Single-Loop Antenna Control

This article presents a study of a single-loop antenna control system. A typical antenna control system consists of two feedback loops. The first one—an inner loop—is called a rate loop. It uses tachometers to control the drive rate. The second loop—called a position loop—uses encoders to control antenna position. The questions arise: Does one need two loops to control antenna motions? Can one achieve similar performance for a system with the position loop only? In order to answer these questions, we studied three types of antennas with a single-loop control: a rigid (or idealized) antenna in order to obtain initial insight into properties of the closed-loop antenna systems; a small antenna, 5 meters in diameter; and a large antenna, 34 meters in diameter. The study compares command following and rejection of wind disturbances of antennas with and without rate loops, and we show that both configurations are equivalent.