ON A BIOMIMETIC VEHICLE WITH SKELETON SIMILAR TO THE SEA TURTLE

Abstract

The article studies the semi-active Nitinol (NiTi) control of a biomimetic vehicle
with a skeleton similar to the sea turtle. NiTi wires link two segments of adjacent vertebrae
of the vehicle's skeleton and generate the relative motion between two segments. By heating
and cooling the NiTi wires, two-way rotation of the vertebrae is generated, which causes the
shape of the vehicle to change. NiTi wires are inserted into elastic tubes containing water to
facilitate cooling through forced water circulation. The vehicle is capable of deforming and
taking different shapes to allow movement at controlled oscillation frequencies up to 1 Hz,
with a 1/2 Hz oscillation that produces large amplitudes of the skeletal motion. The
optimization of the motion trajectories of the sea turtle vehicle based on the minimum energy
criterion, led to a symmetric trajectory similar to the figure 8 with an attack angle of 12 °
during the descent and climb phases. The optimal trajectory is confirmed by the experimental
results obtained by Font et al. in 2011. The paper represents a part of the PhD thesis of
Luciana Majercsik [3].