Smart tagline system and method for motion control of a suspended object

Abstract

A system for compensating motion of a load (46, 47) that is suspended from a suspension point on a boom (34) of a crane (28). The boom (34) is rotatable over a luffing angle (γ1) and / or a hoisting distance (H) between the load (40, 46, 47) and the suspension point (48) is adjustable. The system includes two taglines (44, 45) for exerting tensile forces on the load in directions towards the boom, two guiding members (56, 57) defining respective exit points (58, 59) at or near the boom where the taglines extend towards coupling points (54, 55) on the load, a pose sensor (38) for determining a momentary pose of the load, and a controller (21) for controlling motions of the load in at least two selected degrees of freedom by dynamically and individually adjusting tensions in the taglines based on the momentary pose of the load, and by dynamically adjusting respective positions of the guiding members (56, 57) along the boom (34) in response to a change in the boom luffing angle (γ1) and / or in the hoisting distance (H), to maintain each of the taglines substantially parallel with a horizontal plane (Ph) during operation.

Description

Smart Tagline System and Method for Motion Control of a Suspended ObjectTechnical Field

[0001] The invention relates to a system and a method for controlling motion of a suspended load. Furthermore, the invention relates to a computer program product configured to perform the proposed method, and a computer readable medium comprising such a computer program.Background Art

[0002] Methods and systems for damping / minimizing motion of a load that is suspended from an installation vehicle and relative to a target are known in the art. A common method for stabilizing motion of a load suspended from a crane involves adding control wires to the suspended load (or a carrier frame, also known as a “lifting yoke” or “lifting tool”, attached to the load) and controlling the wires to dampen or mitigate the pendulation motion of the suspended load.

[0003] Precision is particularly important when installing or unmounting components within a constrained space or such as between enclosures or wall segments of e.g. a nacelle. The maximum accuracy a state of the art GPS / IMU measurement system may provide is typically in the order of multiple centimetres (e.g. in the order of 2-3 cm horizontally and ± 8-10 cm vertically).

[0004] Patent document EP1925582A1 describes a system and method for hoisting a wind turbine blade, including the use of a crane boom, a bearing wire and two control wires connecting the blade to the boom. The control wires are actuated by a winch arrangement for keeping the blade orientation substantially horizontal when it is lifted off the ground.

[0005] Patent document WO2015 / 165463A1 describes a method and a device for automatically controlling rotation and displacement of a load that is suspended from a main wire of a crane and guided by two taglines, using control signals to the tagline and main wire actuators based on signals relating to angles and angular velocities measured by an inertial measurement unit (IMU) on the load. These signals are processed in a control unit, which then calculates desired lengths of the taglines, and sends control signals to the actuators to control actual position of the load.

[0006] Patent document CN112027909A describes a hoisting control device for preventing rotation and swing of large offshore wind turbine blades, including a control and measurement feedback system that adjusts the pre-tension of the left and right steel ropes so that the wind turbine blades cannot swing and rotate during the lifting process until hoisting and installation is completed.

[0007] It would be desirable to provide a system and method that allows motion compensation control with improved selectivity and accuracy.Summary of Invention

[0008] Therefore, according to a first aspect, there is provided a system for compensating motion of a load when this load is suspended from a suspension point on a boom of a hoisting arrangement. The boom is rotatable over a boom luffing angle and / or a hoisting distance between the load and the suspension point is adjustable. The system includes two taglines, two guiding members, a pose sensor, and a controller. The two taglines are configured to extend from the boom to the load, and are configured to exert tensile forces on the load in directions towards the boom. The two guiding members define respective exit points at or near the boom where the taglines are allowed to extend from the boom in transverse directions towards corresponding coupling points on the load. The pose sensor is configured to dynamically determine a momentary pose of the load. The controller is configured to control motions of the load in at least two selected degrees of freedom (DOF) by dynamically and individually adjusting tensions in the taglines based on the momentary pose of the load, and by dynamically adjusting respective positions of the guiding members along the boom in response to a change in the boom luffing angle and / or change in the hoisting distance, in such a way as to maintain each of the taglines substantially parallel with a reference plane during operation.

[0009] The dynamic and individually controlled adjustments of tensions in the taglines to control motions of the load are, in addition to being based on the momentary pose of the load, also based on the momentary locations of the tagline exit points. The proposed system provides automatic closed-loop control wherein the momentary pose of the suspended load is measured and used as feedback by the control system, while maintaining of the taglines substantially parallel with the initially selected reference plane in response to a changing boom luffing angle and / or load hoisting distance helps preserving the initial selection of the two DOF along which motion control is to be exerted, by ensuring that the taglines stay close to their initially selected directions and thereby minimize the directional impact on the spatial interdependencies and required magnitudes of the tagline tensions to be applied when controlling motion (compensation) of the load when the luffing angle and / or height is being changed. The momentary pose of the load may be determined with respect to a reference frame associated with the hoisting assembly itself (e.g. with the boom), or with respect to an external reference frame (e.g. a quasistatic reference associated with the earth, or a reference associated with a target relative to which the load is being manoeuvred). In addition, the guiding members are dynamically controlled to move up (or down) along the boom in response to the load being hoisted up (or down) in substantially vertical direction (along the gravity vector) and / or in response to the boom tilt being increased (or decreased), in a way that ensures that the initial spanning directions of the two taglines remain substantially parallel to the preset reference plane at all times.

[0010] Preferably, the reference plane is a horizontal plane i.e. a plane substantially along the local earth surface and perpendicular to the local gravity vector. The phrase "maintaining the taglines substantially parallel with the reference plane" refers herein to holding both taglines in essentially the same orientation as the predetermined reference plane while only dynamically changing overall distance from that plane (or at least maintaining the taglines within slight tilt offsets to be considered sufficiently parallel to the reference plane as is realistically achievable when controlling the tagline exit points and tensions, i.e. within a orientation tolerance of ±5°, or ±21 / 2°, or possibly even within ±1 ° of the reference plane).

[0011] Alternatively, or in addition, the positions of the guiding members may also be adjusted in response to another orientational change of the boom, for instance when the boom rotates as a result of pitching and / or rolling motion of the vehicle (e.g. vessel) to which the hoisting assembly (e.g. crane) may be mounted.

[0012] Term “position” is used herein to refer to a three-dimensional set of coordinates or a translation vector relative to a given coordinate reference frame. The position of an object - or a representative point for this object like its centre of mass - may be represented in 3D space by a vector in B3. The term “orientation” is used herein to refer to the three-dimensional rotational state of the object around a predefined axis, which may either be expressed relative to the object’s own local reference frame or relative to an external reference frame. The orientation of an object may be represented in 3D space by orthonormal rotation matrices, Euler angles, roll-pitch-yaw angles, unit-quaternions, matrix exponentials, or any other known rotational representation that may be applied. The combination of the position and the orientation of an object is referred to herein as the “pose” of the object.

[0013] The term “wrench” (symbol w) is used herein to indicate a joint 6-vector representation of a net three-dimensional (3D) linear force vector (symbol F) and the net 3D torque vector (symbol M) acting on an object.

[0014] A "frame of reference" or "reference frame" refers to an abstract coordinate system for which the origin and orientation are specified by a reference point and directional unit vectors.

[0015] The terms "load" and "load assembly" are used herein in an interchangeable manner to refer to a composite object that is suspended with the hoist line from the hoisting arrangement, and which includes the specific load that is to be installed or moved (such as a rotor blade or other component) as well as the load carrier that is temporarily fixed to the specific load while carrier and specific load are suspended from the hoist line .

[0016] The term "line" (as e.g. in "hoist line" and "tagline") is used herein to refer generally to any kind of elongated connection like a wire, cable, chain, rope, cord, etc (or any plurality or combination thereof) and is assumed to be sufficiently strong to lift a load connected thereto and / or for controlling the pose of that load. The term “tagline” is used herein to refer to a line attached and configured to exert a pulling force on a suspended load for purposes ofcontrolling motions of the load (assembly / carrier) during handling operations. The tagline may be structurally composed of a single continuous line, a group of parallel lines, and / or a series of interconnected line segments. Irrespective of this structure, the tagline is assumed to have an off-axis flexibility that renders it unsuitable to exert a pushing force. The phrase "connected to the load (assembly / carrier)' may - but does not necessarily - mean that the end of the tagline is rigidly fixed to the load (assembly / carrier). Alternatively, the tagline may be passed through a sheave connected to the load (assembly / carrier) and then passed back to its original attachment point (e.g. the vessel) in for instance a double reeved configuration.

[0017] Any known mechanism may be used for adjusting a length of the tagline, such as for instance a winch around which part of the tagline is wound or a linear drive (e.g. a spindle or rack-and-pinion mechanism) to which a distal end of the tagline is attached. The term "winch" is used to refer to any machine or instrument for hauling or pulling and includes a drum or spool from / on which a line may be (un)wound by means of a rotational actuator, possibly powered by e.g. an electric, pneumatic, hydraulic, or combustion drive.

[0018] The term "tagline exit point" is used herein to refer to the point where a respective tagline exits the corresponding guide member (e.g. via a diverter sheave) and proceeds toward the load. A “tagline exit direction” is the direction towards which the tagline extends after departing from the corresponding exit point.

[0019] The term "decoupled" refers herein to a controlled way of adjusting the pose and / or orientation of the load (assembly) in such a way that generated movement of the load (assembly) in one selected direction of the two selectable DOFs does not induce or influence motion of the load (assembly) already taking place in the non-selected other DOF.

[0020] The term "dynamically measuring" refers herein to a repeated measurement i.e. continuous or intermittent sampling of one or more physical quantities or properties associated with the observed system, in order to produce a series of measurements that have a well- defined time ordering.

[0021] In an embodiment, both taglines are configured to extend substantially along a same tagline plane. In this case, the controller may further be configured to dynamically adjust the positions of the guiding members in response to the change in the boom luffing angle and / or change in the hoisting distance, to maintain the tagline plane substantially parallel with the reference plane during operation. The refence plane is preferably a horizontal plane, to allow the taglines to continuously exert tension forces substantially perpendicular to the gravity vector, also after and in response to a changing luffing angle and / or hoisting distance. The portion of tagline tensions (tensile forces) that can be effectively applied onto the load to induce translation and / or rotation along the two selected DOF is thereby maximized.

[0022] In embodiments, the controller is further configured to coordinate dynamic adjustment of tensile force magnitudes in the taglines and the positions of the guiding members, in order to dynamically control motion of the load in two spatial DOF. The two DOFsmay include a translational DOF (which for instance may be in a transverse direction in the assembly reference frame, or a horizontal direction in the external reference frame, in particular the earth reference frame), as well as a rotational DOF (which may for instance be around a nominal hoisting axis in a vertical direction). In this case, the controller may further be configured to calculate the tensile force magnitudes with a matrix equation constructed based on the momentary pose of the load and the momentary poses of the coupling points and the exit points relative to an assembly reference frame, to provide a decoupled motion control between the translational DOF and the rotational DOF.

[0023] The DOF-decoupling allows accurate motion (compensation) control of the suspended load in two specifically selectable DOF of the load and allows addressing each of these two DOF independently from the other of these two DOF. Selection and excitation of the load along one of these DOF thus avoids generating crosstalk and additional movement of the load along the other of the two selectable DOF.

[0024] Construction procedures carried out at large height may require a high accuracy (e.g. millimetre-precision) alignment and linking action. For instance, during insertion and fixing of a rotor blade or installation of a gearbox during wind turbine (de)construction, the proposed DOF-decoupling allows precise rotation (compensation) of a suspended wind turbine component (e.g. blade) in a horizontal plane and around a vertical axis, while at the same time allows suppressing unwanted translations of the component caused by external forces along the horizontal plane in a manner decoupled and independent from the rotation.

[0025] In embodiments, the controller is configured to calculate a desired distribution of momentary tensile force magnitudes for moving the load from a current load pose to a desired load pose.

[0026] According to embodiments, the pose sensor is configured to determine the momentary pose of the load, the momentary poses of the exit points, and the momentary poses of the coupling points relative to a boom reference frame, and wherein the controller is configured to calculate desired poses for the exit points for maintaining the taglines substantially in the reference (e.g. horizontal) plane, and to dynamically issue control signals to the guiding members to reposition into the desired poses.

[0027] In embodiments, the pose sensor includes an imaging sensor that is configured to acquire spatiotemporal image data of the load. The pose sensor may further include a processor configured to dynamically determine from the image data a momentary pose of the load with respect to the reference frame of the hoisting arrangement (e.g. boom reference), or to the external reference frame (e.g. earth reference or target reference).

[0028] Alternatively, any other known method for performing object matching may be used based on imaging or on point-cloud data (such as matching LIDAR-based point cloud data with a CAD or other type of 3D model).

[0029] In embodiments, the imaging sensor has a field of view that is sufficiently wide to allow concurrently capturing of the load and of the guide members within the same image data. Moreover, the field of view may be sufficiently wide to capture (part of) the target as well.

[0030] In embodiments, the field of view of the imaging sensor is adjustable. This adjustability may be achieved by rotating the field of view and / or by translating the imaging sensor relative to the boom in response to the change in the boom luffing angle and / or in the hoisting distance, in such a way that both the load and the exit points are maintained within view during the operation.

[0031] In embodiments including the imaging sensor, the guiding members may be provided with markers directed towards and located within a field of view of the imaging sensor. In this case, the imaging sensor may be configured to acquire the spatiotemporal image data containing both the markers and the load. Furthermore, the processor may be configured to dynamically determine, from the image data, momentary poses of the markers, and to derive therefrom the momentary poses of the exit points.

[0032] In embodiments, the guiding members include trolleys, and the boom includes tracks that extend substantially along the length direction of the boom. The track is configured to couple to a respective trolley and allow the trolley to be moved along the track while restricting trolley motion in directions transverse to the track.

[0033] Each of the trolleys may be provided with positional encoders configured to dynamically provide indications of momentary positions of the trolleys relative to the corresponding tracks. In this case, the processor may be configured to dynamically determine, from the indications of momentary positions, the momentary poses of the exit points.

[0034] In embodiments, the hoisting arrangement includes an inertial measurement unit (IMU), configured to measure a pose of the boom relative to an external reference frame. In this case, the controller may be configured to dynamically determine, from the measured pose of the boom, the momentary positions of the hoisting arrangement, the load and the exit points with respect to the external reference frame.

[0035] In embodiments, the suspension point may be located at a jib portion of the boom that protrudes forward relative to a main portion of the boom, and the load may be suspended below the jib portion and in front of the main portion. In this case, the taglines may extend from the respective exit points on two lateral sides of a sagittal plane of the boom, and in transverse forward direction towards the load. In this case, the controller may be configured to dynamically adjust the tensile force magnitudes maintained in the taglines to keep the load deflected in transverse rearward direction towards the boom.

[0036] In embodiments, the hoisting arrangement includes a crane that is mounted on an offshore vessel, and the load includes one or more components of an offshore wind turbine.

[0037] In alternative embodiments, the hoisting arrangement includes a crane that is fixed to the earth, to a building, or to a wheeled or tracked vehicle, and the load includes any structural element, e.g. a prefab structural element of a land-based building or infrastructure.

[0038] According to a second aspect, there is provided a method for compensating motion of a load suspended from a hoisting arrangement, using a tagline system according to the first aspect.

[0039] In a further aspect, there is provided a computer program product configured to provide instructions to carry out the method according to the second aspect, when loaded on a computer arrangement.

[0040] Yet a further aspect pertains to a computer readable medium (for instance a non- transitory computer readable medium) comprising the computer program product according to the previous aspect.Brief Description of Drawings

[0041] Embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts. In the drawings, like numerals designate like elements. Multiple instances of an element may each include separate labels appended to the reference number (for instance “18a” and “18b”). The reference number may be used without an appended label (e.g. “18”) to generally refer to an unspecified instance or to all instances of that element.

[0042] Figure 1 schematically shows a perspective view of a motion compensation system according to an embodiment, which forms part of a jack-up vessel with crane used during construction of an offshore wind turbine.

[0043] Figures 2a and 2b schematically show a perspective view and a top view of the exemplary motion compensation system from Figure 1 ;

[0044] Figures 3a and 3b schematically show side view of a motion compensation system according to an embodiment installed in a crane oriented at different boom luffing angles;

[0045] Figure 4 schematically shows a perspective view of an exemplary guiding member forming part of the motion compensation system according to an embodiment;

[0046] Figure 5 schematically shows a perspective view of a motion compensation system with double-reeved taglines, according to another embodiment, and

[0047] Figure 6 schematically shows a component diagram for a control arrangement that forms part of a motion compensation system according to an embodiment.

[0048] The figures are meant for illustrative purposes only, and do not serve as restriction of the scope or the protection as laid down by the claims.Description of Embodiments

[0049] The following is a description of certain embodiments of the invention, given by way of example only and with reference to the figures.

[0050] Figure 1 schematically shows an embodiment of the proposed tagline system 20, which is configured to compensate motion perturbations of a suspended load 40 in two selected degrees of freedom (DOF) such that control in one of the two selected DOF is decoupled from control in the other of the two selected DOF. In this example, the system 20 is provided in a crane 28 that is mounted on an offshore jack-up vessel 22, which is deployed to install various components 14, 16, 17, 18 of a wind turbine 12 at sea 10. In the exemplary operation shown in Figure 1 , the system 20 is used to facilitate positioning of a suspended rotor blade 18c, to allow the blade to be mounted to a rotor hub 17 of a nacelle 16 that is part of the offshore wind turbine 12.

[0051] The exemplary vessel 22 is temporarily positioned in a fixed pose on the seabed by extending its four jack-up legs 24, so that a relation between a reference frame {Cv} associated with the vessel 22 and an external reference frame {CE} that is fixed with respect to earth remains (approximately) constant, at least during the installation procedure.

[0052] In this example, the crane 28 includes a fixed pedestal 30 that is mounted to a deck 26 of the vessel 22, and a turret 32 that is rotatably mounted to the pedestal 30 and configured to perform in-plane rotational motion (“slewing”) about a vertical slew axis Arp substantially perpendicular to a horizontal reference plane of the vessel deck 26. The crane 28 further includes a boom 34 that is rotatably coupled with its base 35 to the turret 32, such that the boom 34 may dynamically adjust its elevation angle (“luffing”) in upward-downward rotational directions about a transverse luff axis Ay and relative to the transverse plane associated with the deck 26 or a transverse plane associated with a vehicle chassis or earth-fixed base in case the crane 28 is land-based. This transverse plane may be in a fixed orientation (e.g. parallel or slanted) or be moving relative to the earth horizontal plane Ph.

[0053] A distal end of the boom 34 forms or is provided with a jib portion 36, which is inclined forwards relative to the main portion of the boom 34. A hoist line 42 is suspended at or near a distal end 37 of the jib 36. During installation, the suspended rotor blade 18c is rigidly held by a load carrier 47, which in this example is formed by a blade cradle. The suspended cradle 47 and blade 18c are jointly referred to as the load assembly 40. An upper portion of the cradle 47 is connected via the hoist line 42 to a suspension point at or near the distal end 37 of the jib 36. Depending on the required hoist line strength and acceptable hoisting speed appropriate for the type of load that is selected (e.g. a blade or a nacelle), the hoist line may alternatively be located at a mid-portion and / or at a proximal part of the jib. Typically, a main hoist with largest hoisting capacity is provided at a proximal end of the jib, an auxiliary hoist is provided at a medial section of the jib, and a whip hoist is provided at a distal end of the jib. The hoist line 42 is dynamically extendable / retractable, for instance using a winch mechanism (not indicated) that is controlled by an operator in / on the crane 28 or the vessel 22, in order to raise or lower the load assembly 40 as needed to move the blade 18c towards its mounting ring on the rotor hub 17.

[0054] The exemplary system 20 includes two taglines 44, 45. Each tagline 44, 45 extends upwards along a portion of the boom 34 and then makes a turn towards the load assembly 40 where the taglines 44, 45 are connected to corresponding coupling points (see Figures 2a-2b). The lengths of the individual taglines 44, 45 are independently and dynamically controlled by the system 20, to exert dynamically adjustable tensile forces on the load assembly 40 along substantially horizontal directions. This dynamic tagline control facilitates in stabilizing the pose of the load assembly 40 by dynamically counteracting externally induced motion disturbances of the vessel 22 and the load assembly 40, and / or facilitates in inducing a desired load motion to allow the load assembly 40 to approach a (possibly moving) target point on the wind turbine 12.

[0055] In the example of Figure 1 , an imaging sensor formed as a camera 38 is provided at or near the distal end 37 of the jib 36. The camera 38 is pointed with its field of view generally downwards along the boom 34, and is configured to acquire visual data of the load assembly 40 from a top / plan view perspective. The camera 38, alone or possibly combined with a processor device that receives the visual data from the camera 38, is configured to determine a pose (possibly in at least three of the three translational DOFs and / or three rotational DOFs) of the load assembly 40 in a reference frame {CB} of the boom. The boom reference frame {CB} may have its origin defined on / at / near the boom 34 and with determined orientations of orthogonal unit vectors relative to the boom 34. The camera 38 may additionally be configured to acquire visual data of the exit points where the taglines 44, 45 depart from the boom 34 towards the load assembly 40 and may be configured to determine the tagline exit directions.

[0056] Figure 2a schematically shows a perspective view of geometric relations between the crane 28, the hoist line 42 and taglines 44, 45, and the load assembly 40 in an embodiment of the proposed system 20. Figure 2b schematically shows a top view of the system shown in Figure 2a.

[0057] Again, merely for illustration purposes, the operation involves hoisting of a rotor blade 46, 18c, which is suspended from the crane 28 and held in a vicinity of a rotor hub 17 of a partially finished offshore wind turbine 12. The blade 46, 18c is held suspended by the blade cradle 47. An upper portion of the cradle 47 is connected at a hoist coupling point 49 to the hoist line 42. The hoist line 42 is held taut by the weight of the load assembly 40, and extends in a linear trajectory in a predominantly downward and slightly rearward direction from the suspension point 48 at the distal upper end 37 of the jib 36 to the coupling point 49.

[0058] The jib 36 is oriented with its nominal body axis Aj in a forwards slanted direction relative to the nominal body axis AB of the main part of the boom 34. In this example, the body axes Aj and AB form nominal centrelines of the jib 36 and boom 34, and jointly span a nominal sagittal plane Ps. This plane Ps generally extends in forward / rearward directions ±XB and upward / downward directions ±ZB of the boom reference frame {CB} and divides the boom 34and jib 36 into two lateral halves on opposite lateral sides of the plane Ps, corresponding with the lateral directions ±YB of boom reference frame {CB}.

[0059] The two taglines 44, 45 span from two respective exit points 58, 59 located on two respective guide members 56, 57 at the boom 34, towards two respective coupling points 54, 55 located on the cradle 47. The respective taglines 44, 45 are fixed to the cradle 47 at the corresponding coupling points 54, 55, so that the taglines 44, 45 are allowed to exert tensile forces F1 , F2 (vectors) with corresponding force magnitudes T1 , T2 on the load assembly 40.

[0060] The two guide members 56, 57 are attached to the boom 34 in a movable manner, which allows each guide member 56, 57 to move in a corresponding substantially linear trajectory along the boom 34 and predominantly parallel with the boom axis AB or predominantly parallel with the lateral bounding surface of the boom. In this example, the first guide member 56 and its corresponding exit point 58 is provided on one lateral side of the sagittal plane Ps, whereas the second guide member 57 and its corresponding exit point 59 is provided on the opposite lateral side of the sagittal plane Ps.

[0061] Each tagline 44, 45 is routed in a slidable or rollable manner (with low friction e.g. by a sheave) through a corresponding guide member 56, 57. The tagline 44, 45 is thereby divided into a lower section 50, 51 that runs along the boom 34, and an upper section 52, 53 that is deflected relative to the lower section 50, 51 , and which extends in substantially horizontal direction towards the load assembly 40. In this example, the lower tagline sections 50, 51 are routed downwards towards a respective tagline actuator 62, 63 (which in this example is located near the base 35 of the boom 34, but which may be located elsewhere in other embodiments). Each of the actuators 62, 63 may for instance be implemented as a tugger winch, which may be actuated by a dedicated electric or hydraulic drive or other wire reeling actuator means known in the art. In alternative embodiments, the actuators may be implemented as linear tagline extension / retraction mechanisms.

[0062] In the example of Figures 2a-b, each of the distal ends of the upper sections 52, 53 of respective taglines 44, 45 is provided with a tension sensor 64, 65 located at or near the coupling point 54, 55. The tension sensor 64, 65 is configured to dynamically measure the momentary magnitudes T1 , T2 of the tensile forces F1 , F2 applied by the respective taglines 44, 45 onto the load assembly 40. The tension sensors 64, 65 are configured to acquire (continuous or intermittently sampled) series of tension values as function of time.

[0063] In this example, both taglines 44, 45 are continuously controlled by the winches 62, 63 to apply inwards pulling forces F1 , F2 onto the suspended load assembly 40, such that the tensioned taglines 44, 45 pull and thereby displace the load assembly 40 away from a rest pose 40R that the suspended load assembly 40 would assume due to gravity but without tagline tensions or other external influences (Figure 2b). This pulling causes the load assembly 40 to move along an inwards direction -XB substantially parallel with a horizontalplane Ph (albeit with a slight upwards change in height) towards the boom 34 into an offset pose 40o.

[0064] In the exemplary arrangement shown in Figure 2b, the two taglines 44, 45 extend substantially in the same tagline plane Pt, but in a mutually slanted / oblique (i.e. non-parallel) and non-crossing constellation. In the example of Figure 2b, the taglines 44, 45 extend at respective slant angles p1 and p2 relative to lines in the tagline plane Pt that extend parallel with the sagittal plane Ps of the boom 34 and jib 36. The slant angles p1 and p2 may have substantially equal magnitudes but opposite signs p1 = -p2 (at least in an unperturbed equilibrium state, which may change during operation due to changing external influences like wind and wave motion).

[0065] A nominal coronal plane Pc of the load 46, which is shown in top view in Figure 2b, extends transversely through the hoist coupling point 49 and parallel with a nominal body axis AL of the load 46 and along a vertical direction along the momentary gravity vector Fg. In the example in Figures 2a-b, the taglines 44, 45, the coupling points 54, 55 and the guide members 56, 57 are in the same half-space on the side of the coronal plane Pc that faces towards the main portion of the boom 34. By contrast, the hoist suspension point 48 on the jib 36 is positioned on an opposite side of the coronal plane Pc away from the main boom portion 34.

[0066] Part of the gravitational force Fg that is not cancelled by the combined tensile forces exerted by the hoist line 42 and taglines 44, 45 will give rise to a restitution force, which urges the load assembly 40 back towards its rest pose 40R. In the absence of other external forces, the tensile forces F1 , F2, hoist force Fh and gravity Fg will cancel each other out, so that the load assembly 40 remains suspended in the predetermined offset pose 40o. However, any change to this equilibrium state (e.g. due to changing direction of gravity, tagline tensions, or other external disturbances), will result in a net wrench (i.e. force and / or torque) to be exerted on the load assembly 40. Relaxing both taglines 44, 45 allows the load assembly 40 to translate back towards the rest pose 40R, whereas tightening one tagline (e.g. 44 or 45) while relaxing the other tagline (e.g. 45 or 44) will allow the load assembly 40 to rotate about the coupling point 49. By dynamically adjusting the individual tagline tension magnitudes T 1 , T2, the inability of the taglines 44, 45 to exert pushing forces on the suspended load assembly 40 is overcome, and the motion compensation of the suspended load assembly 40 is also allowed to include outward deflection +Tx away from the boom and rotational motions ±Rz about a vertical axis Az ("yawing"). If such winch control is commanded in an open loop manner, however, no clean decoupling of two of two selected DOF will be possible, due to frictions and other non-linearities in the system. The pose sensor in combination with a closed- loop control method enables the precise decoupling of motions in two selected DOFs.

[0067] The tagline tension settings and resulting offset pose 40o are adjusted in real-time based on incoming sensor data at a relatively high dynamic rate, to ensure that the desiredinstantaneous offset pose continues to provide enough leeway for outward translational and rotational motions, as well as to ensure that the two selected motional DOFs remain addressable and excitable in a mutually decoupled manner.

[0068] The computation of the desired tagline tension magnitudes T1 , T2 to be applied by each winch 62, 63 relies, in part, on the momentary pose of each tagline exit point 58, 59 at the boom 34 and the momentary pose of each tagline coupling point 54, 55 at the load assembly 40 as well as on the momentary pose of the load assembly. From these point poses, analytic matrix equations may be constructed for computing the desired tagline tension magnitudes, which take as input a vector of desired wrench components to be exerted on the load.

[0069] Figure 2a further illustrates that the exemplary system 20 includes a control device 21 or 80 (see e.g. Figure 6), which is in signal connection with the tension sensors 64, 65 to receive measurement signals indicative of the momentary tensile force magnitudes T1 , T2 applied by the respective taglines 44, 45 onto the load assembly 40. The control device 21 / 80 is also in signal connection with the winches 62, 63, and is configured to actuate the winches 62, 63 to reel the corresponding tagline 44, 45 out or in, thereby increasing or decreasing the wire length of the corresponding tagline 44, 45. The control of each winch 62, 63 is configured to proceed in a concurrent but mutually independent manner, that is, the tagline lengths may be adjusted simultaneously but with mutually different magnitudes and directions.

[0070] Functionality of the proposed tagline system 20 may be coupled or integrated with an existing control system of the crane 28 (schematically illustrated by element 21 in Figure 1), to allow a crane operator to control luffing / slewing motions of the crane 28, hoisting and motion compensation of the suspended load assembly 40 together via a single user interface (e.g. at an operator console).

[0071] The system 20 further includes an imaging sensor 38 configured to acquire spatiotemporal image data of objects within its field of view 67, either continuously or intermittently at know time instances. In this example, the sensor is formed by a photogrammetric camera 38 arranged at the tip 37 of the jib 36. This camera 38 may be mounted - either by a fixed or repositionable mounting (e.g. gimbal or pan-tilt drive) - to point substantially downwards towards the load assembly 40, and to maintain at least an upward portion of the load carrier 47 and / or load 46 in its field of view 67 during operation. Preferably, this view onto the load carrier 47 and / or load 46 is maintained from load-out at the quayside, during pick-up above deck, and up to and including the installation of the load 46.

[0072] A sensor reference frame {Cs} may be defined by a determined origin on / at / near the camera 38, and with a determined orientation and scale relative to the sensor output (e.g. images) produced by the camera 38 during use. The camera 38 may be configured to detect objects discernible in the acquired images and to determine momentary poses of these objects relative to its sensor reference frame {Cs}. Alternatively, the camera 38 may beconfigured to transmit the acquired images to an associated image processor which is configured to post-process the images to determine momentary poses of the objects in the images, relative to the sensor reference frame {Cs}.

[0073] Figure 2b schematically shows a peripheral contour of the camera field of view 67 at a height corresponding with the tagline plane Pt. By positioning the camera 38 high on the jib 36 and above the load assembly 40 - and by choosing appropriate settings and elements for the camera optics - the camera 38 may maintain a largely unobstructed view on multiple constituents of the tagline system 20. For instance, the camera 38 may have a field of view that is sufficiently wide (e.g. by using a fisheye lens) to allow the load carrier 47, (part of) the load 46, the guide members 56, 57, and possibly also (part of) the target 12 to be simultaneously captured within the same image. In this way, the camera 38 and / or the image associated processor may concurrently detect each of these objects in the same image and may determine the poses of each object relative to the camera reference frame {Cs}.

[0074] The camera 38 is configured to dynamically acquire spatiotemporal image data of the load assembly 40. The camera 38 and / or image processor may further be configured to derive momentary poses of the suspended load assembly 40 relative to the sensor reference frame {Cs} at successive times. The control device 21 is in signal connection with the imaging sensor 38 and / or the image processor, to receive the derived momentary poses of the suspended load assembly.

[0075] A load reference frame {CL} may be defined by a determined origin on / at / near the load assembly 40, and with a determined orientation and scale relative to the load assembly 40. The momentary position of each tagline coupling point 54, 55 on the load assembly 40 may be expressed as a positional vector relative to the load reference frame {CL}.

[0076] In an embodiment, the load carrier 47 is provided with a known pattern of active and / or passive markers 68, and the camera 38 is configured to maintain an unobstructed view on this marker pattern 68. The camera 38 may be configured to detect the marker pattern 68 in the acquired images, to determine the momentary poses of the markers 68, and to use these poses to derive the pose of the load carrier 47 and of the tagline coupling points 54, 55 relative to the sensor reference frame {Cs}. Since the markers 68 remain fixed on the load carrier 47 during operation, their relative positions may be defined beforehand with respect to the load reference frame {CL}. The positions of the coupling points 54, 55 may also remain fixed relative to the load reference frame {CL} during operation. The load carrier 47 with markers 68 and coupling points 54, 55 may be surveyed beforehand (for instance by the camera 38 or by a total station) to establish the required transformation from the markers to the load reference frame {CL}. Moreover, the camera 38 may be surveyed and calibrated to determine its internal image calibration parameters, such as the focal length, horizontal and vertical sensor offsets, radial lens distortion or any other known camera calibration parameter. The locations of the markers 68 and momentary pose of the suspended load assembly 40derived from the acquired image may then be used to transform the positions of the tagline coupling points 54, 55 (which are known in the load frame {CL}) into the sensor reference frame {Cs}, for each time that the camera 38 has acquired an image e.g. using known marker matching techniques. Alternatively, a marker-less method may be used that relies on image segmentation and / or edge detection techniques, to detect the pose of the load carrier 47 in the relevant DOFs.

[0077] The coordinate transformation from sensor reference frame {Cs} to boom reference frame {CB} may also be determined offline by surveying (e.g. using a total-station). In cases wherein the pose of the image sensor 38 remains fixed relative to boom reference frame {CB}, a constant transform may be found that can be applied to transform any image-based measurements expressed within in sensor frame {Cs} into a measurement expressed in boom frame {CB} at each sample instant. In the example of Figure 2a, the crane 28 includes an inertial measurement unit (IMU) 66, which is coupled with a GNSS receiver and configured to measure a current pose of the boom 34 relative to the external reference frame {CE}.

[0078] In the example shown in Figures 2a-b, the guide members 56, 57 are implemented as trolleys (i.e. cart mechanisms) that are arranged to be moved in a controlled manner up and down along guiding tracks 60, 61 , which in this example are formed by rigid rails 60, 61 provided along the length of the boom 34. As alternatives to using wheeled trolleys and rail bars, the guiding members and guiding tracks may be implemented using, spindle or rack- and-pinion mechanisms, telescoping members, or any other guiding track arrangement known in the art. The mechanically rigid character of the rails allows accurate determination of momentary linear positions of the guide members 56, 57 during operation.

[0079] The momentary positions of each tagline exit point 58, 59 may be expressed as a positional vector relative to the boom reference frame {CB}. The reference starting positions and full range of possible positions of the tagline exit points 58, 59 may be determined through prior survey measurements. The (changing) momentary positions assumed by the exit points 58, 59 along the boom during operation may then be followed as function of time by online measurement of positional changes using calibrated displacement sensors (e.g. Figure 4) and / or by online measured using remote sensing techniques.

[0080] Alternatively, or in addition, the trolleys 56, 57 may also be provided with trolley markers 70, 71 , and the camera 38 may be configured to detect the trolley markers 70, 71 in the acquired images, and to measure the respective poses of the trolley markers 70, 71 directly in the sensor reference frame {Cs}, concurrently with the pose detection of the load carrier 47 (and attached load 46). Suitable transformations for re-expressing the measured trolley poses in sensor reference frame {Cs} into the boom reference frame {CB} and possibly into the external reference frame {CE} may be determined via similar procedures as described above for the load marker measurements.

[0081] The proposed system and method allow the motions of the load 46 and load carrier 47 to be stabilized against external disturbances, such as for instance induced by winds, by dynamically and individually controlling the tensions applied by the taglines as well as the positions of the tagline guide members on the boom. Additional motion control can be superimposed, as will be explained with reference to Figure 6.

[0082] In embodiments, also the target 12 may be equipped with an inertial measurement unit (IMU) combined with a GPS system, configured to derive the pose of the target 12 and associated reference frame {CT} relative to the external reference frame {CE}. Such embodiments may additionally allow the load 46 and carrier 47 to be automatically aligned with the target 12 if such sensors are in signal connection with the controller. For instance, in examples were the suspended load 46 is a turbine blade 18c and the target 12 is (part of) a rotor hub 17 of a wind turbine nacelle 16 onto which the blade 18c is to be mounted, the target reference frame may for instance be placed near a bolt (hole) on a pitch ring adapter of the rotor hub 17. The suspended blade 18c should first be aligned with the bolt (hole) before fixing the connection.

[0083] Figures 3a and 3b illustrate an exemplary operation of the proposed system in which the boom 34 of the crane 28 assumes considerably different luffing angles y1 , y2 and the load assembly 46, 47 may be moved to a different hoisting distance H during different operational phases, while the load assembly 46, 47 continues to be held with position offset towards the boom by pre-tensioning of the two taglines 44, 45 (e.g. offset 40o in Figure 2b) and while the taglines 44, 45 are maintained substantially parallel with the initially reference plane Ph, which in this example is a horizontal plane perpendicular to the gravity vector Fg. The boom 34 is rotatable over variable luffing angles y relative to a transverse plane Pv associated with the pedestal 30 or a fixed platform (e.g. the deck 26) of the vessel 22. Furthermore, a vertical distance between the suspension point 48 on the boom jib 36 and the coupling point 48 on the load carrier 47 is referred to as hoisting distance H, which is also dynamically adjustable by changing a length of the hoist line 42.

[0084] Figure 3a shows a phase wherein the boom 34 is rotated downwards and held at a first luffing angle y1 that is relatively small, so that the load 46' may be picked-up by the load carrier 47 from a deployment platform (e.g. a deck of the same or another vessel, or a loadout area in a port). The first luffing angle y1 may be maintained while the hoist line 42 is retracted, so that the load carrier 47 and load 46 move upwards and the hoisting distance H decreases.

[0085] The taglines may alternatively also be (temporarily) applied to a lower hoist block of a crane directly, without a load assembly attached, in order to avoid swinging motions of such a hoist-block on a vessel prior to attaching a load assembly.

[0086] The guide members 56, 57 are configured to be dynamically repositioned upwards along the rails 60, 61 of the boom 34 while the hoisting distance H decreases, and configured to be moved downwards along the rails 60, 61 of the boom 34 when the hoisting distance Hincreases. The upwards or downwards repositioning of the guide members 56, 57 causes a nominal plane Pt spanned by the two taglines 44, 45 to be held substantially aligned with the horizontal plane Ph of the external reference frame {CE} while the distance H changes. The displacement lengths of the guide members 56, 57 along the boom 34 may for instance be (approximately) proportional to the instantaneous value of the hoisting distance H and inversely proportional to the sine of the instantaneous luffing angle y.

[0087] Figure 3b shows another phase wherein the boom 34 is rotated to a large luffing angle y2, so that the load 46 may be held suspended in a motion-compensated manner and at considerable altitude near the intended mounting point on the target 12 (Figure 1). The guide members 56, 57 are additionally configured to be dynamically repositioned in response to a changing boom luffing angle y. Also in this case, the repositioning ensures that the nominal plane Pt spanned by the two taglines 44, 45 remains substantially aligned with the horizontal reference Ph while the luffing angle y changes.

[0088] In addition, the tagline system 20 may be configured (e.g. by means of the control device 21) to dynamically reposition the guide members 56, 57 along the boom while both the boom luffing angle y and the hoisting distance H are changed, to maintain the two taglines 44, 45 substantially aligned with the horizontal plane Ph perpendicular to the local gravity vector Fg.

[0089] By maintaining the taglines 44, 45 substantially parallel with a horizontal plane Ph, the initial tension exerted on the load assembly 40 may be kept essentially constant, both in magnitude and in direction, while the boom 34 proceeds through varying luffing angles y and / or the load assembly 40 changes hoisting distance H. As a result, the possibility to control the two selected motional DOFs of the load assembly 40 independently and in a decoupled manner between the two selected DOFs, remains available during different values for the hoisting distance H and the luffing angle y. The same applies to potential other orientational changes of the vessel, e.g. during roll when an embodiment is used on a floating vessel that rolls around its longitudinal axis or in any other direction of motion that may be caused by a moving vehicle.

[0090] In addition, the camera 38 may be configured to maintain both the load assembly 40 and the guide members 56, 57 on the boom 34 within its field of view 67 while the boom 34 progresses through various luffing angles y. In this way, the camera 38 may track the momentary poses of the guide members 56, 57, to allow the tagline system 20 to correct the positions of the guide members 56, 57.

[0091] In addition, the system 20 (e.g. control device 21) may be configured to dynamically command the winches 62, 63 to reel in or out, in order to (concurrently but independently) change the lengths of the taglines 44, 45 in conjunction with the commanded positional changes for the guide members 56, 57, in order to compensate for changes in tagline path lengths from the respective winch 62, 63 via the guide member 56, 57 to the load assembly40, and to ensure that the exerted tensile force magnitudes T1 , T2 remain essentially constant.

[0092] Figure 4 shows an example of a displaceable trolley, which may form one or both of the guide members 56, 57. The trolley 56, 57 may be in signal connection with a controller (e.g. by the control device 21), to allow the trolley to be commanded to travel selectively up or down along a guiding track 60, 61 that extends predominantly parallel to the nominal body axis AB of the boom 34. In this example, the guiding track is formed as a rigid guiding rail 60, 61 along the boom 34.

[0093] In this example, the trolley 56, 57 includes a bracket or frame structure 72 and a swivel block 74 with sheave 78. The swivel block 74 is rotatably connected to the bracket 72, to allow the block 74 and sheave 78 to jointly pivot about a nominal yawing axis Aw that coextends largely or fully with longitudinal direction of the guiding track 60, 61 (which may coincide with the boom body axis AB). Other embodiments of the trolley may include an additional or different pivot axis, such as a roll axis.

[0094] The sheave 78 supports and redirects the tagline 44, 45 along parts of its angular periphery, such that the tagline 44, 45 forms a first section 50, 51 that extends largely downward along the boom, and a second section 52, 53 that extends from the respective exit point 58, 59 towards the corresponding coupling point 54, 55 on the load assembly 40. The sheave 78 is rotatably coupled to the swivel block 74 about an axle Aqj to allow the sheave 78 to rotate in both angular directions ±qj, thereby reducing friction while the tagline 44, 45 passes through the trolley 56, 57 when the length of the tagline 44, 45 and / or the position of the trolley 56, 57 along the boom 34 changes.

[0095] In this example, the bracket 72 and swivel block 74 are attached to the rail 60, 61 via three rollers 73a-c, which enclose the rail 60, 61 from opposing radial sides. An drive actuator 75 with gearbox may be provided, which is linked to drive the rotation of one or more of the rollers 72 so as to move the entire trolley 56, 57 up- or down along the rail 60, 61 . The rollers 73 and / or the actuator 75 may include a brake mechanism 76, which is configured to temporarily lock the trolley 56, 57 in place at a determined position along the rail 60, 61 , without consuming energy / power for maintaining this lock, and further configured to release this lock to allow the trolley 56, 57 to move to a different position along the rail 60, 61 . In embodiments wherein the positions of the trolleys 56, 57 are independently controllable, the brake mechanism 76 for each respective trolley 56, 57 may also be separately actuatable.

[0096] The trolley drive 75 may be equipped with a position encoder 77, which is configured to generate trolley position signals indicative of the momentary linear displacement of the trolley 56, 57 along the rail 60, 61 and relative to the boom 34 with respect to a starting position. The location of the trolley starting position and the encoder-vs-displacement characteristic relative to the boom reference frame {CB} may be determined in advance, e.g. via calibration and survey measurements.

[0097] The trolley position signals may be transmitted to the controller (e.g. 21), which may be configured to determine actual momentary pose of the trolley 56, 57, based on the received trolley position signal acquired at each time, in combination with the known starting position and displacement characteristic.

[0098] Figure 5 depicts an embodiment of the tagline system 120 wherein the taglines 144, 145 are double-reeved. Features in the system 20 that have already been described above with reference to the arrangements in figures 1-4 may also be present in the system 120 shown in figure 5 and will not all be discussed here again. For the discussion with reference to figure 5, like features are designated with similar reference numerals preceded by 100 to distinguish the embodiments.

[0099] Each of the two taglines 144, 145 is composed of outgoing sections that depart from the respective tagline actuator (e.g. winches) towards and through the corresponding displaceable guide member (e.g. trolleys) and further towards the load assembly, as well as of returning section that depart from the load assembly, back towards and through the corresponding displaceable guide member, and further towards a point near the respective tagline actuator. Each respective outgoing section belonging to the same tagline predominantly co-extends with the corresponding returning section of that same tagline.

[0100] As an example, Figure 5 illustrates that an outgoing first section 150a of the tagline 144 departs from the tagline actuator 162 towards the displaceable guide member 156, and then proceeds as outgoing further first section 152a towards the first coupling point 154 on the load carrier 147. In this embodiment, the first coupling point 154 is formed using a low-friction rolling or sliding coupling (e.g. a snatch-block with a pulley) that allows the first tagline 144 to be routed back as a returning first further section 152b. This returning first further section 152b runs from the load carrier 147 back towards and through the displaceable guide member 156, and then proceeds as returning first section 150b back towards a fixed point near a base of the tagline actuator 162. The outgoing first section 150a substantially co-extends with the returning first section 150b generally along the boom, whereas the outgoing first further section 152a substantially co-extends in a horizontal plane with the returning first further section 152b of the tagline 144. Similar properties apply to the various sections of the second tagline 145, which will not be repeated here in detail.

[0101] In the example shown in Figure 5, load sensors 164, 165 (for instance a load-pin) is provided between the coupling points 154, 155 and the load carrier 147. The load sensors 164, 165 are configured to dynamically measure momentary magnitudes T1 , T2 of the pulling forces F1 , F2 exerted by the taglines 144, 145 on the load carrier 147, and to transmit the sensor readings to the control system 121 in real time.

[0102] Alternatively, or in addition, one or more further load sensors 179a-b for dynamically measuring the momentary pulling forces exerted by the taglines 144 (145) may be provided, for instance between the fixing points close to the tagline actuators 162 at / on / near the boom134, or incorporated in the tagline actuators 162 for instance as a load-pin on / in the actuator frame or gearbox or a sensor that dynamically measures the momentary power supplied to or torque applied by the tagline winding drum. Providing the further load sensors 179 at positions at / near the boom 134 allows the sensor readings to be transmitted to the controller 121 via wired connection, thereby reducing the probability of signal delays, jitter and noise associated with wireless transmissions.

[0103] In yet alternative embodiments, either one of or both the taglines may be single, double-, triple-, or quadruple-reeved, or have an even higher number of tagline sections going back and forth between the boom and the load assembly. In each case, providing the tagline actuator unit(s) and / or the load sensor(s) at or near the boom allows connecting the actuator unit(s) and / or load sensor(s) to the control device (e.g. 121) using wired signal connections.

[0104] Figure 6 shows a logical diagram with components and their interactions in an exemplary control arrangement 80 that is configured to control a tagline system, for instance one of the exemplary systems 20, 120 from Figures 1-5.

[0105] The arrangement 80 in Figure 6 is discussed with reference to system elements that are mentioned in the examples of Figures 1-4 (such as taglines 44, 45), but it should be understood that the elements may also be part of different system embodiments (such as the system from Figure 5 with taglines 144, 145, or any other system explicitly described or implied in the present document).

[0106] In the exemplary arrangement 80 of Figure 6, control of the tagline tension magnitudes T1 , T2 proceeds in conjunction with a closed-loop load control for the motion of the load assembly 40, which uses the measured poses of the tagline exit points 58, 59 on the boom 34 and measured poses of the tagline coupling points 54, 55 on the load assembly 40. Due to the presence of the two controllable taglines 44, 45, the use of the tagline configuration (and respective directions) based on knowledge of the tagline exit and coupling points (and hence their vector directions) in a single reference frame, and due to the dynamic adjustment for maintaining the tagline directions substantially constant with respect to gravity Fg during boom operations, the arrangement 80 allows concurrent but decoupled motion control of the load assembly 40 in two selectable DOF in a manner that allows the control parameters corresponding to excitation of a selected one of these two DOF to be calculated without creating excitation of the other of the two DOF. As a result, the induced motion of the load assembly 40 along the selected DOF will take place independently from the other DOF i.e. while avoiding causing motion of the load assembly 40 along the other of the two selectable DOF as well (i.e. "decoupled DOF excitation").

[0107] In the example shown in Figure 6, the control arrangement 80 includes a load trajectory calculator 82, a load motion controller 84, a tension and exit-point calculator 86, a pose sensor system 94 including an imaging sensor 38 and an exit point sensor 77 and / or 38,a trolley controller 98 coupled to two trolleys 56, 57, and a winch controller 102 coupled to two winches 62, 63 with tension sensors 64, 65.

[0108] The exemplary control arrangement 80 from Figure 6 is adapted to receive measurements that are continuously or intermittently acquired by various sensors in the arrangement.

[0109] The load trajectory calculator 82 is configured to calculate a desired pose of the load assembly 40 relative to a boom reference frame {CB}, or alternatively relative to an external reference frame {CE}, or alternatively relative to a target reference frame {CT}, based on measurement signals from a variety of sensors, and to calculate a desired spatial trajectory (or a set-point) and corresponding temporal sequence (or single instances) of desired poses 83 that the load assembly 40 ought to follow in order to move the load assembly 40 from a current pose toward a final desired pose during operation. Depending on the particular reference relative to which the load is to be moved in a motion compensated manner, and on the presence of sensors (e.g. IMU 66) for dynamically measuring spatial relations between various reference frames, the desired load poses 83 may be expressed relative to the vessel reference frame {Cv} (if an IMU is located on the vessel), relative to the (fixed) external reference frame {CE} (if e.g. an IMU is located on the boom directly), or to a reference frame {CT} of a target that may also be slowly moving in time (e.g. the top of a wind turbine 12) (if an IMU or image detection of target motion is in signal connection with the load trajectory calculator 82.

[0110] The load trajectory calculator 82 is in signal communication with various sensors provided on the crane 28 and configured to receive pose data 81 representing momentary orientation (or, if applicable, elevation) of the crane 28. This may include a sensor for measuring a momentary slewing angle (p and / or momentary luffing angle y of the boom 34 relative to the external reference {Cv} (or {CE} in case of a land fixed crane), and a hoist sensor for measuring a momentary height H between a coupling point 49 on the load assembly 40 and a suspension point 48 on the boom 34. A sensor may be included to measure elevation if a crane is configured to change its length, such as e.g. a telescopic boom crane. The load trajectory calculator 82 may additionally or alternatively receive pose / orientation data of a moving vessel 22 onto which the crane 28 may be mounted. From this momentary crane pose 81 , whether calculated directly from sensors on the boom or indirectly from vessel pose information, the load trajectory calculator 82 then calculates a desired load pose 83.

[0111] In embodiments, the various calculated desired load poses 83 may be expressed relative to the boom reference frame {CB}. In other embodiments wherein the system 20 includes means to determine momentary poses of the crane 28 relative to the external reference frame {CE}, the desired load pose 83 may be expressed directly in the external reference frame {CE}. The required coordinate transforms (as function of time) may bedetermined for instance based on measurements of an IMU 66 provided on the crane boom 34 and configured to express the pose of the boom 28 in coordinates of the external reference frame {CE}. In other embodiments wherein the system 20 includes means to determine momentary poses of the crane 28 and target 12. The desired load pose 83 may be expressed relative to the target reference frame {CT} (optional signal connection between imaging sensor 38 and load trajectory calculator 82 now shown in Figure 6).

[0112] The image sensor 38 of the pose sensor system 94 continuously or intermittently acquires spatiotemporal image data of the load assembly 40 (and potentially also of the trolleys and the target). From this image data, the pose sensor system 94 determines the momentary pose 95 of the load assembly 40 in real time, preferably at a rate comparable to the image sample rate (e.g. at a rate of several tens of Hertz e.g. 75 Hertz). Spatial transformation of the image data and / or pose data 95 from the sensor reference frame {Cs} to the boom reference frame {CB} may occur instantaneously, for instance by determining in advance the sensor pose relative to the boom reference frame {CB} through surveying techniques.

[0113] The image sensor 38 is configured to detect a marker pattern 68 on the load carrier 40, to generate the image data used for determining the momentary pose of the load assembly 40. In addition, the image sensor 38 may be configured to concurrently detect other marker patterns, such as the two marker patterns 70, 71 on each of the trolleys 56, 57, and / or the marker 69 on or near a point of interest on the target 12.

[0114] The load motion controller 84 is configured to compare the desired load pose 83 with the currently measured pose 85 of the load assembly 40 received from the pose sensor system 94 to form an error on which a controller acts. The load motion controller 84 derives therefrom a desired wrench 85 that should act on the load assembly 40 in two selected DOF (e.g. translations ±Tx and rotations ±Rz) in order to reposition it toward the desired load pose 83, which preferably includes an offset (e.g. 40o in Figure 2b).

[0115] The poses (e1 , e2) of the tagline exit points 58, 59 are caused to change dynamically during the operation, as a result of the proposed control methodology and in response to a change of the boom luffing angle y and / or a change of the hoisting height H. Furthermore, the poses (a1 , a2) of the tagline coupling points 54, 55 are expected to change dynamically during the operation with respect to e.g. the external reference frame {CE} or to the boom reference frame {CB}, caused by the various controlled and uncontrolled motions of the suspended load assembly 40.

[0116] The pose sensor system 94 is configured to determine, from the available data acquired by the imaging sensor 38 and from prior surveying, the momentary poses (a1 , a2) 96 of the coupling points 54, 55 in the load reference frame {CL}, and to re-express in real time these poses (a1 , a2) 96 via online transformations into the sensor reference frame {Cs} and into the boom reference frame {CB}.

[0117] In addition, the pose sensor system 94 is configured to determine the poses (e1 , e2) 97 of the exit points 58, 59 expressed in the boom reference frame {CB}, which may be measured using the trolley displacement sensors 77 and kinematic calculations involving survey data. Alternatively, or in addition, the exit point poses (e1 , e2) 97 may be measured by the image sensor 38 configured to detect the two marker patterns 70, 71 on each of the trolleys 56, 57 and subsequent transformation of those poses in a boom reference frame {CB}.

[0118] The tension and exit point calculator 86 is configured to derive desired tagline tension magnitudes T1 , T2 which are required for ensuring that the measured load pose 95 matches with the desired load pose 83. The tagline tension magnitudes T1 , T2 either serve to counteract undesired translations and rotations of the suspended load assembly 40, or may cause a motion, depending on the output of the load trajectory calculator 82.

[0119] The tension and exit point calculator 86 receives, from the pose sensor system 94, the momentary poses (e1 , e2) 97 of the tagline exit points 58, 59 measured relative to the boom reference frame {CB}. From the pose sensor system 94, the tension and exit point calculator 86 also receives the momentary poses (a1 , a2) 96 of the tagline coupling points 54, 55 measured relative to the boom reference frame {CB}.

[0120] Based in part on the calculated desired wrench 85, the tension and exit-point calculator 86 uses a tension distribution algorithm to derive how the desired wrench 85 is to be effectuated, by controlling the winches 62, 63 to dynamically adjust the individual tagline lengths L1 , L2 until desired tension values 88 in the two taglines 44, 45 are realized. A further function inside the tension and exit-point calculator 86 is the determination of the required exit point poses (e1 , e2) 97 as required for controlling the desired positions 87 of the trolleys 56, 57 in order to ensure that the taglines 44, 45 remain substantially within the selected reference plane (here, a horizontal plane Ph) even when the boom luffing angle y and / or the hoisting height H changes. For this purpose, the tension and exit-point calculator 86 is supplied with the crane’s luffing angle y, the hoist height H and potentially also a crane’s or vessel’s IMU information (for additional out of axis roll and pitch compensation to be done by the exit points).

[0121] The separation of the desired tension values 88 for each winch 62, 63 and desired exit point poses 87 for each trolley 56, 57 may be determined using analytic matrix equations that take into account the measured momentary positions (a1 , a2) 96 of tagline coupling points 54, 55 relative to the boom reference frame {CB}, the measured momentary pose 95 of the load assembly 40 relative to the boom reference frame {CB}, and the measured momentary positions (e1 , e2) 97 of the tagline exit points 58, 59 relative to the boom reference frame {CB}. The desired tension values 88 may then be applied preferably in an external reference frame {CE} or in a target reference frame {CT} by selecting one of the three desired references (crane, external, or target) to be also the reference in which the desired load pose 83 is expressed by the load trajectory calculator 82.

[0122] The tension and exit-point calculator 86 is configured to determine the tagline directions and their norms, and to use this information to construct a coupling matrix, based on the selected degrees of freedom, that maps the tagline tension magnitudes into forces and torques exerted on the load assembly 40 in the boom reference frame {CB} via derivation of the tagline lengths and directional information.

[0123] The tension and exit-point calculator 86 is further configured to multiply the coupling matrix with a desired motion input wrench. This coupling matrix includes information about the relative pose of the load assembly 40 to the boom reference frame {CB} and information about the measured exit point poses 97 relative to the boom reference frame {CB}.

[0124] In the examples shown in Figures 1-5, the tagline guide members 56, 57 and corresponding tagline exit points 58, 58 were configured to be dynamically repositioned up- or down- along the crane boom 34.

[0125] Figure 6 illustrates that the exemplary control arrangement 80 further includes means for monitoring and controlling the momentary poses 97 of the cable exit points 58, 59 on the crane boom 34. Current positions 99 for the trolley poses 99 may be measured by positional encoders 77 in the motor units of the trolleys 56, 57 (Figure 4) and / or by image data from the imaging sensor 38 based on trolley markers 69.

[0126] The exemplary arrangement 80 includes a trolley controller 98, configured to receive desired exit point poses 87 from the tension and exit-point calculator 86 as well as the momentary positions 101 of each trolley, based on which the trolley controller 98 generates trolley error signals, and generates based on those command signals that correspond to new desired positions 99 for the trolleys and their tagline exit points along the boom 34 that ensure that the taglines 44, 45 remain spanned substantially along the reference (e.g. horizontal)plane Ph, also when the momentary luffing angle y or slewing angle (p of the boom 34, and / or the momentary hoist distance H of the hoist assembly 40 changes. The trolley controller 98 transmits the desired trolley pose commands 99 in real time to the trolley actuators 75 (Figure 4), which upon receipt cause the actuators 75 to move the trolleys 56, 57 to the desired positions 99.

[0127] Figure 6 illustrates that - in addition to the trolley control and feedback loop 98, 77 / 38 - the exemplary control arrangement 80 further includes a tagline control and feedback loop 102, 64, 65.

[0128] The tension and exit-point calculator 86 issues instructions to the winch controller 102, to command the individual winches 62, 63 to actuate their drives to achieve the newly set desired tension 88 for the respective winch. Meanwhile, each tension sensor 64, 65 continuously or intermittently measures the momentary tension 105 in the corresponding tagline 44, 45 at successive times. Each respective winch 62, 63 then compares its currently measured tension 105 and determines a momentary error between the desired tension 103and actual tension 105, to determine whether the winch drive needs to continue changing the tagline length L1 , L2 or whether the setpoint has been reached.

[0129] Figure 6 thus illustrates that the proposed arrangement and method may involve a hierarchy of active feedback control loops, with the tension feedback control loop 102 for the individual tagline sensors and the positional feedback control loop 98 for the individual trolleys are being nested inside the pose feedback control loop for the load motion controller 84.

[0130] The currently set tension vectors F1 , F2, for which the magnitudes T1 , T2 have been established by the winches 62, 63 and for which the vector directions have been established by the currently set trolley positions 100, finally act on the suspended load assembly 40, via the two taglines 44, 45 and at the positions of the tagline coupling points 54, 55 on the load carrier 47. These tensions F1 , F2 exert a linear force on the load assembly 40 in the selected translational DOF Tx and / or angular torque on the load assembly 40 in the selected rotational DOF Rz, in a way that the excitation of these two DOF proceed in a mutually decoupled manner. The linear force and / or angular torque cause the load assembly 40 (and ultimately the load 46) to change (or maintain) its pose towards the desired pose 83.

[0131] The above elements in the control arrangement described with reference to Figure 6 have been described in terms of system components, interactions and dependencies.However, it will be understood that according to the second aspect, any selected combination of the components, interactions and dependencies also can be described as method steps, by using the appropriate gerund form.

[0132] Apart from this, depending on the preferred calculation algorithms, desired numerical stability of the various matrix calculations, and / or a desire to show on-screen results to an operator expressed in a particular reference frame (e.g. {CE} or {Cv} or {Cc} or {CT} etc), any of the calculations and poses for the various objects may also be expressed in this particular reference frame through suitable coordinate transforms and / or matrix inversions.

[0133] Those skilled in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques, and would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

[0134] The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein, for instance with reference to figure 5, may be implemented or performed with a general-purpose processor (e.g. a PC or IPC), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device (e.g. a PLC), discrete gate or transistor logic, discrete hardware components, graphical processor unit (GPU) or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, digital signal processor or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor or a combination of DSP and FPGA, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0135] The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, solid state disk, removable disk, CD / DVD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

[0136] In the non-limiting examples discussed with reference to Figures 1-5, the hoisting arrangement was formed as a jib crane. In alternative embodiments, however, the proposed system may be installed in / on or otherwise be used to augment any type of crane that includes one or several booms, jibs, or arms (either solid or lattice structure, fixed or telescoping) which is / are configured to exhibit a luffing motion and / or a hoisting of a suspended load.

[0137] In other method embodiments, the tagline system may be used to install a nacelle suspended from the hoisting arrangement on a pre-installed tower, transition piece and monopile of a wind turbine. The ability to perform precise rotational adjustments ±Rz of the suspended nacelle independently from horizontal translations ±Tx reduces installation complexity by obviating the need to power the horizontal slewing actuator in the nacelle in order to align the nacelle base with the monopile.

[0138] In yet alternative method and / or system embodiments, the vehicle may be a floating vessel, platform, or pontoon. The proposed systems may also be used in a land-based crane (e.g. a wheeled, railroad-based, or caterpillar tracked crane, or a fixed tower crane), for instance during hoisting and mounting of a prefab element (such as a concrete floor slab) on a pre-assembled house or civil structure. In such settings, detection of the pose of the suspended load might only be needed in a horizontal plane, such as determining the ±Tx and ±TY translational positions and the ±Rz rotational position of the prefab element which may be done by direct image processing techniques known in the art.

[0139] In yet an alternative method and / or system embodiments, the vehicle may be a jackup or a floating vessel. The proposed systems may also be used to install any secondary steel components onto a bottom-fixed or a floating structure of e.g. a partially assembled wind turbine generator. In such settings, the proposed system may make use of its decoupled motion compensation to install ladders or concrete platforms onto monopiles or transition pieces or any other construction element intended to conclude a construction of an offshore asset.

[0140] In the examples shown in Figures 1-5, the displaceable tagline guide members were implemented as trolley carts that were linearly repositionable with drives and lockable with brakes along guiding tracks implemented as rigid rails provided along the boom. However, in alternative embodiments, actuation of the trolley positions along the boom may be implemented using winches and tug lines attached to the trolleys (e.g. via pad-eyes). In yet alternative embodiments, the trolleys may be implemented by pulleys that are slidable along guidewires that are spanned along the longitudinal direction of the boom, between a proximal end near the base of the boom and a remote part towards a distal end of the boom.

[0141] In the example shown in Figures 2a-b and 5, the taglines extended in a non-parallel non-crossing arrangement between the respective exit points on the boom and the coupling points on the load carrier. In alternative embodiments, however, the taglines may be arranged to cross each other at a position between the exit points and the coupling points, so that both taglines depart from their respective exit point, then intersect the sagittal plane Ps at a location in front of the boom, before the taglines proceed to their coupling points located on laterally opposite sides of the sagittal plane. In such embodiment, the positions of the tagline guide members may additionally be controlled to maintain a small vertical offset between the taglines, which is sufficient to prevent the taglines from mutually colliding but remains minimal to ensure that both taglines remain close to the nominal horizontal plane Pt vertically sandwiched between the two crossing taglines. A crossed tagline arrangement may confer an improved rotational control force around a substantially vertical axis Az extending through the hoisting point but at the expense of a reduced level of decoupling between the selected two DOFs.

[0142] In the example shown in Figures 2a-b and 5, the two taglines extended in a nonparallel arrangement between the respective exit points on the boom and the coupling points on the load carrier substantially in a horizontal plane. Alternatively, the nominal plane spanned by the two taglines may also be non-horizontal, as long as the angle that this plane spans is maintained during a substantial part of the lifting operation, by appropriate dynamic readjustment of hoist lengths and the tagline guiding members (and exit points).

[0143] In the exemplary tagline systems shown in Figures 1-5, two taglines were present. In alternative embodiments, additional taglines may be connected to the load assembly and to the boom, which extend in slanted directions upwards from the boom towards the loadassembly. Such secondary taglines may be held at substantially constant tensions during motion control operation, to ensure that the suspended load assembly remains stabilized against upwards or downwards perturbing forces caused by sudden wind jerks acting on the suspended load assembly.

[0144] In the examples of Figures 1-5, the locations of the tagline coupling points relative to the load reference frame {CL} were static. This is not required, though. In alternative embodiments, the tagline coupling points may be implemented in a moveable manner on the load or the load carrier, for instance by pulleys or arms that may change shape and / or orientation. In such embodiments, similar advance surveying techniques and online position measurement (e.g. with position encoders) as were described for the tagline exit points, may be employed to establish momentary positions of the tagline coupling points relative to the load reference frame {CL}.

[0145] In the examples shown in Figures 1-3b, the imaging sensor was implemented using only a single camera 38. In alternative embodiments, the imaging sensor may be implemented by an assembly of cameras that are mutually and algorithmically coupled, each camera including an optical system (e.g. lens) with either the same or a different field of view to allow the various objects to be imaged and their momentary poses to be determined across a wide range of distances between these objects and the imaging sensor. Using such a composite image sensor allows the method to be used for a wide range of hoisting configurations at small and large hoisting distances, without needing to adjust the imaging sensor during the operation.

[0146] In yet alternative embodiments, the imaging sensor may be implemented using one or multiple laser sensors (for instance a LIDAR sensors), configured to dynamically acquire sparse point cloud image data of objects within their field of view. The acquired point cloud data may then be compared with available geometric data of known objects (for instance 3D CAD models of the load carrier and / or the load) by known computer vision techniques involving optimizing a similarity metric while iterating through pose transformation parameters between the model and the current point-cloud data to find the best matching poses for the objects (e.g. load carrier and / or load) relative to the (common) sensor reference frame {CS}.

[0147] In the exemplary arrangement shown in Figure 6, the feedback loops for the trolley positions and tagline tensions were nested inside the pose feedback control loop. In alternative embodiments, the control arrangement for the feedback loops may be integrated by means of a single multiple-input multiple-output (MIMO) controller.

[0148] It will be understood that the term “matrix equation”, which in the present disclosure is used during calculating the tensile force magnitudes, should not be construed in a limited way as covering only the specific compact notation that involves a matrix. Instead, the skilled person will understand that the term pertains generally to a system of linear equations that describe (possibly approximated) linear relations between a known input vector (such as avector of desired wrench components to be exerted on the load) and an unknown output vector (such as the vector of tensile force magnitudes).

[0149] The present invention may be embodied in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. It will be apparent to the person skilled in the art that alternative embodiments of the invention can be conceived and reduced to practice. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope, to the extent permitted by relevant national laws or intergovernmental agreements.List of Reference SymbolsSimilar reference numbers that have been used in the description to indicate similar elements (but differing only in the hundreds) have been omitted from the list below, but should be considered implicitly included.10 body of water (e.g. sea)12 target (e.g. wind turbine)14 pile16 nacelle17 rotor hub18 blade19 connection member (e.g. bolt)20 tagline system21 control device (e.g. crane or vessel computer)22 vehicle (e.g. offshore vessel)24 leg26 deck28 crane30 pedestal32 turret34 boom35 base36 jib37 tip38 imaging sensor (e.g. camera)40 load assembly40o offset pose40R rest pose42 hoist line44 1sttagline45 2ndtagline46 load (e.g. blade)47 load carrier (e.g. blade cradle)48 hoist suspension point49 hoist coupling point50 1sttagline section51 2ndtagline section52 1stfurther tagline section53 2ndfurther tagline section54 1stcoupling point55 2ndcoupling point56 1stguide member (e.g. trolley)57 2ndguide member (e.g. trolley)58 1stexit point59 2ndexit point60 1stguiding track (e.g. rail)61 2ndguiding track (e.g. rail)62 1stwinch63 2ndwinch64 1sttension sensor65 2ndtension sensor66 inertial measurement unit (IMU)67 sensor FOV68 load marker (fiducial)69 target marker70 1sttrolley marker71 2ndtrolley marker72 trolley bracket73 trolley wheel74 trolley swivel75 trolley drive76 trolley brake77 position encoder78 trolley sheave80 control arrangement81 measured crane pose82 load trajectory calculator83 desired load pose84 load motion controller85 desired 2DOF wrench86 tension and exit point calculator87 desired exit point poses88 desired tagline tensions90 boom sensor92 hoist line sensor93 measured load height94 pose sensor system95 measured load pose96 measured coupling point poses (a1 , a2)97 measured exit point poses (e1 , e2)98 trolley controller99 desired trolley positions100 current trolley positions101 measured trolley positions102 winch controller103 desired winch tensions104 current winch tensions105 measured winch tensionsAB boom body axisAj jib body axisAT target body axisAL load body axisAz load vertical axisAy luff axisArp slew axisFg gravity forceFh hoisting forceF1 1sttagline tension vectorF2 2ndtagline tension vectorT1 1sttension magnitudeT2 2ndtension magnitudeH hoisting distancePs sagittal planePc coronal planePt tagline planePv vehicle planePh horizontal planeX first linear directionY second linear directionZ third linear directionRx first rotational directionRy second rotational directionRz third rotational direction y luff angle qj sheave rotation anglep1 1stslant angle p2 2ndslant angle{CL} load reference frame{Cv} vessel reference frame {CB} boom reference frame{Cs} sensor reference frame{CT} target reference frame{CE} external reference frame (e.g. ECEF)

Claims

1. 33Claims1. A system (20) for compensating motion of a load (40, 46, 47) suspended from a suspension point (48) on a boom (34) of a hoisting arrangement (28), wherein the boom (34) is rotatable over a boom luffing angle (y) and / or wherein a hoisting distance (H) between the load (40, 46, 47) and the suspension point (48) is adjustable, the system comprising: two taglines (44, 45) configured to extend from the boom to the load and to exert tensile forces (F1 , F2) on the load in directions towards the boom; two guiding members (56, 57) defining respective exit points (58, 59) at or near the boom (34) where the taglines (44, 45) are allowed to extend from the boom in transverse directions towards corresponding coupling points (54, 55) on the load (40, 46, 47); a pose sensor (38, 94) configured to dynamically determine a momentary pose (95) of the load; a controller (21 , 80) configured to control motions of the load in at least two selected degrees of freedom, DOF, by: dynamically and individually adjusting (102-105) tensions in the taglines based on the momentary pose (95) of the load, and by dynamically adjusting (98-101) respective positions of the guiding members (56, 57) along the boom (34) in response to a change in the boom luffing angle (y) and / or in the hoisting distance (H), to maintain each of the taglines (44, 45) substantially parallel with a reference plane (Ph), for instance a horizontal plane, during operation.

2. The system (20) according to claim 1 , wherein the controller (21 , 80) is configured to coordinate dynamic adjustment of tensile force magnitudes (T1 , T2) in the taglines and the positions of the guiding members (56, 57), to dynamically control motion of the load (40, 46, 47) in two spatial DOF, including a translational DOF (±Tx) in a transverse direction (XB, XE) and a rotational DOF (±Rz) about a nominal hoisting axis (Az) in a vertical direction (ZB, ZE).

3. The system (20) according to claim 2, wherein the controller (21 , 80) is further configured to calculate the tensile force magnitudes (T1 , T2) using a matrix equation constructed based on the momentary pose (95) of the load and the momentary poses (96, 97) of the coupling points (54, 55) and the exit points (58, 59) relative to a reference frame ({CB}) of the hoisting arrangement, to yield a decoupled motion control between the translational DOF and the rotational DOF.

344. The system (20) according to any one of claims 1-3, wherein the hoisting arrangement (28) includes an inertial measurement unit, IMU, (66) configured to measure a pose of the boom (34) relative to an external reference frame ({CE}, {CV}); and wherein the controller (21 , 80) is configured to dynamically determine, from the measured pose of the boom, the momentary positions of the hoisting arrangement (28), the load (40, 46, 47) and the exit points (58, 59) with respect to the external reference frame.

5. The system (20) according to any one of claims 1-4, wherein the pose sensor (38, 94) includes an imaging sensor (38) configured to acquire spatiotemporal image data of the load (40, 46, 47), and a processor (94) configured to dynamically determine from the image data a momentary pose (95) of the load with respect to a reference frame ({CB}) of the hoisting arrangement or to an external reference frame ({CE}, {CT}).

6. The system (20) according to claim 5, wherein the guiding members (56, 57) are provided with markers (70, 71) directed towards and located within a field of view (67) of the imaging sensor (38); wherein the imaging sensor (38) is configured to acquire the spatiotemporal image data containing both the markers (70, 71) and the load (40, 46, 47); and wherein the processor (94) is configured to dynamically determine, from the image data, momentary poses of the markers (70, 71), and to derive therefrom the momentary poses (97) of the exit points (58, 59).

7. The system (20) according to claim 5 or 6, wherein the imaging sensor (38) has a field of view (67) that is sufficiently wide to allow concurrently capturing the load (40, 46, 47), the guide members (56, 57), and possibly also part of a target (12), to be within the same image data.

8. The system (20) according to any one of claims 5-7, wherein the imaging sensor (38) has an adjustable field of view (67), by rotating the field of view and / or by translating the imaging sensor relative to the boom (34) in response to the change in the boom luffing angle (y) and / or in the hoisting distance (H), so as to dynamically maintain both the load (40, 46, 47) and the exit points (58, 59) within view during operation.

9. The system (20) according to any one of claims 1-8, wherein the controller (21 , 80) is configured to calculate (86) a desired distribution of momentary tensile force magnitudes (T1 , T2) for moving the load (40, 46, 47) from a current load pose (95) to a desired load pose (83).

10. The system (20) according to any one of claims 1-9, wherein the pose sensor (38, 94)is configured to determine the momentary pose of the load (40, 46, 47), the momentary poses (97) of the exit points (58, 59), and the momentary poses (96) of the coupling points (54, 55) relative to a reference frame ({CB}) of the hoisting arrangement (28), and wherein the controller (21 , 80) is configured to calculate desired poses (87) for the exit points for maintaining the taglines (44, 45) substantially parallel with the reference plane (Ph), and to dynamically issue control signals to the guiding members (56, 57) to reposition into the desired poses (99).

11. The system (20) according to any one of claims 1-10, wherein the suspension point (48) is located at a jib portion (36) of the boom that protrudes forward relative to a main portion (34) of the boom, and the load (40, 46, 47) is suspended below the jib portion (36) and in front of the main portion (34); wherein the taglines (44, 45) extend from the respective exit points (58, 59) on two lateral sides of a sagittal plane (Ps) of the boom (34), and in transverse forward direction (+XB) towards the load; wherein the controller (21) is configured to dynamically adjust the tensile force magnitudes (T 1 , T2) maintained in the taglines (44, 45) to keep the load deflected in transverse rearward direction (-XB) towards the boom.

12. The system (20) according to any one of claims 1-11 , wherein both the taglines (44, 45) are configured to extend substantially along a same tagline plane (Pt), and wherein the controller (21 , 80) is further configured to dynamically adjust (98-101) the positions of the guiding members (56, 57) in response to the change in the boom luffing angle (y) and / or in the hoisting distance (H), to maintain the tagline plane (Pt) substantially parallel with the reference plane (Ph) during operation.

13. The system (20) according to any one of claims 1-12, wherein the guiding members (56, 57) include trolleys (72, 73), and wherein the boom (34) comprises tracks (60, 61) extending substantially along a length direction (AB) of the boom, each track being configured to couple to a respective trolley and allow the trolley to be moved along the track while restricting trolley motion in directions transverse to the track.

14. The system (20) according to claim 13, wherein the trolleys (56, 57) are provided with positional encoders (77) configured to dynamically provide indications of momentary positions (101) of the trolleys (72, 73) relative to the corresponding tracks (60, 61); wherein the processor (94) is configured to dynamically determine, from the indications of momentary positions (101), the momentary poses (97) of the exit points (58, 59).

15. The system (20) according to any one of claims 1-14, wherein the hoisting arrangement (28) includes a crane (28) that is mounted on an offshore vessel (22), and wherein the load (40, 46, 47) includes one or more components (16, 17, 18) of an offshore wind turbine (12).

16. The system according to any one of claims 1-14, wherein the hoisting arrangement includes a crane that is fixed to the earth, to a building, or to a wheeled or tracked vehicle, and wherein the load includes a prefab structural element of a land-based building or infrastructure.

17. A method for compensating motion of a load (40, 46, 47) suspended from a hoisting arrangement (28), using a tagline system (20) according to any one of the preceding claims.

18. A computer program product configured to provide instructions to carry out a method according to claim 17 when loaded on a computer arrangement.

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