Autonomous Undersea Vehicles Research Articles

Efficient path planning for AUVs in unmapped marine environments using a hybrid local–global strategy

The ability of autonomous undersea vehicles (AUVs) to plan paths in unknown marine environments is the precondition for executing complicated missions. However, existing path planning algorithms based on underwater sensing equipment often struggle to achieve efficient exploration and generate high-quality trajectories. In this paper, we introduce a novel approach to efficiently handle the challenge of AUV navigation under limited information. Our solution combines global and local planning techniques to generate optimized paths that guarantee collision-free and efficient operations. In global path planning, we incrementally use the rolling windows to make decisions on high-level path branching while utilizing waypoints from selected branches to refine the calculation of local paths for enhanced accuracy. We employ an efficient small-scale path search strategy at the local path computation level by leveraging sensor-detected environments. In this stage, we propose an advanced rapidly exploring random tree (RRT) algorithm called circle-RRT. By combining adaptive circle sampling with dynamic step sizes, this algorithm can significantly reduce the generation of redundant sampling points and improve the efficiency of local path planning. We evaluated the efficiency of our algorithm in unknown environments through simulations and compared it with previous leading methods.

SMART submarine cable technology can facilitate acoustics on the global scale

The submarine cable industry is beginning to share their infrastructure for ocean observing. Science Monitoring And Reliable Telecommunications (SMART) Subsea Cables is working to integrate temperature, pressure, and seismic acceleration sensors into commercial cables (∼70 km spacing) to support climate monitoring and disaster risk reduction on the global scale. The seismic and pressure sensors are expected to have sensitivity at low acoustic frequencies, (e.g., <50 Hz and <5 Hz, respectively); future systems could include hydrophones and other sensors. Further, telecom rated branching cables supporting multipurpose “nodes” are becoming a reality (per existing dedicated science cable systems). These can support low frequency transceivers and autonomous undersea vehicles (AUVs). With cabled power, these would be part of the fixed/mobile acoustic tomography system measuring ocean heat content and more generally for transporting energy, data, and acquiring multidisciplinary data throughout a large volume of the ocean. A 3700 km SMART ring system in Portugal will be ready in 2026 and one connecting Vanuatu and New Caledonia is starting. Others in planning stages that could include these concepts are: Far North Fiber connecting Norway/Finland/Ireland with Japan, the NSF proposed SMART cable connecting New Zealand with Antarctica, New Zealand-Chatham Islands, and Lisbon-Egypt through the Mediterranean.

Adaptive Backstepping Axial Position Tracking Control of Autonomous Undersea Vehicles with Deferred Output Constraint

In this paper, an adaptive backstepping control scheme is proposed to solve the the surge motion tracking control problem of an autonomous undersea vehicle (AUV) with system constraint. First, an initial rectification reference signal is constructed for the subsequent implementation of deferred output constraint and making the control input smaller and smoother in the early stage of system operation. Second, a barrier Lyapunov function is adopted for developing an output-constrained state feedback adaptive controller. Then, on the basis of coordinate transformation and estimating the derivative of surge displacement by a linear and nonlinear combined differentiator, we develop an output feedback adaptive backstepping control scheme for AUVs whose velocity signals are unmeasurable. We also carried out a comparative numerical simulation with traditional adaptive control to verify the feasibility of the proposed control strategy.

New developments in submarine cable technology can facilitate acoustics in Polar regions and on the global scale

The subsea telecommunications cable industry is expanding their present single purpose infrastructure to include ocean observing capability. Science Monitoring And Reliable Telecommunications (SMART) Subsea Cables is working to integrate temperature, pressure, and seismic acceleration sensors into commercial cables (∼70 km spacing) to support climate and ocean observation, sea level monitoring, and tsunami and earthquake early warning on the global scale. Furthermore, telecom rated branching cables with power feed units supporting multipurpose “nodes” are becoming a reality. Acoustic capability can be integral to both. Major uses of these nodes include supporting low frequency transceivers enabling basin scale tomography and geo-positioning of mobile assets and docking for autonomous undersea vehicles (AUVs). Enabled by cabled power, these would be part of the fixed/mobile acoustic tomography system measuring ocean heat content at the speed of sound and more generally for transporting energy, data, and acquiring multidisciplinary data throughout a large volume of the ocean. Both variants and hybrids between can support the necessary acoustics contribution to ocean observing. Two proposed systems can support polar applications: Far North Fiber Express connecting Norway/Finland/Ireland with Japan via the Canadian Northwest Passage, and the NSF proposed SMART cable connecting New Zealand with McMurdo Base, Antarctica.

Hydrothermal Chimney Distribution on the Endeavour Segment, Juan de Fuca Ridge

AbstractThe Endeavour Segment of the Juan de Fuca Ridge is well known for its abundance of hydrothermal vents and chimneys. One‐meter scale multibeam mapping data collected by an autonomous undersea vehicle revealed 572 chimneys along the central 14 km of the segment, although only 47 are named and known to be active. Hydrothermal deposits are restricted to the axial graben and the near‐rims of the graben above a seismically mapped axial magma lens. The sparse eruptive activity on the segment during the last 4,300 years has not buried inactive chimneys, as occurs at more magmatically robust mid‐ocean ridges.

Robotic Solutions for Arctic Transit Corridor Cargo Autonomous Undersea Vehicles

The development of regular navigation through the Arctic Ocean transit transport corridor from Southeast Asia to Western Europe can provide economic advantages comparable in importance with the construction and operation of the main canals between the oceans – the Suez and Panama. Cost-effective year-round navigation on the northern transport corridor is possible with an undersea (under-ice) scheme of cargo delivery. The construction of reinforced concrete Cargo Autonomous Undersea Vehicles (CAUVs) and the lighter transportation scheme allow solving technical and economic problems. The complicated scheme of undersea transportation gives birth to a new class of ships and raises a number of unsolved technical tasks. Among them are the loading of lighters on CAUVs, the formation of CAUVs trains and the locomotion control tasks. All these tasks require control of a large number of parameters and are complex for humans. Robotic CAUVs are regarded as an option of choice to deal with these control tasks.

Mobile Robot Rendezvous Using Potential Fields combined With Parallel Navigation

Industrial robotics, military, surveying, and delivery applications have laid a foundation for research into autonomous machines, including unmanned aerial vehicles, autonomous ground vehicles, and autonomous undersea vehicles. This paper supports this research by developing a new guidance method which combines potential fields, typically used for obstacle avoidance, and parallel navigation, a popular missile guidance method. The new unified algorithm allows a mobile robot interceptor to guide to, and rendezvous with, a moving target while avoiding obstacles in its path. A Matlab simulator is used to analyze performance for different interceptor-target geometries and obstacle densities. Simulations and analysis show that the combined algorithm increases performance by reducing the time-to-contact in most of the cases. Specifically, it was found to provide a 14.4%–21.3% improvement in approximately 96%–98% of the simulation cases.

A bio-inspired climb and glide energy utilization strategy for undersea vehicle transit

Marine animals have been the bio-inspirational source for some novel concepts for locomotion, sensing, and the intelligent control of undersea vehicles. There has been little (if any) research in the area of bio-inspired energy utilization strategies applied to undersea vehicles. For example, there are reasons why some fish swim at a specific cruise speed; why some fish move by burst acceleration to higher speeds followed by coasting; and why some negatively buoyant fish alternately glide downwards, and then swim upward. The goal of this study is to develop the theory and models of the climb and glide form of autonomous undersea vehicle transit in a form that can permit assessment of future practical technology insertions (such as drag reduction and wing design). In addition, existing theory was expanded to address vehicles with significant wet weight and the effect of hotel load (equivalent to the basal metabolic rate of animals). Several observations from this preliminary analysis for climb/glide operation of practical vehicles were made. Over a practical and useful range of hotel loads and net vehicle lift-to-drag ratios, energy savings benefits relative to level flight transit from 10% to excess of 40% can be expected. This translates directly into a 10–40% increase in range if a climb/glide strategy is employed instead of level flight transit under the right operating conditions.

IRAP: An integrated, real-time, autonomous passive acoustic monitoring system for beaked whale detection, localization, and tracking

The integration and demonstration of passive sonar hydrophone arrays into autonomous undersea platforms for acoustic marine mammal monitoring has witnessed significant advances in the last few years due to the availability and scalability of low-cost, low-power commercial technology for acoustic remote sensing. In this paper, we will review the at-sea performance of a nine-element Mills Cross high frequency hydrophone array (HFA) integrated into an autonomous undersea vehicle (AUV) for the detection, classification, localization, and tracking (DCLT) of beaked whales during a deployment conducted off leeward Kauai in February, 2016. Using passive sonar equation analysis, we will review the design rationale of the HFA, and quantify system performance using standard signal processing metrics such as measured array gain, tracking accuracy, and detection range on a calibrated high-frequency source transmitting replica beaked whale click trains at a de minimus source level. A candidate autonomous real-time passive sonar processing architecture that combines an adaptive beamformer/matched filter front-end with a false alarm mitigation back-end to balance detection sensitivity, classifier robustness, and processing throughput will also be presented. We conclude with a cost/power/persistence trade-off for some commercially available autonomous platforms. [This work was supported by NAVFAC Living Marine Resources Program.]

Research on Dynamic Simulation of AUV Launching a Towed Navigation Buoyage

A mathematic model was established to simulate the process of AUV (autonomous undersea vehicle) launching a towed buoyage. Based on the lumped mass method and moment theorem and angular momentum theorem, dynamic equations of the cable and the buoyage were developed, respectively. Then the boundary conditions and the numerical scheme to deal with the cable with non-fixed length were presented. Moreover, the process of AUV launching a towed cable was simulated. By using the model, the results show the trajectory of buoyage and shape of towed cable can be well predicted.

Range dependent sediment sound speed profile measurements using the image source method

This paper presents a range dependent sediment sound speed profile measurement obtained using the image source method. This technique is based on the analysis of the seafloor reflected acoustic wave as a collection of image sources which positions are linked with the thick-nesses and the sound speed of the sediment stack. The data used were acquired by the NURC in 2009 during the Clutter09 experiment. The equipment used was an autonomous undersea vehicle towing a 1600-3500 Hz frequency band source and a 32 m horizontal line array of 32 hydrophones at 12 m above the seabed. Under the assumption of locally range independent seabed properties, the moving horizontal array provides successive range independent sediment sound speed profiles along a track to obtain the range and depth dependent structure of the seafloor. Two key steps include recovery of the time-varying unknown array shape from the data and spatial filtering of the successive sound speed profiles. A comparison of the image source method result and seismic data along nearly the same 14 km track indicates that the seabed stratigraphy is correctly mapped by this method.

Bioinspired Propulsion Mechanisms Based on Manta Ray Locomotion

AbstractMobuliform swimmers are inspiring novel approaches to the design of underwater vehicles. These swimmers, exemplified by manta rays, present a model for new classes of efficient, highly maneuverable, autonomous undersea vehicles. To improve our understanding of the unsteady propulsion mechanisms used by these swimmers, we report detailed studies of the performance of robotic swimmers that mimic aspects of the animal propulsive mechanisms. We highlight the importance of the undulatory aspect of producing efficient manta ray propulsion and show that there is a strong interaction between the propulsive performance and the flexibility of the actuating surfaces.

Applied Model-Based Analysis and Synthesis for the Dynamics, Guidance, and Control of an Autonomous Undersea Vehicle

Model-based analysis and synthesis applied to the dynamics, guidance, and control of an autonomous undersea vehicle are presented. As the dynamic model for describing vehicle motion mathematically, the equations of motion are derived. The stability derivatives in the equations of motion are determined by a simulation-based technique using computational fluid dynamics analysis. The dynamic model is applied to the design of the low-level control systems, offering model-based synthetic approach in dynamics and control applications. As an intelligent navigational strategy for undersea vehicles, we present the optimal guidance in environmental disturbances. The optimal guidance aims at the minimum-time transit of a vehicle in an environmental flow disturbance. In this paper, a newly developed algorithm for obtaining the numerical solution of the optimal guidance law is presented. The algorithm is a globally working procedure deriving the optimal guidance in any deterministic environmental disturbance. As a fail-safe tactic in achieving the optimal navigation in environments of moderate uncertainty, we propose the quasi-optimal guidance. Performances of the optimal and the quasi-optimal guidances are demonstrated by the simulated navigations in a few environmental disturbances.

Reverberation and scattering measurements from seabed clutter features using an autonomous undersea vehicle.

Acoustic reverberation in littoral ocean waveguides is often controlled by small-scale seabed heterogeneities. Thus, validation of reverberation models and development of realistic simulations require measurements of those scales. Clutter features for mid-frequency active sonars span scales from order 1–1000 m. The smaller scale seabed features O(1–10)m, however, are not generally represented in bathymetric data, even from modern hull-mounted multibeam systems. One promising tool for isolation and quantitative measurement of small-scale seabed features is an AUV with a source (800–3500 Hz) and towed array. Recent measurements from the Clutter09 experiment in the Straits of Sicily show that O(1–10)m scale seabed features (e.g., carbonate chimneys on mud volcanoes) are resolved and can be quantified. [Work supported by the Office of Naval Research OA321 and the NATO Undersea Research Centre.]

Seabed reflection measurements from an autonomous undersea vehicle: Probing seabed spatial variability.

Spatial variability of the seabed in littoral regions is driven by processes that span a large range of space and time scales, ranging from eustatic fluctuations which are more or less global in extent but can have a profound effect on sedimentary layering from hundreds of meters to sub‐meter scales, to biologic reworking which might be very local and affect only the upper few tens of centimeters. These processes (as well as many others) conspire to create a rich variety of sediment property distributions both in vertical and horizontal dimensions. One way to probe the spatial variability is with wide‐angle reflection measurements. Here we discuss results from the Clutter09 experiment in which seabed reflection measurements were conducted using a broadband source (800–3500 Hz) and a 32 element towed horizontal receiver. The results are compared with previous observations using a single hydrophone and a Uniboomer. [Work supported by the Office of Naval Research OA321 and the NATO Undersea Research Centre.]

Synchronization of Animal-Inspired Multiple High-Lift Fins in an Underwater Vehicle Using Olivo–Cerebellar Dynamics

The development of neuroscience-based control methodologies and their integration with the high-lift unsteady hydrodynamics of control surfaces inspired by swimming and flying animals are the subjects of this paper. A biology-inspired rigid autonomous undersea vehicle called the biorobotic autonomous undersea vehicle (BAUV) has been developed at the Naval Undersea Warfare Center (NUWC), Newport, RI. The BAUV is equipped with six simultaneously rolling and pitching fins for generating large unsteady control forces for performing agile maneuvers. First, as an exploratory example, we introduce the van der Pol oscillator as an oscillatory controller for the BAUV and we describe experiments performed to examine the fin forces (thrust and lift) and electric power requirement, and to demonstrate the effectiveness of the oscillator's limit cycle property for disturbance rejection effectiveness. We then describe a BAUV control system that includes six inferior-olive (IO) neuron models for control of the pitch and roll motion of the six foils. These IO neurons exhibit limit cycle oscillation (LCO). For control of the BAUV, these IO neurons must oscillate in synchronism with specific relative phases. We present here four feedback linearizing control systems of varying complexity for control of the relative phases of the IO neurons. It is shown that each of the IO control systems accomplishes asymptotic regulation of the phases and thus enables the foils to produce the required control forces. The first controller has a global synchronization property, but the remaining controllers accomplish local synchronization. We present simulation results for tracking piecewise, time-varying phase angle commands as well as experimental results for control of the BAUV by IO neurons. The results show that with appropriate phasing of the fins, an optimal graceful gait of the BAUV is achieved where no untoward force or moment is present. An analog hardware version of the local controller with a cluster of six IO neurons has also been built, which allows five of the signals to rapidly synchronize to the reference, with or without prescribed phase shift, much like in the simulations. The designed controllers can be used in any platform or multivariate BAUV-like system requiring fast, accurate phase control. Laboratory test results for the phase synchronization of two servomotors (roll and pitch) using the designed analog hardware controller are also shown.

Identifying the parameters of a dynamic autonomous undersea vehicle — environment system

A method for identifying some parameters of a dynamic undersea vehicle — environment system, such as a moment of inertia of rotating drive components with regard to the adjoint moments of inertia and a viscous friction factor of a propeller, is proposed. Simulation validated the high rate of convergence of the desired parameters to the true values.

Passive synthetic aperture as an experimental tool

The use of autonomous undersea vehicle towed arrays offer an inexpensive way to carry out oceanographic measurements. Due to the small size and limited power of such vehicles, the physical aperture of the array is necessarily limited and the tow speed is low. However, there is an advantage in that short arrays at low speeds can have no flow noise. In addition the use of passive synthetic aperture (PSA) to provide spatial resolution and gain can play a major role. Here, we describe the use of two forms of passive synthetic array processing used in a shallow‐water experiment. A six‐element towed array, with 0.75 m spacing, was used to estimate the horizontal wave numbers of a propagation channel. A narrow‐band form of PSA will be described which was used to generate coherent spatial gain by generating an aperture hundreds of wavelengths and provided accurate estimates of the horizontal modal wave numbers at frequencies les than 600 Hz. A broadband form of PSA was used to provide bearing estimation of a ferry passing through the area. The ferry's broadband propulsion noise, which was in the 900 Hz region, was used as the source. An overall increase in gain is demonstrated.

Nonlinear optimization of autonomous undersea vehicle sampling strategies for oceanographic data‐assimilation

AbstractThe problem of how to optimally deploy a suite of sensors to estimate the oceanographic environment is addressed. An optimal way to estimate (nowcast) and predict (forecast) the ocean environment is to assimilate measurements from dynamic and uncertain regions into a dynamical ocean model. In order to determine the sensor deployment strategy that optimally samples the regions of uncertainty, a Genetic Algorithm (GA) approach is presented. The scalar cost function is defined as a weighted combination of a sensor suite's sampling of the ocean variability, ocean dynamics, transmission loss sensitivity, modeled temperature uncertainty (and others). The benefit of the GA approach is that the user can determine “optimal” via a weighting of constituent cost functions, which can include ocean dynamics, acoustics, cost, time, etc. A numerical example with three gliders, two powered AUVs, and three moorings is presented to illustrate the optimization approach in the complex shelfbreak region south of New England. © 2007 Wiley Periodicals, Inc.

Autonomous undersea vehicles and acoustical oceanography

Autonomous undersea vehicles (AUVs) have been actively increasing in their capabilities over the past 10 years. Recent developments in the academic sector have transitioned to become commercially available technologies which are now available for general use in academic, commercial and military applications. The Oceanographic Systems Laboratory at Woods Hole Oceanographic Institution has been a leader in the development of robotic vehicles, with most development funding coming from the Office of Naval Research. The result of this development effort has been the REMUS family of AUV systems. Originally designed primarily for shallow water hydrographic reconnaissance and mine‐hunting, these systems have since been adapted and utilized for many other applications including deep ocean search and survey, physical oceanography, and more recently acoustical oceanography. New, larger systems contain sufficient energy and payload capabilities to tow long hydrophone arrays, and can carry large projectors allowing active and passive techniques to be used in unmanned, un‐tethered systems at any depth in the oceans. Recent developments in these unmanned vehicle systems will be discussed along with new payload capabilities now under development for acoustical oceanography.