Shoichiro Takehara

Development of Tether Space Mobility Device

With the increasing use of the International Space Station, humans have more opportunities to work in space. In space, a mobility device that operates efficiently is needed. In this research, a mobility system called the “Tether Space Mobility Device” (hereinafter called TSMD) is proposed. In general, the tether is a cable or a wire rope. The proposed system has a mechanism that uses the tether for enabling a human to move to a target point. However, this system has the problem that the center of mass of the human and that of the TSMD are different from the direct line to the target point. Then, the human is rotated by the tension of the tether. Thus, to use this device safely, rotation of the human body must be controlled. For this reason, a numerical simulation model is proposed. The numerical model is composed of three rigid bodies and one flexible body that can express motion with large deformation and large displacement. In this model, winding motion of the tether can be expressed. An experiment of the TSMD was designed to move under two-dimensional microgravity. The experiment confirmed the validity of the numerical simulation model. The possibility of the mobility device using the tether and the influence of the control system are discussed.

Quantitative biomechanical analysis of transient body behavior during lateral-directional motion of vehicle occupant

In the design of a unified system by human and car seat, comprehensive methodology as the technique including principle and structure of mutual dynamic systems has been required and analyzed. However, these topics have been studied for only vibration measurement. The purpose of this study is to simulate biomechanical body behavior of vehicle occupant in lateral-directional transient acceleration using the carriage, the car seat, motion capture system and mobile force plate. In this paper, the seated body behavior with lateral-directional acceleration is simulated by the experiments and the obtained physical components are quantitatively evaluated by singular value decomposition. As a result of the experiments and data analysis, the effectiveness of the method to analyze biomechanical behavior of vehicle occupant during lateral-directional transient motion on the car seat and its quantitative evaluation concerning principal human motion patterns are validated. Obtained motion patterns may be useful for the efficient automobile design.

Motion of a Tethered System Under Attitude Control With Large Deformation, Rotation and Translation

In this paper, we discuss about the motion of a system consisting of a very flexible body and rigid bodies at its end under attitude control to the end body. A tethered subsatellite in space is known as an example of this system. We consider two mathematical models for flexible body. First, the flexible body motion in a plane is described by using Finite Element Method formulation. Second, the flexible body in planer motion is described by using Absolute Nodal Coordinate formulation. In this method, it is easy to describe the motion of the flexible body with large deformation, rotation and translation displacement. We can consider interaction between the deflection of the flexible body and the motion of the rigid bodies in these methods. Furthermore we attempt to control the attitude of the end body using a reaction wheel. The flexible body motion is influenced on the motion of the rigid bodies under attitude control of end body. The control technique consists of an attitude control by the reaction wheel and a control by the reaction wheel with the joint torque control to cancel accumulation of angular momentum. First, eigenvalue analysis is carried out where control gain changes. Second, the motion under controlled system is discussed under free vibration. We compared these results. Furthermore we treat large deformation problem. The end of flexible body moves horizontally. As a result, we confirm the interaction between flexible body and rigid body under the attitude control.Copyright