Umbilical Cable Research Articles

Electromagnetic Analysis of Submarine Umbilical Cables With Complex Configurations

These studies present the electromagnetic analyses of different configurations of the so called “Integrated Production Umbilical,” or simply Umbilical Cables. Modern Umbilical Cables can have more than 4 independent 3-phase power circuits as well as steel tubes. There is no 2-D symmetry for these cable configurations and the 3-D simulations are very undesirable due to cable length. The adopted methodology to evaluate cable performance is a combination of 2-D-finite element analyses (coupled with electric circuit) and the transposition technique. The results have shown that the configuration B in which all power circuits rotates along its own center has better performance considering the load terminal voltages due to the compensation of the induction effect along the cable.

Comparing ability to complete simple tele‐operated rescue or maintenance mobile‐robot tasks with and without a sensor system

PurposeThe purpose of this paper is to investigate the effect on completion of mobile‐robot tasks depending on how a human tele‐operator interacts with a sensor system and a mobile‐robot.Design/methodology/approachInteraction is investigated using two mobile‐robot systems, three different ways of interacting with the robots and several different environments of increasing complexity. In each case, the operation is investigated with and without sensor systems to assist an operator to move a robot through narrower and narrower gaps and in completing progressively more complicated driving tasks. Tele‐operators used a joystick and either watched the robot while operating it, or sat at a computer and viewed scenes remotely on a screen. Cameras are either mounted on the robot to view the space ahead of the robot or mounted remotely so that they viewed both the environment and robot. Every test is compared with sensor systems engaged and with them disconnected.FindingsA main conclusion is that human tele‐operators perform better without the assistance of sensor systems in simple environments and in those cases it may be better to switch‐off the sensor systems or reduce their effect. In addition, tele‐operators sometimes performed better with a camera mounted on the robot compared with pre‐mounted cameras observing the environment (but that depended on tasks being performed).Research limitations/implicationsTele‐operators completed tests both with and without sensors. One robot system used an umbilical cable and one used a radio link.Practical implicationsThe paper quantifies the difference between tele‐operation control and sensor‐assisted control when a robot passes through narrow passages. This could be an useful information when system designers decide if a system should be tele‐operated, automatic or sensor‐assisted. The paper suggests that in simple environments then the amount of sensor support should be small but in more complicated environments then more sensor support needs to be provided.Originality/valueThe paper investigates the effect of completing mobile‐robot tasks depending on whether a human tele‐operator uses a sensor system or not and how they interact with the sensor system and the mobile‐robot. The paper presents the results from investigations using two mobile‐robot systems, three different ways of interacting with the robots and several different environments of increasing complexity. The change in the ability of a human operator to complete progressively more complicated driving tasks with and without a sensor system is presented and the human tele‐operators performed better without the assistance of sensor systems in simple environments.

Deep-sea technology

As oil companies venture deeper into the oceans, they are having to install production equipment in dark, freezing conditions and under crushing pressures on the seabed. Commercial divers cannot operate in such a hostile environment, so expensive remotely controlled underwater vehicles operated via an umbilical cable that stretches perhaps a couple of kilometres from a support vessel to the sea floor must be used to maintain ever more complex equipment. However, a more cost-effective solution for light intervention tasks may soon be provided in the form of vehicles that 'fly' to work sites without connection to the surface. Subsea production systems are designed to be as simple and reliable as possible. They are built up from modules, which can be retrieved for repair. Problems with hydraulic systems, which are susceptible to fluid leaks and hydraulic contamination, are a particular worry, because of the environmental damage they cause. Seabed Rig AS is taking on a truly awesome challenge in developing a submerged autonomous seabed drilling rig. They spent the last three years developing this technology with assistance from the oil-giant Statoil. In May 2009, Seabed Rig licensed technology and contracted with Energid Technologies Corporation to create a robot control system for the subsea operations.

Analysis of the effects of time delays on the teleoperation of a mobile robot in various modes of operation

PurposeThe purpose of this paper is to investigate the effect of time delay on the ability of a human operator to complete a task with a teleoperated mobile‐robot using two systems, two different ways of interacting with the mobile‐robots and several different environments.Design/methodology/approachTeleoperators are observed completing a series of tasks using a joystick to control a mobile‐robot while time delays are introduced to the system. They sit at a computer and view scenes remotely on a screen. Cameras are either mounted on the robot or mounted externally so that they view both the environment and robot. Teleoperators complete the tests both with and without sensors. One robot system uses an umbilical cable and one uses a radio link.FindingsIn simple environments, a teleoperator may perform better without a sensor system to assist them but as time delays are introduced then there are more failures. In more complicated environments or when time delays are longer, then teleoperators perform better with a sensor system to assist. Teleoperators may also tend to perform better with a radio link than with an umbilical connection.Research limitations/implicationsTeleoperated systems rely heavily on visual feedback and experienced operators. This paper investigates the effect of introducing a delay to the delivery of that visual feedback.Practical implicationsThe paper suggests that in simple environments with short time delays then the amount of sensor support should be small but in more complicated environments or with longer delays then more sensor support needs to be provided.Originality/valueResults from imposing time delays on a teleoperated mobile‐robot are presented. Effects on the task of different ways of viewing activity on a computer display are presented, that is with cameras mounted on the robot or cameras mounted externally to view both the environment and robot. Results from using sensors to assist teleoperators are presented. The paper suggests that the amount of sensor support should be varied depending on circumstances.

A Finite-Element Approach for Calculating Electrical Parameters of Umbilical Cables

This paper presents a systematic approach for calculating electrical per-unit-length parameters of signal cables by the finite-element method. The associated software (UFIELD) has been specifically adapted to umbilical cables used in offshore control applications. Efficient and robust case specification is achieved through a library of predefined, parametrized models for the umbilical elements (signal cables, pipes, armors). Additional features include automated specification of boundary conditions and excitations, adaptive mesh generation, and the handling of twisted elements and layers. The approach is validated against analytical solutions. Application to the Snohvit control umbilical shows excellent agreement with measured signal parameters, for the triad element alone, and for the triad element inside the umbilical. Similar results are obtained for the Ormen Lange quad element.

Comparing speed to complete progressively more difficult mobile robot paths between human tele‐operators and humans with sensor‐systems to assist

PurposeThe purpose of this paper is to investigate the effect on time to complete a task depending on how a human operator interacts with a mobile‐robot. Interaction is investigated using two tele‐operated mobile‐robot systems, three different ways of interacting with robots and several different environments. The speed of a tele‐operator in completing progressively more complicated driving tasks is investigated also.Design/methodology/approachTele‐operators are timed completing a series of tasks using a joystick to control a mobile‐robot. They either watch the robot while operating it, or sit at a computer and view scenes remotely on a screen. Cameras are either mounted on the robot, or so that they view both the environment and robot. Tele‐operators complete tests both with and without sensors. One robot system uses an umbilical cable and one uses a radio link.FindingsIn simple environments, a tele‐operator may perform better without a sensor system to assist them but in more complicated environments then a tele‐operator may perform better with a sensor system to assist. Tele‐operators may also tend to perform better with a radio link than with an umbilical connection. Tele‐operators sometimes perform better with a camera mounted on the robot compared with pre‐mounted cameras observing the environment (but that depends on tasks being performed).Research limitations/implicationsTele‐operated systems rely heavily on visual feedback and experienced operators. This paper investigates how to make tasks easier.Practical implicationsThe paper suggests that the amount of sensor support should be varied depending on circumstances.Originality/valueResults show that human tele‐operators perform better without the assistance of a sensor systems in simple environments.

On the Behavior of an Underwater Remotely Operated Vehicle in a Uniform Current

This paper presents a series of analyses on the behavior of an underwater remotely operated vehicle (ROV) with the umbilical cable in uniform current. The hydrodynamic mathematical model including the coupled effect of the current and the umbilical cable is proposed here to deal with 6 degrees of freedom motions of the ROV. Because of the umbilical cable on the ROV, the present problem is the two-point boundary value problem with respect to a set of first-order ordinary differential equation systems, which are solved by applying the multistep shooting method. The corresponding hydrodynamic coefficients of the underwater vehicle used in the hydrodynamic model are obtained by the planar motion mechanism (PMM) test technique. Three different current speeds are considered to investigate the current effect on the ROV's operations including forward motion, ascending motion, and descending motion. The present results reveal that the current indeed significantly affects the operations of the ROV, and the mathematical numerical model developed here can serve as a useful tool to offer some valuable information for the anticurrent ROV design.

Autonomous underwater vehicles (AUVs) and investigations of the ice–ocean interface in Antarctic and Arctic waters

AbstractLimitations of access have long restricted exploration and investigation of the cavities beneath ice shelves to a small number of drillholes. Studies of sea-ice underwater morphology are limited largely to scientific utilization of submarines. Remotely operated vehicles, tethered to a mother ship by umbilical cable, have been deployed to investigate tidewater-glacier and ice-shelf margins, but their range is often restricted. The development of free-flying autonomous underwater vehicles (AUVs) with ranges of tens to hundreds of kilometres enables extensive missions to take place beneath sea ice and floating ice shelves. Autosub2 is a 3600 kg, 6.7 m long AUV, with a 1600 m operating depth and range of 400 km, based on the earlier Autosub1 which had a 500 m depth limit. A single direct-drive d.c. motor and five-bladed propeller produce speeds of 1–2 m s−1. Rear-mounted rudder and stern-plane control yaw, pitch and depth. The vehicle has three sections. The front and rear sections are free-flooding, built around aluminium extrusion space-frames covered with glass-fibre reinforced plastic panels. The central section has a set of carbon-fibre reinforced plastic pressure vessels. Four tubes contain batteries powering the vehicle. The other three house vehicle-control systems and sensors. The rear section houses subsystems for navigation, control actuation and propulsion and scientific sensors (e.g. digital camera, upward-looking 300 kHz acoustic Doppler current profiler, 200 kHz multibeam receiver). The front section contains forward-looking collision sensor, emergency abort, the homing systems, Argos satellite data and location transmitters and flashing lights for relocation as well as science sensors (e.g. twin conductivity–temperature–depth instruments, multibeam transmitter, sub-bottom profiler, AquaLab water sampler). Payload restrictions mean that a subset of scientific instruments is actually in place on any given dive. The scientific instruments carried on Autosub are described and examples of observational data collected from each sensor in Arctic or Antarctic waters are given (e.g. of roughness at the underside of floating ice shelves and sea ice).

A Nonlinear Analysis Formulation for Bend Stiffeners

Bend stiffeners are polymeric structures with a conical shape designed to limit the curvature of flexible risers and umbilical cables at their uppermost connections, protecting them against overbending and from accumulation of fatigue damage. Thus, they are of vital importance to deep water oil and gas production systems. This work develops a mathematical formulation and a numerical solution procedure for the geometrical and material nonlinear analysis of the riser/bend stiffener system considered as a beam bending model. The structures are separately modeled, which allows the numerical calculation of the contact force along the system arc length. The governing differential equations are derived considering geometrical compatibility, equilibrium of forces and moments, and nonlinear asymmetric material constitutive relations, which leads to a shift in the neutral axis position from the cross-section centroid. The eccentricity and the bending moment versus curvature relation for each cross section are numerically calculated and then expressed by a polynomial power series expansion. A set of four first-order nonlinear ordinary differential equations is written and four boundary conditions are specified at both ends. Once the global problem is solved, the contact force may be promptly calculated. A finite difference method is implemented in Fortran code to obtain the numerical solution. A case study is carried out where linear elastic symmetric and nonlinear elastic asymmetric constitutive models are compared and discussed. The results are presented for the riser/bend stiffener deflected configuration, angle, curvature, and contact force distribution. The results demonstrate that an accurate structural analysis of bend stiffeners depends on a precise assessment of the nonlinear asymmetric polyurethane property.

Cyclic loading and marine environment effects on the properties of HDPE umbilical cables

This work presents a study of the effects of cyclic loading and marine environment on the mechanical properties of high-density polyethylene (HDPE) used in the external layer of submarine cables. Two different types of samples were tested. The first type was tested in the as-received condition whereas the second one was taken from the cyclic-loaded material. The cyclic-load test was carried out in a device, according to the API 17E standard (API 17E-98, Specification for sub sea production control umbilicas). These samples were submitted to a process of artificial aging. All the specimens were submitted to tensile test and the analysis and comparison of the results showed that HDPE suffered alterations in its mechanical behavior, especially the material submitted to cyclic loading. Both aged and as-received samples were observed by using scanning electron microscopy and their hardness was also measured. The results showed that the cyclic loading, the seawater and the ultraviolet radiations accelerated the degradation process of HDPE.

Post-buckling behaviour of slender structures with a bi-linear bending moment–curvature relationship

Certain classes of slender structures of complex cross-section or fabricated from specialised materials can exhibit a bi-linear bending moment–curvature relationship that has a strong influence on their global structural behaviour. This condition may be encountered, for instance, in (a) non-linear elastic or inelastic post-buckling problems if the cross-section stiffness may be well approximated by a bi-linear model; (b) multi-layered structures such as stranded cables, power transmission lines, umbilical cables and flexible pipes where the drop in the bending stiffness is associated with an internal friction mechanism. This paper presents a mathematical formulation and an analytical solution for such slender structures with a bi-linear bending moment versus curvature constitutive behaviour and subjected to axial terminal forces. A set of five first-order non-linear ordinary differential equations are derived from considering geometrical compatibility, equilibrium of forces and moments and constitutive equations, with hinged boundary conditions prescribed at both ends, resulting a complex two-point boundary value problem. The variables are non-dimensionalised and solutions are developed for monotonic and unloading conditions. The results are presented in non-dimensional graphs for a range of critical curvatures and reductions in bending stiffness, and it is shown how these parameters affect the structure's post-buckling behaviour.

Automatic Control and Guidance Method of ROV with Umbilical Cable

For the remotely operated vehicle (ROV) with an umbilical cable, it becomes difficult to guide it to a target as the depth increases. Especially, the vehicle for the working in the deep sea under current disturbance, the control to reach the target is the most important and difficult problem, because the tension of the umbilical cable, which connects the vehicle to the mother ship, becomes extremely large by current force. The author proposes the algorithm for automatic control and guidance to reach the target in the sea under the restriction of actuator's maximum force. The application was successfully conducted to ROV with umbilical cable as a basic control algorithm

Numerical stability analysis and control of umbilical–ROV systems in one-degree-of-freedom taut–slack condition

In this paper, the stability of an umbilical–ROV system under nonlinear oscillations in heave motion is analyzed using numerical methods for the uncontrolled and controlled cases comparatively. Mainly the appearance of the so-called taut–slack phenomenon on the umbilical cable produced by interactions of monochromatic waves and an operated ROV is specially focused. Nonlinear elements were considered as nonlinear drag damping, bilinear restoring force and saturation of the actuators. Free-of-taut/slack stability regions are investigated in a space of physical bifurcation parameters involving a set of both operation and design parameters. They indicate a wide diversity in qualitative behaviors, both in the periodicity and possible routes to chaos from the stability regions to outside. For detection of periodicity of the nonlinear oscillations inside and outside the stability regions, a method based on Cauchy series is developed. The first part of the results is dedicated to the stability of the uncontrolled dynamics. These results suggest the design of a control system that is able to counteract hefty hauls of the cable during the sinking/lifting operation under perturbation. A combination of a force and cinematic controller based on nonlinear model–reference control is proposed. Through a comparative study of the stability regions for uncontrolled and controlled dynamics, it is shown that the control system can extend considerably these regions without appearance of the taut–slack phenomenon despite the presence of wave perturbations. The limits between the taut and taut–slack zones are defined by the wave steepness and the available energy of the actuators.

On the motions of the underwater remotely operated vehicle with the umbilical cable effect

In this paper, a hydrodynamic model is developed to simulate the six degrees of freedom motions of the underwater remotely operated vehicle (ROV) including the umbilical cable effect. The corresponding hydrodynamic forces on the underwater vehicle are obtained by the planar motion mechanism test technique. With the relevant hydrodynamic coefficients, the 4th-order Runge–Kutta numerical method is then adopted to solve the equations of motions of the ROV and the configuration of the umbilical cable. The multi-step shooting method is also suggested to solve the two-end boundary-value problem on the umbilical cable with respect to a set of first-order ordinary differential equation system. All operation simulations for the ROV including forward moving, ascending, descending, sideward moving and turning motions can be analyzed, either with or without umbilical cable effect. The current effect is also taken into consideration. The present results reveal that the umbilical cable indeed significantly affects the motion of the ROV and should not be neglected in the simulation.

1P1-E25 水中ロボットを追跡する水上支援機を利用した水中ロボットシステムの提案

Underwater robots can play a significant role in the investigations of underwater environment. However, conventional underwater robot systems that consist of underwater robot, operator and huge support ship have some problems such as propagation loss of acoustic wave, constraint of underwater robot behavior by umbilical cable. In this research, underwater robot systems with a Surface Support Vehicle that tracks an underwater robot are proposed. The Surface Support Vehicle is a compact surface vehicle having the functions of support ship and tracks an underwater robot autonomously. By installation of the Surface Support Vehicle, the problems of conventional underwater robot systems are resolved, and novel operation methods are realized. In this paper, the advantages of installation of the Surface Support Vehicle are explained and a effectiveness of the Surface Support Vehicle is verified by the experimental results in actual environment.

Inspection of ship hulls using automated ultrasonic inspection

The main objective of this paper is to extend the authors' last work (1) , which described an automated ultrasonic system developed for the non-destructive underwater inspection of defects caused by corrosion on hulls of floating units employed in the offshore oil industry. The main advantages of this system are that it can be carried out without production stoppages and the oil storage tanks do not need to be emptied during the hull inspection process. The inspection system is made up of a mobile vehicle with magnetic wheels that secure it to the ship hull and an ultrasound pulse-echo apparatus, which provides a non-destructive technique in an immersed state. The vehicle is remotely controlled by means of an umbilical cable. The ultrasound inspection results are shown in A, B, C and D-scan images. In this paper the first results obtained by this system are described. The laboratory and field results showed that this system is effective for this purpose.

Remotely Operated Vehicles

An ROV comprising a topside, a fish and an umbilical cable for connecting the topside and the fish together. The fish is adapted to be powered by an onboard battery inductively coupled to the fish. The cable is of a fine diameter to reduce drag through the water. RF transmissions carry control and return signals to and from the fish and topside. The fish has two cameras. The front facing camera is located behind a dual layer flooded dome. A pan and tilt mechanism is fitted to one of the cameras and uses a pivotable gimbal frame driven by a lead nut moving along an arcuate bolt.

Optical calibration hardware for the Sudbury Neutrino Observatory

The optical properties of the Sudbury Neutrino Observatory (SNO) heavy water Cherenkov neutrino detector are measured in situ using a light diffusing sphere (“laserball”). This diffuser is connected to a pulsed nitrogen/dye laser via specially developed underwater optical fibre umbilical cables. The umbilical cables are designed to have a small bending radius, and can be easily adapted for a variety of calibration sources in SNO. The laserball is remotely manipulated to many positions in the D 2 O and H 2 O volumes, where data at six different wavelengths are acquired. These data are analysed to determine the absorption and scattering of light in the heavy water and light water, and the angular dependence of the response of the detector's photomultiplier tubes. This paper gives details of the physical properties, construction, and optical characteristics of the laserball and its associated hardware.

Acoustic source array system module for underwater operation which can be installed on a motorized boat

A small boat or launch such as a motorized reinforced hull inflatable boat provides a platform for an acoustic source array of airguns. The array is made up as a ladder structure in which the airguns are disposed horizontally between vertical support and umbilical lines, preferably with their discharge ports in laterally offset or staggered relationship to minimize undesirable interactions between the acoustic transmissions released into the water by the sources and to help maximize the acoustic output of the array for a given array length. A structure stows the array on the boat for transport when the array is not deployed for use. If desired, the stowed array may be substantially enclosed by the hull of the boat. The stowage structure is preferable defined by a track or rails on the top of the deck. Umbilical cables attached to the array are translated, as by being wound on a drum and unwound therefrom, to deploy or retrieve the array over the stern of the boat. The umbilicals provide power (compressed air to the airguns and control signals for timed actuation of the guns). The array may be part of a module which includes a winch for winding and unwinding the umbilicals to retrieve and deploy the array. The array system also includes a compressor for supplying compressed air to the airguns of the array.

Non-Linear Analysis of Bend Stiffeners

This paper presents a mathematical formulation and a numerical solution for the geometrical and material non-linear analysis of bend stiffeners employed to protect the upper terminations of flexible risers and subsea umbilical cables. The governing differential equations result from considering geometrical compatibility, equilibrium of forces and moments and material constitutive relations, which can be linear elastic symmetric or non-linear elastic asymmetric. In this latter case, the bending moment versus curvature for each cross-section is calculated and then expressed by a polynomial power series expansion. Hence, a set of four first order non-linear ordinary differential equations may be written and four boundary conditions are defined at both ends. A one-parameter shooting method is employed and results are presented for a case study where linear elastic symmetric and non-linear elastic asymmetric constitutive models are compared and discussed. The results are also compared with finite element modeling for linear elastic materials. It is shown that an accurate analysis of bend stiffeners depends on a precise assessment of the material constitutive property.