An Application of a Fuzzy Controller in the Adjustment System of the Sub-Reflector of the 25m Radio Antenna of the Xinjiang Astronomical Observatory

In this paper we present a detailed study of the performance of the adjustment system of the sub-reflector of the 25m radio antenna at the Nanshan Station of the Xinjiang Astronomical Observatory. Our study is to fit the plan of transforming the 25m antenna, which is to improve overall electric performance of the antenna through real-time compensation from the sub-reflector and to realize auto-switch of feeds. A key component of the adjustment system is its control system based on a fuzzy controller. In our study we use the Simulink to simulate the performance of the fuzzy controller in controlling the servo system of the 6-DOF parallel platform for different settings. The settings consist of the combinations of two cases of input signals (step signals and sinusoidal signals) with two cases of noise (vanishing noise and non-vanishing noise). Our study includes a detailed error analysis to obtain optimal parameter values of the control system as well as key performance parameter values of the adjustment system of the sub-reflector, which is under the control of the fuzzy controller. We have found that in the cases of sinusoidal signals as input signals the errors of system response do not exceed 0.09mm, and in the cases of step signals as input signals steady-state errors of the system do not exceed 0.0011mm with the adjustment time at about 0.3s. Our experimental results show that the overall performance of the control system based on the fuzzy controller is sufficient for it to accurately, reliably, and promptly adjust the sub-reflector. The control system based on the fuzzy controller is thus valuable in improving the electric performance of the 25m antenna, in the sense that it can meet the requirements of data accuracy and system reliability in astronomical observation and deep-space exploration.