SEISMIC AUTONOMOUS UNDERWATER VEHICLE
Apparatuses, systems, and methods for the deployment of a plurality of seismic autonomous underwater vehicles (AUVs) on or near the seabed. In one embodiment, the AUV comprises a buoyant body coupled to a pressure vessel that contains substantially all of the AUV's electronic components. The pressure vessel may comprise a plurality of composite components coupled together by a metallic ring to provide a substantially cylindrical shape to the pressure vessel. The AUV body provides lift to the AUV during lateral movement and compensates for an overall negative buoyancy of the AUV. The AUV may include a plurality of thrusters for propulsion. A vertical thruster may be used to create an upwards attack angle during takeoff and to maintain depth and orientation during flight. During normal flight operations, the AUV is configured to travel horizontally and vertically in a body of water by using only the horizontal thrusters.
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The present application is a continuation of U.S. patent application Ser. No. 15/292,816, filed on Oct. 13, 2016, which claims priority to U.S. provisional patent application No. 62/242,693, filed on Oct. 16, 2015. The entire contents of each of the above documents is incorporated herein by reference.BACKGROUND OF THE INVENTION Field of the Invention
This invention relates to marine seismology and more particularly relates to the deployment, retrieval, operation, and design of seismic autonomous underwater vehicles.Description of the Related Art
Marine seismic data acquisition and processing generates a profile (image) of a geophysical structure under the seafloor. Reflection seismology is a method of geophysical exploration to determine the properties of the Earth's subsurface, which is especially helpful in determining an accurate location of oil and gas reservoirs or any targeted features. Marine reflection seismology is based on using a controlled source of energy (typically acoustic energy) that sends the energy through a body of water and subsurface geologic formations. The transmitted acoustic energy propagates downwardly through the subsurface as acoustic waves, also referred to as seismic waves or signals. By measuring the time it takes for the reflections or refractions to come back to seismic receivers (also known as seismic data recorders or nodes), it is possible to evaluate the depth of features causing such reflections. These features may be associated with subterranean hydrocarbon deposits or other geological structures of interest.
There are many methods to record the reflections from a seismic wave off the geological structures present in the surface beneath the seafloor. In one method, a marine vessel tows an array of seismic data recorders provided in streamers. In another method, seismic data recorders are placed directly on the ocean bottom by a variety of mechanisms, including by the use of one or more of Autonomous Underwater Vehicles (AUVs), Remotely Operated Vehicles (ROVs), by dropping or diving from a surface or subsurface vessel, or by attaching autonomous nodes to a cable that is deployed behind a marine vessel. The data recorders may be discrete, autonomous units, with no direct connection to other nodes or to the marine vessel, where data is stored and recorded.
Emerging technologies in marine seismic surveys need a fast and cost effective system for deploying and recovering seismic receivers that are configured to operate underwater. Newer technologies use AUVs that have a propulsion system and are programmed to move to desired positions and record seismic data. In general, the basic structure and operation of a seismic AUV is well known to those of ordinary skill. For example, Applicant's U.S. Pat. No. 9,090,319, incorporated herein by reference, discloses one type of autonomous underwater vehicle for marine seismic surveys.
Because a seismic survey may require hundreds if not thousands of AUVs for a particular survey, an AUV is needed that is easy to operate and relatively straightforward and cost-effective to manufacture. A need exists for an improved AUV that is more cost effective and less complex, one that is lighter and requires less power, and one that is easier to maintain and repair. An improved AUV is needed that more effectively couples to the seabed and can travel to and from a particular point on the seabed without using as much power as may be required by known seismic AUVs.SUMMARY OF THE INVENTION
Apparatuses, systems, and methods for the deployment and retrieval of a plurality of seismic autonomous underwater seismic vehicles (AUVs) on or near the seabed. In one embodiment, the AUV comprises a streamlined body coupled to a pressure vessel that contains substantially all of the AUV's electronic components. The pressure vessel may comprise a plurality of composite components (such as carbon fiber) coupled to a metallic coupler to provide a substantially cylindrical shape to the pressure vessel. The AUV body may include a plurality of buoyant wings, surfaces, or other parts of the AUV that are configured to provide lift to the AUV in a body of water during lateral movement and to compensate for an overall negative buoyancy of the AUV. The AUV may include a plurality of landing legs or fins for increased stability of the AUV during flight and during rest and increased coupling to the seabed. The AUV may include a plurality of thrusters, such as one vertical thruster located near a front portion of the AUV and two horizontal thrusters located near a middle or a rear portion of the AUV. A vertical thruster may be used to create an upwards attack angle during takeoff and to maintain depth or orientation during flight. During normal flight operations, the AUV may be configured to travel horizontally and vertically in a body of water by using only the horizontal thrusters.
In one embodiment is disclosed an AUV for recording seismic signals on the ocean bottom during a marine seismic survey, the AUV comprising: a body that is positively buoyant, a pressure vessel coupled to the buoyant body that houses a plurality of electronic components within the pressure vessel, a propulsion system configured to propel and steer the AUV while travelling underwater, and one or more seismic sensors configured to record seismic signals while the AUV is resting on the bottom of the ocean.
In another embodiment is disclosed an AUV for recording seismic signals on the seabed during a marine seismic survey, the AUV comprising a pressure vessel that houses a plurality of electronic components within the pressure vessel, wherein an exterior portion of the pressure vessel comprises carbon fiber, and one or more seismic sensors configured to record seismic signals while the AUV is resting on the bottom of the ocean.
The pressure vessel may comprise a plurality of components that may be coupled together, wherein at least one of the components is substantially non-metallic, such as being made of carbon fiber or similar component. For example, an exterior portion of the pressure vessel may comprise one or more carbon-fiber components. In one embodiment, the pressure vessel comprises a first part coupled to a second part by a metallic ring. The first and second parts may be substantially non-metallic, such as being made of carbon-fiber components. The pressure vessel may be cylindrical and comprise a first semi-spherical end coupled to a second semi-spherical end by a metallic ring connector. The metallic ring connector may couple one or more external devices (such as thrusters, altimeters, acoustic devices, etc.) to the internal components of the pressure vessel by a variety of connections, such as a pressure sealed connector, a penetrator, or corresponding flat surfaces on both the external device and the ring connector. In other embodiments, the external devices may be coupled to a separate portion of the pressure vessel, such as a connector or penetrated located in one or more of the ends (such as in a substantially middle portion of the end cap) of the carbon-fiber components.
The AUV may comprise a propulsion system with a plurality of thrusters, such as at least one horizontal thruster and at least one vertical thruster. The at least one vertical thruster may be configured to provide all vehicle pitch control for the AUV and/or provide lift-off force from the seabed for the AUV. The plurality of thrusters may comprise a motor, nozzle, and/or impeller, and in one embodiment the plurality of thrusters are rim driven thrusters. Each of the plurality of thrusters may be coupled to a braking system configured to prevent rotation of the thrusters while the AUV is on the seabed when the AUV propulsion system is powered off.
The AUV may comprise one or more fins or legs coupled to the buoyant body and/or pressure vessel for seabed coupling purposes. In other embodiments, a plurality of legs may comprise a landing frame that couples the buoyant body to the pressure vessel and the AUV to the seabed for increased coupling effects for seismic recordings. The buoyant body may have a plurality of different shapes. In one embodiment, the body has a shape that provides lift to the AUV during horizontal movement of the AUV. While the buoyant body is positively buoyant, overall the AUV may be negatively buoyant in a body of water. The AUV may include an altimeter, which may be partially or entirely located within the pressure vessel or external to the pressure vessel. In one embodiment, the altimeter is located entirely within the pressure vessel, such as being located on an internal side of a carbon-fiber component of the pressure vessel housing.
In one embodiment is disclosed an integrated seismic and AUV control system that is configured to control a seismic payload and the propulsion system. The seismic payload may comprise one or more seismic sensors (such as three geophones and one hydrophone). In one embodiment, the integrated control system comprises a digital autonomous recorder (DAR) configured to control the propulsion system. The DAR may be coupled to an acoustic guidance system located on the AUV.
Also disclosed is a method for performing a marine seismic survey by the use of an AUV. For example, the method may include deploying an AUV to the bottom of the ocean, recording seismic signals on the seabed with one or more seismic sensors located on the AUV, lifting off the AUV from the seabed, and positioning the AUV from a seabed position to a target location in the sea or near the surface of a body of water. The lifting step may comprise activating at least one vertical thruster on the AUV and lifting a first end of the AUV off of the seabed solely by using the at least one vertical thruster. The positioning step may comprise changing a vertical position of the AUV by using the at least one horizontal thruster. In some embodiments, vertical travel in a body of water does not require the use of the vertical thruster. Instead, varying the speed of the AUV by the horizontal thruster controls the lift of the AUV by the buoyant body, thereby controlling the vertical position of the AUV.
The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.
Various features and advantageous details are explained more fully with reference to the nonlimiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well known starting materials, processing techniques, components, and equipment are omitted so as not to unnecessarily obscure the invention in detail. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure. The following detailed description does not limit the invention.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.Autonomous Underwater Vehicles and Components Thereof
In one or more embodiments, an autonomous underwater vehicle (AUV) is used to record seismic signals on or near the seabed. A seismic AUV in the following description is considered to encompass an autonomous self-propelled underwater node that has one or more sensors capable of detecting seismic waves in a marine environment. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of an AUV with seismic sensors for recording seismic waves. In general, the structure and operation of a seismic AUV is well known to those of ordinary skill. For example, Applicant's U.S. Pat. No. 9,090,319, incorporated herein by reference, discloses one type of autonomous underwater vehicle for marine seismic surveys.
The AUV may also include an inertial navigation system (INS) 118 configured to guide the AUV to a desired location. An inertial navigation system may include a module containing accelerometers, gyroscopes, magnetometers, or other motion-sensing devices. The INS may initially be provided with the current position and velocity of the AUV from another source, for example, a human operator, a GPS satellite receiver, a deployed subsea station, a deployed ROV, another AUV, from the vessel, etc., and thereafter, the INS computes its own updated position and velocity by integrating (and optionally filtrating) information received from its motion sensors. One advantage of an INS is that it requires no external references in order to determine its position, orientation or velocity once it has been initialized. However, the INS may still require regular or periodic updates from an external reference to update the AUV's position to decrease the positioning error of the AUV, particularly after long periods of time subsea. As noted above, alternative systems may be used, as, for example, acoustic positioning. An optional acoustic Doppler Velocity Log (DVL) (not shown) can also be employed as part of the AUV, which provides bottom-tracking capabilities for the AUV. Sound waves bouncing off the seabed can be used to determine the velocity vector of the AUV, and combined with a position fix, compass heading, and data from various sensors on the AUV, the position of the AUV can be determined. This assists in the navigation of the AUV, provides confirmation of its position relative to the seabed, and increases the accuracy of the AUV position in the body of water.
Besides or instead of INS 118, the AUV may include compass 120 and other sensors 122 as, for example, an altimeter for measuring its altitude, a pressure gauge, an interrogator module, etc. The AUV 100 may optionally include an obstacle avoidance system 124 and a communication device 126 (e.g., Wi-Fi or other wireless interface, such as a device that uses an acoustic link) or other data transfer device capable of wirelessly transferring seismic data and/or control status data. One or more of these elements may be linked to processor 108. The AUV further includes antenna 128 (which may be flush with or protrude from the AUV's body) and corresponding acoustic system 130 for subsea communications, such as communicating with a deployed ROV (or other underwater station), another AUV, or a surface vessel or station. For surface communications (e.g., while the AUV is on a ship), one or more of antenna 128 and communication device 126 may be used to transfer data to and from the AUV. Stabilizing fins and/or wings 132 for guiding the AUV to the desired position may be used with propulsion system for steering the AUV. However, in one embodiment, the AUV has no fins or wings. The AUV may include buoyancy system 134 for controlling the AUV's depth and keeping the AUV steady after landing.
Acoustic system 130 may be an Ultra-Short Baseline (USBL) system, also sometimes known as Super Short Base Line (SSBL). This system uses a method of underwater acoustic positioning. A complete USBL system includes a transceiver or acoustic positioning system mounted on a pole under a vessel or ROV (such as Hi-PAP or μPAP, commercially available by Kongsberg) and a transponder on the AUV. In general, a hydro-acoustic positioning system consists of both a transmitter and a receiver, and any Hi-PAP or μPAP or transponder system acts as both a transmitter and a receiver. An acoustic positioning system uses any combination of communications principles for measurements and calculations, such as SSBL. In one embodiment, the acoustic positioning system transceiver comprises a spherical transducer with hundreds of individual transducer elements. A signal (pulse) is sent from the transducer (such as a Hi-PAP or μPAP head on the surface vessel), and is aimed towards the seabed transponder located on the AUV. This pulse activates the transponder on the AUV, which responds to the vessel transducer after a short time delay. The transducer detects this return pulse and, with corresponding electronics, calculates an accurate position of the transponder (AUV) relative to the vessel based on the ranges and bearing measured by the transceiver. In one embodiment, to calculate a subsea position, the USBL system measures the horizontal and vertical angles together with the range to the transponder (located in the AUV) to calculate a 3D position projection of the AUV relative to a separate station, cage, ROV, or vessel. An error in the angle measurement causes the position error to be a function of the range to the transponder, so an USBL system has an accuracy error increasing with the range. Alternatively, a Short Base Line (SBL) system, an inverted short baseline (iSBL) system, or an inverted USBL (iUSBL) system may be used, the technology of which is known in the art. For example, in an iUSBL system, the transceiver is mounted on or inside the AUV while the transponder/responder is mounted on a separate vessel/station and the AUV has knowledge of its individual position rather than relying on such position from a surface vessel (as is the case in a typical USBL system). In another embodiment, a long baseline (LBL) acoustic positioning system may be used. In a LBL system, reference beacons or transponders are mounted on the seabed around a perimeter of a work site as reference points for navigation. The LBL system may use an USBL system to obtain precise locations of these seabed reference points. Thus, in one embodiment, the reference beacon may comprise both an USBL transponder and a LBL transceiver. The LBL system results in very high positioning accuracy and position stability that is independent of water depth, and each AUV can have its position further determined by the LBL system. The acoustic positioning system may also use an acoustic protocol that utilizes wideband Direct Sequence Spread Spectrum (DSSS) signals, which provides for a greater communications range in the water.
With regard to the AUV's internal configuration, the AUV includes a CPU that is connected to an inertial navigation system (INS) (or compass or altitude sensor and acoustic transmitter for receiving acoustic guidance from the mother vessel), a wireless interface, a pressure gauge, and an acoustic transponder. The INS is advantageous when the AUV's trajectory has been changed, for example, because of an encounter with an unexpected object (e.g., fish, debris, etc.), because the INS is capable of taking the AUV to the desired final position as it encounters currents, wave motion, etc. Also, the INS may have high precision. For example, an INS may be accurate up to 0.1% of the travelled distance, and a USBL system may be accurate up to 0.06% of the slant range. Thus, it is expected that for a target having a depth of 1000 m, the INS and/or the acoustic guidance is capable of steering the AUV within +/−1 m of the desired target location. The INS may be also configured to receive data from a surface vessel and/or a deployed ROV to increase its accuracy. The AUV may include multiple CPUs. For example, a second CPU may be configured to control one or more attitude actuators and a propulsion system. One or more batteries may be located in the AUV. A seismic payload is located inside the AUV for recording the seismic signals. As another embodiment, an obstacle avoidance system may be included in the AUV, which is generally configured to detect an object in the path of the AUV and divert the AUV from its original route to avoid contact with the object. In one example, the obstacle avoidance system includes a forward-looking sonar. The AUV includes any necessary control circuitry and software for associated components. In one embodiment, the AUV may have various operational modes, such as wakeup, sleep, maintenance, and travel modes.
Those skilled in the art would appreciate that more or less modules may be added to or removed from the AUV. For example, the AUV may include variable buoyancy functionality, such as the ability to release a degradable weight on the bottom of the ocean after seismic recording to assist in the rise or surfacing of the AUV to a recovery spot (such as on or near the ocean surface). In other embodiments, the AUV may include one or more buoyancy or ballast tanks that may be flooded with air or water to assist in the vertical navigation of the AUV, such as described in more detail in Applicant's U.S. Patent Publication No. 2015/0336645, incorporated herein by reference. In another embodiment, the AUV may include a suction skirt that allows water to be pumped out of a compartment under the AUV after it has landed to create a suction effect towards the seabed. In still other embodiments, the AUV may include one or more seabed coupling mechanisms or self-burying functionality, such as the ability to rock or twist into the ocean by specific movements of the AUV or the use of a plurality of base water outlets on the bottom of the AUV to fluidize the seabed sediment, as described in more detail in Applicant's U.S. Pat. Nos. 9,381,986 and 9,457,879, incorporated herein by reference.Improved Autonomous Underwater Vehicle
The disclosed AUV embodiments provides numerous benefits over previously disclosed seismic AUVs, including better seabed seismic coupling, enhanced subsea maneuverability, control, and propulsion, and increased acoustic capabilities. The disclosed AUV uses less power than conventional seismic AUVs, and is also more cost effective, lighter, less complex more reliable, and easier to handle and repair than existing seismic AUVs.
In one embodiment, body 201 is comprised of a positively buoyant flotation material that partially offsets the remaining negative buoyant components of the AUV, thereby making the overall buoyancy of the AUV slightly negative. In other words, while the AUV main body is positively buoyant, the remaining components (e.g., the pressure vessel, landing fins and other attached components) are negatively buoyant such that the overall buoyancy is slightly negative. The flotation material may be made of a material with a plurality of air cells or pockets. In one embodiment, the floatation material is made out of microsphere syntactic foam, which is comprised of resin and hollow glass microspheres. The syntactic foam is available in a range of densities and is formulated to meet depth and buoyancy requirements down to 10,000 meters. The syntactic foam may be fully casted and/or machined to the specific configurations of the AUV body shape and thereafter coated with one or more layers of protective skins for improved impact resistance, reduced water absorption, and reduced drag in the water. The protective coating may also have anti-fouling properties to prevent or slow down any undesired marine biological growth. In other embodiments, the floatation material may also be casted in a pre-made polyethylene (PE) coated or similar plastic coating rotation mold. In one embodiment, the buoyant body of the AUV is cast as a single foam structure, such that the main body and the contoured wings form a monolithic and/or single structure. In other embodiments, the foam body may comprise separate portions that are integrated together, such that the buoyant main body may be removably attached to one or more buoyant wing sections. The configuration and design of the buoyant wings creates increased lift, such that only horizontal thrust is needed during normal AUV flight within a body of water. In other words, once the AUV lifts off the seabed or other resting place and has reached its cruising speed, the lift created from the wing shape of the foam is great enough to balance out the negative buoyancy of the vehicle. Thus, during normal flight operations, the vertical thruster is used only for depth control and to maintain level flight. While this design may increase the overall complexity of the AUV shape, it decreases the overall power needed to move the AUV in a body of water and the number of thrusters required, thereby decreasing the size (and weight), complexity, and cost of the necessary power supply, and thereby decreases the overall cost of the AUV. Various embodiments of buoyant body 201 are possible, as described below in more detail in relation to
In one embodiment, pressure vessel 211 holds substantially all of the electronic components of the AUV, including any seismic sensors, batteries, processors, data recording units, memory units, motors, etc. In one embodiment, the hydrophone is mounted directly into an exterior portion of the pressure vessel for exposure of the hydrophone to the water. In one embodiment, the hydrophone is casted or glued to the inside of the pressure vessel hull or to the titanium center hub (see
One problem with conventional seismic AUVs and sensors is the use of external cables, wires, and/or connectors outside of any pressurized vessel. Each electrical component (e.g., motor, sensor, battery, antenna, propeller, etc.) requires an electrical connection. Harsh conditions (such as extreme pressures and temperatures existing at or near the seabed, along with corrosion issues caused by seawater) cause many problems with electrical connections and components exposed to the sea, often times leading them to fail and/or have a shortened life. While it is desired to reduce the number of electrical components and connections outside of a single pressure vessel, existing designs of seismic AUVs have not been able to solve this problem. Thus, in one embodiment, the disclosed AUV eliminates all or substantially all of the electrical cables and connectors outside of the pressure vessel by using a central electrical hub (see
In one embodiment, pressure vessel 211 is substantially cylindrical and may be comprised of a single cylindrical housing with two hemispherical endcaps, such that when integrated together the pressure vessel is capable of withstanding pressure depths of 3000 meters or more beneath the water surface. In contrast to prior art AUV designs, this cylindrical design provides a cost effective configuration for the pressure housing; however, such a uniform shape to the pressure vessel creates additional problems, such as electrically connecting many of the operational components that are needed for an AUV (such as propellers, sensors, acoustic devices, etc.). In one embodiment, the pressure vessel may be coupled to the lower side of the buoyant body, as shown in
In one embodiment, the AUV comprises a plurality of landing skids and/or fins. Skids and/or fins may protrude from the pressure vessel and/or be coupled to the pressure vessel, and may be any variety of material compositions, including plastic and/or metal. In one embodiment, a first fin is arranged at approximately 90 degrees from a second fin. The fins may be arranged in numerous configurations, including from approximately 30 degrees or less to approximately 180 degrees in relation to each other, and preferably between 60 degrees to 120 degrees. The fins provide stabilization to the AUV during movement of the AUV in the water and while resting on the seabed floor, and thereby also function as stands. The landing fins also produce lift when the AUV is moving forward with at least a minimal upwards attack angle. Further, the fins provide increased contact to the seabed and provide increased seabed coupling for the seismic sensors. In one embodiment, each fin comprises two protrusions or ends at the corners for increased penetration into and coupling with the seabed, such that the AUV is configured to couple to the seabed at four separate points (two points on each landing fin). This stabilizes the vehicle on the bottom, especially in uneven bottom surface. In one embodiment, the landing fins and pressure vessel are arranged such that in soft seabed situations the pressure vessel is configured to slightly sink into the seabed sediment for increased seabed coupling to the AUV sensors. In these cases the bottom of the pressure vessel may be resting on the seabed.
In one embodiment, the propulsion system of the AUV may comprise a plurality of thrusters, and in one embodiment may include one vertical thruster 233 located in a front portion of the AUV and two horizontal thrusters 231a, 231b located substantially in the middle portion of the AUV near the center of buoyancy (COB). In some embodiments, the horizontal thrusters are located substantially in the rear portion of the body as viewed longitudinally. In one embodiment, each horizontal thruster is located in a circular opening or recess 203a, 203b underneath the contoured wings of body 201. The efficient design of the AUV, as well as the center of buoyancy and center of gravity (COG), provides an inherent stability of the AUV in which a minimal number (such as three) thrusters is needed for stable flight within a body of water. In one embodiment, the AUV is configured to provide a high separation between the COB to the COG, as increasing the COB to COG distance will increase the stability of the AUV in a body of water thereby requiring a less complex control system.
The thrusters may be propellers, impellers, and/or jet nozzles. Each thruster may be coupled to a motor or water pump that is powered by a power supply. Each thruster may be selectively and independently operated and controlled, such that for any particular movement and/or operation, one, two, or three of the thrusters may be simultaneously operated. The thrusters are configured to rotate in opposing directions as appropriate. For example, vertical thruster 233 may rotate in a first direction to provide positive vertical lift (e.g., move the nose of the AUV up) and may be configured to rotate in a second direction to provide negative vertical lift (e.g., move the nose of the AUV down). Similarly horizontal thrusters 231a, 231b may be configured to rotate in a first direction to provide forward movement and in a second direction to provide backwards movement. Each of the horizontal thrusters may be configured to operate in counter-rotating propeller mode (e.g., rotate in separate directions and still provide the same lateral movement) for increased AUV flight stability, such that the angular momentum and/or torque developed by the propellers is balanced and/or cancelled out. In other embodiments, a plurality of vertical thrusters may be used, such that a first thruster is located substantially in the front section of the AUV and a second thruster is located substantially in the rear section of the AUV. In still other embodiments, each buoyant wing of the AUV may be coupled to a vertical thruster, such that the AUV has four vertical thrusters (one at the front, one at the back, and one on each wing). In one embodiment, vertical thruster 233 is mounted in an opening in the buoyant body, and each horizontal thruster 231a, 231b is mounted under a rear portion of a wing.
In still other embodiments, each thruster is configurable between a first position to provide substantially lateral movement and a second position to provide substantially vertical movement, such that each thruster may act as both a vertical and horizontal thruster depending on the angle/configuration of the thruster. In one embodiment, the thrusters are any commercially available thrusters configured to create a certain amount of thrust in a given direction in a body of water. In other embodiments, the thrusters are specially designed thrusters for optimal weight, design, and speed, size, and thrust considerations. In one embodiment the thruster uses a two-blade propeller, but in other embodiments, three, four or more bladed propellers may be used. In one embodiment the motor driving the thruster is a direct drive DC brushless motors for low noise in noise sensitive applications. In one embodiment the AUV uses rim driven thrusters. Rim driven thrusters significantly prevent the risk of a rope, cable, or similar deployment line from being trapped in the propeller of the thruster. In a rim driven thruster, the center of the propeller is “open” with the propellers or fins being rotated by the rim or outer periphery of thruster driving the propellers, such that a rope can pass through without catching.
Vertical thruster 233 creates a force either upwards or downwards depending on its rotation direction. In one embodiment, vertical thrust is not utilized to significantly move the AUV vertically in a body of water, but can be used for depth control and/or to maintain level flight. In other words, vertical thruster 233 is not used during normal flight mode of the AUV in a body of water. However, vertical thruster 233 is used during take off from and landing on the seabed (as more easily described in relation to
In one embodiment, the AUV is specifically designed to be heavier in seawater to allow prolonged deployment on the seabed. In other words, the AUV is not neutrally buoyant in a body of water, and to compensate for this negative weight, the AUV is configured with a vertical thruster located near the nose of the AUV (such as vertical thruster 233) and a form lift is created by the AUV body as it travels through the water at a cruising speed under power from the horizontal thrusters (such as horizontal thrusters 231a, 231b). Thus, the form lift shape (such as body 201 or body 301) allows a permanently negatively buoyant AUV in a water column to be suspended during horizontal transit without additional vertical thrusters/power. If horizontal speed is decreased, the upwards lift decreases and the negatively buoyant AUV sinks; if horizontal speed is increased, the upwards lift increases to overcome the negative buoyancy and the AUV rises. To maintain level flight, the AUV control algorithm may slightly change the vehicle pitch angle. This is in contrast to existing AUV devices, which typically have some type of buoyancy change device (water expulsion, inflatable bag, weight release, etc.) to alter the buoyancy of the AUV to move it from one position to another position (such as from the water surface to the seabed).
This alternative embodiment shown in
Shown in more detail in
Homing and docking array 341 is located on a front portion or nose of the AUV and is configured for automatic homing into a retrieval device or basket. For example, in one embodiment one or more transmitters may be located on a retrieval device or basket that transmits a tone or ping for the homing array to navigate towards. Homing array 341 may be made up of several sensors arranged in an array, and when it approaches the transmitter it can use this array to detect the transmitted signals and determine which direction the AUV needs to fly to reach the destination. The closer the AUV gets to the transmitter, the more accurate that the homing array will be able to navigate the AUV to the destination position. In one embodiment, the homing array is directly attached to the pressure vessel to eliminate external cables, while in other embodiments a cable is run from the pressure vessel to the homing array.
In one embodiment, altimeter 348 is mounted on the exterior hull of the pressure vessel, such as on the bottom or side of the pressure vessel. The altimeter measures the altitude of the vehicle over sea bottom, which is an important parameter in case of dead reckoning of the AUV. The altimeter may also assist in the landing process of the AUV, as it is an important sensor to determine the AUV's height over the seabed. In another embodiment, the altimeter may be mounted on the inside of the pressure vessel, which may be possible if the pressure vessel (or portions thereof) is made of carbon fiber or other composite material. Mounting the altimeter inside the pressure vessel tube provides many benefits, including reducing an electrical connection through the pressure vessel, which reduces the risk of failure in case of water ingress. An additional benefit is that it removes the need for the altimeter to have a full depth rating of 3000 meters (or other high depth water pressure typical on the ocean bottom), since the altimeter may now be mounted inside of the pressure tube. Thus, the resulting altimeter is less complex, less likely to fail, and is less expensive.
Various penetrators may be machined into ring connector 501 for external connections to the pressure vessel, thereby eliminating the need for external cables. For example, ring 501 may comprise one or more openings 505 to receive an external electronic device such as an acoustic transducer. Any connectors/penetrators that couple to the pressure vessel may have O-ring seals that prevent the surrounding seawater to enter into the pressure vessel. For example, in one embodiment, two horizontal thrusters (such as thrusters 231a, 231b) are configured to mount onto pressure vessel 500 such that no external cables connect the pressure vessel to the thrusters. In this embodiment, the connection between the horizontal thrusters and the pressure vessel may be made by a penetrator in the titanium ring Likewise, in some embodiments, the vertical thruster (such a thruster 233) is configured to also mount directly to the pressure vessel to avoid external cables, while in other embodiments a cable connects the vertical thruster to the pressure vessel (similar to the embodiment in
As described earlier,
In one embodiment, the geophones may be located substantially in the center of the pressure vessel such that they are located in the approximate center of gravity (COG) of the AUV. Having the location of the geophones in the center of the AUV increases the quality of the of seismic data obtained by the geophones by having consistent readings and positions of the geophones in the AUV no matter the landing position/orientation of the AUV on the seabed. Also, the effect of any rotation of the AUV around its COG will have as low as possible impact on the fidelity of the geophone signals when the geophone array is mounted close to COG. In one embodiment, the configuration of the components changes the COG and/or center of buoyancy (COB) for the AUV. For example, the batteries may be placed at an upper portion of the pressure vessel for a center of gravity closer to the center of the AUV, whereas the batteries may be placed at the bottom of the pressure vessel if a lower center of gravity is desired to maximize overall AUV stability and to maximize COG and COB separation. The COB and COG of the AUV may be varied based upon the coupling of the pressure vessel to the buoyant body, as well as the location of electronic components within the pressure vessel itself. In one embodiment, the greater the distance between the COG and the COB, the more stable the AUV will be during flight, thereby reducing the complexity of the control algorithm for AUV flight. In other embodiments, the AUV may also have variable buoyancy so that the AUV changes it buoyancy when it has landed to make the AUV heavier for better coupling. Then before take off, the AUV may make the buoyancy lighter for easier lift off and because it is lighter, power is saved.Operation
In other embodiments (particularly if the batteries of an AUV is depleted or the AUV has operational errors), to retrieve the AUV after deployment, a flat circular area on the top part of the AUV body is provided so that a suction device mounted to the end of the ROV's manipulator arm may be used to pick up and move the AUV. In another embodiment, the area on top of the AUV can be slightly curved and the suction device made to fit with the body curve or shape of the AUV. In one embodiment, the suction tool for the ROV may also have a guiding frame or feature to ease the placement of the suction on top of the AUV, which makes it easier for an ROV operator to correctly hit the top AUV surface with a suction tool. In other embodiments, the AUV may comprise a lock or latch for coupling to an ROV instead of the use of a suction device, such that the ROV may move the AUV from a first location to a second location subsea without using a suction device (which is common for ROV placement of marine seismic nodes). In other embodiments, the AUV may comprise a guide latching mechanism to dock the AUV to an ROV or other subsea station, which may operate similarly to an ROV docking system, such that the AUV may have a female receptacle and the ROV (or other device) may have a corresponding male probe (or vice versa). In one embodiment, the AUV may fly directly into a basket guided by a homing array.
The versatility of the disclosed seismic AUV allows it to be utilized in a wide variety of subsea deployment and retrieval operations. For example, the AUV is configured to move to a particular subsea location based on a transducer on the AUV communicating with another subsea device or surface vessel. The AUV can be dropped and/or deployed from a surface vessel and travel near or to the seabed at a predetermined location based on predetermined positions. After the desired number of seismic surveys has been performed with the AUV on the ocean bottom, the AUV may travel back up to the surface vessel for recovery. However, this method requires a larger power supply on the AUVs, which increases the weight, cost, and size of the AUV. As another example, the AUV may be deployed with an ROV, skid, cage, or subsea station from a surface vessel and be positioned on or near the seabed, similar to the method described in Applicant's U.S. Patent Publication No. 2016/0121983, incorporated herein by reference. The AUVs may be instructed to deploy from the ROV, skid, cage, or subsea station to a predetermined location on or near the seabed for seismic data recordings. In other embodiments, instead of instructing the AUV to fly to a predetermined position, the AUV may receive range and bearing to the target updates at regular intervals. The AUV may then calculate the necessary action to reach the target destination. In yet another embodiment, the AUV is directly guided from the onboard acoustic positioning system. In this mode, the AUV may receive instructions of heading, speed, and pitch in its route and/or path to the target destination. In some embodiments, an ROV or subsea station may be coupled to a cage with the AUVs and transfer those AUVs to the ROV or subsea station for deployment Likewise, for recovery, the AUVs may travel to the ROV, skid, cage, or subsea station after the seismic survey is completed. The ROV may or may not facilitate recovery of the AUV into the intended recovery station. Likewise, in some situations, a robotic manipulator arm of an ROV may be used to grab, place, or position a plurality of AUVs from one subsea location to another subsea location. For example, a plurality of AUVs may be commanded to travel to a particular subsea location on the seabed, and the ROV may then travel to that subsea location and grab each of the AUVs and place them in a skid of the ROV or a subsea basket or station. In some embodiments, an ROV is used to recover the AUVs only and is not used to deploy the AUVs. In some embodiments, an ROV is not used at all and an intelligent subsea station configured with an acoustic system is used to facilitate deployment and retrieval of the AUVs. In general, the particular deployment and recovery method of the AUVs is not limited by this invention.
In operation, and as one example, once on or near the seabed (by any number of mechanisms), a plurality of AUVs may self-navigate to their predetermined deployment locations on the seabed based on position updates that are provided by a SSBL/USBL navigation system that is mounted on a surface vessel, a ROV, or subsea station (such as a cage). These positions may be provided in geographic coordinates (e.g., the WGS-84 reference system). The position information may be sent to each AUV via an acoustic communication link, such as a Cnode transducer on each AUV. The data communication packet also stimulates a reply ping from the AUV that is then used to establish its position by the SSBL/USBL system. In a different navigation method, instead of receiving or determining its position, the AUV may be given the range and bearing to its target on the seabed. In yet another navigation method, the AUV may not be given a position or range/bearing, but rather commands of which heading, speed, pitch, and altitude to fly. There are many possible ways for the AUV to navigate to an intended destination point, and the methods mentioned here is not meant to limit the disclosed AUV to any of those specific methods mentioned herein.
In one embodiment, one or more ROVs are deployed from a dynamically positioned surface vessel, along with cages or baskets that contain a plurality of AUVs. In one embodiment, each cage carries a plurality of trays with a plurality of AUVs on each cage. The ROV removes trays from these baskets, and may carry a plurality of AUVs (such as 6, 9, 12, 15, or more) on the beginning of each deployment cycle. The ROV may move to a central line in a plotted seabed grid; as the ROV moves along the line, each AUV stays in wait mode until it is updated via an acoustic command with a landing position (or range and bearing updates at regular intervals) and a command to deploy. The AUV then enters transit mode and maneuvers out of the tray housed in the ROV. Each AUV then transits to its assigned set down location on the seabed, and as each AUV nears its assigned landing position, it switches to landing mode, maneuvers to the set down position, and establishes that its resting place is within the stipulated set-down position accuracy by averaging the position updates it receives from the ROV. Alternatively, if the AUV is receiving range and bearing updates instead of operating with an absolute position, the AUV may send a status update to the onboard system when it has landed on the seabed. The onboard acoustic system may then determine the landing position via the acoustic system. The AUV then sends a confirmation message with its location to the ROV or other subsea positioning station/device. The AUV then shuts down the AUV control functions (including switching the transponder to hibernate mode), leaving only the seismic payload electronics package powered on. In other embodiments, the cNode transducer is automatically shut down or hibernated if it does not receive any pings or interrogations for a set period of time from a separate acoustic system. This procedure is repeated until the desired number of AUVs is positioned on the seabed. At this stage, the source vessel will travel along the predetermined source lines and fire the seismic source at the predetermined positions, while the AUVs acquire the seismic data.
After the seismic survey is completed, a coded wakeup signal may be sent to one or more of the AUVs to power on the AUV control functions. When taking off from the seafloor, the vertical thruster may be used to pitch the AUV's nose up off the seafloor, as discussed in relation to
In general, conventional seismic AUVs typically “added on” a seismic electronics package to an existing guidance and AUV control system of a traditional (e.g., non-seismic) AUV. Each system (e.g., an AUV control system and a seismic payload control system) would have its own battery pack, as well as separate electronic components communicating between the systems. This typical electronics system is inefficient and not integrated, making the overall seismic AUV more heavy, complicated, likely to fail, and expensive.
As shown in
Seismic payload system 821 comprises digital autonomous recorder (DAR) 823 and seismic payload/sensor package 825 that may consist of up to 8 channels. In one embodiment, seismic payload 825 may comprise three geophones and one hydrophone, providing a 4-component (4C) setup. The disclosed embodiment allows 4 additional components for additional sensors or other components. DAR 823 is interfaced to both AUV control system 801 and to cNode acoustic system 811. DAR 823 is able to record continuous data on the seabed for long time periods, such as months. DAR 823 is also configured to interface with and control AUV control system 801. In one embodiment, DAR 823 is the electronics component that sends AUV control system 801 into a hibernation mode and also to wake the AUV from the hibernation mode after seismic recording is finished. In addition to the seismic channels, DAR 823 may also comprise tilt meter (not shown) a that is configured to measure tilt angles in X, Y, and Z directions for the AUV. The tilt angles are also recorded by the DAR.
In one embodiment, acoustic guidance system or module 811 consists of a cNode transponder with transducer 813, transformer 815, and associated OEM electronics board 817. Acoustic guidance system 811 is coupled to and/or interfaces with DAR 823, which directs the communications from guidance system 811 to either itself (e.g., DAR 823) or AUV control system 801 depending on the type and destination of the command. Typically, during a flight of the AUV, cNode guidance system 811 will send position or range/bearing updates to the DAR, which forwards these to the AUV control, so that the AUV control system 801 can use the regular positional updates to determine how the thrusters shall be controlled to reach the target destination.
In some embodiments to conserve power, the AUV guidance system and propulsion system is powered and/or switched off during seismic recordings. During such periods of seismic data recording, there may be bio-fouling operations occurring, where the AUV electronics control briefly wakes up for a short period of time, turns the propeller to prevent bio-fouling and then the AUV electronics control system powers down. By having the AUV control system electronics separate from the seismic recorder electronics (as shown in
As shown in
Compared to prior DARs, DAR 903 is configured with a computer system that can also handle the computing needed for AUV navigation control and thruster control. Compared to prior DARs, DAR 903 is configured with motor drives for any propulsion system, such as a plurality of thrusters, shown as blocks 911, 913, and 915, so that DAR 903 can direct control the thrusters. Similar, DAR 903 is configured with serial ports to interface with various other external devices, such as altimeter 917, IMU sensor 919, a homing array, etc. DAR 903 may be coupled to an interconnection or Ethernet board 921, which is coupled to acoustic guidance system 931 and is configured to communicate with an external device for data and/or power transfer. Any internal Ethernet switch existing in the prior art between the different components of the AUV is removed, as only the DAR needs to be connected to Ethernet/data connections. The DAR is coupled to and/or comprises a battery pack and battery control system (BMS) 923. The DAR may have a direct connecting for charging the batteries. Similar to existing
The embodiment disclosed in
However, using a common power source (as shown in
All of the methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the apparatus and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. In addition, modifications may be made to the disclosed apparatus and components may be eliminated or substituted for the components described herein where the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the invention.
Many other variations in the configurations of a node and the wireless systems on the node and/or vessel are within the scope of the invention. For example, the AUV may be of any configuration, and may be designed to couple to the seabed or merely near the seabed. The pressure vessel may or may not be comprised of carbon fiber components or generally be in the shape of a cylindrical tube. The DAR may or may not be an integrated computer that combines separate AUV control functionality into the DAR. It is emphasized that the foregoing embodiments are only examples of the very many different structural and material configurations that are possible within the scope of the present invention.
Although the invention(s) is/are described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present invention(s), as presently set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention(s). Any benefits, advantages, or solutions to problems that are described herein with regard to specific embodiments are not intended to be construed as a critical, required, or essential feature or element of any or all the claims.
Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The terms “coupled” or “operably coupled” are defined as connected, although not necessarily directly, and not necessarily mechanically. The terms “a” and “an” are defined as one or more unless stated otherwise. The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a system, device, or apparatus that “comprises,” “has,” “includes” or “contains” one or more elements possesses those one or more elements but is not limited to possessing only those one or more elements. Similarly, a method or process that “comprises,” “has,” “includes” or “contains” one or more operations possesses those one or more operations but is not limited to possessing only those one or more operations.
1. An autonomous underwater vehicle (AUV) for recording seismic signals on the ocean bottom during a marine seismic survey, the AUV comprising:
- a pressure vessel coupled to a buoyant body, wherein the pressure vessel houses a plurality of electronic components;
- a propulsion system configured to control the AUV while travelling underwater;
- a power supply;
- an accelerometer; and
- one or more seismic sensors.
2. The AUV of claim 1, wherein the accelerometer and the one or more seismic sensors are located within the pressure vessel.
3. The AUV of claim 1, wherein the pressure vessel is located exterior to the buoyant body.
4. The AUV of claim 1, wherein the pressure vessel is substantially cylindrical.
5. The AUV of claim 1, further comprising a plurality of wings, wherein the accelerometer or the one or more seismic sensors is mechanically coupled to the plurality of wings for increased seabed coupling.
6. An autonomous underwater vehicle (AUV) for recording seismic signals on the ocean bottom during a marine seismic survey, the AUV comprising:
- a pressure vessel that houses a plurality of electronic components, wherein the plurality of electronic components comprises one or more seismic sensors;
- a propulsion system;
- a plurality of upper wings; and
- a plurality of lower wings.
7. The AUV of claim 6, further comprising a buoyant body coupled to the pressure vessel.
8. The AUV of claim 6, wherein the plurality of upper wings is buoyant.
9. The AUV of claim 6, wherein the plurality of upper wings is configured to provide lift.
10. The AUV of claim 6, wherein the plurality of lower wings is coupled to the pressure vessel.
11. The AUV of claim 6, wherein the plurality of lower wings is configured to couple to the seabed.
12. The AUV of claim 6, wherein the plurality of lower wings comprises stabilizing wings.
13. The AUV of claim 6, wherein the plurality of lower wings comprises landing fins.
14. The AUV of claim 6, wherein the propulsion system comprises a plurality of thrusters, wherein each of the plurality of thrusters is located on a side of the AUV between the plurality of upper wings and the plurality of lower wings.
15. An autonomous underwater vehicle (AUV) for recording seismic signals on the ocean bottom during a marine seismic survey, the AUV comprising:
- a pressure vessel coupled to a buoyant body, wherein the pressure vessel houses a plurality of electronic components, wherein the pressure vessel is negatively buoyant, wherein the buoyant body comprises a foam body that is positively buoyant;
- a propulsion system configured to propel and steer the AUV while travelling underwater; and
- one or more seismic sensors.
16. The AUV of claim 15, wherein the pressure vessel is located substantially beneath the buoyant body.
17. The AUV of claim 15, wherein the buoyant body has a contoured shape that is configured to provide lift to the AUV.
18. The AUV of claim 15, further comprising a plurality of contoured wings that is configured to provide lift to the AUV.
19. The AUV of claim 15, wherein the AUV comprises a negative buoyancy, wherein the AUV is configured to provide lift during lateral subsea movement to overcome the negative buoyancy of the AUV.
20. The AUV of claim 15, wherein the propulsion system comprises a single vertical thruster that is configured to provide all vehicle pitch control for the AUV.
Filed: May 7, 2019
Publication Date: Aug 22, 2019
Applicant: Seabed Geosolutions B.V. (Leidschendam)
Inventors: Geir Valsvik (Laksevag), Arne Henning Rokkan (Olsvik), Johan Fredrik Næs (Trondheim), Matthew E. Silvia (Pocasset, MA), Christopher J. von Alt (Pocasset, MA)
Application Number: 16/405,418