LQG compensator for large antenna under wind disturbance

An increased frequency band requires a more accurate pointing ability in large antenna. Accurate tracking by large antenna must be assured during changing weather conditions. However, because of the outdoor nature of their operations, and especially for those with a low natural frequency, the antenna could be severely influenced by the wind disturbances. Furthermore, it would be difficult to compensate for any pointing error due to reflector deformations which are usually hard to estimate and are ignored. To decrease the pointing deviation, caused by flexible deformation of the antenna structure under wind load, a robust control method with wind rejection is proposed. Firstly, the pointing errors arising from structural deformation are analysed and a pointing control-oriented antenna model catering for the flexible deformation of the structure is presented. Secondly, a linear-quadratic-Gaussian (LQG) controller is designed to reject wind disturbances. Finally, a series of simulations of a 7.3 m antenna is conducted. Compared with the traditional proportional-integral-derivative (PID) controller, the pointing error could be reduced by 77.5% with the compensation method proposed under the wind speed at 10m/s.