Two-DOF H∞ Robust Controller Design for Radio Telescope Servo System

The pointing accuracy of radio telescope is affected by external disturbances. Additionally, the antenna's dynamic characteristics change with different working conditions due to the influence of gravity. To improve the radio telescope servo system's anti-disturbance and robust tracking performances, this paper proposed a two-degree-of-freedom (2DOF) H_inf robust controller. This controller is designed using the H_inf optimization procedure in a single step. The feedback controller designed, based on the loop shaping, is used to guarantee disturbance suppression performance and robust stability. A prefilter is employed to improve the robust model-matching properties of the closed-loop system. To verify the effectiveness of the control algorithm, a PI controller and the proposed controller are designed for the Nanshan 26m radio telescope (NSRT) servo system. Simulation results show that compared with the PI controller, the 2DOF controller can further improve both the tracking performance and anti-disturbance performance. Furthermore, the controller designed for the nominal model satisfies the robust tracking performance and disturbance rejection performance for the radio telescope working in any condition.