Practical Wind-Disturbance Rejection for Large Deep Space Observatory Antenna

Abstract

The wind-load disturbance is the major factor that affects the pointing and tracking accuracy of a large deep space observatory antenna. An antenna position control scheme is proposed based on the most popularly used proportional-integral-derivative controller. The wind-load torque and other uncertain mechanical dynamics are treated as external and internal disturbances, respectively. All disturbances considered as a whole can be estimated and compensated based on an extended state observer, which can attenuate the adverse effects caused by the wind. The mechanism of electric motor is used to simplify the design procedure and reduce the required order of the observer. In addition, only minor control software modifications are required for the existing control system of the antenna. At first, the effectiveness of the proposed approach was illustrated by mathematical simulations. Then, this methodology was applied to a practical installation. In the experiment, a 65.2% reduction of overshoot and a remarkable amelioration in the capacity of wind-disturbance rejection were achieved, whereas the tracking precision was also improved significantly. In addition, the proposed method can also reduce the possibility of wearing and tearing of the installation.