Shoichiro Takehara

In this paper, the dynamic characteristics of a small wheel bicycle are discussed. In the dynamic analysis with multibody dynamics, the influence of the head angle on the small wheel bicycle is investigated. With the driving experiment of the small wheel bicycle, straight-ahead stability and upstanding stability are evaluated by the subjects and measured by the experimental apparatuses. The results show the smaller head angle has more stability and the results are corresponding with the simulation results.

The tethered system, which composed with a mother ship and satellite connected with tether, is an example of recent satellites. In the analysis and modeling of tether, large deformation and large displacements must be considered. The Absolute Nodal Coordinate Formulation can describe the motion of tether. In the modeling method, internal damping and fluid resistance are not considered, and the identification for such parameters is still problem to be solved. In this study, the effect of damping and fluid resistance based on strain energy and drag equation are formulated while considering a parameter identification method. These parameter and number of elements are identified by the experiment at the same time. In order to verify the modeling method, an example of swing-up control using a genetic algorithm is performed in simulation and experiment. Validity of model and availability of motion control based on multibody dynamics are shown comparison between experiment and simulation.

In this study, the modeling and formulation for tether motion with time-varying length, large rotation, large displacement and large deformation are proposed. A tether or cable is an important element in lift systems, construction machines for transportation and often is used with a time-varying length. In some cases, these systems are large and the tether has a long length, large deformation and large displacement. The dynamic behavior of a tether in extension and retraction using the proposed method is discussed in this paper. In the passage through resonance, significant tether motions with large rotation and large deformation result. In the analysis of this phenomenon, the transient fluctuations of the motion amplitudes are examined and compared with the corresponding steady state motions. The accuracy and the cost of the calculations are also verified by comparison with the experimental results.

Tethered satellite systems (TSS offer various attractive potential applications in space, and therefore, they have been an object of study for over two decades. It is difficult to expect its motion under an existing numerical model of a string, which confirmed by experiment on the ground. Hence, we performed the experiment for analyzing motion and vibration of a tether under microgravity, in order to construct a simulation model of a space tether. Several kinds of experiment for a tether were done using the drop shaft, which can provide microgravity environment during about 4 seconds. Tether motion was measured by tracking white markers at constant intervals on the tether. Pictures taken by two CCD cameras make it possible to obtain a position in 3D space by image processing software. Basic motion of a constant length tether was examined. Also, retrieval of a tether having a rigid body at its end was performed.