• Journal of Biosystems Engineering
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• 제33권2호
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• pp.94-100
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• 2008

Present chemical application method using a power sprayer has been labor intensive, costly and ineffective. Therefore, a small agricultural unmanned helicopter was suggested to replace the conventional spray system. In this study, conceptual design for developing the helicopter and a consequential prototype were reported. The overall conceptual design was initiated by deciding the type of agricultural helicopter, as the single rotor helicopter with a tail system. As the first step of the designing, an air-cooled, 2-stroke engine was selected and a prototype transmission was designed by determining the rotating speed of main rotor shaft. A 'pusher' type tail rotor system was adapted to balance the reaction torque and reduce the power use. The tail boom length was designed to avoid the rotating trajectory of the main rotor. The RF console consisted of the engine control, attitude control, and emergency control modules. Assembling the prototype concluded the mechanical development of the agricultural helicopter.

• 한국기계가공학회지
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• 제10권1호
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• pp.87-92
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• 2011

This article proposes a new technique of the dynamic model using multi-body dynamic analysis tool for a flexible main spindle rotor system with a novel phase adjusting control technique for the purpose of an active control of rotor vibration. The dynamic model is used as a plant model. Also in order to make control system, a component parameters and phase controller is composed and simulated by SIMULINK. The vibration is reduced to 50%. Therefore the ADAMS dynamic model for the flexible main spindle rotor and the phase adjusting control techniques may be effective for the suppressing the vibration and helpful for the future active control for rotor vibration.

• 전기학회논문지
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• 제66권11호
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• pp.1657-1662
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• 2017

Rotor bar faults in induction machines, which are a part of main distribution of power system, can even stop the entire system by causing contact between a stator and a rotor. There are two methods of diagnosing rotor bar faults in induction motors, online and offline tests, and existing diagnosis methods have many limitations which can lead to misdiagnosis. This paper proposes a potable rotor bar faults diagnosis system based on single phase rotation test, one of offline test methods, which detects rotor bar faults through impedance interpretation by exciting AC current in a stator winding. The test was conducted on a motor of 0.4kW in the laboratory and a motor of 1500kW in industry field.

• Journal of Biosystems Engineering
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• 제35권4호
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• pp.215-223
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• 2010

In order to develop an precision aerial pesticide application system to be attached to an unmanned helicopter which can be applied to small lots of land, this study analyzed the flowing and spraying characteristics of the spray droplets by the main rotor downwash by setting the application conditions at the flight altitude of 3 m, the diameter of main rotor of 3.1 m, the boom length of around 2.8 m, and the spraying rate of 8 L/ha. The results of this study are summarized below. Through analysis of the covering area ratio of the spray droplets by main rotor downwash by nozzle type, boom with tilt angle and height, it was found that the covering area ratio of the twin flat-fan nozzle of around 25% was more uniform than other types of nozzle, also boom with $10^{\circ}$ tilt angle and spraying height of 3 m was shown to be the appropriate conditions for aerial application of pesticides. It was found that the nozzle position to minimize the scattering loss of spray droplets due to vortex phenomenon at both ends of the main rotor was around 10 cm from the end of the main rotor. An application test for the aerial pesticide application system attached to the HUA-ACEI unmanned helicopter developed by the Rural Development Administration showed that the range of covering area ratio of the spray droplets was 10-25%, and the spraying width was approximately 7 m when over 10% of covering area ratio was considered for valid spraying.

• 항공우주산업기술동향
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• 제8권1호
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• pp.118-130
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• 2010

본 논문에서는 헬리콥터 로터 허브 시스템 중 최신의 기술이 적용된 무베어링 허브 시스템에 대하여 적용된 기술에 대한 동향을 기술하였다. 먼저 헬리콥터 로터 허브시스템의 형태별 장단점을 분석하였으며, 무베어링 로터 허브 시스템이 타 허브 시스템에 비하여 갖는 고유의 특징에 대하여 기술하였다. 다음으로 무베어링 로터 허브 시스템의 주요 구성품에 대한 기능 및 역할, 특성에 대하여 기술하였다. 나아가 무베어링 로터 허브를 적용하고 있는 기 개발된 헬리콥터들의 사례에 대하여 기술하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.513-520
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• 2004

A steady-state/transient performance simulation model was newly developed for the propulsion system of the CRW (Canard Rotor Wing) type UAV (Unmanned Aerial Vehicle) during flight mode transition. The CRW type UAV has a new concept RPV (Remotely Piloted Vehicle) which can fly at two flight modes such as the take-off/landing and low speed forward flight mode using the rotary wing driven by engine bypass exhaust gas and the high speed forward flight mode using the stopped wing and main engine thrust. The propulsion system of the CRW type UAV consists of the main engine system and the duct system. The flight vehicle may generally select a proper type and specific engine with acceptable thrust level to meet the flight mission in the propulsion system design phase. In this study, a turbojet engine with one spool was selected by decision of the vehicle system designer, and the duct system is composed of main duct, rotor duct, master valve, rotor tip-jet nozzles, and variable area main nozzle. In order to establish the safe flight mode transition region of the propulsion system, steady-state and transient performance simulation should be needed. Using this simulation model, the optimal fuel flow schedules were obtained to keep the proper surge margin and the turbine inlet temperature limitation through steady-state and transient performance estimation. Furthermore, these analysis results will be used to the control optimization of the propulsion system, later. In the transient performance model, ICV (Inter-Component Volume) model was used. The performance analysis using the developed models was performed at various flight conditions and fuel flow schedules, and these results could set the safe flight mode transition region to satisfy the turbine inlet temperature overshoot limitation as well as the compressor surge margin. Because the engine performance simulation results without the duct system were well agreed with the engine manufacturer's data and the analysis results using a commercial program, it was confirmed that the validity of the proposed performance model was verified. However, the propulsion system performance model including the duct system will be compared with experimental measuring data, later.

• Journal of Biosystems Engineering
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• 제32권4호
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• pp.230-236
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• 2007

In this study, a tail rotor system for an agricultural RF controlled helicopter was developed and tested. This study concluded the mechanical development of the 'Agro-heli' by completing the tail rotor system and its radio console. The RF control system was closely related with the tail system for the control of flying attitude. The thrust of the tail system balance off the reaction torque, created by the main rotor. Lifting tests with and without the tail system were compared for estimating the consumption of power. The tail system would use $4{\sim}5%$ of the total power which was in an acceptable range. Flying performance and attitude was visually inspected. It showed reliable and safe control during the distance flying trials and could be adapted for utilization in aerial applications. Aerial application using an RF controlled agricultural helicopter may make precise and timely spraying possible.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제13권4호
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• pp.324-335
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• 2013

This article presents the design, control, and implementation of a small quad-rotor system under the practical limitation of being cost effective for private use, such as in the cases of control education or hobbies involving radio-controlled systems. Several practical problems associated with implementing a small quad-rotor system had to be taken into account to satisfy this cost constraint. First, the size was reduced to attain better maneuverability. Second, the main control hardware was limited to an 8-bit processor such as an AVR to reduce cost. Third, the algorithms related to the control and sensing tasks were optimized to be within the computational capabilities of the available processor within one sampling time. A small quad-rotor system was ultimately implemented after satisfying all of the above practical limitations. Experimental studies were conducted to confirm the control performance and the operational abilities of the system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1051-1057
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• 2000

A projected 100 kW APU gas turbine rotor-bearing system has a main outer shaft, which is composed of some numbers of segmented sections for manufacturing and assembly conveniences. For a secure assembly of the segmented sections a tie shaft or inner shaft is installed inside of the outer shaft and a tensional axial preload of 50,000 N is provided to it. In this paper it is intended to set-up a sound modeling method of the APU rotor system, and particularly, the influences of the tie shaft on the rotordynamic characteristics of the entire APU gas turbine rotor-bearing system are investigated. Analysis results show that as a conservative design practice the inner tie shaft should be actively modeled in the rotordynamic analysis of the APU rotor-bearing system, and its effects on the dynamic behaviors of the outer shaft should be thoroughly design-reviewed.

• 한국소음진동공학회논문집
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• 제22권2호
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• pp.187-192
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• 2012

Recently, KARI(Korea Aerospace Research Institute) has been developing a modern 11.5 m diameter four bladed bearingless main rotor system, and this rotor system can be used for 7,000 lb class helicopter. Flexbeam and torque tube can be considered as key structural components, and large elastic twist of flexbeam induced by pitch control motion of torque tube can influence the nonlinear aeroelastic behavior. In this paper, the dynamic characteristic analysis results of bearingless rotor system were presented. In order to construct a input model and validate the analysis procedures, calculated results using the comprehensive helicopter analysis program CAMRAD II were compared with the measured natural frequencies and lag damping data from small-scale wind tunnel test. Next, the analysis model was extended to a full-scale model, and the dynamic analysis results were presented.