2005 Fiscal Year Final Research Report Summary
Development of small tethered system for ocean inquitry.
| Project/Area Number |
14550223
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Dynamics/Control
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| Research Institution | Sophia University |
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Principal Investigator |
SOGABE Kiyoshi Sophia University, 理工学部, Professor (60095859)
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| Co-Investigator(Kenkyū-buntansha) |
TERUMICHI Yoshiaki Sophia University, 理工学部, Professor (50262118)
NOHMI Masahiro Kagawa University, 工学部, Associate Professor (20325319)
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| Project Period (FY) |
2002 – 2005
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| Keywords | Tethered System / Multibody Dynamics / Ocean Inquiry / Motion of Flexible Body / Large Deformation and Displacement / Interaction with Fluid Dynamics |
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| Research Abstract |
Tethers experiencing extension and retraction are important components of some mechanical systems and play a pivotal role. Its behavior during the mission is complex due to the large displacement, large deformation and time-varying length. In the modeling and formulation of the dynamic behavior of flexible bodies with large rotation, large displacement and large deformation, Absolute Nodal Coordinate Formulation (ANCF) is often used. In this approach, the resulting constant mass matrix leads to an improvement of the accuracy and reduces the calculation costs. The main interest of this study is to develop the modeling and formulation for the resulting constant mass matrix despite the time-varying length of the tether. In the finite element approach for tether system motion in extension and retraction, the mass matrix is generally time dependent due to the time-varying length of the tether. This leads to long simulation times and high calculation costs. Thus, the development of an effici
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ent numerical algorithm to predict the long-term dynamic behavior of such systems is needed. The feature of the proposed method in this study is the introduction of relevant dimensionless variables and the application of the method of multiple scales with nonlinear time scales in the modeling and formulation in ANCF. New nodal coordinates and a shape function are also introduced. The introduced nonlinear time scales, which correspond to the period of the first mode natural frequency of the tether fixed at both ends, is defined by using the element number and dimensionless element length. The new nodal coordinates, the new shape function and the multiple nonlinear time scales lead to the constant mass matrix in ANCF despite the time-varying length of the tether.
Some experimental approach with the experimental set up with a water tank has been completed, comparing with the numerical results. They are in good agreement and the validity of this proposed approach was confirmed. Then, it is expected that the position and attitude control will be applied. Less
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