FSI modeling of frog inspired soft robot embedded with ALD encapsulated flex sensor for underwater synchronous swim

Abstract

The outstanding swim characteristics of the frog have inspired the development of artificial robotic swimmer, featuring synchronous swim capabilities, which could be of significant engineering interest in underwater applications. The Underwater synchronous swim is challenging because drag on the oars increases as the square of their speed. In frogs, as leg muscles shorten faster, the force capacity falls and drag force increases. In this paper, key features of frog's synchronous swim are reproduced by running 2D simulations which fully exploit the Fluid-Structure Interaction interface of COMSOL. Velocity, displacement, lift and drag forces in 2D space are studied. Unlike previous FSI underwater robotics studies in which much efforts are put on fluid dynamics, here muscles contraction is simulated by using the notion of pre-strain, emphasizing the kinematical role of muscle and the generation of movement. Based on these parameters, a soft frog robot embedded with shape memory alloy is fabricated using multilayer 3D printing technology. Flex Sensor encapsulated with Atomic Layer Deposition (ALD) is included in the limbs of soft frog robot to read the angle in real time. A proper synchronous movement of a frog-like body is reproduced by defining the pattern of muscles activation.