Hybrid Autonomous Underwater Vehicle Research Articles

Станция подводного обслуживания гибридного необитаемого подводного аппарата системы мониторинга подводного добычного комплекса

The use of support vessels significantly increases the cost of monitoring objects of underwater production complexes (UPC), and the presence of a cable communication line significantly limits the possibility of using remote-controlled uninhabited underwater vehicles (ROV), which is reduced to zero in conditions of continuous ice coverage of the work area. An obvious alternative to the use of ROVs are autonomous uninhabited underwater vehicles (AUVs), equipped with equipment for conducting contact work with monitoring objects and communicating with the shore control post. At the same time, the necessary autonomy for the use of such hybrid autonomous uninhabited underwater vehicles (HAUVs) can be ensured by a network of bottom stations equipped with systems for contactless charging and information exchange with the shore UPC control post. The work proposes the concept of an underwater service station (USS) for a HAUV, which allows, in long-term underwater deployment conditions, to use the device not only in an autonomous mode, but also in a remote control mode from a shore control post. A model for using the station for its intended purpose and the composition of the equipment necessary for its implementation have been determined, the design of the technical solution of the station has been presented, determined taking into account the features of installation on a complex bottom surface and the requirements for docking the HAUV for contactless charging and information exchange, including in the mode of remote control from the SCP. Basic technical solutions for the USS have been developed that provide automatic adjustment of the horizontal position of the docking unit, reliable docking and holding of the HAUV charging and information exchange terminals, and control of the vehicle’s pointing process using a set of rotary video cameras with lamps and a sector-view sonar. Algorithms for interaction between the station and the HAUV have been developed for autonomous and controlled via optical communication cable operating modes of the vehicle.

Addressing Actuator Saturation during Fault Compensation in Model-Based Underwater Vehicle Control

Robust control systems are a necessity for autonomous underwater vehicle (AUV) systems due to the challenges they face during operation. Many AUV control-design methods have been developed for different actuator configurations, with robustness against model parameter uncertainties, environmental disturbances, and system faults. Actuator faults can reduce the physical capabilities of a system, which can be compensated for through control re-allocation. However, the increased control allocation to the remaining actuators may cause actuator saturation and reduce controller performance. In this work, we present a depth-pitch model-based nonlinear control law that directly considers actuator saturation, and a fault-tolerant control allocation method for a hybrid AUV actuator configuration. Two types of actuator faults are considered for an underwater vehicle with a hybrid actuator configuration. The proposed controller is implemented in a simulated system, and its trajectory tracking performance is compared with a baseline system without fault or saturation tolerance. To determine the utility of the proposed saturation and fault tolerance control methods, the tracking performance in these simulations is quantified in terms of the settling time, post-fault peak values, and root mean square of the depth and pitch errors.

Simulation Study on a New Hybrid Autonomous Underwater Vehicle with Elevators

This study aims to design a new hybrid twin autonomous underwater vehicle (HTAUV) consisting of dual cylinder hulls and analyze its pitching motion. The kinematic model for the HTAUV is established, followed by the execution of hydrodynamic simulation CFD of the HTAUV using Ansys Fluent. These simulations are conducted to obtain the hydrodynamic force equation of the HTAUV, which relates to the deflection angle of the elevator. Through the motion simulation of the HTAUV, under the same net buoyancy condition, notable differences emerge when the elevator is deflected. Specifically, parameters such as gliding speed, gliding angle, and pitch angle of the HTAUV are larger when the elevator is deflected, as compared to cases where no deflection is applied.

Underwater Drones Promote Sustainability of Offshore Natural Resources Exploitation

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 32481, “How Underwater Drones Can Promote the Environmental Sustainability of Offshore Natural Resources Exploitation,” by Giovanni Massari, Cristina Marras, SPE, and Francesco Cavallini, Saipem. The paper has not been peer reviewed. Copyright 2023 Offshore Technology Conference. Reproduced by permission. _ The goal of the complete paper is to offer an overview of underwater intervention/inspection drones (UIDs) and provide the necessary elements to take full advantage of this technology, supporting environmental sustainability of future offshore projects and activities. The investigation provided in the complete paper explores conventional applications for oil and gas and extends to future energy, mining, and CO2 capture and storage projects. UID Technology Subsea robotics is rapidly evolving from conventional remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) to services delivered by a new generation of vehicles with hybrid capabilities. UIDs present distinct advantages and technical challenges, including the following: - UIDs are battery-powered robotic solutions capable of interchanging data through water communication modems (acoustic or optical). - UIDs have hybrid AUV and ROV capabilities; as an ROV, they can be operated by a pilot using a remotely controlled console that also can be located onshore, while, as an AUV, they can execute complex tasks or missions automatically. - Underwater drones can efficiently and safely operate in total darkness, with poor or no communication links. For this reason, UIDs typically are provided with an advanced set of sensors (sonar, cameras, and lasers) capable of providing information about the vehicle’s orientation, altitude, depth, and the absolute or relative position. - UIDs can be deployed from a topside offshore facility, launched from shore, or deployed inside a subsea garage. Although these descriptions underline some of the technical challenges related to UIDs that require additional steps to achieve full maturity, the use of UIDs nevertheless clearly presents advantages that are almost independent from the application scenarios, including reduced operational risks, intervention time, CO2 emissions, and cost. Environmental Sustainability of Offshore Projects The notion of environmental sustainability embodies maintaining an ecological balance in the natural environment for the benefit of current and future generations; promoting responsible and respectful management of natural resources; avoiding their depletion and the degradation of the environment; and extending the concept to encompass social, human, and economic considerations. Robotic subsea technology offers pivotal assistance in accessing critical information so that all stakeholders can execute and operate offshore projects responsibly, satisfying essential projects’ commercial, environmental, and social criteria. The authors write that, while offshore companies and technology suppliers have already jointly explored the introduction of UIDs within conventional integrity-management campaigns of oil and gas fields, confirming the benefits of this choice for derisking and cost efficiency, a deep analysis on how UIDs can be used to boost environmental sustainability of complex offshore projects is still missing. Their work investigates relevant examples in this domain.

Microstructure Turbulence Measurement in the Northern South China Sea from a Long-Range Hybrid AUV.

This study describes the development of a long-range hybrid autonomous underwater vehicle (AUV) for ocean turbulence measurement. It is a unique instrument, combining the characteristics of the conventional AUV and the buoyancy-driven glider, with a variety of flexible motion modes, such as cruise mode, glider mode, drift mode, and combination of multiple motion modes. The hybrid AUV was used for continuous turbulence measurement in the continental slope of the northern South China Sea in 2020. A total of ten continuous profiles were completed covering a horizontal span of 25 Km and a depth of 200 m. The hybrid AUV was operated in the combined glider and cruise mode. The hybrid AUV's flight performance was stable and satisfied the requirement for turbulence observation. The measured velocity shears from both probes were in good agreement, and the noise-reduced shear spectra were in excellent agreement with the Nasmyth spectrum. The water column in the study area was highly stratified, with a thick thermocline. The dissipation rate (ε) varied from 1.41 × 10-10 to 4.18 × 10-7 W·kg-1. In the surface mixed layer, high values of ε (10-9∼10-8 W·kg-1) were observed toward the water surface. In the thermocline, ε was 10-9.5∼10-9 W·kg-1, which was smaller than the level of the surface mixed layer. This result was mainly because of the strong "barrier"-like thermocline, which damped the transmission of wind and heat energy from the surface mixed layer to the deep layer. Overall, this study demonstrates the utility of hybrid AUVs for collecting oceanic turbulence measurements. They are a powerful addition to traditional turbulence instruments, as they make it possible to survey large areas to obtain high-quality and high-resolution data in both vertical and horizontal directions over long durations.

Analysis of a New Twin Hybrid Autonomous Underwater Vehicle

The twin hybrid autonomous underwater vehicle (THAUV) is a novel type of unmanned underwater platform that consists of a twin torpedo-shaped hull and is actuated by two buoyancy engines and two thrusters proposed in this paper. The THAUV was designed to have faster speed generated by the two buoyancy engines and two thrusters. The two buoyancy engines on each hull and the airfoil are mainly responsible for the diving and surfacing motion, and the thrusters drive the THAUV along the horizontal plane. The THAUV is capable of carrying more instrumentation and energy than a conventional hybrid autonomous underwater vehicle (HAUV) with a single buoyancy engine such that the THAUV can perform more exploration tasks and operate for a longer period in a one-time operation. Different from other unmanned underwater vehicles (UUVs) with two airfoils or wings, the THAUV has a single airfoil connecting the twin hull such that it does not require connecting bars and additional airfoils. For this reason, the structure of THAUV is more compact and simpler. In this paper, a new compact THAUV is designed and CFD simulation is used to obtain the hydrodynamic parameters of THAUV operation in water. The motion model of the THAUV is also established and the operating parameters of the THAUV are obtained by simulation.

Time-Optimal Path Planning of a Hybrid Autonomous Underwater Vehicle Based on Ocean Current Neural Point Grid

Path planning is the precondition for Hybrid Autonomous Underwater Vehicles (HAUV) to enter the submerged area to undertake a mission. The influence of ocean currents on HAUV should be further investigated to obtain a time-optimal path. The improved A* algorithm and the neural network model are employed in this paper to plan a time-optimal path for the vehicle. The HAUV in glider mode is capable of traveling forward mainly through the zigzag motion in vertical plane. Since the vehicle can only receive the command orders when it surfaces from the water, the path is expected to include a series of discrete waypoints in the water surface. At the same time, the presence of submerged riverbeds is also taken into account to avoid hazards for HAUVs when it navigates in the water. It can be demonstrated that ocean currents can be used to decrease the operating time. The comparison results of the two methods verify that the size of the map affects the calculation time. In addition, the neural node represented method surpasses the modified A* method, especially when the map is too large.

Passive Bearing Estimation Using a 2-D Acoustic Vector Sensor Mounted on a Hybrid Autonomous Underwater Vehicle

The bearing estimation problem of low-frequency underwater acoustic sources is of paramount importance in antisubmarine warfare and passive acoustic monitoring applications. Typical solutions require manned vessels and towed arrays characterized by high costs, risks, and deployment difficulties. An alternative solution for such applications is represented by acoustic vector sensors (AVSs), which are lightweight, compact, and moderate in cost, have promising performance in terms of bearing discrimination and the potential to operate from autonomous underwater platforms. This article presents an experimental assessment of a 2-D AVS derived from a sonobuoy and mounted on a hybrid autonomous underwater vehicle (AUV) for estimating the bearing of underwater sources. The sensor model, its technical characteristics, the installation onboard the vehicle, and the implementation of the passive signal processing chain are reported. Three different algorithms for bearing estimation have been tested on real data: one based on a time-domain representation, one based on the frequency domain, and one relying on joint time–frequency representation. Experimentation and data are presented, first from very shallow waters within the Italian Navy base of CSSN, La Spezia, and then from the Tyrrhenian Sea, in the context of a multiplatform exercise led by the NATO S&TO CMRE. Using an acoustic navigation system as ground truth, these experiments allow the assessment of bearing estimation capabilities in both AUV (by using propeller and pump jets) and gliding navigation modes. While the results of all the three processing methods are at least par to those recently reported in similar experiments with different vector sensors and processing, the time–frequency-domain method can identify multiple sources without prior knowledge of the source signal waveform or bandwidth.

Evaluation of energy management strategies for fuel cell/battery-powered underwater vehicles against field trial data

• Evaluation of Energy Management Strategies (EMS) against field trial data. • Fuel cell/battery-hybrid power system is modelled in Simulink®. • Performance criteria include energy efficiency, degradation and power reliability. • Choice of EMS depends on character of mission: high-autonomy missions require more complex EMS. This study combines high-fidelity simulation models with experimental power consumption data to evaluate the performance of Energy Management Strategies (EMS) for fuel cell/battery hybrid Autonomous Underwater Vehicles (AUV). The performance criteria are energy efficiency, power reliability and system degradation. The lack of standardized drive cycles is met by the cost-efficient solution of synthesizing power profiles from sampled AUV field trial data. Three power profiles are used to evaluate finite-state machine, fuzzy logic and two optimization-based EMS. The results reveal that there is a trade-off between the objectives. The rigidity of the EMS determines its load-following behavior and consequently the performance regarding the objectives. Rule-based methods are particularly suitable to design energy-efficient operations, whereas optimization-based methods can easily be tuned to provide power reliability through load-following behavior. Both classes of EMS can be best-choice methods for different types of missions.

Robust depth control of a hybrid autonomous underwater vehicle with propeller torque's effect and model uncertainty

This paper presents a study of depth tracking controller design for a hybrid AUV in the presence of model uncertainty and propeller torque's effect. Firstly, the six degrees of freedom (6-DOF) nonlinear equations of motion, as well as the operating mechanisms and specific characteristics of the hybrid AUV, are described. Subsequently, the model for depth-plane is extracted by decoupling and linearizing the 6-DOF AUV model. Furthermore, a nonlinear disturbance observer (NDO) is constructed to deal with the linearization errors and uncertain components in the depth-plane model. A depth tracking controller is then designed based on the backstepping technique to guarantee the tracking error converges to an arbitrarily small neighborhood of zero. Besides, the robust stability of the proposed controller concerning the propeller torque's effect and the model uncertainty is analyzed. To ensure the objectivity and feasibility of the proposed method, the depth controller is applied to the 6-DOF model of AUV so that it maintains the coupling between roll, yaw, and pitch motion. Finally, the numerical simulation is carried out via MATLAB/SIMULINK to verify the controller's effectiveness, feasibility, and stability.

Mystery pufferfish create elaborate circular nests at mesophotic depths in Australia.

In 2011, the enigma of "mystery circles," small but complex underwater structures first observed by divers from southern Japan in 1995, was solved when a new species of pufferfish, white-spotted pufferfish (Torquigener albomaculosus Matsuura 2014), was identified as the responsible agent. To date these circles have been described only from Japan, where they are formed on a sandy seafloor in water depths less than 30 m. A survey of oil field infrastructure on the North West Shelf of Western Australia in 2018 using a remotely operated vehicle and hybrid autonomous underwater vehicle (HAUV) recorded a high-resolution video and bathymetric data of 21 circular formations with similar features to those described in Japan. The circles display dimensions and morphology like those described from Japan, but were observed in water depths between 129 and 137 m. The HAUV also recorded high-resolution photographs which captured a Torquigener sp. fish in the immediate vicinity of the circles. An additional circle and Torquigener sp. were observed in images collected by baited remote underwater stereo-video in a nearby location in 129 m depth. These circles are the first to be found in Australia. The pufferfish species responsible cannot be identified from images collected. Such a discovery not only generates intrigue and wonder among scientists and the general public but also provides an insight into the reproductive behaviour and evolution of pufferfish globally.

ENDURUNS: An Integrated and Flexible Approach for Seabed Survey Through Autonomous Mobile Vehicles

The oceans cover more than two-thirds of the planet, representing the vastest part of natural resources. Nevertheless, only a fraction of the ocean depths has been explored. Within this context, this article presents the H2020 ENDURUNS project that describes a novel scientific and technological approach for prolonged underwater autonomous operations of seabed survey activities, either in the deep ocean or in coastal areas. The proposed approach combines a hybrid Autonomous Underwater Vehicle capable of moving using either thrusters or as a sea glider, combined with an Unmanned Surface Vehicle equipped with satellite communication facilities for interaction with a land station. Both vehicles are equipped with energy packs that combine hydrogen fuel cells and Li-ion batteries to provide extended duration of the survey operations. The Unmanned Surface Vehicle employs photovoltaic panels to increase the autonomy of the vehicle. Since these missions generate a large amount of data, both vehicles are equipped with onboard Central Processing units capable of executing data analysis and compression algorithms for the semantic classification and transmission of the acquired data.

Three-dimensional trajectory tracking of a hybrid autonomous underwater vehicle in the presence of underwater current

In this work, a six degrees-of-freedom (DOF) nonlinear kinematic and dynamic model of a Hybrid Autonomous Underwater Vehicle (H-AUV) is derived for the two modes of locomotion, propelled and gliding modes. A comprehensive linearization algorithm is developed to include both modes of locomotion. Starting with a three-dimensional time-parameterized curve of position history, Frenet-Serret frames are used to specify the unknown nominal states, which in turn are used to obtain the nominal inputs. A linear time-variant (LTV) state-space model is obtained, and a linear quadratic regulator (LQR) is designed and applied to the nonlinear model. The performance of the devised controller is assessed via a metric that computes the error between the actual and the desired position. Simulation results show that the LQR provides accurate tracking performance, even in the presence of underwater currents with bounded flow velocity. Moreover, the controller autonomously switches modes between propulsion and gliding to ensure minimal trajectory tracking error and energy consumption.

A controller comprising tail wing control of a hybrid autonomous underwater vehicle for use as an underwater glider

A controller for an underwater glider is presented. Considered underwater glider is a torpedo-shaped autonomous underwater vehicle installing adjustable buoyancy bag and movable battery in it. The controller is composed of an LQR controller to maintain zigzag vertical movement for gliding and two PD controllers to control elevator/rudder angles. The LQR controller controls the pumping speed into the buoyancy bag and the moving speed to locate the battery. One of the PD controller controls the elevator angle to assist the LQR controller, and the other controls the rudder angle to adjust the direction of the underwater glider. A reduced order Luenberger observer is adopted to estimates the center of gravity of the glider and the buoyancy mass that are essential but cannot be measured. Mathematical simulation using Matlab proved the validity of the proposed controller to obtain better performance than conventional LQR only controller under the influence of sea current.

Cross-coupling effect and motion control of an autonomous underwater vehicle with internal actuators

Hybrid autonomous underwater vehicles (AUVs) use internal actuators, e.g., tunnel thruster, moving mass, and ballast chamber, for yaw and pitch steering. Unlike control surfaces, internal actuators perform independently of relative flows around AUVs, thus suitable for missions which require excellent low-speed maneuverability. This research focuses on an investigation into the control design of an REMUS AUV using internal actuators to steer its heading direction. It has been shown that an internal moving mass together with a tunnel thruster is capable of providing actuations to serve the purpose. However, our analysis indicates that a coupling between roll and pitch motion causes the internal actuators to oscillate if depth-plane motion is neglected when deriving control laws for the internal actuators. We present a novel control strategy by taking advantage of the cross-coupling effect when designing the heading autopilot system with internal actuators. The effectiveness and robustness of the proposed design are validated by simulation results.

Heading Autopilot of Autonomous Underwater Vehicles With Internal Moving Mass

Inspired by the designs of underwater gliders, hybrid autonomous underwater vehicles (AUVs) have emerged recently, which use internal actuators instead of control surfaces to control the heading angle and depth of the vehicles. In this paper, we focus on controlling the heading angle of a REMUS AUV by using an internal moving mass. We derive a nonlinear dynamical model of the vehicle with hydrodynamic forces and coupling between the vehicle and the internal moving mass. The model is used to study the stability of the horizontal-plane motion of the vehicle and to design a linear feedback law to stabilize its heading angle around a desired direction. Simulation results demonstrate that a controlled internal moving mass is able to fulfill the purpose of heading control.

Nonlinear heading control of an autonomous underwater vehicle with internal actuators

Designs of hybrid autonomous underwater vehicles (AUVs), which use internal actuators instead of control surfaces to steer, have emerged recently in the ocean engineering community. This paper focuses on the heading autopilot design for a REMUS AUV by using an internal moving mass. A nonlinear dynamical system is first derived which describes the horizontal-plane motion of the vehicle coupled with an internal moving mass. It is shown that a displacement of the internal mass in the sway direction can affect the flow of the dynamical system in phase space. Using displacement as the system input, a LQR controller is designed to stabilize the heading angle of the vehicle by taking advantage of the position and inertia of the internal moving mass. The linear controller cannot deal with large perturbations due to the constraints on the maximum displacement and movement speed of the internal moving mass. Consequently, a tunnel thruster is added to the design in order to address the problem. A nonlinear full-state feedback law is derived based on backstepping and Lyapunov redesign technique to control the displacement of the internal mass and the force exerted by the tunnel thruster. Simulation results demonstrate the effectiveness of the proposed design.

Model predictive control of a hybrid autonomous underwater vehicle with experimental verification

In this work, model predictive control is used to provide transit and hover capabilities for an autonomous underwater vehicle where the description of the system dynamics used include terms measured experimentally. The resulting controller manoeuvres the vehicle in the presence of constraints on the actuators and results obtained from the deployment of the vehicle in an inland lake for the study of the zebra mussel, an invasive species, are also given.

P-SURO II 하이브리드 자율무인잠수정 기술 개발 및 현장 검증

In this paper, we present the development of P-SURO II hybrid AUV (Autonomous Underwater Vehicle) which can be operated in both of AUV and ROV (Remotely Operated Vehicle) modes. In its AUV mode, the vehicle is supposed to carry out some of underwater missions which are difficult to be achieved in ROV mode due to the tether cable. To accomplish its missions such as inspection and maintenance of complex underwater structures in AUV mode, the vehicle is required to have high level of autonomy including environmental recognition, obstacle avoidance, autonomous navigation, and so on. In addition to its systematic development issues, some of algorithmic issues are also discussed in this paper. Various experimental studies are also presented to demonstrate these developed autonomy algorithms.

Small boat localization using adaptive three-dimensional beamforming on a tetrahedral and vertical line array

Passive acoustic detection and localization of small surface craft has a number of practical applications, such as monitoring and protecting sensitive marine habitats. Moored passive equipment can be cumbersome to deploy and communicate with, so AUV-mounted devices are being investigated as an alternative. The GLASS’12 experiment was designed to assess the feasibility of using a hybrid autonomous underwater vehicle outfitted with a compact volumetric nose array as a data collection platform. The array consisted of five vertical elements and 4 in a tetrahedral arrangement, and the hybrid underwater vehicle had the capability operating in either glider or propeller-driven modes. The rigid design of the array minimized element location mismatch and enabled the use of aggressive adaptive beamforming in 3-D. This facilitated isolation of broadband multipath arrivals originating from the motor of a small rubber boat. Cross-correlation of beams enabled the time-lag between the arrivals to be measured, which, in turn yielded information about the target range. The underlying formulation bears similarity to the passive fathometer [J. Acoust. Soc. Am. 120(3) (2006)], which exploits surface wave noise rather than ship noise. This presentation will focus on the array beamforming and potential applications for localization and environmental sensing.