High gain and super-twisting sliding mode observers for the adaptive control of quadrotor UAV

This paper presents a comparative analysis of two non-linear estimation techniques namely high-gain observer (HGO) and super-twisting sliding mode observer (STSMO) when applied for output feedback model-based control of the Quad-copter. Under the restriction that absolute position w.r.t initial frame and attitude angles are available while remaining velocities are estimated on-line. Adaptive Sliding mode control was developed and implemented as a control scheme for the closed-loop system to handle not only the aero-dynamic parameter uncertainties, external disturbances and modelling in-accuracies but also to improve performance and reliability of the Quad-copter flight. The performance of the non-linear observers are evaluated in terms of their closed-loop behaviour, ability to cope with model imperfections and process uncertainties such as measurement errors and uncertain initial conditions. Based on the simulations results a performance comparison of both observers is made with adaptive sliding mode control as control scheme.