• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.1-6
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• 2008

The tilt rotor aircraft has the flight characteristics which takes off vertically like a helicopter and flies forward like an airplane. Especially, the transition process from a helicopter to an airplane mode requires not only the mixing of control inputs but also the stability and controllability augmentation system(SCAS) in order to keep the safe flight because there are compound flight dynamic characteristics of a helicopter and an airplane including non-linearity, uncertainty. This paper describes the design of SCAS in a lateral motion for the tilt rotor aircraft based on the $H_{\infty}$ control method, which was performed from mathematical model with weighting matrix based on the relationship between the $H_{\infty}$ norm and the sensitivity function. Through simulation analysis for the controller designed on the $H_{\infty}$ control theory, it was shown that this method may be applied to the control design of the tilt rotor aircraft.

• Journal of Information Processing Systems
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• v.19 no.2
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• pp.232-239
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• 2023

Aiming at the poor compression quality of traditional image compression coding (ICC) algorithm, a multi-description ICC algorithm based on depth learning is put forward in this study. In this study, first an image compression algorithm was designed based on multi-description coding theory. Image compression samples were collected, and the measurement matrix was calculated. Then, it processed the multi-description ICC sample set by using the convolutional self-coding neural system in depth learning. Compressing the wavelet coefficients after coding and synthesizing the multi-description image band sparse matrix obtained the multi-description ICC sequence. Averaging the multi-description image coding data in accordance with the effective single point's position could finally realize the compression coding of multi-description images. According to experimental results, the designed algorithm consumes less time for image compression, and exhibits better image compression quality and better image reconstruction effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.6
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• pp.75-82
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• 2006

Tiltrotor aircraft can fly about twice faster and several times further than conventional helicopters. These aircraft provide advantages preventing compressibility of advancing side and stall of retreating side of blades because they take forward flight with tilting rotor systems. However, they have limit on forward flight speed because of the aeroelastic instability known as whirl flutter. First, the parametric study on the aeroelastic stability of the isolated rotor system has been performed in this paper. And the effects of pitch-link stiffness, gimbal spring constant, and precone angle on the whirl flutter stability of Smart-UAV have been investigated through CAMRAD II analysis.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.2
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• pp.18-33
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• 2008

This paper presents design optimization of a new Active Twist Rotor (ATR) blade and conducts its aeroelastic analysis in forward flight condition. In order to improve a twist actuation performance, the present ATR blade utilizes a single crystal piezoelectric fiber composite actuator and the blade cross-sectional layout is designed through an optimization procedure. The single crystal piezoelectric fiber composite actuator has excellent piezoelectric strain performance when compared with the previous piezoelectric fiber composites such as Active Fiber Composites (AFC) and Macro Fiber Composites (MFC). Further design optimization gives a cross-sectional layout that maximizes the static twist actuation while satisfying various blade design requirements. After the design optimization is completed successfully, an aeroelastic analysis of the present ATR blade in forward flight is conducted to confirm the efficiency in reducing the vibratory loads at both fixed- and rotating-systems. Numerical simulation shows that the present ATR blade utilizing single crystal piezoelectric fiber composites may reduce the vibratory loads significantly even with much lower input-voltage when compared with that used in the previous ATR blade. However, for an application of the present single crystal piezoelectric actuator to a full scaled rotor blade, several issues exist. Difficulty of manufacturing in a large size and severe brittleness in its material characteristics will need to be examined.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.556-561
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• 2009

The UAV(Unmanned Aerial Vehicle) that is remotely operating in various and long flight environments must have a very reliable propulsion system. Precise fault diagnosis of the turbo shaft engine for the Smart UAV that has the vertical take-off, landing and forward flight behaviors can promote reliability and availability. This work proposes a new diagnostic method that can identify the faulted components from engine measuring parameter changes using Fuzzy Logic and quantify its faults from the identified fault pattern using Neural Network Algorithms. The proposed diagnostic method can detect not only single fault but also multiple faults.

• Advances in aircraft and spacecraft science
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• v.6 no.1
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• pp.31-49
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• 2019

Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, helicopter blades, engine rotors, buildings and bridges. Flutter occurs as a result of interactions between aerodynamic, stiffness and inertia forces on a structure. The conventional method for designing a rotor blade to be free from flutter instability throughout the helicopter's flight regime is to design the blade so that the aerodynamic center (AC), elastic axis (EA) and center of gravity (CG) are coincident and located at the quarter-chord. While this assures freedom from flutter, it adds constraints on rotor blade design which are not usually followed in fixed wing design. Periodic Structures have been in the focus of research for their useful characteristics and ability to attenuate vibration in frequency bands called "stop-bands". A periodic structure consists of cells which differ in material or geometry. As vibration waves travel along the structure and face the cell boundaries, some waves pass and some are reflected back, which may cause destructive interference with the succeeding waves. In this work, we analyze the flutter characteristics of a helicopter blades with a periodic change in their sandwich material using a finite element structural model. Results shows great improvements in the flutter forward speed of the rotating blade obtained by using periodic design and increasing the number of periodic cells.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.2
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• pp.190-199
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• 2011

Unsteady flow simulations of complete helicopter configurations were conducted, and the flow fields and the aerodynamic interferences between the main rotor, fuselage, and tail rotor were investigated. For these simulations, a three-dimensional flow solver based on unstructured meshes was used, coupled with an overset mesh technique to handle relative motion among those components. To validate the flow solver, calculations were made for a UH-60A complete helicopter configuration at high-speed and low-speed forward flight conditions, and the unsteady airloads on the main rotor blade were compared to available flight test data and other calculated results. The results showed that the fuselage changed the rotor inflow distribution in the main rotor blade airloads. Such unsteady vibratory airloads were produced on the fuselage, which were nearly in-phase with the blade passage over the fuselage. The flow solver was then applied to the simulation of a generic complete helicopter configuration at various flight conditions, and the results were compared with those of the CAMRAD-II comprehensive analysis code. It was found that the main rotor blades strongly interact with a pair of disk-vortices at the outer edge of the rotor disk plane, which leads to high pulse airloads on the blade, and these airloads behave differently depending on the specific flight condition.

• The Journal of Korea Robotics Society
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• v.6 no.2
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• pp.97-107
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• 2011

This paper describes efficient flight control algorithms for building a reconfigurable ad-hoc wireless sensor networks between nodes on the ground and airborne nodes mounted on autonomous vehicles to increase the operational range of an aerial robot or the communication connectivity. Two autonomous flight control algorithms based on adaptive gradient climbing approach are developed to steer the aerial vehicles to reach optimal locations for the maximum communication throughputs in the airborne sensor networks. The first autonomous vehicle control algorithm is presented for seeking the source of a scalar signal by directly using the extremum-seeking based forward surge control approach with no position information of the aerial vehicle. The second flight control algorithm is developed with the angular rate command by integrating an adaptive gradient climbing technique which uses an on-line gradient estimator to identify the derivative of a performance cost function. They incorporate the network performance into the feedback path to mitigate interference and noise. A communication propagation model is used to predict the link quality of the communication connectivity between distributed nodes. Simulation study is conducted to evaluate the effectiveness of the proposed reconfigurable airborne wireless networking control algorithms.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.11 no.1
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• pp.5-16
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• 2003

The present study was carried out to develop highly efficient RC ornithopter 'Songgolmae' powered by motor and battery. Designed electric ornithopter, which has the dimension of O.88m(W)${\times}$0.56m(L)${\times}$0.15m(H), is smaller than a conventional ornithopter. This ornithopter weighs 277 grams and has 3 channels radio control. It runs on an electric motor by a lithium polymer battery and has a gear ratio of about 75${\sim}$95 to 1 to flap its 88 cm wingspan. The aerodynamic performance of the ornithopter, applied to a flapping motion only, was validated by flight tests. Flight times have exceeded 23 minutes until the battery was used up. The flight test results indicate that the ornithopter developed here has sufficient thrust to propel itself in a forward flight. From the economical point of view and the handling of the RC ornithopter, it can be said that the developed robot ornithopter is an effective RC ornithopter. This robot ornithopter flies its way high into the sky just like a real bird flies. The robot ornithopter is used for a wide range of missions.

• Journal of Contemporary Eastern Asia
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• v.4 no.1
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• pp.1-7
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• 2005

In this paper uses Kaname Akamatsu's 'Flying Geese' model to analyse Japan's role in East Asian integration. Japan made the first attempt to lead Asian countries before the Second World War. At that time, the Japanese Government embarked on a brutally expansionist policy the result of which was creation of the first gaggle of 'flying geese' under the name of the 'Greater East Asia Co-Prosperity Sphere.' During the 'flight' Japan was forcefully imposing its own ideals and values on the rest of the 'gaggle.' At the same time, the Japanese Government assumed hostile attitude toward Western countries. Japan's defeat in the Second World War signified the end of flight for the first 'flying geese' gaggle. After the war, Japan made another attempt at regional integration. This time it was done through establishing a production network in East Asia. Thus the second gaggle of 'flying geese' came into existence. During the flight of the 'second gaggle' of geese, Japan was fostering good ties with Western countries as well, especially the United States. However, some leaders of the 'second gaggle's' member-countries emboldened by their countries' economic success proclaimed that future belongs to Asia and put forward the 'Asian values' argument. The Asian economic crisis of 1997 interrupted the flight of the 'second gaggle' and effectively put an end to the 'Asian values' debate. It is interesting to note that some elements of the 'Asian values' argument resembled ultranationalist discourse that had been dominant in Japan before and during the Second World War. This paper compares historical patterns of East Asian regional integration and highlights future challenges for Japan's Asia policy.