An Agile Robotic Penguin Driven by Submersible Geared　Servomotors: Various Maneuvers by Active Feathering of the Wings

This study introduces an agile robotic penguin featuring a pair of 2-degrees of freedom (DoF) wing mechanisms. Each wing can independently control flapping and feathering motions with two in-house submersible geared servomotors through a differential gear mechanism. Notably, our mechanism allows unrestricted feathering beyond 360°. Since feathering directly changes the wing’s angle of attack (AoA), the hydrodynamic forces can be significantly adjusted to achieve agile maneuvers. This paper demonstrates various maneuvers, including rapid acceleration, hard braking, rolling, pitching, and yawing, achieved solely by changing the feathering motion of both wings. Our robotic penguin reached a maximum forward speed of 1.8 m/s, comparable to the foraging speed of real penguins. The average roll, pitch, and yaw rates were 363°/s, 75°/s, and 92°/s, respectively. This robot serves as a model for the biological study of maneuverability in real penguins and the engineering exploration of bioinspired agile underwater robots.