WO2015105420A1

WO2015105420A1 - A vessel, a motion platform, a control system, a method for compensating motions of a vessel and a computer program product

Info

Publication number: WO2015105420A1
Application number: PCT/NL2015/050010
Authority: WO
Inventors: Jan Van Der Tempel; Jacob Christiaan JANSEN
Original assignee: Ampelmann Operations B.V.
Priority date: 2014-01-09
Filing date: 2015-01-08
Publication date: 2015-07-16
Also published as: NL2012069C2

Abstract

A vessel including a motion platform, which platform comprises: - at least one carrier for bearing, moving and/or transferring a load; - a gangway provided with a first end pivotably connected to the carrier and an opposite second end; - a multiple number of first actuators for moving the carrier relative to the vessel; - a control system arranged for driving the multiple number of first actuators, wherein a cable extends from the vessel and/or the motion platform to at least a position at or near the second end of the gangway, wherein the cable is provided with a connecting element at an end opposite the vessel and/or motion platform, for connecting to another vessel or structure, especially an off-shore structure, wherein the connecting element comprises at least a first prong for hooking over an element connected to the gangway and at least a second prong for hooking over a coupling element provided on the other vessel or structure.

Description

Title: A vessel, a motion platform, a control system, a method for compensating motions of a vessel and a computer program product

The invention relates to a vessel or an assembly for transferring people and/or loads between a vessel and a second vessel or structure. The invention further relates to a method for providing a gangway between a vessel and a second vessel or structure.

Such a vessel is e.g. known from the International patent publication WO 2007/120039. The vessel is provided with a motion platform which comprises a carrier borne by six hydraulic cylinders, and a movable gangway connected to the carrier for providing a connection between the carrier and another structure, such as an offshore

construction. During use, with the aid of sensors, the motions of the respective vessel are measured. With the aid of these measurements, the orientation of the hydraulic cylinders is driven continuously so that the carrier remains approximately stationary relative to the fixed world. In this manner, motions of the ship are compensated so that a transfer between the ship and the fixed world, or vice versa, is made possible.

WO87/02723 discloses a vessel with an articulated ramp, comprising a ramp section connected to a ship by means of a post, extending perpendicular to and rotatable around a first axis

perpendicular to a deck of the ship and pivotable relative to said post around a second axis perpendicular to said first axis. An outer ramp section is connected to the first section by an intermediate platform which is mechanically kept in a position parallel to the ship's deck. The outer section can pivot relative to the first section around a third axis parallel to the first axis and a fourth axis perpendicular to said third axis.

Actuators are provided, by means of hydraulic cylinders, to move the first and outer gangway sections relative to the ship and to an oil rig. Anchor lines extend below the ramp sections, from a set of constant tension winches in the post to a free end of the outer ramp section. The anchor lines extend through a ball joint fixedly connected to the outer ramp section by a rod, and through an anchor line stop fitting. The oil rig is provided with a mooring station for receiving the ball joint and the anchor line stop fitting, by sliding the anchor lines between the ball joint and the stop fitting into a slit in the mooring station and then pulling the anchor lines tight, such that the ball joint is pulled against a first side of the mooring station and the stop fitting to an opposite side of the mooring station. In order to bring the stop fitting with the anchor lines to the oil rig a pilot line is connected to the ends of the anchor lines extending beyond the stop fitting. The pilot line is then passed to the oil rig by a rig man on the ship, which pilot man is received by a rig man on the oil rig. The rig man on the oil rig then has to pull in the pilot line, to slide the anchor lines in said slit. Then the winches are activated for bringing the anchor lines under load and subsequently pull the ball joint into a fixed connection with the mooring station. In this known system there always has to be a rig man on the oil rig for coupling and uncoupling. In coupled condition the outer ramp section will rotate relative to the oil rig in six degrees of freedom around the ball joint, whereas all forces for

maintaining the coupled relationship are to be provided by the anchor cables extending through said ball joint and the stop fitting.

FR2465640 discloses a system for transferring persons and small cargo between a ship and an off shore structure, comprising a telescoping gangway carried by a platform on the ship. The platform allows passive rotation around an axis perpendicular to the ship's deck and limited pivoting of the platform around an axis substantially parallel to said deck. The gangway is pivotably connected to the platform by a further axis also extending substantially parallel to the deck. A hydraulic cylinder is provided between the platform and the first segment of the gangway connected to the platform, for compensating for part of the weight of the platform and for retracting the first segment of the gangway to a horizontal storage position. A cable extends below the gangway segments, tensioned by a constant tension winch provided below the first segment of the gangway, near the platform. A towing cable is provided between a free end of the gangway and a boom of the off shore structure. The boom is provided on a special platform of the structure, which allows the boom to pivot around a vertical axis over about 270 degrees. A winch is provided for tensioning the towing cable, either from the gangway or the structure. FR2465640 does not disclose how the towing cable is connected or disconnected from either the structure of the ship, and does not disclose how the towing cable is transferred between the ship and the structure, for coupling or decoupling. The end of the gangway is kept in close contact with the structure by maintaining the cables tensioned by means of the constant tension winches.

W098/57845 discloses a system for transferring personnel and small cargo between a vessel and an off shore structure, wherein the vessel is provided with a large and complicated transfer device,

comprising a telescoping gangway suspended from an articulated frame extending well above the gangway. Through the frame a pilot cable can be led for transferring a ball joint coupling element to a complementary ball joint coupling element provided on the off shore structure. In this structure the gangway is passive and operated by means of the frame. The ball joint coupling provides for limited rotational movements of the gangway relative to the off shore structure.

WO2006/013342 discloses a ship with a gangway for providing a connection between the ship and an off shore structure such as a windmill. To this end a runway is provided, fixed on the ship, over which a first end of the gangway can be guided, between a stored position on the ship and an extended position. Guide wires can be provided between the ship and the structure, over which guide wires the gangway can be guided to the structure. The gangway is thereby supported by the guide wires and the runway and its free end can be supported at the off shore structure. The cables are kept taut at all times during use and the first end will move over the run way in order to compensate for movement of the ship relative to the structure.

One of the objects of the invention is to improve a vessel including a motion platform.

Another object of the invention is to reduce manufacturing and/or operational costs of a motion platform.

At least one of these and other objects are achieved with a vessel, assembly, platform and/or method according to the present description.

In a first aspect this disclosure can be characterised by a motion compensation platform, which platform comprises at least one carrier for bearing, moving and/or transferring a load and a gangway provided with a first end pivotably connected to the carrier and an opposite second end. A multiple number of first actuators is provided for moving the carrier relative to the vessel, and a control system is arranged for driving the multiple number of first actuators. A cable extends from the vessel and/or the motion platform to at least a position at or near the second end of the gangway. During movement of the gangway to and/or from the structure the cable can in embodiments be carried by the gangway, for example at or near the second end thereof. The cable can be provided with a connecting element at an end opposite the vessel and/or motion platform, for connecting to another vessel or structure, especially an off-shore structure, wherein the connecting element comprises at least a first prong for hooking over an element connected to the gangway and at least a second prong for hooking over a coupling element provided on the other vessel or structure In a second aspect this disclosure can be characterised by an assembly of a vessel according to the invention and a mooring element, wherein the mooring element comprises a counter coupling element for coupling to the cable and/or to a coupling element connected to the cable.

In a third aspect this disclosure can be characterised by a motion platform, particularly but not exclusively suitable for a vessel as described, which platform comprises at least one carrier for bearing, moving and/or transferring a load, a gangway provided with a first end pivotably connected to the carrier and a second end for contacting a target area, a multiple number of first actuators for moving the carrier relative to the vessel. At least a second actuator is provided for moving the gangway relative to the carrier, whereas a control system is arranged for driving the multiple number of first actuators and for driving the at least one second actuator. A cable is provided which is or can be carried at or near the second end of the gangway. The cable will preferably at least be carried by the gangway during movement of the second end of the gangway towards or away from a second vessel or structure with which the cable is to be connected.

In a fourth aspect this disclosure relates to a method for providing a gangway between a first vessel and second vessel or a structure, such as an off-shore structure, wherein the gangway is carried at a first end by a motion platform on the vessel and has an opposite second end. Further a cable is provided, connected to the vessel and/or the platform, for example by a winch. The method comprises, but is not necessarily limited to the steps of:

moving the gangway by the platform, preferably in an active mode, such that the second end is brought to a position near or in contact with the second vessel or structure;

connecting the cable to the second vessel or structure; allowing the motion platform and/or gangway to follow the movements of the vessel relative to the movements of the second vessel or structure, especially by bringing the platform and/or gangway from an active mode into an inactive mode. The cable can be provided with a connecting element at an end opposite the vessel and/or motion platform, for connecting to another vessel or structure, especially an offshore structure. The method can comprise the steps of:

hooking at least a first prong of the connecting element over an element connected to the gangway;

- carrying the coupling element to a coupling element at the other vessel or structure;

hooking at least a second prong of the connecting element over the said coupling element provided on the other vessel or structure; releasing the first prong from the element connected to the gangway; and

moving a free end of the gangway towards the other vessel or structure.

In embodiments the cable is carried by the gangway to and from the structure, and is preferably released from the gangway once it is connected to both the vessel and the structure.

In clarification of the invention, exemplary embodiments of a vessel, motion platform, method and use according to the invention will be further elucidated with reference to the drawing. In the drawing:

Fig. 1 shows a schematic perspective view of a vessel according to the invention;

Fig. 2 shows a schematic diagram of the vessel shown in Fig. 1; Fig. 3 shows a schematic perspective of a motion platform according to the invention;

Fig. 4 shows a flow chart of an embodiment of a method according to the invention; Fig. 5A-K schematically a series of steps in providing and removing a gangway;

Fig. 6A-D schematically steps of an alternative embodiment;

Fig. 7 in top view schematically an embodiment of an assembly of the present invention; and

Fig. 8A - D disclose an embodiment of a coupling element and counter coupling element for coupling a cable.

In this description, identical or corresponding parts have identical or corresponding reference numerals. In the drawing,

embodiments are given only as examples. The parts used there are mentioned merely an as example and should not be construed to be limitative in any manner. Other parts too can be utilized within the framework of the present invention.

According to embodiments of the invention a gangway is or can be used for transferring a cable from a vessel to another vessel or structure, for providing a connection between the two. Then the cable and, optionally, the gangway and/or platform are used to keep the second end of the gangway, opposite the first end which is connected to the platform, in close proximity off and preferably in contact with the second vessel or structure.

In this description reference is made to for example second vessels, structures such as off shore structures and the like, with which a connection is to be made by a gangway of a vessel according to this disclosure. In this description second vessel and structure are

interchangeable, unless otherwise specified, and may both be referred to as structure 2.

In this description a gangway is to be understood as an element or assembly for transferring or allowing to transfer people, cargo, animals or other loads between a vessel and another vessel or structure, the gangway bridging at least part and preferably all of a gap or distance between the vessel and the second vessel or structure or at least a landing area thereof.

In this disclosure a cable has to be understood as any element which is known to be used or suitable for connecting a vessel to another vessel or structure, such as but not limited to metal, plastic or fibre cables, such as mooring cables or lines, chains, rods and the like. In this description second vessel or structure has to be understood as including but not limited to sea going vessels and ships, hulls, off-shore structures such as drilling platforms, windmills and the like, for example

permanently, semi-permanently or temporarily placed in and/or on open water.

In this description a Stewart platform is described as the basis for a motion platform, by way of example only. Other types of motion platforms can be used within the context of the invention too.

Figure 1 schematically shows an embodiment of a vessel 1 according to the invention. With this vessel 1, a load such as for instance people, animals, goods and/or other loads can be transferred from the vessel 1 to a target area, such as for example another, second vessel or a structure, such as for example an off-shore structure 2, and vice versa. The structure 2 can for example be a frame or base of, for instance, a windmill or platform at sea 3. For transfer, the vessel 1 is provided with a motion platform 4. This platform can be designed to compensate for motions of the vessel 1 relative to the structure 2, for the purpose of holding a part of the platform or connected elements contacting the structure 2 relatively still relative to the structure 2, so that for instance people such as windmill construction personnel can transfer relatively safely. The motions of the vessel 1 that can be compensated may comprise linear motions such as surge (vessel moves from front 1A to back IB), heave (up and down) and sway (sideways), and rotating motions such as roll (bow from left to right) yaw (the vessel 1 rolls from left to right) and pitch (bow up and down). Naturally, the motions of the vessel 1 are often combinations of these linear and rotational motions.

This transferring from or to the vessel 1 should of course not be understood as limited to the transfer from and/or to windmills 2. In principle, transferring can be carried out between the vessel 1 and any other surrounding structure or vessel 2. The vessel 1 is suited for transferring, for instance, people, animals and/or loads to, in principle, any offshore construction, such as platforms at sea 3 and/or other constructions in the water 3, etc. In certain embodiments, a vessel 1 according to the invention is designed for transferring to any part connected to the fixed world, such as a quay, a levee, cliffs, steep rocks, (sea)floor etc. In certain embodiments, a vessel 1 has been made suitable for transferring to other moving elements and/or floating elements, such as, for instance, other vessels. To that end, with the aid of, for instance, a camera, optical sensor or the like, the motions of such a moving element can be registered and be compensated by the active components of the platform.

In the embodiment shown, the motion compensation platform 4 is provided with a carrier 6 and a multiple number of first actuators, implemented as six hydraulic cylinders 5a, for moving the carrier. Such a motion platform 4 is for example known as simulation platform, as "Stewart" platform. The carrier 6 can be designed to be movable in six degrees of freedom. However, the carrier can also be designed to be movable in less degrees of freedom, e.g. three degrees of freedom, e.g. with respect to roll, yaw and pitch. The platform 4 further comprises a gangway 16 having a first end 16a and a second end 16b. The gangway first end 16a is pivotably connected to the carrier 6. Further, the gangway second end 16b, opposite the first end 16A is or can be brought into contact with the structure 2. The gangway 16 can be moved with respect to the carrier 6 by driving at least a second actuator 5b provided by the platform. In operation, during at least a certain period the second end 16b of the gangway 16 can be held substantially stationary relative to the windmill 2 by actively driving the multiple number of hydraulic cylinders 5a and the at least one second actuator. To that end, the platform is further provided in a known manner with motion sensors and a control system for appropriately driving the respective actuators.

Figure 3 shows a schematic perspective of a motion platform 4 according to the invention. The platform includes a framework or base 50 rigidly fixed to the vessel 1. The multiple number of first actuators 5 bear the carrier 6 on the framework 50. The carrier 6 is provided with a top surface 6 on which the gangway 16 is pivotably mounted via a pivot mechanism 25. Further, Fig. 3 shows the second actuator 5b enabling the second end 16b of the gangway 16 to be lifted and lowered with respect to the carrier 16. More specifically, the second actuator 5b is arranged for pivoting the gangway 16 with respect to a first pivoting axis A

substantially parallel to the carrier 6 and transverse with respect to a longitudinal axis L of the gangway 16. Thus, by pivoting the gangway 16 around the first pivoting axis A, the second end 16b of the gangway can be lifted or lowered to follow a target height of the target area 2.

The platform is further provided with another second actuator

(not shown) that is arranged for pivoting the gangway 16 with respect to a second pivoting axis B substantially transverse with respect to the plane wherein the carrier 6 extends, so that the gangway may swivel clockwise or counter-clockwise in a substantially horizontal plane or at least in a plane or parallel to a plane perpendicular to said axis B and/or substantially parallel to the plane of the carrier 6.

The gangway includes a first gangway section 26a and a second gangway section 26b mutually interconnected via a translation

mechanism 28. The first gangway end 16a is provided on the first gangway section 26a, while the second gangway end 16b is provided on the second gangway section 26b. The platform is further provided with a second actuator, e.g. integrated in the translation mechanism 28, for moving the second gangway section 26b with respect to the first gangway section 26a substantially along the gangway longitudinal axis L, so that the gangway second end 16b may follow a lateral, horizontal movement of the vessel with respect to the target area 2. The gangway 16 can thus be extended and retracted by means of the mechanism 28 and the relevant second actuator.

In embodiments by compensating a vessel movement via actively driving some or all second actuators 5b, a motion compensation in three degrees of freedom can be performed such that the carrier 6 has to compensate for the other three degrees only. In embodiments compensation, as far as necessary, can be performed in more than three, for example four, five or all of the six degrees of freedom by actively driving the first actuators.

It is noted that in another embodiment of the motion platform according to the invention, another design can be implemented, e.g.

having only two second actuators or only one second actuator for the gangway extension and retraction. Then, the carrier has to perform a motion compensation in more degrees of freedom, e.g. four degrees or five degrees of freedom.

Figure 1 and 2 show a cable 20, at a first end connected to the vessel 1 by a winch 21. In embodiment such winch can be a standard winch or can for example be an auto recovery winch, render and recovery winch or constant tension winch. An opposite second end of the cable is connected to the structure 22 by a coupling element 23, connected releasably to a counter coupling element 24 on the structure 2. The counter coupling element 24 can be formed by or part of a mooring element 25 as will be discussed. With the cable 20 the distance between the vessel and the structure can be defined, at least maximised, and/or controlled by defining the length X of the cable 20. The tension in the cable 20 can be adjusted and/or controlled, for example by the winch 21, and the cable 20 can be pulled taut.

In embodiments the gangway 16, especially the second end 16b thereof can be held by and/or pushed against the structure 2, for example against, into and/or onto a mooring element 25. In embodiments the gangway, especially the second end 16b can be kept in a relatively constant position relative to the structure 2, for example in, on and/or over the mooring element 25, as a result of the tension in the cable being controlled, especially kept taut and the platform 4 and/or the gangway 16 being controlled such that the end 16b of the gangway 16 is pushed against the mooring element 25. In such embodiment the platform 4 and/or gangway 16 can be controlled such that they only follow the movements of the vessel 1 in stead of compensating for the movements thereof relative to the structure or second vessel 2. In embodiments in which the gangway 16 has two or more parts 26A, B movable relative to each other in a length direction L of the gangway 16, such as for example shown in fig. 3, 5, 6 and 7, the second end 16B can be held in position relative to the structure or second vessel 2, especially relative to a mooring element 25 thereon, by extending and reducing the axial length of the gangway 16, by movements of the second part 26b relative to the first part 26a, and for example allowing the gangway to pivot freely around the first pivot axis A and/or second pivot axis B and/or for example by holding the platform in a fixed position or by allowing the platform to follow movements of the gangway substantially passively.

Substantially passively or not active can be understood in this context as including but not limited to allowing the platform, especially the carrier to follow movements of the first end of the gangway 16 by not actively controlling the pressure of the first actuators 5a, and/or by actuating the first actuators 5a only to such extend that the platform 4 does not pull the second end 16b away from the structure or second vessel 2. In

embodiments the cable 20 can be controlled such that the majority or even all of the movements of the vessel 1 relative to the structure or second vessel 2 can be compensated for by adjustments in the length of the gangway 16 between the first and second ends 16a, 16b and pivoting of the gangway 16 relative to the platform 4, especially the carrier, for example around the first and/or second axis A, B. Such pivoting can be free pivoting, e.g. without actuation by any second actuator, or can at least partly be controlled by at least one second actuator 5b. In all of these embodiments the first and/or second actuators 5a, 5b could be controlled to for example dampen movements of the parts of the platform and/or gangway relative to each other and/or relative to the vessel 1.

In embodiments a vessel, especially a platform 4 with a gangway 16 can be used in two modes: an active mode for transferring an end of the cable 20 and/or the second end of the gangway 16 from the vessel 1 to a structure or second vessel 2 to which a connection is to be made, and a second mode in which the platform is operated more passively than in active mode, and at least partly follows movement of the gangway and does not compensate for the movements of the vessel or at least compensates for movements of the vessel to a lesser extend than in active mode. In active mode at least the first actuators 5a and preferably also second actuators 5b can in embodiments be controlled actively, based on the sensor signals of sensors 7, as discussed with respect to and in the prior art as for example disclosed in WO 2007/120039 and/or

WO2012/021062, for actively compensating for movements of the vessel 1 and bringing and holding the second end 16b in a preferred position relative to the structure or second vessel 2. In passive mode the position of the second end 16b of the gangway is not controlled, or at least not only actively controlled by movements of the platform and/or actuation of the first and second actuators 5a, 5b, but at least partly effected by the fact that the vessel 1 is kept at a relatively fixed distance from the second vessel or structure 2 by the cable 20, such that the second end 16b of the gangway 16 can be kept substantially in a preferred position relative to the second vessel or structure 2 without the necessity of fully

compensating for the movements of the vessel 1 relative to the second vessel or structure 2. This allows for a far less complicated system to be used, which can for example have a lighter platform 4, smaller actuators 5, a smaller hydraulics or pneumatic or electrical system for driving the actuators and/or, less complicated sensors. In embodiments a vessel 1, assembly, or platform according to the description can moreover enhance safety, since even if the platform 4 is not actively controlled by the system, for example due to power failure, the second end 16a can be kept in close proximity of the second vessel or structure, for safe transfer of for example persons and/or cargo.

Figure 2 shows a schematic diagram of the vessel 1. The control system 8 is connected to the motion sensors 7 for receiving motion sensor data, for instance the rocking of the vessel 1 in the water 3. With the aid of these measurement data, during use, at least in active mode, a first driving signal and a second driving signal are generated for driving the hydraulic cylinders 5a and the at least one second actuator 5b,

respectively, for moving the carrier 6 with respect to the vessel 1 and for moving the gangway 16 with respect to the carrier 6, respectively, in order to bring and at least temporarily maintain the second end 16b of the gangway substantially stable relative to the target area. In order to generate the driving signals, the control system 8 is provided with processor 13. The control system also includes a memory 14. Processing these measurements and actively driving the hydraulic cylinders 5a and the at least one second actuator 5b is a task to be performed by the control system 8. The actuators 5a, 5b may include pneumatic and/or hydraulic means, linear motors, electric driving elements etc. In the embodiments shown in fig. 1, the pneumatic means 9 comprise at least one pneumatic cylinder 10 which is placed approximately in the centre of the motion compensation platform 4 and is connected via pipes 15 to a pressure compensator in the form of an accumulator 11 for buffering compressed air, and a compressor 12 for compressing air. After filling with

compressed air in the pneumatic cylinder 10 and the accumulator 11, after provision of a load, the cylinder 10 will remain pressurized and it can continue bearing at least a part of the load. The pneumatic cylinder 10 may have the property of passively moving along in its longitudinal direction. Motions of the carrier 6 in the longitudinal direction of the cylinder 10 are followed by compression and expansion of the air in the cylinder 10 and the accumulator 11. Small pressure losses in the pneumatic cylinder 10 through, for instance, friction can be measured and compensated with the aid of, for instance, the compressor 12 and/or the control system 8. Such pneumatic means 9 are known per se from the so- called 'heave compensation' systems. By placing this longitudinal direction in the direction of gravity, a great force, e.g. that of the weight of the carrier 6 and the load, will be continuously absorbed by the passive pneumatic means 9, and hence also in the case of a defect in the active elements of the motion compensation platform 4 such as, for instance, the sensors 7, the control system 8 and/or the hydraulic cylinders. In particular embodiments, the pneumatic means 9 are advantageously placed in other directions, for instance for compensating tilting motions of the carrier 6 after, for instance, a defect. In this way, upon a defect of an element such as a cylinder 5, the pneumatic means 9 can prevent the motion compensation platform from making a relatively unsafe motion, such as, for instance, collapsing. Defects that might occur are, for instance, power supply failure or valves in the active hydraulic system becoming wedged. Naturally, also, other, preferably passive, pressure systems 9 can be utilized within the framework of the invention. In certain embodiments, instead of and/or in addition to pneumatic means 8, that is the cylinder 10, at least one spring can be utilized as passive element 10, for instance a spiral and/or gas spring. The pneumatic means 9 can, in principle, comprise different types of pressure elements such as, for instance, hydraulic means and/or elastic means and/or a pulling element, etc. Naturally, one or more pressure elements can be utilized. Depending on, for instance, the expected use, desired precision and/or economic considerations, one particular type, one particular amount and/or positioning can be selected. A passive pressure system 9 provides security in that it will, in principle, not fail and can remain functional without continuous actuation. Also, such a passive system 9 can remain of limited complexity. In embodiments no such pneumatic means are provided or they are designed differently, for example hydraulic.

In particular embodiments, the motion sensors 7 comprise known motion sensors 7 such as for measuring motions of the vessel 1, for instance accelerometers or dynamometers. With known accelerometers, the motion of the vessel 1 relative to the fixed world can be measured. Also, in particular embodiments, other types of sensors 7 can be utilized, such as for instance cameras, GPS (Global Positioning System), sensors utilizing electromagnetic waves, sonic waves, etc. The sensors 7 may measure the position of the vessel 1 relative to one or more elements in the surrounding area, such as for instance towards another vessel 1 and/or the fixed world. The information the control system 8 receives from the motions sensors 7 is processed via, for instance, pre-programmed algorithms so that the actuators 5a, 5b can be driven for holding the second end 16b of the gangway 16 approximately stationary relative to the target area 2. In passive mode preferably at least the second actuator 5b for extending and retracting the gangway is actively controlled, for example advantageously only that second actuator.

Advantageously, the motion sensors include orientation sensors and sensors for measuring a relative distance towards the target area, so that another orientation and/or another position can be measured, thereby avoiding the use of absolute position sensors. As a result, the motion sensors can be implemented in a relatively cheap manner.

The measurements may further include providing

measurement data performed from another structure, e.g. another vessel, concerning movements of the vessel at hand. Measurements may also include providing laser data or video data to retrieve relative position data.

In this respect it is noted that the use of orientation sensors and sensors for measuring a distance towards the target area can not only be applied with the method according to the description, but also, more generally, in combination with a method for compensating motions of a vessel, comprising the steps of measuring motions relative to at least one element in a target area and driving a multiple number of first actuators for moving a carrier relative to the vessel.

The measurements may include providing sensor data of motions of the vessel, the platform and/or the gangway, preferably the second end of the gangway, relative to the target area 2. In particular, vertical position data of the second end 16b of the gangway can be obtained by measuring the height of said gangway second end 16b relative to the target area 2, thereby enabling the control system 8 to follow the target area height relatively easily and accurately by driving the second actuator controlling pivoting the gangway relative to the first pivoting axis A.

The operation of an embodiment of the motion platform 4 is in general approximately as follows. When the vessel 1 is close to the structure or second vessel 2, the platform 4 is activated in active mode. Vessel motions are measured via the sensors 7, which measurement data is used as input for the control system 8. In response to the measurement data, a first driving signal and a second driving signal is generated for driving the respective actuators. Through continuous adjustment of the actuators 5a, 5b the gangway second end 16b will be able to virtually stand still relative to the structure 2, at least temporarily. The cable 20 is transferred to the structure or second vessel 2 preferably by the gangway 16, and is coupled to the second vessel or structure 2, for example by the coupling element 23 and counter coupling element 24 and/or mooring element 25. Then the cable 20 is released from the gangway 16 and pulled taut by the winch 21. The second end 16b of the gangway is preferably pushed against the second vessel or structure 2, especially to a mooring element 25. The platform is brought in passive mode, or fixed in a position. In this position persons, loads, animals and the like can safely be transferred from the vessel 1 to the second vessel or structure 2 or vice versa.

Coupling element 23 and counter coupling element 24 can be any known suitable set of cooperating coupling elements, such as for example hook and eye, loop and boulder, magnets, or any such elements known in the art and suitable for making a reversible connection. In fig. 5 and 6 by way of example only a hook is shown as coupling element 23, whereas an eye (not shown) is used as counter coupling element 24.

In fig. 8 A - D an embodiment is shown of a coupling element 23 connected to a cable 20 and a counter coupling element 24 for cooperation therewith. In fig. 8A - D schematically steps of a sequence for coupling a cable 20 to a structure 2 such as an off shore structure are shown. As is shown in fig. 8A schematically a first coupling element 23 can be provided having basically a hook shape or anchor shape. It can have a central leg 34 and a first and a second prongs 35, 36, one on either side of the central leg 34. The cable 20 can be connected to the free end of the leg 34. In this embodiment the end 16B of the gangway 16 is provided with a rod 37 over which a first prong 35 can be hooked, for carrying the first coupling element 23 towards the structure 2. On the structure 2, preferably at or near a mooring element 25, if applicable, the second coupling element 24 is provided, comprising a second rod 38. As is shown in fig. 8B the second prong 36 can be moved over and hooked to the second rod 38 by

manipulating the element 23 by movement of the gangway 16. In fig. 8B the element 23 is shown, hooked over both rods 37, 38.

Once the second prong 36 has been hooked over the second rod

38, the gangway end 16B can be retrieved slightly, such that the first rod 37 is pulled away from the element 23, out from under the first prong 36, as is shown in fig. 8C. The cable 20 is now connected to the structure 2, especially to the element 24. Then the cable can be tightened by the winch 21, and the end 16B, especially the platform 31 can be moved into the space 29 of the element 25 through the opening 29A as described, for properly coupling the gangway with the structure 2.

Should the cable 20 be released, the same sequence can be performed, in reversed order. Preferably the rods 37 and 38 are

positioned such that they do not interfere with a proper functioning of the coupling between the gangway 16 and the element 25 as described. For example the rods 37, 38 can be placed to a side of the gangway 16, or spaced slightly apart from the edge 32 of the platform 31, e.g. closer to the first end 16A of the gangway, such that the rod 37 does not enter into the space 29.

Obviously other coupling elements 23, 24 can be used, or differently shaped. For example the element 23 can have more than two prongs, for example three or four, as used in a grapnel or grapples or grapple irons, dredging hooks and the like. This coupling as shown in fig. 8 releases the cable

automatically from the gangway 16, preventing undesired and excessive forces acting on the gangway and/or on the cable 20. More in general it may be preferable to release the cable 20 from the gangway once the cable has been properly connected to the structure 2 for that purpose.

Since the platform 4 and the gangway 16 can be actively controlled, the end 16 and thus the first coupling element 23 can be positioned accurately and relatively easily with respect to the second coupling element 24, without the necessity of using a pilot line or the like to be transferred separately from the ship 1 to the structure 2 or vice versa, as is shown in the prior art. The cable 20 can be coupled directly and accurately. Whereas the cable can be released from the gangway 16 easily after coupling. The cable 20 and the gangway can then cooperate in holding the gangway end 16B in the proper position relative to the structure 2.

When releasing the gangway 16 from the second vessel or structure 2 the platform 4 is brought into active mode again, whereas the cable is released from the second vessel or structure 2 and, if applicable, coupled to the gangway again. Then the gangway is retracted and/or rotated and/or pivoted back onto the first vessel 1.

In fig. 5A - K schematically a series of steps is shown in providing a gangway 16 between a vessel 1 and a second vessel or structure 2. In fig. 5 A the platform 4 is shown in a stable state, with the gangway 16 pivoted down, such that the second end 16b thereof rests on the deck 27 of the vessel 1. An operator P can mount the platform 4 via the gangway 16. On the left hand side of the fig. 5A - K schematically part of a structure 2 is shown, which by way of example comprises a central column 2 A and a deck 2B. On the deck 2B a mooring element 25 is mounted, for example bolted to the deck 2B. The mooring element 25 has an in top view substantially triangular catching space 29 having an opening 29a open towards the side of the vessel 1 or at least an edge of the deck 2B, into which the second end 16B of the gangway 16 can be inserted. The space 29 is provided at a top side thereof with two guide flanges 30 extending inward from two opposite sides of the space 29. The second end 16B comprises a plate or platform element 31, for example having a substantially semi circular edge 32. The plate or platform element 32 can be inserted into the space 29 such that it is at least partly enclosed below the flanges 30, such that it cannot be removed from the space 29 in any direction other than through the opening 29A. Thus the second end 16B can be enclosed within the space 29 in all but one direction.

In fig. 5B the operator P has mounted the platform 4 and will actuate the system such that the end 16B of the gangway 16 is lifted from the deck 27. Fig. 5C shows the platform 4 with the gangway 16 having been rotated over an angle of about 180 degrees from the position in fig. 5B, such that the second end 16B faces the structure 2. In this position the platform 4 can still be in a fixed position, i.e. not in an active position compensating for movements of the vessel. In for example this position the system can be brought in active mode, such that the platform 4 will start compensating for the movements of the vessel relative to the structure 2, especially relative to the mooring element 25. As shown in fig. 5D the operator P can actuate a second actuator 5b such that the second part 26B of the gangway 16 is moved forward, i.e. such that the gangway 16 in the direction L is extended, bringing the second end 16B closer to and in contact with the mooring element 25. The cable 20 is allowed to follow the relative movement of the second end 16b, such that the coupling element 23 is brought to the mooring element 25 by the gangway 16. As shown in fig. 5E the second end 16B, especially the plate or platform element 32 is pushed into the space 29. The coupling element 23 can be coupled to the counter coupling element 24, and the cable can be pulled taut by the winch 21.

When or after the cable 20 has been properly coupled to the structure or second vessel 2, the platform can be brought out of the active mode, for example into the inactive mode. Preferably the gangway 16, especially the second end 16B thereof is actively pushed into the space 29, preferably by actuating the relevant second actuator 5b used for extending and retracting the gangway 16 in length direction. This can be done by moving the second part 26B relative to the first part 26A in the length direction L. Alternatively the platform can be used for providing sufficient pressure to the gangway, for example by partly actuating at least one of the first actuators. As is shown in fig. 5F then a staircase 33 can be mounted to the platform 4, for easy access to and from the carrier 6, off the deck 27. Since the platform can be kept stationary relative to the deck 27 this is very easily done. As is shown in fig. 5G a person P2 can easily move over the gangway 16 to the structure 2 or return from the structure 2 to the vessel 1. During such transfer preferably the gangway 16, especially the second end 16B is pushed against the mooring element 25, into the space 29, whereas the cable 20 is kept taut. In embodiments the gangway 16 is allowed to freely pivot around the first axis A relative to the platform 4, or at least the carrier. In embodiments the carrier 6 or at least the gangway 16 can pivot freely around the second axis B as well.

Preferably the space 29 in side view also has a substantially triangular shape or at least widens towards the opening 29A, such that the platform element or plate 32 can pivot within the space 29 over an angle a around an imaginary axis C parallel to the deck 2B and to the opening 29A, whereas preferably the space 29 and the platform element or plate 32 are designed such that the platform element or plate 32 can pivot within the space over an angle 6 around an imaginary axis D (fig. 7) perpendicular to the deck 2B and the axis C, in order to allow the gangway to pivot relative to the structure 2 too. Alternatively or additionally the mooring element 25 could be mounted to the structure 2 such that it can pivot relative to the structure 2. Thus the gangway 16 can follow relative movements of the vessel, with the platform in a fixed position or at least in a mode in which it not fully compensates for the relative movements of the vessel 1.

Fig. 5 H - K show schematically steps of retracting the gangway 16. In fig. 5H the staircase is removed, the platform 4 is brought back into active mode and the cable 20 is slackened and released from the structure by releasing the coupling element 23 from the counter coupling element 24. The cable is again supported by the gangway 16, for example by coupling the coupling element 23 to the gangway or in any other suitable way. Then the second end 16B is retracted from the space 29 in the mooring element 25, as is shown in fig. 51, for example by retracting the gangway 16 and/or by movement of the platform 4. Then the platform may be brought out of the active mode again and can form example be settled into a neutral position, as is shown in fig. 5J. From this position the gangway 16 can be rotated over 180 degrees again, for example by rotating the carrier 6, back above the deck 27whereafter the gangway can be brought into the position as shown in fig. 5K, allowing the operator P to leave the platform over the gangway 16.

During retracting the gangway 16 the cable may be rewound onto the winch or otherwise retrieved too.

In fig. 6A - D steps of an alternative method are shown, wherein the mooring element 25 is carried to the structure 2 by means of the gangway 16. In this embodiment with the platform 4 as shown in fig. 6A the mooring element is mounted onto the second end 16B of the gangway 16, for example by sliding it with the space 29 over the plate or platform element 32 or just the end 16B. On the structure 2 people P3 may be available for assistance. As described before, with the platform not in active mode, the gangway 16 is brought in a position above the deck and is then rotated outward, to the position shown in fig. 6B, in which the platform may be switched into active mode. The cable 20 may already be connected to the mooring element, for example using coupling and counter coupling elements 23, 24, or otherwise. In embodiments the cable 20 could even be fixedly connected to the mooring element 25. From the position in fig. 6B the second end 16B with the mooring element is brought to the structure 2, especially to a deck 2B or such surface for mounting the mooring element 25. The cable is released to allow for such movement of the mooring element end/or second end 16B.

Fig. 6D shows the position in which the mooring element 25 has been placed on the structure 2, with the platform still in active mode. The persons P3 on the deck 2B of the structure 2 can mount the mooring element 25 properly to the structure, permanently or temporarily, for example by bolting, screwing, welding, magnets, form fitting elements, or any other suitable elements or means. During the mounting of the mooring element 25 the platform 4 is preferably kept in active mode, such that no undesired forces are exerted on the mooring element by the gangway during mounting. Once the mooring element 25 has been properly placed and, where necessary, the cable 20 has been attached to the structure 2 and/or mooring element 25 and has been tensioned, such as pulled taut, the platform 4 could be brought out of the active mode.

When retracting the gangway 16 again, for example after it has completed it's function with respect to the structure 2, the mooring element 25 could be left in position on the structure 2, for example for future use in combination with the vessel or a similar vessel.

Alternatively the mooring element 25 could be released from the structure 2 and retracted with the gangway 16 for further use with the same or other structures 2. A mooring element 25 can be provided with appropriate connecting elements, such as pins, screws, bolts, rivets, holes or openings, magnets or any such means for connecting the mooring element 25 to the structure.

In fig. 7 in top view schematically a mooring element 25 is shown mounted on the second end 16B of the gangway 16, for carrying the mooring element 25 to or from the vessel form or to the structure 2. As can be seen the mooring element 25, especially the space 29 can be open towards a top side of the element 25, between the flanges 30.

However, such element 25 could also be closed to the top side 34, and could be differently shaped and/or dimensioned. In other embodiments the mooring element 25 could be designed to fit within the second end 16B of the gangway, for example by providing an opening in the plate or platform element 32 which can be placed over the mooring element, for example forming more or less a ball joint type connection.

The method for compensating motions of a vessel can at least partly be performed using dedicated hardware structures, such as FPGA and/or ASIC components. Otherwise, the method can also at least partially be performed using a computer program product comprising instructions for causing a processor of the computer system to perform the above described steps of the method according to the invention.

Processing steps can in principle be performed on a single processor, in particular steps of providing first and second driving signals for driving the multiple number of first actuators and the at least one second actuator. However, it is noted that at least one step can be performed on a separate processor, e.g. a step of receiving motion sensor data of motions relative to at least one element in a target area.

In a system and method of the present invention the gangway can in embodiments be actively operated, i.e. be in an active mode, meaning that the relevant second actuator or actuators can actively move the second end of the gangway relative to the platform cq carrier thereof, for example by extending or retracting the gangway and/or changing the angle between the gangway and the platform cq carrier thereof. In embodiments the gangway can be brought into a passive mode, in which the or each second actuator for operating the gangway is or can be passive, meaning that the length and/or position of the gangway is defined passively by the relative position of the vessel and the second structure or vessel, wherein the length variations and/or angle variations are provided for at least mainly by pulling and/or pushing forces exerted on the gangway by the vessel and/or structure or second vessel. In embodiments a main aspect can be defined at least by using a gangway for transferring a connecting cable from a vessel to a structure or second vessel.

The invention is by no means limited to the embodiments specifically shown in the drawings and/or discussed in the description. Many variations thereof are possible within the present invention, including but not limited to all combinations of individual or groups of features as disclosed. The gangway can be connected differently to the platform, for example by means of a different hinging structure, such as a connection which allows pivoting around different axis. The gangway can have more than two moveable parts, or only one, and can be connected to the platform 4 such that it can move in the longitudinal direction of the gangway relative to the platform, especially the carrier thereof, for at least partly compensating for movements of the vessel relative to the structure. The mooring element can be omitted on the structure, or can be an integral part thereof. The mooring element can be designed

differently, as long as it allows for a connection with the platform such that the gangway can apply a force to the mooring element, preferably at least a pushing force against the mooring element. The platform can be designed differently, for example with a different number of actuators and/or different types of actuators. The second actuator for extending and retracting the gangway can be designed in any appropriate way, such as for example but not limited to a hydraulic, pneumatic or electric piston- cylinder system, a spindle motor, a cable with winch or any such suitable means known in the art, or combinations thereof, for example enhanced safety. In stead of or additional to the cable a more rigid connector could be used between the vessel and the structure, such as for example but not limited to a pole. In the embodiments shown the winch is provided on the deck of the vessel. In other embodiments the winch could be connected to the platform, for example to a base thereof. The cable can also be connected to the vessel and/or to the platform in a different manner, for example to a clamp, boulder or other such means known in the art. In alternative embodiments additionally or alternatively the winch or a winch can be placed on the structure, to be used for forming a cable connection between the vessel and the structure. Such winch can for example be a winch already available. Alternatively and/or additionally a crane or other hoisting device could be used for transferring the cable and/or the mooring element from the vessel to the structure and/or vice versa and/or for forming the cable connection. In the embodiments shown and discussed he platform is operated at least partly by a human operator on the platform. It shall be clear that it will also be possible to operate such platform remotely, for example from a cabin or from the deck of the vessel or from the structure or even from further away, such as from a shore.

In embodiments the motion platform can be moved actively while moving the second end of the gangway to the second vessel or structure, whereas the motion platform is allowed to passively follow the relative movements of the vessel after coupling the cable and/or the second end of the gangway to the second vessel or structure and/or the motion platform can be moved actively while moving the second end of the gangway to the second vessel or structure, whereas the gangway is allowed to passively follow the relative movements of the vessel after coupling the cable and/or the second end of the gangway to the second vessel or structure. The motion compensation platform can comprise or be formed by a Stewart platform with hydraulic, pneumatic and/or electric cylinders, as is known in the art.

In embodiments disclosed herein the platform can be brought from an active mode to an inactive mode and vice versa. In embodiments the inactive mode could be designed such that in such mode the platform is in a fixed position, for example a rest position wherein the first actuators are kept in a fixed length. In embodiments an inactive mode can be designed such that the platform, especially the carrier can still move by length adjustments of one, some or all of the first actuators, but either not actively controlled by the system or controlled to an extend that the platform does not compensate for movements of the vessel, for example for dampening movements resulting from shock or load differences.

These and many other variations and combinations should be considered also having been disclosed herein.

Claims

1. A vessel including a motion platform, which platform comprises:

- at least one carrier for bearing, moving and/or transferring a load;

- a gangway provided with a first end pivotably connected to the carrier and an opposite second end;

- a multiple number of first actuators for moving the carrier relative to the vessel;

- a control system arranged for driving the multiple number of first actuators, wherein a cable extends from the vessel and/or the motion platform to at least a position at or near the second end of the gangway, wherein the cable is provided with a connecting element at an end opposite the vessel and/or motion platform, for connecting to another vessel or structure, especially an off-shore structure, wherein the connecting element comprises at least a first prong for hooking over an element connected to the gangway and at least a second prong for hooking over a coupling element provided on the other vessel or structure.

2. A vessel according to claim 1, wherein the cable is connected to the vessel or the motion platform by means of at least a winch, such as an auto recovery winch.

3. A vessel according to claim 1 or 2, wherein the connecting element is substantially anchor or hook shaped and wherein the element connected to the gangway and/or the coupling element provided on the other vessel or structure are preferably rod shaped.

4. A vessel according to any one of the preceding claims, wherein at least a second actuator is provided for moving the gangway relative to the carrier, wherein the control system is also arranged for driving the at least one second actuator.

5. A vessel according to any one of the preceding claims, wherein the control system is arranged for compensating a motion of the vessel in at least one degree of freedom by driving the at least one second actuator.

6. A vessel according to any of the preceding claims, wherein at least one second actuator is arranged for pivoting the gangway with respect to a first pivoting axis substantially transverse with respect to a longitudinal axis of the gangway.

7. A vessel according to any of the preceding claims, wherein at least one second actuator is arranged for pivoting the gangway with respect to a second pivoting axis substantially transverse with respect to the carrier.

8. A vessel according to any of the preceding claims, wherein the first gangway end is provided on a first gangway section, wherein the second gangway end is provided on a second gangway section, and wherein at least one second actuator is arranged for moving the second gangway section with respect to the first gangway section substantially along a gangway longitudinal axis.

9. A vessel according to any of the preceding claims, wherein the motion compensation platform comprises or is formed by a Stewart platform with hydraulic, pneumatic and/or electric cylinders.

10. Assembly of a vessel according to any one of the preceding claims and a mooring element, wherein the mooring element comprises a counter coupling element for coupling to the cable and/or a coupling element connected to the cable.

11. Assembly according to claim 10, wherein the mooring element is provided with a receptacle for receiving the second end of the gangway, within and/or over the receptacle.

12. Assembly according to claim 10 or 11, wherein the second end of the gangway and the mooring element are designed such that the mooring element can be carried by the gangway during movement thereof relative to the vessel.

13. Assembly according to any one of claims 10 - 12, wherein the mooring element is provided with connecting elements for connecting the mooring element to a vessel or structure, such as an off-shore structure, permanently and/or reversibly.

14. A motion platform, particularly suitable for a vessel as described in any one of claims 1 - 9 or an assembly according to any one of claims 10 - 13, which platform comprises at least one carrier for bearing, moving and/or transferring a load, a gangway provided with a first end pivotably connected to the carrier and a second end for contacting a target area, a multiple number of first actuators for moving the carrier relative to the vessel, at least a second actuator for moving the gangway relative to the carrier, a control system arranged for driving the multiple number of first actuators, wherein the control system is also arranged for driving the at least one second actuator, and wherein a cable is provided which is or can be carried at or near the second end of the gangway.

15. A method for providing a gangway between a first vessel and second vessel or a structure, such as an off-shore structure, wherein the gangway is carried at a first end by a motion platform on the vessel and has an opposite second end, wherein further a cable is provided, connected to the vessel and/or the platform, comprising the steps of:

connecting the cable to the second vessel or structure; allowing the motion platform to follow the movements of the vessel relative to the movements of the second vessel or structure, especially by bringing the platform from an active mode into an inactive mode and/or allowing the gangway to follow the movements of the vessel relative to the movements of the second vessel or structure, especially by bringing the gangway from an active mode into an inactive mode, wherein the cable is provided with a connecting element at an end opposite the vessel and/or motion platform, for connecting to another vessel or structure, especially an off-shore structure, comprising the steps of:

carrying the coupling element to a coupling element at the other vessel or structure;

moving a free end of the gangway towards the other vessel or structure.

16. A method according to claim 15, wherein the cable during transfer to and/or from the second vessel or structure is carried by the gangway and the cable is released from the gangway after connecting the cable to the second vessel or structure, and is pulled taut, preferably before allowing the motion platform to follow the relative movements.

17. A method according to claim 15 or 16, wherein the motion platform is moved actively while moving the second end of the gangway to the second vessel or structure, whereas the motion platform is allowed to passively follow the relative movements of the vessel after coupling the cable and/or the second end of the gangway to the second vessel or structure.

18. A method according to claim 15 or 16, wherein the motion platform is moved actively while moving the second end of the gangway to the second vessel or structure, whereas the gangway is allowed to

passively follow the relative movements of the vessel after coupling the cable and/or the second end of the gangway to the second vessel or structure.

19. A method according to any one of claims 15 - 18, wherein after coupling the cable to the second vessel or structure, the cable is pulled taut, whereas the second end of the gangway is pushed against the second vessel or structure, especially against a mooring element, preferably at least partly by pushing a second part of the gangway in a length direction of the gangway away from the platform.