Underwater vehicle

Details Underwater vehicle Underwater vehicle

1999-09-20

2001-01-02

Sotelo, Jesus D. (Department: 3617)

Ships

Submersible device

Detachably connected to a main vessel

C114S245000

Utility Patent

active

06167831

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
(Not Applicable)
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
(Not Applicable)
FIELD OF THE INVENTION
The invention relates to the field of vehicles for servicing and operating equipment in deep water and methods for utilizing such vehicles. More particularly, the invention relates to underwater vehicles having a tether management system and a detachable flying craft for use in deep water.
BACKGROUND OF THE INVENTION
Vehicles that operate underwater are useful for performing tasks below the sea surface in such fields as deep water salvage, the underwater telecommunications industry, the offshore petroleum industry, offshore mining, and oceanographic research. (See, e.g., U.S. Pat. Nos. 3,099,316 and 4,502,407). Conventional unmanned subsurface vehicles can be broadly classified according to how they are controlled. Autonomous underwater vehicles (AUVs) are subsurface vehicles that are not physically connected to a support platform such as a land-based platform, an offshore platform, or a sea-going vessel. In comparison, remotely operated vehicle (ROVs) are those subsea vehicles that are physically connected to a support platform.
The typical physical connection between an ROV and a support platform is referred to as an “umbilical.” The umbilical is usually an armored or unarmored cable containing an electrical and/or hydraulic conduit for providing power to an ROV and a data communications conduit for transmitting signals between an ROV and a support platform. An umbilical thus provides a means for remotely controlling an ROV during underwater operation.
ROVs are commonly equipped with on-board propulsion systems, navigation systems, communication systems, video systems, lights, and mechanical manipulators so that they can move to an underwater work site and perform a particular task. For example, after being lowered to a subsurface position, a remotely-located technician or pilot can utilize an ROV's on-board navigation and communications systems to “fly” the craft to a worksite. The technician or pilot can then operate the mechanical manipulators or other tools on the ROV to perform a particular job. In this manner, ROVs can used to perform relatively complex tasks including those involved in drill support, construction support, platform cleaning and inspection, subsurface cable burial and maintenance, deep water salvage, remote tool deployment, subsurface pipeline completion, subsurface pile suction, etc. Although they are quite flexible in that they can be adapted to perform a wide variety of tasks, ROVs are also fairly expensive to operate as they require a significant amount of support, including, for example, a pilot, technicians, and a surface support platform.
ROVs and other subsurface vehicles that are connected to a surface vessel by a physical linkage are subject to heave-induced damage. Heave is the up and down motion of an object produced by waves on the surface of a body of water. Underwater vehicles physically attached to a floating surface platform therefore move in accord with the surface platform. Therefore, when an underwater vehicle is located near a fixed object such as the sea bed, a pipeline, or a wellhead, heave-induced movement can damage both the vehicle and the fixed object. To alleviate this problem, devices such as heave-induced motion compensators and tether management systems have been employed to reduce the transfer of heave to underwater vehicles.
In contrast to ROVs, while underwater, AUVs are not subject to heave-mediated damage because they are not usually physically connected to a support platform. Like ROVs, AUVs are useful for performing a variety of underwater operations. Common AUVs are essentially unmanned submarines that contain an on-board power supply, propulsion system, and a pre-programmed control system. In a typical operation, after being placed in the water from a surface platform, an AUV will carry out a pre-programmed mission, then automatically surface for recovery. In this fashion, AUVs can perform subsurface tasks without requiring constant attention from a technician. AUVs are also substantially less expensive to operate than ROVs because they do not require an umbilical connection to an attached surface support platform.
AUVs, however, have practical limitations rendering them unsuitable for certain underwater operations. For example, power in an AUV typically comes from an on-board power supply such as a battery. Because this on-board power supply has a limited capacity, tasks requiring a substantial amount of power such as cutting and drilling are not practically performed by AUVs. In addition, the amount of time that an AUV can operate underwater is limited by its on-board power supply. Thus, AUVs must surface, be recovered, and be recharged between missions- a procedure which risks damage to the AUV and mandates the expense of a recovery vessel (e.g., a boat).
Another drawback of AUVs is that, without a physical link to a surface vessel, communication between an AUV and a remote operator (e.g., a technician) is limited. For example, AUVs conventionally employ an acoustic modem for communicating with a remote operator. Because such underwater acoustic communications do not convey data as rapidly or accurately as electrical wires or fiber optics, transfer of data encoding real time video signals or real time instructions from a remote operator is not efficient given current technology. As such, AUVs are often not able to perform unanticipated tasks or jobs requiring a great deal of operator input.
Other underwater vehicles having characteristics similar to AUVs and/or ROVs are known. These vehicles also suffer drawbacks such as subjection to heave, need for expensive support, poor suitability for some applications, lack of a continuous power supply, poor communications, poor capabilities, etc. Therefore, a need exists for a device to help overcome these limitations.
SUMMARY
The present application is directed to an underwater vehicle for performing subsurface tasks, and/or for interfacing with, transferring power to, and sharing data with other underwater devices. The vehicle within the invention includes a detachable flying craft for performing an underwater operation or for servicing and operating various subsurface devices such as toolskids, ROVs, AUVs, pipeline sections (spool pieces), seabed anchors, suction anchors, oil field production packages, and other equipment such as lifting frames, etc. The underwater vehicle also includes a tether management system for deploying and retrieving a tether that connects the tether management system to the detachable flying craft.
The detachable flying craft is a highly maneuverable, remotely-operable underwater vehicle that may have a manipulator or tool attached to it for performing a particular manual job. For example, the tool may be a drill for drilling, a saw for cutting, a grasping arm for manipulating components of an underwater object, etc. The detachable flying craft may also feature a connector adapted to “latch” on to or physically engage a receptor on a subsurface device. In addition to stabilizing the interaction of the detachable flying craft and the subsurface device, the connector-receptor engagement can also be utilized to transfer power and data. In this aspect, the detachable flying craft is therefore essentially a flying power outlet and/or a flying data modem.
The tether management system of the underwater vehicle regulates the quantity of free tether between itself and the detachable flying craft. It thereby permits the underwater vehicle to switch between two different configurations: a “closed configuration” in which the tether management system physically abuts the detachable flying craft; and an “open configuration” in which the tether management system and detachable flying craft are separated by a length of tether. In the open configuration, slack in the tether allows the detachable flying craft to move independently of the tether management system. Thus, where the tether management

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