Parametric geometric model and shape optimization of airfoils of a biomimetic manta ray underwater vehicle

As a new kind of autonomous underwater vehicle, bionic submersible has many merits such as high efficiency and low costs. In order to obtain such advantages, it is a good way to simulate the shapes of marine animals and apply them to the design of artificial underwater vehicle. In this paper, an optimization system of airfoils is proposed by the improved class-shape-transformation (CST) parameterization method and genetic algorithm (GA). The appearance of a manta-ray-inspired underwater vehicle is rebuilt using the optimal sectional airfoils obtained by the proposed optimization system. Computational simulations are carried out to investigate the hydrodynamic performance of the submersible using the commercial computational fluid dynamics (CFD) code Fluent. The results demonstrate that the maximum thickness of the vehicle increases by 9%, which means the loading capacity is increased. Moreover, the underwater vehicle shows better hydrodynamic performance, and the lift-drag ratio of initial design is increased by more than 10% using the presented optimization system of airfoils

Review of Computational Fluid Dynamics Analysis in Biomimetic Applications for Underwater Vehicles

Biomimetics, which draws inspiration from nature, has emerged as a key approach in the development of underwater vehicles. The integration of this approach with computational fluid dynamics (CFD) has further propelled research in this field. CFD, as an effective tool for dynamic analysis, contributes significantly to understanding and resolving complex fluid dynamic problems in underwater vehicles. Biomimetics seeks to harness innovative inspiration from the biological world. Through the imitation of the structure, behavior, and functions of organisms, biomimetics enables the creation of efficient and unique designs. These designs are aimed at enhancing the speed, reliability, and maneuverability of underwater vehicles, as well as reducing drag and noise. CFD technology, which is capable of precisely predicting and simulating fluid flow behaviors, plays a crucial role in optimizing the structural design of underwater vehicles, thereby significantly enhancing their hydrodynamic and kinematic performances. Combining biomimetics and CFD technology introduces a novel approach to underwater vehicle design and unveils broad prospects for research in natural science and engineering applications. Consequently, this paper aims to review the application of CFD technology in the biomimicry of underwater vehicles, with a primary focus on biomimetic propulsion, biomimetic drag reduction, and biomimetic noise reduction. Additionally, it explores the challenges faced in this field and anticipates future advancements

Energy Based Control System Designs for Underactuated Robot Fish Propulsion

In nature through millions of years of evolution fish and cetaceans have developed fast efficient and highly manoeuvrable methods of marine propulsion. A recent explosion in demand for sub sea robotics, for conducting tasks such as sub sea exploration and survey has left developers desiring to capture some of the novel mechanisms evolved by fish and cetaceans to increase the efficiency of speed and manoeuvrability of sub sea robots. Research has revealed that interactions with vortices and other unsteady fluid effects play a significant role in the efficiency of fish and cetaceans. However attempts to duplicate this with robotic fish have been limited by the difficulty of predicting or sensing such uncertain fluid effects. This study aims to develop a gait generation method for a robotic fish with a degree of passivity which could allow the body to dynamically interact with and potentially synchronise with vortices within the flow without the need to actually sense them. In this study this is achieved through the development of a novel energy based gait generation tactic, where the gait of the robotic fish is determined through regulation of the state energy rather than absolute state position. Rather than treating fluid interactions as undesirable disturbances and `fighting' them to maintain a rigid geometric defined gait, energy based control allows the disturbances to the system generated by vortices in the surrounding flow to contribute to the energy of the system and hence the dynamic motion. Three different energy controllers are presented within this thesis, a deadbeat energy controller equivalent to an analytically optimised model predictive controller, a $H_\infty$ disturbance rejecting controller with a novel gradient decent optimisation and finally a error feedback controller with a novel alternative error metric. The controllers were tested on a robotic fish simulation platform developed within this project. The simulation platform consisted of the solution of a series of ordinary differential equations for solid body dynamics coupled with a finite element incompressible fluid dynamic simulation of the surrounding flow. results demonstrated the effectiveness of the energy based control approach and illustrate the importance of choice of controller in performance

An holistic bio-inspired approach for improving the performance of unmanned underwater vehicles

PhD ThesisThis research, as a part of the Nature in Engineering for Monitoring the Oceans (NEMO) project, investigated bio-inspiration to improve the performance of Unmanned Underwater Vehicles (UUVs). Initially, the capabilities and performance of current AUVs were compared with Biological Marine Systems (BMSs), i.e. marine animals (Murphy & Haroutunian, 2011). This investigation revealed significant superiority in the capabilities of BMSs which are desirable for UUVs, specifically in speed and manoeuvring. Subsequently, an investigation was carried out on BMSs to find means to make use of their superior functionality towards engineering improved UUVs. It was discovered that due to a mismatch between the purpose of each species evolution and the desired mission of an UUV, all desired characteristics are not evident in a single species. Moreover, due to the multi-functionality of biological systems, it is not possible to independently study each configuration. Therefore, an holistic approach to study BMSs as a system with numerous configurations was undertaken. An evolutionary search and selection algorithm was developed to obtain the myriad of biological information and adjust them to engineering needs (Haroutunian & Murphy, 2012). This Optimum System Selector (OSS) was implemented to output aspects of the appropriate design combination for a bio-inspired UUV, based on its specified mission. The OSS takes into account the energetic cost of the proposed combination as well as the trade-off between size, speed and manoeuvrability. Appreciating the uncertainty in existing measured biological data, the developed code was successfully verified in comparison with BMSs data. Energetic cost of transport is a key factor in selecting a design combination based on desired missions. This is key to the accuracy of the algorithm. Therefore, in another essential research theme, a sophisticated study has been carried out on the understanding, calculating, predicting and comparison of various biological and engineered underwater systems energetics (Phillips et al., 2012). The results of the OSS compared with existing AUVs, showed improvements in the overall capabilities. Therefore, this method is an excellent guide to transform complex biological data for the future design and development of UUVs.EPSRC

Control and guidance systems for the navigation of a biomimetic autonomous underwater vehicle

The field of Autonomous Underwater Vehicles (AUVs) has increased dramatically in size and scope over the past three decades. Application areas for AUVs are numerous and varied, from deep sea exploration, to pipeline surveillance to mine clearing. The main concept behind this work was the design and the implementation of a control and guidance system for the navigation of a biomimetic AUV. In particular, the AUV analysed in this project tries to imitate the appearance and approximate the swimming method of an Atlantic Salmon and, for this reason, has been called RoboSalmo

Underwater Robots Part I: Current Systems and Problem Pose

International audienceThis paper constitutes the first part of a general overview of underwater robotics. The second part is titled: Underwater Robots Part II: existing solutions and open issues

Intersection between natural and artificial swimmers: a scaling approach to underwater vehicle design.

Approximately 72% of the Earth’s surface is covered by water, yet only 20% has been mapped [1]. Autonomous Underwater Vehicles (AUVs) are one of the main tools for ocean exploration. The demand for AUVs is expected to increase rapidly in the coming years [2], so there is a need for faster and more energy efficient AUVs. A drawback to using this type of vehicle is the finite amount of energy that is stored onboard in the form of batteries. Science and roboticists have been studying nature for ways to move more efficiently. Phillips et al. [3] presents data that contradicts the idea that fish are better swimmers than conventional AUVs when comparing the energetic cost of swimming in the form of the Cost of Transport (COT). The data presented by Phillips et al. only applies to AUVs at higher length and naval displacement (mass) scales, so the question arises of whether an AUV built at different displacements and length scales is more efficient than biological animals and if current bio-inspired platforms are better than conventional AUVs. Besides power requirements, it is also useful to compare the kinematic parameters of natural and artificial swimmers. In this case, kinematic parameters indicate how fast the swimmer travels through the water. Also, they describe how fast the propulsion mechanism must act to reach a certain swimming speed. This research adopts the approach of Gazzola et al. [4] where the Reynolds number is associated with a dimensionless number, Swim number (Sw) in this case, that has all the kinematic information. A newly developed number that extends the swim number to conventional AUVs is the Propulsion number (Jw), which demonstrates excellent agreement with the kinematics of conventional AUVs. Despite being functionally similar, Sw and Jw do not have a one-to-one relationship. Sw, Jw, COT represent key performance metrics for an AUV, herein called performance criteria, which can be used to compare existing platforms with each other and estimate the performance of non-existent designs. The scaling laws are derived by evaluating the performance of 229 biological animals, 163 bioinspire platforms, and 109 conventional AUVs. AUVs and bio-inspired platforms have scarce data compared with biological swimmers. Only 5% of conventional and 38% of bio-inspired AUVs have kinematic data while 30% of conventional and 18% of bio-inspired AUVs have energetic data. The low amount of performance criteria data is due to the nature of most conventional AUVs as commercial products. Only recently has the COT metric been included in the performance criteria for bio-inspired AUVs. For this reason, the research here formulates everything in terms of allometric scaling laws. This type of formulation is used extensively when referring to biological systems and is defined by an exponential relationship f (x) = axb, where x is a physical parameter of the fish or vehicle, like length or displacement. Scaling laws have the added benefit of allowing comparisons with limited data, as is the case for AUVs. The length and displacement scale (physical scale) must be established before estimating the performance criteria. Scale is primarily determined by the payload needed for a particular application. For instance, surveying the water column in deep water will require different scientific tools than taking images of an oyster bed in an estuary. There is no way to identify the size of an AUV until it is designed for that application, since these scientific instruments each have their own volume, length, and weight. A methodology for estimating physical parameters using computer vision is presented to help determine the scale for the vehicle. It allows accurate scaling of physical parameters of biological and bio-inspired swimmers with only a side and top view of the platform. A physical scale can also be determined based on the vehicle’s overall volume, which is useful when determining how much payload is needed for a particular application. Further, this can be used in conjunction with 3D modeling software to scale nonexistent platforms. Following the establishment of a physical scale, which locomotion mode would be most appropriate? Unlike conventional AUVs that use propeller or glider locomotion, bio-inspired platforms use a variety of modes. Kinematics and energy expenditures are different for each of these modes. For bio-inspired vehicles, the focus will be on the body-caudal fin (BCF) locomotion, of which four types exist: anguilliform, carangiform, thunniform, and ostraciiform. There is ample research on anguilliform and carangiform locomotion modes, but little research on thunniform and ostraciiform modes. In order to determine which locomotion mode scales best for a bio-inspired AUV, this research examines the power output and kinematic parameters for all four BCF modes. In order to achieve this, computational fluid dynamics simulations are performed on a 2D swimmer for all four modes. Overset meshes are used in lieu of body-fitted meshes to increase stability and decrease computational time. These simulations were used to scale output power over several decades of Reynolds numbers for each locomotion mode. Carangiform locomotion was found to be the most energy efficient, followed by anguilliform, thunniform, and ostraciiform. In order to utilize the above scaling laws in designing a novel platform, or comparing an existing one, there must be a unifying framework. The framework for choosing a suitable platform is presented with a case study of two bio-inspired vehicles and a conventional one. The framework begins by determining how the platform can be physically scaled depending on the payload. Based on the physical scale and derived scaling laws, it then determines performance criteria. It also describes a method for relative cost scaling for each vehicle, which is not covered in the literature. The cost scaling is based on the assumption that all payloads and materials are the same. The case study shows that a conventional AUV performs better on all performance criteria and would cost less to build

Marine Gastrobot Final Design Report

The Marine Gastrobot sponsored by Dr. Christopher Kitts of the Cal Poly Center for Applications in Biotechnology was a research and development effort intended to explore the use of microbial fuel cell technology as a power source for underwater robots. Our team Ocean Locomotion succeeded in developing a first iteration of an underwater robotic platform suitable for microbial fuel cell integration. The primary feature of the design is its sinusoidal fin propulsion intended for benthic exploration with limited risk of entanglement. During the course of development, Ocean Locomotion explored the use of low power actuation methods and determined their limited use for underwater locomotion, tested low power boost converter compatibility with microbial fuel cells, and built hardware capable of integration with microbial fuel cells

Sea Mines and Countermeasures: A Bibliography

This compilation was prepared for the Dudley Knox Library, Naval Postgraduate School, Monterey, CA