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Robust Controller Design For A Fixed Wing UavPrach, Anna 01 September 2009 (has links) (PDF)
This study describes the design and implementation of the pitch and roll autopilots for a fixed wing unmanned vehicle. A Tactical Unmanned Aerial Vehicle (TUAV), which is designed at the Middle East Technical University (METU), is used as a
platform. This work combines development of the classical and robust controllers, which are used for the pitch and roll autopilots. One of the important steps in the thesis is development of the non-linear dynamic model of the UAV, which is developed in MATLAB/Simulink environment. Two different strategies of the controller design imply development of the PID and controllers. Simulation results illustrate the performances of the designed controllers. Simulation is
performed for the nominal model of the UAV and for the model that includes uncertainties and sensor noises.
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Design And Analysis Of An Equipment Rack Structure Of A Medium Transport AircraftYalcin, Mehmet Efruz 01 September 2009 (has links) (PDF)
In this study, equipment rack structure for a medium transport aircraft was designed and finite element analysis of this design was performed. The equipment rack structure, which was designed for a modernization project, was positioned and dimensions were determined by regarding the geometry of primary structures of the aircraft. The structure was designed such that it satisfies the pre-defined margin of safety values. Design of the structure was prepared in Unigraphics, and the finite element modeling and analysis phases were carried out using MSC.Patran and MSC.Nastran programs. For the fastener analysis, which is usually carried out by hand calculations, two analysis tools were prepared by using FORTRAN and Microsoft Office Excel programs. These tools were found to greatly facilitate the analysis and save time. As these tools can be used in other finite element analyses, in which MSC.Patran and MSC.Nastran programs are used, user manuals were prepared.
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A Numerical Investigation Of Helicopter Flow Fields Including Thermal Effects Of Exhaust Hot GasesGursoy, Zeynep Ece 01 October 2009 (has links) (PDF)
This thesis investigates the flow field of a twin-engine, medium lift utility helicopter numerically. The effects of the exhaust hot gases emerging from the engines are accounted for in the numerical study. The commercial computational fluid dynamics (CFD) software ANSYS Fluent is employed for the computations. While the effects of engines are included in the computations through simple inlet and outlet boundary conditions, the main and tail rotors are simulated by the Virtual Blade Model in a time-averaged fashion. Forward flight at four different advance ratios and hover in ground effect are studied. The temperature distribution around the tail boom is compared to available flight test data. Good agreement with the flight test data is observed.
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Flight Control Of A Tilt Duct Uav With Emphasis On The Over Actuated Transition Flight PhaseUnlu, Tugba 01 October 2009 (has links) (PDF)
In the thesis, automatic flight control system is designed for Tilt Duct Unmanned Aerial Vehicle (UAV). The vehicle is a Vertical Take-Off Landing (VTOL) type with two symmetric
rotors on the wings, one aft rotor on the aft body. It behaves like a helicopter but with higher speeds in forward flight. Transition flight of the aircraft from hover to cruise or take-off to forward flight is the primary concern of the thesis study with the nonlinearities and instabilities encountered, together with the over-actuated controls in this mode. A nonlinear simulation code is developed including nonlinear equations of motion together with the nonlinear aerodynamics,
environmental eects, and rotor dynamics. Trim and linearization codes are also developed. Trim conditions for the transition flight phase are calculated for two different
transition scenarios. Linear controllers are developed and nonlinear controller is designed for the transition mode. Nonlinear controller uses the state dependent Ricatti equation SDRE approach by using extended linearization. Two loop approach is used in order to increase controllability. In the inner loop, attitude rates are fed back and SDRE approach is used to calculate the feedback gain matrix online. In the outer loop, vehicle attitude is controlled using the eigenvalue assignment. Blended inverse algorithm based control allocation method is used in control of the over-actuated transition phase. This algorithm is shown to be quite effective among different methods in not only generating necessary forces needed for the control, but also allocating with more control authority on the desired actuator.
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Experimental And Numerical Investigation Of Flow Field Around Flapping Airfoils Making Figure-of-eight In HoverBaskan, Ozge 01 September 2009 (has links) (PDF)
ABSTRACT
EXPERIMENTAL AND NUMERICAL INVESTIGATION OF FLOW FIELD AROUND FLAPPI
G AIRFOILS MAKING FIGURE-OF-EIGHT IN HOVER
BASKAN, Ö / zge
M.Sc., Department of Aerospace Engineering
Supervisor: Prof. Dr. H. Nafiz Alemdaroglu
September 2009, 94 pages
The aim of this study is to investigate the flow field around a flapping airfoil making figure-of-eight motion in hover and to compare these results with those of linear flapping
motion. Aerodynamic characteristics of these two-dimensional flapping motions are
analyzed in incompressible, laminar flow at very low Reynolds numbers regime using both
the numerical (Computational Fluid Dynamics, CFD) and the experimental (Particle Image
Velocimetry, PIV) tools. Numerical analyses are performed to investigate the effect of
different parameters such as the amplitude of motion in y-direction, angle of attack,
Reynolds number and camber on the aerodynamic force coefficients and vortex formation
mechanisms. Both symmetric and cambered airfoil sections are investigated at three
different starting angles of attack for five different amplitudes of motion in y-direction
including linear flapping motion. Experimental simulations are performed in order to verify
the numerical results only for linear motion at Reynolds number of 1000 for symmetric and
cambered airfoils at three different angles of attack. Computed vortical structures are then
compared to vorticity contours obtained from the experiments and advantages of figure-of&ndash / eight motion over linear motion are discussed.
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Investigation Of Rotor Wake Interactions In Helicopters Using 3d Unsteady Free Vortex Wake MethodologyYemenici, Oznur 01 December 2009 (has links) (PDF)
This thesis focuses on developing and examining the capabilities of a new in-house
aerodynamic analysis tool, AeroSIM+, and investigating rotor-rotor aerodynamic
interactions for two helicopters, one behind the other in forward flight. AeroSIM+ is a 3-D
unsteady vortex panel method potential flow solver based on a free vortex wake
methodology. Validation of the results with the experimental data is performed using the
Caradonna-Tung hovering rotor test case. AeroSIM+ code is improved for forward flight
conditions so that, the blades are allowed to move according to the rotor dynamics. In the
simulations, blade airload prediction is seen to be sensitive to changes in vortex core size.
Blade Vortex Interaction (BVI) locations differ depending on the relative position of the rear
rotor with respect to the front rotor as well as on the forward flight speed. It was observed
that the performance characteristics of the rear rotor alter depending on the relative positions
of the rotors within the asymmetric wake flow field. The results of this thesis study such as
the computed forces and moments on each rotor and the frequency characteristics of these
loads can be also used in helicopter dynamics simulators.
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Modelling And Simulation Of A Wheeled Land VehicleLafci, Alp 01 December 2009 (has links) (PDF)
Land transportation is the main form of transportation around the world. Since the invention of the car land transportation changed drastically. As the cars took a solid part in human lives with the developments in electronics and robotics unmanned land vehicles are the future of both commercial and military land transportation. Today armies want unmanned land vehicles to provide logistical support to the units near threat zones and commercial firms want them to deliver goods more reliably and with less expense.
In this thesis, mainly, a 6DoF dynamical model for a four wheeled land vehicle is developed and an autopilot design is presented using PID techniques. For dynamical modeling of the vehicle internal combustion engines, transmissions, tires, suspensions, aero dynamical drag forces and brakes are studied and the model is tested over some scenarios for evaluating its performance.
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Structural Design And Evaluation Of An Adaptive Camber WingSakarya, Evren 01 February 2010 (has links) (PDF)
This study presents a camber morphing concept as an alternative to existing plain flap or aileron type hinged control surfaces used in wings. Structural aspects of the concept are investigated with static nonlinear finite element analyses by using MSC Nastran. In order to assess the aerodynamic characteristics / CFD based 2D solutions are obtained using ANSYS Fluent. The camber morphing concept is applied to the full scale hingeless control surface and implemented in the adaptive camber wing. Hingeless control surfaces and adaptive camber wing are manufactured and changes made in manufacture stages are incorporated into finite element models. Finite element analyses of the wing are conducted with static and dynamic loading and comparison with experimental dynamic analyses are performed.
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Trajectory Computation Of Small Solid Particles Released And Carried By Flowfields Of Helicopters In Forward FlightPekel, Yusuf Okan 01 January 1995 (has links) (PDF)
In this thesis, trajectory computations of chaff particles ejected from a medium weight utility helicopter are performed using computational fluid dynamics. Since these chaff particles are ejected from a helicopter and carried by its flow field, it is necessary to compute and include the effects of the helicopter flow field in general and engine hot gases, main and tail rotor wakes in particular. The commercial code FLUENT is used for flow field and trajectory computations. Both main rotor and tail rotor are simulated by the so-called Virtual Blade Model in a transient fashion. Flows through the engine inlets and exhausts are treated via appropriate boundary conditions in the analysis. The generic ROBIN geometry is studied first in order to assess the accuracy of the Virtual Blade Model and various turbulence models. The computational solutions related to the ROBIN geometry are validated against the available experimental data. Flowfield and trajectory computations of chaff particles are done at a forward flight condition at which certain flight data and chaff trajectory data were acquired by ASELSAN, Inc. In the flight test, three successive chaff decoy ejections were conducted, and the chaff cloud distributions were recorded by two high-speed cameras positioned on two different locations on the helicopter. Numerical calculations employ the post-processed camera recordings for setting the initial distributions of the chaff particles. Then, the computational results related to the chaff particle trajectories are validated by comparing to the recorded transient chaff cloud distributions from the ASELSAN flight test. For post-processing of the recorded chaff distributions, an experimental analysis commercial code called TrackEye is used. It is found that the numerical simulations capture the trends of chaff particle distributions reasonably well.
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Design And Analysis Of A Structural Component Of A Heavy Transport AircraftCikrikci, Davut 01 February 2010 (has links) (PDF)
This thesis aims to present the design and analysis of a structural component of a heavy transport aircraft. The designed component is the &ldquo / coupling&ldquo / which is the interface member connecting two frames or two stringers in the fuselage assembly. The &ldquo / frames&rdquo / , which are the circumferential stiffeners, are joined together by the &ldquo / frame couplings&rdquo / . The &ldquo / stringers&rdquo / , which are the longitudinal stiffeners, are joined together by the &ldquo / stringer couplings&rdquo / .
At the preliminary design phase / the structural design principles of the frame and the stringer coupling parts are explained / which are based on the company experiences that were gained from previous aircraft projects. Afterwards, conceptual design phase is performed by structural analysis of the components. The structural analysis methods are defined and illustrated by analyzing typical examples of the frame and the stringer coupling parts.
Moreover, the critical load case selection process for the structural components is explained and brief information about the load cases that the structural components will be subjected to in their service life are also given in order to have a feeling about flight regime of the aircraft. The applied loads used in structural analysis of the frame coupling and the stringer coupling components are obtained from the global finite element model of the aircraft. The verification process of the part of global finite element model where the developed components are located is also explained in the thesis.
Finally, the general conclusions of the thesis are specified and the recommendations for future work are proposed for similar design and analysis efforts.
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