CCAT mount control using de-convolution for fast scans

Abstract

CCAT will be a 25-meter telescope for submillimeter wavelength astronomy located at an altitude of 5600 meters on Cerro Chajnantor in northern Chile. This paper presents an overview of the preliminary mount control design. A finite element model of the structure has been developed and is used to determine the dynamics relevant for mount control. Controller strategies are presented that are designed to meet challenging wind rejection and fast scan requirements. Conventional inner loops are used for encoder-based control. Offset requirements are satisfied using innovative command shaping with feedforward and a two-command path structure. The fast scan requirement is satisfied using a new approach based on a de-convolution filter. The de-convolution filter uses an estimate of the closed loop response obtained from test signals. Wind jitter requirements remain a challenge and additional sensors such as accelerometers and wind pressure sensors may be needed.

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