Closed Loop Performance Analysis of Classical PID and Robust H-infinity Controller for VTOL Unmanned Quad Tiltrotor Aerial Vehicle

Unmanned Aerial Vehicles (UAVs) guidance, control and navigation have directed the attention of many researchers in both aerospace engineering as well as control theory. Due to the unique rotor structure of Tiltrotor hybrid UAVs, they exhibit special application value. Quad Tiltrotor UAVs set up a distinctive platform that satisfies the needs of the varying mission requirements by combining the conventional features of high-speed cruise capabilities of an aircraft and hovering capabilities of a helicopter and by tilting its four rotors. The aim of this research article is to control the attitude and altitude of the UAV in the presence of uncertainty using two different control techniques. This paper addresses the comparative analysis of the robust H-infinity controller with classical PID control designs for the transition manoeuvre of a hybrid UAV: the VTOL Tiltrotor UAV. The proposed controllers achieve hover to cruise mode transition and vice-versa. The main idea behind the design of controller is to model and analyze the UAV’s position and attitude dynamics. The desired flight trajectory and the transition manoeuvre is achieved by controlling the tilt angle in 15° intervals from 90° to 0° and vice-versa. Performance index subjected to IAE is estimated and compared for both the controllers in the presence of noise, disturbances and uncertainties. The results of simulation illustrate that the robust H-infinity controller achieves better transition, good adaptability, robust performance and robust stability for the whole flight envelope when compared with the PID controller.