Efficient seafloor charging of seafloor autonomous vehicles

Abstract

The present disclosure provides for efficient seabed charging of seabed autonomous vehicles, a docking / charging module of the seabed autonomous vehicle comprising a housing that allows the seabed autonomous vehicle to dock, thereby establishing a data connection and a power connection between the module and the vehicle, the module being equipped with a battery that is charged from a seabed cable having a power conductor, the battery being able to charge the seabed autonomous vehicle via the power connection when the seabed autonomous vehicle is docked with or in close proximity to the docking / charging module.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 042,886, filed June 23, 2020, the contents of which are incorporated in their entirety. TECHNICAL FIELD

[0003] The present invention relates to the field of undersea autonomous vehicles (UAVs) and, in particular, to the charging of batteries that power these vehicles. BACKGROUND

[0004] Underwater autonomous vehicles generally include robots that operate independently underwater. Such vehicles can be remotely controlled or can be controlled by onboard software to perform specific tasks. UAVs can be deployed to perform a variety of tasks in the commercial, research, and military sectors. For example, the oil and gas industry can use UAVs to map the seafloor in detail before installing deep-sea infrastructure or pipelines. Scientists can use UAVs equipped with various sensors to measure various aspects of the undersea environment. The military has many applications for UAVs, including, for example, intelligence gathering, surveillance and reconnaissance, and wartime activities such as payload delivery and mine countermeasures.

[0005] UAVs are typically powered by rechargeable batteries. One limitation of UAVs with rechargeable batteries is that battery recharging must be performed at periodic intervals, depending on the intensity of the tasks performed. Several methods currently exist for recharging the batteries of UAVs, including physically removing the UAV from the undersea environment to land, by bringing the UAV to a ship for recharging, or by lowering a charging port from a ship into the undersea environment. In other cases, the UAV can return to land and connect to a platform for recharging, where the platform can be solar-powered, motion-powered, or wind-powered. However, removing the UAV from its primary activities to travel to shore or be recovered on the sea for battery recharging is inefficient. Moreover, requiring ground activities for battery recharging of the UAV exposes the UAV to the dangers of unwanted surveillance and inclement weather.

[0006] One or more charging stations have been deployed on the seafloor to which a UAV can connect for recharging of its batteries. Such charging stations are typically connected to an undersea cable with power capacity that is used to charge the UAV when connected to the station. The undersea cable typically has power capacity with relatively high voltage but low current. Thus, the time required to recharge the batteries of the UAV can be unacceptable.

[0007] Accordingly, it would be desirable to provide a more efficient means of recharging a UAV while keeping the UAV in the undersea environment. SUMMARY

[0008] The present invention includes a docking / charging station to which a UAV can physically or wirelessly dock. The docking station / charging station is configured with a battery or other power storage device that slowly charges from the power conductors in the branch cable of the subsea communication system while the UAV is undocked from the docking station / charging station. When the UAV is docked with the docking / charging station, the on-board battery on the UAV can be quickly charged using the on-board battery on the docking / charging station. The docking station / charging station can also be configured with data transmission and reception hardware, allowing data collected and stored by the UAV during its mission to be transferred to / from the docking station / charging station and then to / from the on-shore facility via the optical fibers in the branch cable. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a block diagram of a typical subsea communication system according to an embodiment of the present invention.

[0010] Figure 2 is a schematic representation of the power diverted from the trunk cable to the branch cable, as shown in Figure 2(A); and the power in the trunk cable isolated from the branch cable, as shown in Figure 2(B).

[0011] Figure 3 shows a schematic of the optical fibers diverted from the trunk cable to the branch cable (in Figure 3(B)); and the optical fibers diverted away from the branch cable (in Figure 3(A)).

[0012] Figure 4 is a block diagram of a power transfer unit containing a DC-to-DC conversion module (DDCM) for regulating the power to be used by the subsea payload.

[0013] Figure 5 is a block diagram of a DDCM according to an embodiment of the present invention. Figure 4

[0014] Figure 6 is a block diagram of a docking / charging station according to an embodiment of the present invention, to which a UAV is docked.

[0015] Figure 7 is a block diagram of a docking / charging station according to an embodiment of the present invention, to which a UAV is docked. Figure 6 DETAILED DESCRIPTION

[0016] Subsea communication systems typically employ a subsea cable that includes one or more optical fiber cables, each having one or more optical fiber pairs and one or more power conductors. One embodiment of a subsea communication system 100 is shown in​​Figure 1 A communication system 100 is shown in schematic form. The communication system 100 can be a long-haul undersea system configured to carry optical channels from a transmission terminal to a receiving terminal over cables of different lengths. The communication system 100 can include a trunk cable 102 that can be terminated at land-based cable landing stations (CLSs) 110 at each end of the cable. Each cable landing station can include power feed equipment (PFE) 112 for powering the cable 102 and line terminating equipment (LTE) 114 for transmitting and receiving optical signals therebetween.

[0017] The communication system 100 transmits multiple optical channels over optical fibers housed within the cable 102. The system can be bidirectional, with each LTE 114 including a receiver and a transmitter, and each optical fiber pair used for bidirectional communication. The communication system 100 can use dense wavelength division multiplexing (DWDM) to transmit communication channels over the optical fibers. A submarine cable typically includes at least one power conductor to power a plurality of submarine repeaters 116 disposed between cable landing stations for amplifying the DWDM signals, as well as various other components. The power conductor can be powered by the PFE 112 on shore on both ends of the cable. The PFE 112 typically supplies the optical cable system at between 10 kV and 20 kV, although other voltages can be used. In some embodiments, the branch cables 104 can be double conductor cables that can conduct power from the trunk and connect back to the trunk to avoid having to use an earth ground, as required by single conductor branch cables. One or more branch cables 104 can be connected to the trunk cable 102 at different locations. The branch cables 104 can be terminated on shore at the CLS 110 (not shown), or as shown in FIG. 1, terminated undersea to a deployment sled 120. The branch cables 104 terminated undersea can be used to transfer data to / from and provide power to various payloads 122A...122C connected to the deployment sled 120. The payloads 122A...122C can be, for example, different types of sensor arrays. Figure 1 Figure 1 The branch cables 104 can be terminated undersea to the deployment sled 120 as shown in FIG. 1, or on shore at the CLS 110 (not shown). The branch cables 104 terminated undersea can be used to transfer data to / from and provide power to various payloads 122A...122C connected to the deployment sled 120. The payloads 122A...122C can be, for example, different types of sensor arrays.

[0018] ​The trunk cable 102 can include a switch branching unit (sBU) 106 that is capable of switching both power and DWDM optical channels to the branch cable 104. FIG. 2(A) shows power from the trunk cable 102 being diverted to the branch cable 104 via conductor 202 and back to the trunk cable 102 via conductor 204. FIG. 2(B) shows the branch cable 104 in an unpowered, bypassed state, with power from the trunk cable 102 bypassing the branch cable 104 via a single conductor 206 in the trunk cable 102. The sBU 106 can be configured from shore via LTE 114 by sending an optical signal on a command channel to the sBU 106. As shown in FIG. 3(B), communication signals on the optical fibers in the trunk cable 102 can be diverted to the branch 104. FIG. 3(A) shows the optical fibers 302 bypassing the branch cable 104. It should be noted that while FIG. 3 appears to show only signals on one pair of optical fibers being diverted to the branch cable 106, communication signals on multiple pairs of optical fibers can be diverted from the trunk cable 102 to the branch cable 104 on a per pair basis. In some embodiments, all wavelengths of light in the optical fibers can be sent to the branch cable, or various wavelengths of light can be dropped or added.

[0019] Returning to Figure 1 One or more deployment sleds 120 can be connected to the branch cable 104. The deployment sled 120 serves as a base to which one or more payloads 122 can be connected. The payloads 122 can include, for example, various types of sensor arrays or other equipment with commercial, research, or military applications. For example, payload 122A can include a seismograph to collect seismic readings from the ocean floor. The deployment sled 120 can pass power from the branch cable 104 to the payload 122. In addition, the deployment sled 120 can enable two-way communication with the payload 122, allowing both collection of data gathered by the payload 122 and issuance of commands to configure the payload 122. The deployment sled 120 can be equipped with multiple commercially available wet mate connectors or other types of connectors, such that one or more payloads 122 can be easily connected to or disconnected from the deployment sled 120. Wireless technology can also be used for power and data connections. Alternatively, a single payload 122 can be connected directly to the branch cable 104 without the need for a deployment sled 120.

[0020] Because the trunk cable 102 typically operates at 10 to 20 kV, the power delivered to the branch cable 104 can be adjusted by a power transfer unit (PTU) 108. The PTU 108 can include a DC-to-DC converter module (DDCM) that can step the voltage from the high level at the trunk cable 102 to a lower level required by the payload 122 attached to the branch cable 104. In some embodiments, the PTU 108 can be controlled from shore by sending command signals over one or more of the sideband or command bands in the optical fiber to control the level of voltage delivered to the payload 122 attached to the branch cable 104, and in addition to control the current level. The PTU 108 thus isolates the payload 122 from the high trunk voltage. The PTU 108 can be controllable to provide constant current or constant voltage operation to the payload 122, and can be set to limit the output power to a value less than its full output power potential.

[0021] Figure 4 is a block diagram of the PTU 108. The PTU 108 is coupled to the branch cable 104 downstream of the sBU 106. For purposes of explanation, assume that the branch cable 104 has two power conductors 408a and 408b. The trunk cable 102 can have a single power conductor or dual power conductors. The PTU 108 includes a power and telemetry unit 402 that includes circuitry and components adapted to send and receive optical signals via the optical fiber 406 in the branch cable 104. In this case, the sBU 106 must be configured to pass the optical signals from the optical fiber in the trunk cable 102 to the optical fiber in the branch cable 104. The power and telemetry unit 402 uses the received optical signals to configure and adjust the operation of a DC-to-DC converter module (DDCM) 404, for example, to apply new operating parameters such as voltage set points and source mode (constant current, constant voltage). At 410, the adjusted voltage is output from the PTU 108 to a downstream destination (e.g., the deployment skid 120) to power one or more payloads 122.

[0022] Figure 5This diagram illustrates one possible embodiment of a DDCM 404 suitable for use in a PTU 108. The DDCM 404 includes first, second, and third ports 408a, 408b, and 410, each of which is configured to be coupled to an electrical conductor of a cable segment. For example, the first port 408a may be configured to be coupled to a first electrical conductor of a branch cable 104. The second port 408b may be configured to be coupled to a second electrical conductor of the branch cable 104, and the third port 410 may be configured to be coupled to an electrical conductor downstream of the branch cable 104. The DDCM 404 may be configured to draw current from one or both of the first and second ports 408a and 408b to supply power to the branch cable via the third port 410.

[0023] As further shown, the DDCM 404 includes clamping circuitry 502, first and second converters 504-1 and 504-2, controller 506, rectifier 514, filter 516, and clamping circuitry 508. Controller 506 can be powered via a power supply in the power and telemetry unit 402 of PTU 108. In some cases, controller 506 may be implemented within the power and telemetry unit 402 and is not necessarily a separate component as shown. Controller 506 can be implemented as a microprocessor, processor, circuit system, field-programmable gate array (FPGA), or any other suitable controller device. The first and second converters 504-1 and 504-2 can be configured to generate a regulated DC voltage and then chop the regulated DC voltage to generate an AC signal. Although Figure 5 Only the first and second converters are shown, but it should be recognized that multiple converters can be used. The AC output can then be isolated by a transformer and then rectified and filtered via rectifier 514 and filter 516, respectively, to produce a DC output. The output section of the DDCM can be configured with multiple stages. For example, a clamping circuit 508 on the output can ensure that the cable is discharged for worker safety. During a cable fault, a clamping circuit 502 on the input redirects (e.g., provides a path) the surge current around the converter. The clamping circuit 502 can also clamp to ground on each trunk cable to protect workers during repairs of the individual trunk cables.

[0024] The first and second converters 504-1, 504-2 can thus provide two power stages. Each of the first and second converters 504-1, 504-2 can include a boost converter (not shown) and a chopper (not shown). For example, the first and second converters 504-1, 504-2 can be configured with a half-bridge (e.g., two transistor configuration) or full-bridge (e.g., four transistor configuration) switching arrangement. Each of the first and second converters 504-1, 504-2 can be operated according to a current operating mode by, for example, soft switching (e.g., PWM signals) via the controller 506 to direct a certain portion of line current from one or both of the first and second ports 408a, 408b. Other power conditioning schemes are within the scope of the present disclosure, and the present disclosure is not necessarily limited to PWM implementations. Further, a common transformer can be used with magnetic flux, adding power at the output stage. In any case, the first and second converters 504-1, 504-2 can feed boosted current to a chopper, with each respective chopper driving a primary winding of an isolation transformer 530. The isolation transformer 530 can provide galvanic isolation between the first and second ports 408a, 408b and the third port 410.

[0025] Each of the boost converters of the first and second converters 504-1, 504-2 can be driven by the controller 506 via first and second pulse width modulation (PWM) signals, respectively, where the first PWM signal is different than the second PWM signal. The controller 506 can draw an asymmetric load from each of the first and second ports 408a, 408b based on the first and second PWM signals. The controller 506 can thus draw different amounts of power from the first and second ports 408a, 408b to achieve a desired output current / voltage. Depending on the desired configuration, each of the first and second converters 504-1, 504-2 can be configured to be the same or different. Regulation of the output (e.g., port 410) is relatively similar to regulation of a single-input converter, with the addition of a control scheme that ensures switching of the first and second converters 504-1, 504-2 to selectively draw current from each of the first and second ports 408a, 408b. Switching in such a manner can ensure that the first converter 504-1 is switched“on” while the second converter 504-2 is switched“off,” and vice versa, to prevent simultaneous passing of inputs through both ports. During the time each of the converters 504-1, 504-2 is switched“on,” current flows through the ports 408a, 408b. By controlling the proportion of time the first converter 504-1 is switched on relative to the second converter 504-2, the ratio of input currents can be controlled. In embodiments, the ratio of input currents between the first and second ports 408a, 408b does not necessarily depend on the total output load current, so long as the duty cycle control (e.g., the first and second PWM signals) to each of the first and second converters 504-1, 504-2 is scaled in such a way that the ratio of inputs via the first port 408a and the second port 408b remains substantially constant. In some cases, the DDCM 404 can utilize an in-cycle switching scheme or other scheme such as cycle-by-cycle operation to output a constant current or constant voltage. The described embodiments of the DDCM 404 should be considered merely exemplary. Other embodiments of the DDCM 404 are possible within the intended scope of the present disclosure.

[0026] Reference Figure 6 One of the payloads 122 can be a docking / charging station 602 for the UAV 750, which is shown in schematic form as being docked to the docking / charging station 602 in Figure 7 The UAV 750 generally includes a battery 752 to power the UAV 750 and to power onboard circuitry for navigation and for controlling tasks to be performed by the UAV 750. The UAV 750 can also include a data storage 754 containing data collected by the UAV 750 upon disengagement from the docking / charging station 602.

[0027] Further reference Figure 7 The docking / charging station 602 can be connected to the deployment tray 120 and can be configured with a battery 704 that can be slowly charged when the UAV 750 detaches from the docking / charging station 602. Because the branch cable 104 has a limited power delivery capacity, the battery 704 can be slowly charged over time while the UAV 750 is detaching from the docking station 602. When the UAV 750 docks with the docking / charging station 602, the battery 752 in the UAV 750 can be rapidly charged from the battery 704 in the docking / charging station 602.

[0028] Furthermore, the docking station / charging station 602 may be equipped with a data exchange module 706 to transmit data collected by the UAV 750 and stored in the data storage device 754 via an optical fiber included in the branch cable 104. Additionally, when the UAV 750 engages with the docking / charging station 602 for charging, data and new task instructions can be transmitted from the docking / charging station 602 to the UAV 750. In some embodiments, the deployment tray 120 may be optional, and the branch cable 104 may be directly connected to the docking / charging station 602.

[0029] Apart from Figure 7 In addition to the components shown, docking / charging station 602 may also include hardware that allows UAV 750 to engage (dock) with docking / charging station 602. Note that UAV 750 may "engage" with docking / charging station 602 by physically docking or otherwise establishing one or more physical data and power connections between UAV 750 and docking / charging station 602. In other embodiments, the term "engage" may be interpreted as meaning the wireless exchange of data and / or power between UAV 750 and docking / charging station 602. Furthermore, docking / charging station 602 may be further configured with hardware that acts as a beacon or transmitter, thereby allowing UAV 750 to easily locate and / or identify docking / charging station 602. In other embodiments, the data connection between UAV 750 and docking / charging station 602 may be bidirectional, thereby allowing commands or procedures to be transmitted to UAV 750 via branch cable 104.

[0030] Various embodiments have been generally described. As those skilled in the art will recognize, actual implementations of the invention may deviate from the described embodiments, but will be within the scope of the invention as set forth in the following claims.

Claims

1. A seafloor docking / charging module for a seafloor autonomous vehicle, comprising: a housing; a connection to a seafloor cable; a battery, the battery disposed within the housing, and a data exchange module for exchanging data with a seafloor autonomous vehicle and with a land-based station via a seafloor cable, wherein the seafloor cable has both a power conductor and an optical fiber for data transmission, the connection to the seafloor cable comprising: a power connection to the power conductor; and a data connection to the optical fiber, wherein the seafloor docking / charging module is configured to engage with the seafloor autonomous vehicle for transferring power from the battery to the seafloor autonomous vehicle, wherein the battery is charged via the power connection to the seafloor cable.

2. The seafloor docking / charging module of claim 1, further comprising: a connection between the seafloor docking / charging module and the seafloor autonomous vehicle for transferring data between the seafloor docking / charging module and the seafloor autonomous vehicle.

3. The seafloor docking / charging module of claim 1, wherein the power connection and data connection to the seafloor cable are via a deployment sled for providing power and data links between the seafloor cable and the seafloor docking / charging module.

4. The seafloor docking / charging module of claim 1, wherein the data exchange module performs the following functions: receiving data collected by the seafloor autonomous vehicle and transmitting the data to the land-based station via the seafloor cable; transmitting data from the land-based station to the seafloor autonomous vehicle.

5. A method of providing fast charging to a seafloor autonomous vehicle, comprising: navigating the seafloor autonomous vehicle to a seafloor docking / charging module according to any one of claims 1 to 4; docking the seafloor autonomous vehicle to the seafloor docking / charging module, the docking comprising establishing a physical connection for transferring power from the seafloor docking / charging module to the seafloor autonomous vehicle; transferring power from a charging battery on the seafloor docking / charging module to a battery on the seafloor autonomous vehicle; and disconnecting the physical connection; wherein the seafloor docking / charging module is connected to a seafloor cable, the seafloor cable having a power connection and a data connection to a land-based station.

6. The method of claim 5, further comprising: transferring data from a data storage device on the seafloor autonomous vehicle to the seafloor docking / charging module; and transferring the data from the seafloor docking / charging module to a ground station or to another device in communication with the seafloor docking / charging module via the seafloor cable.

7. The method of claim 6, further comprising: transferring data from the ground station to the seafloor docking / charging module via the seafloor cable; and transferring the data from the seafloor docking / charging module to a data storage device on the seafloor autonomous vehicle.

8. The method of claim 5, further comprising: ​ ​ ​ ​ When the seafloor autonomous vehicle is disengaged from the seafloor docking / charging module, the battery on the seafloor docking / charging module is charged via the power connection in the seafloor cable.

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