The lack of power source capacity is one of the most fatal problems for the AUV spotlighted as a means of underwater survey and observation of the next generation, to be attacked for its practical use. To be free from such a problem, some long-term-cruising-AUVs employ with a large capacity power source like a closed cycle diesel engine or a fuel cell. On the other hand, if underwater recharging system for conventional batteries is developed, that will help us make the AUVs more practical without increasing its size, weight and cost. And such a new method of the AUV can be expected that the AUV is operated in combination with underwater bases or large submersibles. Now, we have carried out to develop such an AUV, called“MARINEBIRD”, that is capable of docking in an underwater station and recharging the battery. This kind of technologies have already been underwatertested in the U.S.A. and European countries, but our newly developed AUV is based on our original mechanism for docking, different from such ones. The MARINEBIRD succeeded the docking test in the dock trial, and demonstrated the excellence of its autonomous docking capability. The MARINEBIRD has the big advantage of charging batteries and receiving data at the underwater base without recovery by the surface support ship or such purposes as required in combination with a larger submersible, that will contribute to increase efficiency in underwater survey.
In this paper, a motion planning method for underwater manipulator is considered. Generally, there are some obstacles such as rock, submarine ridges and so on in the work area of underwater manipulators. The manipulators have to work carefully with avoiding these obstacles. Therefore, the aim of this paper is to propose a method that generates the secure moving path of the tip of the manipulator and the manipulator's posture that avoid obstacles in the work area. The work area considered this paper is divided into some cubes. The position of the obstacles is defined as the position of the cube. The path of the tip of the manipulator is also derived as the set of positions of the cubes. In order to generate the path, we use the Genetic Algorithm (GA) that gives quasi-optimal path. On the other hand, the posture of the manipulator is derived by inverse kinematics after generating the path of the tip of the manipulator. Since the manipulator considered this paper is for underwater robots, the effect of the drag force is also considered when the posture of the manipulator is decided. Our proposed motion planning method that combines the path and the posture plan-ning is repeated every sampling time. The effectiveness of our method is shown by several experiments using a 7 degree-of-freedom manipulator.
Energy and air pollution have become important issues in recent years. BDF (Bio Diesel Fuel) such as esterified rapeseed oil or soybean oil, on which a lot of research was accomplished, has attracted attention as one of the new energy sources that replaces fossil fuel. Reported researches approved that in comparison with diesel oil, BDF contributes to reducing of particulate matter emission, which is harmful to the human health. Our research objective is to recycle BDF as marine fuel oil. The test was achieved as an application of BDF-mixed Diesel oil to a ship engine (the continuous rated output: 1000PS/2100rpm×2) and reducing of particulate matter emission.
The purpose of this study is to build up the visualization system using CCD camera at low cost in the high pressure vessel which can pressurize water up to 40MPa. The specification of the vessel is 1.988 m height, 0.635 m diameter and 0.6m3volume. A cheap CCD camera installed in a small container is fixed near a table-tennis ball and a cup of styrene foam in the vessel. Our visualization system succeeded to observing and recording the scenes of breaking of the ball at around 1 MPa and shrinking process of the cup up to 27 MPa.
The Oshima Maru is a 226-gross-ton training ship equipped with one 1300 ps, 370r.p.m, diesel engine. In this ship, various structural countermeasures against vibration and noise were taken. However, unpleasant low-frequency sound from the engine room persisted in the mess hall where crews take their breaks. The main engine room, located on the lower deck, is adjacent to and partially below the mess hall. Conventional solutions for that noise are also subject to considerable structurally variation. Active noise control, ANC, is capable of providing a universal solution. In order to apply ANC, we investigated the sound field in the mess hall using complex intensity analyses and multiple coherence function. From these results, we selected the reference signals suitable for ANC and considered constructing the active control system using multichannel filtered-x LMS algorithm of the ship interior noise.
To improve combustion and exhaust gas emissions in high speed diesel engines operating with high viscosity or low grade fuels, the effects of blending low boiling point components, including paraffins and oxygenates, into the fuel were investigated. The results indicated that a significant and simultaneous improvement of thermal efficiency, smoke and CO was obtained from the high viscosity fuel by blending with a low boiling point component. The improvement increased both with decreases in the blending component boiling point and with increases in the quantity of the blending component. Also, the improvement was obtained apparently at retarded fuel injection timings, resulting in a considerable improvement of the trade-off relation between NOx and thermal efficiency or smoke. The cause for the improvement of thermal efficiency included an increase in the degree of constant volume combustion and combustion efficiency resulting from enhanced evaporation of the high viscosity fuel spray droplets due to blending with a low boiling point component.
In marine air pollution control, only SCR (Selective Catalytic Reduction) is estimated at a variable method to control NOx, but on the other hand, seawater scrubber applying the basic characteristic that is naturally alkaline (pH typically around 8.1) is viewed as an economical SOx removal system at present. Especially, seawater scrubber would not be necessary to follow any of the various land based flue gas desulfurization methods, i.e. wet, dry or alkali scrubbing. However, these methods are not readily adaptable to marine conditions due to the quantities of consumables required, i.e. lime or limestone, the means of operation and the commercial availability. This research is undertaken to develop a new method as the main target of eliminating all exhaust emissions, particularly onboard, because the vessel can easily use seawater and be apt to apply a wet scrubber system. First, with using only seawater, the SOx are absorbed by relatively high solubility compared to other components of exhaust pollutants, and PM (Particulate Matter) is removed through direct contact with sprayed seawater droplets. Besides, the electrolyzed alkaline seawater by electrolysis, which contains mainly NaOH together with alkali metal ions (i.e. Na+, K+, Mg2+, Ca2+), is used as the absorption medium of NOx and CO2. Especially, to increase NOx absorption rate into the alkaline seawater, nitric monoxide (NO) is adequately oxidized to nitric dioxide (NO2) in the acidic seawater, which means both volume fractions are adjusted to identical proportion. The results found that the SOx removal could be achieved nearly perfectly and also led to a sufficient reduction of PM without regard to the pH values of reaction seawater. However, it may be also necessary to do a trial for NOx and CO2absorption with using the electrolyzed seawater.