• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권4호
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• pp.1351-1372
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• 2022

A self-organizing multiple unmanned aerial vehicles (multi-UAVs) deployment based on virtual forces has a difficulty in ensuring the quality-of-experience (QoE) of users because of the difference between the assumed center for users in a hotspot and an actual center for users in the hotspot. This discrepancy is aggravated in a non-uniform and mobile user distribution. To address this problem, we propose a new density based virtual force (D-VF) multi-UAVs deployment algorithm which employs a mean opinion score (MOS) as a metric of QoE. Because MOS is based on signal-to-noise ratio (SNR), a sum of users' MOS is a good metric not only to secure a wide service area but to enhance the link quality between multi-UAVs and users. The proposed algorithm improves users' QoE by combining virtual forces with a random search force for the exploration of finding multi-UAVs' positions which maximize the sum of users' MOS. In simulation results, the proposed deployment algorithm shows the convergence of the multi-UAVs into the position of maximizing MOS. Therefore, the proposed algorithm outperforms the conventional virtual force-based deployment scheme in terms of QoE for non-uniform user distribution scenarios.

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

• 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.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.315-326
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• 2017

Four quadrotor UAVs are maneuvered to guide four animals into their pen within the minimum time by creating noises of predators modeled with an exponential function. The quadrotor UAVs are controlled via PID controllers, follow time optimal trajectories, and avoid collisions through altitude separations. The stability of the proposed PID controller is analyzed and verified using MATLAB/Simulink based simulations. Proposed step by step strategies would be practical solutions of actual cattle roundup problems.

• International Journal of Aeronautical and Space Sciences
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• 제8권2호
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• pp.107-120
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• 2007

Coordination of multiple UAVs is an essential technology for various applications in robotics, automation, and artificial intelligence. In general, it includes 1) waypoints assignment and 2) trajectory generation. In this paper, we propose a new method for this problem. First, we modify the concept of the standard visibility graph to greatly improve the optimality of the generated trajectories and reduce the computational complexity. Second, we propose an efficient stochastic approach using simulated annealing that assigns waypoints to each UAV from the constructed visibility graph. Third, we describe a method to detect collision between two UAVs. FinallY, we suggest an efficient method of controlling the velocity of UAVs using A* algorithm in order to avoid inter-UAV collision. We present simulation results from various environments that verify the effectiveness of our approach.

• 시스템엔지니어링학술지
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• 제18권1호
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• pp.14-32
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• 2022

In this paper, we report the results of a conceptual study to develop of a multi-purpose medium-sized UAV that can safely perform missions in harsh maritime environments. In this study, we focused on developing UAVs capable of performing three maritime missions that urgently require the application of medium-sized UAVs: marine ecosystem management, ocean surveillance system, and response to marine accidents. Furthermore improvement points for the above three naval missions using medium-sized UAVs were derived in preparation for the problems of the existing mission performance. Finally, by developing and analyzing the utilization scenario of the medium-class UAV, the required performance suitable for each mission was defined and assigned to the related mission equipment, A new maritime management plan was proposed using the medium-class UAV system equipped with replaceable mission equipment.

• 한국항공우주학회지
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• 제36권6호
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• pp.565-573
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• 2008

본 연구에서는 다수 무인기의 군집비행을 위한 행위기반 분산형 제어기법을 제안한다. 각 무인기는 특정한 영역으로 비행해야하는 고유의 임무와 동시에 무인기 간의 거리를 유지해야하는 요구조건도 가지고 있다. 이러한 두 가지 요구조건은 서로 상충된다. 제어기를 설계하기 위하여 각 무인기가 통신채널을 통하여 상태변수를 교환할 수 있다는 가정 하에 결합형 동역학을 적용하였다. 군집비행의 성능을 개선하기 위하여 제어이득 행렬의 최적화를 수행하였다. 제어기의 성능을 평가하기 위하여 다수 무인기의 경로점 통과 임무를 위한 수치 시뮬레이션을 수행하였다.

• 한국항공우주학회지
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• 제43권6호
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• pp.488-496
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• 2015

본 연구에서는 각각 다른 목적지에서 다수의 임무를 수행해야하는 복수 무인항공기(Unmanned Aerial Vehicle, UAVs)의 경로를 결정할 때, 무인항공기의 생존가능성을 고려하여 경로를 결정하는 프레임워크를 제안하였다. 본 라우팅 문제는 무인항공기 안전과 임무 완료시간 간의 trade-off 를 나타내는 비용 매트릭스를 이용한 차량경로문제(Vehicle Routing Problem, VRP)로 정의할 수 있다. 특정위치에서 무인항공기의 위험 레벨은 감지될 확률과 격추될 확률을 고려하여 모델링 하였고, 위협 레벨과 비행거리를 고려한 두 지역간의 최소비용경로는 육각형격자(Hexagonal cells)에서 Dijkstra 알고리듬을 사용하여 결정하였다. 또한, 지속적으로 다수의 적을 감시 정찰하는 임무를 수행하는 복수 무인항공기의 최적경로를 결정하는 case study를 수행하였으며, 그 결과를 논의하였다.

• 제어로봇시스템학회논문지
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• 제21권1호
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• pp.7-13
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• 2015

Unmanned air vehicles (UAVs) are getting popular not only as a private usage for the aerial photograph but military usage for the surveillance, reconnaissance and supply missions. For an UAV to successfully achieve these kind of missions, geolocation (localization) must be implied to track an interested target or fly by reference. In this research, we adopted multi-sensor fusion (MSF) algorithm to increase the accuracy of the geolocation and verified the algorithm using two multicopter UAVs. One UAV is equipped with an optical camera, and another UAV is equipped with an optical camera and a laser range finder. Throughout the experiment, we have obtained measurements about a fixed ground target and estimated the target position by a series of coordinate transformations and sequential Kalman filter. The result showed that the MSF has better performance in estimating target location than the case of using single sensor. Moreover, the experimental result implied that multi-sensor geolocation algorithm is able to have further improvements in localization accuracy and feasibility of other complicated applications such as moving target tracking and multiple target tracking.

• 한국항공우주학회지
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• 제45권5호
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• pp.401-408
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• 2017

본 논문에서는 저가 하드웨어 기반의 멀티로터용 비행제어 컴퓨터의 하드웨어 개발과 항법 및 제어 알고리즘의 설계 및 구현, 그리고 실제 비행실험을 통한 검증 과정을 서술하였다. 개발된 비행제어 컴퓨터는 마이크로컨트롤러를 통하여 멀티로터를 안정적으로 제어하며 통합된 Linux 컴퓨터를 활용하여 복잡한 임무에 대응이 가능하도록 설계되었다. 항법 해는 Complementary Filter를 통하여 500 Hz의 속도로 계산을 수행하고, 멀티로터의 운동모델을 기반으로 Observer를 설계, 측정 잡음을 크게 줄였다. 제어 알고리즘은 3차원 Curve Fitting을 통하여 얻은 Feed-forward Term을 사용하여 반응속도를 크게 향상시켰으며, 다수의 비행실험을 통하여 실제 상황에서 효과적으로 동작함을 확인하였다.