# Re-Optimized Design for the ADR-Based Dual-Loop Controller of 100 m Class Aperture Radio Telescope
## 1 Introduction
considered the influence of the antenna reflector structure deformation under wind on pointing and employed the LQG controller to reject wind disturbances. [PERSON] et al. [12] proposed a compound control strategy to address the coupling between flexible deformation and rigid displacement in a large reflector antenna, in which the PID controller is for rigid-body model control, while the LQG is for flexible control. [PERSON] et al. [13] improved an LQG controller in the position-loop to attenuate flexible factors to increase the gain of the PI, consequently reducing the position errors. Although the model-based LQG/H\({}_{2}\) controller claims it is an optimal design and can attenuate structural resonance, it cannot obtain the desired control performance due to the existing model uncertainties, which are universal and non-negligible for the controlled plant. H\({}_{\infty}\) is proposed to deal with the model uncertainties; thus, it is insensitive to model uncertainties and can achieve better control performance than LQG/H\({}_{2}\) in the presence of model uncertainties [14]. The applications of H\({}_{\infty}\) in antenna servo systems have been widely studied. In [15], H\({}_{\infty}\) is used for improving the ship-mounted tracking antenna's tracking accuracy. [PERSON] et al. [16] designed a robust H\({}_{\infty}\) double-feedback controller based on a typical PD controller cascaded with a structure filter to deal with the flexible structure uncertainty. In [17], a bi-objective control architecture is proposed for achieving an optimal H\({}_{2}\) tracking performance by a central controller under low-level disturbance, and a robust H\({}_{\infty}\) anti-disturbance performance at significant disturbance via a disturbance filter. Rationally estimating the plant's model uncertainty is challenging, especially for control engineers without comprehensive knowledge of the plant operating conditions. Furthermore, since these two kinds of methods are model-based, the order of the designed controller is not less than that of the plant models. A controller with high orders may be limited in application without considering order reduction. QFT is also an H\({}_{\infty}\) control approach; it is designed on a Nichols diagram and can directly design a low-order robust controller. [PERSON] [18; 19] applied the QFT to a large radio telescope's servo system to improve its control performance. However, the design was made on an exclusive design platform, thus bringing a limit to its application. SMC [20] is also used for antenna servo control to improve response rapidity and control accuracy; however, it leads to chattering due to the switch between different sliding mode surfaces, which is detrimental for a multiple-body flexible system like a large antenna. So, it is not common in the field of antenna control. DOBC, EID, and ADRC are classes of active anti-disturbance control approaches. [PERSON] et al. [21] augmented a disturbance observer (DOB) on the base of the original controller in an antenna's position-loop to estimate and compensate for the equivalent disturbance in the input channel, thus enhancing the pointing properties of the antenna. The DOB, however, cannot work due to unstable poles when the plant model is in the non-minimum phase, thus limiting its application. [PERSON] et al. [22] considered the non-minimum-phase properties in antenna servo systems due to communication lag, and designed an EID controller to achieve high-accuracy control of an antenna. Like H\({}_{2}\) and H\({}_{\infty}\), the EID controller is also model-based, and the high order of the controller makes it more parameterized, limiting its application to some extent. Different from DOBC and EID, the typical ADRC is a model-free active anti-disturbance control method. It has a lot of successful engineering applications. For example, [PERSON] et al. [23] applied it to a DSN antenna to achieve a good anti-wind-disturbance performance.