Research ArticleBIOMIMETICS

Exploration of underwater life with an acoustically controlled soft robotic fish

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Science Robotics  21 Mar 2018:
Vol. 3, Issue 16, eaar3449
DOI: 10.1126/scirobotics.aar3449
  • Fig. 1 SoFi system overview.

    (Top, left to right) Soft robotic fish and diver interface module. (Bottom, left to right) Subcomponents of the system are the elastomer tail (cut view), external gear pump, BCU, two dive planes, control electronics including acoustic receiver, and fisheye camera.

  • Fig. 2 Underwater exploration.

    Fish trajectory exploring a coral reef. The snapshots of the fish are equally spaced in time by 2.6 s per representation.

  • Fig. 3 Quantitative ocean experiments.

    Clockwise from top left: Straight swimming, vertical diving, left turn, and right turn experiments of the robotic fish.

  • Fig. 4 Underwater observatory.

    (A) A diver using the acoustic communication modem to remotely control the robotic fish. (B) The fish exploring complex coral reef environments. (C) The robotic fish among marine life. (D) Pictures captured by the fish’s onboard camera.

  • Fig. 5 Closeup view of marine life.

    (Left) Onboard view filming several fish passing by the lens of SoFi. (Right) Photo taken by a diver from further behind, showing both the robotic fish and the observed biological fish.

  • Fig. 6 Signal flow within the system.

    The command flow from a human diver to the robot. The diver sends acoustic commands such as thrust, left/right, and up/down as well as camera modes from the transmitter within the diver interface module. The analog signal travels several meters underwater and is then amplified by the receiver and parsed by the microcontroller. The microcontroller adjusts the pump speed, the dive plane position, the BCU, and the mode of the camera.

  • Fig. 7 Soft tail, pump, and BCU.

    (Top) Two views of the soft fish tail in an actuated state (left) and custom external gear pump in an exploded view (right). (Bottom) One of two identical BCU modules in an exploded view.

  • Fig. 8 Acoustic communication.

    (Left) Exploded view of the diver interface module, containing the transmitter. (Right) Schematic view of the transmitter and receiver pipelines.

  • Table 1 Communication experiments.

    Cumulative results of the acoustic communication during four of the six dives, spanning 2 days and averaging about 40 active minutes per dive. Note that “steady commands” are commanded states that persisted for at least 1 s. Observations were made at an average depth of 8.1 m, a maximum depth of 18 m, a range between transmitter and receiver of 0 to 10 m, and a transmit acoustic power of 137.3 dB SPL re 1 μPa.

    Dive 3Dive 4Dive 5Dive 6
    Total commands obeyed673011193
    Total commands missed55624657
    Steady commands obeyed55267578
    Steady commands missed2531721
    Percent of steady
    commands obeyed
    68.8%45.6%91.5%78.8%
    Fish timeouts (reversions to
    neutral state)
    63348181
    Percent of dive spent
    timed out
    12.3%8.0%7.3%8.1%

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/3/16/eaar3449/DC1

    Materials and Methods

    Fig. S1. Wax core fabrication.

    Fig. S2. Tail fabrication.

    Fig. S3. External gear pump.

    Fig. S4. Buoyancy control system.

    Fig. S5. Additional buoyancy control experiments.

    Fig. S6. Acoustic reflections.

    Fig. S7. Motor’s broad spectrum noise.

    Fig. S8. Acoustic range tests.

    Fig. S9. Performance of tone detection algorithm.

    Fig. S10. Ocean communication tests.

    Table S1. Color measurements of exposed parts.

    Table S2. Dive summaries.

    Table S3. Tail strokes.

    Movie S1. Underwater experiments.

  • Supplementary Materials

    Supplementary Material for:

    Exploration of underwater life with an acoustically controlled soft robotic fish

    Robert K. Katzschmann,* Joseph DelPreto, Robert MacCurdy, Daniela Rus

    *Corresponding author. Email: rkk{at}csail.mit.edu

    Published 21 March 2018, Sci. Robot. 3, eaar3449 (2018)
    DOI: 10.1126/scirobotics.aar3449

    This PDF file includes:

    • Materials and Methods
    • Fig. S1. Wax core fabrication.
    • Fig. S2. Tail fabrication.
    • Fig. S3. External gear pump.
    • Fig. S4. Buoyancy control system.
    • Fig. S5. Additional buoyancy control experiments.
    • Fig. S6. Acoustic reflections.
    • Fig. S7. Motor’s broad spectrum noise.
    • Fig. S8. Acoustic range tests.
    • Fig. S9. Performance of tone detection algorithm.
    • Fig. S10. Ocean communication tests.
    • Table S1. Color measurements of exposed parts.
    • Table S2. Dive summaries.
    • Table S3. Tail strokes.
    • Legend for movie S1

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Underwater experiments.

    Files in this Data Supplement:

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