RCUE Agile Underwater Vehicle Control
- Matthew Perkins
Agile Underwater Vehicle Control : Project Description
Background Conventional propeller driven autonomous underwater vehicles (AUVs) cannot operate in dynamic environments, near obstacles, or close to the bottom; they have high roll stability and low actuator authority, and use a decoupled linearized control approach which produces slow moving vehicles with poor agility. In an effort improve AUV agility, the U.S. Navy has funded the development of a number of oscillating foil driven AUVs. Oscillating foils are a class of biologically inspired thruster which can vector propulsion forces more rapidly -- and with higher authority -- than conventional propellers. Foil driven AUVs have the propulsion authority to perform aggressive maneuvers such as banked turns, rolls, and flips. However, since existing linearized AUV control approaches controllers assume small attitude angles and slow angular rotations, they cannot exploit these new vehicle capabilities.
Project Goals The purpose of the proposed effort is to develop and validate control algorithms for foil driven AUVs which take full advantage of their novel propulsion capabilities, enabling them to perform aggressive, large angle maneuvers. Target naval applications for agile vehicles include payload delivery, intelligence/ surveillance/reconnaissance (ISR) and mine counter-measures (MCM) in shallow waters and rivers.
Project Approach A vehicle performing 'large angle' maneuvers follows a trajectory in which the vehicle is rotated >10 degrees from level flight. Control of rigid body rotation at high angles is an inherently non-linear problem. We propose to use non-linear controllers that are formulated using the modified Rodrigues Parameters (rather than the conventional Euler angles or quaternions) to allow computationally tractable and intuitively accessible trajectory generation and trajectory following within the full rotational space available to agile vehicles. This approach has been used by Dr. Licht to demonstrate obstacle avoidance maneuvers using the MIT RoboTurtle AUV.
Simulation and experiment with two vehicles of opportunity will form the core of the effort. One of these vehicles is located at URI; the other is available through Dr. Beal, the NUWC Project Director. Transphibian, currently at URI, is a four finned, 20 kg AUV developed for shallow MCM operation. Razor, currently at NUWC, is a four fined 200kg AUV developed for hostile swimmer interdiction.
Expected Outcomes Dr. Licht's research group at URI will develop and experimental validate provably stable trajectory following controllers for agile underwater vehicles, operating at arbitrary attitude set points. Validation will include fielding of Transphibian and Razor in dynamic, cluttered riverine and near shore environments in Narragansett Bay and the Pettaquamscutt River.
RCUE was selected in January 2014 to join the Naval Engineering Education Center (NEEC), a consortium of educational institutions dedicated to improving recruiting into the U.S. Navy laboratories.
Funds from NEEC support undergraduate and graduate students in the lab working on "Agile Underwater Vehicle Control" in collaboration with engineers at the Newport branch of the Naval Underwater Warfare Center (NUWC - Newport)