Meeting Abstract

6.1  Thursday, Jan. 3  Locomotor Performance of Free-Swimming Robots Propelled by Biomimetic Tails MCARTHUR, G*; GUTIERREZ, A; ROSENBLUM, H; SAHKTAH, H; STICKLES, E; DOORLY, N; LONG, J; Vassar College; Vassar College; Vassar College; Vassar College; Vassar College; Vassar College; Vassar College gimcarthur@vassar.edu

Because they are simplified models of biological systems, free-swimming robots can be used to isolate and test the biomechanical function of morphological features that appear in fish. In this study, we adapted the surface-swimming Tadro robot platform to examine two features of fish axial skeletons: (1) the number of vertebrae and (2) the span of the caudal fin. From hydroelastic theory, we expect that the number of vertebrae and the span of the caudal fin should govern, because of their control of bending stiffness and thrust generation, respectively, much of the mechanical performance of the undulating tail. To test that prediction, we made and installed a variety of morphologically-variable tails in a Tadro. The biomimetic tails were constructed with vertebral columns bearing ring centra — which were glued onto a cross-linked hydrogel acting as a notochord — attached to a rigid flat plate serving as a caudal fin. We had the Tadro perform (1) constant-velocity swimming and (2) transient escape responses. Using high-speed videography and three-axis accelerometry, we correlated variation in swimming speed, peak acceleration, peak tail curvature, and tailbeat amplitude with variation in the two morphological features. To our surprise, neither number of vertebrae nor span of the caudal fin showed a strong correlation with speed or acceleration. One reason for this may be that caudal fins with larger spans, compared to those with smaller spans, tended to have reduced tailbeat amplitude, thus canceling out increases in thrust caused by the increased span.