A radio astronomical observatory satellite ``ASTRO-G'', which will be launched in 2012, has two characteristics: flexible appendages and high-speed and high-precision attitude maneuvering. Because of these two antithetical features, attitude control system (ACS) of ASTRO-G becomes quite challenging in comparison with those of past satellites. For such a satellite, feedforward control which is robust to model identification error is considered to be important. Nil-Mode-Exciting (NME) profiler is one of references for anti-vibration, which is designed to excite no flexible modes, and thus its robustness is considered to be of most significant. NME profiler, however, is relatively slow reference because of negligible high frequency component. In this paper, we propose Modified NME profiler which is relatively fast reference designed by convolution of NME profiler and Input Shaper. Some anti-vibration experiments are carried out to show the effectiveness of the proposed reference.
In this study, effects of the confined area geometry on the aerodynamic performance of the hovering rotor are showed from experiments from standpoints of flight safety. The confined area is simulated putting up vertically a single plate or plural plates on the ground effect plate. The aerodynamic performance of the rotor changes because a part of the rotor wake upward along the walls interferes with the flow field around the rotor. It is shown that the behavior of the steady torque coefficients remarkably depends on the combinations among the space between walls, the wall numbers, and the rotor height, and the required torque coefficient increases at all rotor height compared with that above the ground without walls. And also, there is the required torque coefficient in ground effect which can exceed that out-of-ground effect.
To investigate the internal structure of LSD waves, electron density distribution ne was measured by two-wavelength Mach-Zehnder interferometer and electron temperature Te was by emission spectroscopy. As a result, peak values of ne and Te were about 2 × 1024m-3 and 30,000K, respectively. Based on the measured properties, laser absorption coefficient was calculated. It showed that incident laser energy was perfectly absorbed in a layer much thinner than a plasma layer, situation of which was not predicted by the conventional LSD model. Measured ne at the shock front was not zero while LSD was supported. This suggested that the precursor electrons exist ahead of the shock wave.