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Yu Fukuda, Satoru Yamaguchi, Yuta Shindo, Investigation of the motion control performance and hydrodynamic of a multi-winged towed vehicle with intentional instability
, The Thirty-third (2023) International Offshore and Polar Engineering Conference, 2023.06, The authors propose a towed vehicle with intentional instability for use in seafloor exploration. This towed vehicle has one pair of canard wings in addition to conventional main and tail wings. The hydrodynamic characteristics and the motion control performance of the multi-winged towed vehicle with the three control surfaces are investigated. First, CFD and experiments were conducted to investigate the effects of interference between the wings. Then, equations of the motion for the multi-winged towed vehicle were formulated and the simulations of the motion control were conducted. The calculations were performed for the longitudinal motion of the vehicle. Since this system has three control inputs (three wing angles) for two control outputs (pitch and heave), the control input to reach the target is not uniquely determined. For this reason, the authors reduced the number of control inputs by linking the angles of the tail and the canard wings at a certain ratio. The motion control simulations confirmed that the pitch and heave can be controlled almost independently, demonstrating the superiority of the multi-winged towed vehicle over conventional ones..  |
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Satoru Yamaguchi, Yu Fukuda, Yuta Shindo, Development of an Underwater Towed Exploration System for Archaeological Relics, TheThirty-second (2022) International Offshore and Polar Engineering Conference, 2022.06, Many archaeological relics such as a wreck of an ancient ship are remains under the sea bottom and most of them are untouched because of difficulties of underwater exploration. Usual sub-bottom explorations for offshore resources such as oil and gas are carried out using seismic and sonic prospecting instruments and it is high cost and time consuming. On the other hand, archaeological relics in the relatively shallow water are explored by a sub-bottom profiler and by divers so the area which can be investigated is very limited.
The authors have been developing underwater towed vehicles and autonomous underwater gliders in the previous studies. These vehicles equip various types of instruments including an OBEM (Ocean Bottom Electro-Magnetometer). They are promising instruments for marine environment survey and ocean floor resources exploration.
In this report, a towed exploration system for archaeological relics exploration is proposed and the development of the vehicle including a motion controller is discussed. The vehicle is towed near the sea bottom to improve the accuracy of the measurement using a sonic prospector. The performance of the towed system and its motion control system are assessed by tank experiments and numerical simulations.
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Satoru Yamaguchi, Yutaro Miyai, Transient Motion Control of an Underwater Glider Based on Numerical Analysis, TheThirty-first (2021) International Offshore and Polar Engineering Conference, 2021.06, The authors have been developing an autonomous underwater glider which equips an OBEM (Ocean Bottom Electro-Magnetometer). That is a hopeful instrument for the ocean floor resources explorations. The autonomous vehicle has an ability to achieve a continuous resource exploration autonomously for a long term. The motion control system for landing of the vehicle was investigated in the previous studies. In these reports, hydrodynamic performance of the vehicle in landing is examined by CFD calculations. The bottom effect which affects the lift and drag of the wings of the glider is studied and the characteristics of the blended wing body near a sea bottom is discussed.
On the other hand, the transient motions of the vehicle such as a deployment, the motion when the vehicle changes its buoyancy for cruise are also important problems for the motion control of the vehicle. The control system might be affected by the unpredicted change of the hydrodynamic forces acting on the body and the wing in the transient conditions. Consequently, it may cause deterioration of the performance of the control system.
In this report, these transient motions are investigated based on CFD analysis. The overset mesh approach is used to simulated the sequential maneuvers in the cruising of the underwater vehicle.. |
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Satoru Yamaguchi, Yutaro Miyai, Study on Hydrodynamic Performance of a Blended Wing Body for an Underwater Glider based on Numerical Analysis, TheThirtieth (2020) International Offshore and Polar Engineering Conference, 2020.10, The authors have been developing an autonomous underwater glider which equips an OBEM (Ocean Bottom Electromagnetometer). That is a hopeful instrument for the ocean floor resources explorations. The autonomous vehicle has an ability to achieve a continuous resource exploration autonomously for a long term. The buoyancy and attitude control mechanism of the vehicle enable to move to the next measurement point by gliding.
The vehicle which has a blended wing body measures the slight variation of electromagnet wave on the sea bottom and the landing point for the measurement must be precisely controlled by the motion control system. In the landing stage, it is predicted that surface effect of the sea bottom affects the hydrodynamic characteristics of the vehicle, and it might cause some problems on the motion control system of the vehicle.
The authors attempt to make clear the characteristics of the flow field around the vehicle in the vicinity of a sea bottom. The motion control system for landing of the vehicle was investigated in the previous study (Yamaguchi and Sumoto, 2019). In this report, hydrodynamic performance of the vehicle in landing is examined by CFD calculations. The surface effect by a sea bottom which affects the lift and drag of the wings of the glider is studied and the characteristics of the blended wing body near a sea bottom is discussed.. |
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Nitin D Thulkar, Satoru Yamaguchi, Koki Ebihara, Study of Drag Force Acting on Various Types of DP Jack-up Vessel Legs, TheTwenty-ninth (2019) International Offshore and Polar Engineering Conference, 2019.06, The Dynamic Positioned (DP) Jack-up vessels currently use two popular designs of legs, (i.e. rack & chord lattices and cylindrical leg type). These two leg designs are popular and various experiment conducted in the past to evaluate the drag coefficient and drag force of these legs, but they are only available in a steady state condition. The intention of our experiment is to measure drag force and compare with CFD results. In DP vessels, mathematical model of the vessel first estimates the environmental force acting on the vessel, by using real time sensor data and then generate the counter balance thrust. The output command of force and angle is then sent to the available thrusters. However, usually, DP Jack-up vessels do not have sensor to measure the hydrodynamic force of leg &spudcan. Presently, each DP control system manufacturer for Jack-up vessels uses its own mathematical technique to achieve stability of station keeping during simultaneous operation of dynamic positioning and Jacking operation (SIMOPS). Moreover, this sensor less DP system tuning is unknown to the industries. Our intention of these experiments is to measure the hydrodynamic forces, in order to understand how the evaluated forces is altered under different environmental and operational conditions in SIMOPS operation. To start with, we first decided to measure drag forces when leg & spudcan moves in UP/DN direction under variable environment current. Both CFD and tank experiment is done using 3D prototype scale model of a cylindrical leg. The experimental limitation is also defined based on the tank facilities. The data is recorded during lowering and raising of the leg to see the effect on the drag force of leg- spudcan. The experimental data are recorded for current, leg speed; drag forces etc. with respect to time and average value considered for a steady state experimental case period. The evaluated results are compared with CFD results and show similar trends with acceptable error. The CFD analysis also carried out on a full-scale leg diameter to see the drag force trends. In order to understand the effect of seabed on the overall hydrodynamic force, cases were studied in which the leg was kept just a 0.1 m above seabed.. |
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Satoru Yamaguchi, Hirofumi Sumoto, Landing Motion Control of an Underwater Glider for Ocean Floor Resources Exploration, TheTwenty-ninth (2019) International Offshore and Polar Engineering Conference, 2019.06, Ocean floor resources such as sea-floor hydrothermal deposit, methane hydrate and manganese nodule are promising resources for future ocean development. It is becoming apparent by recent research that certain amount of these resources deposit also near Japan. Though several kinds of exploration methods such as seismic exploration, a multi-beam echo sounder and a sub-bottom profiler which are equipped with a survey ship are used for the resource explorations in general, these exploration methods need a large amount of cost and efforts.
On the other hand, an autonomous underwater glider which equips an OBEM (Ocean Bottom Electromagnetometer) which has been developed in the author’s laboratory is a hopeful instrument for the ocean floor resources explorations. The autonomous vehicle has an ability to achieve a continuous resource exploration autonomously for a long term. The buoyancy and attitude control mechanism enable the vehicle to move to the next measurement point by gliding.
The landing point for the measurement must be precisely controlled by the motion control system because the vehicle measures the slight variation of electromagnet wave on the sea bottom. The performance in a landing stage is essential for the motion control of the vehicle. Here, the motion control system of a weight shift device in the vehicle’s pressure container is developed for a landing stage. The authors attempt to make clear the performance of the controller in this report. Moreover, the characteristics of a buoyancy control device is examined by tank experiments. This unit is used to raise the vehicle to an appropriate height for the next gliding.. |
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Nitin Thulkar, Satoru Yamaguchi, Koki Ebihara, Analysis of Viscous Drag Forces on Jack Up Service Vessels during Simultaneous Operation, 日本船舶海洋工学会秋季講演会, 2018.11, The deepwater energy market in oil and gas has hampered, however the shallow water market continues to grow. Although the renewable energy impacting the energy market but it is mainly affecting coal based thermal power plants, while oil & gas energy market continue to grow.
The purpose of this manuscript is to find the viscous drag force on DP Jackup vessel during SIMOPS operation. The DP system calculates leg interaction forces using fixed Cd Value and fed to DP system for thrust calculation during this SIMOPS (i.e. Jacking operation+ DP station keeping).
However, during the CFD analysis, it was concluded that Cd values varies during leg transient from higher Cd value to steady state.. |
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Satoru Yamaguchi, Landing Point Control of an Underwater Gliding Vehicle for Ocean Floor Resources Exploration, The 16th IAIN World Congress 2018, 2018.11. |
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Nitin D Thulkar, Satoru Yamaguchi, Evaluation of Drag Coefficient Variation in Transit Mode on Leg & Spud can of DP Jackups Vessel, TheTwenty-eighth (2018) International Offshore and Polar Engineering Conference, 2018.06. |
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Satoru Yamaguchi, Hirofumi Sumoto, Ryota Sakamoto, Ryo Nogami, Gliding Performance of an Underwater Glider for Ocean Floor Resources Exploration, TheTwenty-eighth (2018) International Offshore and Polar Engineering Conference, 2018.06. |
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Satoru Yamaguchi, Hirofumi Sumoto, Taishiro Katsu, Yasuki Kono, Development of an Autonomous OBEM Measurement Vehicle for Offshore Resources Exploration, TheTwenty-seventh (2017) International Offshore and Polar Engineering Conference, 2017.06. |
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Satoru Yamaguchi, Hideki Mizunaga, Taishiro Katsu, Satoshi Nakamuta, Yasuki Kono, Preliminary Design of an Underwater Glider for Ocean Floor Resources Exploration, TheTwenty-sixth (2016) International Offshore and Polar Engineering Conference, 2016.06. |
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Masaki Ishiguro, Akiji Shinkai, Satoru Yamaguchi, A Study on the Statistical Prediction of the Freak Wave Generation in the Ocean, TheTwenty-third (2013) International Offshore and Polar Engineering Conference, 2013.07. |
