Undulatory Swimming Performance Explored With a Biorobotic Fish and Measured by Soft Sensors and Particle Image Velocimetry

Abstract

Due to the difficulty of manipulating muscle activation in live, freely swimming fish, a thorough examination of the body kinematics, propulsive performance, and muscle activity patterns in fish during undulatory swimming motion has not been conducted. We propose to use soft robotic model animals as experimental platforms to address biomechanics questions and acquire understanding into subcarangiform fish swimming behavior. We extend previous research on a bio-inspired soft robotic fish equipped with two pneumatic actuators and soft strain sensors to investigate swimming performance in undulation frequencies between 0.3 and 0.7 Hz and flow rates ranging from 0 to 20 cms in a recirculating flow tank. We demonstrate the potential of eutectic gallium–indium (eGaIn) sensors to measure the lateral deflection of a robotic fish in real time, a controller that is able to keep a constant undulatory amplitude in varying flow conditions, as well as using Particle Image Velocimetry (PIV) to characterizing swimming performance across a range of flow speeds and give a qualitative measurement of thrust force exerted by the physical platform without the need of externally attached force sensors. A detailed wake structure was then analyzed with Dynamic Mode Decomposition (DMD) to highlight different wave modes present in the robot’s swimming motion and provide insights into the efficiency of the robotic swimmer. In the future, we anticipate 3D-PIV with DMD serving as a global framework for comparing the performance of diverse bio-inspired swimming robots against a variety of swimming animals.

Soft Underwater Swimming Robots Based on Artificial Muscle

“…In 2021, Schwab et al used two pneumatic actuators and a soft strain sensor to build a soft robotic fish platform that was used to explore undulatory locomotion parameters under different swimming and flow conditions. [64] This study provides insights into the swimming control strategy and propulsive force generation of rainbow trout (Figure 1b). In the same year, Cheng et al designed and fabricated a variable stiffness, pneumatic, soft biomimetic caudal fin, where each pneumatic actuator corresponded to a different tail fin ray (Figure 1c).…”

“…Reproduced with permission. [ 64 ] Copyright 2022. c) Pneumatic soft biomimetic caudal fin. Reproduced with permission.…”

“…used two pneumatic actuators and a soft strain sensor to build a soft robotic fish platform that was used to explore undulatory locomotion parameters under different swimming and flow conditions. [ 64 ] This study provides insights into the swimming control strategy and propulsive force generation of rainbow trout (Figure 1b). In the same year, Cheng et al.…”

“…b) Soft robotic fish with a soft actuator and sensor. Reproduced with permission [64]. Copyright 2022. c) Pneumatic soft biomimetic caudal fin.…”

Morphologically Adaptive Crash Landing on a Wall: Soft‐Bodied Models of Gliding Geckos with Varying Material Stiffnesses

“…The goal of bioinspired robotics is often twofold: understanding nature's fundamental processes and acquiring the capacity to replicate those processes to ultimately construct improved robotic platforms with similar capability. By examining the underlying principles of locomotion strategies found in nature, researchers sought to develop robots with similar capabilities in aerial, [1,2] aquatic, [3][4][5][6][7][8] and terrestrial [9][10][11][12] environments as well as using the robots as platforms in biomechanics research to understand the fundamentals of animal locomotion. [13] To negotiate compelx environments and flow regimes, animals must be able to perform multimodal locomotion.…”