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.
In this paper a robust tracking controller is designed for a hydraulic actuator controlled by a variable displacement vane pump. The nonlinear model of the actuator is linearized around equilibrium points and a robust tracking controller is designed for the linear model covering step and ramp reference and disturbance signals. The proposed robust controller is applied to the nonlinear model. The robust stability of the closed loop linear model and the local stability of the nonlinear model are guaranteed under sufficient conditions. The robust controller is derived using a finite step algorithm based on a Hurwitz invariability technique. Simulation results for various uncertain model parameters are presented indicating the satisfactory performance of the robust controller for the nonlinear model of the hydraulic actuator.
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