Robust Nonlinear Backstepping FTSMC of a Quadrotor UAV-Suspended Load System with Obstacle Avoidance and Swing Attenuation

Quadrotor Unmanned Aerial Vehicles Slung Load (QUAVL) systems are affected by the load's unstable oscillation thereby degrading the whole system's performance during flight. As a result, the ease of navigating a QUAVL system in a cluttered environment may be hindered by the load swings which can potentially derail the system from its intended trajectory and cause damages to man and the environment. Furthermore, the accuracy of load placement may also become a bottleneck. Therefore, the adoption of a stabilising controller, an obstacle avoidance strategy and swing suppression is necessary. This work proposes a Nonlinear Backstepping Finite-time Sliding Mode Control (BFTSMC) of an under-actuated (QUAVL) with swing suppression. The controller design is based on Lyapunov stability stand point whereby the effect of load swing is mitigated with an anti-swing control through delayed feedback. Simulation results are used to validate the controller design.