Remotely Operated Vehicle System Research Articles

Computational fluid dynamic study on design and modification of underwater remotely operated vehicle

Remotely Operated Vehicle (ROV) has been widely used in numerous underwater exploration applications such as exploration of complex deep sea environment, pipeline detection, installation, maintenance, and repair. Thus, it is worthy to design, optimize, and performance evaluation of ROV systems for underwater exploration purposes. Computational Fluid Dynamic (CFD) is a computational approach that is very helpful and widely used to examine the flow characteristics of ROV systems. In this research work, CFD analyses of ROV bodies with different thruster blades were carried out in order to generate thrust forces by the thruster blades. For this purpose, ANSYS FLUENT was used to examine the flow characteristics over the ROV body. The analyses were performed at different flow velocities, such as 1 m/s, 1.5 m/s, 2 m/s, 2.5 m/s, 3 m/s and 3.5 m/s. The outcomes were in the form of thrust force, drag force, pressure distribution, and velocity distribution. The result shows that four-blade thruster generates maximum thrust force as compare to other ROV thruster models. The main reason behind this higher thrust force is due to the larger motion of the fluid. Similarly, drag force was also investigated and observed that the drag force is greater for thruster model 3, having four blades due to the large frontal area of the ROV body and thruster blades. The results obtained in this study are very helpful for engineers and researchers to design and optimize ROV models using numerical methods.

Total Design in the Design and Development Process of a Remotely Operated Vehicle (ROV) with Particular Consideration of Sensorization

This paper provides a methodological proposal for the design and development process of a remotely operated vehicle (ROV). The design core and product design specifications (PDS) of Pugh’s Total Design model are considered, with a focus on the early stages of the product design and development process. A modularization of the functional groups of an ROV is proposed, focusing attention on the sensor system. The main concepts regarding ROVs are presented, Pugh’s Total Design model is explained, justifying the application interest in technological projects, a methodological proposal adapted to ROV projects is provided, based on Pugh’s Total Design model, with special interest in the early stages of the new product development process (NPD), the suitability of applying our own model of industrial design engineering in an ROV system is analyzed, and the contribution of this study is evaluated, proposing future work and lines of research.

IMPROVING THE PERFORMANCE OF THE UNIVERSAL PREVENTOR

This article will describe and analyze the two last parts of an accident at an offshore drilling facility – total loss of control and post accidental work, specifically emergency operation of a BOP. BOP operation methods that will be discussed here are applicable both for the accidents and generally for the events where the BOP functions should be activated when the system cannot be controlled from the host facility. Tasks to be performed in the current work: Acquire background technical expertise in BOP systems and their controls. Acquire background technical expertise in ROV (Remotely Operated Vehicle) systems and their controls. Acquire background information on Macondo well accident and similar accidents, where the emergency BOP control was required. Discuss the response and work done to get the control over the BOPs in these accidents. Develop possible methods to control the BOP in emergencies. Discuss and compare different methods systematically. Come up with further recommendations. Most information for this work was found on the web, using the search and databases such as Google Scholar and One Petro. Standards were provided by the university library, however NORSOK standards were free available from the internet. A large input came from the interviews with professionals within oil and gas. Keywords: bop, control system, valve.

Operational failure assessment of Remotely Operated Vehicle (ROV) in harsh offshore environments

For an effective integrity assessment of marine robotic in offshore environments, the elements’ failure characteristics need to be understood. A structured probabilistic methodology is proposed for the operational failure assessment (OFA) characteristics of ROV. The first step is to assess the likely failure mode of the ROV system and its support systems. This captures the interaction and failure induced events during operation. The identified potential failure modes are further developed into logical connectivity based on the cause-effect relationship. The logical framework is modeled using the fault tree analysis technique to predict the ROV operational failure probability in an uncertain harsh environment. The fault tree analysis captured the logical relationship between the primary, intermediate, and top events probability. The importance measure criteria were adopted to identify the most probable events, links, and their importance on the failure propagation. The model was demonstrated with an ROV for deep arctic water subsea operations. The result identified the control system, communication linkages, human factor, among others, as most critical in the ROV operational failure. The methodology’s application provides core information on the Mean time between failure (MTBF) of the ROV system that could aid integrity management and provides a guide on early remedial action against total failure.

Double-Loop Sliding Mode Controller with An Ocean Current Observer for the Trajectory Tracking of ROV

To solve the trajectory tracking problem of insufficient response and the large tracking error of remotely operated vehicles (ROVs) under the interference of large ocean currents, this paper proposes a double-loop sliding mode controller with an ocean current observer. The designed controller consisted of an outer-loop controller (the position controller) and an inner-loop controller (the velocity controller): the outer controller was designed by the position error, and a reference velocity was created for the inner loop to achieve accurate positioning and attitude tracking. The reference control input was treated as a new target to design the inner-loop controller, enabling the ROV to achieve accurate reference velocity tracking. Based on the theoretical idea of active disturbance rejection control, a kinematic equation-based ocean current observer was designed to estimate and compensate for large unknown currents to ensure accurate trajectory tracking performance under large currents. The simulation results proved that the double-loop sliding-mode control scheme with an ocean current observer always showed good tracking performance, demonstrating the excellent control performance and high robustness of the scheme. Compared with the high-complexity control schemes such as neural network-based PID control or fuzzy sliding mode control, it effectively improves the robustness to ocean current disturbances without increasing the computational effort excessively, and is more practical in ROV systems with limited computational power.

Advances in Underwater Oil Plume Detection Capabilities

Historically, visual observation is an emergency responder's first ‘tool’ in identifying spilled oil. Optical detection has since expanded to include a myriad of signals from space, aircraft, drone, vessel and submersible platforms that can provide critical information for decision-making during spill response efforts. Spill monitoring efforts below the air-water interface have been vastly improved by advances with in situ optical sensors and vehicle platform technology. Optical techniques using fluorescence, scattering, and holography offer a means to determine dissolved versus droplet fractions, provide oil concentration estimates and serve as proxies for dispersion efficiency. For subsurface spills over large space and time scales, Autonomous Underwater Vehicles (AUVs) can be used to provide subsurface plume footprints and estimate oil concentrations. For smaller, more frequent spills, tethered compact Remotely Operated Vehicles (ROVs) may be more appropriate as they are easy to deploy for rapid detection. Two underwater oil detection technologies have been developed: (1) A Remote Environmental Monitoring UnitS (REMUS-600) AUV equipped with fluorescence and backscatter SeaOWL UV-A (Oil-in-Water Locator; Sea-Bird Scientific WET Labs Inc.), holographic imager (HoloCam; SeaScan, Inc), hydrographic information, video camera, CTD and a water/oil sampler. (2) A tethered ROV system (DTG2, Deep Trekker Inc.) equipped with video camera, UviLux (Chelsea Technologies Group, Inc) fluorometer, a CTD and water/oil sampler. Calibration and validation tests of the sensor suite were conducted at the Coastal Response Research Center flume tank (NH, USA). Oil concentration estimates were verified by chemical analysis of hydrocarbons and particle size analysis (LISST 200X, Sequoia, Inc). Operational performance of the ROV platform and sensors was evaluated at the Ohmsett wave tank (NJ, USA). Field performance of the REMUS and sensor suite was evaluated at natural seeps near Santa Barbara, CA. This research demonstrates the forensic value of in situ optical data for improved understanding of the behavior and transport of spilled oil below the air-sea interface.

Alternative configurations to optimize tension in the umbilical of a work class ROV performing ultra-deep-water operation

The utilization of ROV (Remotely Operated Vehicle) for subsea operation has been increasing in the past few years alongside the increasing use of subsea technologies in deep-water oil and gas activities and other maritime operations. While survey class ROVs have reached the deepest depth in the ocean, the work class ROVs are mostly limited to 3 km depth. For a work class ROV operating in deep waters, the excessive static tension due to self-weight of the ROV and its umbilical system leaves small room before the dynamic tension exceeds the safe working load of the umbilical. Snap loads can also exist in the low-tension area of the umbilical when the ROV system is under dynamic motions which can lead to a large tensile load in the line. Therefore, there is a need for a practical solution to ensure that the safe working load is not exceeded during ultra-deep-water operation.This study focuses in reducing the tension in the umbilical hence increasing the operational depth of a work class ROV from deep to ultra-deep waters. Three different configurations, namely the hook, hook & top floaters, and mid-depth hook are numerically investigated and compared with the conventional free-flying ROV configuration. Firstly, deep-water operation of a 3 km ROV system is simulated under combination of a real extreme vertical current profile and various irregular wave conditions. This shows negligible effect of the current profile on umbilical maximum tension.The study also shows that for 3 km ROV operation, the suggested hook configuration is sufficient to effectively reduce the tension load as well as reducing the possibility of snap in the umbilical. Using hook configuration in the umbilical has significant benefits in minimizing ROV motion and also filters out the destructive snap induced high frequency tension fluctuations in the umbilical. For 6 km operation, either hook & top floaters or mid-depth hook can be utilized whereas the mid-depth hook configuration provides a broader environmental operating window for ROV operation. However, installation of floaters on the umbilical to produce the mid-depth hook configuration increases the ROV offset.

A Systematic Review of Remotely Operated Vehicle Surveys for Visually Assessing Fish Assemblages

Anthropogenic activities and greater demands for marine natural resources has led to increases in the spatial extent and duration of pressures on marine ecosystems. Remotely operated vehicles (ROVs) offer a robust survey tool for quantifying these pressures and tracking the success of management intervention while at a range of depths, including those inaccessible to most SCUBA diver-based survey methods (∼>30 m). As the strengths, limitations, and biases of ROVs for visually monitoring fish assemblages remain unclear, this review aims to evaluate ROVs as a survey technique and to suggest optimal sampling strategies for use in typical ROV-based studies. Using the search engines Scopus™ and Google Scholar™, 119 publications were identified that used ROVs for visual surveys of fish assemblages. While the sampling strategies and sampling metrics used to annotate the imagery in these publications varied considerably, the total abundance of fish recorded over strip transects of varying dimensions was the most common sampling design. The choice of ROV system appears to be a strong indicator of both the types of surveys available to studies and the success of ROV deployments. For instance, larger, more powerful working-class systems can complete longer and more complex designs (e.g., swath, cloverleaf, and polygonal transects) at greater depths, whereas observation-class systems are less expensive and easier to deploy, but are more susceptible to delays or cancellations of deployments. In more severe sea state conditions, radial transects, or strip transects that employ live-boating or a weight to anchor the tether to the seafloor, can be used to improve the performance of observation-class systems. As these systems often employ shorter tethers, radial transects can also be used to maximize sampling area at greater depths and on large vessels that may rotate substantially while anchored. For highly mobile species, and in survey designs where individuals are likely to be recounted (e.g., transects along oil and gas pipelines), relative abundance (MaxN) may be a more robust sampling metric. By identifying subtle, yet important, differences in the application of ROVs as a tool for visually surveying deep-water marine ecosystems, we identified key areas for improvement for best practice for future studies.

A novel voltage regulation strategy for the electric power delivery system of a 6000-m ROV

Owing to the increasing demand for deep sea exploration, remotely operated vehicles (ROVs) that can conduct scientific tasks up to a depth of 6000 m are essential for exploring unknown areas. For electrically propelled ROVs, a voltage regulation system is used to maintain the load-side voltage within a limited range during power load variation. The load-side voltage fluctuated frequently during load variation, thus challenging the design of the voltage regulation system. Hence, we propose a novel voltage regulation strategy in the ship-side of a 6000-m-deep ROV system. In this strategy, the nonlinear relationship of the compensated voltage in the ship-side and the active current in the umbilical cable are solved by piecewise linear fitting using the least-squares method. Subsequently, a feedback PID controller is designed to achieve a faster dynamic response and maintain a stable load-side voltage. The real applications of the ROV system for oceanographic surveys demonstrated that the fast response and high accuracy of the voltage regulation system for intense fluctuations of the load-side voltage could be achieved.

Finite element cable-model for Remotely Operated Vehicles (ROVs) by application of beam theory

Increasing autonomy, efficiency and safety for Remotely Operated Vehicles (ROVs) is crucial for future subsea operations and requires accurate models for optimal control, operations and design. This involves precise modeling of the cable in conjunction with the ROV response. This paper presents a novel three-dimensional cable model for Remotely Operated Vehicles using Euler-Bernoulli beam theory. The presented model is implemented in Matlab and takes into account the most important effects related to the response of underwater cables and ROVs. Following beam theory bending stiffness is also included, making the model applicable for low tension scenarios. The presented model is modified to allow for compression of the cable. The resulting non-linear equations are discretized spatially by the Galerkin finite element method and solved temporally by the Newmark-β time integration scheme.The model is verified experimentally in ocean tank experiments on a real ROV system. A numerical example is presented and the results are compared to previous published results. Lastly, a sensitivity analysis for the hydrodynamic parameters is presented.

A System for Retrieval and Incubation of Benthic Sediment Cores at In Situ Ambient Pressure and under Controlled or Manipulated Environmental Conditions

AbstractThe investigation of benthic biodiversity and biogeochemical processes in the deep sea is complicated by the need to conduct experiments at in situ pressures. Recovery of sediment samples to the surface without maintaining full-depth ambient pressure may damage the organisms that are of interest or cause physiological changes that could influence the processes being studied. It is possible to carry out in situ experiments using remotely operated vehicles (ROVs) or lander systems. However, the costs and complexity of ROV operations are significant and, for both ROVs and landers, the complexity and repeatability of the experiments are subject to the limitations imposed by these platforms. A system is described—the Multi-Autoclave Corer Experiment (MAC-EXP)—that has been developed with the aim of offering a new experimental approach to investigators. The MAC-EXP system is designed to retrieve sediment cores from depths down to 3500 m and to seal them into pressure chambers before being recovered so that they are maintained at their normal ambient pressure. After recovery the core chambers can be connected to a laboratory incubation system that allows for experimentation on the sediment without loss of pressure and under controlled conditions of temperature and oxygen concentration. The system is relatively low cost when compared to ROV systems and can be deployed using methods and equipment similar to those used for routine deployments of small unpressurized multicorers. The results of sea trials are detailed.

Observer-Based Adaptive Neural Network Trajectory Tracking Control for Remotely Operated Vehicle.

This paper focuses on the adaptive trajectory tracking control for a remotely operated vehicle (ROV) with an unknown dynamic model and the unmeasured states. Unlike most previous trajectory tracking control approaches, in this paper, the velocity states and the angular velocity states in the body-fixed frame are unmeasured, and the thrust model is inaccurate. Obviously, it is more in line with the actual ROV systems. Since the dynamic model is unknown, a new local recurrent neural network (local RNN) structure with fast learning speed is proposed for online identification. To estimate the unmeasured states, an adaptive terminal sliding-mode state observer based on the local RNN is proposed, so that the finite-time convergence of the trajectory tracking error can be guaranteed. Considering the problem of inaccurate thrust model, an adaptive scale factor is introduced into thrust model, and the thruster control signal is considered as the input of the trajectory tracking system directly. Based on the local RNN output, the adaptive scale factor, and the state estimation values, an adaptive trajectory tracking control law is constructed. The stability of the trajectory tracking control system is analyzed by the Lyapunov theorem. The effectiveness of the proposed control scheme is illustrated by simulations.

Time Domain Modeling of ROV Umbilical using Beam Equations

Abstract: This paper presents a finite element model for representing the cable dynamics of a typical ROV(Remotely Operated Vehicle) umbilical. The goal is to produce a model able to capture the most important dynamic effects of the umbilical affecting the ROV by solving the Euler-Bernoulli beam equations using finite element method. The model is general and is applicable to a wide variety of deep-sea ROV systems. The presented model is demonstrated by numerical examples for umbilical and ROV systems, both for steady state and dynamic response. The model is further validated by comparison with published results.

Failure Analysis of Fasteners in a Remotely Operated Vehicle (ROV) System

A failure analysis study was carried out on AISI 204 Cu stainless steel full-threaded fasteners and end-threaded SS 316L fasteners used in a deep water work class ROV system. The AISI 204 Cu stainless steel full-threaded fasteners were used in a Ti–6Al–4V alloy pressure case. The end-threaded SS 316L fasteners were used for attaching the bottom fender in the tether management system (TMS) made of Al 6061-T6 alloy. The mechanical property of both the fasteners was found to be within standard specification. The SEM study of the full-threaded fasteners revealed that the corrosion pit formation in the unfractured interface area is the cause of crack initiation. Subsequently, the crack propagated by stress corrosion cracking and finally, failed by fast overload cleavage fracture. It can be reasoned that a lower wt.% of molybdenum in AISI 204 Cu stainless steel reduced the pitting corrosion resistance of the full-threaded fasteners. The end-threaded fastener failed by stress corrosion cracking, but corrosion pit was not found in the fracture surface, due to the lack of its interface area with the unfractured region. It can be inferred that the chlorine ions of seawater break the oxide film of stainless steel bolts to form corrosion pits. These corrosion pits act as a stress concentration point to initiate a crack, and subsequently the bolts fail by stress corrosion cracking, showing a brittle appearance.

A geometrically exact formulation for three-dimensional numerical simulation of the umbilical cable in a deep-sea ROV system

This paper proposes a geometrically exact formulation for three-dimensional static and dynamic analyses of the umbilical cable in a deep-sea remotely operated vehicle (ROV) system. The presented formulation takes account of the geometric nonlinearities of large displacement, effects of axial load and bending stiffness for modeling of slack cables. The resulting nonlinear second-order governing equations are discretized spatially by the finite element method and solved temporally by the generalized-α implicit time integration algorithm, which is adapted to the case of varying coefficient matrices. The ability to consider three-dimensional union action of ocean current and ship heave motion upon the umbilical cable is the key feature of this analysis. The presented formulation is firstly validated, and then three numerical examples for the umbilical cable in a deep-sea ROV system are demonstrated and discussed, including the steady configurations only under the action of depth-dependent ocean current, the dynamic responses in the case of the only ship heave motion, and in the case of the combined action of the ship heave motion and ocean current.

Una arquitectura para el diseño conceptual de vehículos para exploración subacuática

Este artículo presenta una arquitectura para el diseño conceptual de vehículos subacuáticos operados remotamente (ROV). La arquitectura propuesta está basada en una revisión extensa de literatura y la experiencia obtenida durante 20 años con el desarrollo de tres sistemas ROV diseñados para misiones de inspección subacuática. El ROV se divide en cinco subsistemas: vehículo, estación en superficie, interfaz superficie/vehículo, sistema de control y software. Para cada uno de estos subsistemas se definen funciones y tareas, se enuncian componentes, se establecen interrelaciones con otros subsistemas y se plantean alternativas comúnmente utilizadas. La delimitación de los subsistemas desde el diseño conceptual busca evitar problemas en las fases avanzadas del desarrollo del sistema robótico de exploración.

Dynamics analysis of planar armored cable motion in deep-sea ROV system

The armored cable used in a deep-sea remotely operated vehicle (ROV) may undergo large displacement motion when subjected to dynamic actions of ship heave motion and ocean current. A novel geometrically exact finite element model for two-dimensional dynamic analysis of armored cable is presented. This model accounts for the geometric nonlinearities of large displacement of the armored cable, and effects of axial load and bending stiffness. The governing equations are derived by consistent linearization and finite element discretization of the total weak form of the armored cable system, and solved by the Newmark time integration method. To make the solution procedure avoid falling into the local extreme points, a simple adaptive stepping strategy is proposed. The presented model is validated via actual measured data. Results for dynamic configurations, motion and tension of both ends of the armored cable, and resonance-zone are presented for two numerical cases, including the dynamic analysis under the case of only ship heave motion and the case of joint action of ship heave motion and ocean current. The dynamics analysis can provide important reference for the design or product selection of the armored cable in a deep-sea ROV system so as to improve the safety of its marine operation under the sea state of 4 or above.

Imaging and sampling beneath free-drifting icebergs with a remotely operated vehicle

A commercially available, small (less than 100-kg), remotely operated vehicle (ROV) was modified to image and sample the marine ecosystem surrounding free-drifting icebergs east of the Antarctic Peninsula during three field expeditions in 2005, 2008 and 2009. Modifications included fitting the vehicle with an accessory tool sled, additional thrusters, flotation and significant changes to internal wiring to support a wide array of sensors and samplers. The ROV was re-configured aboard the R/V Nathaniel B. Palmer to perform either general exploration and biological sampling (Bio dives) or water sampling (Chemistry dives). In-situ sensors and a suction sampler were used for Bio dives while a suction pump and hose were fastened along the full length of the ROV tether to enable continuous water sampling adjacent to each iceberg during Chemistry-dives. Details of the ROV system are presented along with a discussion of the 18 dives that explored the sides and bottoms of six different icebergs during the 2009 field expedition.

Intelligent UUVs: Some issues on ROV dynamic positioning

Intelligent unmanned underwater vehicles (UUVs) fall under two main group categories: the remotely operated vehicles (ROVs), which are characterized by remote operation and presence of a tether cable; and the autonomous underwater vehicles (AUVs), which are characterized by their autonomous behavior and absence of a tether cable. One fundamental issue of the UUV design is the dynamic position control system. This system plays a crucial role together with the sensor architecture in the degree of system autonomy that can be achieved. This paper is concerned with a few issues when dynamically positioning remotely operated underwater vehicles (ROVs). By restricting the operating regime of ROVs to slow velocity requirements the paper investigates the implementation of a few decentralized control strategies and compare their performance measures, which are assessed by simulating a nonlinear ROV system model for each control strategy. Issues concerning input tracking, disturbance rejection, and plant variations are discussed. The evaluations consider the use of linear PID feedback and feedforward variants, and a robust nonlinear control strategies applied to a full order, fully coupled, and nonlinear vehicle model. These evaluations consider a vehicle undertaking standard mission activities where the tether cable dynamics, with load estimates obtained from a lumped mass cable model, and the vehicle actuator system are present. The paper shows that much of the performance deterioration may be attributed mainly due to cable inertia. The authors also verify that the nonlinear robust control strategy does not necessarily allow for better performance over the linear feedback control strategies implemented when vehicle motions are confined to slow velocity profiles. These and other partial results will aid the design of the control system for an underwater vehicle currently under construction

MODUS: Space Shuttle for Deep-Water Operations

This paper presents MObile Docker for Underwater Sciences (MODUS), a specialized remotely operated vehicle (ROV) for deployment, recovery, and servicing of heavy sea bottom stations, for example, scientific observatories for deep-water application (depth rated 4,000 m). Developed, built, and tested as part of the EC-funded project GEophysical and Oceanographic STation for Abyssal Research (GEOSTAR 2001), the new ROV system includes the operating vessel with winch and umbilical and the versatile "space shuttle" MODUS for handling the bottom station with modularized payload. The paper focuses on aspects of the development as well as open water trials and missions. Results from hydrodynamic analyses are presented to illustrate design studies for minimized structure drag and therefore minimized power requirements for thruster-driven horizontal movements. Motion analyses comprise the dynamic behavior of the ship and the entire deep-dived system considering hydroelastic effects. Due to the direct coupling, vertical excitations of the ship in the prevailing sea are substantially transmitted along the submerged umbilical to the ROV, causing potentially harmful slack cable situations. Results from numerical simulations illustrate the dynamic response of the system due to ship oscillations in random seas and the associated downtime of MODUS operations. The paper presents the latest technological and scientific applications of MODUS during its first cruises: Reaching depths of 3,700 m within the EC-funded projects GEOSTAR and BIOtechnology from the DEEP (BIODEEP) in the Mediterranean Sea demonstrates its high availability with reliable performance and low costs.