Soft Fish

Autonomous Soft Robotic Fish

A soft fish tail replaces a complex multi-link rigid fish body for biomimetic locomotion. This work presents an autonomous soft-bodied robotic fish that is hydraulically actuated and capable of sustained swimming in three dimensions. A new closed-circuit drive system that uses water as a transmission fluid is used to actuate the soft body. Circulation of water through internal body channels provides control over the fish’s caudal fin propulsion and yaw motion. ¬†A new fabrication technique for the soft body is described, which allows for arbitrary internal fluidic channels, enabling a wide-range of continuous body deformations. ¬†Furthermore, dynamic diving capabilities are introduced through pectoral fins as dive planes. These innovations enable prolonged fish-like locomotion in three dimensions.

  • [PDF] [DOI] R. K. Katzschmann, A. D. Marchese, and D. Rus, “Hydraulic Autonomous Soft Robotic Fish for 3D Swimming,” in 2014 international symposium on experimental robotics (iser 2014), Marrakech, Morocco, 2014, pp. 405-420.
    [Bibtex]
    @inproceedings{katzschmann2014hydraulic,
    abstract = {This work presents an autonomous soft-bodied robotic fish that is hydraulically actuated and capable of sustained swimming in three dimensions. The design of a fish-like soft body has been extended to deform under hydraulic instead of pneumatic power. Moreover, a new closed-circuit drive system that uses water as a transmission fluid is used to actuate the soft body. Circulation of water through internal body channels provides control over the fish's caudal fin propulsion and yaw motion. A new fabrication technique for the soft body is described, which allows for arbitrary internal fluidic channels, enabling a wide-range of continuous body deformations. Furthermore, dynamic diving capabilities are introduced through pectoral fins as dive planes. These innovations enable prolonged fish-like locomotion in three dimensions.},
    address = {Marrakech, Morocco},
    author = {Katzschmann, Robert K and Marchese, Andrew D and Rus, Daniela},
    booktitle = {2014 International Symposium on Experimental Robotics (ISER 2014)},
    doi = {10.1007/978-3-319-23778-7_27},
    isbn = {9783319237787},
    issn = {1610742X},
    keywords = {Fluidic Elastomer Actuator,Fluidic elastomer actuator,Hydraulic,Hydraulic Actuation,Hydraulic actuation,Lost-Wax Silicone Casting,Lost-wax silicone casting,Robotic Fish,Robotic fish,Soft Actuator Fabrication,Soft Robotics,Soft actuator fabrication,Soft robotics,Underwater Locomotion,Underwater locomotion,fluidic elastomer actuator,hydraulic actuation,lost-wax fabrication,lost-wax silicone casting,motion,robotic fish,soft actuator fabrica-,soft actuator fabrication,soft robotics,tion,under-,water locomotion},
    mendeley-tags = {Hydraulic,lost-wax fabrication,soft robotics},
    number = {1122374},
    pages = {405--420},
    title = {{Hydraulic Autonomous Soft Robotic Fish for 3D Swimming}},
    volume = {109},
    year = {2014}
    }

Cyclic Actuation

Various pump mechanisms are presented for soft undulating actuation in water. Undulating structures are one of the most diverse and successful forms of locomotion in nature, both on ground and in water. This work presents a comparative study for actuation by undulation in water.
We focus on actuating a 1DOF systems with several mechanisms. A hydraulic pump attached to a soft body allows for water movement between two inner cavities, ultimately leading to a flexing actuation in a side-to-side manner. The effectiveness of six different, self-contained designs based on centrifugal pump, flexible impeller pump, external gear pump and rotating valves are compared. These hydraulic actuation systems combined with soft test bodies were then measured at a lower and higher oscillation frequency. The deflection characteristics of the soft body, the acoustic noise of the pump and the overall efficiency of the system are recorded. A brushless, centrifugal pump combined with a novel rotating valve performed at both test frequencies as the most efficient pump, producing sufficiently large cyclic body deflections along with the least acoustic noise among all pumps tested. An external gear pump design produced the largest body deflection, but consumes an order of magnitude more power and produced high noise levels. Further refinement remains on determining the suitable oscillation frequencies and inner cavity designs for optimal efficiency and movement.

  • [PDF] [DOI] R. K. Katzschmann, A. De Maille, D. L. Dorhout, and D. Rus, “Cyclic hydraulic actuation for soft robotic devices,” in Ieee international conference on intelligent robots and systems, Daejeon, 2016, pp. 3048-3055.
    [Bibtex]
    @inproceedings{katzschmann2016cyclic,
    abstract = {Undulating structures are one of the most diverse and successful forms of locomotion in nature, both on ground and in water. This paper presents a comparative study for actuation by undulation in water. We focus on actuating a 1DOF systems with several mechanisms. A hydraulic pump attached to a soft body allows for water movement between two inner cavities, ultimately leading to a flexing actuation in a side-to-side manner. The effectiveness of six different, self-contained designs based on centrifugal pump, flexible impeller pump, external gear pump and rotating valves are compared. These hydraulic actuation systems combined with soft test bodies were then measured at a lower and higher oscillation frequency. The deflection characteristics of the soft body, the acoustic noise of the pump and the overall efficiency of the system are recorded. A brushless, centrifugal pump combined with a novel rotating valve performed at both test frequencies as the most efficient pump, producing sufficiently large cyclic body deflections along with the least acoustic noise among all pumps tested. An external gear pump design produced the largest body deflection, but consumes an order of magnitude more power and produced high noise levels. Further refinement remains on determining the suitable oscillation frequencies and inner cavity designs for optimal efficiency and movement.},
    address = {Daejeon},
    author = {Katzschmann, Robert K. and De Maille, Austin and Dorhout, David L. and Rus, Daniela},
    booktitle = {IEEE International Conference on Intelligent Robots and Systems},
    doi = {10.1109/IROS.2016.7759472},
    isbn = {9781509037629},
    issn = {21530866},
    pages = {3048--3055},
    title = {{Cyclic hydraulic actuation for soft robotic devices}},
    volume = {2016-Novem},
    year = {2016}
    }

Remote Control

An end-to-end compact acoustic communication system designed for easy integration into remotely controlled underwater operations. The system supports up to 2048 commands that are encoded as 16 bit words. We present the design, hardware, and supporting algorithms for this system. A pulse-based FSK modulation scheme is presented, along with a method of demodulation requiring minimal processing power that leverages the Goertzel algorithm and dynamic peak detection. We packaged the system together with an intuitive user interface for remotely controlling an autonomous underwater vehicle. We evaluated this system in the pool and in the open ocean. We present the communication data collected during experiments using the system to control an underwater robot.

  • [PDF] [DOI] J. Delpreto, R. Katzschmann, R. Maccurdy, and D. Rus, “A compact acoustic communication module for remote control underwater,” in 10th acm international conference on underwater networks and systems, wuwnet 2015, 2015.
    [Bibtex]
    @inproceedings{delpreto2015compact,
    abstract = {This paper describes an end-to-end compact acoustic communication system designed for easy integration into remotely controlled underwater operations. The system supports up to 2048 commands that are encoded as 16 bit words. We present the design, hardware, and supporting algorithms for this system. A pulse-based FSK modulation scheme is presented, along with a method of demodulation requiring minimal processing power that leverages the Goertzel algorithm and dynamic peak detection. We packaged the system together with an intuitive user interface for remotely controlling an autonomous underwater vehicle. We evaluated this system in the pool and in the open ocean. We present the communication data collected during experiments using the system to control an underwater robot.},
    author = {Delpreto, J. and Katzschmann, R. and Maccurdy, R. and Rus, D.},
    booktitle = {10th ACM International Conference on Underwater Networks and Systems, WUWNet 2015},
    doi = {10.1145/2831296.2831337},
    isbn = {9781450340366},
    keywords = {Goertzel algorithm,Microcontroller,System integration,Underwater acoustic communication,Underwater low-bandwidth robot control},
    title = {{A compact acoustic communication module for remote control underwater}},
    year = {2015}
    }

Link to Soft Robotic Fish Project at DRL, CSAIL, MIT