• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.343-352
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• 2016

A multi-rotor vehicle is an unmanned vehicle consisting of multiple rotors. A multi-rotor vehicle can be categorized as tri-, quad-, hexa-, and octo-rotor depending on the number of the rotors. Multi-rotor vehicles have many advantages due to their agile flight capabilities such as the ability for vertical take-off, landing and hovering. Thus, they can be widely used for various applications including surveillance and monitoring in urban areas. Since multi-rotors are subject to uncertain environments and disturbances, it is required to implement robust attitude stabilization and flight control techniques to compensate for this uncertainty. In this research, an advanced nonlinear control algorithm, i.e. sliding mode control, was implemented. Flight experiments were carried out using an onboard flight control computer and various real-time autonomous attitude adjustments. The feasibility and robustness for flying in uncertain environments were also verified through real-time tests based on disturbances to the multi-rotor vehicle.

• Journal of Aerospace System Engineering
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• v.13 no.2
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• pp.1-9
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• 2019

This paper elaborates on the directional axis guidance and control algorithm used in mission flight for high altitude long endurance UAV. First, the directional axis control algorithm is designed to modify the control variable such that a strong headwind prevents the UAV from moving forward. Similarly, the guidance algorithm is designed to operate the respective algorithms for Fly-over, Fly-by, and Hold for way-point flight. The design outcomes of each guidance and control algorithm were confirmed through nonlinear simulation of high altitude long endurance UAV. Finally, the penultimate purpose of this study was to perform an actual mission flight based on the design results. Consequently, flight tests were used to establish the flight controllability of the designed guidance and control algorithm.

• Current Industrial and Technological Trends in Aerospace
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• v.4 no.2
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• pp.55-67
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• 2006

20세기에 탄생한 동력비행기는 인간의 이동능력을 비약적으로 향상시켰다. 인류의 미개척지였던 항공분야의 발전은 지속적인 기술개발을 통해 더 빨리, 더 멀리, 더 높이 향하기 위해서 계속 나아가고 있다. 이러한와중에 최근에 괄목할 만한 성장을 이룬 컴퓨터와 소프트웨어 산업의 발전은 비행임무에 따라 위험성이 높거나, 사람이 하기 힘든 반복적이고 지루한 비행을 대신하기위한 로봇 비행체 즉, 무인항공기의 개발을 가능하게 하였다. 무인항공기의 탄생 초기에는 조종사의 희생을 줄이기 위해 군사 분야에서 주로 사용되었으나, 산림감시나 해안정찰, 기상관측, 재난관측, 조난자 수색 등 민수분야의 임무로 점차 활동영역이 넓혀지고 있다. 현재 무인항공기에 탑재된 인공지능의 수준은 안정된 비행이 가능하도록 하는 자동조종(autopilot)과 주어진 비행경로를 추종하기위한 항법유도(Navigation & Guidance)정도이며, 비행 중 발생하는 비상상황에 대처하기 위한 의사판단은 지상의 조종자에 의해 결정된다. 앞으로는 계획되지 않은 상황을 맞이했을 때 무인기 스스로 판단하여 경로를 변경하고, 동시에 여러 무인기들과 협력하여 임무를 수행함으로써 임무효율을 높이는 방향으로 인공지능의 수준이 향상될 것이다. 본 논문에서는 최근의 무인항공기 개발추세와 이들 무인기에 고려되고 있는 제어기에 대해 살펴보고, 향후 무인항공기에 적용될 자율비행 알고리듬과 제어기 시스템의 개발동향에 대해 고찰하였다.

• Journal of KIISE
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• v.44 no.6
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• pp.559-565
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• 2017

A UAV(unmanned aerial vehicle) requires higher reliability for external effects such as electromagnetic interference because a UAV is operated by pre-designed programs that are not under human control. The design of a small UAV with a complete resistance against the external effects, however, is difficult because of its weight and size limitation. In this circumstance, a conventional small UAV dropped to the ground when an external effect caused the rebooting of the flight-control computer(FCC); therefore, this paper presents a novel algorithm for the improvement of the flight safety of a small UAV. The proposed algorithm consists of three steps. The first step comprises the calibration of the navigation equipment and validation of the calibrated data. The second step is the storage of the calibration data from the UAV take-off. The third step is the restoration of the calibration data when the UAV is in flight and FCC has been rebooted. The experiment results show that the flight-control system can be safely operated upon the rebooting of the FCC.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.169-179
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• 2010

Satisfying the same probability of loss of control and essentially two fail operative performance with a triplex computer architecture requires a lot of modification of the conventional redundancy management design techniques, previously employed in quadruplex digital flight control computer. T-50 FCS for triplex redundancy management design applied an advanced digital flight control architecture with an I/O controller which is functionally independent of the digital computer to achieve the same reliability and special failure analysis and isolation schemes for fail operational goals with a triplex configuration. The analysis results indicated that the triplex flight control system is to satisfy the safety requirement utilizing the advanced flight control techniques and the system performance of the implemented flight control system was verified by failure mode effect test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.9
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• pp.711-723
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• 2017

This paper proposes a flight control system for an organic flight array(OFA) which has a new configuration to consist of multi modularized ducted-fan unmanned aerial vehicles (UAVs). The OFA is able to apply to various missions such as indoor reconnaissance, communication relay, and radar jamming by using capability of hover flight. The OFA has a distinguished advantage due to reconfigurable structure to assemble or separate with respect to its missions or operational conditions. A dynamic modelling of the OFA is derived based on equations of motion of the single ducted-fan modules. In order to apply nonlinear control method, an affine system of attitude dynamics is derived. Moreover, the control system is composed of a back-stepping controller for attitude control and a PID controller for position control. Then the performance of the proposed controller is verified via a numerical simulation under wind disturbance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.712-718
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• 2008

This paper deals with a development of flight control law switching system which can be used for flight test of the research control law by switching control law during flight. Through this research program, fader logic and integrator stabilization design has been introduced to minimize the transient response of aircraft caused by flight control law switching and to prevent the divergence of the integrator included in the control law in standby mode. MIL-STD-1553B communication was applied to transfer the data between the two control laws. This paper introduce the control law switching system architecture and major design concept and include the system verification and validation result performed on the flying quality simulator of the advanced trainer.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.867-873
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• 2008

Model based virtual Flight Control System construction is essential for Fly-by-Wire Flight Control System verification & validation(V&V) of concurrent engineering base. We researched the concept of dual-architecture system for virtual system construction, and analyzed Flight Control System that is applied to high altitude long endurance(HAE) UAS. Finally, we constructed the model based virtual Flight Control System with system analysis and achieved system verification about flight critical failure modes. Analysis target is RQ-4A.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.316-323
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• 2016

A UAV(Unmanned Aerial Vehicle) flies along pre-programed navigation points(in-flight, take-off, or landing) automatically without pilot input. Even though UAVs fly differently from general piloted aircraft as the pilot controls the aircraft from a ground station through means of a data-link system. Occasionally, the data-link connection can be lost for any number of reasons, in which case, the FLCC(Flight control Computer) must automatically switch to autopilot to continue flying. Hence, the FLCC is a flight-critical component that must be throughly tested and validated. This paper discusses the development of a HILS(Hardware in the Loop Simulation) test environment designed to simulate real flight conditions to verify the FLCC satisfies flying quality requirements and maintains robustness despite any potential malfunctions or emergency situations.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.22-31
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• 2013

Flight tests on flight control performance of helicopter, conversion and airplane mode for the Smart UAV were completed. Automatic take-off and landing, automatic return home as well as automatic approach to hover were performed in helicopter mode. Climb/descent, left/right turn using speed and altitude hold mode were performed in each $10^{\circ}$ tilt angle in conversion mode. The rotor speed in airplane mode was reduced to 82% from 98% RPM in order to increase rotor efficiency with reducing Mach number at tip of rotors. It reached to the designed maximum speed, $V_{TAS}$=440 km/h at 3 km altitude. This paper presents the flight test result on full envelopment of Smart UAV. Detailed test plan and test data on control performance were also presented to prove that all data meets the flying qualities requirement.