A Novel Multiple Synchronous Compliant and Passive Propeller Inspired by Loons for Swimming Robot

Animals living around water and marine environments have undergone a long evolutionary process and have developed a variety of propellers to enable rapid movement through the water. Loons, a kind of diving birds, use deformable, propulsion-generating feet to move through highly viscous fluid environments, and rely on the strong propulsion generated by the feet of this structure to enable them to dive to 70 meters and hunt fish in the water. Inspired by loons, a novel propeller for swimming robot was designed. A linkage with non-linear compliant oscillatory paddles mimicking loon's propelling mechanics, for thrust-efficient and agile locomotion, was firstly proposed. Arming to greater thrust and miniaturization, the method connecting linkage and the paddles is proposed which enables all the paddles oscillator synchronously to produce more thrust in the power stroke. Meanwhile, each compliant paddle, featured one-sided jointed limits, could create asymmetric gait cycle that avoids greater resistance in the recovery stroke. Furthermore, to analyze and evaluate the movement as well as the deformation and propelling force, the blade element theory was utilized to describe the dynamic model of the proposed propellers. Finally, experiments were carried out to verify the design and dynamic model. Overall, this paper offers a feasible and pragmatic design for biomimetic robot with multiple propellers synchronous propelling.