This article presents the design, fabrication, characterization of a soft biomimetic robotic frog based on multilayer structural design of Shape Memory Alloy (SMA) and ultraflexible material. The synchronous swimming motion of frog is achieved by dual thrust approach, utilizing four SMA (BMF 150) muscle wires. The frog robot is named as Exploratory Frog (EXPOG) and is fabricated using multiheaded 3D printing system. Whereas the body of the EXPOG is printed using polylactic acid, which is connected with functionally responsive limbs (50 mm length and 6mm thickness). The proposed kinematic model was simulated in COMSOL to verify the surface velocity and vortex generation in water using the frog’s strokes. We successfully performed the experiment to validate the swimming of EXPOG with that of real frog. Each limb consists of two muscles (SMA-1 and SMA-2). SMA-1 works as the main thrust creating unit, which is powered by 5V, 250 mA whereas SMA-2 creates back thrust force for antagonistic motion. Electrical and mechanical characterizations have been performed. Moreover, experimental data was further processed using TRACKER for angle, displacement, and velocity. The EXPOG can swim at different controllable frequencies (0.5 – 2 Hz) which enables it to swim at the speed up to 15 mm/s (0.3 BLS) in deep water (15 cm).
Journal: International Journal of Mechanical Science