AUVAC

Silicon Swimmers

Taking advantage of thousands of years of evolution, researchers are working to perfect new underwater robots modeled after fish. Michael Philen, assistant professor of Aerospace and Ocean Engineering, assembled a research team that spans disciplines and universities to study the behavior and physiology of fish. With a $1.9 million grant from the National Science Foundation, the artificial fish they are developing could lead to underwater robots that can move far more efficiently than current propeller technology.

Fish can swim with a hydrodynamic efficiency of up to 90 percent, while modern propeller technology can be much less than this, according to Philen. Fish sense their environment and take advantage of this data to precisely adjust their complex muscular system and fins for maximum efficiency. Philen explains that “the hair-like neuromasts along a fish’s body allows a fish to sense the smallest changes in the fluid. This allows a fish to adjust its swimming to the water conditions and perform complicated maneuvers, such as schooling and escape.”

In order to replicate nature, such a sophisticated robotic fish requires novel sensors, actuators, materials, and control algorithms. “We want to use what we’ve learned from fish to develop artificial muscles and sensors for distributed sensing and actuation,” says Philen. The sensors will supply the robot with the data it needs, and the artificial muscles will allow it to act on this data.

A Mission Oriented Metric to Assess the Benefits of Biologically Inspired Propulsion

In this study, we quantify the potential mission specific benefits of biomimetic propulsion as a function of environmental conditions and operational requirements for a small unmanned underwater vehicle (UUV) mission. The benchmark mission requires the UUV to persist in shallow water for 24hr within a specified radius around the desired station, preceded and followed by a 40km transit

The achievable time on station for the nominal vehicle using biologically inspired propulsion is compared to that of the same vehicle using currently available thrusters. The comparison is carried out across a range of sea-states, with varying requirements for station keeping precision, and with a range of assumptions about the performance improvements provided by biomimetic propulsion. The expected magnitude and frequency of wave disturbances in shallow water are generated using U.S. Army Corps of Engineers guidelines for harbor design and construction.

If biomimetic propulsors can deliver on the promise of significantly improved effectiveness in generating low speed maneuvering forces, fin propelled vehicle can perform a high precision 24 hour station keeping mission in 3x higher waves than the thruster propelled vehicle. In rough conditions, the fin propelled vehicle can perform the mission with 10x higher precision.

Prototypical Robotic Fish with Swimming Locomotive Configuration in Fluid Environment

Abstract

Aquatic animal has always inspired many researchers’ interest to develop such living creations’ behavioral robots. Numbers of animal-liked aquatic robots have been invented in the past; however, very few works involved the study of full behavioral movement of these aquatic animals. This paper presents a study and design of a robotic fish that imitate natural aquatic animals’ forms of locomotion by focusing on the apparatus of swimming performances. The main research focus is the behavioral movement of the propulsion and maneuvering of a robotic fish in a fluid environment. The robot could dynamically generate a series of behavior selection network to form the operational plan, avoiding obstacle as well as fish-liked maneuver; forward, backward and turning. This robot differs from other research that not only uses the tail peduncle to propel its movement but also use pectoral fin in stabilizing and maneuvering. The proposed paradigm has been implemented to develop a prototypical robotic fish. The experiments also illustrate the conventionality, and the robustness of such a fish-robot framework.

Towards Amphibious Robots: Asymmetric Flapping Foil Motion Underwater Produces Large Thrust Efficiently

The development of amphibious robots requires actuation that enables them to crawl as well as swim; sea turtles
are excellent examples of amphibious functionality, that can serve as the biomimetic model for the development of amphibious robots.

In this paper we have implemented the observed swimming kinematics of Myrtle, a green sea turtle Chelonia Mydas residing in the Giant Ocean Tank of the New England Aquarium, on the 1.5-meter long biomimetic vehicle Finnegan the RoboTurtle. It is shown that these kinematics result in outstanding performance in (a) rapid pitching, and (b) rapid level turning. The turning radius for the rigid hull vehicle is 0.8 body lengths, a remarkable improvement in turning ability for a rigid hull vehicle.

Still Finnegan’s performance lags the live turtle’s performance by about 20%. Careful observations have shown that turtles employ a fin motion in-line with the direction of locomotion; this degree of freedom was not available to the Finnegan fins, as presently designed. Experimental tests on a flapping fin equipped with this third degree of freedom have shown that the in-line motion enhances the fin’s performance.

This hydrodynamic result is doubly beneficial to an amphibious robot, because it allows for further enhancements in the hydrodynamic function of fins, while the in-line motion allows the same fins to be used for crawling on land.