Biomimetic Design of a Soft Robotic Fish
for High Speed Locomotion
Sander C. van den Berg , Rob B. N. Scharff , Zolt´ an Rus´ ak , and Jun
Wu
(B)
Department of Sustainable Design Engineering, Delft University of Technology,
Landbergstraat 15, 2628 CE Delft, The Netherlands
j.wu-1@tudelft.nl
Abstract. We present a novel DC motor driven soft robotic fish which is
optimized for speed and efficiency based on experimental, numerical and
theoretical investigation into oscillating propulsion. Our system achieves
speeds up to 0.85 m/s, outperforming the previously reported fastest
free swimming soft robotic fish by a significant margin of 27%. A simple
and effective wire-driven active body and passive compliant body are
used to mimic highly efficient thunniform swimming. The efficient DC
motor to drive the system decreases internal losses compared to other
soft robotic oscillating propulsion systems which are driven by one or
multiple servo motors. The DC motor driven design allows for swimming
at higher frequencies. The current design has been tested up to a tailbeat
frequency of 5.5 Hz, and can potentially reach much higher frequencies.
Keywords: Soft robotic fish · Oscillating propulsion · Marine
robotics · Biomimetics
1 Introduction
Minimal disruption to the marine environment is an important requirement
for the design of underwater vehicles for closeup observations of marine life,
(deep) sea exploration, mining, and pipeline inspection. Robotic fish using oscillating soft tails have advantages compared to underwater vehicles that use rotary
propulsion. Rotary propulsion typically operates at a relatively high frequency.
This creates highly disturbing vibrations in the water and actively sucks in
objects and wildlife into the propeller. In contrast, oscillating propulsion uses
lower frequencies and a compliant tail that pushes obstacles away rather than
entangling them. Moreover, oscillating propulsion has the potential to be more
efficient than rotary propulsion. This is due to the harvesting of energy from
the turbulence at the wake of the vessel’s body and the absence of energy losses
due to rotation of the water flow as seen in rotary propulsion. Small propellers
used to drive underwater vehicles typically do not produce efficiencies above 40%
[13], where oscillating motion has shown efficiencies of up to 87% in lab experiments [2]. The difference in efficiency becomes especially large at great depths,
c
Springer Nature Switzerland AG 2020
V. Vouloutsi et al. (Eds.): Living Machines 2020, LNAI 12413, pp. 366–377, 2020.
https://doi.org/10.1007/978-3-030-64313-3_35
for High Speed Locomotion
Sander C. van den Berg , Rob B. N. Scharff , Zolt´ an Rus´ ak , and Jun
Wu
(B)
Department of Sustainable Design Engineering, Delft University of Technology,
Landbergstraat 15, 2628 CE Delft, The Netherlands
j.wu-1@tudelft.nl
Abstract. We present a novel DC motor driven soft robotic fish which is
optimized for speed and efficiency based on experimental, numerical and
theoretical investigation into oscillating propulsion. Our system achieves
speeds up to 0.85 m/s, outperforming the previously reported fastest
free swimming soft robotic fish by a significant margin of 27%. A simple
and effective wire-driven active body and passive compliant body are
used to mimic highly efficient thunniform swimming. The efficient DC
motor to drive the system decreases internal losses compared to other
soft robotic oscillating propulsion systems which are driven by one or
multiple servo motors. The DC motor driven design allows for swimming
at higher frequencies. The current design has been tested up to a tailbeat
frequency of 5.5 Hz, and can potentially reach much higher frequencies.
Keywords: Soft robotic fish · Oscillating propulsion · Marine
robotics · Biomimetics
1 Introduction
Minimal disruption to the marine environment is an important requirement
for the design of underwater vehicles for closeup observations of marine life,
(deep) sea exploration, mining, and pipeline inspection. Robotic fish using oscillating soft tails have advantages compared to underwater vehicles that use rotary
propulsion. Rotary propulsion typically operates at a relatively high frequency.
This creates highly disturbing vibrations in the water and actively sucks in
objects and wildlife into the propeller. In contrast, oscillating propulsion uses
lower frequencies and a compliant tail that pushes obstacles away rather than
entangling them. Moreover, oscillating propulsion has the potential to be more
efficient than rotary propulsion. This is due to the harvesting of energy from
the turbulence at the wake of the vessel’s body and the absence of energy losses
due to rotation of the water flow as seen in rotary propulsion. Small propellers
used to drive underwater vehicles typically do not produce efficiencies above 40%
[13], where oscillating motion has shown efficiencies of up to 87% in lab experiments [2]. The difference in efficiency becomes especially large at great depths,
c
Springer Nature Switzerland AG 2020
V. Vouloutsi et al. (Eds.): Living Machines 2020, LNAI 12413, pp. 366–377, 2020.
https://doi.org/10.1007/978-3-030-64313-3_35