Modeling and Hovering Attitude Control of a Prototype Tandem Ducted Fan Vehicle

Abstract

The problem of attitude stabilization of an unconventional tandem ducted fan aircraft in a hover configuration subject to low-order controller structure constraint is addressed. The novel vehicle is naturally unstable and exhibits cross-coupling among the longitudinal, lateral and heading motion on the aircraft, so the design of flight controllers is not straightforward as in the conventional fixed-wing aircraft case. Three independent controls mixing are constructed as control inputs. An accurate yet simple enough dynamics model is first presented based on the first principles and static experimental tests. To facilitate the practical implementation, direct design of low order controller within Linear Matrix Inequalities framework is adopted to construct an autonomous flight control law for the platform. Details of the static loop shaping controller design are presented, together with a comprehensive analysis of simulation tests. Military rotorcraft handling qualities specifications are utilized as a reference to evaluate the controller performance. Classic $H_{\infty }$ loop shaping and conventional PID are also applied to the same plant for comparison. The resulting static robust controller produces just three states with guaranteed robustness and achieves the top level performance in accordance with the military rotorcraft standard ADS-33D-PRF (Standard 2000).