• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.7
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• pp.581-593
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• 2017

In order to develop high efficiency propeller for multicopter type UAV, we designed, analyzed and tested aerodynamic and structural dynamics. For the design of the high efficiency propeller, the optimum design method was applied for the determination of the airfoil and the three-dimensional planform is designed to reduce induced power of the propeller. The flight suitability of the derived shape was determined through structural design and analysis. The rotation test was performed to confirm the performance of the analytically designed shape. In this paper, we propose a procedural propeller design methodology using these design analysis test methods.

• Current Industrial and Technological Trends in Aerospace
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• v.4 no.1
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• pp.34-43
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• 2006

헬기는 비행에 필요한 추력, 모멘트 및 조종력을 회전하는 로터시스템에서 발생시키기 때문에 근본적으로 진동이 많이 생기는 항공기이다. 로터시스템의 회전에 의해 발생되는 진동소스를 제어함으로써 헬기 동체에 전달되는 진동을 감소시키고자 하는 연구들이 지금까지 수많이 진행되었다. 이러한 연구들을 크게 두 가지로 분류하면, 수동적 진동제어 방법과 능동적 진동제어 방법으로 나눌 수 있다. 수동적 진동제어 방법은 그간 오랫동안 연구되어 현재 운용 헬기에 실제적으로 적용되고 있으나 능동적 진동제어 방법은 최근까지 활발한 연구가 진행되고 있는 상태이다. 본 논문의 서론에서는 헬기 진동제어를 위한 일반적인 방법에 대한 개요를 소개하였다. 본문은 로터시스템 진동제어 기술 중 최근까지 연구가 진행되고 있는 능동적 진동제어 방법을 중심으로 기술하였다. 특히 최근 비행시험에 성공하여 거의 실용화 단계에 이르고 있는 PZT를 이용한 Trailing Edge Flap 기술, Active Twist Rotor 등을 중점적으로 소개하였다. 마지막으로 유로콥터 BK117의 ADASYS 로터 시스템 성공사례 및 향후 해결해야 할 기술적 제한사항 등을 간략하게 기술하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.1
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• pp.81-88
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• 2006

In this paper, we analyze a noncommutativity error that is not able to be compensated with integrating gyro outputs in RLG-based INS. The system can suffer from some motion known as RLG dithering motion, coning motion, ISA motion derived by an AV mount and vehicle real dynamic motion. So these motions are a cause of the noncommutativity error, the system error derived by each motion has to be analyzed. For the analysis, a relation between rotation vector and gyro outputs is introduced and applied to define the coordinate transformation matrix and the angular vector.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.98-104
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• 2004

A spacecraft alignment measurement requires highly precise measurement accuracy which is less than ${\pm}0.5^{\circ}$. In general, such an alignment measurement has been performed by using three or more theodolites. However, it contains the latent accuracy error because of a position stability of spacecraft, etc. The new alignment measurement system which consists of a theodoilte, a rotating table and a digital inclinometer has been developed to possibly to possibly reduce the error. This paper describes the concept and methodology of methodology of measurement system. It was found that new measurement system can provide more accurate results than the conventional system.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.174-180
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• 2006

The present paper describes transient thermal and mechanical analyses of a lox/kerosene type turbopump in a LRE(Liquid Rocket Engine). Turbopumps are used to pressurize propellants to achieve higher specific impulse of LRE. The turbopump under development has been designed and verified by structural analyses using finite element methods. Some parts of the turbopump operate under cryogenic environments, while the others work under ambient and high temperature environments. Therefore, numerical analysis at a turbopump system level is essential. In this study, casing assemblies of lox pump and fuel pump were analyzed to determine strength test and air-tightness test conditions. Also, some operational stress and strains of fuel pump casings were measured and analyzed. Based on these results, stress concentration of fuel pump casings during the operation could be successfully predicted.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.240-247
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• 2006

Tilt rotor aircraft is a multi-configuration airplane which has three independent flight modes; helicopter, conversion, and aiplane. The control surface mixer resign is reqctired to generate and distribute efficient control forces and moments in each flight mode. In the conversion mode, the thrust vector is changed from helicopter mode to airplane, therefore the thrust vector makes undesired forces and moments which affect on pitch, roll and yaw dynamics. This paper describes the design results of control surface mixer design which minimize the undesired forces and moments due to nacelles tilting angle change for 4O% scaled model.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.105-110
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• 2013

The gimbal expansion joint for the pipe line of a liquid rocket engine undergoes high pressure and cyclic rotational displacement loadings. In present study, the moment analyses and tests of the internal-type gimbal expansion joint for the engine were performed. The moment components due to spring stiffness, friction and lateral force were obtained using a analytic method and their sums at low and high pressures were compared with the test results. Also, applying a $MoS_2$ dry film lubricant to the pin of a external hinge expansion joint, it is tested that the galling of the pin was removed and the friction coefficient was decreased for low pressures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.63-68
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• 2003

Shot peening process is most often used to improve the fatigue properties of metal parts, In order to achieve an optimum, repeatable, and reliable fatigue enhancement from the shot peening process, the important shot peening parameters must be optimized, In this paper, the optimum peening intensity(Almen intensity) condition is investigated by experiment. Rotary bending fatigue test has been adopted to investigate the effects of optimum peening on the fatigue characteristics, Experimental results show that the fatigue strength and fatigue life has been tremendously increased by optimum-peening treatment. However, the fatigue strength and fatigue life has been decreased by under or over peening.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.3
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• pp.224-231
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• 2009

In this study, an aerodynamic performance analysis code has been developed as a part of rotorcraft comprehensive program. Airloads on rotor blades are calculated based on the blade element theory with look-up tables of aerodynamic coefficients of 2-D airfoils. In order to calculate rotor induced inflow, various inflow prediction methods such as linear inflow, dynamic inflow, prescribed wake and free wake model are integrated into the present module. The aerodynamic characteristics of each method are compared and validated against available experimental data such as Elliot's inflow distribution and sectional normal force coefficients of AH-1G.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.4
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• pp.301-309
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• 2021

Pulse count method is the classical reaction wheel speed detection method. In this study, we represent the pulse count method as mathematical equations. Instead of rotation speed, we model the reaction wheel rotation through rotation angle during sampling periods. We verified the effectiveness of the proposed model by comparing the pulse counts variation and averaging method effects from the model and previous research results. Then, we add tacho pulse non-uniformity to this verified model, and examine the errors of pulse count method. We express the measurement error increasement due to non-uniformity as mathematical equations, and also shows the requirement of moving average numbers to offset the measurement errors.