Attitude tracking control of a quadrotor UAV subject to external disturbance with L2 performance

Attitude stability plays an important role in the safe flight of quadrotor unmanned aerial vehicle (UAV). This paper aims to address the problem of attitude control of quadrotor UAV. The mathematical model of quadrotor system subject to external disturbance is first introduced. Then, a finite-time disturbance observer (FTDO) is developed to effectively compensate for external disturbance. It is proved that the disturbance observation error can be guaranteed to converge to zero in finite time. Based on the designed FTDO, a backstepping sliding mode control technique is proposed to stabilize three attitude angles of a quadrotor UAV, which can eliminate the tracking errors of attitude channel to zero asymptotically. Moreover, by constructing an auxiliary equation, the bound of transient attitude tracking error in terms of L-2 norm is derived. Finally, the comparative simulations are carried out to illustrate the effectiveness of the proposed control scheme and several statistical indexes are given to quantitatively evaluate the performance in terms of observation error, tracking error and control signal.