• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.842-845
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• 2000

It is essential to reduce stiction between the slider and the disk for super-smooth media such as glass disk for high density recording. We developed a stiction-reduced slider by fabricating mechanical bumps on the air bearing surface of the slider by indentation technique. This paper presents a possibility and concept of Stiction-Free-Slider which can operate on the data zone of a magnetic disk. The slider hat many bumps and their heights are in the tens of nm range. The SFS shows good performance on the data zone. Moreover, little wear of the bumps was observed when the preload was small.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.138-147
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• 1999

For autonomous navigation, a legged robot should be able to walk over irregular terrain and adapt itself to variation of supporting surface. Walking through slope is one of the typical tasks for such case. Robot needs not only to change foot trajectory but also to adjust its configuration to the slope angle for maintaining stability against gravity. This paper suggests such adaptation algorithm for stable walking which uses feedback of reaction forces at feet. Adjusting algorithm of foot trajectory was studied with the estimated angel of slope without visual feedback. A concept of virtual slope angle was introduced to adjust body configuration against slope change of the supporting terrain. Regeneration of foot trajectory also used this concept for maintaining its stable walking against unexpected landing point.

• 한국정밀공학회지
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• 제12권3호
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• pp.144-152
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• 1995

TV microphonic phenomenon (black patterns overlapped on the image when TV sound is set too high) was studied experimentally. It was found that this phenomenon was due to the vibration generated at speakers, and transmitted to the CRT through the TV cabinet structure. Based on this fact, a simulative study was carried out on the assumption that the vibratory motion of the shadow mask located in the CRT could cause the landing error of electronic beam. The result of the simulation corresponded qualitatively with experi- mentally observed facts.

• 전자통신동향분석
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• 제38권3호
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• pp.11-19
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• 2023

Drones, which were early operated by remote control, have evolved to enable autonomous flight by combining various sensors and software tools. In particular, autonomous flight of drones was possible since the application of GNSS-RTK (global navigation satellite system with real-time kinematic positioning), a precision satellite navigation technology. For instance, unmanned drone delivery based on GNSS-RTK data was demonstrated for pizza delivery in Korea for the first time in 2021. However, the vulnerabilities of GNSS-RTK should be overcome for delivery drones to be commercialized. In particular, jamming in the navigation system and low positioning accuracy in urban areas should be addressed. Solving these two problems can lead to stable flight, takeoff, and landing of drones in urban areas, and the corresponding solutions are expected to establish a hybrid positioning technology. We discuss current trends in hybrid positioning technology that can either replace or complement GNSS-RTK for stable drone autonomous flight.

• 한국항행학회논문지
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• 제19권1호
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• pp.1-6
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• 2015

전 세계적으로 급속하게 증가하는 항공교통량으로 인해 ICAO는 기존의 항행장비를 위성항법 기반으로 대체해 나가고 있으며, 이의 일환으로 기존의 ILS를 이용한 이착륙 서비스를 GBAS 로 대체할 계획을 수립 하였다. GBAS는 활주로까지 항공기를 유도하는 정밀 접근 서비스와 공항 주위의 정밀위치정보 서비스를 제공하는 위성항법 보강시스템을 이용하여 ILS와 달리 한 개의 시스템으로 활주로의 수에 관계없이 요구 성능을 제공할 수 있으며 curved approach가 가능하다는 장점을 보유하고 있다. 본 논문에서는 태안비행장 비행시험을 통한 ILS접근 절차와 GBAS curved approach절차를 비교하여 비행시간 단축 및 연료 감소효과를 분석하였으며 실제 비행시험을 통하여 이를 측정 확인 하였다.

• 한국항공운항학회지
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• 제16권1호
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• pp.18-28
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• 2008

The purpose of this study is leading to prevent the major causes of commercial-aviation fatalities about controlled-flight-into-terrain(CFIT) in approach-and-landing accidents. The paper of major analysis for controlled flight into terrain(CFIT) was Guam accident, Mokpo accident and Gimhae accident in commercial transport-aircraft accidents from 1993 through 2002. CFIT occurs when an airworthy aircraft under the control of the flight crew is flown unintentionally into terrain, obstacles or water, usually with no prior awareness by the crew. This type of accident can occur during most phases of flight, but CFIT is more common during the approach-and-landing phase. Ninety-five percent of the Guam accident, Mokpo accident, and Gimhae accident where weather was known involved IMC, fog, and rain. The paper believed that prevention for CFIT accident was education and training for flying crew and upgrade for equipment such as EGPWS, and need more research for professional organizations of airlines, and accomplishing precision approaches should be a high priority.

• 한국정밀공학회지
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• 제18권12호
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• pp.137-144
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• 2001

The major movement blocks of the container are the range between the apron and the designation points on yard in container terminals. The yard tractor drived by operator takes charge of it's movement in conventional container terminals. In automated container terminal, AGV(automatic guided vehicle) takes charge of a yard tractor's role and information of navigation path are ordered from upper control system. The automated container terminal facilities must have the docking system that guides landing zinc to execute high speed travelling and precision positioning. This paper describes the new docking method with the rotating LSB(laser slit beam) generator and two pair of photo receiver. The LSB generator is installed on the fixed ground and the photo receiver is implemented on the moving vehicle such as AGV. The proposed docking system is implemented to confirm it's function and accuracy. The accuracy of measured moving position is represented in ±5mm at 1 data sampling.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.826-831
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• 2004

Recently, studies have been carried out to develop unmanned Micro Air Vehicles(MAVs) that can search and monitor inside buildings during urban warfare or rescue operations in hazardous environments. However, existing fixed-wing and rotary-wing MAVs cannot travel at extremely low or high speeds, hover in place, or change directions instantly. This has lead researches to search for other flight methods that could overcome those drawbacks. Insect flight principles and its applications to MAVs are being studied as an alternative flight method. To take flight, insects flap and rotate their wings. These wing motions allow for high maneuverability flight such as hovering, vertical take off and landing, and quick acceleration and deceleration. This paper proposes a method for designing a mechanism that reproduces hovering insect flight, the basis for all other forms of insect flight. The design of a mechanism that can reproduce the motion that causes maximum lift is proposed, the required specifications are calculated, and a method for reproducing hovering insect flight with a single motor is presented. Also, feasibility of the design was confirmed by simulation.

• 한국정밀공학회지
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• 제21권4호
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• pp.120-131
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• 2004

In this paper, we propose the method of a motion planning generation in which the movement of the 3-link leg subsystem is constrained to a slider-link and a singular posture can be easily avoided. The proposed method is the jumping control moving in vertical direction which mimics a cat's behavior. That is, it is jumping toward wall and kicking it to get a higher-place. Considering the movement from the point of constraint mechanical system, the robotic system which realizes the motion changes its configuration according to the position and it has several phases such as; ⅰ) an one-leg phase, ⅱ) in an air-phase. In other words, the system is under nonholonomic constraint due to the reservation of its momentum. Especially, in an air-phase, we will use a control method using state transformation and linearization in order to control the landing posture. Also, an iterative learning control algorithm is applied in order to improve the robustness of the control. The simulation results for jumping control will illustrate the effectiveness of the proposed control method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1341-1344
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• 2003

Studies on impact damage of composite laminate shells were fewer compared with those on impact behaviors to analyze time-load, displacement-load and impact energy - energy absorption. Up to date the studies were not enough to demonstrate suitability of their results because they were dependent on theories and numerical analyses. In particular, it is a well-known fact that there was a correlation between initial peak load and damage resistance of composite material flat plates imposed with low-speed impact, but studies on composite material shells with curvature were also very few. Actually structures such as wings or moving bodies of airplanes, motor cases and pressure containers of rockets are circular. And as low-speed impact load is imposed for optimal design of take-off and landing, and containers of airplanes, it is very important to analyze evaluation of behaviors and damaged areas. Therefore, in this paper to evaluate the impact characteristics of the CFRP laminate shell according to size of curvature quantitatively, it was to identify energy absorption and impact damage instruments according to change of impact speed.