An open-loop control algorithm of the active reflector system of FAST

An open-loop control algorithm is put forward for continuous paraboloid deformation of the active reflector system of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The method is based on a calibration database and interpolation in 2D spatial domain and temperature domain, respectively. It is completely independent of real-time measurement of cable nodes so that it has advantage of working all-weather and no additional electro-magnetic interference (EMI). Furthermore, its control accuracy can be effectively improved via reasonable layout of the calibrated paraboloids and increasing calibration accuracy. Meanwhile deformation safety is considered via calibration as well. Finally its control accuracy is also confirmed via site measurements of paraboloid deformations. (paper)