Guns, Jellyfish, and SteelWhy we should mimic jellyfish for efficient underwater

propulsion

Cyro – biomimic jellyfish robot

Guns? I thought this was bioE!

Why does a gun recoil?How is a submarine propelled?

How does a jellyfish propel itself?

(Naïve?) Propulsion Model

j-u

Time = t Time = t+Dt

u

MV

u+Du

M - Dm

V-DV

Model v. ExperimentLittle jellyfish (prolates)

Big jellyfish (oblates)

Big !!!D

Vortex complexes Increase Efficiency

Biomimetic Robot Design

• Features to replicate?• How to do this simply?

• Bell material properties: buoyancy, elasticity• Bell geometry/deformation• Muscles/Actuation

Hard body vs. soft-body

Finite degrees of freedom (DOF) Infinite degrees of freedom (DOF)

Action and Reaction: SMAsShape Memory Alloys (SMA)

Stress, strain and heating

Crystal structure phase change

Temperature induced phase change:

Martensite: soft, plastic, easily deformable state

Austenite: much harder material, rigid/difficult to deform.

Reaction: Spring steel and elastomerSMA changes length

metal does not

3-D printed mold: Integrating actuators

The devil in the detailsNo-flaps Flaps

Computer control: Feedback

SMA contracts

Changing resistance

Monitored by computerAdjusts current flow through SMA

Mimic vs. Nature

Up, up, and away

Small modifications go a long way!

Flaps and segments lead to large increased in thrust

ReferencesJellyfish Propulsion Mechanisms

S. Colin and J. Costello. Morphology, swimming performance and propulsive mode of six co-occuring hydromedusae. J. Exp Biol. 205 (2002) 427-437.

J. Dabiri et al. Flow patterns generated by oblate medusan jellyfish: field measurements and laboratory analyses. J. Exp Biol. 208 (2005) 1257-1265

Bioinspired Jellyfish Robot (Robojelly)

A. Villanueva et al. A biomimetic robotic jellyfish (Robojelly) actuated by shape memory alloy composite actuators. Bioinsp. Biomim 6 (2011) 036004

A. Villanueva et al. A bio-inspired shape memory alloy composite (BISMAC) actuator. Smart Mater. Struct. 19 (2010) 025013