Bionic Collapsible Wings in Aquatic-aerial Robot

The concept of aerial-aquatic robots has emerged as an innovative solution that can operate both in the air and underwater. Previous research on the design of such robots has been mainly focused on mature technologies such as fixed-wing and multi-rotor aircraft. Flying fish, a unique aerial-aquatic animal that can both swim in water and glide over the sea surface, has not been fully explored as a bionic robot model, especially regarding its motion patterns with the collapsible pectoral fins. To verify the contribution of the collapsible wings to the flying fish motion pattern, we have designed a novel bio-robot with collapsible wings inspired by the flying fish. The bionic prototype has been successfully designed and fabricated, incorporating collapsible wings with soft hydraulic actuators, an innovative application of soft actuators to a micro aquatic-aerial robot. We have analyzed and built a precise model of dynamics for control, and tested both the soft hydraulic actuators and detailed aerodynamic coefficients. To further verify the feasibility of collapsible wings, we conducted simulations in different situations such as discharge angles, the area of collapsible wings, and the advantages of using ground effect. The results confirm the control of the collapsible wings and demonstrate the unique multi-modal motion pattern between water and air. Overall, our research represents the study of the collapsible wings in aquatic-aerial robots and significant contributes to the development of aquatic-aerial robots. The using of the collapsible wings must a contribution to the future aquatic-aerial robot

Physics and applications of squid-inspired jetting

In the aquatic world jet propulsion is a highly successful locomotion method utilized by a variety of species. Among them cephalopods such as squids excel in their ability for high-speed swimming. This mechanism inspires the development of underwater locomotion techniques which are particularly useful in soft-bodied robots. In this overview we summarize existing studies on this topic, ranging from investigations on the underlying physics to the creation of mechanical systems utilizing this locomotion mode. Research directions that worth future investigation are also discussed

Aerial-aquatic robots capable of crossing the air-water boundary and hitchhiking on surfaces.

Many real-world applications for robots-such as long-term aerial and underwater observation, cross-medium operations, and marine life surveys-require robots with the ability to move between the air-water boundary. Here, we describe an aerial-aquatic hitchhiking robot that is self-contained for flying, swimming, and attaching to surfaces in both air and water and that can seamlessly move between the two. We describe this robot's redundant, hydrostatically enhanced hitchhiking device, inspired by the morphology of a remora (Echeneis naucrates) disc, which works in both air and water. As with the biological remora disc, this device has separate lamellar compartments for redundant sealing, which enables the robot to achieve adhesion and hitchhike with only partial disc attachment. The self-contained, rotor-based aerial-aquatic robot, which has passively morphing propellers that unfold in the air and fold underwater, can cross the air-water boundary in 0.35 second. The robot can perform rapid attachment and detachment on challenging surfaces both in air and under water, including curved, rough, incomplete, and biofouling surfaces, and achieve long-duration adhesion with minimal oscillation. We also show that the robot can attach to and hitchhike on moving surfaces. In field tests, we show that the robot can record video in both media and move objects across the air/water boundary in a mountain stream and the ocean. We envision that this study can pave the way for future robots with autonomous biological detection, monitoring, and tracking capabilities in a wide variety of aerial-aquatic environments

A numerical study of fin and jet propulsions involving fluid-structure interactions

Fish swimming is elegant and efficient, which inspires humans to learn from them to design high-performance artificial underwater vehicles. Research on aquatic locomotion has made extensive progress towards a better understanding of how aquatic animals control their flexible body and fin for propulsion. Although the structural flexibility and deformation of the body and fin are believed to be important features to achieve optimal swimming performance, studies on high-fidelity deformable body and fin with complex material behavior, such as non-uniform stiffness distributions, are rare. In this thesis, a fully coupled three-dimensional high-fidelity fluid-structure interaction (FSI) solver is developed to investigate the flow field evolution and propulsion performance of caudal fin and jet propulsion involving body and/or fin deformation. Within this FSI solver, the fluid is resolved by solving unsteady and viscous Navier-Stokes equations based on the finite volume method with a multi-block grid system. The solid dynamics are solved by a nonlinear finite element method. The coupling between the two solvers is achieved in a partitioned approach in which convergence check and sub-iteration are implemented to ensure numerical stability and accuracy. Validations are conducted by comparing the simulation results of classical benchmarks with previous data in the literature, and good agreements between them are obtained. The developed FSI solver is then applied to study the bio-inspired fin and jet propulsion involving body deformation. Specifically, the effect of non-uniform stiffness distributions of fish body and/or fin, key features of fish swimming which have been excluded in most previous studies, on the propulsive performance is first investigated. Simulation results of a sunfish-like caudal fin model and a tuna-inspired swimmer model both show that larger thrust and propulsion efficiency can be achieved by a non-uniform stiffness distribution (e.g., increased by 11.2% and 9.9%, respectively, for the sunfish-like model) compared with a uniform stiffness profile. Despite the improved propulsive e performance, a bionic variable fish body stiffness does not yield fish-like midline kinematics observed in real fish, suggesting that fish movement involves significant active control that cannot be replicated purely by passive deformations. Subsequent studies focus on the jet propulsion inspired by squid locomotion using the developed numerical solver. Simulation results of a two-dimensional inflation-deflation jet propulsion system, whose inflation is actuated by an added external force that mimics the muscle constriction of the mantle and deflation is caused by the release of elastic energy of the structure, suggest larger mean thrust production and higher efficiency in high Reynolds number scenarios compared with the cases in laminar flow. A unique symmetry-breaking instability in turbulent flow is found to stem from irregular internal body vortices, which cause symmetry breaking in the wake. Besides, a three-dimensional squid-like jet propulsion system in the presence of background flow is studied by prescribing the body deformation and jet velocity profiles. The effect of the background flow on the leading vortex ring formation and jet propulsion is investigated, and the thrust sources of the overall pulsed jet are revealed as well. Finally, FSI analysis on motion control of a self-propelled flexible swimmer in front of a cylinder utilizing proportional-derivative (PD) control is conducted. The amplitude of the actuation force, which is applied to the swimmer to bend it to produce thrust, is dynamically tuned by a feedback PD controller to instruct the swimmer to swim the desired distance from an initial position to a target location and then hold the station there. Despite the same swimming distance, a swimmer whose departure location is closer to the cylinder requires less energy consumption to reach the target and hold the position there.Fish swimming is elegant and efficient, which inspires humans to learn from them to design high-performance artificial underwater vehicles. Research on aquatic locomotion has made extensive progress towards a better understanding of how aquatic animals control their flexible body and fin for propulsion. Although the structural flexibility and deformation of the body and fin are believed to be important features to achieve optimal swimming performance, studies on high-fidelity deformable body and fin with complex material behavior, such as non-uniform stiffness distributions, are rare. In this thesis, a fully coupled three-dimensional high-fidelity fluid-structure interaction (FSI) solver is developed to investigate the flow field evolution and propulsion performance of caudal fin and jet propulsion involving body and/or fin deformation. Within this FSI solver, the fluid is resolved by solving unsteady and viscous Navier-Stokes equations based on the finite volume method with a multi-block grid system. The solid dynamics are solved by a nonlinear finite element method. The coupling between the two solvers is achieved in a partitioned approach in which convergence check and sub-iteration are implemented to ensure numerical stability and accuracy. Validations are conducted by comparing the simulation results of classical benchmarks with previous data in the literature, and good agreements between them are obtained. The developed FSI solver is then applied to study the bio-inspired fin and jet propulsion involving body deformation. Specifically, the effect of non-uniform stiffness distributions of fish body and/or fin, key features of fish swimming which have been excluded in most previous studies, on the propulsive performance is first investigated. Simulation results of a sunfish-like caudal fin model and a tuna-inspired swimmer model both show that larger thrust and propulsion efficiency can be achieved by a non-uniform stiffness distribution (e.g., increased by 11.2% and 9.9%, respectively, for the sunfish-like model) compared with a uniform stiffness profile. Despite the improved propulsive e performance, a bionic variable fish body stiffness does not yield fish-like midline kinematics observed in real fish, suggesting that fish movement involves significant active control that cannot be replicated purely by passive deformations. Subsequent studies focus on the jet propulsion inspired by squid locomotion using the developed numerical solver. Simulation results of a two-dimensional inflation-deflation jet propulsion system, whose inflation is actuated by an added external force that mimics the muscle constriction of the mantle and deflation is caused by the release of elastic energy of the structure, suggest larger mean thrust production and higher efficiency in high Reynolds number scenarios compared with the cases in laminar flow. A unique symmetry-breaking instability in turbulent flow is found to stem from irregular internal body vortices, which cause symmetry breaking in the wake. Besides, a three-dimensional squid-like jet propulsion system in the presence of background flow is studied by prescribing the body deformation and jet velocity profiles. The effect of the background flow on the leading vortex ring formation and jet propulsion is investigated, and the thrust sources of the overall pulsed jet are revealed as well. Finally, FSI analysis on motion control of a self-propelled flexible swimmer in front of a cylinder utilizing proportional-derivative (PD) control is conducted. The amplitude of the actuation force, which is applied to the swimmer to bend it to produce thrust, is dynamically tuned by a feedback PD controller to instruct the swimmer to swim the desired distance from an initial position to a target location and then hold the station there. Despite the same swimming distance, a swimmer whose departure location is closer to the cylinder requires less energy consumption to reach the target and hold the position there

Automated Sensing Methods in Soft Stretchable Sensors for Soft Robotic Gripper

A soft robot is made from deformable and flexible materials such as silicone, rubber, polymers, etc. Soft robotics is a rapidly evolving field where the human-robot-interaction and bio-inspired design align. The physical characteristics such as highly deformable material and dexterity make soft robots widely applicable. A soft robotic gripper is a robotic hand that acts like a human hand and grasps any object. The most common applications of soft robotics grippers are gripping and locomotion in sensitive applications where high dynamic and sensitivity are essential. Nowadays, soft robotics grippers are used without any sensing method and feedback as it is crucial to make the output feedback from the gripper. The major drawback of soft robotic grippers is their need for more precision sensing. In traditional robots, we can integrate any sensor to detect the force and orientation of objects. Still, soft robotic grippers rely on the deformation sensing method, where the sensor must be highly flexible and deformable. With a precise sensing method, it is easier to determine the exact position or orientation of the object being gripped, and it limits the application of the soft robotic gripper. Sometimes, soft robots are employed in harsh environments to solve problems. With the sensing feedback, automation may become more reliable and succeed altogether. So, in this research, we have designed and fabricated a soft sensor to integrate with the gripper and to observe the feedback of the gripper. We propose integrated multimodal sensing that incorporates applied pressure and resistance change. The sensor provides feedback when the grippers hold any object, and the output response is the resistance change of the sensor. The liquid metal is susceptible and can respond to low force levels. We presented the 3D design, FEM simulation, fabrication, and integration of the gripper and sensor, and by showing both simulation and experimental results, the gripper is validated for real-time application. FEM simulation simulates behavior, optimizing design and predicting performance. We have designed and fabricated a soft sensor that yields microfluidic channel arrays embedded with liquid metal Galinstan alloy and a soft robotic gripper hand. Different printing processes and characterization results are presented for the sensor and actuator. The fabrication process of the gripper and sensor is adequately described. The gripper output characteristics are tested for bending angle, load test, elongation, and object holding under various applied pressure. Additionally, the sensor was tested for stretchability, linearity and durability, and human gesture integration with the finger, and this sensor can be easily reused/ reproduced. Furthermore, the sensor exhibits good sensitivity concerning different pressure and grasping various objects. Finally, we collected data using this sensor-integrated gripper and trained the dataset using machine learning models for automation. With more data, this can be an autonomous gripper with intelligent sensing methodologies. Moreover, this proposed stretchable sensor can be integrated into any existing gripper for innovative real-time applications

Soft pneumatic actuators: a review of design, fabrication, modeling, sensing, control and applications

Soft robotics is a rapidly evolving field where robots are fabricated using highly deformable materials and usually follow a bioinspired design. Their high dexterity and safety make them ideal for applications such as gripping, locomotion, and biomedical devices, where the environment is highly dynamic and sensitive to physical interaction. Pneumatic actuation remains the dominant technology in soft robotics due to its low cost and mass, fast response time, and easy implementation. Given the significant number of publications in soft robotics over recent years, newcomers and even established researchers may have difficulty assessing the state of the art. To address this issue, this article summarizes the development of soft pneumatic actuators and robots up until the date of publication. The scope of this article includes the design, modeling, fabrication, actuation, characterization, sensing, control, and applications of soft robotic devices. In addition to a historical overview, there is a special emphasis on recent advances such as novel designs, differential simulators, analytical and numerical modeling methods, topology optimization, data-driven modeling and control methods, hardware control boards, and nonlinear estimation and control techniques. Finally, the capabilities and limitations of soft pneumatic actuators and robots are discussed and directions for future research are identified

Controlo de um Veículo Autónomo Submarino Biomimético

O papel dos Unmanned Underwater Vehicles (UUVs) tem vindo a ganhar, progressivamente, um maior destaque nos últimos anos. A sua constante evolução capacitaos da possibilidade de serem utilizados nas mais variadas missões, seja para fins militares ou civis. Apesar das suas capacidades, este tipo de veículos, por recorrerem a uma propulsão através de hélices, faz com que possuam algumas desvantagens, tais como: baixa eficiência energética, baixa manobrabilidade em espaços confinados e altos valores de ruído. Em resposta a estes problemas foram criados um novo tipo de veículos chamados Biomimetics Underwater Vehicles (BUVs), que têm como objetivo o uso de sistemas que repliquem o movimento de animais, colmatando as falhas acima mencionadas. A presente dissertação inclui-se no projeto internacional SABUVIS em parceria com a Escola Naval Polaca, Universidade de Tecnologia da Cracóvia entre outros, e a Faculdade de Engenharia da Universidade do Porto e a Oceanscan como parceiros portugueses. Este projeto tem como objetivo a construção e desenvolvimento de um veículo biomimético capaz de executar operações de Intelligence, Surveillance and Reconnaissance (ISR) através de uma cauda inspirada em peixes com duas secções ou uma cauda inspirada na foca. Assim, o trabalho desenvolvido na presente dissertação visa o desenvolvimento de um controlador para a locomoção do veículo biomimético, usando uma cauda de imitação de um peixe com uma secção e duas barbatanas laterais. Este controlador segue uma arquitetura hierárquica de dois níveis, no controlador de alto nível são implementadas diversas funções, como o veículo ser capaz de se movimentar para um dado ponto ou seguir o movimento de outro veículo. No controlador de baixo nível são calculados os parâmetros de oscilação da cauda principal e das barbatanas laterias tendo em conta os comandos recebidos dos controladores de alto nível. Toda a validação do controlador desenvolvido foi baseada na implementação dos controlos num simulador desenvolvido para um veículo semelhante ao estudado.In recent times, the role of Unmanned Underwater Vehicles (UUVs) has increasingly gained importance. Its constant evolution enables them to be used in the most varied missions, whether for military or civilian purposes. Despite its capabilities, this type of vehicles, due to propulsion through propellers, has some disadvantages, such as: low energy efficiency, low manoeuvrability in confined spaces and high noise values. In response to these problems, a new type of vehicle was created - Biomimetics Underwater Vehicles (BUVs) -, which aim to use systems that replicate the movement of animals, filling those flaws. This dissertation is part of the international project SABUVIS, in partnership with the Polish Naval School, Krakow University of Technology among others, and Faculdade de Engenharia da Universidade do Porto and Oceanscan as Portuguese partners. This project aims to build and develop a biomimetic vehicle capable of performing Intelligence, Surveillance and Reconnaissance (ISR) operations through a fish-inspired tail with two sections or a seal inspired tail. Thus, the work developed in this dissertation aims at the development of a controller for locomotion of the biomimetic vehicle, using a fish-like tail with one section and two pectoral fins. This controller follows a two-level hierarchical architecture: in the high-level controller several functions are implemented, such as the vehicle being able to move to a given point or to follow the movement of another vehicle. In the low-level controller, oscillation parameters of the main tail and side fins are calculated, considering the commands received from the high-level controllers. All the validation of the controller was based on the implementation of the controls in a simulator developed for a vehicle like the one studied

Ocean Noise

Scientific and societal concern about the effects of underwater sound on marine ecosystems is growing. While iconic megafauna was of initial concern, more and more taxa are being included. Some countries have joined in multi-national initiatives to measure, monitor and mitigate environmental impacts of ocean noise at large, trans-boundary spatial scales. Approaches to regulating ocean noise change as new scientific evidence becomes available, but may also differ by country. The OCEANOISE conference series has provided a platform for the exchange of scientific results, management approaches, research needs, stakeholder concerns, etc. Attendees have represented various sectors, including academia, offshore industry, defence, NGOs, consultants and government regulators. The published articles in the Special Issue cover a range of topics and applications central to ocean noise