• 한국공작기계학회논문집
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• 제13권1호
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• pp.88-93
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• 2004

In general, a fundamental structural design consideration for an automobile is the overall dynamic behavior in bending and torsion. Dynamic behavior of the automobile are mainly influenced by the structural stiffness of B.I.W.(body-in-white) and the physical property of trim components. In this paper, the modeling techniques for various trim components of middle-sized bus are presented, and the dynamic effects of the trim components on the vibration characteristics of the bus are investigated. The $1^{st}$ torsional frequency is decreased by attaching windshield and backlite to the B.I.W., but the $1^{st}$ vertical bending frequency and the $1^{st}$ lateral bending frequency are increased. The natural frequencies of the bus are decreased by attaching doors and windows. And also, the natural frequencies of the bus are large decreased by attaching seats, instrument panel etc. The study shows that the dynamic characteristics of the bus can be effectively predicted in the initial design stage.

• 한국항해항만학회지
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• 제37권2호
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• pp.137-142
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• 2013

The displacement Deep-V catamaran concept was developed in Newcastle University(UNEW) through development of the systematic Deep-V catamaran series. One of the most important Deep-V catamaran launched to date is Newcastle University's own multi-purpose research vessel, The Princess Royal. The vessel was launched in 2011 and enhanced the Deep-V catamaran concept further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. It was however identified that the vessel has substantial amount of dynamic trim that limited the visibility of the captain. The dynamic trim also increased the wave-making resistance thereby preventing the vessel from attaining its maximum speed in certain sea states. This paper therefore presents the application of devices such as Trim Tabs, Interceptors, Transom Wedges and Integrated Transom Wedges-Tabs to control the dynamic trim and improvement of fuel efficiency of the vessel. All of these energy saving devices were fitted into a model for tests in Newcastle University's Towing Tank. Model test verification confirmed that the optimum appendage was the interceptors, they produced a 5% power saving and 1.2 degree trim reduction at 15 knots, and investigations of full scale trials will be scheduled with and without application of device to compare the improvement of performance.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.153-158
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• 1992

The purpose of this paper is to calculate the dynamic derivatives of single rotor Helicopter in forward flight. From trim condition, the equation of motion is derived, and we can calculate the dynamic dervatives. The results were compared with flight test data. The phase angle and stick displacement are obtained and compared at the trim condition.

• Coupled systems mechanics
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• 제7권2호
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• pp.163-176
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• 2018

The ship hydrodynamics in static and dynamic states were investigated using 3-dimensional numerical simulations. The static case simulated a fixed ship, while the dynamic case considered a ship with free sinkage and trim using the mesh morphing technique. High speed was found to increase the wave elevation around the ship. Compared with the static case, the dynamic case seemed to generate higher waves near the bow and after the stern. The frictional resistance was found be to more dominant. However, the pressure resistance became gradually important with the increase of the ship speed. The trim and sinkage were also analyzed to characterize the ship hydrodynamics in the dynamic state.

• 대한조선학회논문집
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• 제54권2호
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• pp.96-101
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• 2017

Amphibious assault vehicles have been used in the Marine Corps. In recent years, their ability to move faster is becoming one of the most important considerations. At high speeds, the vehicle tends to sink at the stern and sometimes the opposite occurs. Such dynamic trim plays a significant role in determining the vehicle's hydrodynamic performance. Furthermore, an excessive trim by stern upsets the viewing angle. We have thus considered a stern hydrofoil to reduce the dynamic trim of the amphibious assault vehicle. Laboratory-scale resistance tests were conducted in a towing tank at the Seoul National University (SNU). This study aims to make a preliminary assessment of the hydrodynamic performance of the vehicle with the stern hydrofoil and to investigate permissible speed range of the vehicle. The experimental results show that the stern hydrofoil can successfully achieve a reduction of both the dynamic trim and the hydrodynamic resistance at running speeds above 20 km/h.

• International Journal of Aeronautical and Space Sciences
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• 제12권3호
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• pp.241-251
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• 2011

Most large commercial aircrafts and high performance military aircrafts use fly-by-wire (FBW) or fly-by-light systems to improve their controllability, comfort, and safety. A flight envelope protection technique is used with flight control systems utilizing the FBW technique. Such flight envelope protection systems prevent these aircraft from exceeding the structural/aerodynamic limits and control their surface limits. This is accomplished by predicting the values of the future state variables and adaptively compensating the control action. In this study, the conventional dynamic trim algorithm of the flight envelope protection is modified to increase the method accuracy and to handle cases with multiple variables. Numerical simulation is also performed to verify the performance of the proposed method.

• 대한조선학회논문집
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• 제50권2호
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• pp.88-94
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• 2013

The primary objective of the current work is to obviously analyze regarding effects of trim conditions of a ship on resistance performance using model test and CFD. Model tests at a towing tank are conducted to investigate resistance for trim conditions at the given same displacement. Measured resistance shows small but distinct differences according to trim conditions. However, these differences are difficult to be clarified by measured physical quantities and wave pattern analysis from model tests. CFD is employed for the assessment of resistance performance according to trim conditions. The flow computation is conducted considering free surface and dynamic trim using a commercial CFD code (STAR-CCM+). The initiative of the present work is to systematically demonstrate pressure resistance acting on each region of divided finite zones of ship surface along the length and draught direction of surface when pressure distribution on the ship is interpreted. Also, a standard to assess the pressure resistance applied on the divided regions of a ship is established.

• 한국항공우주학회지
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• 제38권4호
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• pp.327-334
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• 2010

최근 개발된 항공기는 대부분 디지털 Fly-By-Wire(FBW) 혹은 광신호를 사용하는 Fly-By-Light(FBL) 시스템을 사용하고 있다. 이러한 시스템들은 조종사의 직접 조종으로는 불가능하거나 어려운 복잡한 임무의 수행, 비행범위 확장, 신뢰성 향상 등의 장점을 가지고 있다. FBW 기술을 적용한 비행제어기술이 발전됨에 따라 운항 시 안정성 확보 및 보다 효율적인 임무수행을 위해 비행영역(Flight Envelope) 보호의 개념이 항공기 설계에 있어 중요한 문제로 부각되고 있다. 본 논문에서는 dynamic trim 알고리즘, peak response estimation, 제어이득 스케쥴링 등의 방법을 이용해서 항공기의 비행영역 보호를 수행하고, 각 방법의 성능을 비교하여 최적의 제어기를 설계하는 연구를 수행하였다.

• 한국항공운항학회지
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• 제21권4호
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• pp.34-40
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• 2013

Attitude command response type required for enhanced handling qualities of helicopter can be implemented by mechanical automatic flight control system with SAS actuators which have limited authorities. However, the early saturation of SAS actuator hinders the helicopter from following the attitude command for large stick command. Auto-trim controller can delay SAS actuator's saturation by utilizing trim actuators and allows the attitude command response type for larger stick command. This paper describes the control law for limited authority system of helicopter with auto-trim. Limited authority system is applied to BO-105 linear dynamic model and simulation is performed along with handling quality analysis.

• 한국해양공학회지
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• 제29권6호
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• pp.411-417
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• 2015

The shipping and shipbuilding industries have had business difficulties since the implementation of regulations on the CO₂ emissions from ships by IMO and the occurrence of the global financial crisis in 2008. Under this global recession, most shipping firms have started to operate their fleets at slow steaming rates with the goal of improving the profit ratio per transported unit. This study analyzed the resistance performance of a 6,800 TEU container ship corresponding to its trim variation with slow steaming, compared with that at its original design speed. Two different grid systems were used for the numerical calculation, one that considered the free surface allowing the capture of the dynamic trim and one that did not. This made it possible to clearly classify each resistance component to provide useful information to hull-form designers. In addition, a form factor assumption method using CFD was used for a reasonable effective power prediction in compliance with the 1978 ITTC performance prediction method. It was found that the total resistance of a 6,800 TEU container ship was reduced by 2.6% in the case of a 1-m trim at the bow at 18 kn.