Antenna control systems for flexible structure under a wind load

Abstract

Higher levels of pointing (directional) accuracy are required with the increase of diameter of large reflector antennae. The influence of wind disturbance on the level of pointing error has become a serious problem with the increased size of antenna. Newer, larger antenna designs have to combine increased control and more accurate pointing mechanisms that challenge existing technology. With reference to the typical Cassegrain antenna, this paper aims to improve the accuracy of antenna pointing mechanisms under a variety of wind conditions. This is based on the pointing model derived from combining both structural dynamics and electromechanics such that the pointing error caused by wind can be estimated efficiently. Using different controller design methods, which present the flexible pointing error as a combination of rotation angle error, torque disturbance, and state disturbance, the pointing error is compensated effectively. Tests and analysis of a 7.3 m antenna have been conducted. The results show that the linear-quadratic-Gaussian controller can reduce the maximum pointing errors by 79.3%, and the sliding mode controller is found to significantly outperform other controllers as it has the smallest root mean square of pointing error.