Design and Experimental Research on a Bionic Robot Fish with Tri-Dimensional Soft Pectoral Fins Inspired by Cownose Ray

Abstract

Bionic propulsion has advantages over traditional blade propellers, such as efficiency and noise control. Existing research on ray-inspired robot fish has mainly focused on a single type of pectoral fin as bionic propeller, which only performed well in terms of pure speed or maneuverability. Rarely has the performance of different fin types been compared on the same platform to find an optimal solution. In this paper, a modularized robot fish with high-fidelity biomimetic pectoral fins and novel multi-DOF propelling mechanism is presented. A kinematic model of the pectoral fin based on motion analysis of a cownose ray is introduced as guidance for the propelling mechanism design. A high-fidelity parametric geo-model is established and evaluated based on statistical data. The design and fabrication process of the 3D soft bionic fins, as well as the robot platform, is also elaborated. Through experiments comparing the performance of different fin types constructed with different materials and approaches, it was found that the new soft fins made of silicon rubber have better performance than traditional fins constructed with a flexible inner skeleton and a permeable outer skin as a result of better 3D profile preservation and hydrodynamic force interaction. The robot ray prototype also acquires a better combination of high speed and maneuverability compared to results of previous research.

Design and Hydrodynamic Experiment Research on Novel Biomimetic Pectoral Fins of a Ray-Inspired Robotic Fish

“…Several buoyancy bars (black dashed line) are attached to the upper and lower surface of the central module and actuation modules, adjusting the buoyancy and weight center to keep the fish balanced in the water. The geometry outline of the fish closely resembles the 3D profile of real cownose rays, and most parts that would interact with water, including the pectoral fins, the head and tail module, the buoyancy bars on the fish back and belly, were either 3D-printed directly or cast in a 3D-printed mold, based on the parametric geo model established in our previous research [33], utilizing bionic morphology to achieve better hydrodynamic performance.…”

Three-Dimensional Numerical Study of Hydrodynamic Interactions between Pectoral Fins and the Body of Aquatic Organisms

“…The pectoral fins contribute to propulsion velocity and pectoral fin vortices reduce drag on the body [ 14 , 15 ]. Recently, the effect of pectoral fin flexibility on swimming was reported [ 16 , 17 , 18 , 19 ], and the pectoral fin is expected to improve the propulsive performance of aquatic organisms.…”

A Bioinspired Cownose Ray Robot for Seabed Exploration

“…The Biomimetic Cownose Ray [ 28 ] and the Bionic Manta Ray Robot [ 29 ] have fins composed of flexible silicone ribs mounted on a flexible shaft and covered by an elastic skin; conversely, the Aqua Ray [ 30 ] and the Manta Ray AUV [ 31 ] actuate the fins with Bionic Fluidic Muscles allowing a large amplitude fin deflection. Another biomimetic robot exploiting this strategy to reproduce the fin deformation is the Bionic Robot Fish, which reproduces the fin shape very accurately and uses an articulated mechanism composed of sliding rods and spherical joints to achieve a flapping and pitching movement [ 32 ]. A quite similar mechanism is adopted by the Bionic Pectoral Fin, which deforms producing both a chordwise and a spanwise wave [ 33 ].…”