Patent Publication Number: US-6910435-B2

Title: Mooring device

Description:
This application is a National Phase in the United States of PCT/NZ01/00026 and claims the benefit of the New Zealand Application 501395 filed Feb. 26, 2000. 

   TECHNICAL FIELD 
   The present invention relates generally to mooring devices for releasably securing and retaining in position a large object in relation to a nearby second large object. More particularly, the present invention relates to robotic mooring devices for controlling the mooring and departure process for vessels from a fixed or floating dock, or from another vessel. 
   BACKGROUND ART 
   Whilst the invention relates to a mooring device for releasably securing and retaining in position a large object in relation to a nearby second large object, it will be described with reference to mooring devices for docking and undocking a vessel. However, it will be understood that the invention is not limited solely to such example. 
   The use of robot-like mooring devices has been proposed to reduce the labour intensity, hazards and time taken by using the traditional mooring lines. These devices should be capable of restraining movement of the ship in response to winds, currents, shifting tides, movement of the ship due to the addition or removal of cargo, and the like. 
   An example of such a device is shown in WO91/14615, which describes a mechanism with a prehensile assembly for engaging a bollard on the vessel. A disadvantage of this type of system is that the vessel must be specially adapted. Further, precision is required to align the two coupling components. The prehensile assembly is not adapted to be quickly disengaged during the departure process. 
   A known system of the applicants employs a mooring arm mounted within a ship to one end of which a vacuum cup is fixed. During mooring, the vacuum cup protrudes through an opening in the hull of the ship and attaches to a bearing plate. The bearing plate is fixed to the dock, but able to rise and fall freely relative to it. Such a system is significantly more efficient than the traditional mooring process but because of the bearing plate, it is only suited to applications where the ship has a dedicated dock. In addition, other means are provided for securing the vessel accurately in the fore and aft direction with respect to the dock. Where such is not the case, this inability to absorb forces acting on the vessel in the fore and aft direction and the necessity to provide a means of raising and lowering the dock mounted attachment plate is a disadvantage of this known system. 
   U.S. Pat. No. 3,974,794 illustrates an alternative dock mounted system which is able to handle a range of different vessels, with no modification to the vessel being necessary, since the vacuum cups bear on the ship&#39;s hull. Hydraulic cylinders are used to rotate the vacuum cup fixed to a dock to conform to the shape of the hull. 
   U.S. Pat. No. 3,463,114 describes a mooring device with a buffered telescopic boom fitted with a vacuum cup for engagement with the hull of a ship. The boom is fixed in vertical guides and it is allowed to rise and fall with the ship when fastened thereto. 
   In both of these systems (in U.S. Pat. Nos. 3,463,114 and 3,974,794) the ship is rigidly fixed to the mooring station in the longitudinal direction with respect to the ship, consequently the mooring device is subject to deleterious impact loads in this direction. Neither system may be used to control the position of the vessel in the fore-and-aft direction. 
   DE 2557964 illustrates a fending device with two dimensional movement and impact absorption. However there is no means for mooring a vessel, nor retain the moored vessel against a dock. 
   Generally, there are three degrees of freedom of the position of a floating vessel: fore-and-aft, rise-and-fall, and athwart-ship (and there are three degrees of freedom of its orientation or rotation: roll, pitch and yaw). When mooring a vessel, particularly a massive vessel, it is desirable to have a degree of compliance in the mooring device, to avoid impact loads which may occur in any direction. Additionally, when loading a vessel for example, it is often desirable to control and to vary the fore-and-aft position of the vessel relative to the dock, as well as to control the athwart-ship position. 
   It is an object of the present invention to provide a mooring device which automatically positions a first large object relative to a nearby second large object, with precise control of both the fore and aft and the athwart-ship position of the first object with respect to the second object, and which device reliantly buffers the mooring forces exerted between the two objects. 
   It is a further object of the present invention to provide a mooring device which provides increased control over the movement of the first large object relative to the second object, as compared with mooring devices known in the art. 
   It is a further object of the present invention to address the foregoing problems in respect of positioning a first large object relative to a second large object or to provide the public with a useful choice. 
   Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. 
   DISCLOSURE OF INVENTION 
   According to one aspect of the present invention there is provided a mooring robot for releasably fastening to a surface of a first moveable object, the mooring robot being mountable to a second object, said first object moving in response to the application of external forces, relative to the second object, which movement moves the first object from a pre-determined operating position, the mooring robot including:
         an attractive attachment element for releasable engagement with said surface; and   a movement unit, to which is pivotally secured the attractive element, said movement unit including a capability for three degrees of freedom of translational movement, which capability is translated through said attachment element to said surface to the first object, and wherein said unit includes mechanical means to provide resilient restorative forces associated with each of the two degrees of freedom of the movement in the horizontal plane;   wherein the resilient restorative means providing said restorative forces operates to return the attachment element and thus the first object to said predetermined operating position.       

   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein said second object is either moveable or fixed in location. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein said first object is a sea vessel, and the second object is selected from: a fixed dock, a floating dock and a second vessel. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein the said surface is the freeboard of a hull of a vessel. Optionally, the said surface may extend below the freeboard. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein said first object is a selected from: a fixed dock, a floating dock and a first vessel and the second object is a vessel. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein the restorative force is proportional to the displacement of the first object from the predetermined operating position in the horizontal plane. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein the restorative means stores energy as the first object is displaced (in response to said external forces) from the pre-determined operating position, and releases said stored energy to return the first object back to the pre-determined operating position. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein the attractive element comprises at least one vacuum cup having a circumferential elastomeric seal. The vacuum is preferably formed by a vacuum pump. Optionally, the mooring robot includes two vacuum cups. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein the capability of the three degrees of freedom of movement of the movement unit are polar coordinate-type movement depending on one translational motion and two rotations. 
   Optionally, the capability of the three degrees of freedom of movement of the movement unit are of a Cartesian coordinate-type movement depending on three translational motions, a cylindrical coordinate-type movement depending on two translational motions and one rotation, and an articulation-type movement depending on three rotations. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein the movement unit uses polar co-ordinate movement and comprises linear actuators arranged to provide the said one translational motion and two rotations. 
   According to a further aspect of the present invention there is provided a mooring robot as described above, wherein the linear actuators are fluid powered piston-and-cylinder units, or rams. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein said rams are double-acting hydraulic rams, having fluid connections at both ends of their cylinders and providing linear force on both their extension and retraction strokes. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein the restorative means comprises an hydraulic accumulator. 
   According to a further aspect of the present invention there is provided a mooring robot substantially as described above, wherein the movement unit further comprises:
         a robot arm with a telescoping end,   a vacuum cup assembly which is fixed to the telescoping end, said assembly including at least one vacuum cup; and   a gimbal in which the robot arm is mounted.       

   Preferably, the gimbal is a universal type joint. Alternatively, the gimbal may be a spherical type joint. 
   Optionally, the movement unit further includes
         a mounting unit with limited movement in one direction;   shock absorbing means for absorbing forces between the attachment element and the mounting.       

   According to a further aspect of the present invention there is provided a mooring robot as described above, wherein the vacuum cup assembly is attached to the robot arm by a universal joint permitting limited rotation of the vacuum cup assembly relative to the robot arm perpendicular to the axis thereof. 
   According to a further aspect of the present invention there is provided a mooring system for releasably fastening a first moveable object to a second nearby object, said system including at least two mooring robots, each being substantially as described above. 
   According to a further aspect of the present invention there is provided a mooring system for releasably fastening a first moveable object to a second nearly object as described above, wherein said first object is a vessel and the second object is a dock, and wherein the mooring robots are mounted on the front face of and below the top of the dock and are retractable within a fender line fixed to the dock. 
   Optionally, the mooring robots may be mounted on the top of the dock or below the dock. 
   According to a further aspect of the present invention there is provided a mooring system for releasably fastening a first moveable object to a second nearby object as described above, wherein said first object is a vessel and the second object is a dock, and wherein the mooring robots are mounted on the front face of and below the top of the dock and are retractable within a fender line fixed to the dock. 
   According to another aspect of the present invention there is provided a mooring system including two or more mooring robots as described above wherein the control and monitoring of the mooring robots is performed by a control system linked to the ship&#39;s alarms. 
   Advantageously, this mooring device is simple and effective to operate and maintain, is free of interference with equipment and mechanisms utilised in the loading and unloading operations, and requires minimum care or adjustment when in use. 
   The mooring system also has the advantage of eliminating the need for close-in manoeuvring on departure from the dock as the mooring robots can be used to push a vessel clear of the dock. As with the mooring process, the departure is automated and can be remotely controlled. 
   Additionally, the use of resilient restorative forces in the horizontal plane and the resultant degree of control over vessel movement when docked, said vessel movement resulting from externally applied forces, is greatly increased over the prior art mooring devices. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: 
       FIG. 1  is a three-dimensional schematic view of a robot arm a first preferred embodiment of a mooring robot of the present invention; 
       FIG. 2  is a pictorial view of the first preferred embodiment of the mooring robot of the present invention; 
       FIG. 3  is an exploded view of the mooring robot of  FIG. 2 ; 
       FIG. 4  is a side elevation of a second preferred embodiment mooring robot of the present invention; 
       FIG. 5  is a front elevation of the mooring robot of  FIG. 4 ; 
       FIG. 6  is a plan view of the mooring robot of  FIG. 4 ; 
       FIG. 7  is a side elevation of the first preferred embodiment of the mooring robot fixed to a dock, and 
       FIG. 8  is a plan view of mooring device of the present invention. 
   

   BEST MODES FOR CARRYING OUT THE INVENTION 
   Referring to  FIG. 1 , a first preferred embodiment of a mooring robot  100  of the present invention (illustrated schematically) is fixed to a dock  50  and may be fastened to the hull  51  of a vessel by means of vacuum cups  1 . The mooring robot  100  includes a robot arm  10 , having three degrees of translational freedom for positioning the vacuum cups  1  anywhere within a three-dimensional operating envelope  20 . The robot arm  10  provides a telescoping movement along axis Z and is fixed at one end in a gimbal  11  for rotation about two orthogonal axes X and Y, which are substantially vertical and horizontal respectively. 
     FIG. 2  illustrates this first preferred embodiment of the mooring robot  100 , which includes a mounting frame  30  fixed to the dock  50 . The robot arm  10  is fixed by means of the gimbal  11  ( FIG. 1 ) to the mounting frame  30 , and protrudes through a vertically extending aperture  33  in a sub-frame  31  which is slidably connected to the mounting frame  30 . The sub-frame  31  provides generally horizontal actuation of the robot arm  10  and has a limited degree of sliding movement along a horizontal axis relative to the mounting frame  30  and includes a pivotally mounted collar  34  (see also  FIG. 3 ) defining the aperture  33 . 
     FIG. 3  is an exploded view of the mooring robot  100 , wherein each vacuum cup  1  has a circumferential seal  2  which is presented towards the hull  51  (FIG.  1 ). The seal  2  is of a type described in the co-pending U.S. patent application 10/220,010 which is based upon New Zealand Patent application No. 501394 (which description is incorporated herein by reference). Attached vacuum piping, valving, vacuum source and controls etc are not shown, for clarity. The vacuum cups  1  are arranged in a horizontal array supported by a horizontal member  4 . Member  4  is a hollow section and also acts as a vacuum reservoir for the cups  1 . In order to allow the vacuum cups  1  to conform to the shape of the hull  51  and to accommodate rotational displacement of the vessel, member  4  is mounted to the robot arm  10  about a universal joint  5 , for rotations perpendicular to the axis of the robot arm  10 . The collar  34  is pivotally fixed to the sub-frame  31  by bearings permitting rotation about a vertical axis V. The vacuum cups  1  are fixed to the member  4  by pivots  6  providing limited rotation of the vacuum pads  1  about a generally vertical axis. 
   The telescoping movement of the robot arm  10  is driven by a double acting hydraulic ram  21 , having a position transducer  122 . The robot arm  10  is pivoted about the axis Y to provide generally up and down movement of the vacuum cups  1 . This is controlled by a double-acting hydraulic ram  22 , both ends of which are pivotally fixed, one end to the mounting frame  30  the other end to the robot arm  10 . Rotation about the axis Z generally provides fore-and-aft movement and is controlled by a double-acting hydraulic ram  23 , one end of which is fixed to the mounting frame  30  the other end to the sub-frame  31 . Rotary position transducers  37 ,  38  are fitted about the gimbal  11  for sensing rotation about axes X and Y respectively. 
   The hydraulic system (not shown) for actuating the rams  21  and  23  for controlling the position of the vacuum cups  1  in the horizontal plane includes a hydropneumatic accumulator for storing excess energy when the pressure in the rams  21  and  23  rises and releasing it when the pressure falls. Both sides of each double acting ram  21  and  23  are connected to the accumulator through control valving. The valving allows the accumulator to be cut in or out of the system as a whole and includes means for sensing which side of the ram  21  and  23  is pressurised by mooring forces and directing fluid from the pressurised side to the accumulator. Both sides of ram  22  are provided with valving which, when opened, allows fluid to flow freely to and from a hydraulic reservoir, thereby providing a “free-floating” operational mode. 
   A second preferred embodiment of the mooring robot  200  is shown in  FIG. 4 , wherein the three degrees of translational freedom are provided by means of a cylindrical coordinate-type movement depending on two translational motions and one rotation. A pair of robots  200  is shown, each having vacuum cups  1  connected to a telescopic robot arm  210  for linear movement along axis Z thereof. The robot arm  210  is pivotably fixed to a carriage (not shown) for rotation about a vertical axis X and the carriage itself may be moved along a vertical axis A. 
     FIG. 5  shows vertical columns  90 , in which the carriage (not shown) moves, the columns  90  extend above and below the surface of the dock D. Each carriage is counterweighted by means of cables  94  fixed through pulleys  91  to counterweights (not shown), and is driven both up and down by means of a looped drive cable  92  connected to a winch  93 . 
   Referring to  FIG. 6 , adjacent to each column  90  is a tube  95  extending vertically and enclosing the counterweight (not shown). A pair of wheels  98  on either side of the carriage  97  carry it in the column  90 . The carriage  97  has a pivot  99 , defining axis X, about which the robot arm  10  is pivoted by means of a double-acting hydraulic ram  223 . The robot arm  210  is telescoped by a double-acting hydraulic ram  221 . The rams  221 ,  223  are connected to a hydropneumatic accumulator, in the manner described above. 
   With reference to  FIG. 7 , the first preferred embodiment of the mooring robot  100  is shown mounted to a fixed dock  50 . A range of sizes of ship S may be accommodated by the dock  50 , which may be fixed or floating. 
   A mooring system  500  preferably includes two or more mooring robots  100 , as described above. Optionally the mooring system may include robots  200  or both robots  100  and  200 . Optionally energy-absorbing fenders F, of the known type may be retained at intervals along the front face of the dock  50 . The mooring robots  100  are mounted on the front face and below the top of the dock  51  so as not to interfere with loading and unloading operations. It will be appreciated that the mooring system  100  may equally be fixed to a ship S, permitting the ship S to be made fast to a surface attached to the dock  51  or another ship S. 
   In the mooring system  500  several mooring robots  100  are connected by service lines  131  to a single power/control unit  30  mounted on the dock  50 . The power/control unit  30  provides control signals to the mooring robot  100  and provides means to power the rams  21 ,  22 ,  23  ( FIG. 3 ) and the vacuum cups  1  (FIGS.  1 - 3 ). It also receives feedback signals indicating the operating conditions of each mooring robot  100 . Positional feedback indications from the mooring robot  100  can be provided to other systems, for example, automatic loading systems which require information on the position of the ship S. Preferably the mooring system  100  operates automatically in the sequence to be described below, this operation being controlled remotely from the shore or the ship S by a unit  32 . 
   The operation of the mooring robot ( 100 ,  200 ) is described herein below with reference to  FIGS. 7 and 8 . To make fast a ship S the mooring arm ( 10 ,  210 ) is extended generally perpendicular to the front mooring face of the docked area In operation, when the ship S draws near to the dock  50 , the robot arm ( 10 ,  210 ) extends the vacuum cups  1  out toward the hull of the ship S. The ship S is positioned so that the vacuum cups  1  engage a planar section of the hull. 
   The assumption that the ship side is substantially planar is not critical to the operation of the mooring robot ( 100 ,  200 ) since the pivots ( 5 ,  3 ) allow the vacuum cups  1  to rotate to conform to the curve of the hull of the ship S. Although some vessels have slightly rounded sides for greater seaworthiness, for most container ships (in particular) this assumption is valid, except possibly near the bow and stern of the ship. This is because ships designed to stow containers have flat sides to use the space efficiently, and the bow and stern of the ship are not used for mooring. 
   Sensors of a known type (not shown) indicate engagement with the hull. The vacuum cups  1  are then actuated to fasten to the ship S in the known manner. With both mooring robots ( 100 ,  200 ) fixed, the ship S is automatically moved into a docked position (not shown) maintaining it at a pre-set (but variable) distance clear of the dock  50 . This position is the preferred, or pre-determined operating position. 
   Referring to the first preferred embodiment, and  FIGS. 1-3 , the operation of each mooring robot  100  maintains the ship S, within certain limits in the docked position in response to changing conditions of wind, tide, swell and displacement. If each mooring robot  100  is too rigid to allow movement of the ship S fore-and-aft, athwart ship and also in pitch, roll, and yaw, then failure of the vacuum in the cups  1 , or of the ship&#39;s hull could occur. 
   On attaining the docked position (or pre-determined operating position), the hydraulic pumps for actuating the rams ( 21 ,  22 ,  23 ) are stopped, the accumulator is cut into the lines to the ram  21  and  23  and the vertical movement ram  22  is switched into free-floating mode allowing the mooring robot (and thus the ship S) to rise and fall with the tide, state of loading, etc. Once in the docked position, pressure is regulated on each side of the piston of the rams  21  and  23  such that movement of the robot arm  10  in any direction in the horizontal plane away from the docked position results in a proportional force acting to restore the arm  10  to the pre-determined operating position, and thus return the ship S to the docked position. 
   Movement in the horizontal plane from the predefined docked position will result in pressurising of the fluid in the accumulator which provides hydraulic pressure to the rams ( 21 ,  23 ) tending to restore the arm  10  to the pre-determined operating position and thus the ship S to the docked position. The maximum ram pressure, and hence the maximum load able to be applied to the vacuum cups  1 , is limited to a level safely below the load capacity of the vacuum cups  1 . Under severe conditions, if the travel of the rams  21 ,  22 ,  23  approaches its limit under maximum operating pressure, an alarm condition is indicated, allowing the ship&#39;s captain or port authorities to take emergency action. All other operating conditions are also monitored and preferably linked to the ship&#39;s alarms. 
   The ram  22  permits the ship S to rise and fall relative to the dock  51 . Optionally, the method of mooring the ship S includes a first step of initially selecting the height of the vacuum cups  1 , depending on the state of the tide and state of loading of the ship S. The ram  22  is then operated to move the cups  1  to that height. In this way the vertical travel necessary to accommodate the full range of ships S may be reduced. 
   Referring to  FIGS. 4 &amp; 5 , in the operation of the second preferred embodiment of the mooring robot  200 , the resilient action in the horizontal plane is accomplished in a similar manner to that described above for the first preferred embodiment of the mooring robot  100 . The two rams  221  and  223  are connected to an accumulator. Vertical movement of the carriage  97  is controlled by allowing the mooring robot  200  to rise and fall freely. It will be appreciated that the mooring robot  200 , as compared to mooring robot  100 , provides an increased vertical range of operation and is thereby able to accommodate a wider variations in this direction, due to load and tidal flow etc. 
   The mooring robots  100 ,  200  may optionally include means for absorbing and/or resiliently buffering substantially vertical mooring forces for providing the increased stability, particularly with respect to roll and pitch of the ship S. For example, this may be provided by means of shock absorbers (not shown) connected to the robot arm  10  or may be provided through the actuating elements controlling vertical movement—the ram  22  and winch/cable  92 ,  93  in the two preferred embodiments respectively. 
   Even providing for the resilience as described, the ship S is more rigidly held in the docked position by these mooring systems ( 100 ,  200 ) than by the traditional (mooring line) method. Also, not only are paint abrasion and impact damage to the ship S prevented, but this increased stability is also advantageous when transferring cargo between the ship S and shore. Additionally, it has been found in practice that the mooring system ( 100 ,  200 ) consumes less energy to moor a ship S than systems using automatic tensioning devices to control mooring lines. 
   The mooring system ( 100 ,  200 ) also eliminates the need for close-in maneuvering on departure from the dock  51  as the mooring robot  100  can be used to push the ship S clear of the dock  51  As with the mooring process, the departure is automated and remotely controlled by the unit  30 . 
   Whilst the invention has been described with reference to a fixed dock  50 , it will be appreciated that the dock may be a floating dock or that the dock may be replaced by a second vessel. Similarly the above invention has been described with the mooring system  500  afixed to the dock  51 . It will be appreciated that the mooring system may be afixed to the movable vessel. 
   Similarly, the above embodiment of the invention as embodied in a docking system for vessel, it will be appreciated that there are other applications for the invention; for example the docking of one object to another under water, or in other environments. In such situations it will be apparent that he use of the term ‘horizontal’ plane is not limiting; but is used by way of reference to assist in defining the plane of restorative movement relative to the orientation of the object being dock and/or relative to any constant force (in the example above, gravity) 
   Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.