Observer-based Super-twisting Sliding Mode Control of Quadcopters

This paper focuses on the problematic position tracking of a quadcopter under external disturbances by developing a super-twisting sliding mode controller (STSMC) based on a higher-order sliding mode observer (HOSMO). A generalized quadcopter model is presented with position and attitude dynamics. This observer-based controller design is applied adaptable for future hardware implementation on a COEX Clover 4.2. The Clover drone has measurable position signal using vision-based navigation and ArUco marker localization, where the HOSMO can estimate the unknown state being linear velocity. HOSMO helps in estimating the unknown external disturbances on the quadcopter for possible compensations. The proposed controller has been applied to the position dynamics with extensive simulations. If desired, it could be applied to the attitude dynamics as well. Lyapunov- based method is used to investigate the closed-loop stability and convergence while a smoothing function was used to attenuate potential chattering problems. Part of the Proceedings of the Canadian Society for Mechanical Engineering International Congress 2022.