• The Journal of Korea Robotics Society
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• v.18 no.3
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• pp.337-345
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• 2023

In this paper, we propose a 3D LiDAR sensor-based costmap generation and path planning algorithm using it for reliable autonomous flight in complex indoor environments. 3D path planning is essential for reliable operation of UAVs. However, existing grid search-based or random sampling-based path planning algorithms in 3D space require a large amount of computation, and UAVs with weight constraints require reliable path planning results in real time. To solve this problem, we propose a method that divides a 3D space into several 2D spaces and a path planning algorithm that considers the distance to obstacles within each space. Among the paths generated in each space, the final path (Best path) that the UAV will follow is determined through the proposed objective function, and for this purpose, we consider the rotation angle of the 2D space, the path length, and the previous best path information. The proposed methods have been verified through autonomous flight of UAVs in real environments, and shows reliable obstacle avoidance performance in various complex environments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.611-619
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• 2016

This paper proposes a collision prevention system for an agricultural unmanned helicopter. The collision prevention system consists of an obstacle detection system, a mapping algorithm, and a collision avoidance algorithm. The obstacle detection system based on a LiDAR sensor is implemented in the unmanned helicopter and acquires distance information of obstacles in real-time. Then, an obstacle mapping is carried out by combining the distance to the obstacles with attitude/location data of the unmanned helicopter. In order to prevent a collision, alert is activated to an operator based on the map when the vehicle approaches to the obstacles. Moreover, the developed collision prevention system is verified through flight test simulating a flight pattern aerial spraying.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.31 no.1
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• pp.18-25
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• 2023

In recent years, UAM (Urban Air Mobility) has emerged as a solution to these urbanization problems, and many related reports and diverse prospects have been reported. UAM flights are planned to take off and land at a Vertiport located in the city center and fly along a pre-established corridor. In order for UAM to operate safely in the city center, it must ensure a safe flight path that avoids the buildings in the city center and many surrounding obstacles. Therefore, in this study, we compared and examined the installation standards of the obstacle limitation surface necessary for UAM to take off and land safely at the Vertiport. First, we analyzed the helicopter obstacle limitation surfaces in Japan and overseas, and the UAM Vertiport installation standards and obstacle limitation surface application standards recently announced at the FAA and EASA. It identified differences and similarities between heliport and Vertiport, and considered improvements to domestic helicopter obstacle limitation surfaces and criteria that could meet FAA and EASA standards.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.27 no.3
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• pp.106-111
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• 2019

Pilot has been fighting to get over fatigue during flight and thought it as a hinderance for safe flight. The fatigue related problem has been the biggest obstacle for aviation safety so far. Even though pilots and airlines try their best to overcome fatigue during flight, they couldn't overcome this problem. So the airliners let the pilot sleep during flight if pilots are too tired with the report. It is controlled rest used and managed by several European airliners. So this study tries to get Korean airline pilots' fatigue information and figure out the cause and reduce it.

• Journal of the Korea Computer Graphics Society
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• v.27 no.5
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• pp.63-71
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• 2021

Among drone autonomous flight technologies, obstacle avoidance is a very important technology that can prevent damage to drones or surrounding environments and prevent danger. Although the LiDAR sensor-based obstacle avoidance method shows relatively high accuracy and is widely used in recent studies, it has disadvantages of high unit price and limited processing capacity for visual information. Therefore, this paper proposes an obstacle avoidance algorithm for drones using camera-based PPO(Proximal Policy Optimization) reinforcement learning, which is relatively inexpensive and highly scalable using visual information. Drone, obstacles, target points, etc. are randomly located in a learning environment in the three-dimensional space, stereo images are obtained using a Unity camera, and then YOLov4Tiny object detection is performed. Next, the distance between the drone and the detected object is measured through triangulation of the stereo camera. Based on this distance, the presence or absence of obstacles is determined. Penalties are set if they are obstacles and rewards are given if they are target points. The experimennt of this method shows that a camera-based obstacle avoidance algorithm can be a sufficiently similar level of accuracy and average target point arrival time compared to a LiDAR-based obstacle avoidance algorithm, so it is highly likely to be used.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.515-522
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• 2012

CFIT(Controlled Flight Into Terrain) is one of the major causes of aircraft accidents. In order to solve this problem, GPWS(Ground Proximity Warning System) is used to generate terrain collision warning using the distance between the aircraft and the underneath ground. Since the GPWS uses the vertical clearance only, it frequently generates false warnings. In this study, a terrain/obstacle collision avoidance warning algorithm was developed for fast flying and highly maneuvering fighters using the flight status and the geographic information. This algorithm condsiders the overall delay in the aircraft reactive motion including the pilot's reaction time. The paper presents a detailed logic and test methods.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.6
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• pp.448-453
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• 2023

As the production of small quadcopter drones has diversified and multi-sensors have been installed in FC due to the spread of MCU capable of high-speed processing, small drones that can perform special-purpose operations rather than simple operations have been realized. Hovering, attitude control, and position movement control were possible through the IMU in the FC mounted on the drone, but control is not easy when GPS connection and video communication are not possible in a closed building with a complex structure. In this study, when encountering an obstacle with a change in altitude in such a space, we proposed a method to overcome the obstacle and perform autonomous flight using optical flow and IR sensors using the Lucas-Kanade method. Through experiments, the drone's altitude flight on stairs that replace the complex structure of a closed space with stable hovering motion has a success rate of 98% within the tolerance of 10 [cm] due to external influences, and reliable autonomous flight up and down is achieved.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.4
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• pp.93-99
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• 2020

It seems to be increased rapidly that practical uses of intelligent Dron for public mission performance such as surveillance, prevention of disaster accident, relief etc with Dron technology development. Dron is needed for major technology realization of detection and trace technology of target, flight control and obstacle avoidance during flighting, detection and control of landing point functions to use smart safety-city platform construction. This dron system cause a great ripple effect technically and promote industrialization in the field of new technology. In this paper, an effective analysis and design method of dron system software will be presented by showing user requirement analysis using object-oriented method, flowchart and screen design.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.5 no.1
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• pp.65-79
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• 1997

In this study, we deviced side warning system that is necessary to the ground operation of aircraft. The system consist of obstacle detection part, transmission part, receive part, and warning part. We used TOF(Time Of Flight) method using 40kHz ultrasonic wave as the obstacle detection part. The 447MHz RF module was applied to the transmission and receive part. The warning part is activated by the computer using received distance data. The detection system attach to the left/right side edge of main wing and horizontal stabilizer. We have decided 10m obstacle detection range. The result of experiment was satisfactory.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.4
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• pp.20-25
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• 2016

A primary benefit of flight at high angle-of-attack conditions is to be able to reduce the speed of flight and maneuvers, which can enhance the capability of sensing and obstacle avoidance for a small UAV. The flight at high angle-of-attack conditions, however, is easy to be beyond stall which is characterized by substantial flow separation over an airfoil. Current numerical analysis was conducted on the capabilities of three representative turbulence models to predict the aerodynamic characteristics of a typical airfoil at angle-of-attack conditions. The investigation shows that these turbulence models provide good comparison with experimental data for attached flow at moderate angle-of-attack conditions. Calculation by current turbulence models are, however, not appropriate at high angle-of-attack conditions with flow separation.