Compensation of vibration-induced pointing error caused by wind disturbances in large antenna

Abstract

Under different working conditions, scientists need to ensure that the pointing performance of large reflector antenna; however, wind disturbances are the most tricky problems that minimize the pointing accuracy. This is because the wind disturbances have randomness and time-varying characteristics. Davenport spectrum has been widely used to estimate the frequency domain of wind; moreover, it is also used to design the antenna controller in such a way that the servo angle error caused by wind torque gets minimized significantly. But it is difficult to ensure pointing accuracy without considering the reflector vibration caused by wind force. Therefore, this paper proposes a novel method to overcome wind disturbances. This method introduces the concept of predictable pointing errors in the servo controller. All these predictable errors are induced by vibrations. First, we developed an analysis model to determine pointing errors caused by wind. Second, we develop the wind forecast technique to estimate the future load on antenna structure. Third, using the model predictive control (MPC), we design a novel controller to compensate the future pointing errors. Finally, we conduct a series of tests and analysis. For a 7.3 m antenna, the results indicate that when MPC controller is used in the system, the resultant pointing errors are seven times smaller than the errors witnessed under the traditional controller. This indicates that MPC controller is effective in improving the pointing performance.

Keywords

Reflector antenna model predictive control pointing accuracy reflector vibration wind disturbances

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