Damping device, damping system, vessel equipped with damping system and damping method

Abstract

A damping device includes a cable to be connected to a mass; a winch for hauling in and paying out the cable; a measurement system for measuring a cable motion relative to the winch and for measuring a cable tension in the cable; a control system for damping cable motion by driving the winch in dependency of the measured cable motion and the measured cable tension; a sheave to guide the cable from the winch to the mass, wherein the measurement system is configured to measure the cable tension by measuring a magnitude of a load on the sheave caused by the cable tension.

Claims

1. A damping device, comprising: a cable to be connected to a mass; a winch for hauling in and paying out the cable; a measurement system for measuring a cable motion relative to the winch and for measuring a cable tension in the cable; a control system for damping cable motion by driving the winch in dependency of the measured cable motion and the measured cable tension; and a sheave to guide the cable from the winch to the mass, wherein the measurement system is configured to measure the cable tension by measuring a magnitude of a load on the sheave caused by the cable tension, wherein the control system comprises a damping mode in which a desired cable tension applied in the cable by the control system is dependent on the measured cable motion, and wherein the control system also comprises a non-damping mode in which the desired cable tension is independent of the measured cable motion, and wherein the control system is operable to switch between the damping mode and the non-damping mode.

2. The damping device according to claim 1, wherein the control system is configured to apply the desired cable tension in the cable by driving the winch based on the measured cable tension.

3. The damping device according to claim 1, wherein in the damping mode of the control system, the control system is configured such that, in case the cable is paid out by the winch, the desired cable tension in the cable is higher than in case the cable is hauled in by the winch.

4. The damping device according to claim 1, wherein the measurement system is configured to measure the cable motion relative to the winch by measuring the cable speed.

5. The damping device according to claim 1, wherein the measurement system is configured to measure the cable motion relative to the winch by measuring motion of the sheave caused by the cable motion.

6. The damping device according to claim 5, wherein the measurement system is configured to measure the motion of the sheave by measuring a rotational speed of the sheave.

7. The damping device according to claim 5, wherein the measurement system comprises a sensor to measure the motion of the sheave, which sensor is an encoder type sensor.

8. The damping device according to claim 1, wherein the control system in the damping mode is configured to automatically switch to the non-damping mode when the cable tension drops below a predetermined minimum value.

9. A damping system comprising: a first damping device; and a second damping device, wherein each of the first damping device and the second damping device comprises: a cable to be connected to a mass; a winch for hauling in and paying out the cable; a measurement system for measuring a cable motion relative to the winch and for measuring a cable tension in the cable; a control system for damping cable motion by driving the winch in dependency of the measured cable motion and the measured cable tension; and a sheave to guide the cable from the winch to the mass, wherein the measurement system is configured to measure the cable tension by measuring a magnitude of a load on the sheave caused by the cable tension, and wherein the control system is configured to apply a desired cable tension in the cable by driving the winch based on the measured cable tension, and wherein the damping system further comprises a yaw control system configured to adapt the desired cable tension in the cables of the first and second damping devices based on a difference between the measured cable motion of the cable of the first damping device and the measured cable motion of the cable of the second damping device in order to minimize said difference between the measured cable motion in the cables of the first and second damping devices.

10. A vessel comprising the damping system according to claim 9.

11. The vessel according to claim 10, further including a mass, wherein the mass and the damping system are configured to be connected to each other via one or more cables of the damping system.

12. The vessel according to claim 11, wherein the mass and the cables of the first and second damping device are configured to be connected to the mass at distinct locations which are at least spaced apart in horizontal direction.

13. The vessel according to claim 10, wherein the vessel further comprises a crane including a hoisting cable to be connected to the mass in order to handle the mass.

14. A method to damp motion of a moveable mass, said method comprising the following steps: connecting a first cable to the mass, such that the first cable is guided from a first winch to the mass by a first sheave; connecting a second cable to the mass, such that the second cable is guided from a second winch to the mass by a second sheave, and such that the first and second cable are connected to the mass at distinct locations which are at least spaced apart in horizontal direction; measuring cable motion of the first cable relative to the first winch; measuring cable motion of the second cable relative to the second winch; measuring cable tension in the first cable by measuring a magnitude of a load on the first sheave caused by the cable tension; measuring cable tension in the second cable by measuring a magnitude of a load on the second sheave caused by the cable tension; damping motion of the first cable by driving the first winch in dependency of the measured cable motion of the first cable and the measured cable tension in the first cable; and damping motion of the second cable by driving the second winch in dependency of the measured cable motion of the second cable and the measured cable tension in the second cable.

15. The method according to claim 14, wherein the step of damping motion of the first cable includes applying a desired cable tension in the first cable by driving the first winch based on the measured cable tension in the first cable, wherein the desired cable tension is dependent on the measured cable motion of the first cable, and wherein the desired cable tension is higher in case the first cable is paid out by the first winch than in case the first cable is hauled in by the first winch.

16. The method according to claim 15, wherein the step of damping motion of the second cable includes applying a desired cable tension in the second cable by driving the second winch based on the measured cable tension in the second cable, wherein the desired cable tension is dependent on the measured cable motion of the second cable, and wherein the desired cable tension is higher in case the second cable is paid out by the second winch than in case the second cable is hauled in by the second winch.

17. The method according to claim 16, wherein the method also includes the following steps: comparing the measured cable motion of the first cable with the measured cable motion of the second cable; determining a difference between the measured cable motions of the first and second cable; adapting the desired cable tensions in the first and second cable based on the determined difference in order to minimize said difference.

Description

(1) The invention will now be described in a non-limiting way by reference to the accompanying drawings in which like parts are indicated by like reference symbols, and in which:

(2) FIG. 1 depicts a vessel according to an embodiment of the invention;

(3) FIG. 2 depicts schematically a damping system provided on the vessel of FIG. 1;

(4) FIG. 3 depicts in more detail a control system for use in the damping system of FIG. 2;

(5) FIG. 4 depicts a top view of a vessel according to another embodiment of the invention; and

(6) FIG. 5 depicts schematically a damping system provided on the vessel of FIG. 4.

(7) FIG. 1 depicts schematically a vessel VE according to an embodiment of the invention. The vessel VE includes a hull HU and a crane CR arranged on the hull. The crane CR comprises a hoisting cable HC, which in the shown configuration, holds a mass M. Hauling in and paying out of the hoisting cable by an appropriate winch (not shown) allows to respectively lift and lower the mass M by the crane as indicated by arrow A1. As the operation of the crane is generally known and not relevant for describing the invention, the crane CR will not be described in more detail.

(8) Movement of the vessel VE, as e.g. indicated by arrow A2, which may be caused by wind, waves and/or currents, may cause the mass M to swing relative to the crane CR and hull HU as indicated by arrow A3. In order to damp motion of the mass M relative to the vessel, a damping system including a damping device DD is provided on the vessel. The damping device DD is partially shown in FIG. 1, schematically in FIG. 2, and FIG. 3 depicts in more detail a part thereof.

(9) The damping device DD comprises a cable C connected to the mass M. The cable C is wound on a winch drum WD which can be rotated by a motor MO connected thereto. The combination of winch drum WD and motor MO will be referred to as winch W. Rotation of the winch drum by the motor MO allows to haul in or pay out the cable C as indicated by arrow A4.

(10) The cable C is guided by a sheave SH which is rotatable about a sheave rotation axis RA defined in this embodiment by a pin P and corresponding bearings (not shown). The sheave SH interacts with the cable C in such a manner that motion of the cable C will result in rotation of the sheave SH and tension in the cable C will result in loads applied to the sheave SH and thus to the pin P and bearings of the sheave SH.

(11) The damping device DD according to the embodiment of FIGS. 1 and 2 comprises a measurement system for measuring a cable motion of the cable C relative to the winch and for measuring a cable tension in the cable C. In FIG. 2, the measurement system comprises a sensor S1 measuring the loads applied to the pin P, thereby measuring a magnitude of a load on the sheave SG caused by the cable tension allowing to determine the cable tension in the cable C.

(12) Alternatively or additionally, the measurement system may comprise sensors measuring the cable tension more directly, e.g. by using strain gauges on the cable or on the part connecting the cable to the mass.

(13) The measurement system further comprises a sensor S2 measuring motion of the sheave SH caused by motion of the cable C, for instance by measuring the rotational speed of the sheave SH, e.g. using an incremental encoder type of sensor.

(14) The measured cable motion and the measured cable tension are input to a control system CS configured to drive the winch W in dependency of the measured cable motion and the measured cable tension in order to damp the cable motion. Driving the winch is carried out by providing a drive signal DS to the motor MO. Motor MO can e.g. be an electric motor, but can also be a hydraulic motor.

(15) FIG. 3 depicts in more detail an embodiment of the control system CS of FIG. 2. Input to the control system are a signal CM representative for the cable motion of the cable C, and a signal CT representative for the cable tension in the cable C. The signal CM is converted into a desired cable tension DCT by a motion to tension converter MTC. The desired cable tension DCT is compared to the actually measured cable tension CT, and the difference between the two is fed to a controller CO which, based on the desired cable tension and the measured cable tension, outputs a drive signal DS to the motor MO of the winch in order to apply the desired cable tension in the cable C.

(16) The signals inputted to the control system may in an embodiment be processed first by a processing unit. An example thereof is illustrated by a processing unit DB shown in dashed lines for processing the cable tension signal CT. A similar processing unit may be provided for the cable motion signal CM. The processing unit may amongst others filter and/or convert the signal into a signal suitable to be processed further by the control system.

(17) The motion to tension converter MTC may be configured to output a desired cable tension DCT which is dependent on the measured cable motion. When the mass is moving towards the damping device, the desired cable tension may be lower than in case the mass is moving away from the damping device. In other words, the desired cable tension is higher in case the cable is paid out than in case the cable is hauled in. A minimum cable tension is preferably always desired as this prevents a slack cable.

(18) The above configuration of the control system may be referred to as damping mode. However, the control system may also comprise a non-damping mode. In this non-damping mode, the desired cable tension is constant and thus independent of the cable motion. The non-damping mode may be implemented in the motion to tension converter which in the damping mode operates as described above, but in the non-damping mode is set to output a constant desired tension independent of the input to the motion to tension converter MTC.

(19) FIG. 4 depicts a top view of a part of a vessel according to another embodiment of the invention. Shown are a mass M which is suspended from a hoisting cable HC as in FIG. 1. Due to vessel motions, e.g. roll of the vessel, the mass may start to swing back and forth as indicated by arrow A3. However, it is also possible that the mass M starts to rotate about a vertical axis parallel to the hoisting cable as indicated by arrow A5. For instance due to yaw of the vessel. In order to damp motions of the mass M, a damping system is provided comprising a first damping device FDD and a second damping device SDD.

(20) The first and second damping device are both a damping device similar to the damping device shown in relation to FIGS. 1-3. Hence, the first damping device comprises a first cable FC connected to a first winch FW and guided from the first winch to the mass by a first sheave FS. The second damping device in turn comprises a second cable SC connected to a second winch SW and guided from the second winch to the mass by a second sheave SS.

(21) The first damping device further comprises a first measurement system FMS for measuring a cable motion of the first cable FC relative to the first winch FW and for measuring a cable tension in the first cable, and a first control system FCS for damping cable motion of the first cable FC by driving the first winch in dependency of the measured cable motion of the first cable and the measured cable tension in the first cable.

(22) The second damping device further comprises a second measurement system SMS for measuring a cable motion of the second cable SC relative to the second winch SW and for measuring a cable tension in the second cable, and a second control system SCS for damping cable motion of the second cable SC by driving the second winch in dependency of the measured cable motion of the second cable and the measured cable tension in the second cable.

(23) The first and second control system FCS, SCS are interconnected via a yaw control system as is shown in FIG. 5, but omitted in FIG. 4 for clarity reasons.

(24) FIG. 5 depicts in more detail the damping system of FIG. 4. The first damping device of the damping system includes a first winch with a first winch drum FWD which is driven by a first motor FMO. Also shown are the first sheave FS guiding the first cable FC from the first winch to the mass. Similarly, the second damping device of the damping system includes a second winch with a second winch drum SWD which is driven by a second motor SMO. Also shown are the second sheave SS guiding the second cable SC from the second winch to the mass.

(25) The first damping device FDD further comprises a first measurement system FMS including a first tension sensor FS1 for measuring a magnitude of the loads applied to the first sheave FS to determine the cable tension in the first cable FC, and including a first motion sensor FS2 for measuring a motion of the first cable FC.

(26) The second damping device further comprises a second measurement system SMS including a second tension sensor SS1 for measuring a magnitude of the loads applied to the second sheave SS to determine the cable tension in the second cable SC, and including a second motion sensor SS2 for measuring a motion of the second cable SC.

(27) The signal FCM representative for the motion of the first cable is inputted to a first motion to tension converter FMTC of a first control system FCS to provide a desired cable tension for the first cable which is dependent on the measured cable motion of the first cable, and is inputted to a yaw control system YCS.

(28) The signal SCM representative for the motion of the second cable is inputted to a second motion to tension converter SMTC of a second control system SCS to provide a desired cable tension for the second cable which is dependent on the measured cable motion of the second cable, and is inputted to the yaw control system YCS.

(29) The yaw control system YCS compares the measured cable motion of the first cable with the measured cable motion of the second cable. The difference between said two measured cable motions is representative for motion of the mass about the hoisting cable indicated by arrow A5 in FIG. 4.

(30) The yaw control system YCS comprises a difference to tension converter DTC to determine a tension compensation value TCV that is added to the desired cable tension in the first control system and subtracted from the desired cable tension in the second control system.

(31) In both control systems FCS, SCS the adapted desired cable tension is compared to the measured cable tension, and the difference therebetween is inputted to a respective controller FCO and SCO which provides a respective drive signal FDS and SDS to the corresponding motors FMO and SMO of the winches FW and SW.

(32) Hence, when there is a difference between the cable motions of the first and second cable, the desired cable tensions as applied by the first and second control system are different and counteract the difference between the cable motions of the first and second cable thereby damping the rotation of the mass M about the hoisting cable HC.

(33) It will be apparent to the skilled person in the art of damping systems that the invention is not limited to the examples shown above and that many other embodiments and alternatives also fall within the scope of the invention.