A Thrust-Elevator Interaction Criterion for Aircraft Optimal Longitudinal Control

Abstract

The aim of this research is to investigate the combined use of throttle and aerodynamic control vanes for aircraft optimal control. A new disruptive aircraft configuration concept is presented, featuring control vanes downstream of two rear-mounted ducted propellers. The aerodynamic interaction between the horizontal vane and the throttle is analyzed in the scope of a longitudinal control study. A static criterion is proposed to discern the efficiency of the interaction, with respect to a generic pitch command. A traditional control allocation logic is used to exploit the throttle as a secondary pitch effector, and a modified version based on the interaction criterion is proposed; its behavior is tested through an open-loop design space exploration of actuator time constants and effectors prioritization weights. A flexible control system architecture is designed to compare the aircraft closed-loop response in conjunction with a phugoid damper loop. Results show that the best tracking performance is obtained with pilot commands allocated to the elevator, and phugoid damper commands to both elevator and throttle. The traditional allocation method achieves the best tracking performance at the expense of the largest control effort. The modified allocation alleviates the effort while still achieving better performance than the non-coupled control.