Abstract
In this paper, an undulating soft fin is proposed for surge motions of an underwater robot inspired from the knife fish. The design, fabrication, and the control approach of the underwater robot are presented. The body length of the robot is 16 cm, and the fin length is 10 cm. A flapper mechanism which connects the servo motor and the soft fin excites oscillatory motions at the leading edge of the soft fin. The width of the fin along with the frequency and amplitude of the oscillatory flapping motion were varied to study their effects on free-swimming speed. As the width of the soft fin increases, the swimming speed increases. There exists an optimal frequency where a maximum speed is found. A maximum swimming speed of 0.625 BL/s (body lengths per second) is achieved for the considered range of parameters.