Robust H_∞ control for miniature unmanned aerial vehicles at hover by the finite frequency strategy

摘要

This study presents control synthesis of a miniature unmanned aerial vehicle to improve its hovering capability in the presence of wind disturbances. By time-scale techniques, the six-degree-freedom flight system can be decoupled into subsystems in different time-scales: one including slow-varying translational dynamics and Euler angles, and another composed of fast-varying angular velocities. To avoid contradictions between subsystems, control specifications for subsystems are classified, respectively, in disjoint frequency ranges. Robust controllers, applied directly to the original flight system, are formulated by composing the sub-controllers. To achieve desired handling and flying qualities, wind characteristics are considered, and a novel flexible strategy is then developed to ensure an adequate response in all flight modes under different weather conditions. The effectiveness and merits of the proposed methods are illustrated with a simulation example.