Mathematical modeling and control of Biomimetic Autonomous Underwater Vehicle (BAUV) based on flapping propulsion.

Bioinspired underwater vehicles which mimic motion from flapping gait of marine fishes can benefit from the flight efficiency and silent maneuver in aquatic environments. However, there is a very limited amount of research which focuses on mapping the flapping fin propulsion to model the complete dynamics of the bioinspired robot. Multiple parameters like amplitude of motion, flapping frequency and initial angle of attack affect the overall motion dynamics. In this work, the propulsive thrust generated from the undulating fin structure is numerically investigated by computational fluid dynamics (CFD) study. Further, this non-linear thrust map is used to formulate the mathematical model of the proposed biomimetic autonomous underwater vehicle (BAUV). To validate the trajectory tracking performance of the proposed system in 2D planar maneuver, coupled dynamics of the underactuated vehicle (with one caudal, and two dorsal fins) is derived and hybrid control strategy is implemented. Trajectory tracking control of the proposed structure is also studied which is challenging because of the oscillatory motions of the fins. For a L-shaped trajectory of edge length 200m, the proposed BAUV with a span-length of 2.5 m is capable to render the desired trajectory with permissible error of 0.2 m, maximum flapping frequency of 0.6 Hz and dorsal fin deflection of 25 degrees which verify the accuracy of the proposed BAUV model.