The invention relates to a motion compensating supporting structure for a vessel based utility module, in particular a vessel based transport unit such as a telescopic gangway.

Telescopic gangways are generally known, e.g. in a motion compensated gangway comprising a movable transition deck and a telescopic gangway connected to the transition deck. The telescopic gangway typically has a tip that may be held, during operation of the motion compensated gangway, in close proximity of an object such as an offshore construction to or from which a load or a person has to be transferred. The movable transition deck may have a motion compensating supporting structure forming a base to be mounted on a vessel, including actuators, e.g. hydraulic pistons, to compensate for relative motion between the base or vessel and an object to or from which the load/person can be transferred. Said relative motion may for example result from waves or rolling, pitching, and/or yawing motion of a vessel or boat floating on the water.

Patent pubhcation NL 1027103 discloses a vessel with a Stewart type construction for compensating motions of a ship. The construction comprises a transition deck, borne on six hydraulic cylinders, and motion sensors. During use, with the aid of the sensors, the motions of the vessel are measured. With the aid of these measurements, the orientation and/or position of the cyhnders is driven continuously so that the transition deck remains approximately stationary relative to the fixed world. In this manner, motions of the vessel are compensated and for instance people or loads can be transferred from the vessel onto a stationary offshore construction, or vice versa.

Motion compensated gangways per se, such as for compensating for vessel motions when transferring personnel and/or loads are known in the art. For example from the Ampelmann® system as disclosed in general in NL1027103, or systems disclosed in WO2012/138227 and W02013/10564.

Roll compensation can be used actively to level a gangway and access platform parallel to the horizon. Roll compensation may has at least two value drivers, as it significantly makes it easier for an operator to land the tip on a structure increasing the practical workabihty. Further roll compensation may increase the comfort for the transferee when walking over the gangway.

An object of the invention is to provide a motion compensating supporting structure for a vessel based transport unit such as a telescopic gangway.

It is also an object of the invention to provide an effective motion compensating supporting structure for a vessel based transport unit such as a telescopic gangway that is relatively cost efficient.

Thereto, according to an aspect of the invention, a motion compensating supporting structure for a vessel based utility module, in particular a vessel based transport unit, comprising a four-bar mechanism having four revolute joints for forming a closed loop linkage, wherein a first revolute joint and a second revolute joint of the four revolute joints are fixedly attached to a base mountable on the vessel, the four-bar mechanism further having a first bar and a second bar, each of the first and the second bar being connected, at a first end thereof, with the first revolute joint and the second revolute joint, respectively, and extending from said respective revolute joint mainly downwardly, a second end of the first and the second bar, opposite to the respective first end, being connected to a third revolute joint and a fourth revolute joint, respectively, of the four revolute joints, the four-bar mechanism also having a rigid platform element having a first end connected to the third revolute joint and having a second end, opposite to the first end, connected to the fourth revolute joint, forming the closed loop linkage. By applying a four-bar mechanism, an effective self stabilizing roll compensating supporting structure for a vessel based transport unit is obtained. By integrating roll and/or pitch compensation the structure will naturally tend to return to a state of stable, safe equilibrium. When the base of the vessel is forced to tilt under angle relative to the horizontal direction, the platform element is brought in a new equilibrium state that typically has an orientation between a horizonal orientation and the actual orientation of the vessel base. Then, a rolling and/or pitching motion of the vessel base will at least partially be compensated, in particular a rolling and or pitching motion of the vessel base will at least partially passively be compensated.

Further, by applying a four-bar mechanism, the compensation technique provides a support structure that can compensate angular motions of the vessel over one or two axes. The structure may be inherently passive, saving energy costs. As a result, a rolling and/or pitching movement of the vessel may at least partially be compensated in a passive, reducing work that otherwise needs to be done by an actuator, thus saving power requirement. Also, the size and layout of the motion compensating supporting structure may be flexible in design.

Preferably, the structure includes an actuator or generator for actively positioning the vessel based transport unit and or for generating electrical power from movements of the transport unit relative to the vessel.

The vessel based transport unit can e.g. be implemented as a telescopic or other gangway, mast or pedestal.

The invention also relates to a vessel.

The invention will be further elucidated on the basis of exemplary embodiments which are represented in the drawings. The exemplary embodiments are given by way of non-limitative illustration of the invention. In the drawings: Fig. 1 shows a schematic side view of a motion compensating supporting structure according to the invention;

Fig. 2 shows a schematic side view of the motion compensating supporting structure shown in Fig. 1 in three different states;

Fig. 3 shows a schematic perspective view of a vessel provided with the motion compensating supporting structure shown in Fig. 1;

Fig. 4 shows a schematic perspective view of the motion compensating supporting structure shown in Fig. 1;

Fig. 5 shows a schematic perspective view of a second embodiment of a motion compensating supporting structure according to the invention;

Fig. 6 shows another schematic perspective view of the motion compensating structure shown in Fig. 5, and

Fig. 7 shows a schematic perspective view of a third embodiment of a motion compensating structure according to the invention.

In the figures identical or corresponding parts are represented with the same reference numerals. The drawings are only schematic representations of embodiments of the invention, which are given by manner of non-limited examples.

Figure 1 shows a schematic perspective view of a motion compensating supporting structure 10 according to the invention, for a vessel based transport unit such as a telescopic gangway. The motion compensating supporting structure 10 includes a four-bar mechanism 12 forming a closed loop linkage that is arranged for at least partially compensating a motion of the vessel, using gravitation.

Generally, the motion compensating supporting structure 10 can not only be used for supporting a vessel based transport unit but also for supporting another vessel based utihty module such as a crane, utihty arm or pedestal.

The four-bar mechanism 12 has four revolute joints 14, viz. a first revolute joint 14a, a second revolute joint 14b, a third revolute joint 14c and a fourth revolute joint 14d, interconnecting four bars 16, 18, 20 in a closed loop. As shown, the joints 14 and bars 16, 18, 20 are alternatingly connected to each other, in series. The first revolute joint 14a and the second revolute joint 14b are fixedly attached to a base 18 mountable on the vessel. Further, a first bar 16a of the four bars is connected, at a first end 16a’ of said first bar 16a, to the first revolute joint 14a. Similarly, a second bar 16b of the four bars is connected, at a first end 16b’ of said second bar 16b, to the second revolute joint 14b. The first and the second bar 16a, b, also referred to as the first and the second rocker, may pivot, at their first end 16a’, 16b’, relative to the base 18 mountable on the vessel. The first bar 16a and the second bar 16b both extend from the respective revolute joints 14a, 14b, mainly downwardly. A second end 16a” of the first bar 16a, opposite to the first end 16a’ of the first bar 16a, is connected to the third revolute joint 14c. Similarly, a second end 16b” of the second bar 16b, opposite to the first end 16b’ of the second bar 16b, is connected to the fourth revolute joint 14d. The four-bar mechanism 12 also has a rigid platform element 20 having a first end 20’ connected to the third revolute joint 14c and having a second end 20”, opposite to the first end 20’, connected to the fourth revolute joint 14d.

The serial chain including the first revolute joint 14a, the first bar 16a, the third revolute joint 14c, the rigid platform element 20, the fourth revolute joint 14d, the second bar 16b, the second revolute joint 14b and the base 18 connected to the first revolute joint 14a forms a closed loop planar linkage. Here, the base 18 and the rigid platform element 20 form the third bar and the fourth bar, respectively, of the four -bar mechanism 12.

In the shown embodiment, the rigid platform element 20 includes a coupler platform boom 20b and a first and second coupler leg 20a, c extending from the coupler platform boom 20b downwardly towards and up to the third revolute joint 14c and the fourth revolute joint 14d, respectively. In the shown embodiment, the coupler platform boom 20b extends mainly horizontally. It is noted that, in principle, the coupler platform boom 20b may have another orientation, e.g. slightly tilted relative to a horizontal direction. Also, the coupler legs 20a, c may extend in another orientation, e.g. sidewardly and/or upwardly. The coupler platform boom 20b may serve as a supporting unit for supporting the vessel based transport unit. It is further noted that the rigid platform element 20 may have more components, e.g. multiple coupler platform boom components that are mutually connected.

The rockers 16a, b, also referred to as the first and second bar 16a, b, each lie on a corresponding rocker line 22a, b intersecting at an instantaneous center of zero velocity point or Instantaneous Center of Rotation point ICOR located above the coupler platform boom 20b. The ICOR changes depending on the orientation of the individual rockers 16a, b. Further, the combination of the platform element 20 and all components mounted thereon including the vessel based utility module have a center of gravity COG located at a level below the ICOR as shown in Fig. 1.

The motion compensating supporting structure 10 further includes an actuator 24 controlling the position of the third revolute joint 14c relative to the base 18 mounted to the vessel. In another embodiment the actuator 24 may be arranged in another way, however being coupled to the four-bar mechanism controlling the position of the rigid platform element 20, and thereby all joints and links. Generally, an actual position of a hnk between the actuator 24 and the four-bar mechanism is a derivative of the position of the rigid platform element 20.

Figure 2 shows a schematic side view of the motion compensating supporting structure 10 shown in Fig. 1 in three different states. On the left hand side the structure 10 is shown in a neutral stance wherein the coupler platform 20b is mainly horizontal, in equilibrium. In the center of Fig. 2, the structure 10 is shown in an off balance state wherein the structure 10 is not in equilibrium. Here, the coupler platform 20b and the base 18 are tilted relative to the mainly horizontal orientation of the neutral stance, at the same angle relative from the horizontal orientation, e.g. due to a rolling movement of the vessel. On the right hand side in Fig. 2, the structure 10 has found a new equilibrium. Here, the position and/or orientation of joints and bars have changed, and both the platform element and the base are still tilted relative to the horizontal orientation, however the platform element 20b now being tilted with a tilting angle relative to the horizontal orientation that is smaller than a tilting angle of the base 18 relative to the horizontal orientation.

As shown in Fig. 2, the four-bar mechanism of the structure 10 is arranged so as to at least partially compensate for a rolhng and/or pitching movement of the vessel. In its equihbrium state or neutral stance shown on the left hand side, the center of gravity COG is located at a vertical position right below the Instantaneous Center of Rotation point ICOR. Here, the coupler platform 20b may swing around the neutral stance, e.g. induced by turbulence forces exerted on the vessel based transport unit, while the base 18 mounted on the vessel maintains a horizontal orientation. Then, the platform 20b always tends to return to the neutral stance even though the center of gravity COG is above the revolute joints of the four-bar mechanism. During swinging, the coupler platform 20b substantially maintains its mainly horizontal orientation.

It is noted that in another embodiment, e.g. for supporting another vessel based utility module, such as a pedestal, the center of gravity COG may be located at a higher level than the center of orientation ICOR.

When the vessel rolls, the base 18 tilts relative to a horizontal hne H. Then, also the coupler platform 20b tilts having a first tilting angle agl relative to the horizontal line H, as shown in the center of Fig. 2, in its off balance state. The center of gravity COG is located at a vertical position horizontally offset relative to the Instantaneous Center of Rotation point ICOR. Due to gravitational force resulting in a moment around the ICOR, the four-bar mechanism tends to return to a more horizontal position, as shown on the right hand side in Fig. 2, wherein the center of gravity COG is located again at a vertical position right below the Instantaneous Center of Rotation point ICOR, finding a new equilibrium state. Here, the coupler platform 20b still has a tilted orientation relative to the horizontal line H, however now having a second tilting angle ag2 relative to the horizontal line H, the second tilting angle ag2 being smaller than the first tilting angle agl in the state shown in the center of Fig. 2. In other words, the four-bar mechanism of the structure 10 is self balancing to an equilibrium state wherein the tilting angle of the coupler platform 20b relative to a horizontal line H is reduced thus at least partly compensating for rolling movements of the vessel. Again, in the new equilibrium state shown on the rights hand side in Fig. 2, the coupler platform 20b may swing around said new equihbrium state, e.g. induced by turbulence forces exerted on the vessel based transport unit, while the base 18 mounted on the vessel maintains its orientation relative to the horizontal line H.

The actuator 24 may be arranged as a driver for actively adjusting an orientation of the coupler platform 20b by moving the third revolute joint 14c in a direction mainly parallel to a direction from the first revolute joint 14a to the second revolute joint 14b. Additionally or alternatively, the actuator 24 may function as a generator converting movements of the coupler platform into electrical energy. The structure 10 may be realized with a generator only or with an actuator acting as a driver only, or without any of an actuator or generator.

Figure 3 shows a schematic perspective view of a vessel or boat 50 provided with the motion compensating supporting structure 10 shown in Fig. 1. The structure 10 includes an additional four-bar mechanism 30, also referred to as second four-bar mechanism, coupled in parallel with the first four-bar mechanism 12 described above, using linkage bars 95, together forming a double four-bar mechanism moving dependent from each other. Then, the two four bar mechanisms are dependent from each other and act as a single four bar mechanism. The second four-bar mechanism 30 has an orientation similar to the first four -bar mechanism 12, for performing similar movements as the first four-bar mechanism 12. Similar to the first four-bar mechanism 12, the second four-bar mechanism 30 also has a first, second, third and fourth revolute joint 34a,b,c,d forming together with a first bar 36a, a second bar 36b, the base 18 and a rigid platform element 40 a closed loop planar linkage, parallel to the closed loop planar linkage of the first four-bar mechanism 12. The second four-bar mechanism 30 further includes an optional actuator 44 controlling the position of the third revolute joint 34c relative to the base 18 mounted to the vessel.

The motion compensating supporting structure 10 further includes a rigid platform frame 42 mounted on the rigid platform element 20 of the first four-bar mechanism 12 and on the rigid platform element 40 of the second four-bar mechanism 30, for supporting the vessel based transport unit.

In Fig. 3, the vessel based transport unit is implemented as a telescopic gangway 60 having a main boom 62, a telescoping boom 64 and a rotatable transition deck 66 carrying the main and telescoping booms 62, 64 and rotatable relative to a mainly vertical axis A. The telescoping boom 64 is telescopable with respect to the main boom 62 in a longitudinal direction L to adjust a longitudinal length L of the telescopic gangway 60. Within the context of this application the term telescopable is meant to be construed as being movable, such as being able to move in and out of each other and/or with respect to each other along said longitudinal direction L.

It is noted that instead of the telescopic gangway 60 another vessel based transport unit can be supported by the motion compensating supporting structure, such as a gangway of another type, a mast and/or a pedestal.

It is further noted that, in principle, the motion compensating supporting structure may include a single four-bar mechanism only. As shown in Fig. 3, a line Li interconnecting the first revolute joint 14a to the second revolute joint 14b may be mainly transverse to a longitudinal axis LA of the vessel 50 so as to stabilize a roll movement of the vessel 50. However, in another embodiment, the first revolute joint 14a and the second revolute joint 14b may each have a rotating axis that is mainly parallel to a longitudinal axis L of the telescopic gangway 60 so as to stabilize a roll movement of the telescopic gangway 60.

Generally, a motion compensating supporting structure may be provided wherein the first revolute joint 14a and the second revolute joint 14b each have a rotating axis that is mainly parallel to a longitudinal axis of the vessel based utility module so as to stabilize a roll movement of the vessel based utility module. Here, the vessel based utility module is for example a gangway, such that gangway roll movements can be compensated. Here, a luffing actuator may compensate pitch movements of the gangway.

Figure 4 shows a schematic perspective view of the motion compensating supporting structure 10 shown in Fig. 1. The structure 10 includes a rigid platform frame 42 mounted on the first four-bar mechanism 12 and the second four-bar mechanism 30 that dependent on each other, via linkage bars 95, and act as a single four bar mechanism. In Fig. 4 the fourth revolute joint 14d of the first four-bar mechanism 12 is explicitly shown. Generally, the first and the second four-bar mechanism 12, 30 each have a first revolute joint 14a; 34a, a second revolute joint 14b; 34b, a third revolute joint 14c, 34c and a fourth revolute joint 14d, 34d. Further, the base 18 mounted to the vessel 50 and the first and second revolute joints 14a; 34a, 14b; 34b are shown.

The motion compensating supporting structure 10 can be used to compensate a one axis or one dimensional movement, e.g. for stabihzing a roll movement of a telescopic gangway. Figure 5 shows a schematic perspective view of a second embodiment of a motion compensating supporting structure 100 according to the invention. Here, the structure 10 includes an extra first four-bar mechanism 70 and an extra second four-bar mechanism 72 arranged transverse to the two four-bar mechanisms 12, 30, also referred to as first double four-bar mechanisms 12, 30, shown in Fig. 3 and described above. The extra first and second four-bar mechanisms 70, 72, referred to as a second double four-bar mechanism 70, 72, are also arranged in parallel to each other, similar to the first double four-bar mechanisms 12, 30 and are mounted on top of the rigid platform elements 20, 40 of the first double four- bar mechanisms 12, 30.

Similar to the first double four-bar mechanisms 12, 30, the second double four-bar mechanisms 70, 72 each have four revolute joints 74a,b,c,d, first and second bars 76a, b, and rigid platform elements 80, 82. Again, a second a rigid platform frame 92 is mounted on the rigid platform elements 80, 82, for supporting a vessel based transport unit. Here, a line Li2 interconnecting the first revolute joint to the second revolute joint of each extra four-bar mechanism 70, 72 is mainly parallel to the longitudinal axis LA of the vessel 50 so as to stabihze a pitch movement of the vessel 50.

The first and second revolute joints 74a, b are fixedly attached to the rigid platform elements 20, 40 of the first double four-bar mechanisms 12, 30 such that the first and second double four -bar mechanisms 12, 30, 70, 72 are arranged in series, for both compensating roll and pitch movements of the vessel 50.

Generally, rotating axes of the first and second revolute joints of the transverse four-bar mechanism may be mainly transverse to rotating axes of the first and second revolute joints of the four-bar mechanism or double four-bar mechanism so as to stabilize pitch and roll movements of the vessel. Here, the vessel based utility module is for example a pedestal arranged for transferring at heights above the sea surface. Then, compensation at the base of the pedestal may significantly reduce motions at a top of the pedestal, on transfer deck. Also, the vessel based utility module can be a motion compensation arm, e.g. for various purposes such as technical work platform deployment, or for using it to establish a connection for offshore vessel charging. Further, the vessel based utihty module can be a motion compensated feeder, e.g. for a crane, for making an offshore lifting operation safer.

It is noted that the first and second double four-bar mechanisms 12, 30, 70, 72 can be arranged in reverse order such that the second double four-bar mechanism 70, 72 is mounted to the vessel 50, while the first double four-bar mechanism 12, 30 is mounted on top of the second double four-bar mechanism 70, 72. Further, the orientation of the respective double four-bar mechanisms may be different, e.g. having a non-transverse orientation with respect to each other.

Figure 6 shows another schematic perspective view of the motion compensating structure shown in Fig. 5. The structure 10 has a first double four-bar mechanism and the second double four-bar mechanism connected to each other via an intermediate platform 96 and arranged so as to provide two axes or two dimensional movement compensation i.e. in two independent directions X,Y extending parallel to the platform, e.g. for a pedestal, a motion compensation arm or a motion compensated feeder mounted on the platform 42. The structure 10 has an actuator 24 coupled to the first double four-bar mechanism controlling the first double four-bar mechanism position and another actuator 24 coupled to the second double four-bar mechanism controlling the second double four-bar mechanism position. Linkage bars 95, 95’ are provided interconnecting the individual four-bar mechanisms of the first and second double four-bar mechanism.

Figure 7 shows a schematic perspective view of a third embodiment of a motion compensating structure 10 according to the invention. The structure 10 is provided with three actuators 24a-c providing three axes or two dimensional movement compensation i.e. in two independent directions X,Y extending parallel to the platform 42 and in a rotating direction around the height direction Z extending perpendicular to the platform 42, i.e. pitch, roll and yaw movements, e.g. for a pedestal, a motion compensation arm or a motion compensated feeder mounted on the platform 42. The structure has three linkage bars 95a-c and three four-bar mechanisms connected to a corresponding actuator 24a-c. The joints are shown as ball joints. However, joints can also be implemented as gimbals or cardan joints. The embodiment shown in Fig. 7 may be implemented with less components, compacter design or build size and/or lighter weight.

It will be clear to the skilled person that the invention is not limited to the exemplary embodiment represented here. Many variations are possible. Such variations shall be clear to the skilled person and are considered to fall within the scope of the invention as defined in the appended claims. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments. However, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.