Mooring cable tension monitoring system

Abstract

A mooring cable tension monitoring system (1) according to one embodiment is a system for monitoring the tension of a mooring cable (10) that is erected on at least one mooring fitting (22) on a hull (21) and that is caught at the tip end to a bollard (31) of a fixed structure (3), the system comprising a mooring machine (4) that includes a reel around which the mooring cable (10) is wound; and a control device (9). The control device (9) calculates the reel-side tension (P) of the mooring cable (10), determines a tension attenuation rate (R) generated when the mooring cable (10) is erected on at least one mooring fitting (22), and calculates the bollard-side tension (P0) of the mooring cable (10) by multiplying the reel-side tension (P) by the tension attenuation rate (R) or dividing the reel-side tension (P) by the tension attenuation rate (R).

Description

Technical Field

[0001] The present disclosure relates to a mooring line tension monitoring system. Background Art

[0002] When a ship is moored to a fixed structure such as a quay or offshore base, a mooring cable is installed on at least one mooring metal member on the hull and the tip of the mooring cable is tied to the mooring post of the fixed structure. The mooring cable is wound or unwound by a mooring machine (motor winch) installed on the hull.

[0003] When mooring a ship, it is desirable to monitor the tension of the mooring cable because the tension of the mooring cable changes due to tide level, load, wind, tidal current, etc. For example, Patent Document 1 describes a mooring machine including: a drum on which a mooring cable is wound; and a band brake which switches between a restrained state in which the drum is prohibited from rotating and an open state in which the drum is allowed to rotate. When the band brake is in the restrained state, the tension of the mooring cable is calculated based on the detection value of a load sensor provided on the band brake and the tension action radius on the drum.

[0004] Furthermore, Patent Document 2 describes using a fiber rope as a mooring line, twisting an elongation sensor into the tip end of the fiber rope, and calculating the tension of the mooring line based on the detection value of the elongation sensor.

[0005] Prior art literature: Patent Literature: Patent Document 1: Japanese Patent Application Publication No. 2002-211478 Patent Document 2: International Publication No. 2020 / 110902 Summary of the invention

[0006] Problems to be solved by the invention: As described in Patent Document 1, when the tension of the mooring cable is calculated based on the detection value of the load sensor provided on the band brake and the tension acting radius on the drum, the calculated tension is the tension of the portion of the mooring cable near the drum. As described above, since the mooring cable is installed on at least one mooring metal fitting on the hull, the tension of the mooring cable is different before and after the mooring metal fitting. That is, in the structure described in Patent Document 1, the tension of the portion between the mooring metal fitting and the bollard in the mooring cable, i.e., the bollard side tension, which is the most important part, cannot be detected.

[0007] On the other hand, in the structure described in Patent Document 2, although the tension on the bollard side of the mooring cable can be detected, it is necessary to twist the elongation sensor into the fiber rope.

[0008] Therefore, an object of the present disclosure is to provide a mooring line tension monitoring system capable of detecting the bollard-side tension of a mooring line without using an elongation sensor.

[0009] Means of solving the problem: The present invention provides a mooring cable tension monitoring system, which is a system for monitoring the tension of a mooring cable, wherein the mooring cable is installed on at least one mooring metal fitting on a ship body and the tip end of the mooring cable is tied to a mooring post of a fixed structure, the system comprising: a mooring machine including a drum wound with the mooring cable; and a control device, which calculates the tension of the portion of the mooring cable between the mooring machine and the at least one mooring metal fitting, namely, the drum-side tension, and determines the tension attenuation rate caused by the installation of the mooring cable on the at least one mooring metal fitting, and calculates the tension of the portion of the mooring cable between the at least one mooring metal fitting and the mooring post, namely, the bollard-side tension, by multiplying the drum-side tension by the tension attenuation rate and dividing the drum-side tension by the tension attenuation rate.

[0010] Effect of the invention: According to the present disclosure, there is provided a mooring line tension monitoring system capable of detecting the bollard-side tension of a mooring line without using an elongation sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic structural diagram of a mooring line tension monitoring system according to an embodiment; Figure 2 This is the front view of the mooring machine; Figure 3 This is a schematic diagram of the structure of a band brake. DETAILED DESCRIPTION

[0012] Figure 1 1 shows a mooring line tension monitoring system 1 according to one embodiment. The mooring line tension monitoring system 1 monitors the tension of the mooring line 10 when the ship 2 is moored to a fixed structure 3 such as a quay or an offshore base by the mooring line 10 .

[0013] Specifically, the mooring cable tension monitoring system 1 includes: a plurality of mooring machines 4, which are provided on the hull 21 of the ship 2; and a control device 9, which controls these mooring machines 4. Each mooring machine 4 reels in and unreels the corresponding mooring cable 10. In the present embodiment, four mooring machines 4 are arranged on the port and starboard sides of the bow side and the port and starboard sides of the stern side, but the number and position of the mooring machines 4 can be appropriately changed.

[0014] A plurality of mooring metal parts 22 are provided on the hull 21, and a plurality of mooring posts 31 are provided on the fixed structure 3. When mooring, each mooring cable 10 is installed on at least one mooring metal part 22, and the tip of the mooring cable 10 is tied to the mooring post 31. Figure 1 In the embodiment, all the mooring cables 10 are installed on two mooring metal fittings 22 , but the number of mooring metal fittings 22 installed on each mooring cable 10 may be one or more than three.

[0015] The mooring metal parts 22 are, for example, stand rollers, fairleads, deck rollers, chocks, etc. The mooring posts 31 are, for example, bitts, bollards, and quick release hooks, etc. The mooring cable 10 can be a fiber rope or a metal wire. Examples of the material of the fiber rope include nylon and ultra-high molecular weight polyethylene (HMPE). The mooring cable 10 can also be a fiber rope at the tip portion, with the remaining majority being made of metal wire.

[0016] like Figure 2 As shown, each mooring machine 4 includes: a drum 7, which is wound with a mooring rope 10; and a motor 51, which rotates the drum 7. Figure 2 In order to simplify the drawings, the mooring rope 10 is omitted. The drum 7 is rotatably supported by the support 25. In this embodiment, a speed reducer 52 is provided between the motor 51 and the drum 7, and a clutch 53 and a band brake 6 are provided between the speed reducer 52 and the drum 7. That is, the motor 51 rotates the drum 7 via the speed reducer 52 and the clutch 53.

[0017] The motor 51 rotates in a first direction in which the mooring cable 10 is wound onto the drum 7 and in a second direction in which the mooring cable 10 is unwound from the drum 7. In the present embodiment, the motor 51 is a hydraulic motor, and the hydraulic oil is supplied to and discharged from the hydraulic motor via the control valve 55. The control valve 55 is controlled by the control device 9, thereby switching the motor 51 between stopping, rotating in the first direction, and rotating in the second direction. However, the motor 51 may also be an electric motor, which is directly controlled by the control device 9.

[0018] In addition, the motor 51 is provided with a torque detector 50 for detecting the torque of the motor 51. In the present embodiment, the motor 51 is a hydraulic motor, and therefore a pressure sensor for measuring the inflow pressure of the working oil supplied to the hydraulic motor is used as the torque detector 50, and the inflow pressure measured by the pressure sensor is converted into the torque of the motor 51. However, a torque sensor for directly measuring the torque of the motor 51 may be used instead of the pressure sensor. Alternatively, in the case where the motor 51 is an electric motor, the current flowing to the electric motor may be converted into the torque.

[0019] The clutch 53 switches between an engaged state in which the reel 7 is connected to the speed reducer 52 and a disengaged state in which the reel 7 is separated from the speed reducer 52. In the present embodiment, the clutch 53 includes a hydraulic cylinder. The hydraulic cylinder is connected to an electromagnetic valve 81, and the electromagnetic valve 81 is controlled by the control device 9, thereby switching the clutch 53 from the engaged state to the disengaged state or vice versa. However, the clutch 53 may also include an electric cylinder instead of the hydraulic cylinder, and the electric cylinder is directly controlled by the control device 9.

[0020] The band brake 6 switches between a restrained state that prohibits the reel 7 from rotating and an open state that allows the reel 7 to rotate. Figure 3 As shown, the band brake 6 includes a hydraulic cylinder 66. The hydraulic cylinder 66 and the solenoid valve 82 (refer to Figure 2 ) is connected, and the electromagnetic valve 82 is controlled by the control device 9, thereby the band brake 6 is switched from the restrained state to the open state or vice versa. However, it is also possible that the band brake 6 includes an electric cylinder instead of the hydraulic cylinder 66, and the electric cylinder is directly controlled by the control device 9.

[0021] In more detail, the band brake 6 includes a brake drum 61 that rotates together with the spool 7 and a pair of arc-shaped bands 62 and 63 along the brake drum 61. One ends of the bands 62 and 63 are connected via a pin 64, and the other ends of the bands 62 and 63 are connected to the above-mentioned hydraulic cylinder 66 via a link mechanism 65. When the hydraulic cylinder 66 moves the other ends of the bands 62 and 63 away from each other via the link mechanism 65, a small gap is formed between the bands 62 and 63 and the brake drum 61, and the band brake 6 is in an open state. On the contrary, when the hydraulic cylinder 66 moves the other ends of the bands 62 and 63 closer to each other via the link mechanism 65, the bands 62 and 63 tighten the brake drum 61, and the band brake 6 is in a restrained state.

[0022] The band brake 6 is provided with a load cell 60 for detecting the belt tension F acting on the belts 62 and 63 in the restrained state. In the present embodiment, a pin-type load cell 60 is used. The link mechanism 65 includes a tension bar 67 connected to the bracket 23 provided on the hull 21 via the load cell 60.

[0023] The control device 9 inputs an operation signal for each mooring machine 4. Based on the input operation signal, the control device 9 controls the control valve 55 and the electromagnetic valves 81 and 82 of the corresponding mooring machine 4. For example, the control valve 55 includes an operating lever so that the crew can manually operate the mooring machine 4, and when the operating lever is tilted, an operation signal corresponding to the tilting direction is input to the control device 9. Alternatively, in the case of automatic ship operation, the control device 9 may generate an operation signal by itself.

[0024] Regarding the control device 9, the functions of the elements disclosed in this specification can be performed using a circuit or processing circuit including a general-purpose processor, a special-purpose processor, an integrated circuit, an ASIC (Application Specific Integrated Circuits), an existing circuit, and / or a combination thereof, which is constructed or programmed to perform the disclosed functions. The processor includes transistors and other circuits, so it can be regarded as a processing circuit or circuit. In the present disclosure, a circuit, unit, or means is hardware that performs the listed functions, or hardware that is programmed to perform the exemplified functions. The hardware may be the hardware disclosed in this specification, or it may be other known hardware that is programmed or constructed to perform the listed functions. When the hardware is a processor that is considered to be a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to constitute the hardware and / or processor.

[0025] Furthermore, the control device 9 is electrically connected to the torque detector 50 and the load sensor 60. In the present embodiment, the control device 9 is also electrically connected to the roll number detector 70 and two cameras 91 (see Figure 1 The winding number detector 70 detects the number of windings of the mooring cable 10 on the drum 7. For example, the winding number detector 70 converts the position of the outermost peripheral surface of the mooring cable 10 wound on the drum 7 into the number of windings.

[0026] One of the two cameras 91 captures an area including two mooring cranes 4 arranged on the bow side and all mooring cables 10 extending from these mooring cranes 4 where all mooring metal parts 22 may be installed, while the other camera 91 captures an area including two mooring cranes 4 arranged on the stern side and all mooring cables 10 extending from these mooring cranes 4 where all mooring metal parts 22 may be installed.

[0027] The control device 9 calculates the tension of the portion between the mooring metal fitting 22 and the bollard 31 in each mooring cable 10 , that is, the bollard side tension P0 , based on the detection results of the torque detector 50 , the load sensor 60 , and the number of windings detector 70 and the image of the camera 91 .

[0028] First, the control device 9 calculates the tension of the portion between the mooring machine 4 and the mooring metal fitting 22 in each mooring cable 10, that is, the drum side tension P. Specifically, when the band brake 6 is in the open state, the control device 9 calculates the drum side tension P based on the torque T of the motor 51 detected by the torque detector 50 and the number of windings N detected by the winding number detector 70. For example, the control device 9 calculates the drum side tension P using the following mathematical formula (1).

[0029] [Mathematical formula 1] , r: reduction ratio of reducer 52 [-] ηW: Mechanical efficiency of mooring machine 4 [-] dR: Diameter of mooring cable 10 [mm] dD: diameter of the drum 7 [mm].

[0030] On the other hand, when the band brake 6 is in the restrained state, the control device 9 calculates the reel side tension P based on the band tension F detected by the load sensor 60 and the number of layers N detected by the number of layers detector 70. For example, the control device 9 calculates the reel side tension P using the following mathematical formula (2).

[0031] [Mathematical formula 2] , L: horizontal distance from the center of the reel 7 to the load sensor 60 [mm].

[0032] Next, the control device 9 determines, for each mooring cable 10 , a tension reduction rate R generated when the mooring cable 10 is installed on the mooring fitting 22 . To determine the tension reduction rate R, the image of the camera 91 is used.

[0033] The control device 9 determines which mooring metal fitting 22 each mooring cable 10 is installed on and the winding angle of the mooring cable 10 relative to each mooring metal fitting 22 based on the image captured by the camera 91. Then, the control device 9 calculates the individual attenuation rate Ri for each mooring metal fitting 22 where each mooring cable 10 is installed. In addition, "i" refers to the number of the mooring metal fitting 22 where one mooring cable 10 is installed. For example, the control device 9 calculates the individual attenuation rate Ri using the following mathematical formula (3).

[0034] [Mathematical formula 3] , μi: Friction coefficient associated with the i-th mooring metal component 22 θi: The winding angle of the mooring cable 10 relative to the i-th mooring metal member 22 That is, the individual attenuation rate Ri of the i-th mooring metal fitting 22 is calculated using the friction coefficient μi and the winding angle θi.

[0035] The friction coefficient μi is a coefficient corresponding to the type of the i-th mooring metal fitting 22 and the type of the mooring cable 10 installed at the i-th mooring metal fitting 22. The control device 9 pre-stores a friction coefficient table that specifies the correspondence between the type of the mooring metal fitting 22 and the type (material and diameter) of the mooring cable 10 and the friction coefficient. The control device 9 uses the friction coefficient table to determine the friction coefficient μi of the i-th mooring metal fitting 22 based on the pre-stored type of the mooring cable 10 and the image of the camera 91. For example, the friction coefficient table when the mooring metal fitting 22 is a bearing seat is shown in Table 1.

[0036] [Table 1] .

[0037] The control device 9, when there is only one mooring metal fitting 22 installed on the mooring cable 10, determines the individual attenuation rate Ri of the mooring metal fitting 22 as the tension attenuation rate R generated by installing the mooring cable 10 on the mooring metal fitting 22. When there are multiple mooring metal fittings 22 installed on the mooring cable 10, the control device 9 multiplies the individual attenuation rates Ri of the mooring metal fittings 22 and determines the multiplied value as the tension attenuation rate R generated by installing the mooring cable 10 on the mooring metal fittings 22. That is, the control device 9 determines the tension attenuation rate R of the entire mooring cable 10 using the following mathematical formula (4).

[0038] [Formula 4] , n: the total number of mooring metal parts 22 installed on one mooring line 10.

[0039] Then, the control device 9 calculates the bollard side tension P0 (P0=P×R) by multiplying the drum side tension P by the tension decay rate R when the mooring cable 10 is wound onto the drum 7, and calculates the bollard side tension P0 (P0=P÷R) by dividing the drum side tension P by the tension decay rate R when the mooring cable 10 is unwound from the drum 7 or when the drum 7 stops. Therefore, the bollard side tension P0 when the mooring cable is wound and the bollard side tension P0 when the mooring cable is unwound or when the drum stops can be calculated simply by switching whether to multiply or divide the drum side tension P by the tension decay rate R.

[0040] As described above, in the mooring cable tension monitoring system 1 of the present embodiment, the drum-side tension P is converted into the bollard-side tension P0 using the tension decay rate R. Therefore, the bollard-side tension P0 of the mooring cable 10 can be detected without using an elongation sensor.

[0041] Furthermore, in the present embodiment, since the tension reduction rate R is determined using the mathematical formula (4), the tension reduction rate R of the entire mooring cable 10 can be calculated simply by calculating the individual reduction rate Ri of each mooring metal fitting 22 .

[0042] Furthermore, since the individual attenuation rate Ri of each mooring metal fitting 22 is calculated using the friction coefficient μi and the winding angle θi, the individual attenuation rate Ri can be calculated using the same mathematical formula.

[0043] (Variation) The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the present invention.

[0044] For example, a separate drum including a storage drum and a tension drum may be used as the drum 7 instead of using the winding number detector 70. When mooring, the mooring cable 10 is wound around the tension drum, and the radius from the center of the drum 7 to the line of action of the tension is constant. However, in this case, when mooring, the mooring cable 10 needs to be wound around the tension drum. In contrast, if the winding number detector 70 detects the winding number of the mooring cable 10 on the drum 7, special operations when mooring are not required, as in the case of using a separate drum.

[0045] In addition, depending on the ship 2, the mooring metal fittings 22 where the mooring cable 10 is installed may be predetermined. In this case, the winding angles of the mooring cable 10 relative to each mooring metal fitting 22 other than the mooring metal fitting 22 located near the outline of the ship 2 may be stored in advance in the control device 9 without requiring the camera 91.

[0046] In addition, the control device 9 may calculate the winding angle of the mooring cable 10 relative to the mooring metal fitting 22 located near the outline of the ship 2, in other words, the mooring metal fitting 22 located closest to the mooring post 31 among the mooring metal fittings 22 on which the mooring cable 10 is installed, based on the GPS information (latitude and longitude) of the ship 2 and the terrain information of the fixed structure 3 (including the latitude and longitude of the mooring post 31) pre-stored in the control device 9.

[0047] (Summarize) As a first aspect, the present disclosure provides a mooring cable tension monitoring system, which is a system for monitoring the tension of a mooring cable, wherein the mooring cable is installed on at least one mooring metal fitting on a hull and the tip end is tied to a mooring post of a fixed structure, the system comprising: a mooring machine including a drum wound with the mooring cable; and a control device, which calculates the tension of the portion of the mooring cable between the mooring machine and the at least one mooring metal fitting, i.e., the drum-side tension, and determines the tension attenuation rate caused by the installation of the mooring cable on the at least one mooring metal fitting, and calculates the tension of the portion of the mooring cable between the at least one mooring metal fitting and the mooring post, i.e., the bollard-side tension, by multiplying the drum-side tension by the tension attenuation rate or dividing the drum-side tension by the tension attenuation rate.

[0048] According to the above configuration, the tension on the drum side is converted into the tension on the bollard side using the tension decay rate. Therefore, the tension on the bollard side of the mooring cable can be detected without using an elongation sensor.

[0049] As a second aspect, in the first aspect, the at least one mooring metal fitting may include a plurality of mooring metal fittings, the control device may calculate individual attenuation rates for each of the plurality of mooring metal fittings, and determine the tension attenuation rate generated when the mooring cable is installed on the plurality of mooring metal fittings by multiplying the individual attenuation rates of the plurality of mooring metal fittings. According to this configuration, the tension attenuation rate of the entire mooring cable can be calculated only by calculating the individual attenuation rates of each mooring metal fitting.

[0050] As a third aspect, in the second aspect, the control device may calculate the individual attenuation rate using a friction coefficient corresponding to the types of the mooring cable and the mooring metal fitting and a winding angle of the mooring cable relative to the mooring metal fitting. According to this structure, the individual attenuation rate can be calculated using the same mathematical formula.

[0051] As a fourth aspect, in any one of the first to third aspects, the control device may calculate the bollard side tension by multiplying the drum side tension by the tension decay rate when the mooring cable is wound onto the drum, and calculate the bollard side tension by dividing the drum side tension by the tension decay rate when the mooring cable is unwound from the drum and when the drum stops. According to this configuration, the bollard side tension when the mooring cable is wound and the bollard side tension when the mooring cable is unwound and when the drum stops can be calculated simply by switching whether to multiply or divide the drum side tension by the tension decay rate.

[0052] As the fifth aspect, in any one of the first to fourth aspects, for example, the mooring machine includes: a motor that rotates the drum; and a belt brake that switches between a constraint state that prohibits the drum from rotating and an open state that allows the drum to rotate, and the control device calculates the drum side tension based on the torque of the motor when the belt brake is in the open state, and calculates the drum side tension based on the belt tension of the belt brake when the belt brake is in the constraint state.

Claims

1. A mooring cable tension monitoring system, characterized in that: It is a system for monitoring the tension of a mooring line, which is installed on at least one mooring metal piece on the hull and whose tip is tied to a mooring post of a fixed structure. The system has: a mooring machine, comprising a drum around which the mooring cable is wound; and A control device, which calculates the tension of the portion between the mooring machine and the at least one mooring metal member in the mooring cable, namely, the drum-side tension, and determines the tension attenuation rate caused by the mooring cable being installed on the at least one mooring metal member, and calculates the tension of the portion between the at least one mooring metal member and the bollard in the mooring cable, namely, the bollard-side tension, by multiplying the drum-side tension by the tension attenuation rate or dividing the drum-side tension by the tension attenuation rate.

2. The mooring line tension monitoring system according to claim 1, characterized in that: The at least one mooring metal member comprises a plurality of mooring metal members, The control device calculates individual attenuation rates for the plurality of mooring fittings, respectively, and determines the tension attenuation rate generated when the mooring cable is installed on the plurality of mooring fittings by multiplying the individual attenuation rates of the plurality of mooring fittings.

3. The mooring line tension monitoring system according to claim 2, characterized in that: The control device calculates the individual attenuation rate using a friction coefficient according to the types of the mooring cable and the mooring hardware and a winding angle of the mooring cable with respect to the mooring hardware.

4. The mooring line tension monitoring system according to any one of claims 1 to 3, characterized in that: The control device calculates the tension on the bollard side by multiplying the tension on the drum side by the tension decay rate when the mooring cable is wound onto the drum, and calculates the tension on the bollard side by dividing the tension on the drum side by the tension decay rate when the mooring cable is unwound from the drum and when the drum stops.

5. The mooring line tension monitoring system according to any one of claims 1 to 3, characterized in that: The mooring machine includes: a motor that rotates the drum; and a band brake that switches between a restrained state that prohibits the drum from rotating and an open state that allows the drum to rotate, The control device calculates the spool-side tension based on the torque of the motor when the band brake is in the released state, and calculates the spool-side tension based on the band tension of the band brake when the band brake is in the restricted state.

Images