Exponential Reaching Law based Robust Trajectory Tracking for Unmanned Aerial Vehicles

This paper addresses the problem of three-dimensional trajectory tracking of unmanned aerial vehicles, specifically quadrotors. Firstly, a two-loop hierarchical control design is proposed based on the time scale separation. Then an asymptotically convergent robust nonlinear control strategy is proposed for both loops to ensure the quadrotor's high precision trajectory tracking using the sliding mode control. In this approach, the reaching law is designed using an exponential function that dynamically adapts to the variation of system states and ensures the chattering reduction in the quadrotor's inputs. The robustness of the proposed controller is tested in the presence of large initial deviations and time-varying disturbances using simulations.