• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.654-667
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• 2003

This paper presents a consequence of the systematic approach to identify the aerodynamic parameters of an unmanned aerial vehicle (UAV) equipped with the automatic flight control system. A 3-2-1-1 excitation is applied for the longitudinal mode while a multi-step input is applied for lateral/directional excitation. Optimal time step for excitation is sought to provide the broad input bandwidth. A fully automated programmed flight test method provides high-quality flight data for system identification using the flight control computer with longitudinal and lateral/directional autopilots, which enable the separation of each motion during the flight test. The accuracy of the longitudinal system identification is improved by an additional use of the closed-loop flight test data. A constrained optimization scheme is applied to estimate the aerodynamic coefficients that best describe the time response of the vehicle. An appropriate weighting function is introduced to balance the flight modes. As a result, concurrent system models are obtained for a wide envelope of both longitudinal and lateral/directional flight maneuvers while maintaining the physical meanings of each parameter.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.2
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• pp.139-144
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• 2004

The flight control system designed for an unmanned airship, which is under development by KARI, is in reduced. First, the dynamic characteristics of the airship are addressed, which are fairly different from those of the nominal aircraft. In order to implement autonomous flight for the unmanned airship, flight control logic is designed including autopilot and guidance law. The autopilot is designed under consideration of the velocity region of the unmanned airship. The guidance laws are implemented in main operational modes such as point navigation, station keeping and spiral up/down for emergency return. Their simulation results are also presented in order to validate performances of the flight control system.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.13 no.2
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• pp.14-26
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• 2005

A tilt-rotor aircraft has various flight modes : helicopter, airplane, and conversion. Each of flight mode has unique and nonlinear flight characteristics. Therefore the gain schedules for whole flight envelope are required for effective flight performance. This paper proposes collective, flap, and nacelle angle scheduler for whole flight envelope of the Smart UAV(Unmanned Air Vehicle) based on CAMRAD(Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics) II analysis results. The scheduler designs are improved so that the pitch attitude angle of helicopter mode was minimized. The range of scheduler are reduced inside of engine performance limits. The conversion corridor and rotor governor are suggested also.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.2
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• pp.1-6
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• 2012

Four dimensional(4-D) trajectory modeling is conducted based on flight plan. The flight plan is divided into several segments which represent certain operating flight modes. Thrust, drag and fuel consumption rate of an aircraft are calculated using BADA provided by Eurocontrol. The trajectory is modeled with the rate of climb/descent calculated with Total-Energy Equation. The simulation results with a typical aircraft and its flight plan indicate that the trajectory modeled corresponds well with the suggested flight plan. The performance profiles including total endurance time and time history for speed, thrust, drag and fuel consumption were also appropriately generated.

• 시스템엔지니어링워크숍
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• s.4
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• pp.101-104
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• 2004

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.9
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• pp.759-765
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• 2016

This paper presents the principle, dynamics modeling and control, hardware implementation, and flight test result of a hybrid-type unmanned aerial vehicle (UAV). The proposed UAV was designed to provide both hovering and fixed-wing type aerodynamic flight modes. The UAV's flight mode transition was achieved through the attitude transformation in pitch axis, which avoids a complex rotor tilt mechanism from a structural and control viewpoint. To achieve this, a different navigation coordinate was introduced that avoids the gimbal lock in pitch singularity point. Attitude and guidance control algorithms were developed for the flight control system. For flight test purposes, a quadrotor attached with a tailless fixed-wing structure was manufactured. An onboard flight control computer was designed to realize the navigation and control algorithms and the UAV's performance was verified through the outdoor flight tests.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.21-31
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• 2007

Relaxed Static Stability (RSS) concept has been applied to improve aerodynamic performance of modern version supersonic jet fighter aircraft. The T-50 advanced supersonic trainer employs the RSS concept in order to improve the aerodynamic performance. And the flight control system stabilizes the unstable aircraft and provides adequate handling qualities. The T-50 longitudinal control laws employ a proportional-plus-integral type controller based on a dynamic inversion method. The longitudinal dynamic modes consist of short period with high frequency and phugoid mode with low frequency. The design goal of longitudinal control law is optimization of short period damping ratio and frequency using Lower Order Equivalent System (LOES) complying the requirement of MIL-F-8785C. This paper addresses phugoid mode characteristics such as damping ratio and natural frequency that is affected by the nonlinear control laws such as angle of attack limiter, auto pitch attitude command system and autopilot of pitch attitude hold.

• Journal of Korea Foundry Society
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• v.12 no.4
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• pp.326-334
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• 1992

Particle-reinforced metal matrix composites via the Osprey spray casting process were fabricated by injecting second phase particles of $Al_2O_3$(＜$40{\mu}m$) and W($6{\mu}m$) into the spray of Cu droplets, and the thermal behaviors of the composite droplets during flight were considered theoretically on the basis of mixing modes between the Cu droplets and the reinforced particulates injected. It was found that the W-injected spray is comprised of particle-embedded droplets, and the $Al_2O_3-injected$ spray comprises particle-attached droplets. From the predicted results of the thermal behaviors of the composite droplets and preforms produced, it is concluded that the thermal behaviors of the composite droplets during flight, and during the subsequent deposition are strongly influenced by its mixing modes between the reinforced particulates and Cu droplets during flight.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.198-203
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• 2010

In this paper, study on the mode characteristics analysis of the SH-EMAT (shear horizontal, electromagnetic acoustic transducer) waves for evaluating the thickness reduction in plates such as corrosion and friction is presented. Noncontact methods for ultrasonic wave generation and detection have been a great concern and highly demanded due to their capability of wave generation and reception on surface of high temperature or on rough surface. Mode identification of the SH-EMAT wave is carried out in an aluminum plate with thinning defects using time frequency analysis method such as wavelet transform, compared with theoretically calculated group velocity dispersion curve. The changes of various wave features such as the amplitude and the time-of-flight have been observed and the correlations with the thickness reduction have been investigated. Firstly, experiments have been conducted to confirm that it is possible to selectively generate and receive specific desired SH modes. These modes have then been analyzed to select the parameters that are sensitive to the thickness change. The results show that the mode cutoff and the time-of-flight changes are feasible as key parameters to evaluate the thickness reduction.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.111-119
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• 2013

Conceptual design of RBCC (Rocket Based Combined Cycle) engine is performed through the thermodynamic cycle analysis. The engine is designed to take off at sea level and accelerate to Mach 8 at 30 km altitude. According to the flight speed, the engine operating modes are categorized into 3 modes : Ejectorjet (~ Mach 3), Ramjet (Mach 3~6), Scramjet (Mach 6~8). As a design result, the engine has a diameter of 1 m and a length of 6.7 m. In the prediction results, its maximum thrust is 16.5 ton. In Ramjet and Scramjet modes, design condition of the engine intake influence the engine thrust according to the flight speed.