Saturated adaptive sliding mode control for autonomous vessel landing of a quadrotor

An autonomous vessel landing control algorithm of a quadrotor with input saturation and parametric uncertainties is investigated. To facilitate the controller design, the problem of vessel landing is converted from general trajectory tracking problem of a quadrotor to a stabilisation problem of relative motion. A non-linear and coupled six-degrees-of-freedom relative position and attitude model with uncertain parameters and external disturbances is established. The proposed controllers are composed of a relative position controller (RPC) and a relative attitude-altitude controller (RAC). The quadrotor is first commanded by RPC to reach above the vessel, as it reaches, RAC is initiated to guide the quadrotor to descend steadily on the vessel. Both RPC and RAC employ the saturated adaptive sliding mode control technique. The parametric uncertainties and disturbances are estimated by adaptive algorithms, while the control input saturation effect is compensated by linear compensators. All signals in the closed-loop systems are proved uniformly ultimately bounded via Lyapunov theory. Numerical simulations validate the effectiveness of the proposed control approach.