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.
Precision Guided Airdrop for Vertical Replenishment of Naval Vessels
Abstract : This paper addresses the investigation into the feasibility of the use of precision guided airdrop as a means to deliver cargo to naval vessels at sea. In this context, precision guided airdrop means delivering unmanned cargo packages that, once dropped from an aircraft at high altitude, have the capability to guide themselves to a precise landing point by con- trolling an aerodynamic decelerator (parafoil or parachute) to which the cargo package is attached. The paper describes the problem of replenishment of naval vessels at sea and describes the benefits that the application of precision airdrop might provide. Improved accuracy of aerial delivery systems is the major focus of analysis, and how the application of model predictive control has potential to achieve the necessary improvements in accuracy that would make shipboard landings possible. A simple example is developed of a model predictive control algorithm adapted to track a target landing area that is moving with constant velocity. Additional techniques are also surveyed, as well as other potential applications of precision airdrop to maritime operations.
Ozonation of polycyclic aromatic hydrocarbons in oil/water-emulsions: mass transfer and reaction kinetics.
The ozonation of highly condensed polycyclic aromatic hydrocarbons (PAH) was studied in oil/water-emulsions, which are comparable to poorly water-soluble PAH in industrial wastewaters and at contaminated sites. As there was a lack of knowledge about the ozonation in oil/water-emulsions, first the ozone mass transfer was studied and optimized from the gas to the water phase and from the water to the oil phase. The ratio of mass transfer and oxidation reaction was determined by the Hatta-number and revealed a slow, quasi homogeneous reaction of ozone with PAH inside the oil droplets. Because the ozone gas concentration had no influence under the optimized conditions, the selective PAH-ozonation could be described microkinetically by a direct ozone reaction of pseudo-first order regarding PAH-concentrations. The determined PAH mean reaction rate constants of 1.02 min(-1) in oil/water-emulsions are in the upper range as found for PAH dissolved in water. These results give a new insight into the ozonation in the three-phase systems and into the treatment of highly condensed, hardly biodegradable PAH.