Method of wireless underwater communication

Abstract

The invention relates to a method of wireless underwater communication comprising: navigating a first unit in a body of water; causing a second unit to acquire at least one image of the first unit using a camera on the second unit; based on the acquired image, navigating the second unit in the body of water so as to maintain the second unit within wireless optical communication range relative to the first unit; and exchanging data between the first unit and the second unit by wireless optical communication.

Description

[0001] METHOD OF WIRELESS UNDERWATER COMMUNICATION

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a method of wireless underwater communication, more specifically a method of dynamic wireless underwater communication between underwater vehicles.

[0004] TECHNICAL BACKGROUND

[0005] Remotely controlled unmanned vehicles are widely used for a variety of operations of underwater facilities or subsea structures. They allow the operations to be performed remotely, even autonomously without human intervention. Such unmanned vehicles generally require tethered communication by means of an umbilical connected to a surface, or subsea component. Some unmanned vehicles are autonomous or untethered, but still require wireless communication to enable operations to be monitored or directed by operators.

[0006] There are several limitations in wireless underwater communication. Radio waves are significantly attenuated in water and do not work underwater. Acoustic communication allows underwater communication over long ranges, but has very low data rates. Optical communication allows high-speed and high-capacity communication, but it has a shorter communication range than acoustic communication, and is susceptible to noise created by water turbidity, ambient light and solar light. Wireless communication by means of acoustic, or optical communication typically requires several modems to be installed in the area of operations, requiring both electrical power and supporting communication infrastructure to enable operations. In areas where there is insufficient electrical or communication infrastructure to support the introduction of autonomous or untethered vehicles, a dynamic system is required.

[0007] Therefore, there is a need for providing an improved method of wireless underwater communication.

[0008] SUMMARY OF THE INVENTION There is provided a method of wireless underwater communication comprising:

[0009] - navigating a first unit in a body of water;

[0010] - causing a second unit to acquire at least one image of the first unit using a camera on the second unit;

[0011] - based on the acquired image, navigating the second unit in the body of water so as to maintain the second unit within wireless optical communication range relative to the first unit; and

[0012] - exchanging data between the first unit and the second unit by wireless optical communication.

[0013] According to some embodiments, operation of the first unit is controlled by way of the exchange of data by wireless optical communication with the second unit.

[0014] According to some embodiments, each of the first unit and the second unit comprises at least one optical emitter and at least one optical receiver.

[0015] According to some embodiments, the first unit is configured to perform inspection of a subsea structure.

[0016] According to some embodiments, the first unit is a remotely operated vehicle (ROV).

[0017] According to some embodiments, the second unit is an autonomous underwater vehicle (AUV).

[0018] According to some embodiments, the first unit is untethered.

[0019] According to some embodiments, the method comprises exchanging data between the second unit and a surface vessel, preferably via an umbilical between the second unit and the surface vessel, more preferably via an optical fibre in the umbilical.

[0020] According to some embodiments, based on the acquired image, a distance and orientation of the second unit relative to the first unit are determined, and navigating the second unit is adjusted as a function of the determined distance and orientation.

[0021] According to some embodiments, the first unit has a pattern on its surface, the acquired images comprise a captured pattern and the distance and orientation of the second unit relative to the first unit are determined depending on the captured pattern.

[0022] According to some embodiments, the second unit comprises a lamp which illuminates the first unit so as to allow acquiring images.

[0023] According to some embodiments, maintaining the second unit within wireless optical communication range relative to the first unit comprises maintaining the second unit within a predetermined range of distance to the first unit and maintaining an orientation of the second unit relative to the first unit within a predetermined orientation range.

[0024] According to some embodiments, the method comprises causing the second unit to navigate towards the first unit based on acoustic communication between the first unit and the second unit, prior to causing the second unit to acquire at least one image of the first unit.

[0025] According to some embodiments, the method comprises causing the second unit to navigate towards the first unit based on optical communication between the first unit and the second unit, prior to causing the second unit to acquire at least one image of the first unit.

[0026] According to some embodiments, the wireless optical communication is carried out using bidirectional laser signals between the first unit and the second unit.

[0027] The present disclosure enables efficient and dynamic wireless underwater communication. In the body of water, the second unit acquires at least one image of the first unit using its camera. Based on this visual localization, “visual lock” may be achieved between the first unit and the second unit. Once such “visual lock” is achieved, the second unit can be navigated so that it stays within the optical communication range relative to the first unit. Alignment and positioning are on one-on-one level between the first and second units, so that a large number of receivers and emitters is not required. There is no need to install communication facilities on the seabed. In contrast to communication relying on modems installed on fixed areas, the navigation of the second unit relative to the first unit is dynamic, following a flight path of the first unit in an adapted manner. Thus, the method according to the present disclosure enables dynamic wireless underwater communication. Based on visual localization by a camera and optical communication, the method according to the present disclosure enables highspeed and high-capacity transmission with reduced power demand.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Non-limiting examples will now be described in reference to the accompanying drawings, where:

[0030] FIG. 1 is a schematic view of a configuration in a body of water to enable wireless underwater communication in accordance with the present disclosure.

[0031] FIG. 2 is a schematic view an acoustic positioning between a first unit and a second unit in the configuration of Fig. 1 . FIG. 3 is a schematic view of an optical positioning between the first unit and the second unit in the configuration of Fig. 1 and 2.

[0032] FIG. 4 is a schematic top view of the first unit.

[0033] DETAILED DESCRIPTION

[0034] The present disclosure will now be described in more detail without limitation in the following description.

[0035] It is provided a method of wireless underwater communication. The method comprising:

[0036] - navigating a first unit in a body of water;

[0037] - causing a second unit to acquire at least one image of the first unit using a camera on the second unit;

[0038] - based on the acquired image, navigating the second unit in the body of water so as to maintain the second unit within wireless optical communication range relative to the first unit; and

[0039] - exchanging data between the first unit and the second unit by wireless optical communication.

[0040] The body of water is for example a sea, an ocean, a lake and / or a river.

[0041] In some embodiments, operation of the first unit is controlled by way of the exchange of data by wireless optical communication with the second unit. For example, control signals for remotely operating the first unit are transmitted from the second unit to the first unit via optical communication.

[0042] In some embodiments, the first unit is configured to perform inspection of a subsea structure. Examples of the subsea structure comprises a production or injection well, pipelines and flowlines and associated structures, anchor and mooring systems for floating offshore wind turbines, surface buoys, floating production storage and offloading systems (FPSOs) and associated surface and midwater components, seafloor bathymetry, unexploded ordnances (UXOs), seafloor manmade and natural features, undersea processing systems, and any underwater facility or infrastructure for exploitation and / or production of energy.

[0043] The first unit is for example a remotely operated vehicle (ROV). The ROV is a subclass of unmanned underwater vehicles (ULIVs), which is non- autonomous and remotely controlled.

[0044] In some embodiments, the first unit is untethered. By "untethered" is meant absence of a hard-wired communication link and that the first unit is not physically connected to a surface vessel / component via one or more tether or umbilical cables for operation. Preferably, the untethered first unit is self-contained and does not require an external power source and / or communication link. In some embodiments, the first unit comprises an imaging device such as a camera.

[0045] In some embodiments, the first unit comprises one or more sensors. The one or more sensors may comprise, for example a camera, a manipulator, a thruster, a sonar, a magnetometer, a temperature sensor, a pressure sensor, and a salinity sensor.

[0046] In some embodiments, images obtained by said camera of the first unit and / or measurement data obtained by said sensor(s) of the first unit may be transmitted from the first unit to the second unit and then to the surface vessel, for example via optical communication, without a hard-wired connection such as tether and umbilical cables. In some embodiments, commands for controlling a manipulator, a thruster, and / or an operation of a sensor of the first unit may also be transmitted to the first unit from the surface vessel (via the second unit), for example via optical communication, without a hard-wired connection such as tether and umbilical cables.

[0047] The imaging device and the one or more sensors of the first unit may be used to perform the inspection of the subsea structure as described above.

[0048] The second unit is for example an autonomous underwater vehicle (AUV). In contrast to ROVs, ALIVs autonomously operate without human intervention. ALIVs may be programmed for autonomous operation.

[0049] In some embodiments, each of the first unit and the second unit comprises at least one optical emitter and at least one optical receiver. The above-mentioned optical communication may be established between the first unit and the second unit with the use of said optical emitter and receiver.

[0050] Each of the first unit and the second unit may comprise two or more optical emitters and two or more optical receivers, for example in order to provide interoperability and a wider range of applications, as well as to provide redundancy.

[0051] Each of the first unit and the second unit may comprise an optical modem, that comprises the above-described optical emitter(s) and receiver(s).

[0052] In some embodiments, optical communication is established with the use of the optical modem or the emitter(s) / receiver(s) for remote control of the first unit by a surface vessel (via the second unit), and / or data transmission between the first unit and the surface vessel (via the second unit).

[0053] Preferably, the arrangement of emitter(s) and receiver(s) on the second unit is “downwards facing”, allowing the second unit to be located above the first unit during operations to reduce a risk of entanglement of the first unit in umbilical(s) of the second unit. The second unit may be within wireless optical communication range relative to the first unit when at least one optical emitter on the first unit is within communication range with at least one optical receiver on the second unit, and when at least one optical emitter on the second unit is within communication range with at least one optical receiver on the first unit.

[0054] In some embodiments, maintaining the second unit within wireless optical communication range relative to the first unit comprises maintaining the second unit within a predetermined range of distance to the first unit and maintaining an orientation of the second unit relative to the first unit within a predetermined orientation range.

[0055] In some embodiments, the predetermined range of distance between the first unit and the second unit is between 0.5 and 10 m, preferably between 0.5 and 5 m.

[0056] In some embodiments, based on the acquired image, a distance and orientation of the second unit relative to the first unit are determined, and navigating the second unit is adjusted as a function of the determined distance and orientation.

[0057] In some embodiments, the first unit has a pattern on its surface, the acquired images comprise a captured pattern and the distance and orientation of the second unit relative to the first unit are determined depending on the captured pattern. The pattern on the surface of the first unit may be e.g. a one-dimensional pattern such as a linear barcode, a two-dimensional pattern such as a matrix code or 2D barcode.

[0058] In some embodiments, the second unit comprises a lamp which illuminates the first unit so as to allow acquiring images. For example, the camera on the second unit may be an eyeball camera. The camera and a suitable lighting provided to the second unit may also allow an improved view of the site of operation to improve situational awareness to an operator.

[0059] This image-based positioning between the first unit and the second unit may be called “visual lock” of the relative positions of the first unit and the second unit. For example, once the second unit enters the optical communication range relative to the first unit and the optical communication is established between the first unit and second unit, this relative positioning of the units is “locked” with the use of the image-based positioning, so that the optical communication link between the first unit and the second unit is maintained.

[0060] Preferably, the second unit has a Pointing - Acquisition - Tracking (PAT) capability, which is a capability to capture and track a counter-part light source or image. Specifically, once at least one image of the first unit is acquired and the “visual lock” is established, the second unit may autonomously detect, track and follow the first unit, keeping a predetermined distance from it. As the first unit moves, the change in the distance and orientation between the first unit and the second unit gives an instruction to the second unit to move accordingly, so that the second unit stays within wireless optical communication range relative to the first unit.

[0061] Alternatively or additionally, a visual odometry may be used to ascertain the change in direction and speed of the first unit and / or the second unit. For example, typical speeds of the first unit and / or the second unit are in the order of 1 -2 m / s.

[0062] Alternatively or additionally, once the “visual lock” is established, an intended flight path of the first unit may be communicated to the second unit via optical communication, thus an optimal flight path of the second unit may be calculated. This information may also be communicated to the surface vessel to allow effective route planning to maintain the visual connection between the first unit and the second unit. One or more command for controlling the first unit and / or the second unit to follow the respective flight path, thus to maintain the optical communication between the first unit and the second unit, may be transmitted from the surface vessel.

[0063] Preferably, the first unit and the second unit may be controlled as a “vehicle symbiosis” by a single operator for both units. Specifically, once the “visual lock” has been established, the operator’s controls may be relayed via the second unit to the untethered first unit by optical communication, thus the operator may command both units, maintaining a duet of vehicle movements. This may be refined by the image recognition capability of the second unit to maintain its optimal position. These commands may also be relayed to the surface vessel that may be either crewed or uncrewed itself. Alternatively, the first unit and the second unit may be controlled independently.

[0064] In some embodiments, the wireless optical communication is carried out using bidirectional laser signals between the first unit and the second unit. This advantageously enables low power consumption.

[0065] The second unit may be powered by a rechargeable battery. For example, the second unit may be charged at a surface docking station before underwater operation. Additionally or alternatively, the second unit may be temporarily deployed subsea, connected to an existing subsea infrastructure, that would enable communications via an existing communication method (e.g. optical fibers), or possibly high speed serial communication using compressed video at a low frame rate. In some embodiments, the method comprises exchanging data between the second unit and the surface vessel, preferably via an umbilical between the second unit and the surface vessel, more preferably via an optical fibre in the umbilical. For example, the second unit may receive data such as images and sensor data from the first unit, and transmit the received data to the surface vessel.

[0066] In some embodiments, the method further comprises causing the second unit to navigate towards the first unit based on acoustic communication between the first unit and the second unit, prior to causing the second unit to acquire at least one image of the first unit. In this context, the first unit and / or the second unit may comprise an acoustic modem. Such acoustic positioning may be supported by the surface vessel. The acoustic modem can be used to supplement optical communication, or as a back-up when optical communication is lost, for example. The second unit may comprise a hybrid modem and automatically switch between acoustic and optical communications.

[0067] For example, an acoustic positioning for a relatively rough alignment of the second unit with the first unit may be performed first before acquiring the image of the first unit. This may maintain a gap / distance between the first unit and the second unit within a range which is outside a visual range of the camera but falls within the optical communication range of the optical modem. The visual range of an underwater camera is typically less than 10 m, specifically around 5 m depending on the underwater condition such as water clarity and ambient light conditions, while the optical communication range of the optical modem is typically 20-30 m.

[0068] In some embodiments, the method further comprises causing the second unit to navigate towards the first unit based on optical communication between the first unit and the second unit, prior to causing the second unit to acquire at least one image of the first unit.

[0069] For example, additionally or alternatively to the above-described alignment based on the acoustic positioning, an alignment of the second unit with the first unit may be performed based on optical communication.

[0070] Preferably, after the first approximate positioning is performed based on the acoustic communication, a more refined positioning is performed based on the optical communication, then the “visual lock” is performed as described above. In other words, the positioning of the first and second units based on the acoustic communication may be refined by the optical communication before the “visual lock”. In some embodiments, the first unit and / or the second unit is self-propelled. The first unit and / or the second unit may comprise a propulsion system for providing a necessary thrust to move underwater. The propulsion system may comprise, for example, one or more motors, one or more thrusters, and / or one or more propellers.

[0071] EXAMPLES

[0072] The following examples illustrate the present disclosure without limiting it.

[0073] Fig. 1 illustrates a schematic view of a configuration in a body of water to enable the wireless underwater communication in accordance with the present disclosure.

[0074] In Fig .1 , a first unit 1 is an untethered ROV equipped with an optical modem 4. The first unit 1 comprises at least one identification feature on its surface (not shown in Fig. 1 ). A second unit 2 is an AUV tethered via an umbilical 5 to a surface vessel / component (not shown in Fig. 1 ). The second unit 2 comprises an optical modem 4, and a camera 6 with an integrated light for vehicle detection and tracking, and task site overview, for example. Each optical modem 4 comprises at least one receiver and at least one emitter (not shown). From the crewed surface component, an operator may deploy the second unit 2 with the umbilical 5 and powered from a surface component.

[0075] Fig. 2 illustrates a schematic view of an acoustic positioning between the first unit and the second unit in the configuration of Fig. 1 .

[0076] In Fig. 2, a surface component 8 supports acoustic positioning between the first unit 1 and the second unit 2. The first unit 1 may hover in the body of water, or may be parked on a docking station 7 in the body of water as seen in Fig. 2. The first unit 1 waits for a control command, for example from the surface component 8, to transmit its approximate position. Upon receiving the control command, the first unit 1 transmits its approximate position, for example by using an acoustic modem. For example, the positions and control status messages may be transferred between the first unit 1 and the surface component 8 by acoustic communications. The operator on the surface component 8 receives the approximate position information of the first unit 1 , and controls the second unit 2 to an approximate area in which the optical communication range can be acquired between the first unit 1 and the second unit 2. Alternatively or additionally, the second unit 2 may be autonomous and follow a flight path determined to move to an approximate location relative to the reported location of the first unit so as to acquire the optical communication range. In Fig. 2, the position information of the first unit is obtained by acoustic positioning supported by the surface component, and the rough alignment of the first unit and the second unit is performed based on the acoustic positioning.

[0077] Fig. 3 illustrates a schematic view of an optical positioning between the first unit and the second unit in the configuration of Fig. 1 and 2.

[0078] After navigating the second unit 2 based on the obtained position information of the first unit 1 to a location within the optical communication range relative to the first unit, optical communication is established between the first unit and the second unit, specifically via the optical modems 4 on the first unit and the second unit. Once optical communication has been established, a further refinement of position may be made until the “visual lock” (described below) is achieved between the first unit and the second unit.

[0079] Fig. 4 illustrates a schematic top view of the first unit. In Fig. 4, the first unit 1 comprises the optical modem 4 and two identification features 9 as visual features or markers on its top surface. With the visual identification features 9 on the first unit 1 , the second unit 2 can maintain its relative position to the first unit 1 in a three-dimensional Cartesian coordinate system, for example using a visual odometry, thus the “visual lock” is established between the first unit 1 and the second unit 2.

[0080] The operator on the surface component 8 may control the navigation of the second unit 2 via the umbilical 5 to maintain the “visual lock” with the first unit 1 . The operator can then take control of the untethered first unit 1 , via optical communication between the second unit 2 and the first unit 1 , to perform required operations or to control manipulator arms to perform tasks requiring intervention (for instance to pick up or move an object). In this configuration, both vehicles may be under human control, one for the first unit, and one for the second unit. The second unit may also improve situational awareness by providing an alternative view of the worksite.

[0081] Alternatively or additionally, the second unit may navigate towards the reported position of the first unit without direct operator control (for example from an remotely operated, uncrewed surface component). As described above, when optical communication has been established, the second unit may autonomously navigate to provide the visual lock with the first unit and maintain its relative position to the first unit. In this configuration, a single operator may be required for the first unit alone, with the position of the second unit maintained by tracking the identification feature on the first unit, possibly supported by flightpath communication between the first unit and the second unit. Navigation and control of the second unit may be autonomous and require no command from the operator. The commands for controlling the first unit may be provided from the operator to the second unit, then relayed to the first unit via optical communication between the first unit and the second unit.

[0082] The method according to the present disclosure may also be used to assist in a recovery of subsea located vehicles or devices equipped with a means to communicate by either acoustic, optical or RF or inductive means, for example, triggering a component to activate a function (switch on a pump, or sensor etc.).

Claims

CLAIMS1. A method of wireless underwater communication comprising: navigating a first unit in a body of water; causing a second unit to acquire at least one image of the first unit using a camera on the second unit; based on the acquired image, navigating the second unit in the body of water so as to maintain the second unit within wireless optical communication range relative to the first unit; and exchanging data between the first unit and the second unit by wireless optical communication.

2. The method according to claim 1 , wherein operation of the first unit is controlled by way of the exchange of data by wireless optical communication with the second unit.

3. The method according to claim 1 or 2, wherein each of the first unit and the second unit comprises at least one optical emitter and at least one optical receiver.

4. The method according to any one of claims 1 to 3, wherein the first unit is configured to perform inspection of a subsea structure.

5. The method according to any one of claims 1 to 4, wherein the first unit is a remotely operated vehicle (ROV).

6. The method according to any one of claims 1 to 5, wherein the second unit is an autonomous underwater vehicle (AUV).

7. The method according to any one of claims 1 to 6, wherein the first unit is untethered.

8. The method according to any one of claims 1 to 7, comprising exchanging data between the second unit and a surface vessel, preferably via an umbilical between the second unit and the surface vessel, more preferably via an optical fibre in the umbilical.

9. The method according to any one of claims 1 to 8, wherein, based on the acquired image, a distance and orientation of the second unit relative to the first unit are determined, and navigating the second unit is adjusted as a function of the determined distance and orientation.

10. The method according to claim 9, wherein the first unit has a pattern on its surface, the acquired images comprise a captured pattern and the distance and orientation of the second unit relative to the first unit are determined depending on the captured pattern.

11. The method according to any one of claims 1 to 10, wherein the second unit comprises a lamp which illuminates the first unit so as to allow acquiring images.

12. The method according to any one of claims 1 to 11 , wherein maintaining the second unit within wireless optical communication range relative to the first unit comprises maintaining the second unit within a predetermined range of distance to the first unit and maintaining an orientation of the second unit relative to the first unit within a predetermined orientation range.

13. The method according to any one of claims 1 to 12, comprising causing the second unit to navigate towards the first unit based on acoustic communication between the first unit and the second unit, prior to causing the second unit to acquire at least one image of the first unit.

14. The method according to any one of claims 1 to 13, comprising causing the second unit to navigate towards the first unit based on optical communication between the first unit and the second unit, prior to causing the second unit to acquire at least one image of the first unit.

15. The method according to any one of claims 1 to 14, wherein the wireless optical communication is carried out using bidirectional laser signals between the first unit and the second unit.

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