Fig. 7: Batoid-robots mimic nature with high and low aspect ratio designs employing undulatory and oscillatory fin kinematics.
From: Ray-inspired robots: recent advances in actuation and control
a The width:length ratio of biological oscillatory and undulatory batoid rays show a clear division between swimming modes at W/L = 1.3528. Width is defined as the distance from fin tip to fin tip, and length is the distance between the tip of the leading edge of the ray to the trailing edge of the fin disc (excluding tails). The boundary at 1.35 is calculated by varying from the mean of each group (1.07 for undulatory and 1.73 for oscillatory) by the same number of standard deviations (standard deviation of 0.142 for undulatory and 0.192 for oscillatory). b The speed versus W/L ratio of various batoid-inspired robots shows distinct aspect ratio regimes for undulatory versus oscillatory locomotion. The 1.35 boundary seen in natural rays is shown, which also separates the approximate regimes for robot locomotion17,19,24,40,41,42,44,45,46,47,48,49,50,51,52,53,54,55,56,58,59,61,62,63,68,70,71,73,74,75,76,77,79,80,82,84,85,86,87,120,121,122,123,124.
