Steering-plane motion control for an underwater robot with a pair of undulatory fin propulsors

This paper presents the development, control, and experimental evaluation of a bio-inspired underwater vehicle that employs for propulsion a pair of lateral undulatory fins. Each fin is comprised of three actuated fin rays, interconnected by a membrane-like flexible surface. The rays' motion profile is produced via two coupled Central Pattern Generator networks, and a simple fluid drag model is used to estimate the thrust generated by the fins. Closed-loop strategies are developed for steering-plane motion control of the vehicle, involving forward/turning swimming and in-place rotations, with feedback provided by an on-board AHRS sensor. A series of experiments are conducted to assess the validity of the computational models, the efficacy of the proposed controllers, as well as the effect of the various kinematic parameters of the fin undulations on the generated thrust and the robot's swimming performance.