Improved helicopter flight control

Abstract

An Apache AH-64D simulation model designed by Boeing and McDonnell Douglas, is used to improve the handling qualities of this helicopter to level 1 during both good and degraded visual environments for the full helicopter flight envelope. This project results from the design phase of a follow-up project with the goal of extending an Incremental Nonlinear Dynamic Inversion controller to work with a hypothetical full-authority Fly-By-Wire system for the first time. Regarding previous Apache flight controller designs with limited control authorities, oscillations were severe due to the effect of a high bandwidth nonlinear flight controller on the main rotor dynamics. A significant improvement is found by implementing an inner control loop which regulates the disk flapping angles of the main rotor. A translational rate and attitude command controllers are provided through a system of cascaded outer-loops. A position hold and sideslip controllers are implemented as well to complement this nonlinear closed-loop system. Offline simulations are performed in Simulink to validate the capabilities of this control system. An initial piloted experiment is performed with a professional Apache test pilot to assess the handling quality levels on the SIMONA Research Simulator. This evaluation has shown the possibility of level 1 handling qualities within a broader range of the flight envelope of military helicopters.