Vertical motion reduction device, work ship, and vertical motion reduction method of transport barge

Abstract

To provide a device capable of improving an operation rate of a ship-to-ship transfer work, and to provide a work ship and a method.SOLUTION: A vertical motion reduction device of a work ship includes: one or more vertical thrusters 40 arranged underwater on an outboard side of the work ship to generate a vertical thrust of the work ship; a sensor 41 for detecting pitching and rolling at a gravity center position of the work ship; a sensor 42 for detecting a vertical motion at a prescribed position of the work ship; and a controller 43 for controlling the vertical thrust generated by each of one or more vertical thrusters 40 based on a detection result by the sensor 41 and the sensor 42.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a device for reducing vertical motion of a work boat, and a method for reducing vertical motion of a work boat and a transport barge. [Background technology]

[0002] When constructing offshore structures such as offshore wind power facilities, a self-elevating platform vessel (SEP vessel) is used as the work vessel, which loads construction materials at the quay and then moves to the installation area for installation work. If the SEP vessel can stay at the installation area and another work vessel such as a transport barge can be used to transport the construction materials and install them on board the SEP vessel or at the site by ship-to-ship transfer, the time that the expensive SEP vessel is occupied can be reduced, contributing to reducing construction costs. Here, ship-to-ship transfer refers to the lifting and unloading work carried out between vessels at sea.

[0003] However, when lifting heavy objects such as construction materials from a transport barge at sea, even if the SEP vessel is secured, the transport barge is constantly rocking due to waves, making it an extremely dangerous task.

[0004] A transport barge is a vessel with a box-shaped shape that has excellent loading capacity, but it is subject to large oscillations due to waves. For this reason, when used for ship-to-ship transfer operations, the oscillations of the transport barge can be reduced by mooring it at multiple points with anchors or by using a dynamic positioning system (DPS) that controls the propellers on the bottom of the vessel to maintain position.

[0005] With this method, horizontal displacement parallel to the sea surface can be sufficiently reduced by anchor mooring and the propulsive force of the DPS, but the DPS has almost no effect on reducing vertical (up and down) motion perpendicular to the sea surface, and anchor mooring only reduces it slightly.

[0006] Known technologies for reducing vertical oscillation include a technology that actively drives a fin attached to the bow (see Non-Patent Document 1) and a technology that absorbs the hull movement using a parallel mechanism device consisting of six hydraulic cylinders (see Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Mamiko Kanemoto, Yasuo Yoshimura, "Effects of Active Fins on Rolling Reduction and Propulsive Performance", Proceedings of the 23rd Conference of the Japan Society of Naval Architects and Ocean Engineers, November 22, 2016, pp.389-392 [Non-Patent Document 2] Yutaka Tanaka, “Movement Absorber Using Hydraulic Motion Base”, [online], November 2018, Measurement and Control, Vol. 57, No. 11, [Retrieved July 22, 2022], Internet<URL:https: / / www.jstage.jst.go.jp / article / sicejl / 57 / 11 / 57_803 / _pdf / -char / ja> Summary of the Invention [Problem to be solved by the invention]

[0008] In order to improve the operating rate of ship-to-ship transfer operations, it is desirable to minimize the rocking of the area where the load to be hoisted by the crane is located. However, the conventional technology in Non-Patent Document 1 aims to reduce the vertical movement, including the rotational movement, of the entire ship. In addition, the conventional technology in Non-Patent Document 2 is a device that is only intended for the top of the device, and there is a problem in that a very large device is required to control the heavy load that is the subject of the crane operation. [Means for solving the problem]

[0009] The present invention has been made in consideration of the above problems, and provides a vertical motion reduction device for a work vessel, One or more thrust generating means are disposed in the water outside the work vessel and generate thrust in the vertical direction of the work vessel; A first detection means for detecting pitching and rolling at the center of gravity of the work vessel; A second detection means for detecting vertical movement of the work vessel at a predetermined position; a control means for controlling a vertical thrust generated by each of the one or more thrust generating means based on detection results of the first detection means and the second detection means; A heave reduction device is provided, comprising: Effect of the Invention

[0010] According to the present invention, the operating rate of ship-to-ship transfer operations can be improved. [Brief description of the drawings]

[0011] [Figure 1] Conceptual diagram of the transfer of wind turbine components by SEP vessel. [Diagram 2] Conceptual diagram of the transfer of jacket foundation by a derricking crane barge. [Diagram 3] FIG. 1 shows an example of a transport barge. [Figure 4] FIG. 2 is a diagram showing a configuration example of a vertical motion reducing device. [Diagram 5] FIG. 13 is a diagram illustrating control for reducing the vertical movement of the transport barge. [Figure 6] FIG. 13 is a diagram illustrating control for reducing the vertical movement of the transport barge. [Figure 7] FIG. 13 is a diagram showing another example of the configuration of the vertical motion reducing device. [Figure 8] FIG. 13 is a diagram showing an example of an analysis model for performing a numerical analysis when a vertical thruster is installed. [Figure 9] FIG. 13 is a diagram showing an example of an analytical model for performing numerical analysis when a submerged horizontal plate is installed. [Figure 10] A diagram showing an example of mean significant wave height and mean significant period on the Sea of ​​Japan side. [Figure 11] A diagram showing an example of mean significant wave height and mean significant period on the Pacific side. [Figure 12]FIG. 10 is a diagram showing a first result of an analysis performed using the analytical model shown in FIG. [Figure 13] FIG. 10 is a diagram showing a second result of an analysis performed using the analytical model shown in FIG. 9 . [Figure 14] FIG. 9 is a diagram showing a first result of an analysis performed using the analytical model shown in FIG. 8 . [Figure 15] FIG. 9 is a diagram showing a second result of an analysis performed using the analytical model shown in FIG. 8 . [Figure 16] 5 is a flowchart showing an example of an operation of reducing vertical movement by the vertical movement reducing device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Before describing the vertical motion reduction device, the work ship, and the method for reducing the vertical motion of the work ship of the present invention, the construction of an offshore structure at sea will be described. FIG. 1 is a conceptual diagram of the transfer of wind turbine components constituting an offshore wind power generation facility as an example of an offshore structure. Note that the offshore structure is not limited to an offshore wind power generation facility. The SEP vessel 10 is one of the work ships and has a barge 11, a lifting leg 12, and a crane 13. The SEP vessel 10 is fixed to the installation area by lowering the lifting leg 12 to the seabed, and after the barge 11 is raised above the sea surface, the installation work of the wind turbine components is performed using the crane 13, etc.

[0013] The SEP vessel 10 can load several wind turbine components and the like at the quay, move to the installation area, and perform installation work. However, if the SEP vessel 10 is repeatedly loaded with construction materials, moved from the quay to the installation area, and then returned to the quay to load construction materials again, the expensive SEP vessel 10 will be occupied for a long time, and construction costs will increase. For this reason, the SEP vessel 10 can lower the lifting legs 12, maintain the barge 11 elevated above sea level, and transport the construction materials using the transport barge 14, which is one of the work vessels. This allows the SEP vessel 10 to install the wind turbines one by one with small movements. In other words, the SEP vessel 10 only needs to lift and lower the lifting legs 12 to install each wind turbine, return the lifting legs 12, move to the adjacent foundation (wind turbine installation position), lift and lower again, and install the wind turbines again, and this reduces the movement time of the SEP vessel 10, which reduces the occupation time of the expensive SEP vessel 10, and leads to a reduction in construction costs.

[0014] As shown in Fig. 2, a wind power generation facility is installed on the seabed by lifting a jacket foundation 21, which serves as the base of the wind power generation facility, with a crane from a derricking crane ship 20. When performing crane work, the derricking crane ship 20 is fixed to the installation area by dropping an anchor.

[0015] The jacket foundation 21 and piles 22 can be transported from the quay to the installation area by the derricking crane ship 20, and then penetrated and installed. However, if the derricking crane ship 20 is used for transportation as well, the period of offshore construction will be longer and the construction costs will increase. For this reason, like the SEP ship 10, the derricking crane ship 20 can also be anchored and maintained fixed in the installation area, and the jacket foundation 21 can be installed at low cost using the transport barge 14.

[0016] In the example shown in Fig. 2, the derricking crane ship 20 is lifting (transporting) one of two jacket foundations 21 that have been placed on the deck of the transport barge 14. The foundation type is not limited to the jacket type using the jacket foundation 21, and may be a monopile type or a tripod type.

[0017] In the example shown in FIG. 1, a tower 15 is installed by an SEP vessel 10, and a deck-type transport barge 14 transports wind turbine components 16 on its deck. The wind turbine components 16 include three blades that constitute the wind turbine, a rotor shaft having a hub to which the three blades are connected, a generator connected to the rotor shaft and generating electricity by the rotation of the rotor shaft, a brake device connected to the rotor shaft and stopping the rotation of the rotor shaft, a speed increaser that increases the rotation of the wind turbine to the number of rotations required for generating electricity, a yaw control device that causes the direction of the rotor shaft to follow the wind direction, and an anemometer. The generator, brake device, etc. are stored in a nacelle that serves as a housing. The nacelle also serves to provide waterproofing and soundproofing.

[0018] In FIG. 1, a component in which two blades are connected via a rotor shaft to a nacelle housing a generator etc., and one blade, are transported as wind turbine component 16 onto the deck of a transport barge 14. The SEP vessel 10 uses a crane 13 to hoist the wind turbine component 16 and installs it on top of an already installed tower 15. Specifically, the component with the two blades connected is first installed at the top of the tower, and the remaining blade is attached to the hub. In this way, the wind power generation facility can be installed by offshore construction.

[0019] Incidentally, when lifting heavy objects such as wind turbine components 16 from the transport barge 14 at sea, even if the SEP vessel 10 is fixed, the transport barge 14 is constantly swaying due to waves and the like. For this reason, the heavy objects are displaced in the horizontal and vertical directions (up and down directions), and if they are lifted in this state, there is a possibility of collision with nearby workers or other heavy objects, making it a very dangerous operation. The lifting work of lifting heavy objects is dependent on oceanographic conditions such as the limit wave height for operation, and it needs to be carried out when the oceanographic conditions are good and the operation can be carried out safely and efficiently (for example, when the waves are calm).

[0020] The limit wave height for work is the maximum wave height at which work can be performed by a work vessel. In addition to wave height, oceanographic conditions include wave direction, wavelength, period, etc. Here, if the total time is x hours, and the time during x hours when the vessel's motion is small and transfer operations can be performed is y hours, then the time y is divided by the total time x and multiplied by 100 to obtain the operating rate (%). The operating rate indicates the proportion of time that transfer operations can be performed relative to the total time, and the higher the operating rate, the longer the time that transfer operations can be performed.

[0021] On the Pacific coast, swells occur frequently throughout the year, and the operation rate is extremely low due to the effects of the swells. If the rocking of the hull of the transport barge 14 can be reduced so that crane work can be performed, the operation rate of ship-to-ship transfer work can be improved. For this reason, it is important to reduce the rocking of the hull of the transport barge 14.

[0022] The transport barge 14 will be described with reference to Fig. 3. Fig. 3(a) is a side view showing an example of the transport barge 14, and Fig. 3(b) is its plan view. The transport barge 14 is a box-shaped barge with a taper formed at the front and rear (bow and stern) of the hull and a large area in the horizontal direction, and has excellent loading capacity. The transport barge 14 can transport construction materials and the like loaded on its deck. The transport barge 14 may carry heavy machinery such as a crane vehicle, and may also be equipped with a winch used when mooring to a quay or the like, an anchor winch (windlass) for pulling up an anchor, and the like.

[0023] The transport barge 14 is a box-shaped barge with a large horizontal area, and therefore is subject to large rocking caused by waves. For this reason, when used for ship-to-ship transfer operations, it is necessary to moor it at multiple points with anchors or control the propellers installed on the bottom of the vessel by the DPS to maintain its position and reduce the rocking of the vessel as much as possible for crane operations. The transport barge 14 shown in FIG. 3 is equipped with horizontal thrusters 30 as a rotating propulsion means on the bottom of the vessel. The horizontal thrusters 30 can rotate 360°, and four of them are installed on the bottom of the vessel at predetermined positions in the front and rear of the vessel in the longitudinal direction. The transport barge 14 can control the direction and rotation speed of the propellers as the rotors of these four horizontal thrusters 30, move the vessel in a predetermined direction, and reduce rocking caused by waves. The number of horizontal thrusters 30 per one transport barge 14 is not limited to four.

[0024] The horizontal thrusters 30 have a high effect of reducing the rocking of the transport barge 14 in the horizontal direction, but have no effect in the vertical direction.

[0025] Therefore, a vertical motion reduction device is installed on the transport barge 14, and the vertical motion reduction device reduces the vertical motion of the transport barge 14 caused by waves. That is, the transport barge 14 is equipped with a DPS and a vertical motion reduction device, and after the horizontal motion is reduced by the DPS, the vertical motion reduction device reduces the vertical motion.

[0026] The vertical motion reduction device aims to improve the operating rate of ship-to-ship transfer operations, and therefore does not aim to reduce the vertical motion of the entire transport barge 14, but rather aims to reduce the vertical motion limited to the location of the suspended load (part of the hull). In order to achieve such a reduction in vertical motion limited to a specific location, the vertical motion reduction device includes a vertical thruster 40 as thrust generating means for generating a thrust in the vertical direction, which is installed in the water so as to protrude from the outer hull (side of the hull) of the transport barge 14, or in a position where there is no problem even if a tugboat approaches the transport barge 14 by devising the hull shape, or installed so that the installation location can be changed, such as by moving to the bottom of the ship when docking, as shown in Figure 4.

[0027] The vertical thruster 40 includes a prime mover and a conversion means having a plurality of blades that converts the rotational force output from the prime mover into thrust. The conversion means having a plurality of blades is, for example, a propeller. The vertical thruster 40 may use a fixed pitch propeller in which the angle of the propeller blades relative to the vertical direction (blade angle or propeller pitch) is fixed, or a variable pitch propeller in which the propeller pitch is variable. When reversing the direction in which thrust is generated with a fixed pitch propeller, it is usually necessary to reverse the rotation direction of the propeller. Note that with a fixed pitch propeller, it is also possible to change and control the magnitude of thrust by simply increasing or decreasing the rotation speed by α (n±α>0) while rotating the propeller at a certain constant rotation speed n (rpm) and generating a certain thrust.

[0028] In contrast, a controllable pitch propeller can generate any magnitude of thrust steplessly over the entire range from downward to upward simply by changing the pitch of the blades. Therefore, when a controllable pitch propeller is used, the controller 43 keeps the rotation direction and speed constant and controls the blade pitch to control the direction and magnitude of the thrust generated.

[0029] When constructing a new transport barge 14, the shape of the barge may be modified so that the vertical thruster 40 is installed in a location that will not get in the way when the barge is docked. The vertical thruster 40 may be located as close as possible to the side wall of the ship, or may be located a little away.

[0030] The vertical motion of a ship's hull varies greatly due to the mutual influence of the up and down movement of the ship's center of gravity (centre) and the rotational motion of the ship. Pitching is predominant in longitudinal waves with a wave direction of 0° from bow to stern, while roll is predominant in transverse waves with a wave direction of 90° from starboard (the right side facing the bow) to port (the opposite side), or from port to starboard. Therefore, it is believed that the vertical motion of a ship's hull can be reduced by reducing the rotational motion of the ship caused by the pitching and rolling of the ship.

[0031] The rolling motion of the hull can be reduced by providing fins that extend from bow to stern and protrude from both the port and starboard sides of the hull. This reduces the vertical motion of the entire hull. If the goal is to improve the availability of ship-to-ship transfer operations, it is sufficient to reduce the vertical motion only in the area of ​​the hoisted load.

[0032] As shown in Fig. 4, when the location of the hoisted load is on the deck on one side (for example, the port side) of the outer side of the transport barge 14 and approximately the center position in the longitudinal direction of the transport barge 14, at least one vertical thruster 40 with propeller blades facing in the up and down direction can be provided on the outer side of the transport barge 14 in order to reduce rotational motion at the location of the hoisted load. In the example shown in Fig. 4, four vertical thrusters 40 are provided on both the bow and stern sides of the transport barge 14, on both the port chord and starboard sides. The up and down motion of the transport barge 14 is controlled, including the rotational motion (rotational movement) of the hull, by controlling the up and down thrust generated by the four vertical thrusters 40.

[0033] Here, control for reducing the vertical movement of the transport barge 14 will be described with reference to Fig. 5 and Fig. 6. If the X-axis is taken along the longitudinal direction (length direction) of the transport barge 14, the Y-axis is taken along the lateral direction (width direction) of the transport barge 14, and the Z-axis is taken along the vertical direction (height direction or ocean depth direction) passing through the point where the X-axis and the Y-axis intersect, the rotation φ of the hull around the X-axis is called roll, the rotation θ of the hull around the Y-axis is called pitch, and the rotation ψ of the hull around the Z-axis is called yaw. Furthermore, the forward and backward movement X in the X-axis direction is called surge, the left and right movement Y in the Y-axis direction is called sway, and the vertical movement Z in the Z-axis direction is called heave.

[0034] The horizontal movements of surge and sway, as well as yaw, are controlled by the horizontal thrusters 30. The vertical thrusters 40 control the rotational movements of the vessel, pitch and roll.

[0035] Specifically, as shown in Fig. 6, when the hull is viewed from the bow side, the hull is a substantial rectangle whose center is the center of gravity G, the direction passing through the center of gravity G from port to starboard is the Y axis direction, and the vertical direction perpendicular to the Y axis direction is the Z axis direction. The X axis direction is the direction from the stern side to the bow side above the center of gravity G.

[0036] For example, when a clockwise rotational motion occurs in the hull around the X-axis, the port side descends and the starboard side ascends. In order to return the hull to the horizontal state before the rotational motion occurred, a control is required to raise the lowered port side and lower the raised starboard side, that is, a control to roll counterclockwise as shown in FIG. 6. Such a control can be realized, for example, by activating only the vertical thruster 40a provided on the port side to generate a thrust in the upward direction toward the sea surface. Alternatively, only the vertical thruster 40b provided on the starboard side may be activated to generate a thrust in the downward direction toward the seabed. Furthermore, the vertical thruster 40a may be activated to generate a thrust in the upward direction, and the vertical thruster 40b may also be activated to generate a thrust in the downward direction.

[0037] As shown in Fig. 6, when the thrusts generated by the left and right vertical thrusters 40a, 40b are directed in opposite directions, they are converted into energy that rotates around the X-axis at the center of gravity G of the hull (roll energy). When the thrusts generated by the left and right vertical thrusters 40a, 40b are the same and directed in the same direction, they are converted into energy that moves in the vertical direction (heave energy). When the thrusts generated by the left and right vertical thrusters 40a, 40b are different and directed in the same direction, they are converted into energy that rotates around the X-axis and energy that moves in the vertical direction.

[0038] Incidentally, when there is a suspended load on the port side, the transport barge 14 is arranged with its port side close to the SEP vessel 10. In this case, if the vertical thruster 40 is installed on the port side, it may interfere with crane work or cause damage due to contact between the hulls. For this reason, instead of providing the vertical thrusters 40 at four locations on the port and starboard sides of the bow and stern of the transport barge 14 as shown in FIG. 4, the vertical thrusters 40 may be provided at two locations on the bow and stern of the starboard side (upper side in the drawing) opposite the port side where the suspended load is located, as shown in FIG. 7(a). The vertical thrusters 40 do not have to be provided at two locations on the starboard side, and may be provided at one location or three or more locations on the starboard side.

[0039] Incidentally, even if the vertical thruster 40 is installed at only one location on the outer hull, it is possible to suppress the rotational motion of the hull, and as a result, it is possible to suppress the up and down movement of the hull at each position.

[0040] For existing transport barges 14, the vertical thrusters 40 may be installed anywhere on the outer hull as long as the vertical thrusters 40 can be installed later, and taking into account the position of the suspended load, one or more vertical thrusters 40 may be installed on the side opposite the side where the suspended load is located.

[0041] When constructing a new transport barge 14, the hull may be recessed into a substantially rectangular or semicircular shape as viewed from above to allow the vertical thrusters 40 to rotate, as shown in Fig. 7(b), to form a recess 50, and the vertical thrusters 40 may be installed in the recess 50 to eliminate inconvenience during construction. The recess 50 may be formed anywhere on the hull. The number of recesses 50 may correspond to the number of vertical thrusters 40 to be installed.

[0042] 4 again, the location of the suspended load is not always the same. For this reason, it is necessary to control the thrust generated by each vertical thruster 40 according to the location of the suspended load.

[0043] The vertical motion reduction device includes one or more vertical thrusters 40, a sensor 41 as a first detection means for detecting pitching and rolling at the center of gravity of the hull, a sensor 42 as a second detection means for detecting vertical motion at a predetermined position of the hull, and a controller 43 as a control means for controlling the thrust generated by the one or more vertical thrusters 40.

[0044] The sensors 41, 42 are displacement sensors, speed sensors, acceleration sensors, etc. The sensors 41, 42 may be used in combination with a positioning device such as a global positioning system (GPS). The sensors 41, 42 may be installed one each at the center of gravity position and the location of the suspended load, or one sensor may be moved for each measurement. The sensor 42 may be one sensor that is moved according to the location of the suspended load, or multiple sensors may be installed in advance and the sensor that obtains the detection results may be switched according to the location of the suspended load.

[0045] The controller 43 includes a processor, a memory, and the like, and controls the magnitude and direction of the thrust generated by the vertical thruster 40 based on the detection results of the sensors 41 and 42. The sensors 41 and 42 and the controller 43 may be connected to each other so as to be able to communicate with each other either by wire or wirelessly.

[0046] The controller 43 controls the magnitude and direction of the thrust generated by the vertical thruster 40 by changing the rotation direction and rotation speed of the propeller for the vertical thruster 40 so as to eliminate the vertical movement of the location of the suspended load. The vertical thruster 40 offsets the vertical movement of a predetermined position with the generated thrust, thereby reducing the vertical movement of the predetermined position.

[0047] The thrust of the vertical thruster 40 is converted into thrust with low efficiency of rotational energy near the sea surface, so the vertical thruster 40 needs to be installed at a predetermined depth from the sea surface. However, even if the thrust of the vertical thruster 40 is not controlled in both directions, but only in the upward direction where thrust is easily obtained near the water surface, the rotational movement can be controlled and the vertical movement of each position of the hull can be suppressed by installing the vertical thruster 40 at two or more positions. From this, it is not necessarily impossible to control by installing the vertical thruster 40 near the sea surface, but in order to perform stable control, it is desirable to install the vertical thruster 40 at a predetermined depth from the sea surface. The predetermined depth can be, for example, a depth of 1 m or more from the sea surface, where the vertical thruster 40 is not exposed to the sea surface.

[0048] Incidentally, instead of the vertical thruster 40, it is also possible to use a metal flat plate (submerged horizontal plate) of a predetermined thickness that can move in the vertical direction, and move the submerged horizontal plate up and down using an actuator or the like to offset the up and down movement of a predetermined position on the hull and reduce the up and down movement at that predetermined position.

[0049] A brief description of control when using a submerged horizontal plate will be given. The approximate center position on the port side of the ship's hull is taken as position P. If a load is placed at position P and position P attempts to displace in the sinking direction, the ship's hull rotates about its center of gravity G. If the approximate center position on the starboard side, which is the opposite side of position P, is taken as position S, position S attempts to displace upward due to this rotation. The upward displacement is suppressed simply by installing the submerged horizontal plate, but in order to suppress this displacement, the controller moves the submerged horizontal plate downward, suppresses position S from floating up, and suppresses the displacement of position P in the sinking direction. If position P attempts to displace in the floating up direction, the controller controls the submerged horizontal plate to move upward instead. Even if the location of the suspended load is not approximately the center position on the port side, the vertical movement of the location of the suspended load can be reduced by controlling the amount and speed of the vertical movement of the submerged horizontal plate.

[0050] There is a correlation between the size of the submerged horizontal plate and the energy required for control (the performance of the actuator), and by changing the size of the submerged horizontal plate and the performance of the actuator, it can be used in a variety of forms.

[0051] The vertical motion reduction device can be either one that uses a vertical thruster 40 or one that uses a submerged horizontal plate. In order to determine whether they have the same degree of effectiveness or which has a more advantageous effect, an analytical model was constructed and a numerical analysis was performed.

[0052] Fig. 8 is a diagram showing an example of an analytical model for performing a numerical analysis when vertical thrusters 40 are installed at four positions on the transport barge 14. Fig. 9 is a diagram showing an example of an analytical model for performing a numerical analysis when submerged horizontal plates 60 are installed at four positions on the transport barge 14. The transport barge 14 is a box-shaped ship with a total length of 110 m in the longitudinal direction, a maximum width of 32 m in the transverse direction, and a height of 7 m from the uppermost deck to the lowermost ship bottom.

[0053] The vertical thrusters 40 and the submerged horizontal board 60 are installed at four locations in total: two locations on the port and starboard sides on the bow side of the hull of the transport barge 14 (the distance from the bow to the center position of the vertical thrusters 40 and the submerged horizontal board 60 is 20 m from the bow), and two locations on the port and starboard sides on the stern side of the hull (the distance from the stern to the center position of the vertical thrusters 40 and the submerged horizontal board 60 is 20 m from the stern). The submerged horizontal board 60 is a flat plate 10 m long and 2 m wide.

[0054] The direction of the waves is the Y-axis direction, which is 90° when the X-axis direction is 0°, for example, from starboard to port. The control position is the position where the suspended load is located, for example, approximately the center position on the port side of the hull.

[0055] Figure 10 shows an example of the mean significant wave height and mean significant period on the Japan Sea side, and Figure 11 shows an example of the mean significant wave height and mean significant period on the Pacific side. Successive waves are observed one by one at an observation point, 1 / 3 of the total are selected in order from the highest wave height, and their wave heights and periods are averaged to obtain the significant wave height and significant period.

[0056] The mean significant wave height and mean significant period on the Japan Sea side are the monthly averages calculated from wave observation data measured at four locations: off the coast of Akita Prefecture, Akita Port, off the coast of Yamagata Prefecture, and Sakata Port over a five-year period from 2015 to 2019. Figure 10(a) shows the mean significant wave height for each month, and Figure 10(b) shows the mean significant period for each month.

[0057] The mean significant wave height and mean significant period on the Pacific side are the monthly averages calculated from wave observation data measured at four locations: offshore northern Iwate, Kuji Port, offshore Fukushima Prefecture, and Onahama Port over a five-year period from 2015 to 2019. Figure 11(a) shows the mean significant wave height for each month, and Figure 11(b) shows the mean significant period for each month.

[0058] On the Sea of ​​Japan side, the monthly average significant wave height is less than 1m only for the five months from May to September, making it a period when the waves are calm and suitable for ship-to-ship transfer operations. The monthly average significant period at this time is less than 5.5 seconds (s). For the seven months from January to April and October to December, the monthly average significant wave height exceeds 1m, reaching a maximum of 2.5m, and the monthly average significant period is approximately 5.5 to 7.4 seconds.

[0059] On the other hand, on the Pacific side, the monthly average significant wave height is approximately 1 to 2 m throughout the year from January to December, and the monthly average significant period is approximately 6.4 to 9.2 seconds.

[0060] Therefore, by setting the monthly average significant period to, for example, 6 seconds and performing a numerical analysis, it is possible to determine whether the vertical movement can be sufficiently reduced by control using the vertical thruster 40 or the submerged horizontal plate 60 during the period from May to September on the Japan Sea side. In addition, since the maximum monthly average significant period is approximately 9.2 seconds, by setting the monthly average significant period to, for example, 10 seconds or more and performing a numerical analysis, it is possible to determine whether the vertical movement can be sufficiently reduced by control using the vertical thruster 40 or the submerged horizontal plate 60 during all months on the Pacific Ocean side, including the Japan Sea side.

[0061] Fig. 12 shows the results of a numerical analysis of control using the submerged horizontal plates 60, with the monthly average significant period set to 6 seconds. Fig. 12(a) shows the relationship between the elapsed time t (sec) and the vibration characteristics δ1 to δ4 (m) in the up and down direction of the four submerged horizontal plates 60, when feedback control is performed using the proportional gain used in proportional control (P control) and the differential gain used in differential control (D control) for the deviation between the output value indicating the position of the submerged horizontal plate 60 output by the controller 43 performing proportional-differential (PD) control and the target value. Here, the proportional gain (P gain) is set to 30, and the differential gain (D gain) is set to 1.5.

[0062] Figure 12(b) is a diagram showing the relationship between elapsed time t (sec) and heave (m), which indicates the vertical oscillation characteristics at the center of gravity of the vessel with and without control by the submerged horizontal plate 60. The waves are the same with and without control, and the control force of the submerged horizontal plate 60 alone is not enough to change the vertical oscillation of the entire transport barge 14, so the two waveforms overlap.

[0063] Figure 12(c) is a diagram showing the relationship between elapsed time t (sec) and the vertical displacement (m) of the port center position, i.e., the controlled position where there is a suspended load, with and without control using the submerged horizontal plate 60. Without control, the port center position is displaced significantly up and down, from about -2.3 to about +2.3 m. On the other hand, with control, the port center position is displaced up and down, from about -0.2 to about +0.2 m, and the vertical displacement is reduced. This shows that control using the submerged horizontal plate 60 can reduce the vertical movement of the controlled position where there is a suspended load.

[0064] Fig. 12(d) is a diagram showing the relationship between elapsed time t (sec) and roll (deg), which indicates the rolling characteristics at the ship's center of gravity position with and without control by the submerged horizontal plate 60. Without control, the ship rotates in a range of about -9 to +9 degrees, and the rotational movement is large. On the other hand, with control, the ship rotates in a range of about -2.5 to +2.5 degrees, and the rotational movement is small. This shows that the roll can be controlled to suppress up-and-down movement.

[0065] Fig. 13 shows the results of a numerical analysis of control using submerged horizontal plates 60, with the monthly average significant period set to 12 seconds, which is greater than 10 seconds. Fig. 13(a) shows the relationship between the elapsed time t (sec) and the vibration characteristics δ1 to δ4 (m) in the heave direction of the four submerged horizontal plates 60, and Fig. 13(b) shows the relationship between the elapsed time t (sec) and the heave (m) indicating the heave characteristics at the center of gravity of the ship with and without control using the submerged horizontal plates 60. In Figs. 13(a) and (b), the significant period is doubled compared to Figs. 12(a) and (b), and therefore the deviation δ and the heave are also larger.

[0066] Figure 13(c) is a graph showing the relationship between elapsed time t (sec) and the vertical displacement (m) at the center of the port side with and without control by the submerged horizontal plate 60, and Figure 13(d) is a graph showing the relationship between elapsed time t (sec) and roll (deg), which indicates the lateral sway characteristics at the center of gravity of the vessel with and without control by the submerged horizontal plate 60.

[0067] In Figure 13(c), without control, the port center position displaces up and down from approximately -1.1 to +1.1 m, and with control, the port center position displaces up and down from approximately -0.8 to +0.8 m, with the vertical movement being slightly reduced.

[0068] In Fig. 13(d), without control, the rotation is in the range of about -2 to +2 degrees, while with control, the rotation is in the range of about -4 to +4 degrees, with the rotational movement being larger with control. This is because an attempt is made to suppress the vertical movement. In the case of a long significant period of 12 seconds, unlike the case of a short significant period of 6 seconds, the vertical movement is only slightly suppressed even with control, and it can be seen that the control effect of the submerged horizontal plate 60 is small.

[0069] Therefore, control using the submerged horizontal plate 60 is effective only during the period from May to September on the Japan Sea side when the waves are calm and suitable for ship-to-ship transfer operations.

[0070] Fig. 14 shows the results of a numerical analysis of control using the vertical thrusters 40, with the monthly average significant period set to 6 seconds. Fig. 14(a) shows the relationship between elapsed time t (sec) and the vibration characteristics Ft1 to Ft4 (kN) in the heave direction of the four vertical thrusters 40, and Fig. 14(b) shows the relationship between elapsed time t (sec) and the heave (m) indicating the heave characteristics at the center of gravity of the vessel with and without control by the vertical thrusters 40.

[0071] 14(a) shows the relationship between the elapsed time t (sec) and the vibration characteristics Ft1 to Ft4 (kN) in the heave direction of the four vertical thrusters 40 when feedback control is performed using the proportional gain used in proportional control (P control) and the differential gain used in differential control (D control) for the deviation between the output value indicating the thrust by the vertical thrusters 40 output by the controller 43 performing proportional-differential (PD) control and the target value. Here, the proportional gain (P gain) is set to 600,000 and the differential gain (D gain) is set to 800,000.

[0072] The heave shown in FIG. 14(b) is in the range of about -0.5 to about +0.5 m even when controlled by the vertical thruster 40, as in the case of control by the submerged horizontal plate 60 shown in FIG. 12(b).

[0073] FIG. 14(c) is a graph showing the relationship between elapsed time t (sec) and the vertical displacement (m) of the port center position with and without control by the vertical thruster 40, and FIG. 14(d) is a graph showing the relationship between elapsed time t (sec) and roll (deg) with and without control by the vertical thruster 40.

[0074] In Fig. 14(c), in the case of no control, the port center position is displaced significantly up and down, from about -2.3 to about +2.3 m, as in the case of control by the submerged horizontal plate 60 shown in Fig. 12(c). On the other hand, in the case of control, the port center position is displaced up and down, from about -0.2 to about +0.2 m, as in the case of control by the submerged horizontal plate 60 shown in Fig. 12(c). From this, it can be seen that the up and down movement of the position of the suspended load can be reduced even with control by the vertical thruster 40.

[0075] In Fig. 14(d), in the case of no control, the rotation is in the range of about -8 to about +8 degrees, and the rotational movement is large, as in the case of control by the submerged horizontal plate 60 shown in Fig. 12(d). On the other hand, in the case of control, the rotation is in the range of about -2 to about +2 degrees, and the rotational movement is small, as in the case of control by the submerged horizontal plate 60 shown in Fig. 12(d). From this, it can be seen that the up and down movement can be suppressed by controlling the roll.

[0076] FIG. 15 shows the results of a numerical analysis of the control using the vertical thruster 40 with the monthly average significant period set to 12 seconds, which is 10 seconds or more. FIG. 14(a) shows the relationship between the elapsed time t (sec) and the vibration characteristics Ft1 to Ft4 (kN) in the heave direction of the vertical thruster 40, and FIG. 14(b) shows the relationship between the elapsed time t (sec) and the heave (m) with and without control by the vertical thruster 40. FIG. 15(b) shows that the significant period is doubled compared to FIG. 14(b), and therefore the heave is also larger. Note that the vibration characteristics Ft in the heave direction have almost the same deviation of about -20 to about +20 kN because the gains are changed from the result shown in FIG. 14(a) with a P gain of 300,000 and a D gain of 600,000.

[0077] Figure 15(c) is a diagram showing the relationship between elapsed time t (sec) and the port center position (m) with and without control by the vertical thruster 40. Without control, the port center position displaces up and down from approximately -1.1 to +1.1 m, while with control, the port center position displaces up and down from approximately -0.4 to +0.4 m, and unlike the case of control by the submerged horizontal plate 60 shown in Figure 12(c), the vertical movement is greatly reduced.

[0078] Fig. 15(d) is a diagram showing the relationship between elapsed time t (sec) and roll (deg) with and without control by the vertical thruster 40. Without control, the roll is in the range of about -2 to +2°, and with control, the roll is in the range of about -2.5 to +2.5°, and as in the case of control by the submerged horizontal plate 60 shown in Fig. 12(d), the vertical movement is suppressed by increasing the rotational movement. Thus, with control by the vertical thruster 40, the vertical movement and rotational movement can be reduced even with a long significant period of 12 seconds, and it is clear that the control is effective.

[0079] From the above, in the case of short-period waves with a significant period of 6 seconds, both the vertical thruster 40 and the submerged horizontal plate 60 can provide good control effects. With the submerged horizontal plate 60, when the significant period is 12 seconds, practically no control effect can be obtained even if the submerged horizontal plate 60 is moved up and down to an extent that cannot be fully controlled. This is considered to be due to the fact that, for example, with the same amplitude, the fluid force (vertical thrust acting on the hull) obtained when the submerged horizontal plate 60 is moved up and down is less easily converted into fluid force energy as the period becomes longer.

[0080] On the other hand, the vertical thruster 40 can effectively control even long-period waves with a significant period of 12 seconds. Therefore, control by the vertical thruster 40 can sufficiently reduce vertical motion not only during the period from May to September on the Sea of ​​Japan side when the waves are calm and suitable for ship-to-ship transfer operations, but also during the periods from January to April and October to December on the Sea of ​​Japan side, and also during the periods from January to December on the Pacific side. As a result, ship-to-ship transfer operations can be performed on both the Sea of ​​Japan side and the Pacific side throughout the year, improving the operating rate.

[0081] Control using the vertical thrusters 40 is basically the same as control using the submerged horizontal plate 60, which controls the vertical movement of each hull position, which is caused by the coupling of the vertical and rotational movements of the hull, by the phase difference of the rotational movement.When controlling the vertical movement as well, this control can be achieved by installing vertical thrusters 40 in multiple locations.

[0082] 16 is a flow chart showing an example of the operation of reducing vertical motion by the vertical motion reduction device. The operation of reducing vertical motion by the vertical motion reduction device starts from step 100 (S100) when the transport barge 14 arrives at the target sea area, the propeller installed on the bottom of the vessel is controlled by the DPS, and the horizontal position is maintained.

[0083] In step 101 (S101), the sensor 41 detects the pitching and rolling of the transport barge 14 at the center of gravity. This is because it is impossible to control the rotation without knowing what kind of rotational motion is occurring in the hull of the transport barge 14. In addition, the sensor 42 detects the up and down movement at a predetermined position where the suspended load is located.

[0084] The up and down movement of the hull of the transport barge 14 at a predetermined position where the suspended load is located can be detected (calculated) by detecting the up and down movement, pitching, and rolling of the hull at the center of gravity. Therefore, the up and down movement at the predetermined position may be grasped by measuring the up and down movement, pitching, and rolling of the hull at the center of gravity.

[0085] In step 102 (S102), the controller 43 acquires the detection result of the sensor 41 from the sensor 41 as a first detection result, acquires the detection result of the sensor 42 from the sensor 42 as a second detection result, calculates the rotation direction and rotation speed of the propeller of the vertical thruster 40 based on the first detection result and the second detection result, notifies the vertical thruster 40 of the rotation direction and rotation speed of the propeller, and commands control. In step 103 (S103), the vertical thruster 40 adjusts the rotation direction and rotation speed of the propeller based on the command from the controller 43, and generates thrust in the vertical direction of the hull. This controls the hull to reduce the vertical movement.

[0086] In step 104 (S104), it is determined whether the transfer work has been completed, and if not, the process returns to step 101 (S101) and control of the vertical movement continues. On the other hand, if the transfer work has been completed, the process proceeds to step 105 (S105) and control of the vertical movement ends. The transport barge 14 can be switched from the operation of maintaining the horizontal position by the DPS to the operation of moving to the next work site, quay, etc., and can start moving.

[0087] The control shown in FIG. 16 is an example of PD control in which the vertical movement of a specific position on the hull is detected and only the detection results are used. However, control in the operation of reducing vertical movement is not limited to PD control.

[0088] By providing a first detection means for detecting pitching and rolling of the hull in addition to a second detection means for detecting the vertical movement of a predetermined position where a suspended load is located, it is possible to reduce the vertical movement of the hull, including the vertical movement of the center of gravity of the hull. The center of gravity of the hull changes slightly up and down due to pitching and rolling, because the metacenter position, which is the center of the hull's inclination, is the center of rotation. For this reason, it is desirable to be able to control and reduce the vertical movement of the center of gravity of the hull as well. The vertical movement of the predetermined position where a suspended load is located can be detected by detecting the vertical movement, pitching, and rolling of the center of gravity of the hull, as described above. In other words, the vertical movement of the center of gravity of the hull can be detected by detecting the vertical movement of the predetermined position where a suspended load is located, and the vertical and rolling of the center of gravity of the hull.

[0089] Therefore, by detecting the vertical movement of a predetermined position where a suspended load is located with the first detection means and detecting the pitch and roll of the hull's center of gravity with the second detection means, the vertical movement of the hull's center of gravity can be grasped and control can be performed to reduce the grasped vertical movement of the hull's center of gravity. A specific example of control of the vertical movement of the hull's center of gravity is control in which vertical thrusters 40 installed on the left and right sides of the center of gravity generate thrust in the opposite phase (opposite side) to the oscillation of the center of gravity. Note that this control is just one example and is not limited to this control.

[0090] The vertical motion reduction device, work vessel, and vertical motion reduction method of the present invention have been described in detail above with reference to the embodiments shown in the drawings. However, the present invention is not limited to the above-described embodiments, and can be modified within the scope of what a person skilled in the art can conceive, such as other embodiments, additions, modifications, deletions, etc., and any aspect is within the scope of the present invention as long as it achieves the functions and effects of the present invention. [Explanation of symbols]

[0091] 10…SEP ship 11…Barge 12...Lifting legs 13…Crane 14...Transport barge 15…Tower 16...Wind turbine components 20...Elevating crane ship 21...Jacket Basics 22...Pile 30…Horizontal thruster 40, 40a, 40b...Vertical thrusters 41, 42…Sensor 43…Controller 50…Recess 60...Horizontal board

Claims

1. A vertical motion reduction device for a work vessel, comprising: One or more thrust generating means arranged in the water outside the work vessel and generating thrust in the vertical direction of the work vessel; a first detection means for detecting pitching and rolling at the center of gravity of the work vessel; A second detection means for detecting vertical movement of the work vessel at a predetermined position; a control means for controlling a vertical thrust generated by each of the one or more thrust generating means based on detection results of the first detection means and the second detection means; A vertical motion reducing device comprising:

2. The vertical motion reducing device according to claim 1 , wherein the one or more thrust generating means are installed on only one side of the outer hull of the work vessel.

3. the thrust generating means includes a prime mover and a conversion means having a plurality of blades for converting a rotational force output from the prime mover into thrust; The vertical motion reducing device according to claim 1 or 2, wherein the control means controls a rotation direction and a rotation speed of the plurality of blades.

4. the thrust generating means includes a prime mover and a conversion means having a plurality of blades for converting a rotational force output from the prime mover into thrust; The conversion means is capable of changing an angle of the plurality of blades with respect to the vertical direction, The vertical motion reducing device according to claim 1 or 2, wherein the control means controls at least angles of the plurality of blades.

5. The vertical motion reducing device according to claim 1 or 2, wherein the work vessel has one or more recesses for accommodating each of the one or more thrust generating means.

6. A work boat equipped with a vertical motion reduction device, The vertical motion reducing device is One or more thrust generating means arranged in the water outside the work vessel and generating thrust in the vertical direction of the work vessel; a first detection means for detecting pitching and rolling at the center of gravity of the work vessel; A second detection means for detecting vertical movement of the work vessel at a predetermined position; a control means for controlling a vertical thrust generated by each of the one or more thrust generating means based on detection results of the first detection means and the second detection means; Including, work boats.

7. The work vessel includes one or more propulsion means on the outer side or bottom or both of the work vessel for moving the work vessel horizontally; 7. The work vessel of claim 6, wherein the one or more propulsion means maintain a horizontal position of the work vessel.

8. 8. A work vessel according to claim 6 or 7, wherein the one or more thrust generating means are installed on only one side of the outer hull of the work vessel.

9. A method for reducing vertical motion of a work vessel, comprising: detecting pitching and rolling at the center of gravity of the work vessel by a first detection means, and detecting up and down movement of the work vessel at a predetermined position by a second detection means; a step of controlling a vertical thrust generated by each of one or more thrust generating means disposed in the water outside the work vessel by a control means based on the detection results of the first detection means and the second detection means; A method comprising:

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