Visual pose estimation for shipboard landing of autonomous parafoils
This paper outlines an investigation into the use of a simple, focal-plane imaging sensor for guidance of an autonomous parafoil system for approach and landing on a moving platform such as a ship underway. The perspective-projective transformation between an object in a three-dimensional world and an image on a two-dimensional plane is analyzed and then formulated using a homogeneous coordinate system. The estimation problem is addressed; specifically, the challenge of dealing with the out-of-frame condition due to parafoil oscillation as it approaches the target. A dual-mode Kalman estimation-scheme is proposed that suspends measurement when the target is out-of-frame, and incorporates a two-view measurement when the target reenters the frame.
Shipboard Landing Challenges for Autonomous Parafoils
This paper examines some of the challenges that must be overcome if future aerial delivery systems are to have the capability to land on the flight deck of a ship underway. The unique aspects of trajectory planning for landing on a ship’s flight deck are first examined, followed by formulation of the position estimation problem for a moving target. Some preliminary investigations into characterizing the wind over a moving landing platform at sea are then described. Finally, experimental results are presented for testing of a small prototype autonomous parafoil with a simple moving target on land.
Improved Surface Layer Wind Modeling for Autonomous Parafoils in a Maritime Environment
This paper investigates the use of atmospheric boundary layer theory to produce more accurate wind estimates for guiding an autonomous parafoil during the last portion of its flight before touchdown. The problem of wind estimation for a prototype autonomous parafoil aerial delivery system is first explained, followed by the simple assumptions for wind estimation that its guidance algorithm makes. A logarithmic wind profile model in the atmospheric surface layer is then introduced. The parameters and limitations of this model are discussed, along with the characteristics of this model that make it especially useful over the surface of the ocean. Finally, the incorporation of this model into the guidance algorithm of the prototype aerial delivery system is discussed, and subsequently evaluated in flight tests against the original algorithm that did not include the logarithmic surface layer wind model.