Design of Reaction Mass Dampers in the Suspension for the FAST Focus Cabin

The FAST (Five-hundred-meter Aperture Spherical radio Telescope) focus cabin is suspended and driven by 6 cables, moving on a spherical cap of ~ 206 meters in diameter.Due to the low stiffness and weak damping of large-span cables, vibrations of the focus cabin are expected normally excited by wind-impact and other disturbances from the capstans, which can significantly influence the pointing accuracy of the telescope.A reaction mass damper is effective and reliable for vibration control.In this paper, designs of reactive mass dampers are investigated to suppress vibration and increase damping.As a result of the numerical analysis and dynamical simulation, we show that reaction mass dampers have satisfied performance in suppressing vibrations of the focus cabin and in improving the pointing accuracy of the telescope.