Constrained docking control for shipborne UAV SideArm recovery

In this work, we sought to investigate constrained docking control during shipborne SideArm recovery of an Unmanned Aerial Vehicle (UAV) under preassigned safe docking constraints, rough ocean environments, and different initial positions. The aim was to solve the UAV tracking-lag problem that manifests when attempting to dock with a rapidly moving SideArm and to improve the accuracy and rapidity of docking. First, together with the formulations of the shipborne SideArm system and environmental airflows, the affine nonlinear dynamics of the hook was established to reduce tracking lag. Then, echo state network approximators with good approximation capacity and low computational consumption were designed to accurately approximate the UAV's unknown nonlinear dynamics. With feedforward compensation provided by these approximators, a nonlinear-mapping-based constrained docking control law was developed for shipborne SideArm recovery of UAVs. This approach to controlling the docking trajectory and the forward docking speed of the UAV can achieve rapid and exact docking with a moving SideArm, without violating the preassigned safe docking-constraint envelopes. Simulations under different docking scenarios were used to validate the effectiveness and advantages of the proposed docking-control algorithm.