Figure - available from: International Journal of Advanced Robotic Systems
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Classification of swimming modes: (a) BCF and (b) MPF. Blue areas contribute to swim. Adapted and redrawn from Ref. 32 BCF: body and/or caudal fin; MPF: median and/or paired fin.
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Recently, the increasing interest in underwater exploration motivates the development of aquatic unmanned vehicles. To execute hazardous tasks in an unknown or even hostile environment, researchers have directed on developing biomimetic robots inspired by the extraordinary maneuverability, cruising speed, and propulsion efficiency of fish. Neverthe...
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Citations
... replicate muscle-like actuation and theoretically offer unlimited degrees of freedom [38][39][40][41][42][43][44][45] . Their fully soft-bodied structures, composed of pliable materials and highly deformable components, enable gentle interactions with fragile specimens [45][46][47][48][49] and adaptability in unstructured environments [50][51][52][53][54] (Fig. 1c). ...
The deep ocean, Earth’s untouched expanse, presents immense challenges for exploration due to its extreme pressure, temperature, and darkness. Unlike traditional marine robots that require specialized metallic vessels for protection, deep-sea species thrive without such cumbersome pressure-resistant designs. Their pressure-adaptive forms, unique propulsion methods, and advanced senses have inspired innovation in designing lightweight, compact soft machines. This perspective addresses challenges, recent strides, and design strategies for bioinspired deep-sea soft robots. Drawing from abyssal life, it explores the actuation, sensing, power, and pressure resilience of multifunctional deep-sea soft robots, offering game-changing solutions for profound exploration and operation in harsh conditions.
Fish-like agile movements, such as fast forward swimming and rapid turning, are essential for robots to perform a wide variety of tasks in aquatic environments. However, achieving these locomotion capabilities simultaneously in existing biomimetic underwater robots has proven challenging. Here, we present a self-contained robotic fish capable of swimming at a speed of 6.3 body length per second and pivot turning at an angular speed of 1450° per second. These fast motions, which compare well with those of real fish, are realized by directly oscillating a flexible body using an electromagnetic motor. This direct-drive (DD) method eliminates the need for transmission parts, simplifies the robotic structure, improves mechanical robustness, and enables the use of a flexible continuum body that passively interacts with water, generating fish-like body deformations and subsequent rapid swimming. This also allows the robot to have the Strouhal and swimming numbers that match the typical values observed in nature. Moreover, the observed frequency peaks in swimming are similar to computed values using a model, which guides the design of the robot. These results illustrate the DD method as a promising framework for the creation of highly versatile biomimetic underwater robots.
Underwater unmanned robots are an essential tool for human underwater exploration and detection and are widely employed in a variety of underwater operational settings. One of the hottest issues in this field is applying bionic notions to the creation of underwater unmanned robots by simulating fish swimming or cephalopod crawling. Using the tentacle suction cup adsorption technique during octopus’ predation as a model, underwater magnetic adsorption robots with the opening and closing claws were studied in this paper. First, the robot’s general structural design is presented. The claw mechanism is demonstrated by mimicking the octopus’s tentacle action during feeding, which primarily consists of an opening and closing claw that replicates the octopus’s tentacle and a magnetic adsorption unit that replicates the octopus’s suction cup adsorption. Then, the Kriging response surface optimization method is used to optimize the design of the claw mechanism to obtain excellent mechanical properties, and simulation software is used to verify. Finally, a robot prototype was built and its pool tests were conducted, with some experimental results presented. The experimental results show that after the robot reaches the predetermined position through pneumatic ejection and secondary propulsion launch, it can quickly open its claws within 0.11 s and apply 462.42 N adsorption force to complete the adsorption of the target.
This paper proposes a novel intelligent approach to swarm robotics, drawing inspiration from the collective foraging behavior exhibited by fish schools. A bio-inspired neural network (BINN) and a self-organizing map (SOM) algorithm are used to enable the swarm to emulate fish-like behaviors such as collision-free navigation and dynamic subgroup formation. The swarm robots are designed to adaptively reconfigure their movements in response to environmental changes, mimicking the flexibility and robustness of fish foraging patterns. The simulation results show that the proposed approach demonstrates improved cooperation, efficiency, and adaptability in various scenarios. The proposed approach shows significant strides in the field of swarm robotics by successfully implementing fish-inspired foraging strategies. The integration of neurodynamic models with swarm intelligence not only enhances the autonomous capabilities of individual robots, but also improves the collective efficiency of the swarm robots.
Biomimetic robotics can help support underwater exploration and monitoring while minimizing ecosystem disturbance. It also has potential applications in sustainable aquafarming management, biodiversity preservation, and animalrobot interaction studies. This study proposes a bio-inspired control strategy for an underactuated robotic fish, which utilizes a single DC motor to drive a mechanism that converts the motor’s oscillating motion into an oscillatory motion of the robotic fishtail through a magnetic coupling and a wire-driven system. The proposed control strategy for the robotic fish is based on central pattern generators (CPGs) and incorporates proprioceptive sensory feedback. The torque exerted on the fishtail is adjusted based on its position, allowing for increased or decreased body speed and steering with different angular speeds and radii of curvature despite the underactuated design. The robotic fish can vary the swimming speed of 0.08 body lengths per second (BL/s) with a related change in the tailbeating frequency up to 2.3 Hz, and it can vary the steering angular speed in the range of 0.08 rad/s with a relative change in the curvature radius of 0.25 m. The controller can adapt to changes in tail structure, weight, or the surrounding environment based on the proprioceptive feedback. Design changes to the modular design can improve speed and steering performances, maintaining the control strategy developed.
The polyvinyl chloride (PVC) gel actuator has the advantages of low mass density, large actuation strain, good compliance, and simple fabrication. It deforms when excited by a voltage, and the deformation amplitude of the actuator is higher when an alternating current (AC) voltage of a specific frequency causes the actuator to resonate. In this paper, a circular-plane actuator based on PVC gel film and flexible electrodes was developed. Then, a theoretical model is established based on the Yeoh strain energy density function model and the mechanical analysis of deformation region-boundary constraints, and the key parameters affecting the deformation are obtained. Subsequently, finite element simulation tests were done on the basis of this model, and the values of uniaxial stretching were highly consistent with the previous actual experimental results, which verified the reasonableness of the model and simulation method. Then, we focus on the analysis of the resonance frequencies of PVC actuators with different plasticizer content, electrode diameter, and pre-stretching degree. Finally, we compare the differences in time-domain characteristics of PVC actuators in the resonant and non-resonant states.
