Attitude control of VTOL-UAVs

This paper presents a novel control approach to obtain asymptotic attitude stability of a quadrotor as a representative of Planar Vertical Take Off and Landing (PVTOL) Unmanned Aerial Vehicles (UAVs). The considered quadrotor is a symmetric VTOL-UAV with four rigid mono-directional propellers, which has been modeled based on quaternion representation with taking Coriolis and gyroscopic torques into account. In the proposed approach, two nearly equivalent control laws (model independent as well as model dependent) have been used to obtain exponential stability of attitude angles and asymptotic stability of attitude angular velocity of the quadrotor UAV. The proposed approach also presents how the attitude parameters i.e. attitude angles and attitude angular velocity can be quickly regulated to their desired values as required.