Bio-Inspired Actuation Control for Swimming Gait Transition using an Undulating Fin Robot

Many marine animals use undulating fins for navigation and performing fine maneuvering. The Black Ghost Knifefish achieves smooth gait transition from hovering to bi-directional longitudinal movement by shifting the colliding point of propagated sinusoidal waves emanating from opposing ends of a single undular fin. Inspired by the knifefish, in this work we explore a novel propulsive and directional control method in which a sigmoidal spatiotemporal pattern is applied to an elongated membrane affixed to a robotic vessel. We found that adjusting the curvature of the undulating fin in tandem with the point of collision of sinusoidal waves generated a net yawing torque. This allows for fine heading control and production of a controlled forward or backward thrust. The sigmoid actuation proved capable of full control of the robot's position and orientation during both station-keeping when subjected to external disturbances and speed variation during tracking and following a target.