Shape memory alloy-driven undulatory locomotion of a soft biomimetic ray robot

Kim, Hyungsoo; Heo, Junyoung; Choi, In‐Gyu; Ahn, Sung‐Hoon; Chu, Wujin

doi:10.1088/1748-3190/ac03bc

Cited by 14 publications

(7 citation statements)

References 37 publications

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“…Hence, soft robotic devices have been developed, as they can use simple deformations to achieve natural movements mimicking biological systems 26 – 28 . Current soft wing twisting technology has, in most cases, taken two forms: the first form produces actuation via shape memory alloys (SMA) or ionic polymer-metal composite (IPMC) 17 , 29 , 30 . However, as a creative approach, these solutions fail to produce large hydrodynamic forces when used in flapping wing conditions.…”

Section: Introductionmentioning

confidence: 99%

Soft-robotic green sea turtle (Chelonia mydas) developed to replace animal experimentation provides new insight into their propulsive strategies

van der Geest,

Garcia,

Borret

et al. 2023

Sci Rep

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Green sea turtles (Chelonia mydas) can swim up to 50 km per day while only consuming seagrass or microalgae. How the animal accomplishes this vast journey on such low energy intake points to the effectiveness of their swimming technique and is a testament to the power of evolution. Understanding the green sea turtle's ability to accomplish these journeys requires insight into their propulsive strategies. Conducting animal testing to uncover their propulsive strategies brings significant challenges: firstly, the ethical issues of conducting experiments on an endangered animal, and secondly, the animal may not even swim with its regular routine during the experiments. In this work, we develop a new soft-robotic sea turtle that reproduces the real animal's form and function to provide biomechanical insights without the need for invasive experimentation. We found that the green sea turtle may only produce propulsion for approximately 30% of the limb beat cycle, with the remaining 70% exploiting a power-preserving low-drag glide. Due to the animal's large mass and relatively low drag coefficient, losses in swim speed are minimal during the gliding stage. These findings may lead to the creation of a new generation of robotic systems for ocean exploration that use an optimised derivative of the sea turtle propulsive strategy.

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Section: Introductionmentioning

confidence: 99%

Soft-robotic green sea turtle (Chelonia mydas) developed to replace animal experimentation provides new insight into their propulsive strategies

van der Geest,

Garcia,

Borret

et al. 2023

Sci Rep

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“…In contrast, Liu et al [24] exhibits a pareddown mechanical structure featuring a singular flexible fin surface driven by individually powered fin rays that oscillate, thereby engendering a form of wave propagation that enhances operational stability. However, the existing robotic undulatory fins can only realize the swing motion of one degree of freedom (1-DOF) [25,26]. The range of fin motion is small, the motion form is more real, and the fish is too simplified.…”

Section: Introductionmentioning

confidence: 99%

Inspired by the Black Ghost Knifefish: Bionic Design of Undulatory Fin with 2-DOF Rays and Its Propulsion Performance

Zhou

Liu

et al. 2023

Applied Bionics and Biomechanics

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The demand for high-performance underwater thrusters in marine engineering is increasing. The concealed, mobile, and efficient underwater ability of fish provides many directions for research. The black ghost knifefish uses only wavy ventral fins to swim and can hover and roll in the water. Based on the physiological and morphological characteristics of the black ghost knifefish, we explored the structure and movement mode of the ventral fin, so as to establish a two-degree of freedom (2-DOF) structural model and kinematic model. We reveal the motion mechanism of the undulating fin propulsion through the constructed model and computational fluid dynamics. It is found that when the fin surface fluctuates, a pair of vortices with opposite directions will be formed on the concave side of the fin surface. These vortices will produce a central jet on the fin surface, provide a reverse impulse for the ventral fin, and make the fin obtain power. In addition, we found that the propulsive force of the ribbon fin along the body direction is positively correlated with the swing amplitude and frequency of the fin movement, and the propulsive torque of the ribbon fin to realize the maneuvering movement increases first and then decreases with the increase of the torsion angle. The research on the structure and motion mechanism of the ribbon fin of the black ghost knifefish provides a basis for the development of a bionic prototype of multi-DOF motion and the control strategy of high-mobility motion.

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“…As a result of these modeling difficulties, as well as significant weight and volume restrictions for sensing and control hardware, there has yet to be an untethered electrothermally-actuated soft robot with embedded sensors and associated modeling that capture actuator states ( Rich et al, 2018 ). In fact, most SMA-based soft walking robots often focus on designs that do not include embedded sensors and operate entirely through open-loop control or dependency on external hardware ( Huang et al, 2018 , 2019 ; Almubarak et al, 2020 ; Meng et al, 2020 ; Patterson et al, 2020 ; Boothby et al, 2021 ; Kim et al, 2021 ; Rehan et al, 2021 ; Thomas et al, 2021 ). In turn, modeling of these untethered robots, when it has been done, does not include time-dependent actuator states ( Goldberg et al, 2019 ; Huang et al, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

In-Situ Sensing and Dynamics Predictions for Electrothermally-Actuated Soft Robot Limbs

et al. 2022

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Untethered soft robots that locomote using electrothermally-responsive materials like shape memory alloy (SMA) face challenging design constraints for sensing actuator states. At the same time, modeling of actuator behaviors faces steep challenges, even with available sensor data, due to complex electrical-thermal-mechanical interactions and hysteresis. This article proposes a framework for in-situ sensing and dynamics modeling of actuator states, particularly temperature of SMA wires, which is used to predict robot motions. A planar soft limb is developed, actuated by a pair of SMA coils, that includes compact and robust sensors for temperature and angular deflection. Data from these sensors are used to train a neural network-based on the long short-term memory (LSTM) architecture to model both unidirectional (single SMA) and bidirectional (both SMAs) motion. Predictions from the model demonstrate that data from the temperature sensor, combined with control inputs, allow for dynamics predictions over extraordinarily long open-loop timescales (10 min) with little drift. Prediction errors are on the order of the soft deflection sensor’s accuracy. This architecture allows for compact designs of electrothermally-actuated soft robots that include sensing sufficient for motion predictions, helping to bring these robots into practical application.

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Shape memory alloy-driven undulatory locomotion of a soft biomimetic ray robot

Cited by 14 publications

References 37 publications

Soft-robotic green sea turtle (Chelonia mydas) developed to replace animal experimentation provides new insight into their propulsive strategies

Soft-robotic green sea turtle (Chelonia mydas) developed to replace animal experimentation provides new insight into their propulsive strategies

Inspired by the Black Ghost Knifefish: Bionic Design of Undulatory Fin with 2-DOF Rays and Its Propulsion Performance

In-Situ Sensing and Dynamics Predictions for Electrothermally-Actuated Soft Robot Limbs

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