Batoid Fishes: Inspiration for the Next Generation of Underwater Robots

Abstract

A B S T R A C TFor millions of years, aquatic species have utilized the principles of unsteady hydrodynamics for propulsion and maneuvering. They have evolved high-endurance swimming that can outperform current underwater vehicle technology in the areas of stealth, maneuverability and control authority. Batoid fishes, including the manta ray, Manta birostris, the cownose ray, Rhinoptera bonasus, and the Atlantic stingray, Dasyatis sabina, have been identified as a high-performing species due to their ability to migrate long distances, maneuver in spaces the size of their tip-to-tip wing span, produce enough thrust to leap out of the water, populate many underwater regions, and attain sustained swimming speeds of 2.8 m/s with low flapping/ undulating frequencies. These characteristics make batoid fishes an ideal platform to emulate in the design of a bio-inspired autonomous underwater vehicle. The enlarged pectoral fins of each ray undergoes complex motions that couple spanwise curvature with a chordwise traveling wave to produce thrust and to maneuver. Researchers are investigating these amazing species to understand the biological principles for locomotion. The continuum of swimming motions-from undulatory to oscillatory-demonstrates the range of capabilities, environments, and behaviors exhibited by these fishes. Direct comparisons between observed swimming motions and the underlying cartilage structure of the pectoral fin have been made. A simple yet powerful analytical model to describe the swimming motions of batoid fishes has been developed and is being used to quantify their hydrodynamic performance. This model is also being used as the design target for artificial pectoral fin design. Various strategies have been employed to replicate pectoral fin motion. Active tensegrity structures, electro-active polymers, and fluid muscles are three structure/actuator approaches that have successfully demonstrated pectoral-finlike motions. This paper explores these recent studies to understand the relationship between form and swimming function of batoid fishes and describes attempts to emulate their abilities in the next generation of bio-inspired underwater vehicles.

Hydrodynamic Performance of Aquatic Flapping: Efficiency of Underwater Flight in the Manta

“…The efficiency of an oscillating, flexible hydrofoil is increased by 20% with a small decrease in thrust, compared to a rigid propulsor executing similar movements [13]. Furthermore, the presence of a traveling wave moving in the chordwise direction can increase efficiency and enhance swimming speed [53,54].…”

“…There has been considerable interest recently in the development of bio-inspired autonomous underwater vehicles (BAUVs) [54,58,59]. Under certain conditions, the BAUV may outperform biological swimmers [59].…”

A fast Chebyshev method for simulating flexible-wing propulsion

“…Inspired by their agility, stealth, and efficiency [11,86,78], researchers have been working to integrate similar principles into new technologies, such as autonomous underwater vehicles, ornithopters, and micro-air vehicles [20,61,46,18,58,59,96,75] A distinguishing feature of natural locomotion is the use of flexible wings or fins. These appendages deform significantly when actuated, which can provide a number of performance benefits.…”

Launching the AquaMAV: bioinspired design for aerial–aquatic robotic platforms

“…Flapping propulsion has been demonstrated in many robots, and has many advantages, both in air [67] and in water [68]. Lock et al [25] used experimental data to develop a model for the eect of wing sizing and morphing on the power requirements in air and water of a guillemot inspired apping wing robot.…”

“…Bioinspired robots have been presented that can both y and move on land, either by jumping or by walking [15]. Other robots take cues from amphibious locomotion in nature and can move on land and in water [68].…”