• 드라이브 ㆍ 컨트롤
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• 제13권4호
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• pp.23-30
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• 2016

This paper presents a control-oriented dynamical model of a towing rope system with variable-length. In this system, a winch driven by a motor's torque uses the towing rope to pull a cart. In general, it is a difficult and complicated process to obtain an accurate mathematical model for this system. In particular, if the rope length is varied by operating the winch, the varying rope dynamics needs to be considered, and the key physical parameters need to be re-identified... However, real time parameter identification requires long computation time for the control scheme, and hence undesirable control performance. Therefore, in this article, the rope is modeled as a straight massless segment, with the mass of rope being considered partly with that of the cart, and partly as halfway to the winch. In addition, the changing spring constant and damping constant of the towing rope are accounted for as part of the dynamics of the winch. Finally, a reduced-order observer-based servomechanism controller is designed for the system, and the performance is evaluated by computer simulation.

• 동력기계공학회지
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• 제20권2호
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• pp.58-65
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• 2016

Lately, tugboats are widely used to maneuver vessels by pushing or towing them where tugboats use rope. In order to correctly control the motion of tugboat and towed vessel, the dynamics of the towline would be well identified. In real application environment, the towing rope length changes and the towing load is not constant due to the various sizes of towed vessel. And there are many ropes made by many types of materials. It means that it is not easy to obtain rope dynamics, such that it is too difficult to satisfy the given control purpose by designing control system. Thus real time identification or adaptive control system design method may be a solution. However it is necessary to secure sufficient information about rope dynamics to obtain desirable control performance. In this paper, the authors try to have several rope dynamic models by changing the rope length to consider real application conditions. Among them, a representative model is selected and the others are considered as uncertain models which are considered in control system design. The authors design a robust control to cope with strong uncertain and nonlinear property included in the real plant. The designed control system based on robust control framework is evaluated by simulation.

• 수산해양기술연구
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• 제44권2호
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• pp.120-128
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• 2008

Estimation of the gear shape and cross section of sweep at mouth of a bottom trawl net was described and applied to the field experiments obtained with the Scanmar system. The shape of the trawl net from wingend to the beginning of codend was assumed to be part of an elliptic cone of which the cross section was ellipse, and that of the float rope be of form $y_f=a_fx^{bf}$. In case of a bottom trawl with warp 180m long, the radius of ellipse, the cross section of sweep at mouth, the eccentricity of the ellipse, the inclination angle of float rope and the contribution of the side panel to net height were estimated in accordance with towing speed. The horizontal radius of the upper ellipse increased with increasing towing speed, the eccentricity of it became slightly bigger as increasing the towing speed which meant the shape of it being flat. And the inclination angle of the float rope was about between 7 and 12 degrees in case of the above bottom trawl.

• 수산해양기술연구
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• 제34권3호
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• pp.294-301
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• 1998

Towing performance of a midwater trawl system was examined aboard the training ship KAYA(2900ps) at the East Sea using the midwater trawl gear that had been designed and manufactured in accordance with the vessel. In this experiment, the trawl system data, the towing speed, the length and tension of the warp, net mouth height, and the depth of otter boards and net were measured and analyzed. The results are as follows: 1. In case of heaving in the warp with constant towing speed, the tension was suddenly increased and then again was reduced and after returned to the original steady state tension. At this time, net height was reduced a bit by ascension of ground rope, but returned to it’s original value. In the case where the warp was paid out, the tension was suddenly decreased and after increased and then returned to the tension of the original state, and the net height was greatly increased instantly by the sinking of the ground rope and then returned to the steady state 2. In the case of increased towing speed mm constant warp length, the tension was increased, and reducing the net height, the gear depth was decreased. On the other hand, in the case where towing speed was reduced, the tension was reduced and the gear depth and net height was increased. 3. Otter boards show a swing motion in the scope of 5~ 10m continuously. Otter boards responded to the state change of the trawl system at first, and then the motion of the net appeared. 4. The depth of net center was about 20m deeper than that of the otter boards, it shows about 0.4 times the warp length at the 4knots towing speed.

• 한국수산과학회지
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• 제34권3호
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• pp.238-244
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• 2001

중층트롤 어구의 유체저항을 구하거나 전개판의 간격을 구하는 것은 어구설계나 어로작업에 유용하다. 본 논문에서는 끌줄에 관해 신장을 포함하여 간이해석적 (semi-analytic)으로 푼 3차원해석을 이용하여 중층트롤 어구의 끌줄에 적용시키고, 줄의 형상에 대해 기존의 직선이라는 가정은 실제로 이루는 곡선과는 차이가 있기에, 여기서는 줄의 형상을 곡선 형태로 도입하였는데, 날개그물 끝에서 후릿줄, 뜸$\cdot$발줄 및 (자루그물의) 힘줄에 미치는 세 힘의 합력을 역학적으로 고려하여 어구의 유체저항을 구한 방법을 나타낸 것으로서. 이때 전개판 (OB) 뒤쪽의 후릿줄 (hand rope), bridle 및 뜸 (발)줄의 형상을 곡선인 $y_{r}=Ax_{r}^{B}$의 형태 (B=2이면 포물선 (parabola)임)로 가정하였다. 기존의 중층트롤의 실험자료에서 끌줄의 길이가 100m인 경우에 예망속도의 변화에 따른 여러가지 측정값을 이용하여 트롤어구의 유체저항을 구하는 새로운 방법을 제시하였는데, 10매로 구성된 망지의 유체저항 ($R_{n}(kg)$)과 유속 (V)과의 관계는$1.34 범위에서 $R_{n}=1204.6\;V_{(m/s)}^{1.99}$ 관계가 있었다. 여기에서 제안한 방법을 이용하면 트롤어구의 그물만의 유체저항을 직접적으로 구할 수 있다.

• 한국수산과학회지
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• 제41권2호
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• pp.140-149
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• 2008

This study evaluated the efficiency of an oil fence and spreading devices for one vessel in a towing tank. A series of model experiments and numerical calculations were conducted using an existing oil fence for two vessels and a new method for one vessel. Models of the oil fence and spreading devices were constructed on $1/20^{th}$ scale from waterproofed nylon fabric and canvas. The tensions acting on the model of the oil fences and the horizontal distance between the spreading devices were calculated numerically while the oil fences were being towed. The results were extremely close to the results of the model experiments. The ratio of the opening width to the total length of the oil fence, which shows the efficiency of the oil fence for one vessel, was 49.7% in 0.4 m/sec. Therefore, the proposed oil fence system should be very useful for oil containment at sea. As the opening width of the oil fence is not proportional to the length of the towing rope, it may be reasonable to maintain the towing rope at approximately 100 m. Furthermore, a reasonable towing speed, when operating the oil fence for one vessel equipped with spreading devices, was within 0.4 m/sec.

• 수산해양기술연구
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• 제43권4호
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• pp.347-354
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• 2007

This paper describes on the real-time monitoring of net setting and hauling process for fishing operations of Danish seine vessels in the southern waters of Korea as an application of a PC based ECDIS system. Tracking of fishing process was performed for the large scale Danish seine vessel of G/T 90 and 350 PS class using the fishing gear which the length of net, ground rope, head rope and sweep line including warp in both sides were 86m, 104m, 118m and 3,200m, respectively. Tracking information for net setting and hauling process was continuously recorded for 23 fishing operations performed on November and December, 2003. All measurement data, such as trawl position, heading, towing course and past track which was individually time stamped during data acquisition, was processed in real time on the ECDIS and displayed simultaneously on the ENC chart. The results indicated that after the separation of a marker buoy from Danish seiner, the averaged running speed of vessel and the averaged setting period while shooting the seine on the course of diamond shape to surround the fish school in the 23 fishing operations were 8.3 knots and 13.1 minutes, respectively. And with the maker buoy taken on board, the averaged running speed of vessel and the averaged towing period while closing the seine on the straight route was 1.0 knots and 47.0 minutes, respectively. After the closing stage of hand rope, the hand rope was towed by the averaged speed of 2.2 knots during the 13.0 minutes. The average area for route of diamond shape swept by sweep lines of the seine in 23 fishing grounds was $709,951.6m^2$. Further investigation is also planed to provide more quantitative tracking information and to achieve more effective surveillance and control of Danish seine vessels in EEZ fishing grounds.

• 수산해양기술연구
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• 제38권3호
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• pp.209-216
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• 2002

본 연구에서는 중층트롤의 해상실험에서 Scanmar시스템으로 여러가지 요소를 측정한 자료에, 줄에관해 신장을 포함하여 간이 해석적(semi-analytic)으로 푼 3차원 해석을 중층트롤 어구시스템의 끌줄에 적용시키고, 전개판 뒤쪽의 줄들의 형상을 임의의 지수함수(Y$_{r}$ = $A\chi$$_{r}$ $^{B}$ ) 곡선으로 대응시켜, 중층트롤의 어구(날개 및 자루그물)의 형상을 타원추대의 일부분으로서 (equation omitted)형태로 가정하여 구하는 새로운 방법을 나타냈었다. 실제의 전개판은 예망중 진동한다고 알려져 있으며, 어느 각도 내에서는 안정성이 있기 때문에 양.항력계수는 기존의 종만곡 V형 전개판의 모형실험으로부터 영각이 15$^{\circ}$ 부터 최대값인 22$^{\circ}$ 까지의 값을 평균하여 사용하였다. 본 연구에서는 끌줄의 길이가 300m인 경우에 대한 결과를 나타내었는데, 망입구의 형상(b$_{e}$ /a/seb e/)은 예망속도가 빨라점에 따라 수직으로 긴 타원형에서 수평으로 커져가는 타원형이 됨을 알 수 있다 이때, 망고(즉 옆망이 망고 형성에 기여한 높이와 삼각망 및 천장망이 기여한 높이)는 낮아졌는데, 옆망이 낮아지는 것보다 천장망의 높이가 더 작아짐을 알 수 있다. 뜸줄이 수평과 이룬 경사각(a)은 이 예의 경우에서 약 9$^{\circ}$~11$^{\circ}$ 사이였으며, 예망속도가 빨라질수록 경사각이 작아졌다.

• 수산해양기술연구
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• 제60권3호
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• pp.207-216
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• 2024

This study conducted a marine experiment to improve the fishing system using miniaturized nets for anchovy boat seine to reduce the fleet size. As a result, the miniaturized net for anchovy boat seine properly opened the entrance of the bag net using the buoyancy of the flotation for position indication and the setting force of the ground rope without operating a separate fish detecting boat by attaching a large flotation at the entrances of the inside wing net and the bag net. This also enabled an operation type where the entrance of the bag net is confirmed using a flotation for position indication from a netting boat. The time and the number of people used for net casting and net hauling in the marine experiment were average of five minutes and 25-30 minutes, respectively, and 23-30 people for the existent net, while for the miniaturized large-scale net were average of three minutes and 23-25 minutes, respectively, and 19-25 people. This indicates that the operation time was shortened, the number of fish detecting boats was reduced by one boat, and the number of people for fishing work was decreased by four or five people due to the improvement of fishing operation system according to the reduction of fishing net size. As a result of measuring the shaft horsepower during net towing, the maximum net towing horsepower was 250 HP in comparison to the maximum RPM of the engine (1,200 RPM), indicating that the legal horsepower of 250 HP is enough to conduct net towing and the competitiveness of fishing using the net for anchovy boat seine is ensured through operation cost reduction.

• 수산해양기술연구
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• 제51권1호
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• pp.26-34
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• 2015

The angle of attack of a cambered otter board in a bottom trawl was estimated using a three-dimensional semi-analytic treatment of a towing cable (warp) system that was applied to the field experiments of a bottom trawl obtained by the Scanmar system. The equilibrium condition of the horizontal component and vertical component of forces was used to the three forces acting on the otter board in the horizontal plane. Those forces were the force on the warp at the bracket, hydrodynamic lift and drag forces on the otter board and the force on the hand rope attached just behind the otter board. Also the equilibrium of moment about the front edge of the otter board was used to find out the angle of attack of the cambered otter board. When the warp length was 120m and 180m long and the towing speed was between 1.23 and 1.90 m/s, the estimated angle of attack of the cambered otter board was ranged between $26.1^{\circ}$ and $29.6^{\circ}$, respectively, though the maximum lift force was at the angle of attack $22.6^{\circ}$. The angle of attack of the otter board was tended to increase weakly with the longer length of warp (180 m) at the same towing speed in the experiment.