Design Of Autonomous Underwater Vehicle Research Articles

Rapid data-driven individualised shape design of AUVs based on CFD and machine learning

ABSTRACT The shape design of autonomous underwater vehicles (AUVs) has an essential influence on their hydrodynamic performance. In this study, a data-driven approach is proposed based on computational fluid dynamics (CFD) and machine learning to efficiently design the hydrodynamic shape of AUVs with different sailing velocities, angles of attack (AOAs) and volumes. Based on the data-driven approach, a shape optimisation design for AUVs is established. Moreover, the variation of optimal shape with the design constraints of AOA, velocity and volume is also explored, and the results prove that a relatively larger body with a sharper head is more beneficial for the Myring shape AUVs sailing with a higher velocity and a larger AOA. The results of CFD calculations and those of the data-driven approach are compared, and a circulating flume test is carried out to prove the reliability of CFD method. The comparison verifies the reliability of the optimisation result.

Design and extensibility analysis of a variable buoyancy system for small autonomous underwater vehicles

PurposeA switching depth controller based on a variable buoyancy system (VBS) is proposed to improve the performance of small autonomous underwater vehicles (AUVs). First, the requirements of VBS for small AUVs are analyzed. Second, a modular VBS with high extensibility and easy integration is proposed based on the concepts of generality and interchangeability. Subsequently, a depth-switching controller is proposed based on the modular VBS, which combines the best features of the linear active disturbance rejection controller and the nonlinear active disturbance rejection controller.Design/methodology/approachThe controller design and endurance of tiny AUVs are challenging because of their low environmental adaptation, limited energy resources and nonlinear dynamics. Traditional and single linear controllers cannot solve these problems efficiently. Although the VBS can improve the endurance of AUVs, the current VBS is not extensible for small AUVs in terms of the differences in individuals and operating environments.FindingsThe switching controller’s performance was examined using simulation with water flow and external disturbances, and the controller’s performance was compared in pool experiments. The results show that switching controllers have greater effectiveness, disturbance rejection capability and robustness even in the face of various disturbances.Practical implicationsA high degree of standardization and integration of VBS significantly enhances the performance of small AUVs. This will help expand the market for small AUV applications.Originality/valueThis solution improves the extensibility of the VBS, making it easier to integrate into different models of small AUVs. The device enhances the endurance and maneuverability of the small AUVs by adjusting buoyancy and center of gravity for low-power hovering and pitch angle control.

A Novel Squid-Inspired AUV Design: Revolutionizing Coral Reef Preservation Through CFD and Experimental Insights into Drag and Maneuverability

This study focuses on conceptualizing and optimizing an advanced bionic robotic solution to surmount the limitations of current observational vehicles in coral reef conservation. Human divers are traditionally subjected to physiological challenges, while current robotic alternatives grapple with operational impediments, including anthropogenic marine disturbances. Utilizing advanced robotics tailored for marine ecosystems with intricate topologies and fragile corals, this study aims to enhance conservation precision in the face of climatic shifts and marine pollution from anthropogenic activities.This paper develops a squid-inspired Autonomous Underwater Vehicle (AUV), whose behavior is then examined and improved utilizing both experiments and Computational Fluid Dynamics.(CFD). The governing equations considered here are the incompressible Reynolds-Averaged Navier-Stokes (RANS) with an iterative solver for both the pressure-Poisson and momentum equations. Apart from CFD analysis, a prototype was assembled and experimentally tested to validate the CFD outcomes and assess the lift from its bionic rudders. The maneuverability is optimized through careful designs and parameter studies of several features.A head length is determined to balance viscous and pressure drag while achieving the least total drag in the AUV design. Additionally, a disk is introduced at the AUV’s front, which reduces fluid contact, thereby decreasing the viscous drag. While this modification slightly increased pressure drag, it yielded an overall reduction in total drag. Experimental observations confirmed a propulsion speed and underscored the necessity for maximizing rudder extension.The developed AUV’s squid-like design, optimized via CFD, ensures drag reduction by 5.34% and energy efficiency. By mimicking squid dynamics, disturbances to marine biota are minimized. The incorporation of bionic fins, empirically fine-tuned, enhances the AUV’s agility. These attributes establish it as an exceptional prototype, setting a precedent for future coral reef monitoring systems and augmenting conservation strategies.

Nonlinear dynamics of novel flight-style autonomous underwater vehicle with bow wings, Part I: ASE and CFD based estimations of hydrodynamic coefficients, Part II: Nonlinear dynamic modeling and experimental validations

Accurate dynamic modeling is essential for precise prediction of six degrees-of-freedom (6-DOF) motion and model-based controller design of an autonomous underwater vehicle (AUV). The accuracy of dynamic model of an AUV largely depends upon the precise estimation of hydrodynamic coefficients. Accordingly, to establish the dynamic model based on ASE-estimated hydrodynamic coefficients of the novel flight-style AUV and experimental validations, the study is presented in two parts (Part I: ASE and CFD based estimations of hydrodynamic coefficients and Part II: Nonlinear dynamic modeling and experimental validations).Part I: In this part complete set of nonlinear hydrodynamic coefficients including, added mass, drag, and lift forces and moment coefficients are estimated using ASE technique, which is specifically developed to accurately comprehend the novel AUV design including, AUV hull, fixed wings, control fins, and appendages. Additionally, an improved ASE approach is also proposed to estimate cross flow drag force coefficients. In proposed improved ASE technique, (Cdc) in mathematical formulation is taken from the experimental results of 3D flow past over circular cylinder instead of 2D, as followed previously to estimate the nonlinear cross-flow drag force and moment coefficients (Yvv,Zww,Mww,Nvv,Yrr,Zqq,Mqq&Nrr). The proposed ASE technique is verified and validated in two stages: first, by comparing the ASE-estimated results with CFD-based estimations, and second, by investigating the 6-DOF motion response of the AUV. When compared ASE-estimations with the CFD results for the cross-flow drag force and moment coefficients, the proposed ASE technique has shown a significant improvement (approximately 20%) over the previously employed ASE method. The ASE-estimated results are validated through 6-DOF motion response of AUV during free-running underwater experiments, provided in ‘Part II’. Overall, the proposed ASE technique is considered more effective, direct, and less costly in terms of time and computational efforts, compared to CFD-based or experimental-based estimations of hydrodynamic coefficients of AUVs, particularly torpedo-shaped AUVs.Part II: This part presents a nonlinear dynamic model for a newly designed torpedo-shaped flight-style AUV having complex bow and stern fixed wings and control fins configuration. The model includes precise mathematical formulations to accurately represent the physics of the AUV and underwater environment in terms of hydrodynamic derivatives such as added mass, drag, and lift forces and moment coefficients. These coefficients have been estimated using an ASE method provided in ‘Part I’. The 6-DOF motion response of the AUV has been simulated in both horizontal and vertical planes which includes, zigzag yaw, circle, zigzag pitch, and spiral maneuvers. The lift generated by the bow and stern control fins has been investigated both separately and collectively, especially during complex spiral ascending maneuvers. Moreover, improved ASE technique for cross flow drag coefficients has also been validated through 6-DOF free-running underwater experiments of AUV and insights on impact of cross flow drag coefficients on 6-DOF motion response of AUV has also been provided. Overall, the comparison between the simulated AUV motion and free-running underwater experiments demonstrated consistency, thereby validating the accuracy of the nonlinear dynamic modeling, ASE-based hydrodynamic coefficient predictions, and effectiveness of the newly designed flight-style AUV for underwater operations.

Model-Based Digital Overall Integrated Design Method of AUVs

Autonomous underwater vehicles (AUVs) have the characteristics of a high performance, a complex coupling mechanism, a compact, complex system composition, as well as high requirements for design constraints, quality, and reliability. In the traditional overall design process, numerous design tools and software programs are used, which results in poor model data sharing, a lack of uniqueness and synchronization between system levels, and difficulty in process tracing. Moreover, it is challenging to meet the technical requirements for close collaboration and rapid iteration of multiple positions. To address the aforementioned limitations, this study proposes a digital overall integrated design method for the design and simulation integration of AUVs and defines a unified architecture and interface for system-level design simulation models, thus solving the interoperability and consistency problems in multiple tools and models. In addition, a model-based AUV system integration design verification method that combines different processes, specifications, and models is designed, and software similar to Cameo, which can provide technical means for system-level integrated design and achieve rapid modeling and simulation verification based on system design solutions, is developed. Finally, a practical system design is conducted by taking specific AUV equipment as a research object, and the proposed methods are compared with traditional methods to prove the improvement effect of the technical route on the equipment and development efficiency.

Multi-objective shape optimization of autonomous underwater vehicle by coupling CFD simulation with genetic algorithm

In this paper, a new method of multi-objective optimization of the shape parameters was proposed for the Autonomous Underwater Vehicle (AUV) with both towed and self-propelled, aiming to reduce drag and enhance motion stability during navigation. In this study, the hydrodynamics calculation of AUV was conducted by CFD method covering a wide range of Reynolds number between 105 and 107, and the optimization was performed by NSGA-II multi-objective optimization algorithm. Prior to deploying the optimization process, a sample library was created using the Latin hypercube sampling method to construct the Kriging approximation model. Thereafter, the model was used as the NSGA-II multi-objective optimization function, in which the range of design variables was considered to obtain the Pareto optimal solution. Furthermore, we also introduce and discuss the Pareto optimal points with special characteristics. In addition, the objective function values of these four optimal points were compared with the results of the initial model. The results showed that the drag at the four optimal points were reduced by 12.07%, 11.59%, 10.98% and 7.94%, respectively, and the overturning moments were reduced by 1.96%, 7.38%, 12.73% and 14.08%, respectively. The proposed multi-objective optimization method optimizes the shape of AUV effectively and provides valuable guidance for the design of AUV.

Generating high-efficiency swimming kinematics using hydrodynamic eigenmode decomposition

This paper explores the use of hydrodynamic eigenmode decomposition as a means of generating optimal swimming kinematics of slender three-dimensional bodies. The eigenvectors of the unsteady hydrodynamic system are used as basis functions for the response to external forcing, such as perturbations generated by the deformation of the body. Exploiting the orthogonality of the modes, we show that swimming according to a single appropriately selected hydrodynamic eigenmode results in high-efficiency swimming. To demonstrate this result, we use an inviscid three-dimensional vortex lattice model to investigate the hydrodynamic eigenmodes of a selection of geometries. We find that for all of the body geometries tested, hydrodynamic efficiency far exceeding that of pure heaving or pitching can be achieved. All eigenmodes tested produce high-efficiency motion, as long as the beat frequency is higher than the mode's “cut-in” frequency for thrust generation. The eigenmodes show qualitative similarity to swimming patterns observed in nature and also correspond well to the existing classifications of undulatory and oscillatory swimming. This study demonstrates that the hydrodynamic eigenmode analysis can generate high-efficiency swimming kinematics based only on information about the body and wake geometry, and as such, this method has significant potential for further development and application to autonomous underwater vehicle design.

The hydrodynamic characteristics of autonomous underwater vehicles in rotating flow fields

In this article, the hydrodynamic characteristics of Autonomous Underwater Vehicles (AUVs) are investigated and analyzed under the influence of rotating flow fields, which were generated in a recirculating water tank via a rotating propeller. Initially, experiments were carried out to measure flow field variables and quantities of Interest across the AUV in the presence of the rotating propeller while varying the rotational speed and the extent of rotational flow strength. The flow field across the AUV was measured using an Acoustic Doppler Velocimeter (ADV). These measured turbulent flow statistics were used to validate the Reynolds Stress Model (RSM) based numerical predictions in a commercial CFD solver. After preliminary validation of the turbulent flow statistics with the numerical predictions, a series of numerical simulations were performed to investigate the effect of the rotational flow field of the propeller on the drag, skin friction, and pressure coefficients of the AUV. The operating speed and location of the propeller were also varied to check their effects on the hydrodynamic performance of the AUV. The results provided in this article will be useful for the design optimization of AUVs cruising in shallow water where the flow is highly rotational because of wave-current interactions. Additionally, the results and analysis are relevant to study the design and operation of AUVs that have to operate in a group of unmanned underwater vehicles or near submarines and ships where the flow field is highly complex and such rotational effects are present.

Design of AUVs based on 3D coils positioning and distributed base station control for nuclear spent fuel pools

An underwater magnetic induction positioning and communication system and an energy-efficient distributed control algorithm for underwater base stations are proposed in this paper. The positioning and communication system consists of a number of base stations and an Autonomous Underwater Vehicle (AUV) equipped with three-axis source coils respectively. The AUV receives this signal and based on its amplitude and phase information is able to locate the AUV and communicate with the base station. Due to the short positioning distance of magnetic induction positioning technology, a large number of base stations need to be installed underwater, which puts high demands on the control of the base stations. In this paper, an energy-efficient distributed control algorithm for underwater base stations is proposed to enable the AUV to meet the operational requirements while minimizing the total energy consumption of the base station. According to the simulation results, the design solves the problem that traditional underwater positioning and communication equipment cannot work stably for long periods of time in a high radiated environment, with a positioning error of no more than 10 cm within a preset operating range, and the algorithm proposed in this paper is able to reduce energy wastage by about 20%.

Feasibility analysis of a wave powered autonomous underwater vehicle

An autonomous underwater vehicle (AUV) powered by renewable energy would enable it to extend endurance and forward presence with no logistics tail for fuel. A wave powered concept AUV is proposed and analyzed for this purpose. The AUV is in a torpedo shape and employs a fully hull-encapsulated mass-spring-damper system as its power take-off (PTO) unit. While in the recharging mode, the AUV surfaces and converts wave energy for electricity. Considering the AUV of a common size, our analysis indicates that resonance of the AUV and/or its PTO, to be excited by ocean waves, becomes impossible in typical ocean conditions. Then by making the AUV almost fully submerged to eliminate its intrinsic resonant nature and by applying some realistic constraints, the AUV’s power generation capability without resonance is characterized. Our simulation results show that the AUV is still capable of generating power at a decent level in a wide range of the wave frequency upon optimization. Some guiding principles have been established for AUV design of this type.

Jaya optimization algorithm implemented on a new novel design of 6-DOF AUV body: a case study

The novel Jaya Optimization Algorithm (JOA) was utilized in this research to evaluate the efficiency of a new novel design of Autonomous Underwater Vehicle (AUV). The Three Proportional Integral Derivative (PID) controllers were used to obtain the optimum output for the AUV Trajectory, which can be considered as a main side of the research for solving the AUV Performance. The optimization technique has been developed to solving the motion model of the AUV in order to reduce the rotations of trajectory for the AUV 6-DOF Body in the axis’s in x, y and z for the overall positions, velocity were measured in 50 seconds as the velocity compared with the simulated time, and to execute the optimum output for the dynamic kinematics model based on the Novel Euler-6 DOF AUV Body Equation implemented on MATLAB R2021a Version.

Design and Implementation of Lightweight AUV With Multisensor Aided for Underwater Intervention Tasks

Autonomous underwater vehicles (AUVs) are commonly used to conduct complex underwater tasks, such as marine infrastructure overhaul and maintenance, environmental monitoring, oceanographic mapping, and organism capture. These tasks require the ability of an AUV to perform autonomous navigation, especially when communication is limited in the underwater environment. This brief developed a new type of lightweight intervention AUV for autonomous navigation using data from multiple inertial sensors, where multi-sensor error state Kalman filter schemes are preferable to standard Kalman Filters in terms of the AUV’s motion estimates. Concerning target recognition, a color restoration method is provided for degraded underwater images and a You Only Look Once strategy is combined with topological analysis for object detection. In addition, the proposed design is robust in terms of its software components and mechanical structure, which provides a feasible platform for AUV’s secondary development. Experiments of surveying and object manipulation conducted in underwater environments demonstrate the functionality of the entire system and its potential applications in the fields of science and industry.

Design, Modeling, Control, and Experiments for Multiple AUVs Formation

The multiple autonomous underwater vehicle (AUV) formation plays an important role in underwater missions, such as oceanographic sampling and water pollution monitoring. This article presents the mechatronic design, modeling, formation control, and experiments of multiple AUVs. The structure of the AUV and a simplified mathematical model for tracking control are described. To achieve formation control, we formulate a control framework for the multiple AUVs. The upper layer is a formation algorithm based on a novel leader-follower control law. The bottom layer is a dynamic controller based on active disturbance rejection control (ADRC). The formation algorithm is in charge of calculating reference values for the followers to maintain a desired pattern with the leader. The stability and convergence properties of the algorithm have been analyzed using the Lyapunov stability method. Meanwhile, an ADRC approach-based dynamic controller is established to track the reference values. Numerical simulations are carried out to analyze formation control and validate the control framework. The multiple AUVs can switch and maintain the formation between the one-line pattern and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> pattern. Finally, extensive formation field experiments involving the one-line pattern and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> pattern show the good motion ability of the self-designed AUVs and also verify the feasibility of the proposed control approach. Note to Practitioners—The motivation of the article is to design a practical formation control approach for multiple AUVs and verify the control approach in the field. Although there have been a lot of prior research studies on multiple AUVs, how to design a formation control approach subjected to communication bandwidth constraints and how to develop multiple AUVs and verify the effectiveness of the control method in the field are worthy of intense investigation. Hence, this article builds the mechatronic design and dynamic model of the AUV and proposes a novel leader-follower formation control approach based on the dynamics and kinematic model of AUV. Besides, the stability of formation control for multiple AUVs is proven by the Lyapunov theorem. Multiple AUVs can switch and maintain formation between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> pattern and one-line pattern with a smaller error. Finally, the performance of the proposed formation control strategy is experimentally verified using three self-made AUVs inside a large reservoir. The proposed method is suitable for multiple AUVs missions involving underwater surveillance, underwater pipeline inspection in the ocean.

The effects of head form on resistance performance and flow characteristics for a streamlined AUV hull design

Autonomous underwater vehicles (AUVs) are submersible vehicles that can carry out a wide range of tasks, depending on their design. The design of AUVs has a significant impact on their hydrodynamic performance. A streamlined AUV hull form can be divided into three main parts: the head, middle body, and tail. In this study, we investigated the effects of head form on resistance performance and flow characteristics for an AUV hull. Myring equations are used in the creation of the AUV hull profile, and the exponential parameter (n) is considered to diversify the head forms. Computational fluid dynamics (CFD) simulation software ANSYS Fluent is used to carry out the RANS simulations for the investigation. The analyses are carried out within a range of 0.3 m/s to 1.4 m/s flow velocities to consider the effect of the Reynolds number. The head forms that are most effective in terms of drag and have the greatest volume are evaluated and suggested. Essential design characteristics such as velocity-coloured streamlines, pressure and skin friction distribution, wake area and drag coefficients are shown and discussed. The findings can be used as a guideline to minimize resistance and enhance the design of AUV models.

The effects of caudal fin's bending stiffness on a self-propelled carangiform swimmer

The hydrodynamic performance of a self-propelled carangiform swimmer with a flexible caudal fin in the absence of a free stream is numerically investigated, where the fin's dimensionless bending stiffness varies from 10−3 to 150. It reveals that large flexibility of the caudal fin has a negative impact on the propulsion and moderate rigidity is found to increase the hydrodynamic performance. Two different vortex configurations are observed at low and high bending stiffnesses: (i) reverse Bénard–von Kármán (rBvK) vortex configuration and (ii) deflected reverse Bénard–von Kármán wake with the secondary vortex street, respectively. With the increase in bending stiffness, the thrust-producing part switches from the swimmer body to the caudal fin corresponding to the switch of the vortex configuration. Furthermore, the thrust and drag productions are examined. As the bending stiffness increases, the “active portion” of the caudal fin provides more kinetic energy to the wake flow. It is found that the deflected rBvK is induced by the vortical strength imbalance of two adjacent vortices, and the secondary vortex street is formed by the large strain between the primary vortex and the secondary vortex street. Meanwhile, the dynamic mode decomposition analysis indicates that the dominant mode of the dynamic flow field is the excited frequency resonant mode and the inherent frequency of the secondary vortex street is the same as the undulatory frequency. These results shed new light onto the role of the flexible caudal fin in self-propelled biological systems and may provide some inspirations to autonomous underwater vehicle design.

Research on accurate modeling of hydrodynamic interaction forces on AUVs operating in tandem

The hydrodynamic interaction force between autonomous underwater vehicles (AUVs) operating in tandem can adversely affect the hydrodynamic prediction of individual AUVs and the formation control of the tandem fleet. Accurate modeling of hydrodynamic interaction forces is crucial to the model-based controller design of AUVs. In this paper, we innovatively propose a modeling method that can describe the hydrodynamic interaction relationship accurately and continuously (when the spacing between adjacent AUVs changes). First, an accurate hydrodynamic model for individual AUVs in tandem fleets is established by modifying the typical model through the consideration of memory effects. Second, a model of hydrodynamic interaction forces is derived by subtracting hydrodynamic forces acting on a single AUV operating independently from those acting on an AUV operating in tandem. To enable this model to continuously describe the hydrodynamic interaction relationship when the spacing changes, this model is further derived by taking the spacing as an independent variable based on the parameter conversion method. Finally, planar motion mechanism (PMM) tests are carried out using the computational fluid dynamics (CFD) method to verify the accuracy and continuity of the proposed modeling method. The results show that compared with the typical model, the average error of hydrodynamic forces predicted by the proposed model is reduced by 5.36%, which verifies the feasibility and effectiveness of the proposed modeling method.

Design, analysis, and testing of Petrel acoustic autonomous underwater vehicle for marine monitoring

Autonomous underwater vehicles (AUVs) provide a unique and cost-effective platform for conducting ocean acoustic measurements and surveys such as marine mammal monitoring, extensive area seafloor topography survey, and fish stock survey. The small and medium-sized AUVs combine load-carrying capability, motion, and range and allow for timescale observations that are difficult to achieve with traditional acoustic observation platforms. However, self-noise is still an unavoidable challenge for AUVs when applied in passive acoustic monitoring. This paper presents the acoustic observation application of the Petrel acoustic AUV in marine monitoring. The layout design of a Petrel acoustic AUV and acoustic sensor integration are described in detail, and the self-noise characteristics of Petrel acoustic AUVs are evaluated by simulation and testing. The results showed that the self-noise level of Petrel acoustic AUVs is effectively controlled with its optimized design, and the maximum noise of the propulsion system is only 75 dB in the low-frequency band. Therefore, the Petrel acoustic AUV can be used as an ideal acoustic observation platform to carry out diverse observation tasks. Finally, a solution of fixed-depth motion is proposed to address the problem that frequent attitude adjustment affects the quality of acoustic data in fixed-depth navigation. According to a sea trial in the South China Sea, the method can significantly reduce the attitude adjustment frequency and, thus, provide an ideal environment for acoustic observation. This method also applies to other underwater mobile observation platforms. This study provides a reference for the acoustic integration design of underwater equipment such as long-range AUVs or hybrid-driven underwater gliders.

Design and Motion Performance Analysis of Turbulent AUV Measuring Platform.

The use of a multi-functional autonomous underwater vehicle (AUV) as a platform for making turbulence measurements in the ocean is developed. The layout optimization of the turbulence package and platform motion performance are limitation problems in turbulent AUV design. In this study, the computational fluid dynamics (CFD) method has been used to determine the optimized layout position and distance of the shear probe integrated into an AUV. When placed 0.8 D ahead of the AUV nose along the axis, the shear probe is not influenced by flow distortion and can contact the water body first. To analyze the motion of the turbulence AUV, the dynamic model of turbulence AUV for planar flight is obtained. Then, the mathematical equations of speed and angle of attack under steady-state motion have also been obtained. By calculating the hydrodynamic coefficients of the turbulence AUV and given system parameters, the simulation analysis has been conducted. The simulation results demonstrated that the speed of turbulent AUV is 0.5–1 m/s, and the maximum angle of attack is less than 6.5°, which meets the observation requirements of the shear probe. In addition, turbulence AUV conducted a series of sea-trials in the northern South China Sea to illustrate the validity of the design and measurement. Two continuous profiles (1000 m) with a horizontal distance of 10 km were completed, and numerous high-quality spatiotemporal turbulence data were obtained. These profiles demonstrate the superior flight performance of turbulence AUV. Analysis shows that the measured data are of high quality, with the shear spectra being in very good agreement with the Nasmyth spectrum. Dissipation rates are consistent with background shear. When shear velocity is weak, the measurement of dissipation rate is 10−10 W Kg−1. All indications are that the turbulence AUV is suitable for long-term, contiguous ocean microstructure measurements, which will provide data needed to understand the temporal and spatial variability of the turbulent processes in the oceans.

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.

DESIGN OF LOW-DRAG AUTONOMOUS UNDERWATER VEHICLES AND FLOW CONTROL

Design of autonomous underwater vehicles (AUV) met the opposite challenges. Their achievable route can be enhanced with drag reduction due to an increase of AUV slenderness. However, blunt short AUV have others operational advantages. The possibility to design low-drag bodies for Reynolds numbers employed by contemporary AUV (2×106&lt;Re&lt;107) is based on a combination of known facts. First, blunt bodies experience a drag crisis associated with laminar-turbulent transition in their boundary layers and some boundary layer suction additionally reduces their drag. Second, the transition can be delayed till much higher Re for bodies without adverse pressure gradients over their forward and medium parts. Suction on sterns of such bodies allows for the very substantial drag reduction. Several body shapes with distributed suction with extremely low slenderness (L/B&lt;1.5) are presented. Their drag coefficients are between 0.007 and 0.02, whereas for ellipsoid of the same slenderness it exceeds 0.08.