• International Journal of Aeronautical and Space Sciences
• /
• 제16권4호
• /
• pp.614-623
• /
• 2015

When the speed of a coaxial rotor helicopter in forward flight increases, the wake skew angle of the rotor increases and consequently the position of the vena contracta of the upper rotor with respect to the lower rotor changes. Considering ambient air and the effect of the upper rotor, this study proposes a nonuniform inflow model for the lower rotor of a coaxial rotor helicopter in forward flight. The total required power of the coaxial rotor system was compared against Dingeldein's experimental data, and the results of the proposed model were well matched. A plant model was also developed from first principles for flight simulation, unknown parameter estimation and control analysis. The coaxial rotor helicopter used for this study was manufactured for surveillance and reconnaissance and does not have any stabilizer bar. Therefore, a feedback controller was included during flight test and parameter estimation to overcome unstable situations. Predicted responses of parameter estimation and validation show good agreement with experimental data. Therefore, the methodology described in this paper can be used to develop numerical plant model, study non-uniform inflow model, conduct performance analysis and parameter estimation of coaxial rotor as well as other rotorcrafts in forward flight.

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

• International Journal of Aeronautical and Space Sciences
• /
• 제12권3호
• /
• pp.252-259
• /
• 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.

• 한국통신학회논문지
• /
• 제35권11B호
• /
• pp.1732-1737
• /
• 2010

현재 군에서 무인기를 운용하는 주목적 중 하나는 적에 대한 감시/정찰이다. 이를 위해 무인기는 정보감시/정찰(ISR) 장비들을 탑재하여, 감시/정찰 대상에 대한 영상 데이터를 획득한 후 지상통제소로 전송한다. 지상통제소는 전송된 영상 데이터를 수신한 후, 다양한 사용자에게 배포하게 되는 데, 이 때 품질 보장을 유지하는 것이 중요하다. 본 논문에서는 DDS 표준 프로토콜을 사용하여 무인기의 영상전송 및 품질보장을 관리하는 방안을 제시하였다. 이에 대해 H.264 및 JPEG2000 영상 데이터를 이용하여 영상전송 실험결과 DDS 표준이 UAS 운용에 활용 가능함을 보였다.

• 융합보안논문지
• /
• 제20권1호
• /
• pp.69-75
• /
• 2020

지휘통제체계는 인간의 두뇌와 신경 조직처럼 정보·감시·정찰(ISR)에서 정밀타격체계(PGR)를 연결하는 링커이며 전투력의 중심이다. 미래 한국군의 지휘통제체계 구축시 기술적 문제뿐만 아니라 제도적 문제를 함께 고려해야 한다. 미국 국방부는 지휘 통제체계 개발에 앞서 보안 정책을 수립하고 이를 구체화하여 아키텍처 문서로 정리하며, 이를 토대로 보안 정책의 일관성과 지속을 유지한다. 본 논문에서는 미군의 지휘통제체계 구축시 적용하는 보안 아키텍처를 살펴보고 현행 한국군의 보안 관련 정책(규정)을 분석하여 미래 지휘통제체계 구축 시 보안 요구사항을 식별한다. 식별된 보안 요구사항을 그룹핑하여 현행 보안 관련 규정의 분야별 개선사항을 도출하여 제시하고자 한다.

• 한국광학회지
• /
• 제18권2호
• /
• pp.135-141
• /
• 2007

완전한 2차원 배열을 갖는 중적외선 대역의 $320\times240$ 검출기를 사용하는 3세대 열상 장비의 설계 및 제작은 이차원 배열 검출기 제작 기술의 발달과 영상 신호처리 기술의 진전으로 인해 최근 더욱 더 활발히 이루어지고 있다. 본 논문은 다양한 응용 분야에서 적외선 센서로 사용될 수 있도록 하기 위하여 소형 경량화 제작을 목표로 한 3세대 열상장비의 이중 배율 적외선 카메라의 설계와 Defocus용 셔터 렌즈에 의한 영상기반 불균일 보정 방식에 대해 다룬다.

• 산업경영시스템학회지
• /
• 제34권3호
• /
• pp.24-34
• /
• 2011

An Unmanned Aerial Vehicle (UAV) is a powered pilotless aircraft, which is controlled remotely or autonomously. UAVs are an attractive alternative for many scientific and military organizations. UAVs can perform operations that are considered to be risky or uninhabitable for human. UA V s are currently employed in many military missions such as reconnaissance, surveillance, enemy radar jamming, decoying, suppression of enemy air defense (SEAD), fixed and moving target attack, and air-to-air combat. UAVs also are employed in a number of civilian applications such as monitoring ozone depletion, inclement weather, traffic congestion, and taking images of dangerous territory. For accomplishing the UAV's missions, guarantee of survivability should be preceded. The main objective of this study is to suggest a mathematical programming model and a $A^*PS$-PGA (A-star with Post Smoothing-Parallel Genetic Algorithm) for an UAV's path planning to maximize survivability. A mathematical programming model is composed by using MRPP (Most Reliable Path Problem) and TSP (Traveling Salesman Problem). A path planning algorithm for UAV is applied by transforming MRPP into SPP (Shortest Path Problem).

• 대한조선학회논문집
• /
• 제48권1호
• /
• pp.8-14
• /
• 2011

RIB(Rigid Inflatable Boat) is widely used for coastal transportation in the commercial use and for ISR(Intelligence, Surveillance, Reconnaissance) in the military use. Since RIB is around 10 meters in length and over 30 knots in speed, its motion characteristics in waves is quite different from a large scale ship. When it turns, large roll occurs and heeling direction is opposite to the large ship's case. Currently, many countries are developing USV(Unmanned Surface Vehicle) of which type is RIB. In order to develop high performance autopilot and way point controller, it is very important to identify RIB's motion characteristics. In this paper, sea trial test results of a 7-meter RIB such as speed, turning, zig-zag, and way point control tests were represented and its resistance and propulsion model was identified by using sea trial data and Savitsky's formula. In addition, the state space model which will be used in the identification of the four-degree-of-freedom dynamics in the next step was formulated and the identification procedure was proposed.

• 전기학회논문지
• /
• 제65권7호
• /
• pp.1225-1230
• /
• 2016

Since a flash light produces enormous amount of photon energy in short time, not only electro-optic and infrared(EO/IR) systems utilized for Intelligence Surveillance Target Acquisition and reconnaissance(ISTAR) activities but also the people of a combat field can be severely influenced by a high flash light bursting in front of them. The people who bumped into a flash could not escape such enormous amount of photon energy, resulting in being blind temporarily or even permanently. In order to investigate the effect of a high flash source on a human eye, it is essential to know how much photon energy be incident into an eye from the flash source. In this paper, the model of irradiated photon energy to individuals from some flashes is proposed. The proposed irradiated photon energy per unit area of retina is based on taking the situation to be modeled as a simple EO system in front of a flash light. The validity of proposed model was proved by the application of the model to human on the surface of the earth with the well known light source, the Sun. The model of this study can be utilized to simulate the retinal intensity and energy of a flash for various conditions such as the illumination levels, the distance from a flash busting site, luminous intensity and time of a flash.

• Ocean Systems Engineering
• /
• 제10권4호
• /
• pp.373-397
• /
• 2020

Heave compensation is a vital part of various marine and offshore operations. It is used in various applications, including the transfer of cargo between two vessels in the open ocean, installation of topsides of an offshore structure, offshore drilling and for surveillance, reconnaissance and monitoring. These applications typically involve a load suspended from a hydraulically powered winch that is connected to a vessel that is undergoing dynamic motion in the ocean environment. The goal in these applications is to design a winch controller to keep the load at a regulated height by rejecting the net heave motion of the winch arising from ship motions at sea. In this study, we analyze and compare the performance of various control algorithms in stabilizing a suspended load while the vessel is subjected to changing sea conditions. The KCS container ship is chosen as the vessel undergoing dynamic motion in the ocean. The negative of the net heave motion at the winch is provided as a reference signal to track. Various control strategies like Proportional-Derivative (PD) Control, Model Predictive Control (MPC), Linear Quadratic Integral Control (LQI), and Sliding Mode Control (SMC) are implemented and tuned for effective heave compensation. The performance of the controllers is compared with respect to heave compensation, disturbance rejection and noise attenuation.