Amphibious Robot Research Articles

Design and Implementation of Small Modular Amphibious Robot System

Various marine engineering facilities have been eroded by marine organisms and wind waves for a long time, resulting in different types of damage to the surface of marine engineering facilities, such as the pile legs of offshore platforms. Therefore, in order to carry out safety inspections and other work on marine engineering facilities, a small amphibious robot structure system and a set of control systems adapted to it are independently developed. Various problems such as the modular design of the structure, composite motion mode, adsorption stability, wall adaptability of the crawling mode, and flaw localization have been solved by means of three-dimensional modeling, mechanical analysis, simulation, and electronic design. At the same time, a set of control systems including hardware and software is developed for the amphibious robot. In order to improve the stability and efficiency of the amphibious robot working underwater, a sliding mode control algorithm based on the exponential reaching law and saturation function is designed. For the fixed depth and fixed heading control functions, the sliding mode control algorithm and the PID control algorithm are simulated and compared. Finally, several types of experiments are carried out for the amphibious robot. The simulation and experimental results show that all the functions of the amphibious robot meet work requirements, such as the motion performance of the composite motion mode. Compared with the PID control algorithm, the sliding mode control algorithm has a faster response speed and better stability, which is conducive to the efficient and stable work of the amphibious robot underwater.

Advancements in amphibious robot navigation through wheeled odometer uncertainty extension and distributed information fusion

The advancement and safeguarding of the water-land interface region is of paramount importance, and amphibious robots with the capacity for autonomous operation can play a pivotal role in this domain. However, the inability of the majority of reliable navigation sensors to adapt to the water-land interface environment presents a significant challenge for amphibious robots, as obtaining positional information is crucial for autonomous operation. To address this issue, we have proposed a positioning and navigation framework, designated as NAWR (Navigation Algorithm for Amphibious Wheeled Robots), with the objective of enhancing the navigation capabilities of amphibious robots. Firstly, a method for representing the odometer's confidence based on a simplified wheel-terrain interaction model has been developed. This method quantitatively assesses the reliability of each odometer by estimating the slip rate. Secondly, we have introduced an improved split covariance intersection filter (I-SCIF), which maximizes the utilization of navigation information sources to enhance the accuracy of positional estimation. Finally, we will integrate these two methods to form the NAWR framework and validate the effectiveness of the proposed methods through multiple robot field trials. The results from both field trials and ablation tests collectively demonstrate that the modules and overall approach within the NAWR framework effectively enhance the navigation capabilities of amphibious robots.

Microfiber Actuators With Hot-Pressing-Programmable Mechano-Photothermal Responses for Electromagnetic Perception.

Electromagnetic radiation (EMR) is a ubiquitous harm and hard to detect dynamically in multiple scenarios. A mechano-photothermal cooperative microfiber film (MFF) actuator is developed that can synchronously detect EMR with high reliability. The programmable actuation is deployed by a hot-pressing methodology, achieving the MFF with moderate modulus (378MPa) and superior toughness (87.26MJm-3) that ensure superior response (0.068cm-1s-1) and bending curvature (0.63cm-1). A secondary hot-pressing can further program the actuation behavior with black phosphorus local photothermal enhancement patterns to achieve 2D-3D transformable geometries. An amphibious robot with a land-water adaptive locomotion mechanism is designed by programming the MFFs. It can crawl on land and locomote on water with a velocity up to ≈1.8mms-1, and ≈2.39cms-1, respectively. Employing the conductive fabric layer of the actuator with electromagnetic induction effect, the amphibious robot can synchronously perceive environmental EMR with sensitivity up to 99.73%±0.15% during locomotion, with superior adaptability to EMR source intensity (0.1 to 3000W) and distance (≈9m) compared to a commercial EMR detector. This EMR detective microfiber actuator can inspire a new direction of environment-interactive smart materials, and soft robots with multi-scenario adaptivity and autonomous environment perceptivity.

Hydrodynamic Simulation and Experiment of a Self-Adaptive Amphibious Robot Driven by Tracks and Bionic Fins.

Amphibious robots have broad prospects in the fields of industry, defense, and transportation. To improve the propulsion performance and reduce operation complexity, a novel bionic amphibious robot, namely AmphiFinbot-II, is presented in this paper. The swimming and walking components adopt a compound drive mechanism, enabling simultaneous control for the rotation of the track and the wave-like motion of the undulating fin. The robot employs different propulsion methods but utilizes the same operation strategy, eliminating the need for mode switching. The structure and the locomotion principle are introduced. The performance of the robot in different motion patterns was analyzed via computational fluid dynamics simulation. The simulation results verified the feasibility of the wave-like swimming mechanism. Physical experiments were conducted for both land and underwater motion, and the results were consistent with the simulation regulation. Both the underwater linear and angular velocity were proportional to the undulating frequency. The robot's maximum linear speed and steering speed on land were 2.26 m/s (2.79 BL/s) and 442°/s, respectively, while the maximum speeds underwater were 0.54 m/s (0.67 BL/s) and 84°/s, respectively. The research findings indicate that the robot possesses outstanding amphibious motion capabilities and a simplistic yet unified control approach, thereby validating the feasibility of the robot's design scheme, and offering a novel concept for the development of high-performance and self-contained amphibious robots.

Lightweight Sewer Pipe Crack Detection Method Based on Amphibious Robot and Improved YOLOv8n.

Aiming at the problem of difficult crack detection in underground urban sewage pipelines, a lightweight sewage pipeline crack detection method based on sewage pipeline robots and improved YOLOv8n is proposed. The method uses pipeline robots as the equipment carrier to move rapidly and collect high-definition data of apparent diseases in sewage pipelines with both water and sludge media. The lightweight RGCSPELAN module is introduced to reduce the number of parameters while ensuring the detection performance. First, we replaced the lightweight detection head Detect_LADH to reduce the number of parameters and improve the feature extraction of modeled cracks. Finally, we added the LSKA module to the SPPF module to improve the robustness of YOLOv8n. Compared with YOLOv5n, YOLOv6n, YOLOv8n, RT-DETRr18, YOLOv9t, and YOLOv10n, the improved YOLOv8n has a smaller number of parameters of only 1.6 M. The FPS index reaches 261, which is good for real-time detection, and at the same time, the model also has a good detection accuracy. The validation of sewage pipe crack detection through real scenarios proves the feasibility of the proposed method, which has good results in targeting both small and long cracks. It shows potential in improving the safety maintenance, detection efficiency, and cost-effectiveness of urban sewage pipes.

Development of a novel amphibious robot with a reusable cycloidal propulsion module

This paper proposes a novel amphibious robot with reusable cycloidal propulsion module, and conducts simulation and experimental studies on its propulsion performance. Underwater, the robot adopts the collaboration of multiple cycloidal propellers to achieve moving and turning, providing good maneuverability; on land, the four blades of each cycloidal propeller are used as the blade wheel to drive the robot to move and turn, thus realizing the reuse of the same propulsion module in two environments. The experimental results show that the robot's underwater movement speed coefficient reaches a maximum of 0.275; by changing the direction of the propellers on both sides, the robot can realize in-situ turning, and the turning speed increases with the increase of the revolution speed of the propeller. The robot multiplexes the cycloid propellers into blade wheels on land, moves with a maximum speed coefficient of 0.207, and realizes the functions of mobile turning and in-situ turning, respectively, by means of the speed difference between the blade wheels on both sides. The findings confirm the feasibility of the cycloid propeller as a reusable propulsion module for amphibious robots, and the developed robot has good maneuverability, which is promising for application in the field of amphibious operations.

Jellyfish‐inspired multimodular bionic amphibious robot

Jellyfish‐inspired multimodular bionic amphibious robot

A Soft Amphibious Voxel-Type Quadruped Robot Based on Origami Flexiball of Rhombic Dodecahedron.

The research work presents a novel voxel-type soft amphibious robot based on an assembly of origami flexiballs. The geometric and elastic constitutive models of the origami flexiball are theoretically established to elucidate its intricate deformation mechanism. Especially, the zero-energy storage phenomenon and the quasi-zero-stiffness characteristic are revealed to prove that the origami flexiball is suitable for serving as soft robotic components. As a proof of concept, fourteen origami flexiballs are interconnected to form a quadruped robot capable of walking or crawling in both underwater and terrestrial environments, including flat surfaces and sandy terrain. Its adaptability across multiple environments is enhanced by the origami polyhedra-inspired hollow structure, which naturally adjusts to underwater conditions such as hydrostatic pressure and currents, improving stability and performance. Other advantages of the voxel-type soft amphibious quadruped robot include its ease of manufacture using 3D printing with accessible soft elastic materials, ensuring rapid and cost-effective fabrication. We anticipate its potentially versatile applications, including underwater pipeline inspections, offshore maintenance, seabed exploration, ecological monitoring, and marine sample collection. By leveraging metamaterial features embodied in the origami polyhedra, the presented voxel-type soft robot exemplifies an innovative approach to achieving complex functionalities in soft robotics.

Terrestrial locomotion stability of undulating fin amphibious robots: Separated elastic fin rays and asynchronous control

To address the problem of poor postural stability in an undulating fin robot during terrestrial locomotion, this study proposes a novel design featuring separate elastic fin rays with an asynchronous control scheme for bilateral fin surfaces. In this scheme, the robotic fin ray structure and surface driving mode are innovatively designed to mitigate the pitch-angle instability caused by adverse factors, such as integral rigid fin rays and synchronized fin surfaces. Expanding on the ground dynamics model of the robot, this study examined the variation in the pitch angle of the robot body. In this study, an innovative design with separated elastic fin rays was proposed and their feasibility was validated through finite element simulations. In addition, a virtual simulation prototype of the robot was developed to verify the robot body stability under asynchronous fin surface control. The simulation results show that separate elastic fin rays and asynchronous control can effectively improve the postural stability of robots in terrestrial locomotion. In this study, a robot prototype was tested experimentally in various terrestrial environments. The experimental results indicate that equipping the robot with separated elastic fin rays and employing asynchronous motion control significantly enhances the motion postural stability across typical terrain conditions. The maximum pitch angle range can be reduced by 42.7–52.4%, providing new insights for the design of amphibious robots with undulating fins.

Research and Implementation of Pneumatic Amphibious Soft Bionic Robot

To meet the requirements of amphibious exploration, ocean exploration, and military reconnaissance tasks, a pneumatic amphibious soft bionic robot was developed by taking advantage of the structural characteristics, motion forms, and propulsion mechanisms of the sea lion fore-flippers, inchworms, Carangidae tails, and dolphin tails. Using silicone rubber as the main material of the robot, combined with the driving mechanism of the pneumatic soft bionic actuator, and based on the theory of mechanism design, a systematic structural design of the pneumatic amphibious soft bionic robot was carried out from the aspects of flippers, tail, head–neck, and trunk. Then, a numerical simulation algorithm was used to analyze the main executing mechanisms and their coordinated motion performance of the soft bionic robot and to verify the rationality and feasibility of the robot structure design and motion forms. With the use of rapid prototyping technology to complete the construction of the robot prototype body, based on the motion amplitude, frequency, and phase of the bionic prototype, the main execution mechanisms of the robot were controlled through a pneumatic system to carry out experimental testing. The results show that the performance of the robot is consistent with the original design and numerical simulation predictions, and it can achieve certain maneuverability, flexibility, and environmental adaptability. The significance of this work is the development of a pneumatic soft bionic robot suitable for amphibious environments, which provides a new idea for the bionic design and application of pneumatic soft robots.

Numerical Simulation of Motion Test of Bionic Amphibious Quadruped Robot

Bionic amphibious quadruped robots are a huge leap in robotics, with the ability to navigate various terrains with agility and efficiency. In this study, the researchers utilized numerical simulations of motion tests to assess the locomotion skills of these extraordinary robotic systems. They learned a lot about their functioning and problems by rigorously analyzing performance parameters across various terrains and conditions, such as terrain adaptability, traversal speed, energy efficiency, stability, and manoeuvrability. The results they obtained highlighted the importance of adaptive control algorithms and mechanical designs in maximizing traversal speed and energy economy, especially while negotiating difficult terrains. In addition, the study demonstrated the interdisciplinary character of research in bionic amphibious quadruped robots, drawing on insights from biomechanics, control theory, robotics, and computational modelling. By combining previous research and utilizing computational simulation approaches, they opened the road for the creation of versatile and durable robotic systems capable of navigating difficult terrains and surroundings with precision and efficiency. Future research efforts could focus on improving design and control, investigating novel propulsion mechanisms, adaptive locomotion tactics, and biomimetic control algorithms to improve performance and adaptability. Addressing the challenges identified in the research and seizing opportunities for innovation will drive the development of robotic systems that push the limits of locomotion capabilities and open up new possibilities for applications in exploration, search and rescue, environmental monitoring, and beyond.

SwarmPID: Enhancing Amphibious Robot Control through Partial Swarm Optimization

SwarmPID: Enhancing Amphibious Robot Control through Partial Swarm Optimization

Optimizing terrestrial locomotion of undulating-fin amphibious robots: Asynchronous control and phase-difference optimization

This paper presents an asynchronous motion-control approach for undulating-fin amphibious robots, with emphasis on optimizing the phase differences of bilateral fin-surface waves to mitigate the pitch-angle instability typically observed in synchronous control. A comprehensive ground dynamics model is used in this study, which facilitates the meticulous analysis of pitch-angle variations. Using simulation software, a virtual prototype is developed to validate the control stability. This approach is further substantiated via experimental tests conducted on a physical prototype in diverse terrestrial environments. Simulation and experimental results indicate that asynchronous motion control methods significantly enhancing postural stability undulating-fin robots during terrestrial locomotion. Experimental findings demonstrate that adopting asynchronous motion control reduces the maximum range of pitch angles by 38.9%–42.3%. This method significantly enhancing postural stability of robot terrestrial locomotion. This study provides new insights for the design of undulating-fin amphibious robots.

Amphibious Robots Locomotion Strategies in Unstructured Complex Environments: A Review

In the previous literature, amphibious robots focused mainly on locomotion in underwater and flat land surface manoeuvring. Few amphibious robots focused on unstructured land environments. The amphibious robot designs were more emphasised in academics, leading to more work done in building amphibious robots that mimic biological amphibians, imitating the geometry and overall functionality of the amphibious robots. Developing amphibious robots with propulsive mechanisms for manoeuvring in a water environment received more attention than other functionalities like adaptability on rough natural terrain and obstacle repositioning capability. However, practical applications like reconnaissance and surveying posed challenges in the ground environment, which had unstructured and complex terrain profiles, especially in the transition area. Therefore, reviewing the amphibious robots focused on manoeuvring complex uneven surfaces was essential. The literature had comprehensive review papers on navigation strategies encompassing manoeuvring on flat ground surfaces and underwater locomotion. There was a need for a focused study that highlighted the amphibious robot that manoeuvred in an unstructured land environment. The open challenges and recent solutions by designing new mechanisms and deployment issues were highlighted and reviewed. Hence, the paper addressed a more specific review of amphibious robot locomotion in an unstructured environment. The paper also discussed a case study of an amphibious robot capable of locomotion in unstructured environments. It was envisaged that the review would provide directions and insights to researchers and robotic system designers on developing robust propulsive mechanisms for amphibious robots capable of locomotion in unstructured environments.Keywords: manoeuvrability, mobility, terrain, unified locomotion, mechanism, propulsion

Development of Portable Magnetic Adsorption Amphibious Robot

In this study, a portable magnetic adsorption amphibious robot which can operate on and below the waterline is developed for special curved environments, such as the pile legs of offshore platforms and the outer walls of ships. An open robot integrated control system based on a domestic chip is developed, and two operating modes of local control operation and remote wireless operation are realized. A permanent magnet adsorption scheme combining a magnetic adsorption track and a synchronous belt wheel is designed, static and dynamic analysis of the wall-climbing operation of the robot is carried out, and a kinematic model of the underwater robot is established. The experimental results show that the robot can effectively complete amphibious tasks and can realize the accurate control of attitude in water, proving it to be an effective tool for amphibious tasks, such as operating on the pile legs of offshore platforms and the outer walls of ships.

Design based on portable amphibious track robot

A portable amphibious robot that can operate on and under the waterline is designed for the special curved environment such as the pile leg of the offshore platform and the outer wall of the ship. The mechanical structure of the robot and the permanent magnet adsorption scheme of the magnetic adsorption track are designed. The robot can effectively complete amphibious tasks, and provides an effective way for amphibious tasks such as pile legs of offshore platforms and exterior walls of ships.

Conceptualization and Topology Optimization of Ampheel: An Integration of Rolling Wheel and Turtle-Inspired Mechanism for Amphibious Mobile Robot

The primary distinguishing feature of mobile robots is the ability to traverse various environments, setting them apart in the realm of robotics. The mobility of a robot hinges primarily on its locomotion mechanism, which dictates how it moves. The existing unimodal mobile robots are limited to work within the environment for which they are designed for and hence lack a scope to adapt the change in the terrain especially when they put to work in a mixed environment like land and water. Many applications like land and underwater search/rescue, shore infrastructure inspection, coastal area defence and security, offshore energy harvesting, space exploration, etc. demand a mobile robot that can traverse in both terrestrial and aquatic environments with the help of dual or multimodal locomotion mechanism, something like an amphibious animal. Most of the available amphibious robotic solutions have different appendages for both the environment, need human intervention to changeover the mechanism for transition, require different driving system for land and water locomotion and have fragile structures that limit the manoeuvrability. The proposed conceptual design called “Ampheel” is a novel amphibious locomotion mechanism inspired by the biomechanics of freshwater turtles. Ampheel incorporates a rigid wheel, enabling the robot to move on land, integrating soft actuators within it which emulate the turtle's leg-like extensions and enable the aquatic locomotion. Unlike the existing amphibious robots, the Ampheel utilizes the rotational motion of itself as a common driving system for both the environments. This reduces the need of multiple driving systems and also simplifies the control system. Ampheel is designed for safe travelling on land considering the maximum payload of robot as 20 kg including self-weight. Topology optimization of Ampheel is also carried out using ANSYS software for reduction of weight. Additionally, a unique interfacing shaft is designed that transmits the required torque to Ampheel for rotation and also channelise the compressed air to soft pneumatic actuators for inflation during rotation of Ampheel in aquatic setting. The fabricated Ampheel assembly is experimentally checked for failure under the applicable loading condition and found safe.

A numerical study on the hydrodynamics of a swimming crocodile model

Aiming to uncover the propulsion mechanisms underlying a cruising crocodile, we conduct computational fluid dynamics (CFD) simulations on the flow around a simplified three-dimensional model of the Crocodylus siamensis. The locomotion of the crocodile model is realized through undulating its body and tail, mimicking a crocodile-like swimming pattern. At a cruising speed of U∞ = 0.5 m/s (corresponding to a Reynolds number Re = 9.95 × 105 based on U∞ and the body length L), the hydrodynamics of the crocodile model are investigated, taking into account effects of the undulation parameters (i.e., amplitude A and frequency f). The normalized undulation parameters cover broad ranges of 0.6 ≤ A* = A/W ≤ 1.0 and 0.25 ≤ f * = fW/U∞ ≤ 0.625, where W is the body width. The CFD simulations are conducted in ANSYS Fluent, with the SST k–ω turbulence model and user-defined functions for dynamic mesh being used. Numerical results reveal that A* and f * render profound effects on the hydrodynamic performance of the crocodile model. The time-mean axial force coefficient (CA¯) and power coefficient (C¯Power) exhibit rapid growth with increasing A* and/or f *, while the root mean square lateral force coefficient (Cy,rms) is more dependent on f * than on A*. It is further found that, irrespective of A*, CA¯ and C¯Power can be well scaled with Strouhal number St (= 2fA/U∞) or St2(1 − U∞/c). Furthermore, distinct flow patterns are observed in the wake of the crocodile model undulating at different St, corresponding to the drag, transition (or cruising), and thrust type swimming, respectively. Discussion is made on the wake flow structures and their connections to the generation of the hydrodynamic forces. The findings from this work contribute to the understanding of the propulsion mechanisms of the swimming crocodile, meaningful for the design of efficient biomimetic amphibious robots.

An Amphibious Fully-Soft Centimeter-Scale Miniature Crawling Robot Powered by Electrohydraulic Fluid Kinetic Energy.

Miniature locomotion robots with the ability to navigate confined environments show great promise for a wide range of tasks, including search and rescue operations. Soft miniature locomotion robots, as a burgeoning field, have attracted significant research interest due to their exceptional terrain adaptability and safety features. Here, a fully-soft centimeter-scale miniature crawling robot directly powered by fluid kinetic energy generated by an electrohydraulic actuator is introduced. Through optimization of the operating voltage and design parameters, the average crawling velocity of the robot is dramatically enhanced, reaching 16mm s-1. The optimized robot weighs 6.3g and measures 5cm in length, 5cm in width, and 6mm in height. By combining two robots in parallel, the robot can achieve a turning rate of ≈3° s-1. Additionally, by reconfiguring the distribution of electrodes in the electrohydraulic actuator, the robot can achieve 2 degrees-of-freedom translational motion, improving its maneuverability in narrow spaces. Finally, the use of a soft water-proof skin is demonstrated for underwater locomotion and actuation. In comparison with other soft miniature crawling robots, this robot with full softness can achieve relatively high crawling velocity as well as increased robustness and recovery.

An Efficient Optimization Design Framework for Low-Resistance Shape of Bionic Amphibious Robot

An Efficient Optimization Design Framework for Low-Resistance Shape of Bionic Amphibious Robot