| Co-Investigator(Kenkyū-buntansha) |
YOSHIDA Kazuya Tokyo Institute of Technology, Engineering, Research Associate, 工学部, 助手 (00191578)
MATUNAGA Saburo Tokyo Institute of Technology, Engineering, Research Associate, 工学部, 助手 (00222307)
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| Research Abstract |
In low-earth oribiting spacecraft acceleration is induced by various kinds of environmental disturbance sources (e.g.gravity gradient, rotational motion of spacecraft, solar radiation pressure, aerodynamic drag, vibration caused by spacecraft's flexibility, rotating machines and crew activities). To get a better microgravity environment, it is essential to know the level and fluctuation of the microgravity environment in spacecraft. Based on the investigation of fundamental aspects of microgravity, the authors have analyzed the level and fluctuation of the microgravity environment for a single rigid spacecraft and a large flexible spacecraft. Both of them are under influence of gravitational force, solar radiation pressure and aerodynamic drag. The analysis covers the dependency upon the (1) orbital position, (2) position from center of mass within spacecraft and (3) structural vibration. For various configurations of Space Station Freedom, the residual acceleration levels have been evaluated as examples of the approached noted above. It is shown that the residual acceleration fluctuates significantly, the magnitude, and the direction achieving the order of 10-5 G,and that the residual acceleration is strongly dependent on the structural flexibility, attitude control and structural configuration.
In order to suppress the above vibration of the structure, we also studied basic characteristics and control performance of a bang-bang actuator : we analyzed 2/3 DOF model and conducted numerical simulations and experiments using 2/3 DOF model and a free-free beam model. The control methods using information on velocity, acceleration and displacement, fuzzy logic control and rule based control were applied.
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