RIGHTING OF CHINESE MITTEN CRABS (ERIOCHEIR SINENSIS) AND THEIR MODELS

Abstract

The usage of unmanned underwater vehicles for marine tasks is continuously growing and bioinspired stabilizing systems shall help them to gain and keep a stable position during work. Therefore the righting maneuver of E. sinensis has been studied. These crabs are able to perform a 180°-rotation with an angular velocity of 4.30 s−1 when falling underwater from a supine starting position. High-speed particle image velocimetry has shown, that propulsive forces with a peak of 0.021 ± 0.001 N were produced by the hind legs to initiate and stop the rotation. In a numerical multibody simulation a constant force of 0.009 N acting for 0.2 s leads to the same rotation. In order to prove this mechanism, it was implemented into a robotic system. Its mean density of 1.15 g/cm3 deviates not more than 4% from the biological and numerical models. It can complete a 180°-turn within 1.03 ± 0.12 s with a rotational velocity of up to 4.25 s−1.