• Ocean Systems Engineering
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• 제1권4호
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• pp.297-315
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• 2011

New applications of streamlined Autonomous Underwater Vehicles require an AUV capable of completing missions with both high-speed straight-line runs and slow maneuvers or station keeping tasks. At low, or zero, forward speeds, the AUV's control surfaces become ineffective. To improve an AUV's low speed maneuverability, while maintaining a low drag profile, through-body tunnel thrusters have become a popular addition to modern AUV systems. The effect of forward vehicle motion and sideslip on these types of thrusters is not well understood. In order to characterize these effects and to adapt existing tunnel thruster models to include them, an experimental system was constructed. This system includes a transverse tunnel thruster mounted in a streamlined AUV. A 6-axis load cell mounted internally was used to measure the thrust directly. The AUV was mounted in Memorial University of Newfoundland's tow tank, and several tests were run to characterize the effect of vehicle motion on the transient and steady state thruster performance. Finally, a thruster model was modified to include these effects.

• 한국해양공학회지
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• 제24권2호
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• pp.10-17
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• 2010

Conventionally, because it is difficult to control a ship in shallow water and because attempting to do so creates unwanted environmental effects, maneuvering ships in the harbor area for berthing is usually done with the assistance of tugboats. In this paper, we propose a new method for berthing ships automatically by using bow and stern thrusters. Specifically, a steering motion model of a ship is considered, and parameters in the equation are evaluated by the system identification technique. An optimal controller based on observations was designed from the linearization of the non-linear ship motion in the horizontal plane. It is used to reduce the uncertainty about the ship's dynamics and reduce measurement requirements. The performance of the controller was also analyzed for its robustness relative to avoiding disturbing the environment due to winds, currents, and wave-drift forces. Experiments were conducted to estimate the potential for identifying result and the design of the controller. Specifically, in this paper, the system modeling and tracking control approach are discussed based on a two-degree-of-freedom (2DOF) servo-system design.

• 해양환경안전학회지
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• 제25권6호
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• pp.757-764
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• 2019

수중에서 빠른 속도로 운동하는 물체 주변에서 감압이 발생하며, 이로 인해 공동 핵이 팽창함으로써 캐비테이션이 발생한다. 캐비테이션이 발생하게 되면 소음 및 진동이 증가하며, 추진기의 경우 추진 성능이 저해되는 악영향을 초래하기 때문에 이에 대한 예측이 필요하다. 본 연구에서는, 캐비테이션 발생으로 인한 공동소음의 해석절차를 정립하고, 타원형 날개에 적용하였다. 먼저 전산유체역학해석을 수행하여, 날개 형상 주위 유동장 정보를 도출하였다. 공동 핵 밀도 함수를 활용하여, 핵의 초기 반경 별로 개수를 계산하였고 이들을 압력 강하가 큰 날개 끝 전류에 랜덤하게 배치하였다. 이후 공동소음 해석을 위해 각각의 핵에 대하여 Lagrangian 관점에서 버블 다이나믹스를 활용하였고, 계산된 공동의 거동으로부터 소음해석을 수행하였다. 공동소음은 광대역 소음의 특성을 가지는 것을 확인하였으며, 최종적으로 선박해양플랜트연구소(KRISO)의 대형캐비테이션터널(LCT)에서 수행된 실험 계측결과와의 비교를 통해 검증을 수행하였다.