• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.3
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• pp.293-300
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• 2009

The rotorcraft-based unmanned aerial vehicle(UAV) capable of performing close-range surveillance and reconnaissance has been developed. Trade studies on mission feasibility led to the adoption of a coaxial rotorcraft with twin rotors counter-rotating in one axis and driven by electric motors. A commercial off-the-shelf flight control computer(FCC) and a radio frequency modem were adopted for autonomous navigation. In order to achieve an aerial view, commercial charge-coupled device camera was also integrated into the vehicle. The performance of the completed vehicle was proved with manual flight test, and mission capability was verified through waypoint navigation flight after being equipped with FCC. This paper treats the whole process of design and system integration for development of the coaxial rotorcraft UAV.

• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.28-39
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• 2022

With the development of small multicopter PAV (Personal Air Vehicle), it is necessary to develop safety-related devices for manned rotorcraft. In this study, we assumed that an external airbag can be installed in a small multicopter PAV, and using LS-DYNA's Airbag Folding Application, we performed a free-fall collision analysis by modeling the airbag shapes consisting or Roll, Zigzag, and Sigma. There was no significant difference in the final airbag deployment time of the three models. However, when it collides with the ground during deployment, the Sigma fold type external airbag had the fastest deployment speed, applying the most impact force to the PAV, while the Roll fold type external airbag applied the smallest impact force to the PAV.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.997-1003
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• 2012

GNSS and ARS are the most common sensors in low-end UAVs. However, these sensors are vulnerable to built-in errors and cannot measure the body heading independently. The GNSS/INS cannot fully compensate the IMU errors in initial alignment process and rectilinear flights. For an unmanned helicopter, a magnetometer can be more useful than any other sensors to obtain heading information. However, the electric motor which drives small helicopter UAV keeps the magnetometer from reading the pure magnetotelluric vector. This paper shows the effects of electric motor on the magnetometer readings, and presents a method to compensate the effects. The results are verified with flight test data. The simulation and experimental results in this paper proves that aiding GNSS/INS with magnetometer increases observability and improves accuracy.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.840-848
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• 2013

Airworthiness certification of military aircraft is a government's certification that it must have airworthiness and ability to demonstrate its requested function and performance. NATO released STANAG-4671 to establish the minimum airworthiness requirements for UAVs between 150kg and 20,000kg MTOW in 2009. Up to now, there are no clear airworthiness certification criteria and guideline for small UAV which is less than 150kg. STANAG-4671 is used for military UAV airworthiness certification in Korea as Other Airworthiness Certification Criteria. However, since STANAG-4671 requires the same Target Level of Safety without regard to MTOW, excessive Target Level of Safety or design requirements could be applied to relatively small-medium UAV. In this paper, classification and criteria of airworthiness certification for military UAV were investigated and a Target Level of Safety was analyzed based on MTOW using ground victim criteria.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.2
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• pp.139-147
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• 2023

The compact tracking radar system is a pulsed radar tracking system that searches, detects, and tracks targets in real time against aircraft targets with a small RCS(Radar Cross Section) maneuvering at high speed. This paper describes the development of comprehensive performance test equipment to verify the performance of the radar system in a anechoic chamber environment. Describes the design and manufacture of comprehensive performance test equipment to meet requirements, including the generation of simulated target signals to simulate aircraft target signals to verify performance in the laboratory environment of radar systems. It also describes a GUI(Graphic User Interface) program to check performance through a test in conjunction with the tracking radar system. Verify the comprehensive performance test equipment implemented through the performance test.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.3
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• pp.128-133
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• 2018

Korean civil airworthiness requirements of powerplant system are regulated by KAS(Korean Airworthiness Standard) Part 23 and Part 33. These are equivalent to FAR Part 23, Part 33 of FAA, and CS-23 and CS-E of EASA. FAA and EASA rewrite the airworthiness requirements for small airplane. They changed current 'prescriptive regulation' to a 'performance-based regulation' which makes safety performance the objective. Powerplant requirements have also been changed extensively by this concept revolution. In accordance with this reorganization, we studied the new powerplant system requirements of FAR Part 23 and proposed ideal directions to rewrite the Korean Airworthiness Standard.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.16-26
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• 2023

With the growing demand for unmanned aerial vehicles (UAVs), various collision avoidance methods have been proposed, mainly using LiDAR and stereo cameras. However, it is difficult to apply these sensors to small UAVs due to heavy weight or lack of space. The recently proposed methods use a combination of object recognition models and distance sensors, but they lack information on the obstacle size. This disadvantage makes distance determination and obstacle coordination complicated in an early-stage collision avoidance. We propose a method for estimating obstacle sizes using a monocular camera-YOLO and infrared sensor. Our experimental results confirmed that the accuracy was 86.39% within the distance of 40 cm. In addition, the proposed method was applied to a small UAV to confirm whether it was possible to avoid obstacle collisions.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.2
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• pp.1-9
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• 2011

Several studies on the development for solar powered uninhabited aerial vehicles(UAVs) are under way as the use of the renewable energy becomes more and more important these days. This paper is for the conceptual design by a discrete and iterative method. An initial design point with 1.5 meter wing span is determined in the global design, which deploys the mass and energy balances among each component of UAV including solar cells and airframe. Then, the iteration for subsystems is carried out with the help of Vortex Lattice Method(VLM) to optimize the aircraft configuration and the solar power system. It is demonstrated in simulations that the optimized design increases the flight time from 62 to 120 minutes when the solar power system is installed. Also, the associated dynamic analysis reveals that the designed small aircraft has the acceptable stability and controllability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1124-1132
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• 2011

This paper deals with smooth path generation using B-spline for fixed-wing unmanned aerial vehicles manuevering in 2D environment. Hexagonal cell representation is employed to model the 2D environment, which features increased connectivity among cells over square cell representation. Subsequently, hexagonal cell representation enables smoother path generation based on a discrete sequence of path from the path planner. In addition, we present an on-line path smoothing algorithm incorporating B-spline path templates. The path templates are computed off-line by taking into account all possible path sequences within finite horizon. During on-line implementation, the B-spline curves from the templates are stitched together repeatedly to come up with a reference trajectory for UAVs. This method is an effective way of generating smooth path with reduced on-line computation requirement, hence it can be implemented on a small low-cost autopilot that has limited computational resources.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.387-391
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• 2009

The experimental study on the ducted fan for the propulsion system of a small UAV has been performed. In this paper, to investigate the three-dimensional unsteady flow field characteristics of the ducted fan, it was measured by using a $45^{\circ}$ inclined hot-wire from hub to tip at inlet, behind the rotor and outlet of the ducted fan. The hot-wire signal data was acquired at fixed yaw angle. The data was averaged by using the PLEAT (Phase Locked Ensemble Averaging Technique), and then three of non-linear equations were solved simultaneously by using the Newton-Rhapson numerical method. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential contour plot.