Biomimetic Autonomous Underwater Vehicle Research Articles

Universal Scaling Laws for Propulsive Performance of Thrust Producing Foils Undergoing Continuous or Intermittent Pitching

High efficiency thrust generating foils are extensively being researched for potential use as thrusters in micro air vehicles and biomimetic autonomous underwater vehicles. Here, we propose a simple reduced order model for prediction of thrust generation attributes of foils that are pitched either continuously or intermittently in a periodic and possibly asymmetric fashion. Our model accounts for the distinct thrust contributions from added mass, leading edge suction, quasi steady and wake terms, all deduced from a rigorous generalization of linearized potential theory to foils undergoing small amplitude multimodal flapping motion. Additionally, the model relies on Bone-Lighthill boundary layer thinning hypothesis to account for the pitching motion induced increase in the drag force exerted on the foil. We derive generic forms of the thrust coefficient for prescribed multimodal pitching motions and specifically in the limit of large reduced frequencies, demonstrate a convergence to rather simplified scaling laws that are functions of just the Reynolds number and Strouhal number based on root mean square of the foil’s trailing edge velocity. Comparisons with previously reported experimental and simulation-based investigations demonstrate that the scaling laws capture the influence of imposed pitch on thrust generation characteristics over a range of pitching waveforms ranging from sinusoidal to square or triangular-shaped waveforms and also waveforms corresponding to intermittent pitching. The generalized relations derived in our work and the asymptotic scaling laws deduced from them are applicable to a wide spectrum of self-propulsion enabling and thrust producing waveforms including the ones that can potentially be employed in burst and coast swimming.

Modeling, Trajectory Analysis and Waypoint Guidance System of a Biomimetic Underwater Vehicle Based on the Flapping Performance of Its Propulsion System

The performance of biomimetic underwater vehicles directly depends on the correct design of their propulsion system and its control. These vehicles can attain highly efficient motion, hovering and thrust by properly moving part(s) of their bodies. In this article, a mathematical modeling and waypoint guidance system for a biomimetic autonomous underwater vehicle (BAUV) is proposed. The BAUV achieves sideways and dorsoventral thunniform motion by flapping its caudal fin through a parallel mechanism. Also, an analysis of the vehicle’s design is presented. A thrust analysis was performed based on the novel propulsion system. Furthermore, the vehicle’s kinematics and dynamic models were derived, where hydrodynamic equations were obtained as well. Computed models were validated using simulations where thrust and moment analysis was employed to visualize the vehicle’s performance while swimming. For the path tracking scheme, a waypoint guidance system was designed to correct the vehicle’s direction toward several positions in space. To accurately obtain waypoints, correction over the propeller’s flapping frequency and bias was employed to achieve proper thrust and orientation of the vehicle. The results from numerical simulations showed how by incorporating this novel propulsion strategy, the BAUV improved its performance when diving and maneuvering based on the dorsoventral and/or sideways configuration of its swimming mode. Furthermore, by designing proper strategies to regulate the flapping performance of its caudal fin, the BAUV followed the desired trajectories. The efficiency for the designed strategy was obtained by comparing the vehicle’s traveled distance and ideal scenarios of straight-line trajectories between targets. During simulations, the designed guidance system presented an efficiency of above 80% for navigation tasks.

Modeling and Control Design for an Autonomous Underwater Vehicle Based on Atlantic Salmon Fish

Biologically inspired autonomous underwater vehicles (AUVs) or biomimetic AUVs are made to replicate the structural and physiological features of aquatic species. Thus, incorporation of its design in AUV modelling provides higher efficiency at low speeds and improves maneuverability and controllability. This paper develops a biomimetic AUV design based on structural parameters and physiology of an adult Atlantic Salmon fish and proposes a robust control scheme for propelling the fins. For the biomimetic model design of AUV, a 3D CAD model is developed using the actual parameters of Atlantic Salmon fish. The hydrodynamic analysis is performed to calculate the effect of different angles of fin orientations on the value of drag and lift coefficients. Further, kinematic analysis of the tail propulsion system is carried out using the Denavit Hartenberg convention in the Matlab®. Based on the obtained modeling parameters of AUV, a robust sliding mode controller is proposed for tracking the desired tail propulsion response using a DC motor under model uncertainties and disturbances. Moreover, the closed-loop asymptotic stability is also guaranteed through Lyapunov theory, which ensures the convergence of system states to the desired angular movement. Lastly, the proposed algorithm is validated using simulation results with comparative performance analysis to illustrate its efficacy.

THE BIOMIMETIC FIN PERFORMANCE EVALUATION FOR AN EFFICIENT AUTONOMOUS UNDERWATER VEHICLE (AUV) TO SUPPORT THE REVOLUTION IN MILITARY AFFAIRS (RMA) IN UNDERWATER DEFENSE

<div><p class="Els-history-head">The world is facing the global trend of Industry 4.0 in the manufacturing sectors. The concept of the Internet of Underwater Thing (IoUT) presents the trends in the underwater region. The Autonomous Underwater Vehicle (AUV) as a data collector and transmitter becomes the central component in the connected system of the IoUT. The efficiency of the platform is crucial to lengthening the range and duration of the mission. The biomimetic method of utilizing the caudal fin propulsion could enhance the efficiency of the small and low-speed AUV. From the defense perspective, there is a concept of Revolution in Military Affairs (RMA) that supports technological modernization for defense purposes. Technically, this study aims to combine the technical aspects of mechanical engineering and the defense concept of RMA in the technological advancement of AUV for the advanced and efficient defense strategy in the underwater region. The evaluations involved numerical simulation with Computational Fluid Dynamics (CFD) method. The simulation results show that the fully tapered flexible fin enhances the efficiency by 25%, while the narrow flexible fin enhances the efficiency by 30%. These results indicate that a flexible tapered fin should be the primary consideration in designing the high-efficiency biomimetic fin. The visualization of the force vectors shows that the flexibility of the fin acts as a thrust vectoring factor that directs more force vectors in the thrust direction. This study supports the RMA concept implementation by technological modernization, such as efficient biomimetic AUV development, to develop doctrines in the State's defense in the underwater region.</p></div>

Thrust and efficiency enhancement scheme of the fin propulsion of the biomimetic Autonomous Underwater Vehicle model in low-speed flow regime

Efficient low-speed Autonomous Underwater Vehicles (AUV) could adopt a propulsion mechanism with a biomimetic approach of caudal fin propulsion. The developments of the biomimetic AUV have very little attention to the systematic enhancement scheme of the fin performance. Therefore, many unclear relations of the parameters in thrust generation and efficiency of the various types of biomimetic fins. The present study proposes a systematic enhancement scheme of the static and dynamic performances of the biomimetic fins in a low-speed regime. This scheme involves rigid, cupping, and flexible single-joint fins of the acceleration-reaction fin mechanism and a high aspect ratio lunate shape two-joint fin of the lift-based fin mechanism. Average net-force and Thrust-to-Power Ratio evaluated the static performance, while the estimated cruising speed characterized the dynamic performance. The present study shows that the flexible single-joint fin improved the maximum values of the rigid fin performance by three times in average net-force, five times in thrust-to-power ratio, and two and a half times in estimated cruising speed. The two-joint fin enhanced the static and dynamic performances of the flexible fin by three times in average net-force, four times in thrust-to-power ratio, and one and a half times in estimated cruising speed. The present study suggests that flexibility has a role as a thrust vectoring factor. Furthermore, the lift-based mechanism in the two-joint fin provides effective and efficient thrust generation. In the present study, the two-joint fin was the effective and efficient fin propulsion mechanism in a low-speed regime.

A Numerical Model for the Analysis of the Locomotion of a Cownose Ray

Abstract Among all aquatic species, mantas and rays swim by flapping their pectoral fins; this motion is similar to other fishes in terms of efficiency, but it gives better maneuverability and agility in turning. The fin's motion is featured by a traveling wave going opposite to the forward motion, producing a force thanks to momentum conservation. This article aims at understanding the swimming dynamics of rays, focusing on energy efficiency. A computational fluid dynamics (CFD) model of the swimming motion of a cownose ray has been implemented in openfoam, simulating the acceleration of the fish from still to the steady-state velocity using an overset mesh. In this analysis, the one degree-of-freedom dynamics of forward swimming is solved together with the fluid velocity and pressure. The effect of frequency and wavelength of fin motion on thrust, power, and velocity has been investigated and an analysis of the vortices in the wake showed has been performed. The energy efficiency of a self-propelled body has been defined in a novel way and it has been calculated for different motion conditions. The results showed that batoid fishes swim with high energy efficiency and that they are a promising source of inspiration for biomimetic autonomous underwater vehicles.

Dynamic Modeling and Control of a Parallel Mechanism Used in the Propulsion System of a Biomimetic Underwater Vehicle

Incorporation of parallel mechanisms inside propulsion systems in biomimetic autonomous underwater vehicles (BAUVs) is a novel approach for motion generation. The vehicle to which the studied propulsion system is implemented presents thunniform locomotion, and its thrust depends mainly on the oscillation from its caudal fin. This paper describes the kinematic and dynamic modeling of a 3-DOF spherical 3UCU-1S parallel robotic system to which the caudal fin of a BAUV is attached. Lagrange formalism was employed for inverse dynamic modeling, and its derivation is detailed throughout this paper. Additionally, the implementation of control strategies to compute forces required to actuate limbs to change platform’s flapping frequencies was developed. Four controllers: classic PD, a feedforward plus feedback PD, an adaptive Fuzzy-PD, and a feedforward plus Fuzzy-PD were compared in different simulations. Results showed that augmenting oscillating frequencies (from 0.5 to 5 Hz) increased the complexity of the path tracking task, where the classic control strategy (i.e., PD) was not sufficient, reaching percentage errors above 9%. Control strategies using feedforward terms combined with adaptive feedback techniques reduced tracking error below 2% even during the presence of external disturbances.

Fish-like shaped robot for underwater surveillance and reconnaissance – Hull design and study of drag and noise

Undulating propulsion is promising solution for underwater vehicles used in subsea security systems, especially due to its low noise, better energetic efficiency, low water turbulence and living animals mimicry. The design of the biomimetic autonomous underwater vehicle (BAUV) for intelligence surveillance and reconnaissance (ISR), built in the SABUVIS project, is presented in the paper. The shape of the vehicle hull was inspired by living fish. Key aspects of the design and construction of BAUV needed to achieve tasks required to be performed by the robot are described. Two research questions are stated in the paper: how big drag forces act on a biomimetic underwater vehicle and how mechanical design influences the noise level generated by the vehicle. To answer these questions vehicle forward velocity, hull drag, added mass and generated noise were investigated. Forces acting on the BAUV hull while being pulled forward and sideways were measured. Noise generated by the vehicle was also measured for two types of propulsors’ drives in order to select those with the lower sound pressure level. Quantitative results of drag and noise obtained in the research are important for designers of mechanical structures of useful, full scale biomimetic underwater robots and their control subsystems.

Modeling and simulation of the intermittent swimming gait with the muscle-contraction model of pre-strains

The muscle-contraction model of pre-strains is employed to study the intermittent swimming gait of a 2D freely swimming fish. The fluid-structure interaction problem of fish swimming is solved with the finite elements method. Benefits of the intermittent swimming and the effects of the duty cycle and the tail swing number in a burst phase are emphasized. The results show that, compared to the steady swimming, a huge energy saving for swimming can be achieved by sacrificing a little speed during the intermittent swimming. Moreover, the fish swimming can be gradually transited from an intermittent mode to the continuous mode by increasing the duty cycle. With a smaller duty cycle, the fish can save more energy to obtain the same swimming velocity. A smaller tail swing number in a burst phase is more helpful to improve the energy utilization rate under the condition of Rduty = 0.5. In addition, the intermittent swimming will have more benefits at the lower and the higher average swimming speeds, and it is very important to have a proper proportion of the velocity bounds for the performance improvement of the intermittent swimming. These conclusions may have direct meanings for the development of biomimetic autonomous underwater vehicles.

Using Neuro\u2013Evolutionary Techniques to Tune Odometric Navigational System of Small Biomimetic Autonomous Underwater Vehicle \u2013 Preliminary Report

Autonomous underwater vehicles (AUVs) are robots that operate in underwater environment and do not need involvement of an operator when performing some tasks. In order to move independently in water environment, AUVs need navigation capabilities, on the one hand, they have to be able to detect obstacles and avoid them, and on the other hand, they also have to know their own position and spatial orientation, at least course. With regard to the orientation, there are many various solutions like inertial systems, inclinometers, magnetic compasses, optical gyro–compasses, whereas, position due to unavailability of GPS requires solutions dedicated to underwater environment such as inertial navigation. To this end, information about spatial orientation and velocity is necessary. When the vehicle is not equipped with a device to measure velocity, e.g. because of small size of the vehicle itself, the only solution is to use odometry, that is, to apply information from the drive to estimate the velocity. The paper presents Odometric Navigational System (ONS) designed for a small biomimetic autonomous underwater vehicle (BAUV) and tuned by means of neuro–evolutionary techniques. To verify system performance, data from the real BAUV were applied.

Design, Construction, and Modeling of a BAUV with Propulsion System Based on a Parallel Mechanism for the Caudal Fin

Traditional propulsion systems for autonomous underwater vehicles (AUVs) have several deficiencies, such as the invasion of the aquatic environment through the generation of noise and damage to the ecosystem, higher energy consumption, and a unidirectional thruster vector. The last characteristic constrains the maneuverability of the vehicle. This paper proposes a 3-DOF spherical 3 universal–cylindrical–universal and 1 spherical joint (3UCU-1S) parallel mechanism coupled to an artificial caudal fin to produce a vectored thruster for a biomimetic AUV (BAUV). First, the design and construction of the prototype are described. Then, the kinematics and dynamics analysis of the parallel mechanism is presented. Finally, a motion study shows the types of movements that can be achieved with the mechanism to perform flapping of the caudal fin in different directions.

Tunas as a high-performance fish platform for inspiring the next generation of autonomous underwater vehicles

Tunas of the genus Thunnus are a group of high-performance pelagic fishes with many locomotor traits that are convergently shared with other high-performance fish groups. Because of their swimming abilities, tunas continue to be an inspiration for both comparative biomechanics and the design of biomimetic autonomous underwater vehicles (AUVs). Despite the strong history of studies in tuna physiology and current interest in tuna biomechanics and bio-inspired design, we lack quantitative data on the function of many features of tunas. Here we present data on the morphology, behavior, and function of tunas, focusing especially on experimentally examining the function of tuna lateral keels, finlets, and pectoral fins by using simple physical models. We find that both triangular lateral keels and flexible finlets decrease power requirements during swimming, likely by reducing lateral forces and yaw torques (compared to models either without keels or with rectangular keels, and models with stiff finlets or strip fins of equal area, respectively). However, both triangular keels and flexible finlets generate less thrust than other models either without these features or with modified keels or finlets, leading to a tradeoff between power consumption and thrust. In addition, we use micro computed tomography (µCT) to show that the flexible lateral keels possess a lateral line canal, suggesting these keels have a sensory function. The curved and fully-attached base of tuna pectoral fins provides high lift-to-drag ratio at low angles of attack, and generates the highest torques across speeds and angles of attack. Therefore, curved, fully-attached pectoral fins grant both better gliding and maneuvering performance compared to flat or curved, partially-attached designs. We provide both 3D models of tuna morphology derived from µCT scans and conclusions about the performance effects of tuna-like features as a resource for future biological and engineering work for next-generation tuna-inspired AUV designs.

Neural collision avoidance system for biomimetic autonomous underwater vehicle

Autonomous underwater vehicles (AUVs) are underwater robots which are able to perform certain tasks without the help of a human operator. The key skill of each AUV is the capability to avoid collisions. To this end, appropriate devices and software are necessary with the potential to detect obstacles and to take proper decisions from the point of view of both the task and safety of the vehicle. The paper presents a neural collision avoidance system (NCAS) designed for the biomimetic autonomous underwater vehicle (BAUV). The NCAS is a component of the path following and collision avoidance system (PFCAS), which as the name implies is responsible for safely leading the vehicle along a desired path with collision avoidance. The task of NCAS is to make decisions regarding vehicle maneuvers in the horizontal plane, but only in the close proximity of the obstacles. It is implemented as an evolutionary artificial neural network designed by means of a neuro-evolutionary technique called assembler encoding with evolvable operations (AEEO). The paper outlines operation and construction of the BAUV as well as the PFCAS, the role of the NCAS in the entire system, and briefly presents AEEO as well as reporting on the experiments performed in simulation.

Report on Research with Biomimetic Autonomous Underwater Vehicle — Navigation and Autonomous Operation

Abstract The paper presents the second part of the final report on all the experiments with biomimetic autonomous underwater vehicle (BAUV) performed within the confines of the project entitled ‘Autonomous underwater vehicles with silent undulating propulsion for underwater ISR’, financed by Polish National Center of Research and Development. The report includes experiments on the swimming pool as well as in real conditions, that is, both in a lake and in the sea. The tests presented in this part of the final report were focused on navigation and autonomous operation.

Report on Research with Biomimetic Autonomous Underwater Vehicle — Low Level Control

Abstract The paper presents the first part of the final report on all the experiments with biomimetic autono-mous underwater vehicle (BAUV) performed within the confines of the project entitled ‘Autonomous underwater vehicles with silent undulating propulsion for underwater ISR’, financed by Polish National Center of Research and Development. The report includes experiments in the swimming pool as well as in real conditions, that is, both in a lake and in the sea. The tests presented in this part of the final report were focused on low-level control.

Correction of Navigational Information Supplied to Biomimetic Autonomous Underwater Vehicle

Abstract In order to autonomously transfer from one point of the environment to the other, Autonomous Underwater Vehicles (AUV) need a navigational system. While navigating underwater the vehicles usually use a dead reckoning method which calculates vehicle movement on the basis of the information about velocity (sometimes also acceleration) and course (heading) provided by on-board devicesl ike Doppler Velocity Logs and Fibre Optical Gyroscopes. Due to inaccuracies of the devices and the influence of environmental forces, the position generated by the dead reckoning navigational system (DRNS) is not free from errors, moreover the errors grow exponentially in time. The problem becomes even more serious when we deal with small AUVs which do not have any speedometer on board and whose course measurement device is inaccurate. To improve indications of the DRNS the vehicle can emerge onto the surface from time to time, record its GPS position, and measure position error which can be further used to estimate environmental influence and inaccuracies caused by mechanisms of the vehicle. This paper reports simulation tests which were performed to determine the most effective method for correction of DRNS designed for a real Biomimetic AUV.

High–Level Control System for Biomimetic Autonomous Under-water Vehicle

Usually, a rough software architecture designed for a robot can be can be shortly presented in the form of layers. The lowest layer is responsible for direct control of the hardware, i.e. engines, energy system, sensors, navigation devices, etc. A next layer is a low–level control which knows how to use the hardware in order to achieve a desired state of the robot, e.g. to stay on a desired course. And the last layer, the layer which is the nearest to the human–operator, is a high–level control which decides how to use the low–level control and sometimes also individual pieces of the hardware to achieve predefined objectives. The paper describes architecture, tasks and operation of the high–level control system (HLCS) designed for Biomimetic Autonomous Underwater Vehicle (BAUV).

The Positioning Accuracy of BAUV Using Fusion of Data from USBL System and Movement Parameters Measurements

The article presents a study of the accuracy of estimating the position coordinates of BAUV (Biomimetic Autonomous Underwater Vehicle) by the extended Kalman filter (EKF) method. The fusion of movement parameters measurements and position coordinates fixes was applied. The movement parameters measurements are carried out by on-board navigation devices, while the position coordinates fixes are done by the USBL (Ultra Short Base Line) system. The problem of underwater positioning and the conceptual design of the BAUV navigation system constructed at the Naval Academy (Polish Naval Academy—PNA) are presented in the first part of the paper. The second part consists of description of the evaluation results of positioning accuracy, the genesis of the problem of selecting method for underwater positioning, and the mathematical description of the method of estimating the position coordinates using the EKF method by the fusion of measurements with on-board navigation and measurements obtained with the USBL system. The main part contains a description of experimental research. It consists of a simulation program of navigational parameter measurements carried out during the BAUV passage along the test section. Next, the article covers the determination of position coordinates on the basis of simulated parameters, using EKF and DR methods and the USBL system, which are then subjected to a comparative analysis of accuracy. The final part contains systemic conclusions justifying the desirability of applying the proposed fusion method of navigation parameters for the BAUV positioning.

Coordination of Multiple Biomimetic Autonomous Underwater Vehicles Using Strategies Based on the Schooling Behaviour of Fish

Biomimetic Autonomous Underwater Vehicles (BAUVs) are Autonomous Underwater Vehicles (AUVs) that employ similar propulsion and steering principles as real fish. While the real life applicability of these vehicles has yet to be fully investigated, laboratory investigations have demonstrated that at low speeds, the propulsive mechanism of these vehicles is more efficient when compared with propeller based AUVs. Furthermore, these vehicles have also demonstrated superior manoeuvrability characteristics when compared with conventional AUVs and Underwater Glider Systems (UGSs). Further performance benefits can be achieved through coordination of multiple BAUVs swimming in formation. In this study, the coordination strategy is based on the schooling behaviour of fish, which is a decentralized approach that allows multiple AUVs to be self-organizing. Such a strategy can be effectively utilized for large spatiotemporal data collection for oceanic monitoring and surveillance purposes. A validated mathematical model of the BAUV developed at the University of Glasgow, RoboSalmon, is used to represent the agents within a school formation. The performance of the coordination algorithm is assessed through simulation where system identification techniques are employed to improve simulation run time while ensuring accuracy is maintained. The simulation results demonstrate the effectiveness of implementing coordination algorithms based on the behavioural mechanisms of fish to allow a group of BAUVs to be considered self-organizing.

Architecture of Software for Biomimetic Autonomous Underwater Vehicle

Autonomous underwater vehicles are vehicles that are entirely or partly independent of human decisions. In order to obtain operational independence, the vehicles have to be equipped with a specialized software. The main task of the software is to move the vehicle along a trajectory with collision avoidance. Moreover, the software has also to manage different devices installed on the vehicle board, e.g. to start and stop cameras, sonars etc. In addition to the software embedded on the vehicle board, the software responsible for managing the vehicle on the operator level is also necessary. Its task is to define mission of the vehicle, to start, stop the mission, to send emergency commands, to monitor vehicle parameters, and to control the vehicle in remotely operated mode.The paper presents architecture of the software designed for biomimetic autonomous underwater vehicle (BAUV) that is being constructed within the framework of the scientific project financed by Polish National Center of Research and Development.