376
S. C. van den Berg et al.
5 Conclusion
This work presented a biomimetic design of a soft robotic fish for high-speed
locomotion. During free swimming, the fish achieved a top speed of 0.85 m/s,
outperforming previously reported fastest free swimming soft robotic fish by a
significant margin of 27%. At higher tailbeat frequencies, the speed of the fish
increased, whereas the tailsweep length decreased due to a more sigmoid-like
tail shape resulting in a more optimal angle of attack. At a tailbeat frequency
above 2.33 Hz, the Strouhal number of the prototype with the large caudal
fin dropped below 0.4, which is an indicator of good efficiency. These results
confirm the theoretically predicted gain in efficiency due to the increased tailbeat
frequency and more sinusoidal waveform enabled by our novel propulsion system
design. The stiffness of the passive tail segment should be tuned to the tailbeat
frequency such that a sigmoid-like tail shape and optimal angle of attack is
achieved. Future work will focus on controlling the stiffness of the passive tail
segment dynamically in order to achieve efficient swimming at different speeds.
Although our propulsion mechanisms allows for a relatively easy implementation
of a steering mechanism, it has not been implemented in this prototype. This
will be part of future work as well. The design of the soft robotic fish will be
made available online.
References
1. y Alvarado, P.V., Youcef-Toumi, K.: Modeling and design methodology of an efficient underwater propulsion system. In: Robotics and Applications, pp. 161–166
(2003)
2. Anderson, J., Streitlien, K., Barrett, D., Triantafyllou, M.: Oscillating foils of high
propulsive efficiency. J. Fluid Mech. 360, 41–72 (1998)
3. Barrett, D., Triantafyllou, M., Yue, D., Grosenbaugh, M., Wolfgang, M.: Drag
reduction in fish-like locomotion. J. Fluid Mech. 392, 183–212 (1999)
4. Clapham, R.J., Hu, H.: iSplash: realizing fast carangiform swimming to outperform
a real fish. In: Du, R., Li, Z., Youcef-Toumi, K., Valdivia y Alvarado, P. (eds.)
Robot Fish. STME, pp. 193–218. Springer, Heidelberg (2015). https://doi.org/10.
1007/978-3-662-46870-8 7
5. Hover, F., Haugsdal, Ø., Triantafyllou, M.: Effect of angle of attack profiles in
flapping foil propulsion. J. Fluids Struct. 19(1), 37–47 (2004)
6. Katzschmann, R.K., DelPreto, J., MacCurdy, R., Rus, D.: Exploration of underwater life with an acoustically controlled soft robotic fish. Sci. Robot. 3(16), eaar3449
(2018)
7. Kermode, A.C.: Mechanics of Flight. Longman, London (1987)
8. Lighthill, M.J.: Aquatic animal propulsion of high hydromechanical efficiency. J.
Fluid Mech. 44(2), 265–301 (1970)
9. Lindsey, C.: 1 - form, function, and locomotory habits in fish. In: Hoar, W., Randall,
D. (eds.) Locomotion, Fish Physiology, vol. 7, pp. 1–100. Academic Press (1978)
10. Mazumdar, A., Alvarado, P.V.Y., Youcef-Toumi, K.: Maneuverability of a robotic
tuna with compliant body. In: 2008 IEEE International Conference on Robotics
and Automation, pp. 683–688. IEEE (2008)
S. C. van den Berg et al.
5 Conclusion
This work presented a biomimetic design of a soft robotic fish for high-speed
locomotion. During free swimming, the fish achieved a top speed of 0.85 m/s,
outperforming previously reported fastest free swimming soft robotic fish by a
significant margin of 27%. At higher tailbeat frequencies, the speed of the fish
increased, whereas the tailsweep length decreased due to a more sigmoid-like
tail shape resulting in a more optimal angle of attack. At a tailbeat frequency
above 2.33 Hz, the Strouhal number of the prototype with the large caudal
fin dropped below 0.4, which is an indicator of good efficiency. These results
confirm the theoretically predicted gain in efficiency due to the increased tailbeat
frequency and more sinusoidal waveform enabled by our novel propulsion system
design. The stiffness of the passive tail segment should be tuned to the tailbeat
frequency such that a sigmoid-like tail shape and optimal angle of attack is
achieved. Future work will focus on controlling the stiffness of the passive tail
segment dynamically in order to achieve efficient swimming at different speeds.
Although our propulsion mechanisms allows for a relatively easy implementation
of a steering mechanism, it has not been implemented in this prototype. This
will be part of future work as well. The design of the soft robotic fish will be
made available online.
References
1. y Alvarado, P.V., Youcef-Toumi, K.: Modeling and design methodology of an efficient underwater propulsion system. In: Robotics and Applications, pp. 161–166
(2003)
2. Anderson, J., Streitlien, K., Barrett, D., Triantafyllou, M.: Oscillating foils of high
propulsive efficiency. J. Fluid Mech. 360, 41–72 (1998)
3. Barrett, D., Triantafyllou, M., Yue, D., Grosenbaugh, M., Wolfgang, M.: Drag
reduction in fish-like locomotion. J. Fluid Mech. 392, 183–212 (1999)
4. Clapham, R.J., Hu, H.: iSplash: realizing fast carangiform swimming to outperform
a real fish. In: Du, R., Li, Z., Youcef-Toumi, K., Valdivia y Alvarado, P. (eds.)
Robot Fish. STME, pp. 193–218. Springer, Heidelberg (2015). https://doi.org/10.
1007/978-3-662-46870-8 7
5. Hover, F., Haugsdal, Ø., Triantafyllou, M.: Effect of angle of attack profiles in
flapping foil propulsion. J. Fluids Struct. 19(1), 37–47 (2004)
6. Katzschmann, R.K., DelPreto, J., MacCurdy, R., Rus, D.: Exploration of underwater life with an acoustically controlled soft robotic fish. Sci. Robot. 3(16), eaar3449
(2018)
7. Kermode, A.C.: Mechanics of Flight. Longman, London (1987)
8. Lighthill, M.J.: Aquatic animal propulsion of high hydromechanical efficiency. J.
Fluid Mech. 44(2), 265–301 (1970)
9. Lindsey, C.: 1 - form, function, and locomotory habits in fish. In: Hoar, W., Randall,
D. (eds.) Locomotion, Fish Physiology, vol. 7, pp. 1–100. Academic Press (1978)
10. Mazumdar, A., Alvarado, P.V.Y., Youcef-Toumi, K.: Maneuverability of a robotic
tuna with compliant body. In: 2008 IEEE International Conference on Robotics
and Automation, pp. 683–688. IEEE (2008)