Robust stabilization of a three-axis ship-mounted mobile antenna system

The demand for on-line information in diverse environments has driven the development of mobile satellite communication terminals. These high-data-rate systems require antenna pointing accuracy within fractions of a degree. In mobile applications, however, platform base motion complicates the pointing task and must be compensated. To mitigate these disturbances and ensure uninterrupted communication, gimbaled motorized pedestals are employed. This paper investigates the robust stability and performance of a three-axis ship-mounted mobile antenna stabilization system. The azimuth axis was selected for detailed analysis, as it is most affected by dynamic coupling. Typical uncertainties in the system dynamics were defined, and an H∞ controller was synthesized for the closed-loop uncertain system. The controller was benchmarked against a baseline PI controller, and the margins of robust stability and performance were computed. The analysis pinpointed the dominant uncertainty sources that undermine system robustness, forming the basis for targeted controller improvements.