Extended Discrete-Time Quasi-Sliding Mode Control for VTOL UAV in the Presence of Uncertain Disturbances

The discrete control problem of vertical take-off and landing unmanned aerial vehicle (VTOL UAV) in the presence of time-varying uncertain disturbances is developed in this paper. The complexity of control problem is managed by dividing the dynamical model into two subsystems i.e. translational dynamics and rotational dynamics, where each subsystem is composed of three states. A discrete-time quasi-sliding mode control (DTQSMC) is extended to maintain the trajectory tracking control by proposing a new-reaching law for VTOL UAV. A robust controller is designed to handle unknown time-varying disturbances acting upon the translational and rotational dynamics. Moreover, the proposed controller is designed to reduce the chattering issue that commonly appears in conventional sliding mode control (SMC). Rigorous mathematical proof is presented to analyze the stability of the entire closed-loop system. The performance of this design is demonstrated with numerous numerical analyses and simulations.