Aquatic Robots Research Articles

A Simple Physical Model for Control of a Propellerless Aquatic Robot

Abstract This paper is concerned with the motion of an aquatic robot whose body has the form of a sharp-edged foil. The robot is propelled by rotating the internal rotor without shell deformation. The motion of the robot is described by a finite-dimensional mathematical model derived from physical considerations. This model takes into account the effect of added masses and viscous friction. The parameters of the model are calculated from comparison of experimental data and numerical solution to the equations of rigid body motion and the Navier–Stokes equations. The proposed mathematical model is used to define controls implementing straight-line motion, motion in a circle, and motion along a complex trajectory. Experiments for estimation of the efficiency of the model have been conducted.

Passive reconfigurable end effector for underwater simulation on humanoids

The underwater environment uses to be a harsh place to test aquatic robots just after analyze their performance with computational simulations. Apart from the necessary tasks, the robot has to perform additional algorithms in its first tests, like handling with drag or buoyancy forces. A mechanical simulator of the underwater environment is proposed to avoid this gap between virtual simulations and experiments in submerged spaces. This simulator is based on a passive reconfigurable mechanism attached to the robot's trunk or a human body for training before immersion. This mechanism acts as a wearable end effector of a cable-driven robot. This configuration allows to exert desired wrenches in two different links, and it is suitable for humanoid bodies. These forces focus on simulating the underwater force distributed throughout the trunk by exerting specific forces in the hip and the chest of a humanoid robot or a scuba diver. The elastic behavior of different compliant mechanisms related to this mechanism is analyzed. Theoretical simulations and real experiments are developed.

Poly(N-isopropylacrylamide) Hydrogel for Diving/Surfacing Device.

Underwater robots and vehicles have received great attention due to their potential applications in remote sensing and search and rescue. A challenge for micro aquatic robots is the lack of small motors needed for three-dimensional locomotion in water. Here, we show a simple diving and surfacing device fabricated from thermo-sensitive poly(N-isopropylacrylamide) or a poly(N-isopropylacrylamide)-containing hydrogel. The poly(N-isopropylacrylamide)-containing device exhibited fast and reversible diving/surfacing cycles in response to changing temperature. Modulation of the interaction between poly(N-isopropylacrylamide) chains and water molecules at temperatures above or below the lower critical solution temperature regulates the gel density through the swelling and de-swelling. The gel surfaced in water when heated and sank when cooled. We further showed reversible diving/surfacing cycles of the device when exposed to electrical and ultrasonic stimuli. Finally, a small electrically heated gel was incorporated into a miniature submarine and used to control the diving depth. These results suggest that the poly(N-isopropylacrylamide)-containing device has good potential for underwater remote-controlled micro aquatic robots.

Soft Robots for Ocean Exploration and Offshore Operations: A Perspective.

The ocean and human activities related to the sea are under increasing pressure due to climate change, widespread pollution, and growth of the offshore energy sector. Data, in under-sampled regions of the ocean and in the offshore patches where the industrial expansion is taking place, are fundamental to manage successfully a sustainable development and to mitigate climate change. Existing technology cannot cope with the vast and harsh environments that need monitoring and sampling the most. The limiting factors are, among others, the spatial scales of the physical domain, the high pressure, and the strong hydrodynamic perturbations, which require vehicles with a combination of persistent autonomy, augmented efficiency, extreme robustness, and advanced control. In light of the most recent developments in soft robotics technologies, we propose that the use of soft robots may aid in addressing the challenges posed by abyssal and wave-dominated environments. Nevertheless, soft robots also allow for fast and low-cost manufacturing, presenting a new potential problem: marine pollution from ubiquitous soft sampling devices. In this study, the technological and scientific gaps are widely discussed, as they represent the driving factors for the development of soft robotics. Offshore industry supports increasing energy demand and the employment of robots on marine assets is growing. Such expansion needs to be sustained by the knowledge of the oceanic environment, where large remote areas are yet to be explored and adequately sampled. We offer our perspective on the development of sustainable soft systems, indicating the characteristics of the existing soft robots that promote underwater maneuverability, locomotion, and sampling. This perspective encourages an interdisciplinary approach to the design of aquatic soft robots and invites a discussion about the industrial and oceanographic needs that call for their application.

Locomotion Strategies for Amphibious Robots-A Review

In the past two decades, unmanned amphibious robots have proven the most promising and efficient systems ranging from scientific, military, and commercial applications. The applications like monitoring, surveillance, reconnaissance, and military combat operations require platforms to maneuver on challenging, complex, rugged terrains and diverse environments. The recent technological advancements and development in aquatic robotics and mobile robotics have facilitated a more agile, robust, and efficient amphibious robots maneuvering in multiple environments and various terrain profiles. Amphibious robot locomotion inspired by nature, such as amphibians, offers augmented flexibility, improved adaptability, and higher mobility over terrestrial, aquatic, and aerial mediums. In this review, amphibious robots’ locomotion mechanism designed and developed previously are consolidated, systematically The review also analyzes the literature on amphibious robot highlighting the limitations, open research areas, recent key development in this research field. Further development and contributions to amphibious robot locomotion, actuation, and control can be utilized to perform specific missions in sophisticated environments, where tasks are unsafe or hardly feasible for the divers or traditional aquatic and terrestrial robots.

Development of Aquatic Robot with Four Fins for Underwater Environment with Floating Objects

Development of Aquatic Robot with Four Fins for Underwater Environment with Floating Objects

Development of Aquatic Robot with Four Fins for Underwater Environment with Floating Objects

Development of Aquatic Robot with Four Fins for Underwater Environment with Floating Objects

Plasmonic-Enhanced Graphene Oxide-Based Aquatic Robot for Target Cargo Delivery.

The design and fabrication of light-actuated robots that can perform selective motions and targeted cargo delivery have attracted increasing interest in various fields. However, these robots' high-speed locomotion, precise direction control, and efficient actuation ability remain big challenges because of the relatively low photothermal efficiency, especially in the aquatic environment. This work proposes a plasmonic-enhanced graphene oxide (GO)-gold nanorod (Au NR)/calcium alginate (Ca-alginate) aquatic robot. The proposed robot design includes an independent power module (GO-Au NR layer) and a microscale cargo-loaded module (Ca-alginate layer). The plasmonic effect of Au NRs greatly improves the heat transfer efficiency, which in turn increases the temperature variation up to three times during the actuating process. This situation leads to a high traveling speed of the robot up to ∼35 mm/s. Benefiting from the high light-to-work efficiency, the position and posture of the proposed robot have good control in the aquatic environment. The robot is capable of programmable trajectory following, multirobot gathering, separation, and cooperation, providing an efficient solution for cargo delivery. Moreover, after releasing the cargo-loaded module to the target location, the power module can be easily actuated for collection, avoiding the potential side effects from the residual photothermal particles in conventional methods. The plasmonic-enhanced photothermal mechanism and independent module design offer a strategy for light-actuated aquatic robot development and would bring opportunities to further develop biomedical applications.

Biomimetic Realization of a Robotic Penguin Wing: Design and Thrust Characteristics

Flapping flippers or fins are widely employed in biomimetic and bioinspired aquatic robots that imitate natural swimmers, such as fish and dolphins. This article involves robotic biomimetics of the penguin, which is often overlooked as an excellent swimmer benefiting from agile wings. To achieve equivalent swimming skills in an aquatic robot, the wing motion of a real penguin was investigated. Based on the findings, we developed a three-DOF robotic penguin wing that is able to implement the same flapping, feathering, and pitch motions as in natural penguins. A kinematic analysis is presented, and the generation of swimming motions is demonstrated. We designed experiments to study the thrust characteristics of the motion of each joint. The results suggest that the flapping motion generates the main thrust during locomotion and the pitch angle can effectively change the thrust direction while the feathering motion enables active control of the angle of attack (AoA). According to the results, stalling of the wing occurs near an AoA of 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> in the steady state; however, the feathering motion can avoid the stall and boost the net thrust by a factor of up to 7 relative to the net thrust without active feathering. Furthermore, the introduction of the feathering motion reduces the torque required to actuate the flapping motion. The hydrodynamics of the wing in different flow states are also discussed.

Nonlinear model predictive position control for a tail-actuated robotic fish

Position control is a significant technique for the underwater application of robotic fish; however, it is also very challenging due to the underactuated property and input coupling of system dynamics. In this article, a two-stage orientation–velocity nonlinear model predictive controller is proposed to solve this problem. A scaled averaging model of tail-actuated robotic fish is constructed at first. Then, the novel strategy based on orientation and velocity control is developed as well as proved to be equivalent with position control in the sense of Lyapunov. Furthermore, a nonlinear model predictive controller with a two-stage switching strategy is designed to regulate the orientation and velocity error. Finally, the simulation results demonstrate the superiority of the proposed control algorithm compared with other methods. Particularly, there exists an interesting twist-braking behavior in simulation, which indicates that the proposed method makes better use of the system dynamics. The proposed method is efficient for not only bionic robotic fish but also other aquatic underactuated robots, which offers new insight into the position control of underwater robots.

An artificial aquatic polyp that wirelessly attracts, grasps, and releases objects

The development of light-responsive materials has captured scientific attention and advanced the development of wirelessly driven terrestrial soft robots. Marine organisms trigger inspiration to expand the paradigm of untethered soft robotics into aqueous environments. However, this expansion toward aquatic soft robots is hampered by the slow response of most light-driven polymers to low light intensities and by the lack of controlled multishape deformations. Herein, we present a surface-anchored artificial aquatic coral polyp composed of a magnetically driven stem and a light-driven gripper. Through magnetically driven motion, the polyp induces stirring and attracts suspended targets. The light-responsive gripper is sensitive to low light intensities and has programmable states and rapid and highly controlled actuation, allowing the polyp to capture or release targets on demand. The artificial polyp demonstrates that assemblies of stimuli-responsive materials in water utilizing coordinated motion can perform tasks not possible for single-component devices.

Practical model‐free robust estimation and control design for an underwater soft IPMC actuator

In the trend of the recent development of soft actuators, ionic polymer metal composite (IPMC) is considered as one of the new and innovative soft materials. The IPMC is suited to be utilised in medical micro robots and bio-inspired aquatic robotics. It is distinguished by nimble, soft, silent, flexible and lightweight properties. In fact, for the IPMC actuator, hysteresis and creep non-linearities are inevitable; and it is a great challenge to handle them and to achieve high-precision tracking in the control design, especially when the internal system morphology is complex and not fully understood. This study proposes a new model-free control approach for an underwater IPMC actuator to overcome the lack of its exact model and to achieve accurate trajectory tracking. This approach is synthesised based on a non-linear extended state observer technique to estimate lumped uncertainties and disturbances. Furthermore, a sliding mode controller is added as an extra input to deal with the estimation error and to assure the tracking robustness. Finally, the proposed control is experimentally verified to show its effectiveness in comparison with a non-singular terminal sliding mode controller. The experimental results indicate that the proposed controller is capable of delivering good tracking accuracy with strong robustness.

Development of environmental niche models for use in underwater vehicle navigation

This paper presents a review of Environmental Niche Modeling and a methodology for isolating the environmental niche of an aquatic species, given that prior information is available for characterising the physical tolerances for that species. To test and demonstrate our methodology, the environmental niche of the kelp bass has been isolated within Big Fisherman's Cove, Santa Catalina Island, CA, at specific confidence intervals. The motivation for this examination is to demonstrate the utility of ecological analysis in Robotics. Specifically, the utilisation of physical water properties to provide relative navigation and localisation for an aquatic robot. The environmental niches act as navigational landmarks in the seemingly featureless underwater environment. As water patches tend to stick together, this provides persistent landmarks for use in aquatic navigation problems. We provide the background and development of Environmental Niche Models, and present results from field trials for solving the navigation and localisation problem for underwater vehicles. Specifically, we provide results from a technique developed by the authors that utilises physical water parameters, e.g., temperature, salinity, chlorophyll, etc., to localise an underwater vehicle in a given region. The presented method leverages the concept of Environmental Niche Models to provide accurate position estimation that rivals GPS accuracy.

Low-power microelectronics embedded in live jellyfish enhance propulsion.

Artificial control of animal locomotion has the potential to simultaneously address longstanding challenges to actuation, control, and power requirements in soft robotics. Robotic manipulation of locomotion can also address previously inaccessible questions about organismal biology otherwise limited to observations of naturally occurring behaviors. Here, we present a biohybrid robot that uses onboard microelectronics to induce swimming in live jellyfish. Measurements demonstrate that propulsion can be substantially enhanced by driving body contractions at an optimal frequency range faster than natural behavior. Swimming speed can be enhanced nearly threefold, with only a twofold increase in metabolic expenditure of the animal and 10 mW of external power input to the microelectronics. Thus, this biohybrid robot uses 10 to 1000 times less external power per mass than other aquatic robots reported in literature. This capability can expand the performance envelope of biohybrid robots relative to natural animals for applications such as ocean monitoring.

Deep Reinforcement Learning for Snake Robot Locomotion

Abstract The design of gaits for underactuated robots is often unintuitive, with many results derived from either trial and error or simplification of system structure. Recent advances in deep reinforcement learning have yielded results for systems continuous in either states or actions, which may extend to a variety of locomoting robots. In this work we employ reinforcement learning to derive efficient and novel gaits for both terrestrial and aquatic multi-link snake robots. Although such systems operate in different environments, we show that their shared geometric structure allows us to utilize the same learning techniques in both cases to find gaits without any human input. We present results learned and rolled out in simulation, and we describe preliminary efforts to implement the entire learning process on a physical system.

A Neuro-Inspired Computational Model for a Visually Guided Robotic Lamprey Using Frame and Event Based Cameras

The computational load associated with computer vision is often prohibitive, and limits the capacity for on-board image analysis in compact mobile robots. Replicating the kind of feature detection and neural processing that animals excel at remains a challenge in most biomimetic aquatic robots. Event-driven sensors use a biologically inspired sensing strategy to eliminate the need for complete frame capture. Systems employing event-driven cameras enjoy reduced latencies, power consumption, bandwidth, and benefit from a large dynamic range. However, to the best of our knowledge, no work has been done to evaluate the performance of these devices in underwater robotics. This work proposes a robotic lamprey design capable of supporting computer vision, and uses this system to validate a computational neuron model for driving anguilliform swimming. The robot is equipped with two different types of cameras: frame-based and event-based cameras. These were used to stimulate the neural network, yielding goal-oriented swimming. Finally, a study is conducted comparing the performance of the computational model when driven by the two different types of camera. It was observed that event-based cameras improved the accuracy of swimming trajectories and led to significant improvements in the rate at which visual inputs were processed by the network.

A Water Surface Cleaning Robot

This paper describes the design of a robot for cleaning rubbish floating on the water surface. Three important issues for designing the aquatic robots are a cost-effective solution along with robustness and durability. Due to the nature of the cleaning work, we designed the vehicle structure that can provide high stability, good ability in maneuver and can easily collect all the waste flowing in between. A pontoon shaped hull works best for this case and fulfils all the hydrostatic, structural stability criteria. For removal and collection of surface waste, a motor-driven collecting-arm system has been designed for collecting the wastes and redeploying it into a rectangular basket on the hull. This design provides simple and effective waste removal and accommodates large amounts of waste within a small space. For the prototype, the hulls were made up of styrofoam which is wrapped by fibre and then coated with waterproof and resin. It supported together by aluminum. This light and tough structure support the total weight of the system. The propulsion system based on a differential drive mechanism has been designed, which allows the robots to take a 360 turn on the spot and provides high thrust. Electronic circuit and motors have been placing inside the hull, in order to protect them from water. The robot is manually controlled by remote control based on Xbee Pro wireless modules. The testing of the robot prototype proved to be effective in waste collecting and removal. The maximum trash loads that robot can bear is up 16 kg.

An Underwater Image Enhancement Benchmark Dataset and Beyond.

Underwater image enhancement has been attracting much attention due to its significance in marine engineering and aquatic robotics. Numerous underwater image enhancement algorithms have been proposed in the last few years. However, these algorithms are mainly evaluated using either synthetic datasets or few selected real-world images. It is thus unclear how these algorithms would perform on images acquired in the wild and how we could gauge the progress in the field. To bridge this gap, we present the first comprehensive perceptual study and analysis of underwater image enhancement using large-scale real-world images. In this paper, we construct an Underwater Image Enhancement Benchmark (UIEB) including 950 real-world underwater images, 890 of which have the corresponding reference images. We treat the rest 60 underwater images which cannot obtain satisfactory reference images as challenging data. Using this dataset, we conduct a comprehensive study of the state-of-the-art underwater image enhancement algorithms qualitatively and quantitatively. In addition, we propose an underwater image enhancement network (called Water-Net) trained on this benchmark as a baseline, which indicates the generalization of the proposed UIEB for training Convolutional Neural Networks (CNNs). The benchmark evaluations and the proposed Water-Net demonstrate the performance and limitations of state-of-the-art algorithms, which shed light on future research in underwater image enhancement. The dataset and code are available at.

Kinerja dari Prototipe Robot Visual Pengumpul Sampah Perairan dengan Remote Control menggunakan Telemetri

The making of prototype robot waste water collection aims to know the performance itself. The prototype of the Aquatic Waste Collection Robot is designed to float and clean trash in remote controlled waters. The main control drives a series of DC brushless motors to drive while the MG995 servo motor drives a rudder or defender. The device is also equipped with a camera as a medium to see the condition of the robot directly or in real time which will be displayed on the monitor screen. The camera and screen are connected to a telemetry circuit consisting of a transmitter and receiver with a frequency of 5.8 GHz, and a Li-Po battery as a source of robot power supply. The results of prototype testing of water garbage collection robots have been carried out in Embung Langensari Yogyakarta with a depth of 2-3 meters and an area of 5890 m2, the robot can go with a maximum speed of 0.3 m / s with or without the garbage load. Garbage nets used with a capacity of 20 liters. Robots can maneuver to turn right or left with a rudder. In the garbage collection process, this robot can collect relatively small waste

Comprehensive analysis of efficient swimming using articulated legs fringed with flexible appendages inspired by a water beetle

Drag-based swimming is usually accompanied with the shape change of rowing appendages to generate asymmetric force during the power stroke and recovery stroke. To implement this in an aquatic robot, one may actively control the surface area of its legs during the swimming. However, a small sized robot with a limited number of actuators should adjust the surface area of legs in passive manner. For this reason, we proposed a novel articulated leg with flexible appendages inspired by a water beetle. These leg structures were designed to implement an efficient recovery stroke with less resistive force during the recovery stroke, while its surface area was increased again if suitable relaxation time was applied to perform improved power stroke. To identify an optimal leg design, 36 different types were fabricated by changing the passive joint thickness, appendage materials, length, and morphology. Several correlations and dominant parameters were identified, and it was shown that the swimming leg with fixed joint and appendage stiffness cannot always generate the largest torque in all the swimming frequency. Also, a two-dimensional dynamic model was proposed based on an underactuated manipulator, and the model validation was proceeded by comparing with two selected leg designs. In addition, a 5.5 cm long robot with one pair of legs was built to further investigate their locomotory performance. By varying the beating frequency and relaxation time, thorough analysis was addressed in terms of the position, velocity, non-dimensional traveled distance, Strouhal number, and quasi-propulsive efficiency. Here, some important relationships between dimensionless numbers were established. Furthermore, it was found that introducing a relaxation phase between the power stroke and recovery stroke can increase the traveled distance per stroke with slight expense of propulsive efficiency.