Longitudinal flight multi condition control using robust PID controllers

A multi flight condition aircraft control autopilot system is proposed to control the horizontal flight of an aircraft involving atmospheric gusts. The control system involves a robust PID controller that stabilizes the closed loop system for various flight conditions. Considering the stability derivatives of the aircraft and the velocity of the aircraft to be uncertain parameters the robust stabilizing and disturbance attenuation controller is designed to cover full envelop pitch control. The robust PID controller parameters are computed using a finite step algorithm based on a Hurwitz invariability technique. Solvability conditions are derived. Simulation results for four different flight conditions are presented indicating the satisfactory performance of the robust controller in the presence of atmospheric gusts.