Waves apply significant forces to small boats, in particular when such vessels are moving at a high speed in severe sea conditions. In addition, small highspeed boats run the risk of diving with the bow into the next wave crest during operations in the wavelengths and wave speeds that are typical for shallow water. In order to mitigate the issues of autonomous navigation in rough water, a hybrid controller called POSTMAN combines the concept of POS (point of sail) tack planning from the sailing domain with a standard PID (proportional- integral-derivative) controller that implements reliable target reaching for the motorized small boat control task.
This is an embedded, adaptive software controller that uses look-ahead sensing in a closed loop method to perform path planning for safer navigation in rough waters. State-of-the-art controllers for small boats are based on complex models of the vessel’s kinematics and dynamics. They enable the vessel to follow preplanned paths accurately and can theoretically control all of the small boat’s six degrees of freedom. However, the problems of bow diving and other undesirable incidents are not addressed, and it is questionable if a six- DOF controller with basically a single actuator is possible at all. POSTMAN builds an adaptive capability into the controller based on sensed wave characteristics.
This software will bring a much-needed capability to unmanned small boats moving at high speeds. Previously, this class of boat was limited to wave heights of less than one meter in the sea states in which it could operate. POSTMAN is a major advance in autonomous safety for small maritime craft.
This work was done by Terrance L. Huntsberger of Caltech and Felix Reinhart of the Research Institute for Cognition and Robotics for NASA’s Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Innovative Technology Assets Management
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
This Brief includes a Technical Support Package (TSP).
POSTMAN: Point of Sail Tacking for Maritime Autonomous Navigation (reference NPO-47986) is currently available for download from the TSP library.
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