• Smart Structures and Systems
• /
• v.2 no.1
• /
• pp.61-80
• /
• 2006

The concept of structural vibration control is to absorb vibration energy of the structure by introducing auxiliary devices. Various types of structural vibration control theories and devices have been recently developed and introduced into mechanical systems. One of such devices is damper employing controllable fluids such as ElectroRheological (ER) or MagnetoRheological (MR) fluids. MagnetoRheological (MR) materials are suspensions of fine magnetizable ferromagnetic particles in a non-magnetic medium exhibiting controllable rheological behaviour in the presence of an applied magnetic field. This paper presents the modelling of an MRfluid damper. The damper model is developed based on Newtonian shear flow and Bingham plastic shear flow models. The geometric parameters are varied to get the optimised damper characteristics. The numerical analysis is carried out to estimate the damping coefficient and damping force. The analytical results are compared with the experimental results. The results confirm that MR damper is one of the most promising new semi-active devices for structural vibration control.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.5
• /
• pp.769-774
• /
• 2010

It happened fractures on special bolt which supported main landing gear actuator up-lock rod of aircraft. Cracks were initiated mainly from the center hole and the external thread of the special bolt. To find out failure root causes, metallographic, fractographic analyses as well as test work were carried out. From the fractographic study by SEM work, fracture occurred by a brittle intergranular type failure. The fracture could be occurred primarily by solid-metal-induced embrittlement due to cadmium embrittler penetrated into the flaw existed after machining work for center hole and thread on the bolt during baking treatment processing to eliminate hydrogen. For its successful application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and make no more drilled center hole on the bolt to prevent same failure.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.162.3-162
• /
• 2001

The essence of ABS(Anti-skid Brake System) control is to continuously adjust brake pressure to maintain optimum brake torque. This optimum level should balance tire and runway friction its peak value, yielding maximum braking deceleration. It influences not only the deceleration and the taxing distance of an aircraft, but also the strength and the fatigue life of the landing gear. In this paper, an ABS control algorithm is developed with a dynamics model of 5-DOFD(Degree of Freedom). The algorithm is verified by simulations and the simulation results are presented. The dynamics model is simulated by the computer.

• International Journal of Aeronautical and Space Sciences
• /
• v.18 no.4
• /
• pp.623-640
• /
• 2017

The full nonlinear equations of an unmanned aerial vehicle ground taxiing mathematical dynamic model are built based on a type of unmanned aerial vehicle data in LMS Virtual.Lab Motion. The flexible landing gear model is considered to make the aircraft ground motion more accurate. The electric braking control system is established in MATLAB/Simulink and the experiment of it verifies that the electric braking model with the pressure sensor is fitted well with the actual braking mechanism and it ensures the braking response speediness. The direction rectification control law combining the differential brake and the rudder with 30% anti-skid brake is built to improve the directional stability. Two other rectifying control laws are demonstrated to compare with the designed control law to verify that the designed control is of high directional stability and high braking efficiency. The lateral displacement increases by 445.45% with poor rectification performance under the only rudder rectifying control relative to the designed control law. The braking distance rises by 36m and the braking frequency increases by 85.71% under the control law without anti-skid brake. Different landing conditions are simulated to verify the good robustness of the designed rectifying control.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.1
• /
• pp.26-34
• /
• 2019

In this paper, a coarse lunar soil model is developed using discrete element method and its computed physical properties are compared with those of the actual lunar soil for its validation. The surface of the actual moon consists of numerous craters and rocks of various sizes, and it is covered with fine dry soil which seriously affects the landing stability of the lunar lander. Therefore, in consideration of the environment of the lunar regolith, the lunar soil is realized using discrete element method. To validate the coarse model of lunar soil, the simulations of the indentation test and the direct shear test are performed to check the physical properties(indentation depth, cohesion stress, internal friction angle). To examine the performance of the proposed model, the drop simulation of finite element model of single-leg landing gear is performed on proposed soil models with different particle diameters. The impact load delivered to the strut of the lander is compared to test results.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.12
• /
• pp.857-866
• /
• 2022

Fixed-wing UAVs have long endurance and range capabilities compared to other aerial platforms. These advantages led fixed-wing UAVs to become a popular platform for reconnaissance missions in the military. In this research, we modeled fixed-wing UAVs, including the landing gear model and developed a guidance and control system for flight control computers to construct a HILS environment. We also developed an autopilot system that includes automated take-off, cruise, and landing control for UAVs. We also retrived the Aerodynamic coefficients an UAV using Datcom and AVL software and used them for 6 degrees of freedom modeling. The Flight control computer calculates guidance commands using the Carrot chasing guidance law after distinguishing the condition of the UAV based on 16 pre-defined flight modes and calculates control inputs using Nonlinear Dynamic Inversion (NDI) control scheme. We used RTNngine to integrate the Simulink model and flight control computer for HILS environment formulation.

• Proceedings of the KAIS Fall Conference
• /
• 2011.12b
• /
• pp.503-506
• /
• 2011

항공기 착륙장치 피로 수명평가에는 안전 수명방법이 사용된다. 안전 수명방법은 항공기 전 수명기간을 모사하는 피로하중 스펙트럼 조건에서 균열 또는 유해한 변형과 같은 구조적 결함이 발생하지 않도록 설계/입증하는 것을 말한다. 설계 단계에서는 해석적 방법을 통해 착륙 및 지상운용하중을 구하고, 이를 착륙장치 피로해석에 적용하여 피로수명을 확인한다. 착륙장치는 수명 기간 중 일반적으로 High Cycle 피로를 겪게 되므로, 피로해석 시 응력 기반의 접근 방법이 적용된다. 시험평가 단계에서는 일반적으로 4배의 운용수명에 해당하는 피로하중 스펙트럼에 대해 시험을 수행하여, 착륙장치의 안전 수명을 최종 입증하게 된다. 이와 같이 항공기 착륙장치 피로 수명평가를 위해서는 착륙 및 지상운용 하중해석에서부터 피로해석, 피로시험에 이르기까지 전 과정이 유기적으로 결합되어 이루어져야 한다. 본 연구에서는 항공기 착륙장치 피로시험에 필요한 세부과정과 관련 기술을 실제 적용 사례와 함께 기술하였다.

• Journal of Mechanical Science and Technology
• /
• v.17 no.5
• /
• pp.776-783
• /
• 2003

A low speed wind tunnel test was conducted for full-scale model of an unmanned aerial vehicle (UAV) in Korea Aerospace Research Institute (KARI) Low Speed Wind Tunnel(LSWT). The purpose of the presented paper is to illustrate the general aerodynamic and performance characteristics of the UAV that was designed and fabricated in KARI. Since the testing conditions were represented minor portions of the load-range of the external balance system, the repeatability tests were performed at various model configurations to confirm the reliability of measurements. Variations of drag-polar by adding model components such as tails, landing gear and test boom are shown, and longitudinal and lateral aerodynamic characteristics after changing control surfaces such as aileron, flap, elevator and rudder are also presented. To explore aerodynamic characteristics of an UAV with model components build-up and control surface deflections, lift curve slope, pitching moment variation with lift coefficients and drag-polar are examined. The discussed results might be useful to understand the general aerodynamic characteristics and drag pattern for the given UAV configuration.

• Economic and Environmental Geology
• /
• v.49 no.6
• /
• pp.479-490
• /
• 2016

Seabed drilling system has recently been used to drill seafloor mineral resources. This case report highlights the procedure and result of sea-trial of seabed drilling system at off-shore of Japan on March, 2016 as well as briefs an international-technical trend of seabed drilling system. In case of having less than 100 m drill depth, seabed drilling system is favorable for seafloor mineral deposits which are mostly distributed within a narrow district and situated between 1000~3000 m water depth, compared with vessel-mounted drilling system. The system is featured by the remotely-operated drill gear, which has top drives, drill strings and mud system on it. The core samples are generally recovered to ship with seabed driller after a dive. In this sea-trail, recovery rate of core samples averagely shows about 55% and the recovered rocks mostly correspond to fresh and/or weak-altered basalt. In case of drilling hydrothermal ore deposit, the recovery rate would be lower than 55% because of the fragile nature of ores. Alternatively it is used to collect cutting chips through riser or bins in order to increase the recovery rates. Recently a reverse circulation method is taken considered to acquire the better cutting-chips. Three-leg type outrigger system and four-leg type leveling system are the competing landing-instruments of seabed drill system. However the landing efficiency using these gears has to be further monitored due to lack of case reports.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.48 no.4
• /
• pp.322-336
• /
• 2012

To study the catching efficiency of biodegradable trammel net for swimming crab (Portunus trituberculatus), three types (biodegradable, monofilament and multifilament) of trammel nets were used in the field test, and the tests were carried out 16 times with two different mesh sizes (105mm and 160mm) in the Yeonpyeong fishing ground of Korea, 2009~2011. The catching efficiency of three type nets was analyzed by catch in number, catch in weight and average weight per individual of small and large size swimming crab by net types and mesh sizes. Statistical T-test was also carried out to verify the efficiency between the three types of nets. The results are as follows. The catch in number of swimming crab was 24,667 and formed about 81.0% of total catch. Of all swimming crab catch, small swimming crabs with less than 64mm in carapace length which is a prohibited landing size by law formed 48.1%, larger swimming crabs with more than 64mm in carapace length which is a landing size formed 51.9%. In 105mm mesh size trammel net test, the catch share in number of small size swimming crab by biodegradable trammel net was 47.5% in comparison with multifilament trammel net and 74.2% in comparison with monofilament trammel net, so biodegradable trammel net has more protective effects on small size swimming crab than other types of trammel nets. The protective effects for small size swimming crab by biodegradable trammel net was 25.8~52.5% in comparison with other types of trammel nets. The catch share in weight of large size swimming crab by biodegradable trammel net was 98.3% in comparison with multifilament trammel net and 92.3% in comparison with monofilament trammel net, so biodegradable trammel net has a similar catch efficiency to multifilament trammel net. The results of 160mm mesh size trammel net test have shown similar results of 105mm mesh size trammel net test. This study shows that biodegradable trammel net is a more useful fishing gear than multifilament and monofilament trammel net because biodegradable trammel net has lower catch rate than other types of nets in small size swimming crab and similar catch rate than multifilament trammel net which is a well used net by fishermen.