Soft Robotic Jellyfish: Design Optimization

By Andrew Haselton
Slide 1: Title slide reading Soft Robotic Jellyfish: Design Optimization, with author and lab information and a photo of a jellyfish robot next to a real jellyfish.

Slide-1

Soft Robotic Jellyfish: Design Optimization

Andrew Haselton

The University of Alabama

Dr. Erik D. Engeberg

BioRobotics Lab

This work was supported through the NSF REU Site in Sensing and Smart Systems, funded through NSF Award CNS-2447437.

Left image: a soft robotic jellyfish, colored white and gray, hovering near rocks and coral in an underwater cave-like setting with light streaming in from above.

Right image: a real orange sea nettle jellyfish with a domed bell and long trailing tentacles, photographed against a deep blue background.

Bottom right logo: Florida Atlantic University, I-SENSE: The Institute for Smarter Cities, Spaces, and Health, shown with an owl icon.

Slide 2: Background and Motivation, describing the advantages of soft robots near coral reefs and the inefficiency of previous jellyfish designs, with photos of a soft robot near coral and a real jellyfish.

Slide-2

Background and Motivation

  • Soft robots have a distinct advantage operating around fragile marine structures such as coral reefs
  • Previous iterations of the jellyfish design were able to navigate, but were inefficient in their motion, presenting opportunity for improvement and moving closer to emulating real jellyfish

Left image: a white soft robotic jellyfish positioned among rocks and coral in a dim underwater cave, with light entering from an opening above.

Right image: an orange sea nettle jellyfish with long tentacles swimming against a bright blue background.

Slide 3: Objectives and Challenges, listing goals to improve propulsion and optimize actuation, alongside challenges with molded components and the initial bell design, with photos of jellyfish and robot actuator parts.

Slide-3

Objectives

  • Improve jellyfish design to achieve greater propulsion
  • Optimize actuation pattern for propulsion
  • Evaluate the impact a bell can have on propulsion

Challenges

  • Molded components take significant time to produce, limiting the ability to iterate
  • The initial bell design proved to be difficult for the actuators to manipulate

Left image: several pink and white jellyfish with long trailing tentacles swimming in blue water.

Middle image: two gray ribbed pneumatic actuator components lying on a cloth surface.

Right image: an assembled white robotic jellyfish frame showing multiple wedge-shaped bell segments and internal actuator components.

Slide 4: Design Improvements, describing reoriented actuators, improved actuator retention, and an added bell, with a photo of the green robotic jellyfish and a CAD rendering of the bell assembly.

Slide-4

Design Improvements

  • Reoriented actuators
  • Improved actuator retention to ensure actuators stay in place during collisions
  • Added a bell to increase the effective surface area of the actuators

Left image: a green soft robotic jellyfish with a domed top and ribbed actuator legs, resting near underwater plants.

Right image: a CAD rendering of the jellyfish bell assembly, showing a clear domed top, internal support frame, and curved bell panels with attached actuators.

Slide 5: Bell Concepts, showing three CAD renderings of candidate bell designs labeled Single-Piece Ecoflex Bell, Nine-Piece Hinged Bell, and Three-Piece Printed Skeleton Ecoflex Bell.

Slide-5

Bell Concepts

Three CAD renderings of candidate jellyfish bell designs are shown side by side.

Left image, captioned "Single-Piece Ecoflex Bell": a smooth, single continuous domed bell shape with a translucent outer covering over a ribbed internal actuator structure.

Middle image, captioned "Nine-Piece Hinged Bell": a bell made of nine hinged rigid segments arranged around a central frame, giving it a faceted, cylindrical appearance.

Right image, captioned "Three-Piece Printed Skeleton Ecoflex Bell": a bell with a clear domed top and three flexible printed skeleton panels covered in a soft material, flaring outward at the base.

Slide 6: Bell Fabrication, showing three close-up photos of a fabricated silicone bell panel with red support lines, in different stages of finishing.

Slide-6

Bell Fabrication

Three close-up photographs show a single flexible bell panel at different stages of fabrication, each with red reinforcement lines running vertically along the panel.

Left image: a black bell panel with red support lines, showing a smooth curved surface.

Middle image: a black bell panel with visible surface texture and residue from the molding or coating process.

Right image: a lighter gray/translucent version of the same bell panel with red support lines, showing a cleaner finished surface.

Slide 7: Test Setup, showing pump control and load cell voltage plots, an electronics enclosure, a circuit board and signal diagram for the data acquisition system, and a photo of the jellyfish robot submerged in a test tank.

Slide-7

Test Setup

Top left chart, titled "Pump Control": an on/off square wave plotted against time from 60 to 120 seconds, showing the pump repeatedly switching between 0 and 5.

Below it, titled "Load Cell Reading": a voltage plot ranging from about 22.4 to 23 volts over the same time period, showing a repeating oscillating pattern synchronized with the pump control signal.

Top middle image: a black electronics enclosure with three yellow wire connectors and a blue terminal block on top.

Bottom left image: a small green circuit board (PCB) with soldered components and red and black wires attached.

Diagram: a block diagram of the data acquisition and control system. An "Actuator Control Signal" (shown as a square wave) feeds into an "Analog Output" block labeled "National Instruments PCI-6221 [auto]". An "Analog Input" block feeds into a "Low-Pass Filter" labeled "National Instruments PCI-6221 [auto]", which splits into "Unfiltered Load Cell" and "Filtered Load Cell" signals, both feeding into a data logging block alongside the actuator control signal.

Right image: a large cylindrical clear water tank on a table, with a red mounting fixture at the top holding wires that extend down to a pink and translucent jellyfish robot with fanned bell segments submerged in the water. Small dark sensor markers are attached around the base of the bell.

Slide 8: Full-frame photo of the soft robotic jellyfish submerged in the cylindrical test tank, with its bell segments extended and sensor markers visible along the base.

Slide-8

Test setup photo (no slide title present on this page)

A full-frame photograph of the jellyfish robot in its cylindrical test tank. The robot has a pink and translucent bell with segmented panels extending outward, small dark sensor markers spaced along the bottom edge of the bell, and a red mounting fixture with wires visible above the water surface. A whiteboard with handwritten notes is visible in the background.

Slide 9: Testing Parameters, describing the inter-period interval and pulse width ranges tested, with a signal diagram and a table marking which combinations were tested.

Slide-9

Testing Parameters

  • Testing a combination of inter-period interval (IPI) and pulse width (PW) to find the optimal actuation pattern
  • IPI range from 2s to 7s
  • PW range from 1s to 2.6s

Diagram: a square wave signal with "Inter-Period Interval (IPI)" labeling the time from the start of one pulse to the start of the next, and "Pulse Width (PW)" labeling the duration each pulse stays on.

Tested combinations of Inter-Period Interval (IPI) in seconds and Pulse Width (PW) in seconds. An "x" marks a tested combination.
Pulse Width (PW) (s) IPI = 2 IPI = 3.5 IPI = 5 IPI = 6 IPI = 7
1 x x x
1.4 x x x
1.7 x x x
2 x x x
2.3 x x x
2.6 x x x
Slide 10: Baseline Result, describing net negative thrust for the jellyfish with no bell, with pump control and load cell reading charts over time.

Slide-10

Baseline Result

  • Jellyfish with no bell
  • Produces net negative (backwards) thrust
  • Results evaluated by integrating the force with respect to time, and subtracting a baseline jellyfish weight

Top chart, titled "Pump Control": an on/off square wave plotted from 30 to 60 seconds, with "Inter-Period Interval (IPI)" marking the spacing between pulse starts and "Pulse Width (PW)" marking each pulse's duration.

Bottom chart, titled "Load Cell Reading": voltage plotted from about 22.3 to 22.7 volts over the same time range, oscillating with each pump pulse. A downward red arrow labeled "Positive Thrust" points down the left side of the chart, indicating that downward voltage deflections correspond to positive thrust and the trace shows the reading dipping below baseline more than it rises above it, consistent with net negative thrust.

Slide 11: Improved Result, describing positive propulsion achieved with a three-piece bell, with an average thrust table and pump control and load cell reading charts.

Slide-11

Improved Result

  • Three-piece bell
  • Positive propulsion
  • Maximum propulsion achieved at 6s IPI, 2s PW
Average Thrust by Inter-Period Interval (IPI) in seconds and Pulse Width (PW) in seconds.
Pulse Width (PW) (s) IPI = 2 IPI = 3.5 IPI = 5 IPI = 6 IPI = 7
1 -0.0038 -0.0083 0.0013
1.4 0 0 0.0039
1.7 0.0083 0.0132 0.009
2 0.0217 0.0149 0.0251
2.3 0.0112 0.0161 0.0172
2.6 0.0017 0.0057 0.0084

Top chart, titled "Pump Control": an on/off square wave plotted from 30 to 60 seconds, with "Inter-Period Interval (IPI)" marking the spacing between pulse starts and "Pulse Width (PW)" marking each pulse's duration.

Bottom chart, titled "Load Cell Reading": voltage plotted from about 22.4 to 23.2 volts over the same time range, oscillating with each pump pulse. A downward red arrow labeled "Positive Thrust" points down the left side of the chart. Unlike the baseline result, the trace shows the reading rising further above baseline than it dips below, consistent with net positive thrust.

Slide 12: Side-by-side photo and CAD rendering of the finished jellyfish robot with its three-piece bell and clear domed top.

Slide-12

Final jellyfish design (no slide title present on this page)

Left image: a photograph of the assembled jellyfish robot, showing a clear domed top with a red mounting ring, a soft white bell with red reinforcement lines and a three-piece split, and dark sensor markers along the bell's lower edge.

Right image: a CAD rendering of the same jellyfish assembly, showing the clear dome, internal support frame, and translucent bell panels with attached ribbed actuators.

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