Synthetic design and analysis of the new feed cabin mechanism in Five-hundred-meter Aperture Spherical radio Telescope (FAST)

Abstract

Due to the large weight of the feed cabin, the observation range of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is limited and unable to cover the galactic center. To solve this problem, a new feed cabin mechanism (NFCM) is designed to replace the heavy rigid components using the novel lightweight cable-driven structure, where the observation-related characteristics are investigated. After dimensional optimization, the observation range is analyzed using a two-level optimization that has explicit graphic-based solutions, the parameter sensitivity is studied by proposing the direct numerical method, and the anti-disturbance ability is discussed using the novel disturbance unit increment method. Numerical simulations indicate that the optimal designed NFCM can achieve required larger observation range with exceptional observation performance. Additionally, considering the two-level control mode of FAST, a novel controller is proposed for the NFCM by addressing dynamics in the non-inertial frame, and the control performance in time and frequency domain is validated using actual observation data, where the NFCM can effectively suppress residual errors from the outer six-cable-driven system in FAST and has satisfactory control robustness in resisting system disturbances.