A new perspective to velocity control for fixed wing UAVs

Abstract

Unmanned Aerial Vehicles (UAVs) are used in wide ranging applications by civil as well as military organizations all over the world. In an autonomous UAV, a controller onboard the vehicle automatically controls the aircraft's flight and navigation. Airspeed is an important aircraft state that is generally controlled using Proportional Integral Derivative (PID) controller in most of the commercially available autopilots. In this research work, we first used a PID controller to control the airspeed of Aerosonde UAV that has been modeled as a nonlinear system in Matlab software. On the other hand, we have also used a Phase Lead compensator to control Aerosonde's airspeed. For controller design, the nonlinear aircraft model is linearized around a stable trim point and airspeed controller is designed for the decoupled longitudinal model. Controller performance has been subsequently verified against the nonlinear aircraft model. A performance comparison of airspeed PID controller and Phase Lead compensator is carried out. Our findings show that the Phase Lead compensator performs better in controlling velocity of the UAV. It is expected that this research may lead to a more effective and efficient autopilot design for airspeed control of UAVs.