• 한국항해항만학회지
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• 제36권3호
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• pp.215-223
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• 2012

플로팅 함체의 강성변화가 상부 철골모멘트연성골조에 미치는 영향을 확인하기 위해 함체의 높이를 1.5m, 2.0m, 2.5m로 변화시키면서 파랑하중 3초에서 15초에 대하여 동적 유체 해석과 그에 따른 파력을 산정하고 정적 구조 해석을 수행하였다. 해석결과, RAO-피치와 상부 골조의 모멘트 증가량이 선형적인 관계이고 함체의 곡률이 구조물의 강성과 반비례함을 확인하였다. 이러한 선형적 결과를 종합하여, 임의의 함체에 대한 상부골조의 해석 결과를 이용하여 함체 높이가 다른 경우에도 상부 골조의 모멘트를 추정하는 절차를 제안하였으며, 추정결과가 해석결과와 상당히 잘 일치함을 확인하였다.

• 한국항행학회논문지
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• 제27권3호
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• pp.287-292
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• 2023

고정형 CCTV의 경우 팬-틸트(pan-tilt)와 줌(zoom) 기능을 활용하여 가시범위를 최대화하더라도 음영지역이 발생하는 문제가 있다. 이에 대한 대표적인 해결방안으로 다수의 고정형 CCTV를 운영하는 것이다. 이는 CCTV의 개수와 비례한 다량의 부가장비(예: 전선, 설비, 모니터 등)가 필요하다. 다른 해결방안으로 드론을 활용하는 것이다. 문제는 운영시간에 대하여 고정형 CCTV 대비 훨씬 짧다. 운영시간을 연장하기 위해 다수의 드론을 활용하여 한 대씩 임무를 교대하면서 수행하는 방식이 있다. 이 경우 배터리 충전이 필요한 드론은 드론 포트(drone port)에서 준비상태(재충전 완료)로 재진입하여 연속된 임무가 가능하게 하는 것이다. 본 논문은 고정된 전방을 향한 단안 카메라가 탑재된 초소형 드론을 활용하여 방범용 CCTV의 기능으로 활용될 때, 원격지에서 효율적인 운영과 후속 임무의 원활한 연속 수행을 위한 드론포트에 안정적인 착지를 위한 시스템을 제안하고 구현한다. 그리고 이에 대한 운영을 통해 활용 가능성을 입증한다.

• International Journal of Control, Automation, and Systems
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• 제5권4호
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• pp.397-409
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• 2007

In this paper, we propose a nonlinear guidance law for missiles against maneuvering targets. First, we derive the equations of motion described in the line-of-sight reference frame and then we define the equilibrium subspace of the nonlinear system to guarantee target interception within a finite time. Using Sontag's formula, we derive a nonlinear guidance law that always delivers the state to the equilibrium subspace. If the speed of the missile is greater than that of the target, the proposed law has global capturability in that, under any initial launch conditions, the missile can intercept the maneuvering target. The proposed law also minimizes the integral cost of the control energy and the weighted square of the state. The performance of the proposed law is compared with the augmented proportional navigation guidance law by means of numerical simulations of various initial conditions and target maneuvers.

• International Journal of Aeronautical and Space Sciences
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• 제13권3호
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• pp.369-376
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• 2012

A nonlinear robust guidance law is designed for missiles against a maneuvering target by incorporating sliding-mode and optimal control theories based on the state dependent Riccati equation (SDRE) to achieve robustness against target accelerations. The guidance law is derived based on three-dimensional nonlinear engagement kinematics and its robustness against disturbances is proved by the second method of Lyapunov. A new switching surface is considered in the sliding-mode control design. The proposed guidance law requires the maximum value of the target maneuver, and therefore opposed to the conventional augmented proportional navigation guidance (APNG) law, complete information about the target maneuver is not necessary, and hence it is simple to implement in practical applications. Considering different types of target maneuvers, several scenario simulations are performed. Simulation results confirm that the proposed guidance law has much better robustness, faster convergence, and smaller final time and control effort in comparison to the sliding-mode guidance (SMG) and APNG laws.

• 한국정밀공학회지
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• 제31권1호
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• pp.43-50
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• 2014

This paper introduces a robot platform which can do weeding while traveling between rice seedlings stably against irregular land surface of a paddy field. Also, an autonomous navigation technique that can track on stable state without any damage of the seedlings in the working area is proposed. Detection of the rice seedlings and avoidance knocking down by the robot platform is achieved by the sensor fusion of a laser range finder (LRF) and an inertial measurement unit (IMU). These sensors are also used to control navigating direction of the robot to keep going along the column of rice seedling consistently. Deviation of the robot direction from the rice column that is sensed by the LRF is fed back to a proportional and derivative controller to obtain stable adjustment of navigating direction and get proper returning speed of the robot to the rice column.

• International Journal of Aeronautical and Space Sciences
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• 제11권2호
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• pp.69-79
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• 2010

This paper describes the experimental framework for the control system design and validation of a rotorcraft unmanned aerial vehicle (UAV). Our approach follows the general procedure of nonlinear modeling, linear controller design, nonlinear simulation and flight test but uses an indoor-installed multi-camera system, which can provide full 6-degree of freedom (DOF) navigation information with high accuracy, to overcome the limitation of an outdoor flight experiment. In addition, a 3-DOF flying mill is used for the performance validation of the attitude control, which considers the characteristics of the multi-rotor type rotorcraft UAV. Our framework is applied to the design and mathematical modeling of the control system for a quad-rotor UAV, which was selected as the test-bed vehicle, and the controller design using the classical proportional-integral-derivative control method is explained. The experimental results showed that the proposed approach can be viewed as a successful tool in developing the controller of new rotorcraft UAVs with reduced cost and time.

• 제어로봇시스템학회논문지
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• 제12권7호
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• pp.693-699
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• 2006

An accurate and compact map is essential to an autonomous mobile robot system. For navigation, it is efficient to use an occupancy grid map because the environment is represented by probability distribution. But it is difficult to apply it to the large environment since it needs a large amount of memory proportional to the environment size. As an alternative, a topological map can be used to represent it in terms of the discrete nodes with edges connecting them. It is usually constructed by the Voronoi-like graphs, but in this paper the topological map is incrementally built based on the local grid map using the thinning algorithm. This algorithm can extract only meaningful topological information by using the C-obstacle concept in real-time and is robust to the environment change, because its underlying local grid map is constructed based on the Bayesian update formula. In this paper, the position probability is defined to evaluate the quantitative reliability of the end nodes of this thinning-based topological map (TTM). The global TTM can be constructed by merging each local TTM by matching the reliable end nodes determined by the position probability. It is shown that the proposed TTM can represent the environment accurately in real-time and it is readily extended to the global TTM.

• 한국전자파학회논문지
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• 제29권4호
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• pp.256-265
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• 2018

본 논문에서는 PN 유도 법칙을 기반으로 동작하는 능동 RF 탐색기에 대한 반복형 능동 유인체의 재밍 환경에서 공중 플랫폼의 생존성을 분석한다. 플랫폼의 기동, 유인체의 RF 제원(spec), 탐색기의 접근 거리 및 방향 등 다른 조건의 여러 조우 시나리오에서 플랫폼에 대한 탐색기의 miss distance를 계산한다. Miss distance와 근접신관거리와의 비교를 통해 플랫폼의 생존 여부를 판별하며, 이를 기반으로 몇몇 조우 시나리오에서 플랫폼 생존 영역을 도출한다.

• International Journal of Aeronautical and Space Sciences
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• 제12권3호
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• pp.274-282
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• 2011

This paper is focused on dynamic modeling and control system design as well as vision based collision avoidance for multi-rotor unmanned aerial vehicles (UAVs). Multi-rotor UAVs are defined as rotary-winged UAVs with multiple rotors. These multi-rotor UAVs can be utilized in various military situations such as surveillance and reconnaissance. They can also be used for obtaining visual information from steep terrains or disaster sites. In this paper, a quad-rotor model is introduced as well as its control system, which is designed based on a proportional-integral-derivative controller and vision-based collision avoidance control system. Additionally, in order for a UAV to navigate safely in areas such as buildings and offices with a number of obstacles, there must be a collision avoidance algorithm installed in the UAV's hardware, which should include the detection of obstacles, avoidance maneuvering, etc. In this paper, the optical flow method, one of the vision-based collision avoidance techniques, is introduced, and multi-rotor UAV's collision avoidance simulations are described in various virtual environments in order to demonstrate its avoidance performance.

• 한국항공우주학회지
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• 제50권6호
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• pp.393-400
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• 2022

고고도 교전 시 사용되는 궤도수정 및 자세제어 시스템(Divert and Attitude Control System, DACS)은 고가이며 복잡하다. 본 논문에서는 비교적 단순하고 저가인 추력벡터제어(Thrust Vector Control, TVC)를 탑재한 유도탄의 고고도 종말 유도조종 루프를 제안한다. 본 유도조종 루프는 쿼터니언 피드백 제어기법을 이용하여 진 비례항법유도로 산출된 가속도 명령으로부터 변환된 추력 자세각 명령을 추종하며 유도를 수행한다. 고고도에서 탄도탄에 대한 교전 시뮬레이션을 통하여 제안한 유도조종 루프의 성능을 분석한다.