noise disturbance, while simultaneously
constraining transient behaviour and multiple outputs and actuators to
operate within their amplitude, saturation and slew rate limits. These constraints
are achieved by directly formulating them as inequalities. / AFRIKAANSE OPSOMMING: Die lugvaart industrie toon huidiglik ’n belangstelling in die brandstof oordrag
tussen twee groot vervoervliegtuie gedurende vlug, met die doel om die maksimum
opstyggewig kapasiteit sowel as die maksimum ononderbroke vlugafstand vermoë
van die hervulde vliegtuig te vermeerder. ’n Boom hervulling-stelsel word geïmplementeer
om die hoë spoed van brandstof oordrag te voorsien. Die verrigting van
vluggebonde hervulling van ’n groot, trae vliegtuig is moeiliker en meer veeleisend
as bv. van ’n vegvliegtuig, veral vir die vlieënier van die hervulde vliegtuig, wat
sy boom-skakel moet reguleer binne ’n relatiewe klein boom bewegingsruimte vir ’n
relatiewe lang tydperk. Die kinematika betrokke speel ook ’n groter rol in ’n groot
hervulde vliegtuig a.g.v. die langer afstand tussen die boom-skakel en die massa middelpunt/
draaipunt. Hierdie bied die motivering om ’n beheerstelsel te ontwikkel wat
die taak outomaties uitvoer.
Die doel van die navorsing is om ’n beheerstelsel te ontwerp wat die boom-skakel
van die hervulde vliegtuig outomaties reguleer binne die bewegingsruimte van die
boom, gedurende ligte en matige turbulensie. Daar word van die beheerder vereis
om robuust te wees teen onsekerhede in die vliegtuig se meganika, sowel as om die
beheer oppervlaktes en turbines van die vliegtuig binne hul defleksie-, wringkrag- en
sleurtempo-perke te hou.
Daar bestaan reeds ’n groot verskeidenheid van benaderings tot die outomatisering
van luggebonde hervulling, onder andere LQR, μ-sintese en neurale-netwerk
gebaseerde aanpasbare beheer, waarvan geeneen perke op aktueerders en regulasie
foute direk in die ontwerp insluit nie. ’n Nuwe benadering word voorgestel wat
gebaseer is op Linear Matrix Inequality (LMI) optimering. Die LMI tegniek is relatief
nuut in die gebruik van beheerstelsel ontwerp. Dit stel die ontwerper in staat
om ’n stogastiese stelsel, onderworpe aan tydvariante-stelsel-variasie en gekleurde
ruis versteurings, optimaal te reguleer, terwyl aktueerders en stelsel gedrag direk
beperk word.
|
35 |
Lateral control system design for VTOL landing on a DD963 in high sea statesBodson, Marc January 1982 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by Marc Bodson. / M.S.
|
36 |
Nonlinear control of high performance aircraftBean, Ronnie A. 09 December 1994 (has links)
This thesis presents the design of various controllers for a highly maneuverable,
high performance aircraft, namely the modified F-18. The aircraft
was required to perform high angle-of-attack maneuvers, for which the aircraft
behaves in as a highly nonlinear system. An adaptive PID controller
was used to control the aircraft through these high angle-of-attack maneuvers.
Several nonlinear controllers were then developed based on the adaptive PID
control, and were tested for robustness. This thesis also looks at an improvement
in the aircraft which may improve performance in high angle-of-attack
maneuvers.
The contributions of this thesis are in the areas of control, in general, and
specifically in the area of aircraft control. Successful application of linear
adaptive control and nonlinear control were presented. In the area of aircraft
control, controllers were presented which produce good performance for high
angle-of-attack maneuvers, while maintaining implementability. Also, some
insight is gained into what aircraft changes could improve performance. / Graduation date: 1995
|
37 |
A Methodology To Recover Unstable Aircraft From Post Stall Regimes: Design And AnalysisSaraf, Amitabh 03 1900 (has links)
This thesis deals with high angle of attack behaviour of a generic delta wing model aircraft. A high angle of attack wind tunnel database has been generated for this aircraft and based upon the bifurcation analysis of the data and the results of extensive simulations, it has been shown in the thesis that the post stall behaviour of this aircraft is both unstable and unpredictable. Unpredictability of aircraft behaviour arises from the fact that the aircraft response is oscillatory and divergent; the aircraft state trajectories do not settle down to any stable limit set and very often exceed valid aerodynamic database limits. This unpredictability of behaviour raises a major difficulty in the design of a procedure to recover the aircraft to normal flight regime in case the aircraft stalls and departs accidentally. A new methodology has been presented in this thesis to recover such unstable aircraft. In this methodology, a nonlinear controller is first designed at high angles of attack. This controller is connected by the pilot after the departure of the aircraft and the controller drives the aircraft to a well-defined spin condition. Thus, the controller makes the post stall aircraft behaviour predictable. Then a set of automatic recovery inputs is designed to reduce aircraft rotations and to lower the angle of attack. The present aircraft model is unstable at low angle of attack flight conditions as well and therefore to stabilize the aircraft to a low angle of attack level flight, another controller is designed. The high angle of attack controller is disconnected and the low angle of attack controller is connected automatically during the recovery process. The entire methodology is tested using extensive non-linear six degree-of-freedom simulations and the efficacy of the technique is established.
The nonlinear controller that stabilizes the aircraft to a spin condition is designed using feedback linearization. The stability of a closed loop system obtained using feedback linearization is determined by the stability of the zero dynamics of the open loop plant. It has been shown in literature that the eigenvalues of the linearized zero dynamics are the same as the transmission zeros of the linearized plant at the equilibrium point. It is also well known that the location of transmission zeros of a linear system can be changed by the choice of outputs. In this thesis it is shown that if it is possible to reassign the outputs, then the feedback linearization based design for a linear system becomes very similar to a controller design for eigenvalue assignment. This thesis presents a new two-step procedure to obtain a locally stable and optimally robust closed loop system using feedback linearization. In the first step of this procedure optimal locations of the transmission zeros are found and in the second step, optimal outputs are constructed to place the system transmission zeros at these locations. The same outputs can then be used to construct nonlinear feedback for the nonlinear system and the resultant closed loop system is guaranteed to be locally robustly stable. The high angle of attack controller is designed using this procedure and its performance is presented in the thesis. The stabilized spin equilibrium point of the closed loop system is also shown to have a large domain of attraction.
Having designed a locally robust stabilizing controller, the thesis addresses the problem of the evaluation of robustness of the stability of the equilibrium point in a nonlinear framework. The thesis presents a general method to construct bounds on the additive perturbations of the system vector field over a large region in the domain of attraction of a stable equilibrium point using Lyapunov functions. If the system perturbations lie within these bounds, the system is guaranteed to be stable. The thesis first proposes a method to numerically construct a Lyapunov function over a large region in the domain of attraction. In this method a sequence of Lyapunov functions are constructed such that each function in the sequence gives a larger estimate of the domain of attraction than the previous one. The seminal idea for this method is obtained from the existing literature and this idea is considerably generalized. Using this method, it is possible to numerically obtain a Lyapunov function value at each point in the domain of attraction, but the Lyapunov function does not have an analytical form. Hence, it is proposed to represent this function using neural networks. The thesis then discusses a new method to construct perturbation bounds. It is shown that the perturbation bounds obtained over a large region in the domain of attraction using a single Lyapunov function is too conservative. Using the concept of sequence of Lyapunov functions, the thesis proposes three methods to obtain the least conservative bounds for an initial local Lyapunov function. These general ideas are then applied to the aircraft example and the bounds on the perturbation of the aerodynamic database are presented.
|
Page generated in 0.1017 seconds