SYSTEM AND METHOD FOR RETRIEVING DAUGHTERBOATS TO A MOTHERSHIP

Abstract

A system for retrieving manned or unmanned daughter boats onto a mothership. The mothership has a crane/davit, a lifting wire connected to a winch, a first connecting device and a drone assembly including propellers and motors. The daughter boat has a second connecting device for cooperation with the first connection device. The drone assembly is removably fastened to the lifting wire and is provided to move the lifting wire and the first connection part in a horizontal plane to a required position above the second connection part. The winch of the mothership might be connected to a winch control system in order to keep the first connection part in a required vertical position for connection to the second connection part.

Description

TECHNICAL FIELD

Present invention relates to a system and method for handling daughter boats, such as manned and unmanned surface vehicles (USV's) while using a standard davit or crane on a mothership for launch and recovery of said daughter boat.

The inventors have long been on a quest to find the best solution, which works in harsh weather conditions as well as during calm weather, for handling daughter boats, such as unmanned surface vehicles (USV's) while using a standard davit or crane. Today one of the identified challenges is related to manually catching the lifting wire (with hook or ring) and then insert that into the counterpart installed in the daughter boat (hook or ring). In harsh weather the catching is considered both difficult and sometimes dangerous.

The present invention add the possibility of handling unmanned surface vehicles (USV's) by a standard davit designed to conduct launch and recovery of manned daughter boats. As the name «unmanned» imply the boat is unmanned and typically remotely operated. There are today no known solutions for completing the hook/ring connection using a standard davit that also work in harsh weather condition. Complicating the matter; some shipping companies are considering building vessels (motherships) that operates autonomously, remote controlled or with reduced crew, which needs to be able to launch and recover smaller USV/AUV's. The final solution aim to address several challenges at a proven low failure-rate.

BACKGROUND ART

JP6630893B1 describes a lifting system including a rotary wing device often referred to as a drone (quad-, hexa-, octo-copter) mounted in a gimbal-mechanism being attached to a lifting tool. The orientation of the rotary wing device inside the gimbal-mechanism is controlling the direction of the thrust. A horizontal thrust is generated in the rotary wing device (by orientation of the drone in the gimbal-mechanism) and control is performed to move a sling toward a target point. In this system, the rotary wing device constitutes a part of the lifting system itself and the rotary wing device is not removable from the lifting system.

JP2019069835A describes a crane hook device and a stabilization method of a hanging load posture to stabilize the hanging load when the hanging load swings and turns, by using a drone to apply external force on the crane hook to stop the detected motion. Also here, the drone constitutes a part of the lifting system itself, and the drone is not removable from the lifting system.

CN206680084U describes a lifting hook control system using a drone to control the lifting hook. In this embodiment, the drone is a part of the hook and is not removable from the lifting system.

Publications describing similar uses of drones to stabilize lifting hooks are for example CN110360638 and JP6583900B1.

There are today other solutions for launch and recovery of manned and unmanned surface vehicles (USV's) and the most common solution is to either use what is called a stern-launch or to use a floating-dock. While both solutions have proved their worth, they both comes with some trade-offs.

The stern-launch need to be included in the design of the mothership and it also require spending some amount of the volume of the stern. For existing ships, a rebuild is costly. Retrieving a manned daughter boat into the stern opening can sometimes be challenging in «calm» weather, not to mention in harsh weather.

The floating dock is a boat-shaped dock attached to the mothership (lifted by crane or davit) in which the USV is driven into. The known floating-docks today is both physically bigger than the USV and have a certain amount of mass that the davit or crane needs to handle. This implies that using a floating dock require a physically bigger davit with higher maximum workload (MWL) to handle the USV compared to a davit that is lifting the USV directly. A floating dock is also a technical equipment that has a cost both relating to purchase and maintenance. The floating dock also need space on the mothership, and it may be necessary to remove the daughter boat from its cradle for storing. All this handling is needed and require extra space in the daughter boat hangar. The purpose of present invention is to provide a cost-efficient solution to safely launch and recover manned and unmanned daughter boats using an existing standard davit or crane. Hence the existing motherships can upgrade to handling of daughter boats without replace/rebuilding the davits. Similarly, newbuild ships will only require a standard davit or crane to include USV handling.

SUMMARY OF INVENTION

These and other purposes and advantages are obtained by a system according to the invention for retrieving manned or unmanned daughter boats onto a mothership, where the mothership has a crane/davit, a lifting wire connected to a winch, a first connection device and a drone assembly comprising propellers and motors, and the daughter boat has a second connection device for cooperation with the first connection device, wherein the drone assembly is removably fastened to the lifting wire and is provided to move the lifting wire and the first connection part in a horizontal plane to a required position above the second connection part, and that the winch of the mothership might be connected to a heave compensator controller in order to keep the first connection part in a required vertical position for connection to the second connection part.

The drone assembly preferably comprises one or more sensors which can read a marking at or in the vicinity of the second connection part, said sensors communicates with a drone controller regulating the horizontal position of the drone assembly in response to information from the sensor(s) and position the first connection part in the required position above the second connection part for connection of the two connection parts.

A sensor (IMU) in the drone/actuator assembly detect motion/speed of the pendulum motion and the software/controller regulate thrust to reduce and eventually stop the motion. This result in the lifting wire-connector to remain more stationary while the mothership moves due to waves. As a result, it will be easier for a person to grab the connector (if manned) or for the daughter boat to position correctly underneath the lifting point of the davit/crane. This phase will occur before the sensors detect the daughter boat under the davit. When the sensors detect the daughter boat under the davit the drone/actuator assembly will instead target to position itself directly above the counterpart mounted in the daughter boat.

The sensor or sensors is/are preferably one more cameras which are able to locate the marking on the daughter boat.

The marking(s) on the daughter boat is/are a sensor readable QR-marking, an Aruco code marker, an April tag or similar.

According to another preferred embodiment the marking(s) on the daughter boat is a sound producing device.

In one embodiment, the winch control system and the drone controller are interconnected and can operate the system in an automatic mode.

The movement of the drone assembly in the horizontal plane controlled by the drone controller, is preferably obtained by either 1) reversing the rotational direction of the drone motors and reversing the thrust of the propellers, 2) by moving the direction of the propellers, for example by means of servo motors and turn the thrust of the propellers in another direction, or 3) having 4 (or 8) separate motors and propellers mounted in a fixed arrangement whereby they provide thrust in each horizontal direction.

According to another preferred embodiment the daughter boat to be retrieved is a submerged vehicle and the drone assembly is an underwater drone assembly.

According to a preferred embodiment where the second connection part comprises a funnel and a female connection part, whereas to minimize the dimensions of the installation in the daughter boat while still being able to connect in harsh weather, the funnel is designed to fold/collapse away when not needed and to extend/fold into shape before connection.

In order to extend the window of operation, the winch preferably uses an active heave compensation mode to keep the vertical distance to the daughter boat.

In an alternative embodiment, the second connection part is preferably mounted on the lifting wire and the first connection part is mounted in the daughter boat, allowing the second connection part being integrated in the spelter-socket and reducing the overall dimension (height) of the installation.

In order to increase the window of operation, the drone part preferably includes a dynamically extending part that is able to extend faster than the winch can lower, and catch the counter part on the daughter boat, and this create a guide between the drone/wire and the daughter boat.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts a first embodiment of the complete recovery system according to the invention with a one point lift.

FIG. 2 depicts a second embodiment of the complete recovery system according to the invention with a two point lift.

FIG. 3 depicts a drone assembly with hook connector.

FIG. 4 depicts a lifting wire with drone locked in boat hook

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts one embodiment of the complete recovery system according to the invention. In this embodiment, the system comprises a crane/davit (7) on a mother ship. The crane/davit (7) can be a standard crane/davit normally used for deployment and recovery of daughter boats onto a mothership. The crane/davit is provided with a lifting wire (5). The daughter boat (8) can be a manned or unmanned vehicle (USV—unmanned surface vehicle). The winch motor of the crane/davit (7) can be connected to an active heave compensator controller (not shown) in order to keep the lifting wire (5) in a stable vertical position above the daughter boat (8).

The lifting wire (5) is provided with a detachable drone assembly (1), which will be explained in more detail later with reference to FIG. 3. One end of the wire (5) is connected to the crane/davit (7) and the other end of the wire (5) is provided with a first connection part (2), for example a hook connector. The drone assembly (1) is provided above the first connection part (2) and the first connection part (2) may be connected to the wire (5) via a spelter socket (6).

The daughter boat (8) is provided with a second connection part (3), for example a hook which can make engagement and lock with the first connection part (2) on the wire (5). The second connection part (3) is provided with a guide funnel. Further, the daughter boat (8) is provided with one or more sensor readable markings (4). The markings (4) can be a QR marking, an Aruco code, an April Tag or similar. Other types of markings are also conceivable such as an audio systems which can be used to locate and lock the first connection part (2) on the target.

FIG. 2 shows an embodiment with two lifting points, but the arrangement and components are identical to those shown in the embodiment in FIG. 1.

FIG. 3 depicts the drone assembly (1) in more detail. The drone assembly is a detachable unit which can be clamped or otherwise easily fastened on and removed from the wire (5) when handling of the daughter boat is required. The drone has several propellers (1.1) which can be separately controlled to move the drone assembly (1) to the required horizontal position. The purpose of the drone assembly (1) is to control (dampen) the pendulum motion of the lifting wire (5) when the mothership is moving due to waves and wind induced motion and locate the first connection part (2) in correct horizontal position for engagement with the second connection part (3) on the daughter boat (8). The drone assembly (1) comprises one or more sensors (1.3) which are able to read the marking(s) (4) on the daughter boat (8). In one preferred embodiment, the sensors (1.3) can be one or more cameras which are able to read the markings (4) on the daughter boat (8). The sensor(s) (1.3) is connected to a control device (not shown) which makes it possible to determine and move the drone assembly (1) to the required position above the second connection part (3) on the daughter boat (8) for engagement. In one preferred embodiment, the control device of the drone assembly (1) and the heave compensator of the davit/crane (7) can be connected or be the same control unit for controlling both the vertical position of the wire (5) and the horizontal position of the drone assembly (1). When the first and second connection parts (2, 3) are aligned in the correct position, the winch motor is actuated to lower the first connection part (2) onto the second connection part (3) whereby the connection parts be locked together.

In a further preferred embodiment, the control devices of the drone assembly and the davit/crane (7) makes it possible to locate and connect the daughter boat (8) to the first connection part (2) without human interference.

The drone assembly (1) comprises several propellers (1.1) with motors (1.2) which makes the drone assembly (1) movable a horizontal plane (x, y plane). The motors (1.2) are controlled by the control device. The drone motors (1.2) can operate in two different mode, 1) the motors and propellers can be reversed and provide thrust in the opposite (both) directions, by doing this, the number of motors (1.2) can be reduced while keeping the amount of thrust unchanged, or 2) the direction of the propellers can be changed, for example by means of servo motors, and turn the thrust of the propellers in the wanted direction. The advantage of alternative 2) is to keep high thrust while reducing the number of motors/propellers. This two alternatives are to allow function of the drone assembly (1) if one or more of the propellers/motors become damaged or stop functioning. If the thrust can be reversed and/or the propeller can be rotated, it will be able to create thrust in any direction. Hence 4 motors/propellers create normal thrust while one propeller/motor creates ¼ of the normal thrust.

One embodiment of the connection parts of the system according to the invention is shown in FIG. 4, which shows the wire (5), the drone assembly (1), with the first connection part (2) and the second connection part (3), and the sensor readable marking (4). In this embodiment, the position of the marking (4) is offset from the connection position of the first and second connection parts (2, 3) but this offset distance has been programmed into the controller. The first and second connection parts (2, 3) can for example be of the type described in U.S. Pat. No. 9,488,203. In the shown embodiment, the second connection part (3) is provided with a guide funnel which guide the first connection part (2) into the correct position above the second connection part (3) for connection of the two parts. In an alternative embodiment, both the first connection part (2) and the second connection part (3) can be provided with magnetic devices in order to place the two parts in the correct mutual position for connecting the two parts together.

In an alternative embodiment, the system according to present invention can also be used to retrieve submerged vehicles and then the drone (1) is an underwater drone.

LIST OVER REFERENCE NUMERALS

• • 1. Drone assembly
  • 1.1 Drone propellers
  • 1.2 Drone Engine
  • 1.3 Sensors
  • 1.4 Sphere body of drone (two parts)
  • 2. First connection part
  • 3. Second connection part
  • 4. Visual code
  • 5. Lifting wire
  • 6. Spelter socket
  • 7. Crane/Davit
  • 8. Daughter boat

Claims

1. A system for retrieving manned or unmanned daughter boats onto a mothership, where the mothership has a crane/davit, a lifting wire connected to a winch, a first connecting device and a drone assembly comprising propellers and motors, and the daughter boat has a second connecting device for cooperation with the first connection device, wherein the drone assembly is removably fastened to the lifting wire and is provided to move the lifting wire and the first connection part in a horizontal plane to a required position above the second connection part, and the winch of the mothership might be connected to a winch control system in order to keep the first connection part in a required vertical position for connection to the second connection part.

2. The system according to claim 1, wherein the drone assembly comprises one or more sensors which can read a marking at or in the vicinity of the second connection part, said sensor(s) communicate(s) with a drone controller regulating the horizontal position of the drone assembly in response to information from the sensor and position the first connection part in the required position above the second connection part for connection of the two connection part.

3. The system according to claim 1, wherein the sensor or sensors is/are one or more cameras which are able to locate the marking on the daughter boat.

4. The system according to claim 1, wherein the marking on the daughter boat is/are a sensor-readable QR-marking, an Aruco code marker, an April Tag or similar.

5. The system according to claim 1, wherein the marking on the daughter boat is/are a sound producing device.

6. The system according to claim 1, wherein the winch control system and the drone controller are interconnected and can operate the system in an automatic mode.

7. The system according to claim 1, wherein the movement of the drone assembly in the horizontal plane controlled by the drone controller, is obtained by either 1) reversing rotational direction of the drone motors and reversing the thrust of the propellers or 2) by moving the direction of the propellers, for example by means of servo motors and turn the thrust of the propellers in another direction, or 3) having 4 (or 8) separate motors and propellers mounted in a fixed arrangement, whereby they provide thrust in each horizontal direction.

8. The system according to claim 1, wherein the daughter boat to be retrieved, is a submerged vehicle and the drone assembly is an underwater drone assembly.

9. The system according to claim 1, where the second connection part comprises a funnels and a female connection part, whereas to minimize the dimensions of the installation in the daughter boat while still being able to connect in harsh weather, the funnel is designed to fold/collapse away when not needed and to extend/fold into shape before connection.

10. The system according to claim 1, whereas to extend the window of operation, the winch uses an active heave compensation mode to keep the vertical distance to the daughter boat.

11. The system according to claim 1, whereas the second connection part is mounted on the lifting wire and the first connection part is mounted in the daughter boat, allowing the second connector part being integrated in the spelter-socket and reducing the overall dimension of the installation.

12. The system according to claim 1, whereas to increase the window of operation, the drone part includes a dynamically extending part that is able to extend faster than the winch can lower, and catch the counter part on the USV, and thus create a guide between the drone/wire and the USV.