The Autonomous Landing of Rotary-Wing UAVs on Underway Ships in a Sea State
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There is a desire among researchers, governments, corporations and the public to learn more about our environment. To learn how it is changing, how it can be more efficiently used, interacted with, protected and understood. Some of these environments are also some of the harshest, meaning any tool that can help mitigate risks, decrease costs and maximize opportunities should be considered, such as unmanned aerial vehicles (UAV). In order to fully unlock the potential of these tools some infrastructure is lacking, mainly their recovery at sea. Current technologies focus on vision-based systems and very few end-to-end autonomous ship based algorithms have been demonstrated. Most current technologies also require very calm sea states. Here, a novel autonomous landing technique is presented. The algorithm uses acoustic positioning to allow for landings in a wider breadth of conditions and reduces the reliance on specially designed landing targets. It also features a potential fields path planner to adapt for ship motion and provide some obstacle avoidance and natural biasing away from the heaving deck. The autonomy uses a sea state predictor to compensate for harsher sea conditions and ship motion, allowing the UAV to look for appropriate landing windows in higher sea states. Autonomous landings are demonstrated in simulation and in a lab setting for sea conditions up to, and including, sea state 5. The ship motions in these sea states are defined using real sea trials data from the decommissioned Annapolis-class destroyer HMCS Nipigon.