Load alignment control system and method for a load alignment control system

Abstract

The invention relates to a control system and method for controlling alignment of a load suspended on a crane with a target. The method includes determining a motion of the load in at least one degree of freedom, generating a compensation signal indicative of the motion of the load, and generating a control signal for the crane and / or a load motion compensation system LMCS in response to the at least one compensation signal, the first reference sensor is configured to control a reference attitude of the load within a reference coordinate system provided by the first reference sensor. The method further includes receiving, from the feature detection system, a relative motion signal indicative of relative motion between the target and the load; an alignment signal is generated in response to the relative motion signal, and a control signal for controlling the crane and / or the LMCS is generated in response to the alignment signal for moving the load in alignment with the target.

Description

Technical Field

[0001] The present invention relates to a control system for controlling the alignment of a load suspended from a crane with a target. In particular, the present invention relates to a load motion compensation system extended with a load alignment system. The present invention also relates to a method for controlling the alignment of a load suspended from a crane with a target. Background Art

[0002] The installation of offshore wind turbines is a complex matter. First, components such as nacelles and turbine blades must be lifted from the deck of the installation vessel by cranes or other lifting devices to a high altitude, for example up to 150 meters or more. Furthermore, these components must be assembled at this altitude with high precision while suspended from the crane. Installation may be even more difficult due to offshore conditions, such as wind and waves, which may impose disturbing motions on the installation vessel, on the components suspended in the air and lifted by the crane, and / or on the target structure on which the installation is to be performed.

[0003] In order to remove the installation vessel from the influence of water currents and waves, a jack-up vessel can be used. However, a jack-up vessel has a limited working area and limited availability in different waters due to the limitation of the height of the jack-up legs that can lift the vessel. Although the influence of waves and wind on the installation vessel can be reduced by jacking up the vessel, the wind and / or wave forces on all elements can still move the components suspended from the crane.

[0004] As an alternative to jack-up vessels and conventional cranes, motion-compensated cranes or stabilizing platforms may be used on floating vessels. Such cranes are arranged to keep a load suspended therefrom in substantially the same position and orientation, while the base of the crane moves with the vessel motion caused by wind and waves, since the base of the crane is rigidly attached to the vessel in at least some degrees of freedom. However, such motion-compensated cranes may be heavy, require a large amount of energy to operate, and / or have a limited working range or load capacity, particularly in terms of vertical reach.

[0005] An alternative motion compensation system is known from WO2021 / 002749A1, which discloses a load motion compensation system (LMCS), which consists of a crane with a hoist, such as a cable hoist or a hydraulic clamp, and a plurality of actuators, the actuator being a combination of a cable and a winch, which is controlled to compensate for movement caused by wind and water. The position of the hoist and the suspended load can be expressed as a three-dimensional coordinate in a Cartesian coordinate system including three orthogonal translation axes. The orientation of the hoist can be expressed as a set of three angles, which refer to the amount of rotation degrees around the translation axis. Any other symbols such as angular axis coordinates, homogeneous coordinates, etc. can be used for position, orientation, or a combination thereof. In combination, position and orientation are referred to as the attitude of an object. Multiple force sensors are arranged to provide sensor signals indicating the tension on one or more cables in the cable. The sensor tension signal is received by a control system arranged to control the winch based on the received signal. Therefore, the system disclosed in WO2021 / 002749A1 is able to compensate the load for movement due to wind and water or caused by any other factor, and maintain the attitude of the load within a (geographic) reference coordinate system, which is preferably based on a Global Positioning System (GPS) or any other geolocation information.

[0006] When mounted on a vessel and independent of whether the vessel is floating or jack-up, a load motion compensation system eases the task of mounting a load, such as a wind turbine blade, to an object, such as a nacelle or rotor of a wind turbine. In the case of using such a motion compensation system on a jack-up platform, such a motion compensation system allows mounting at higher wind speeds than would be possible without such a compensation system, and also allows the load to be mounted when the object (e.g., nacelle) is in motion. Summary of the invention

[0007] An object of the present invention is to facilitate alignment of a load with a target. In a first aspect, the present disclosure relates to a computer-implemented method for controlling alignment of a load suspended from a crane with a target. The method includes determining motion of the load in at least one degree of freedom, generating at least one compensation signal indicative of the motion of the load; and generating a control signal for the crane and / or a load motion compensation system (LMCS) in response to the at least one compensation signal for controlling a reference pose of the load within a reference coordinate system provided by a first reference sensor. The method also includes receiving a relative motion signal indicative of relative motion between the target and the load from a feature detection system; and generating a control signal for controlling the crane and / or the LMCS in response to the relative motion signal for displacement of the load toward the target.

[0008] According to another aspect, a control box is provided for controlling the alignment of a load suspended from a crane with a target.

[0009] According to another aspect, a control system for controlling alignment of a load suspended from a crane with a target is provided.

[0010] According to another aspect, a method for controlling alignment of a load suspended from a crane with a target is provided.

[0011] According to another aspect, there is provided a crane comprising a control system as disclosed.

[0012] According to another aspect, a vessel is provided comprising a crane and a control system as disclosed.

[0013] Particular embodiments of the invention are set forth in the dependent claims.

[0014] Other objects, aspects, effects and details of specific embodiments of the present invention are described in the following detailed description of a number of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] By way of example only, embodiments of the present disclosure will be described with reference to the accompanying drawings, in which:

[0016] Figure 1 schematically illustrates an example of a load suspended by a crane mounted on a vessel;

[0017] Figure 2 schematically illustrates examples of various mounting arrangements for a target;

[0018] Figure 3 schematically illustrates an example of a control system for controlling alignment of a load with a target according to the present invention;

[0019] Figure 4 An example of a sensor arrangement for a ship-borne crane according to the present invention is schematically illustrated;

[0020] Figure 5 schematically illustrates examples of features and feature detection systems according to the present invention;

[0021] Figure 6 Schematically illustrates Figure 5 The perspective of the feature detection system;

[0022] Figure 7 An example of a method for controlling alignment of a load with a target according to the present invention is schematically illustrated;

[0023] Figure 8schematically illustrates an example of a control scheme of a control system according to the present invention;

[0024] Fig. 9 Another example of a feature, a feature detection system and a feature plate according to the present invention is schematically illustrated;

[0025] Fig.10 Schematically illustrates an example of a feature plate installed on a loaded bolt according to the present invention;

[0026] Fig.11 Another example of a method for controlling alignment of a load with a target according to the present invention is schematically illustrated. DETAILED DESCRIPTION

[0027] Reference Figure 1 , shows a wind turbine generator 1 during installation. A nacelle 2 with a rotor 3 is mounted on top of a tower 4. The tower 4 is mounted on a foundation 5 which can be provided in various ways. For example, Figure 2 As shown, the foundation 5 can be provided through the seabed 6 via a so-called monopile, the foundation 5 can be a floating foundation 7, or can be a fixed jacket 8, or any other suitable foundation type. The floating foundation 7 can be anchored to the seabed by cables or chains. The fixed jacket 8 can rest on the seabed or be installed on the seabed together with piles.

[0028] exist Figure 1 Also shown in the figure is a vessel 9 on the sea 10 carrying a crane 11, from which a load 12, such as a wind turbine blade, is suspended. The crane 11 is arranged to provide various degrees of freedom and can be moved and articulated in various ways. The crane 11 is also equipped with a hoist system 13, which has a tool 14 carrying the load 12, such as a cable hoist, a winch hook, a hydraulic clamp or other types of devices for holding the load. The actuator 15 of the hoist system 13 controls the attitude, i.e., the position and orientation of the tool 14 and thus also controls the attitude of the load 12. The load 12 is preferably rigidly connected to the tool 14 to ensure that the attitude of manipulating the tool 14 directly affects the attitude of the load 12. In some embodiments, there may be some form of mechanical compliance or controlled compliance between the tool 14 and the load 12. In some embodiments, the tool may be suitable for directly grasping and carrying the load 12 while holding the load 12 in a rigid grasping manner. In some examples, the load may include a dedicated structure to enclose the element to be lifted and displaced. In this example, with respect to the installation of a wind turbine, the loads relate to the wind turbine blades which are to be aligned with a target, in this example the nacelle 2, for installation on the target. Alternatively, any other component may be considered as a load, such as a monopile, a transition piece, a tower or tower section, a nacelle, a rotor or any other part that needs to be assembled. Figure 1 Each of the components shown including the load, ie the blades 12 , the target, ie the nacelle 2 and the tower 4 may experience or be caused to move due to waves and wind.

[0029] Generally, in the present disclosure, a crane can be any device suitable for lifting and displacing a load. For example, a crane can include several articulated arms on a rotating platform. A crane can include some kind of articulated tower. Or a crane can include one or more towers with, for example, slides and / or main beams. In addition, a crane can include, for example, a plurality of winches and lifters in combination with an articulated tower. A crane can be combined with another serial or parallel structure to form a closed or open loop mechanism that can act on a load at one or more points. A crane can consist of a serial or parallel mechanism that directly holds a load.

[0030] Reference Figure 3 , a control system 30 for controlling the alignment of a load with a target is shown. The control system 30 includes a control box 38 having at least one controller, in this example a main controller 34 connected to various elements providing input signals, such as an operator or human machine interface (HMI) 31, a plurality of sensors 32, and manual controls 33. The main controller 34 in turn provides output signals to various elements, such as a load motion compensation system (LMCS) 35 and / or the crane 11. And the control system 30 may include a load alignment system, which is shown here as part of the various sensors 32.

[0031] At least one controller 34 of the control box 38 may be configured to generate an alignment signal in response to the relative motion signal. And a control signal is generated in response to the alignment signal for controlling the displacement of the load toward the target by controlling the LCMS 35 and / or the crane. The relative motion signal indicates the relative motion between the target and the load. The relative motion signal may be received from a sensor or a detection system including a plurality of sensors, as further described below. The alignment signal is generated to provide, for example, one or more target set points for the control system to control various actuators. In a simpler case, the alignment signal may be the same as the relative motion signal. Depending on the setting or configuration of the control system, the alignment signal may be represented in various other forms or formats. In a first aspect, the alignment signal is intended to enable the load to move simultaneously with the target, such as moving simultaneously in a synchronized manner, even if there may still be an offset. In a second aspect, the alignment signal may be intended to reduce the offset. And more preferably, it may be intended to cause corresponding structural features of the load and the target to face and / or engage with each other. The alignment signal may be derived by feedback control, such as feedback control applicable during visual servoing, and may directly drive the LCMS.

[0032] As will be appreciated, the main controller may perform all of these functions, or it may include additional dedicated controllers. For example, the control box 38 may include a load motion compensation system LMCS controller 39 for generating LCMS control signals. The control box 38 may include an offset calculator 37 for generating alignment signals. And the control box 38 may include a crane controller 36 for generating crane control signals. In alternative embodiments, each of the components of the control box may be arranged in a distributed arrangement, meaning that at least one or more of the controllers and / or computers may be remotely located and connected to the main controller via a cable or wirelessly connected to the main controller.

[0033] Typically, the generation of signals can be performed sequentially or in parallel, or the signals can be combined. This can depend on the type of computing resources and algorithms applied. In addition, the generation of signals can be continuous and thus result in time-varying signals. Therefore, the generation of a signal can trigger the generation of an additional signal in response thereto while still continuously generating the one signal. For example, in the case where a control signal is generated in response to an alignment signal, this can be interpreted as generating a control signal according to the alignment signal being generated, or in other words, the control signal is generated relative to the alignment signal being generated. For example, a control signal can be generated directly based on a relative motion signal by applying a feedback control law, such as a feedback control law used during visual servoing, which will be familiar to those skilled in the art. In this case, the relative motion signal and the alignment signal can be combined, and the control signal can also be combined. In this case, the compensation signal can also be combined with the control signal, and the processing can not involve representing the compensation signal with an absolute reference, but directly applying a relative reference in response to the relative motion signal.

[0034] The operator or human machine interface HMI 31 can take any form, such as a joystick, a touch screen, a display with a SCADA system, a button, a graphical user interface, or any other form that enables an operator to provide input to the main controller 34. Alternatively, the HMI 31 can also provide input directly to the LMCS controller 39 or the crane controller 36. In addition, the operator can manually provide input via the manual control 33. The manual control 33 can include one or more joysticks, control levers, buttons, knobs, space mice, mice, micromanipulators, or any other human manual input device. The input of each of the HMI 31 and the manual control 33 can be used by the main controller 34 to generate a set point. The set point can be output to the crane controller 36 for moving the load suspended on the crane. And / or the set point can be output to the LMCS 35 to control the attitude of the load 12. The crane controller 36 is configured to control the crane 11 to move and articulate according to the set point if provided, depending on the type of crane.

[0035] The LMCS 35 is configured to control a reference attitude, preferably an absolute reference attitude, of the load. The reference attitude, including position and orientation, may be a set point received from the master controller 34. The set point may also be configured to be interpreted as a relative attitude or an absolute attitude relative to a target, which may be expressed with respect to a terrestrial coordinate reference system or with respect to a reference coordinate reference system. Such a terrestrial coordinate reference system may be derived via a global positioning system GPS, Beidou, Glonass, Galileo, or any other currently known global positioning system (GNSS). The LMCS 35 may include at least one motion sensor arranged to determine the motion of the load in at least one, preferably two, degrees of freedom. The at least one motion sensor is also arranged to generate at least one compensation signal indicating the motion of the load. The LMCS 35 also includes at least one motion compensating actuator arranged to control the attitude of the load in response to at least one compensation signal. The load motion compensation system may also be configured to process the compensation signal and enable the motion compensating actuator for controlling the attitude of the load in a reference attitude, preferably an absolute attitude. Or alternatively directly relative to the target.

[0036] Reference Figure 5The load alignment system includes: a feature 51, which can be arranged on the load 12 or on the target 2; and a feature detection system 50, which is arranged on the target 2 or on the load 12 accordingly. Therefore, depending on which component, load or target the feature 51 is arranged on, the feature detection system 50 will be arranged on another component, target or load. The feature detection system 50 is configured to detect the feature 51, track the movement of the feature 51, and generate a relative motion signal indicating the relative motion between the target and the load.

[0037] The load alignment system may further include an offset calculator 37 for generating an alignment signal in response to the relative motion signal. The offset calculator may be, for example, Figure 3 The dedicated computing resources shown in the embodiment of the present invention, or the offset calculator can be provided as part of the main controller 34. In either case, the function of the offset calculator to generate an alignment signal in response to the relative motion signal can be provided. The generated alignment signal can be transmitted by the main controller 34 to the crane controller 36. Or when generated by a dedicated offset calculator 37, it can be transmitted via the main controller 34. Alternatively, the alignment signal can be transmitted directly from the dedicated offset calculator 37 to the crane controller 36, such as Figure 3 . The crane controller 36 is configured to control the crane 11 in response to the alignment signal for displacement of the load towards the target. Alternatively or additionally, the generated alignment signal may be transmitted by the main controller 34 to the LMCS controller 39. Or transmitted via the main controller 34 when generated by the dedicated offset calculator 37. Or the alignment signal may be transmitted directly to the LMCS controller 39 by the dedicated offset calculator 37 (not shown). The LMCS controller 39 may be additionally or alternatively configured to control the LMCS 35 in response to the alignment signal for displacement of the load towards the target. The main controller 34, the LMCS controller 39, the crane controller 36 and / or the offset calculator 37 may all be combined and may include at least one or more feedback controllers based on inputs from the HMI 31, the sensors 32 and / or the manual controls 33.

[0038] A control box 38 having at least one controller 34 is configured to generate an alignment signal in response to the relative motion signal and to generate a control signal for controlling the displacement of the load towards a target in response to the alignment signal by controlling the load motion compensation system LCMS and / or the crane.

[0039] Reference Figure 1, the actuator 15 of the LMCS may include a set of control lines or tow lines mounted on a tool 14 holding a load 12. The control lines are arranged so that the tool and the load can move in at least one, preferably at least two, degrees of freedom, such as at least one of pitch, roll, yaw, heave, sway and / or surge as mentioned in the field of navigation. By applying different tensions on these control lines, the position and orientation of the tool 14 and the position and orientation of the load 12 can be controlled in the arranged degrees of freedom. The way of representing the degrees of freedom can take any form and is not limited to orthogonal systems, as the way of representing the degrees of freedom can include a right-handed coordinate system, a left-handed coordinate system, a quaternion or axis angle representation of position and orientation, or any other representation.

[0040] As an alternative to a cable-based system, the LMCS can be arranged in different ways, for example by arranging it as a mechanical device with one or more towers providing multiple degrees of freedom. For example, the LMCS can be arranged on a tower with a rotating base located on the deck of the ship, several linear actuators and / or additional rotary joints to move the load relative to the ship. In fact, any suitable kinematic chain that can be envisioned by a person skilled in the art can be used. As long as the LMCS is able to cause controlled movement of the load.

[0041] Reference Figure 4 and Figure 5 , will be described in more detail as Figure 3 A plurality of sensors 32 of a control system 30 are shown. In the following description, each sensor "nn" may define a local coordinate reference which will be denoted by {Snn}, where "Snn" is the name of the coordinate reference.

[0042] exist Figure 4In the embodiment of the present invention, a first reference sensor 41 is arranged on the tool 14 and provides a reference coordinate system {S41}. A second reference sensor 42 may be arranged on the crane 11 in addition or alternatively and provide a second reference coordinate system {S42}. When the reference sensor 42 is arranged as a substitute for the reference sensor 41, the sensor 42 may be regarded as a first reference sensor. The first reference sensor 41 is also capable of providing attitude measurements of the tool in absolute world coordinates or geographic location {W} by utilizing, for example, global navigation satellite sensor signals in combination with an inertial measurement device, commonly referred to as a GNSS / INS device. Additionally, correction services such as PPP or RTK or any other available correction may be used to improve the accuracy of the attitude measurements. The second reference sensor 42 may provide remote sensing measurements of the tool and / or the load and convert the attitude information of the tool and / or the load so that the attitude of the load 12 may be expressed in world coordinates {W}. In this case, the sensor 42 can remotely sense the tool or load via one or more cameras, lidar, or radar or can measure feedback from active or passive markers, reflectors, or any other active or passive system for determining the relative pose between the sensor 42 and the tool 14 and / or load 12.

[0043] Thus, when using a GNSS / INS arrangement, the first reference sensor 41 can measure the attitude of the tool 14 and / or payload 12 directly in world coordinates {W}. Or, alternatively, the attitude and posture of the tool 14 and / or payload 12 can be measured indirectly with the help of a second reference sensor 42 that utilizes telemetry measurements of any feature as described above, or telemetry measurements of the first reference sensor 41, for example, acting as an active or passive marker or radio beacon, and then converting these measurements to world coordinates. For example, telemetry measurements can be accomplished by utilizing a GNSS / INS combination in the second reference sensor 42, and using a camera, lidar, radar, or other telemetry technique to infer the relative position of the first reference sensor 41 or the relative position of any feature of the tool 14 and / or payload 12 and / or any marker arrangement relative to the second reference sensor 42.

[0044] Therefore, the attitude of {S41} can be measured in a relative manner in {S42}, and if {S42} utilizes a GNSS / INS system, the attitude of {S41} in the world coordinate {W} will be easily derived. It will be appreciated that the arrangement of the first reference sensor 41 and the second reference sensor 42 can be reversed while achieving the same result. In addition, the first reference sensor 41 and the second reference sensor 42 can be used alone or in combination. In addition, additional sensors can be provided, each of which defines another reference coordinate system {Snn}. When multiple reference sensors are used, these sensors are preferably arranged so that each sensor has a attitude that can be represented in the coordinate system of at least one other reference sensor. As long as at least one of the reference sensors is capable of providing world coordinates {W} and each sensor can be associated with its attitude to at least one other reference sensor by telemetry or by inference, then all sensor and load attitude measurements can be represented in world coordinates {W}. In addition, kinematic techniques can be used, such as, for example, using Denavit-Hartenberg parameters and homogeneous transformations combined with many rotational measurements that can be derived from encoders, such as, for example, in a serial robot arm. Since the attitude of each sensor can be inferred and expressed in the reference coordinate system of the other sensor, a kinematic chain can be defined. Similarly, attitude measurements, i.e. positions and orientations, of other elements such as the crane 11, the lift 13 and / or the vessel 9 can be performed by inference or directly expressed in world coordinates {W}.

[0045] For example, in Figure 4 In the embodiment, the third sensor 43 may be mounted on the vessel 9 and provide a third reference coordinate system {S43}, in which the attitude of the first reference sensor 41 and / or the second reference 42 may be represented. If the third reference sensor 43 is provided with a GNSS / INS device, the other reference sensors may not be provided with such a device and still obtain a position expressed in world coordinates {W} via kinematic propagation.

[0046] As another example of a suitable sensor device, still referring to Figure 4The fourth sensor 44 may comprise a set of rotary and linear encoders and / or position measuring devices which together with information on the crane's geometry and the crane's attitude relative to the vessel may be used to infer the position of the second reference sensor 42 in a third reference coordinate system {S43} or, alternatively, in a vessel reference coordinate system {V} provided by the vessel structure itself. Any further and / or other combinations of sensors suitable for measuring attitude may be envisaged which may also include parameters such as velocity, acceleration and / or load jerk. Although all attitudes are here expressed in an absolute world coordinate system {W}, the methods described herein are equally applicable to the case where no transformation to a world reference is performed but rather a direct relative transformation between the load and the target is measured and controlled by utilizing relative motion signals and / or alignment signals.

[0047] Depending on the type of load, for example in longitudinal extension, it is preferred to define one point of the load as the load center, such as the center of gravity, and one point as the load end. The load center can then be considered as a reference center and the position of the load end can be described with reference to the load center, which can help to describe the attitude of the load. Both the load center and the load end can be defined as origins and corresponding coordinate reference systems {LC} and / or {LE} provided. These points can be used interchangeably as origins. When the load is considered as a relatively rigid object, the load end will move according to the movement of the load center. In particular in the case of a wind turbine blade which is a rigid longitudinal object, the blade center 16 can be defined as the load center {LC} and the blade root 17 as the load end {LE}, as Figure 4As shown. Each of the blade center and the blade root again defines a coordinate reference system {BC} and {BR}, respectively. As will be appreciated, using various sensor reference coordinates, the position of the load end may be expressed in world coordinates {W} or relative to world coordinates {W}, or relative to any other arbitrarily selected position on the crane or vessel or load compensation system. Alternatively, the load end may also be measured directly from a sensor 45 attached to the tool or may be measured directly by a sensor 46 attached near the load end. Measuring from the tool 14 via the sensor 45 may be preferred for non-rigid objects, for which the motion of the load end may not be easily determined from the motion of the load center, or where the detailed geometry of the load is unknown. In this case, the sensor 45 may be arranged to measure the attitude of the load end relative to the sensor coordinate reference {45}, and the attitude may then be expressed in world coordinates via one of the methods described above, including conversion via a GNSS / INS device, or via inference or kinematic propagation through other sensors and coordinate references, equivalent to a sensor combined with a GNSS / INS device capable of expressing its own coordinates in a world reference. The sensor 45 may be arranged to remotely detect certain geometrical features of the load and determine their relative attitude with respect to {45}. This may be achieved by, for example, one or more cameras, lidar or radar or by any combination thereof or by any other known method of determining the attitude of a structure with respect to a reference. Alternatively, the load end attitude may be measured directly by the sensor 46 in a coordinate reference {46} which may then be directly converted again to a world reference by a dedicated GNSS / INS device as part of the sensor 46 or by inference and / or kinematic propagation to another sensor incorporating such means, as described above.

[0048] Reference Figure 5, shows an example of a feature detection system 50 and a feature 51 present on a load 12. The feature detection system 50 is configured to detect the feature 51, track the motion of the feature 51, and generate a relative motion signal indicating the relative motion between the target, in this example, the nacelle 2, and the load 12. The feature detection system 50 includes a visual detector 52, in this embodiment, a camera, and a processing device 53 such as a PC, a PLC or other general-purpose processor, an FPGA or a microprocessor. Instead of a camera such as a CCD or CMOS camera, the visual detection device can use one or more LIDAR sensors or one or more RADAR sensors or any combination thereof or any other type of analog or computer-supported visual device. The processing device 53 is configured to process the signal from the visual detector 52 and perform the required processing to track the feature 51 and generate a relative motion signal, which can also be directly used as an input to the compensation signal. The feature detection system 50 also includes a communication module 54, such as a WiFi device or a universal cable network interface (router, switch, etc.), which is used to transmit and / or exchange signals with at least one other component of the control system.

[0049] The feature detection system 50 is placed inside, above or near the target 2, which in this example is Figure 1 The camera 52 is mounted on a tripod 57 and placed in a stable position on the interior floor 58 or other structural element of the cabin 2 and oriented so that the camera has an outward view toward the load aligned with the target 2. The exact mounting and mounting means are not relevant and may be performed in different ways.

[0050] Reference Figure 6 , showing Figure 5 The perspective of the feature detection system 50, or more specifically the visual detector 52, is looking out of the opening 59 formed by the mounting ring 60 of the nacelle to which the blade will be aligned and mounted. During the lifting operation, as the load 12 is moved by the crane 11 or LMCS for alignment with the target nacelle 2, a feature 51 present on the load blade 12 will be detected by the camera 52 and the movement of the feature 51 will be tracked. During the lifting operation, the LMCS or crane will compensate for the movement of the load due to wind etc., as described above. In addition, the target, in this example the tower and / or nacelle, may still experience movement due to wind etc. Therefore, the feature 51 may appear to move in front of the visual detector 52, regardless of whether the source of the movement is the load or the target or both, and the visual detector will track the relative movement of the feature with respect to the target.

[0051] Therefore, the motion of the feature 51 tracked by the feature detection system 50 represents the relative motion between the load 12 and the target 2. This relative motion can then be directly applied as input to control the attitude of the load via the crane or LMCS, for example via feedback control (visual servoing). However, since the absolute reference point of the load can also be known from the reference sensor device 32, this relative motion can be expressed in world coordinates {W}. And therefore, it can be used as a target set point for the control system 30. This allows the control system 30 to move the load 12 synchronously with the target 2.

[0052] Still refer to Figure 6 , showing feature 51 in more detail. In this example, feature 51 is of the ArUco or Charuco marking type, allowing the visual detector 52 to track the relative movement of the feature and the relative movement of the load 12. The features on the load may include any set of geometric shapes on the load, any markings, decals or printing or visual identification on the load, or any other unique features that can be recognized by computer vision and / or LIDAR or RADAR sensors. In addition, the feature may be a structural or structural feature or characteristic of the load or part of the load, or even include or consist of a specific color and / or light intensity of a certain paint, surface treatment, surface roughness, or may be created and / or modulated by any other material or surface or geometric property in the backscatter information, whether a structural element of the load, some passive marker or active marker, or any combination thereof.

[0053] Understandably, it is also possible to consider Figure 5 The opposite arrangement, wherein the feature is provided on the target and the feature detection system is provided on the payload.

[0054] Reference Figure 7, illustrates an example of a computer-implemented method for controlling a load suspended from a crane to align with a target. The method includes determining a motion of the load in at least one degree of freedom 701, and generating at least one compensation signal 702 indicative of the motion of the load. In response to the at least one compensation signal, a control signal 703 for the crane and / or the load motion compensation system LMCS is generated for controlling a reference attitude, preferably an absolute attitude, of the load in a reference coordinate system provided by a first reference sensor, such as, for example, the first reference sensor 41, the second reference sensor 42, or the third reference sensor 43. The reference coordinate system may be directly a world coordinate {W}, or by inference as described above. In some embodiments, depending on the configuration of the control system, such as, for example, in the case of no separate dedicated controller but only one master controller, the compensation signal 702 may be directly acquired / processed as the control signal 703. In other embodiments, such as receiving the compensation signal directly from the remote sensor by the master controller, the generation of the control signal 703 requires additional processing. In still other embodiments, the master controller may receive data indicative of the motion of the load and generate the compensation signal as a target set point and as an input for generating the control signal 703.

[0055] The method also includes receiving a relative motion signal 704 indicating relative motion between the target and the load from a feature detection system, such as feature detection system 50. The feature detection system generates the relative motion signal by detecting a feature, such as feature 51, and tracking the motion of the feature relative to the feature detection system. Typically, the method also includes generating a control signal for controlling the crane and / or the load motion compensation system LMCS in response to the relative motion signal to move the load to align with the target 706. It will be appreciated that the generation of the control signals in steps 702 and 706 may be superimposed or combined, and thus a superposition of signals may be provided. Therefore, the order of execution is not necessarily fixed in sequence, and any combination of signals may be merged into a single signal. In this example, the method also includes generating an alignment signal 705 in response to the relative motion signal, and wherein the control signal 706 for controlling the crane and / or the load motion compensation system LMCS is generated in response to the alignment signal.

[0056] Using the apparatus and methods described so far, a load can be aligned with a target; thereby allowing the crane and / or LMCS to move the load toward the target. Basically, the system and method presents the load and target as being fixedly aligned with each other, meaning that relative motion, such as rotation or translation, of the target is simulated via the control system so that the target maintains the same relative attitude as the target. This enables the operator to focus on the task of displacing the load toward the target via the manual controls. Because the offset between the load and the target appears "static" or "fixed" to the operator. And the operator no longer needs to consider interfering motions of the target. Therefore, the operator can use the manual controls to provide displacement commands to move the load toward the target.

[0057] During operation, the time and position at which the feature detection system detects the target and begins tracking provides relative motion from the time of detection, and there may be offsets in the alignment. In one embodiment, in order to close the offset during the step of moving the load to the target and beginning installation, the control system includes a manual control 33 for the operator to use. This will enable the operator to close any gaps remaining due to the offset.

[0058] In addition, the control system may include a human machine interface (HMI) to provide visual feedback of the alignment operation. The HMI will then be configured to display a view or image captured by the feature detection system, or alternatively a view or image captured by, for example, one or more cameras. The operator can use the visual feedback during the final step to close the gap caused by the offset. Alternatively, such feedback can be provided in a virtual manner by means of a 3D visualization or virtual or augmented reality display that can be combined with the camera feedback signal.

[0059] In another embodiment, the control system may apply a pattern classification system to the views or images captured by the feature detection system to identify whether the load is in a position to overlap with a target mounting point.

[0060] Reference Figure 8 , illustrates an example of a control scheme for an extended control system. An initial set point Xdes is input at point 80 and corrected for the vessel position of a reference sensor 82 which senses the position of the vessel 81. The main controller 83 uses the input 80 to control the LMCS actuator 84 which causes the blade 85 to move, resulting in a change in the blade position Xbl. Alternatively, the main controller 83 may control a crane to move the blade 85, or both. As an alternative to using S3 82, here the relative motion signal of the feature detection signal 52 may be used directly in a feedback control manner, such as, for example, visual servoing. Alternatively, the offset calculator 88 processes the relative motion signal of the feature detection system 87, similar to the method described with respect to Figure 5The described signal and calculates a new set point to correct the blade position Xbl to the new position Xbl' with its set point. Also in this embodiment, the operator input from the manual control 89 can still be used to correct the set point to Xbl" to minimize the deviation. These set points are then applied as control signals to, for example, the LMCS actuator. They can be summed to the input 80 of the main controller (not shown).

[0061] Reference Fig. 9 , Fig. 9 Shown with Figure 6 The same elements shown, the load alignment system may additionally include a second feature 61; in addition to the feature 51 on the load. Fig. 9 The feature plate 61 is located within the field of view 63 or line of sight of a feature detection system, in this embodiment a visual detector 52. The feature plate 61 forms part of the load alignment system and is arranged where the feature detection system is provided, in this embodiment in the nacelle 2. The feature plate 61 is also arranged so that the feature detection system 52 detects the second feature 61 as a target reference point, or as a guide close to a target reference point on the structure. Fig. 9 In the example of , the blades are provided with bolts 91 instead of holes 71 .

[0062] In order to achieve a perfect alignment, where the mounting position of the load is positioned facing the corresponding mounting position of the target, such as a bolt in a hole, further movement may be required. This is to perform assembly. In addition, the first feature 51, also implemented here as a feature plate, and the second feature plate 61 need to meet certain conditions, because it is required that the feature detection system 52 is able to determine the geometric relationship between the structural components of both the load and the target.

[0063] Reference Fig.10, a portion of a circular edge 90 of a load, in this example a wind turbine blade, is shown with bolts 91 extending from the edge 90, which will engage holes in a corresponding circular edge of a target, in this example a wind turbine nacelle. In this example, the feature plate 51 is mounted on the bolts 91 by means of a clamp 92, which allows for easy installation and removal before and / or after the blade and nacelle are combined. However, other means for mounting the feature plate 51 on the bolts 91 can be considered. Other structural elements for the feature plate 51 to be mounted thereon can be envisioned, as long as the geometric relationship between the structural element and the feature plate is known or can be derived. Or these can be inferred, for example, from CAD and design data of the load, target and / or feature plate. Alternatively, the feature plate can be defined as one or more visual features that can be detected directly, such as, for example, holes or bolts that will be detected by computer vision algorithms, lidar, radar or other means. Similarly, this also applies to the feature plate 62 to be mounted to the target. In other examples where both the load and the target include holes and the bolt is to be pushed through the holes of both the load and the target, e.g. Figure 6 As shown in the example of , the feature plates 51, 61 can be mounted on or near the holes 62, 71 in a fixed and inferable geometric relationship. As an example of a geometric relationship, a structural relationship of bolts and / or holes can be used. For example, this can be extracted from CAD data, drawings, design information, or from other 2D, 3D or dimensionless model data so that it can be matched with feature detection measurements.

[0064] Regardless of the specific details of the installation of the feature plates 51, 61, the position and / or attitude, i.e., the position and orientation, of the feature plates mounted on the load or target, respectively, needs to be known or at least inferred from the design. This is to understand the geometric relationship between the corresponding mounting positions of the feature plates and the load and target. For example, the blades need to be mounted on the nacelle in a predetermined position and / or orientation.

[0065] Where the load alignment system is extended with the second feature and arranged as described, the offset calculator can be configured to use the target reference points and the geometric relationship and determine the alignment pose of the load. This is the pose of the load 12 that allows the load to be mounted on the target without further compensation for the offset. For example, Figure 6In the example of , the mounting ring 60 is provided with bolt holes 62 to be aligned with bolt holes 71 on the mounting ring 70 of the blade 12. The aligned posture will indicate that the bolt holes of the load and the bolt holes of the target are aligned; thereby allowing, for example, through bolts to be guided through the holes. Therefore, in the case where the alignment posture of the load is determined, the alignment posture can be applied, for example stepwise, when generating the alignment signal in response to the relative motion signal. The alignment signal can involve a trajectory planner and / or a trajectory controller, and the alignment trajectory can also be calculated continuously in one step or in each calculation step.

[0066] exist Fig. 9 The extended load alignment system includes a second feature case, Figure 8 The manual controls 89 may be replaced by a trajectory controller which in turn may be configured to receive any input from the system. Alternatively, the trajectory controller may be used to "guide" the manual motion along a path of a predetermined or online calculated trajectory. The trajectory controller takes the output of the offset calculator and generates a trajectory to displace the load toward and engage the target. The trajectory controller output from the alignment system 50 generates a path or one or more set points for the crane or LMCS or both by generating an alignment signal taking into account the alignment attitude.

[0067] Refer again Fig. 9 To further enhance the determination of the geometric relationship between the first feature 51 and the feature plate 61 and the feature detection system 52, a third feature 64 or feature plate may be provided. The picture showing the second feature 61 and the third feature 64 in a single view allows the determination of the pose offset of the feature detection system 52 relative to the target 2, or at least the relative mounting position of the target as indicated by the pose that can be inferred from the feature plate 61. Fig. 9 In the example of , where the feature detection system 52 is positioned inside the nacelle of the wind turbine, the operator can simply take a picture and upload it, or provide it digitally to the control system 30 by any means. Or alternatively, to an operator or computing device, which will extract the relevant offsets from the picture, such as, for example, the offset of {S64} relative to {S61}, by additional calculations known to those skilled in the art. In the case where pictures are available, and / or by knowing the relative offset between the local coordinate systems of the two feature plates 61, 64 and by knowing the offset of the slave 62 relative to the sensor position 52, the relative offset of the slave camera or sensor frame 52 relative to the relevant position of the structure can be established more accurately. Pictures showing the two features 61, 64 present on the target can be taken before performing the alignment process. Alternatively, they can be taken or processed on the fly. In addition, in other embodiments, the relevant parameters can be entered into the control system by hand or through an auxiliary system.

[0068] Reference Fig.11 , illustrates another example of a method for controlling a load suspended from a crane to be aligned with a target. The method includes providing a reference coordinate system 901 by a first sensor. The reference coordinate system may be directly a world coordinate {W}, or may be inferred as described above. The method also includes providing a feature 902, such as feature 51, on the load 12 or target 2, and correspondingly providing a feature detection system 50 on the target 2 or load 12. The method includes controlling a reference pose 904, preferably an absolute pose, of the load within the reference coordinate system, and wherein the reference pose 904 of the load is controlled in response to at least one compensation signal. As will be appreciated, these steps of controlling the reference pose are performed in a continuous, repetitive manner. The method includes the feature detection system detecting the feature, tracking the motion of the feature, and generating a relative motion signal 907 indicating the relative motion between the target and the load. The method also includes generating an alignment signal 909 in response to the relative motion signal, and controlling the crane and / or the load motion compensation system in response to the alignment signal to align the load movement with the target 910.

[0069] like Fig. 9 As shown, the step of controlling the reference posture 904 may include two further steps or sub-processes of determining the movement of the load 905 in at least one, and preferably at least two, or even more preferably at least three degrees of freedom, and generating at least one compensation signal 906 indicative of the movement of the load.

[0070] Continue to refer to Fig. 9 , illustrates an example of an enhanced method. The method includes setting a second feature and preferably a third feature 903, such as setting the second feature 61 and the third feature 64. The second feature is set at a location where a feature detection system is located, and the feature detection system detects the second feature as a target reference point. Preferably, the third feature is also detected as a target reference point or at least used to derive or infer a related transformation. The method also includes calculating an offset of the load based on the target reference point 908, and applying the calculated offset when generating an alignment signal 909. In the enhanced example, the method also includes generating a displacement signal in response to the calculated offset and / or an input from a manual control, thereby controlling the crane and / or LMCS in response to the displacement signal for displacement of the load towards the target.

[0071] A control system comprising an extended load alignment system with a second feature and preferably a third feature and an alignment method corresponding to such a control system may provide the following benefit: the alignment of the load to the target can be performed taking into account an offset from the moment the feature was detected by the feature detection system, if such an offset exists. This is due to the second feature and / or the third feature, whose world coordinates can be inferred from the position relative to other reference sensors and allows to determine the exact geometrical relationship between all structural elements, sensors and features of interest of the load and the target. When the feature detection system is provided with a GNSS / INS device, a world coordinate system reference may be provided directly, for example as described above with respect to Figure 4 and Figure 5 described.

[0072] Although the present invention has been described above with reference to specific embodiments, the present invention is not intended to be limited to the specific forms set forth herein. On the contrary, the present invention is limited only by the appended claims, and other embodiments different from the specific embodiments described above are equally possible within the scope of the appended claims.

[0073] Furthermore, although exemplary embodiments have been described above with some exemplary combinations of components and / or functions, it will be appreciated that alternative embodiments may be provided by different combinations of components and / or functions without departing from the scope of the present disclosure. For example, the load motion compensation system may take a form different from that disclosed, for example, in WO2021002749A1. Furthermore, it is specifically contemplated that specific features described separately or as part of an embodiment may be combined with other separately described features or portions of other embodiments.

[0074] The present disclosure also relates to implementations reflected in the following clauses:

[0075] c1. A computer-implemented method for controlling a load suspended from a crane to align with a target, the method comprising:

[0076] determining motion of the load in at least one degree of freedom (701);

[0077] generating at least one compensation signal indicative of movement of the load (702); and

[0078] generating a control signal for a crane and / or a load motion compensation system LMCS in response to the at least one compensation signal for controlling a reference attitude of the load in a reference coordinate system provided by a first reference sensor (703);

[0079] receiving a relative motion signal (704) from a feature detection system indicating relative motion between the target and the payload;

[0080] A control signal for controlling a crane and / or a load motion compensation system LMCS is generated in response to the relative motion signal to move the load into alignment with the target (706).

[0081] c2. The method according to clause c1, further comprising:

[0082] generating an alignment signal (705) in response to the relative motion signal; and

[0083] Therein, a control signal (706) for controlling the crane and / or the load motion compensation system LMCS is generated in response to the alignment signal.

[0084] c3. A computer-implemented method according to clause c1 or c2, further comprising:

[0085] The feature detection system generates the relative motion signal by detecting a feature disposed on the payload and tracking the motion of the feature.

[0086] c4. A computer-implemented method according to any of the preceding clauses, further comprising:

[0087] generating a displacement signal in response to the calculated offset and / or input from a manual control; and

[0088] A control signal for controlling a crane and / or a LMCS is generated in response to the displacement signal for displacement of the load with respect to the target.

[0089] c5. A control box for controlling the alignment of a load suspended on a crane with a target, the control box comprising:

[0090] At least one controller (34) configured to perform the method according to any of clauses c1 to c4.

[0091] c6. A control system for controlling the alignment of a load suspended from a crane with a target, the control system comprising:

[0092] at least one reference sensor (41, 42, 43), the reference sensor (41, 42, 43) being configured to provide a reference coordinate system ({S41}, {S42}, {S43});

[0093] A load motion compensation system LMCS (35), the load motion compensation system LMCS (35) is used to control the reference posture of the load (12) in the reference coordinate system ({S41}, {S42}, {S43}), the load motion compensation system LMCS (35) comprising:

[0094] at least one motion sensor (41) arranged to determine motion in at least one degree of freedom and to generate at least one compensation signal indicative of the motion of the load; and

[0095] at least one motion compensating actuator (15) arranged to control the attitude of the load in response to the at least one compensation signal; and

[0096] A load alignment system, the load alignment system comprising:

[0097] a first feature (51), the first feature (51) being arranged on the load (12) or on the target (2);

[0098] a feature detection system (50) disposed on the target (2) or on the load (12), respectively, and configured to detect the feature (51), track the movement of the feature (51), and to generate a relative motion signal indicative of relative motion between the target (2) and the load (12); and

[0099] The control system comprises at least one controller (34), wherein the at least one controller (34) is configured to:

[0100] generating an alignment signal in response to the relative motion signal; and

[0101] In response to the alignment signal a control signal is generated for controlling a crane and / or a load motion compensation system LCMS for moving the load into alignment with the target.

[0102] c7. A control system according to clause c6, wherein the at least one controller is further configured to:

[0103] generating a displacement signal in response to the calculated offset and / or input from a manual control; and

[0104] In response to the displacement signal a control signal is generated for controlling a crane and / or a load motion compensation system LMCS for displacement of the load towards the target.

[0105] c8. A control system according to clause c6 or c7, wherein the at least one controller comprises:

[0106] A load motion compensation system LMCS controller (39), the load motion compensation system LMCS controller (39) being used to generate a LCMS control signal; and / or

[0107] an offset calculator (37, 88), the offset calculator (37, 88) being used to calculate an offset; and / or

[0108] A crane controller (36) is provided, wherein the crane controller (36) is used to generate a crane control signal.

[0109] c9. A control system according to any one of clauses c6 to c8, wherein

[0110] The control system includes a plurality of reference sensors;

[0111] wherein the plurality of reference sensors are arranged such that each sensor has a position expressed in a coordinate system of at least one other reference sensor; and

[0112] Therein, at least one reference sensor provides world coordinates.

[0113] c10. A control system according to any one of clauses c6 to c9, wherein the load motion compensation system (35) is configured to process the compensation signal and enable the motion compensation actuator to control the posture of the load to be in the reference posture.

[0114] c11. A control system according to any one of clauses c6 to c10, further comprising a human-machine interface HMI, wherein the human-machine interface is configured to display a view captured by the feature detection system; and / or

[0115] Manual controls for the operator are also included.

[0116] c12. A control system according to any one of clauses c6 to c11, wherein the load alignment system further comprises:

[0117] a second feature, the second feature being arranged where the feature detection system is provided so that the feature detection system detects the second feature as a target reference point; and

[0118] preferably a third feature, said third feature being arranged on said feature detection system so that said second feature and said third feature can be captured in a single camera view; and

[0119] Wherein the at least one controller is configured to calculate an offset based on at least the first feature and the second feature.

[0120] c13. A method for controlling a load suspended from a crane to align with a target, the method comprising:

[0121] A reference coordinate system is provided by a first sensor (901);

[0122] Setting a feature on the payload or on the target, and correspondingly setting a feature detection system on the target or on the payload (902);

[0123] controlling a reference posture of the payload in the reference coordinate system (904);

[0124] a feature detection system detects the feature, tracks movement of the feature, and generates a relative motion signal (907) indicative of relative motion between the target and the payload; and

[0125] generating an alignment signal (909) in response to the relative motion signal; and

[0126] A crane and / or a load motion compensation system is controlled (910) in response to the alignment signal to move the load into alignment with the target.

[0127] c14. The method according to clause c13, wherein controlling the reference posture (704) comprises: determining the motion of the load in at least two degrees of freedom (905);

[0128] generating at least one compensation signal indicative of movement of the load (906); and

[0129] Wherein, the reference posture of the payload is controlled in response to the at least one compensation signal.

[0130] c15. A method according to any one of clauses c13 to c14, comprising:

[0131] Setting a second feature (903), and more preferably a third feature, where the feature detection system is set; causing the feature detection system to detect the second feature and preferably the third feature as a target reference point;

[0132] c16. The method according to any one of clauses c13 to c15, further comprising:

[0133] generating a displacement signal in response to the calculated offset and / or input from a manual control; and

[0134] A crane and / or LMCS is controlled in response to the displacement signal for displacement of the load toward the target.

[0135] c17. A crane comprising a control system according to any one of clauses c6 to c12.

[0136] c18. A vessel comprising a crane and a control system according to any one of clauses c6 to c12.

[0137] c19. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to perform a method according to clauses c1 to c4 or according to clauses c13 to c16.

[0138] c20. A computer-readable data carrier having stored thereon a computer program product according to clause c19.

Claims

1. A control system for controlling the motion compensation of a load (12) suspended from a crane (11) and moving relative to a fixed external reference system ({W}), and for simultaneously controlling the alignment of the load (12) with a target (2), the control system comprising: A load motion compensation system LMCS (35), the load motion compensation system LMCS (35) is used to control the reference posture of the load (12) relative to the external reference system ({W}), wherein the LMCS (35) comprises: at least one motion sensor (41, 42, 43, 44, 45) arranged to determine the motion of the load (12) in at least one degree of freedom relative to the external reference system ({W}) and to generate at least one compensation signal (702) indicative of the motion of the load; and at least one LMCS actuator (15, 84) arranged to control the attitude of the load relative to the external reference frame ({W}) and responsive to the at least one compensation signal (702); and A load alignment system, the load alignment system comprising: a first feature (51), the first feature (51) being arranged on / in the load (12) or on / in the target (2); a feature detection system (50) disposed on / in the target (2) or on / in the payload (12), respectively, and configured to detect and track the motion of the feature (51), and to generate a relative motion signal (907) indicative of the relative motion between the target (2) and the payload (12); The control system comprises at least one controller (34, 39), wherein the controller is configured to: generating an alignment signal (705) in response to the relative motion signal (907), the alignment signal being different from the compensation signal (702); and A control signal (706) is generated in response to the alignment signal (705) for controlling the crane and / or the at least one LCMS actuator (84) to move the load into alignment with the target.

2. The control system according to claim 1, wherein: The at least one motion sensor (41, 42, 43, 44, 45) is configured to determine an absolute motion of a reference point ({BR}) on the load (12) relative to the fixed external reference frame ({W}), and to generate the compensation signal (702) based on the absolute motion; wherein the feature detection system (50) is configured to detect and track the feature (51) located on the payload (12) or on the target (2), and is configured to generate the relative motion signal (907) indicating the relative motion between the reference point ({BR}) on the payload (12) relative to a target reference system ({S7}) associated with the target (2); And wherein the control system is configured to represent the relative motion signal (907) in world coordinates based on the determined attitude of the reference point ({BR}) relative to the external reference system ({W}) and based on the measured relative attitude between the reference point ({BR}) and the local reference system ({S7}) to derive the control signal (706) for controlling the crane and / or controlling the at least one LCMS actuator (84) for moving the load (12) in synchronization with the target (2).

3. The control system according to claim 1 or 2, wherein: The control system (30) is configured to combine the compensation signal (702) and the alignment signal (705) to produce a superimposed signal or a combined signal (706), and to use the superimposed signal or the combined signal to control the crane (11) and / or the at least one LMCS actuator (84) to maintain the load (12) aligned with the target by simulating relative rotation and translation between the load (12) and the target (2) by dynamically repositioning the load (12) and maintaining the load (12) in a substantially same relative posture including a static offset relative to the target.

4. The control system according to any one of claims 1 to 3, wherein: The feature detection system (50) comprises: a visual detector (52) positioned on or in the target (2) and having a field of view (63) directed toward the first feature (51) arranged on / in the load (12), and A processor (53) configured to process detector signals received from the visual detector (52) to allow tracking of the feature (51) and to generate the relative motion signal (907).

5. The control system according to any one of claims 1 to 4, wherein: The load is a wind turbine blade (12) suspended from the crane (11) mounted on the vessel (9), the wind turbine blade (12) being movable relative to the external reference system ({W}); wherein the target is a nacelle (2) of a wind turbine generator (1); And wherein the wind turbine blade (12) is elongated and defines a blade root (17) located at a distal end (90) and associated with a blade root reference system ({BR}).

6. The control system according to claim 5, wherein: The feature detection system (50) is provided with the visual detector (52) inside the nacelle (2), the visual detector (52) being in a fixed attitude, for example mounted on a tripod (57) placed on the floor inside the nacelle (2), the visual detector (52) having a field of view (63) pointing outward through a mounting ring (60) of the nacelle (2) and observing towards the feature (51) arranged on the blade root (17) in a fixed position relative to the blade root reference system ({BR}), wherein, optionally, the feature (51) is an ArUco marker, a ChArUco marker or a plate provided with a plurality of structural features located in a fixed geometric arrangement known to the control system.

7. The control system according to claim 6, wherein: The load alignment system additionally includes a feature plate (61) located inside the cabin (2) and within the field of view (63) of the visual detector (52), wherein the feature detection system (50) is configured to detect the feature plate (61) as a target reference point associated with a local reference system ({S7}) of the visual detector (52) located in a fixed posture inside the cabin (2).

8. A control system according to any one of claims 5 to 7, wherein: The wind turbine blade (12) comprises a blade mounting member (91), such as a bolt, disposed at the distal end portion (90), the blade mounting member (91) being configured to be connected to a corresponding mounting member (62), such as a bolt hole, disposed at a mounting location (60) at the nacelle (2); And wherein the feature plate (51) is detachably mounted to the blade mounting member (91) by means of a clamp (92) to allow the feature plate (51) to be removed after the wind turbine blade (12) is secured to the nacelle (2).

9. The control system according to any one of claims 1 to 8, wherein: The at least one controller (34, 39) is further configured to: generating a displacement signal in response to the calculated offset and / or input from a manual control (33); and In response to the displacement signal a control signal is generated for controlling a crane and / or a load motion compensation system LMCS for displacement of the load towards the target.

10. The control system according to any one of claims 1 to 9, wherein: The at least one controller (34, 39) comprises: a LMCS controller (39), the LMCS controller (39) being configured to generate the LCMS control signal; and / or an offset calculator (37, 88) for calculating an offset; and / or A crane controller (36) is provided, wherein the crane controller (36) is used to generate a crane control signal.

11. A control system according to any one of claims 1 to 10, wherein The control system includes a plurality of reference sensors (41, 42, 43, 44, 45); in, the plurality of reference sensors being arranged such that each sensor has a position expressed in a coordinate system of at least one other reference sensor; and Therein, at least one reference sensor provides world coordinates.

12. The control system according to any one of claims 1 to 11, further comprising a human-machine interface HMI (31), wherein: The human-machine interface is configured to display a view captured by the feature detection system; and / or Manual controls for the operator are also included.

13. The control system according to any one of claims 1 to 12, wherein: The load alignment system further comprises: a second feature (61), the second feature (61) being arranged at a location where the feature detection system (50) is arranged so that the feature detection system detects the second feature as a target reference point; and Wherein the at least one controller is configured to calculate an offset based on at least the first feature and the second feature.

14. The control system according to claims 6 and 13, wherein: The feature detection system (50) includes a third feature (64) arranged at a position on the visual detector (52) that allows the second and third features (61, 64) to be captured in a single image acquired by an operator located at or within the nacelle (2), and wherein the control system (30) is configured to receive the image including both the second and third features (61, 64) and to derive from the image an attitude offset of the visual detector (52) relative to the nacelle (2) and the second feature (61).

15. A method for controlling alignment of a load suspended from a crane with a target, the method comprising: determining motion of the load in at least one degree of freedom (701); generating at least one compensation signal indicative of movement of the load (702); and generating a control signal for a crane and / or a load motion compensation system LMCS in response to the at least one compensation signal for controlling a reference attitude of the load in a reference coordinate system provided by a first reference sensor (703); receiving a relative motion signal (704) from a feature detection system indicating relative motion between the target and the payload; A control signal for controlling a crane and / or a load motion compensation system LMCS is generated in response to the relative motion signal to move the load into alignment with the target (706).

16. The method according to claim 15, further comprising: generating an alignment signal (705) in response to the relative motion signal; and Therein, the control signal (706) for controlling the crane and / or the load motion compensation system LMCS is generated in response to the alignment signal.

17. The method according to claim 15 or 16, further comprising: The feature detection system generates the relative motion signal by detecting a feature disposed on the payload and tracking the motion of the feature.

18. The method according to any one of claims 15 to 17, further comprising: generating a displacement signal in response to the calculated offset and / or input from a manual control; and A control signal for controlling a crane and / or a LMCS is generated in response to the displacement signal for displacement of the load with respect to the target.

19. A method for controlling alignment of a load suspended from a crane with a target, the method comprising: A reference coordinate system is provided by a first sensor (901); Setting a feature on the payload or on the target, and correspondingly setting a feature detection system on the target or on the payload (902); controlling a reference posture of the payload in the reference coordinate system (904); The feature detection system detects the feature, tracks movement of the feature, and generates a relative motion signal (907) indicative of relative motion between the target and the payload; and generating an alignment signal (909) in response to the relative motion signal; and A crane and / or a load motion compensation system is controlled in response to the alignment signal to move the load into alignment with the target (910).

20. The method according to claim 19, wherein: Controlling the reference posture (704) includes: determining motion of the load in at least two degrees of freedom (905); generating at least one compensation signal indicative of movement of the load (906); and Wherein, the reference posture of the payload is controlled in response to the at least one compensation signal.

21. The method according to claim 19 or 20, comprising: providing a second feature (903) and more preferably a third feature where the feature detection system is provided; The feature detection system is caused to detect the second feature and preferably the third feature as target reference points.

22. The method according to any one of claims 19 to 21, further comprising: generating a displacement signal in response to the calculated offset and / or input from a manual control; and A crane and / or LMCS is controlled in response to the displacement signal for displacement of the load toward the target.

23. A crane comprising a control system according to any one of claims 1 to 14.

24. A vessel comprising a crane and a control system according to any one of claims 1 to 14.

25. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to perform the method according to any one of claims 15 to 22.

26. A computer-readable data carrier having stored thereon a computer program product according to claim 25.

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