Full envelope flight control system design using quantitative feedback theory

Abstract

A controlled plant's characteristics can vary widely throughout its operational envelope. This is a major problem in nominal plant-based control system design. Hence, gain scheduling is often used for full envelope design. In this paper, it is proposed to address the plant's variability using robust control design concepts, minimizing the need for gain scheduling. In particular, the frequency-domain-based quantitative feedback theory multiple input multiple output robust controls design method is employed for the synthesis of a full envelope flight control system for an F-16 aircraft derivative. Qualitative feedback theory addresses structured uncertainty that is caused by full envelope operation. Thus, qualitative feedback theory robust control is particularly suited for full envelope controller design. Compensators and prefilters for the aircraft's pitch and lateral/directional channels are designed to meet level 1 flying qualities specifications, and these designs are validated using simulations.