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Several physico-mechanical designs evolved in fish are currently
inspiring robotic devices for propulsion and maneuvering purposes in
underwater vehicles. Considering the potential benefits involved, this
paper presents an overview of the swimming mechanisms employed by fish.
The motivation is to provide a relevant and useful introduction to the
ex...
Contexts in source publication
Context 1
... anguilliform mode the whole body participates in large-amplitude undulations ( Fig. 7a). Since at least one complete wavelength of the propulsive wave is present along the body, lateral forces are adequately cancelled out, minimising any tendencies for the body to ...
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... [22]. Typical examples of this common locomotion mode are the eel and the lamprey. See [23] for a summary of existing kinematic data on anguilliform locomotion. Similar movements are observed in the subcarangiform mode (e.g. trout), but the amplitude of the undulations is limited anteriorly, and increases only in the posterior half of the body (Fig. 7b). For carangiform swimming this is even more pronounced, as the body undulations are further confined to the last third of the body length ( Fig. 7c), and thrust is provided by a rather stiff caudal fin. Carangiform swimmers are generally faster than anguilliform or subcarangiform ones. However, their turning and accelerating abilities ...
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... locomotion. Similar movements are observed in the subcarangiform mode (e.g. trout), but the amplitude of the undulations is limited anteriorly, and increases only in the posterior half of the body (Fig. 7b). For carangiform swimming this is even more pronounced, as the body undulations are further confined to the last third of the body length ( Fig. 7c), and thrust is provided by a rather stiff caudal fin. Carangiform swimmers are generally faster than anguilliform or subcarangiform ones. However, their turning and accelerating abilities are compromised, due to the relative rigidity of their ...
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... as the tuna and the mackerel. Significant lateral movements occur only at the caudal fin (that produces more than 90% of the thrust) and at the area near the narrow peduncle. The body is very well streamlined to significantly reduce pressure drag, while the caudal fin is stiff and high, with a crescent-moon shape often referred to as lunate ( Fig. 7d). Despite the power of the caudal thrusts, the body shape and mass distribution ensure that the recoil forces are effectively minimised and very little sideslipping is induced. The design of thunniform swimmers is optimised for high-speed swimming in calm waters, and is not well-suited to other actions such as slow swimming, turning ...
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Citations
... The propulsion modes of fish can be categorized into two main types based on the differences in the source of fish movement and the manner in which fins are utilized: BCF (body and/or caudal fin) and MPF (median and/or paired fin) [4][5][6][7]. The body of BCF mode fish is soft and less rigid than that of MPF mode, and it utilizes the fluctuating curvature of the spine to drive the tail fin to oscillate and thus obtain a larger thrust, thus achieving a high swimming speed and propulsion efficiency. ...
This paper presents a biomimetic fish robot featuring a flexible spine driven by cables, which integrates the cable-driven mechanism with a flexible spine. The drive system separates the body and tail fin drives for control, offering enhanced flexibility and ease in achieving phase difference control between the body and tail fin movements compared to the conventional servo motor cascaded structure. A prototype of the biomimetic fish robot was developed, accompanied by the establishment of a kinematic model. Based on this model, a control method for the biomimetic fish is proposed. Additionally, we introduce the concept of prestress to establish a numerical model for the biomimetic fish. Using multi-physical field simulation software, we simulate the two-dimensional autonomous swimming process of the biomimetic fish under different flapping frequencies and solve for its swimming characteristics as well as hydrodynamic properties. Both the simulation and experimental results validate the accuracy of our kinematic model.
... Most fish swim by undulating their bodies and/or fins to create thrust [1,2]. Salmonids use the posterior section of their bodies and their caudal fins to propel themselves by flexing and creating a backward-moving wave, generating thrust for swimming [1][2][3][4]. Aside from basal metabolic rate and specific dynamic action, swimming exercise is believed to constitute a significant portion of a fish's energy expenditure [5][6][7]. ...
... Body and caudal fin swimmers, such as post-smolt Atlantic salmon, typically exhibit steady swimming interspersed with intermittent bursts and coast gaits [1,4]. Steady swimming is mainly supported by the skeletal slow, or red, muscles, fuelled aerobically, while bursts are enabled by the fast, or white, muscles [2,3]. It is plausible that the accelerations and decelerations and absence of steady swimming behaviour caused by the constant wave-like unsteady flow conditions decrease the swimming efficiency and consequently increase oxygen demand [52]. ...
... This shows that Atlantic salmon are more efficient, steady-endurance swimmers. When swimming in wave-like unsteady flow conditions, they use twice as much energy, contrary to some pectoral fin swimmers that are highly skilled in station holding and manoeuvring [3,4]. ...
The swimming performance of cultured finfish species is typically studied under steady flow conditions. However, flow conditions are mostly unsteady, for instance, as experienced in sea pens in exposed sea areas. Using a Loligo swim tunnel, we investigated the effects of swimming in steady and unsteady flows at increasing swimming speeds on post-smolt Atlantic salmon. Oxygen consumption (MO2), locomotory behaviour, and overall dynamic body acceleration (ODBA), as determined with implanted acoustic sensor tags, were compared between both flow conditions. Results were obtained for mean swimming speeds of 0.2 to 0.8 m.s−1 under both flow conditions. Sensor tags that were implanted in the abdominal cavity had no significant effects on MO2 and locomotory parameters. The MO2 of fish swimming in unsteady flows was significantly higher (15–53%) than when swimming in steady flows (p < 0.05). Significant interaction effects of ODBA with flow conditions and swimming speed were found. ODBA was strongly and positively correlated with swimming speed and MO2 in unsteady flow (R2 = 0.94 and R2 = 0.93, respectively) and in steady flow (R2 = 0.91 and R2 = 0.82, respectively). ODBA predicts MO2 well over the investigated range of swimming speeds in both flow conditions. In an unsteady flow condition, ODBA increased twice as fast with MO2 compared with steady flow conditions (p < 0.05). From these results, we can conclude that (1) swimming in unsteady flow is energetically more costly for post-smolt Atlantic salmon than swimming in steady flow, as indicated by higher MO2, and (2) ODBA can be used to estimate the oxygen consumption of post-smolt Atlantic salmon in unsteady flow in swim tunnels.
... The two major swimming modes of fish in the ocean are the body and/or caudal fin (BCF) mode and the median and/or paired fin (MPF) mode [1]. Through in-depth research on the swimming mechanism of fish [1][2][3], researchers have developed various unique biomimetic robotic fish with different swimming behaviors. ...
... The two major swimming modes of fish in the ocean are the body and/or caudal fin (BCF) mode and the median and/or paired fin (MPF) mode [1]. Through in-depth research on the swimming mechanism of fish [1][2][3], researchers have developed various unique biomimetic robotic fish with different swimming behaviors. In order to analyze and solve the interaction problem between the motion of robotic fish and the surrounding flow field structure, most current studies use numerical simulation methods to process the flow field to obtain physical quantities such as the vortex structure and velocity vector, thereby elucidating the swimming mechanism of robotic fish in the flow field and optimizing its behavior. ...
The pectoral fin propulsion of a bionic robotic fish always consists of two phases: propulsion and recovery. The robotic fish moves in a burst-and-coast swimming manner. This study aims to analyze a pair of bionic robotic fish with rigid pectoral fin propulsion with three degrees of freedom and optimize the elliptical propulsion curve with the minimum recovery stroke resistance using computational fluid dynamics methods. Then, the time allocated to the propulsion and recovery phases is investigated to maximize the propulsion performance of the bionic robotic fish. The numerical simulation results show that when the time ratio of the propulsion and recovery phases is 0.5:1, the resistance during the movement of the robotic fish is effectively reduced, and the drag-reducing effect is pronounced. According to a further analysis of pressure clouds and vortex structures, the pressure difference between the upstream and downstream fins of the pectoral fin varies with different stroke ratios. The increase in recovery phase time helps to prevent premature damage to the vortex ring structure generated during the propulsion process and improves propulsion efficiency.
... These tasks include underwater biological observation, pipeline inspection, resource exploration, and underwater reconnaissance [1][2][3][4]. In nature, fish possess exceptional underwater locomotion abilities, allowing them to swim swiftly and efficiently [5]. By emulating the movement patterns of fish, bionic underwater robots exhibit superior mobility, efficiency, and speed compared to traditional propeller-driven underwater robots. ...
In this article, we study the trajectory planning and tracking control of a bionic underwater robot under multiple dynamic obstacles. We first introduce the design of the bionic leopard cabinet underwater robot developed in our lab. Then, we model the trajectory planning problem of the bionic underwater robot by combining its dynamics and physical constraints. Furthermore, we conduct global trajectory planning for bionic underwater robots based on the temporal-spatial Bezier curves. In addition, based on the improved proximal policy optimization, local dynamic obstacle avoidance trajectory replanning is carried out. In addition, we design the fuzzy proportional-integral-derivative controller for tracking control of the planned trajectory. Finally, the effectiveness of the real-time trajectory planning and tracking control method is verified by comparative simulation in dynamic environment and semiphysical simulation of UWSim. Among them, the real-time trajectory planning method has advantages in trajectory length, trajectory smoothness, and planning time. The error of trajectory tracking control method is controlled around 0.2 m.
... The robot swims with the carangiform mode, a bodycaudal fin (BCF) locomotion which can be described as an amplitude-modulated traveling wave [39,40]. The following equation models the imposed transverse motion in a bodyfixed coordinate system for carangiform robotic fish [41]: ...
Bioinspired underwater robots can move efficiently, with agility, even in complex aquatic areas, reducing marine ecosystem disturbance during exploration and inspection. These robots can improve animal farming conditions and preserve wildlife. This study proposes a muscle-like control for an underactuated robot in carangiform swimming mode. The artifact exploits a single DC motor with a non-blocking transmission system to convert the motor’s oscillatory motion into the fishtail’s oscillation. The transmission system combines a magnetic coupling and a wire-driven mechanism. The control strategy was inspired by central pattern generators (CPGs) to control the torque exerted on the fishtail. It integrates proprioceptive sensory feedback to investigate the adaptability to different contexts. A parametrized control law relates the reference target to the fishtail’s angular position. Several tests were carried out to validate the control strategy. The proprioceptive feedback revealed that the controller can adapt to different environments and tail structure changes. The control law parameters variation accesses the robotic fish’s multi-modal swimming. Our solution can vary the swimming speed of 0.08 body lengths per second (BL/s), and change the steering direction and performance by an angular speed and turning curvature radius of 0.08 rad/s and 0.25 m, respectively. Performance can be improved with design changes, while still maintaining the developed control strategy. This approach ensures the robot’s maneuverability despite its underactuated structure. Energy consumption was evaluated under the robotic platform’s control and design. Our bioinspired control system offers an effective, reliable, and sustainable solution for exploring and monitoring aquatic environments, while minimizing human risks and preserving the ecosystem. Additionally, it creates new and innovative opportunities for interacting with marine species. Our findings demonstrate the potential of bioinspired technologies to advance the field of marine science and conservation.
... To name a few advantages, their ecofriendly design point at lower frequencies provides stealth, and their operating principle allows for high efficiency and advanced maneuverability. These devices mimic the thrust-producing thunniform swimming mode shown in Fig. 1 and are characterized by a relatively stiff caudal fin that performs a combination of out-of-phase pitch and heave, tracing an oscillating path, see, e.g., Triantafyllou et al. (1991), Sfakiotakis et al. (1999) and Lauder (2015). Apart from kinematics, the astonishing abilities of aquatic swimmers are attributed to a combination of fin shapes, materials, advanced actuation, and control. ...
... Fig. 1. Schematic representation of the thunniform swimming mode adapted from Sfakiotakis et al. (1999). as auxiliary ship thrusters with wave energy harvesting capabilities. ...
... In BCF locomotion, a backward traveling wave moves downstream to the whole trunk of the body to generate thrust. Breder 55 was the first to classify the BCF motion on the fish as Angulliform, Subcarangiform, Carangiform, and Thunniform based on the use of the part of the trunk and caudal fin 55,57,58 . These four types of BCF locomotion are identified based on the change in wavelength, and the amplitude envelope of the propulsive wave 58 . ...
... Breder 55 was the first to classify the BCF motion on the fish as Angulliform, Subcarangiform, Carangiform, and Thunniform based on the use of the part of the trunk and caudal fin 55,57,58 . These four types of BCF locomotion are identified based on the change in wavelength, and the amplitude envelope of the propulsive wave 58 . The pure undulation motion of the whole body is observed in anguilliform fishes, while the tail of the fish oscillates in thunniform fishes. ...
... The pitching motion is used extensively in carangiform and thunniform fishes 58 , which inspired various researchers to study pitching motion 36-39 . The thrust generation mechanism for the pitching motion of the fin can be attributed to the jet in the wake due to the formation of reverse von Karman vortices 58 . Andersen et al. 45 identified the wake patterns and correlated them with the drag-to-thrust transition in a pitching hydrofoil. ...
A review of recent literature on thrust generation mechanisms by a hydrofoil, bioinspired from fish locomotion is presented. The present work considers fish-inspired periodic kinematics of three types: pitching, heaving, and undulations along with the combination of some of these motions. The pitching corresponds to the tail of the fish while heaving and undulation correspond to that of the body. The undulation also corresponds to the surface of the body; for certain fishes. Both numerical and experimental studies in this arena have been reviewed. The present review follows the classification of oscillatory and undulatory motion. We discuss oscillatory motion with emphasis on pitching, heaving, and the combination of these two motions. In undulatory motion, we cover body undulation and surface undulation motion as a propulsive mechanism. We compare and contrast wake signatures, thrust, and propulsive efficiencies for different motion types. A future outlook, which may help researchers to identify open questions, has been provided.
... Bird flocks and fish schools involve interactions that are social or behavioral as well as physical interactions that are mediated by the aero-or hydro-dynamics of locomotion 4,7,10 . The challenges of understanding flow interactions stem from the spatiotemporal complexities of unsteady locomotion at intermediate to high Reynolds numbers Re 11,12 , many of which are compounded when multiple bodies interact through their flow fields [13][14][15][16] . ...
... Additional information about the apparatus and procedures are provided as "Methods", including a review of previous studies that have validated rotational or "flight mill" systems against rectilinear locomotion [27][28][29]33,34,[43][44][45][46] . The conditions studied here lead to motions of Reynolds number Re~10 3 , which is on the lower end of the range displayed by schooling fish and flocking birds 11,25,47 . ...
... Other dimensionless numbers include A/c = 0.375 and the Strouhal number St = Af =U = Re f =Re = 0:125. These values, while not intended to match any particular biological system, fall within the broad ranges of values relevant to flapping locomotion of animals 11,25,47 . ...
Collectively locomoting animals are often viewed as analogous to states of matter in that group-level phenomena emerge from individual-level interactions. Applying this framework to fish schools and bird flocks must account for visco-inertial flows as mediators of the physical interactions. Motivated by linear flight formations, here we show that pairwise flow interactions tend to promote crystalline or lattice-like arrangements, but such order is disrupted by unstably growing positional waves. Using robotic experiments on “mock flocks” of flapping wings in forward flight, we find that followers tend to lock into position behind a leader, but larger groups display flow-induced oscillatory modes – “flonons” – that grow in amplitude down the group and cause collisions. Force measurements and applied perturbations inform a wake interaction model that explains the self-ordering as mediated by spring-like forces and the self-amplification of disturbances as a resonance cascade. We further show that larger groups may be stabilized by introducing variability among individuals, which induces positional disorder while suppressing flonon amplification. These results derive from generic features including locomotor-flow phasing and nonreciprocal interactions with memory, and hence these phenomena may arise more generally in macroscale, flow-mediated collectives.
... Lift-based swimming, which is exploited by thunniform swimmers like the Guizhouichthyosaurus and the Ophthalmosaurus, requires a specific motion pattern and fin profile that the current soft robotic platform does not provide. As such, it is expected that the longer fins generate more thrust in this specific experimental configuration than the short ones with higher aspect ratios, despite the latter usually being associated with high-speed swimming (Webb 1984, Sfakiotakis et al 1999. The results are shown in table 2. The Utatsusaurus displays the greatest self-propelled speed despite not being the longest fin. ...
... Although it is suited to replicate subcarangiform or carangiform swimming, the longer forms (Cartorhynchus, Utatsusaurus, Mixosaurus, and potentially the longer Guizhouichthyosaurus reconstruction) may have behaved more like anguilliform swimmers, with an overall lesser and more constant stiffness throughout the tail, allowing for more lateral freedom (Motani et al 1996). The platform is also not suited to perform the oscillations associated with thunniform swimming (Ophthalmosaurus) appropriately (Sfakiotakis et al 1999). ...
Animals have evolved highly effective locomotion capabilities in terrestrial, aerial, and aquatic
environments. Over life’s history, mass extinctions have wiped out unique animal species with specialized
adaptations, leaving paleontologists to reconstruct their locomotion through fossil analysis. Despite
advancements, little is known about how extinct megafauna, such as the Ichthyosauria one of the most
successful lineages of marine reptiles, utilized their varied morphologies for swimming. Traditional
robotics struggle to mimic extinct locomotion effectively, but the emerging soft robotics field offers
a promising alternative to overcome this challenge. This paper aims to bridge this gap by studying
Mixosaurus locomotion with soft robotics, combining material modeling and biomechanics in physical
experimental validation. Combining a soft body with soft pneumatic actuators, the soft robotic platform
described in this study investigates the correlation between asymmetrical fins and buoyancy by recreating
the pitch torque generated by extinct swimming animals. We performed a comparative analysis of
thrust and torque generated by Carthorhyncus, Utatsusaurus, Mixosaurus, Guizhouichthyosaurus, and
Ophthalmosaurus tail fins in a flow tank. Experimental results suggest that the pitch torque on the torso
generated by hypocercal fin shapes such as found in model systems of Guizhouichthyosaurus, Mixosaurus
and Utatsusaurus produce distinct ventral body pitch effects able to mitigate the animal’s non-neutral
buoyancy. This body pitch control effect is particularly pronounced in Guizhouichthyosaurus, which
results suggest would have been able to generate high ventral pitch torque on the torso to compensate
for its positive buoyancy. By contrast, homocercal fin shapes may not have been conducive for such
buoyancy compensation, leaving torso pitch control to pectoral fins, for example. Across the range of the
actuation frequencies of the caudal fins tested, resulted in oscillatory modes arising, which in turn can
affect the for-aft thrust generated.
... In the context of pitching motion, it has been observed that the motion is used extensively in carangiform and thunniform fishes, 19 which inspired researchers to study the pitching motion more closely. 4,[20][21][22][23][24][25] The thrust generation mechanism for the pitching motion of fin can be attributed to jet in the wake owing to the formation of reverse von K arm an vortices. ...
... 4,[20][21][22][23][24][25] The thrust generation mechanism for the pitching motion of fin can be attributed to jet in the wake owing to the formation of reverse von K arm an vortices. 19 For pure pitching, the optimal thrust for an oscillating hydrofoil is produced for a specific range of Strouhal numbers (St) between 0.25 and 0.35, as presented by Triantafyllou et al. 26 Additionally, the study by Taylor et al. 1 demonstrated that birds, bats, and insects tend to converge within a similar range of St during cruising flight, suggesting that these animals adjust their cruising kinematics to optimize their pitching-related Strouhal number. Schnipper et al. 27 experimentally found different types of wakes ranging from 2S and 2P to a complex flow of 16 vortices in one pitching cycle hydrofoil. ...
We numerically study the fluid-structure interaction of a free-stream flow across a hydrofoil pitching at its leading edge with superimposed traveling wave-based surface undulations. We utilize an in-house code that employs the sharp interface immersed boundary method and consider a constant pitching amplitude $\theta_0 = 5^\circ$, a constant local amplitude-to-thickness ratio $A_L = 0.15$, and wave number $K = 20$ of surface undulation. We compare the effect of surface undulation on a pitching hydrofoil with that of a hydrofoil undergoing pure pitching or experiencing pure surface undulation. The findings reveal that surface undulation on the pitching hydrofoil increases thrust on the hydrofoil. The onset of asymmetry in the vortex street occurs at a lower pitching Strouhal number ($St$) due to the early formation of a vortex dipole. In addition to the presence of an asymmetric inverse von Kármán vortex street, higher pitching frequencies reveal re-deflection of the asymmetric inverse von Kármán vortices. We quantified dynamics of vortex dipole to explain the occurrence of asymmetric and re-deflected reverse von \karman vortex street. Furthermore, the analysis reveals an optimum combination of $St$ and phase speed that yields higher propulsive efficiency, as both motions compete in generating thrust. A linearly superimposed scaling analysis for the time-averaged thrust of the combined motion is also presented. The computations and scaling are found to be in good agreement.
