Method for controlling the attitude of a blade lifting yoke for a rotor blade for a wind turbine and blade lifting yoke

Abstract

A method for controlling the attitude of a blade lifting yoke (1) for a rotor blade (2) for a wind turbine is disclosed. The blade lifting yoke used includes a yoke unit (6) and a suspension unit (7) connected to a crane (41) at a crane attachment point (P). The yoke unit includes a base (61) and a holding device (61) including a lower clamp member (64) and an upper clamp member (65). The suspension unit includes a plurality of actuators (71, 72, 73, 74), each attached to the yoke unit at a yoke attachment point (70) and extending from the yoke attachment point toward a crane attachment point, such that the actuators are angled relative to one another. The first actuator (71), the second actuator (72), and the third actuator (73) are individually controlled by a control unit to change the length of at least one of the first actuator, the second actuator, and the third actuator to move the position of the lower clamp member relative to the crane attachment point.

Description

[Technical Field]

[0001] The present invention relates to a method for controlling the attitude of a blade lifting yoke for rotor blades for a wind turbine, the blade lifting yoke comprising a yoke unit and a suspension unit, the yoke unit including a base and a retention device, the suspension unit being connected to a crane at a crane attachment point, the retention device comprising a lower clamping member configured to support the rotor blade and an upper clamping member configured to press the rotor blade against the lower clamping member and spaced apart from the lower clamping member in a height direction perpendicular to the longitudinal direction, the suspension units comprising a plurality of actuators each attached to the yoke unit at a yoke attachment point and extending from the yoke attachment point towards a crane attachment point, the yoke attachment points being spaced apart from one another so that the actuators are angled relative to one another. The present invention further relates to a blade lifting yoke for rotor blades for a wind turbine. [Background technology]

[0002] A blade lifting yoke is used to hold rotor blades for installation on a wind turbine while they are lifted by a crane from a ground or ship-based location to the wind turbine nacelle, with the rotor blades held by the blade lifting yoke so that their longitudinal axes extend parallel to the longitudinal direction of the blade lifting yoke.

[0003] When attaching rotor blades to a wind turbine hub, the bolts at the base of the rotor blade must be precisely aligned with the openings in the hub. This can be done by using a crane to move the entire blade lifting yoke that holds the rotor blade, by rotating the hub, and / or by changing the tilt of the hub. However, hydraulically driven blade tilting systems on wind turbines cannot move freely due to limitations imposed by the stroke length of the hydraulic cylinders, and electrically powered blade tilting systems can only move if the wind turbine is already powered, which may not be the case, especially offshore.

[0004] Some prior art blade lifting yokes offer the possibility of tilting and tilting rotor blades by extending and retracting actuators, typically hydraulic cylinders, but as rotor blades become larger, small changes in the attitude of the blade lifting yoke can result in large movements at the root, making it difficult to handle large rotor blades with sufficient precision, especially in high winds.

[0005] Another problem, which becomes increasingly problematic with larger rotor blades, is that the blade lifting yoke must also become larger and more robust, making it more difficult to control when latching and releasing the rotor blade. The latter can result in the blade lifting yoke prematurely slipping off the rotor blade and risking swinging back and striking the rotor blade, or the blade lifting yoke's weight being carried by the rotor blade, potentially overloading the rotor blade. When viewed longitudinally, the blade lifting yoke typically has the overall shape of the letter C, spanning either the leading or trailing edge of the rotor blade, while the opposite edge of the rotor blade protrudes away from the body of the C. This causes the blade lifting yoke to become unbalanced when not carrying a rotor blade, which is often compensated for by providing counterweights at the free ends of the legs of the C, thereby reducing the risk of swinging motion when the rotor blade is released. However, the counterweights make the blade lifting yoke even heavier and more difficult to handle. The delicate weight balance also means that it is typically necessary to have several different blade lifting yokes for different sizes and types of rotor blades. Summary of the Invention [Problem to be solved by the invention]

[0006] Against this background, it is an object of the present invention to provide a method that allows for more precise control of the blade lifting yoke during operation. [Means for solving the problem]

[0007] This and further objects are achieved by the method set forth in the introduction, the method being further characterized in that the first, second and third actuators are individually controlled by a control unit to vary a length of at least one of the first, second and third actuators and move a position of the lower clamp member relative to a crane attachment point, the yoke attachment points to which the first and second actuators are attached being spaced apart from one another in a longitudinal direction, and the yoke attachment point to which the third actuator is attached being spaced apart in a width direction from at least one of the yoke attachment points to which the first and second actuators are attached, the width direction being perpendicular to the longitudinal and height directions.

[0008] This allows the blade lifting yoke's overall center of gravity to remain in the same vertical plane as the crane attachment point when viewed longitudinally, even when loads change, for example, when latching or releasing the rotor blade. Having the center of gravity vertically below the crane attachment point allows the blade lifting yoke, which holds the rotor blade, to tilt about its center of gravity, which was not possible with prior art blade lifting yokes. This makes it easier to control the tilt of the blade lifting yoke, making handling of the rotor blade less susceptible to external factors such as wind. Precise control of tilt can be particularly advantageous when connecting rotor blades to the hub of a wind turbine, where the geometric center of the blade root must be aligned with the geometric center of the hub. Controlling tilt in this way also allows the rotor blades to be tilted with precision and to align the blade root bolts with the hub openings, because undesired translation of the rotor blade's geometric center as a result of tilting is limited when the rotor blade's geometric center is close to the center of gravity.

[0009] The center of gravity can also be kept in the same vertical plane as the crane attachment point when viewed spanwise, thereby providing tilt stability and / or control in addition to or instead of pitch stability and / or control. This allows, for example, the rotor blade root to be kept substantially stationary while the rest of the rotor blade is tilted, thereby allowing alignment of the root with the hub of the wind turbine, for example, when the root bolts are at an angle relative to the openings in the hub through which they are inserted.

[0010] Another benefit of keeping the center of gravity aligned with the crane attachment point is that the same blade lifting yoke can be used for many different rotor blade designs, where the rotor blade center of gravity, and thus the overall center of gravity, is located in many different positions relative to the lower clamping member. This can be due, for example, to the center of gravity being in different positions within the blade profile or rotor blades having different sizes or weights. The shift in the center of gravity position can then be compensated for by changing the length of one or more of the actuators before starting the lift.

[0011] In addition to providing more stability when carrying the rotor blades, the ability to move the position of the lower clamp member relative to the location of the crane attachment point also allows for better stability of the blade lifting yoke itself, for example, by allowing one side to compensate for being heavier than the other, thereby reducing or even eliminating the need for counterweights.

[0012] The counterweight is typically mounted high on the blade lifting yoke when viewed in the height direction, so removing or reducing the counterweight results in a lower center of gravity of the blade lifting yoke when viewed in the longitudinal direction. This in turn means that the center of gravity of the blade lifting yoke, and thus the center of gravity of the entire blade lifting yoke and rotor blades, moves closer to the geometric center of the root of the rotor blade carried by the blade lifting yoke. As also mentioned above, this facilitates accurate tilting of the rotor blades and therefore easier connection to the hub of the wind turbine.

[0013] The actuator can be selected from the group consisting of, for example, a hydraulic linear cylinder, an electric linear cylinder, a cable system including one or more winches with electric or hydraulic drives, a rack and pinion, a threaded rod, and combinations thereof.

[0014] The yoke attachment points may be provided on the retainer or on the base, depending on, for example, the load-bearing capacity of different parts of the yoke unit. The yoke attachment points are advantageously located far from each other to allow optimal adjustment of the rotor blade tilt and other attitudes. The yoke attachment points may be embodied as, for example, brackets, braces, hooks, bolts, threaded openings, etc. The actuator may be provided with hooks, shackles, bolts, etc. for interconnecting with the yoke attachment points.

[0015] The retaining device or base may comprise a frame having the shape of the letter C and spanning the edge of the rotor blade, preferably the leading edge of the rotor blade, during operation.

[0016] In one embodiment, the method further includes varying the length of a fourth actuator, the fourth actuator being attached to a yoke attachment point spaced longitudinally from the yoke attachment point at which the first actuator is attached and located in the same widthwise plane as the yoke attachment point at which the second actuator is attached, the fourth actuator being independently controlled by a control unit. In this embodiment, it may be advantageous for the yoke attachment points at which the first and third actuators are attached to also be located in the same widthwise plane, the plane being spaced longitudinally from the plane at which the yoke attachment points at which the second and fourth actuators are attached. This allows for the use of two sets of actuators when stabilizing or changing pitch and / or tilt is required, resulting in better control of the blade lifting yoke. Using two sets of actuators may also reduce torsional loads on the rotor blades.

[0017] In one embodiment, the root of the rotor blade is aligned with the hub of the wind turbine by varying the length of actuators attached to spanwise spaced yoke attachment points, thereby varying the pitch of the rotor blade.

[0018] In one embodiment, all actuators are retracted to raise the blade lifting yoke or extended to lower the blade lifting yoke. This only serves for smaller movements of the blade lifting yoke, but can be advantageous in the final stages of rotor blade installation because this height adjustment can be performed by the yoke operator and therefore does not require a crane operator.

[0019] When the blade lifting yoke that holds the rotor blades is simply lifted and not affected by external factors such as wind, the position of the center of gravity remains substantially unchanged. However, this is rare. Therefore, it may be advantageous to perform continuous adjustment of the actuator length. As an example, when the rotor blades are released, the blade lifting yoke's hold is usually gradually released, so that the center of gravity gradually moves from the position of the overall center of gravity to the position of the center of gravity of the blade lifting yoke. By gradually adjusting the actuator length, good control of the blade lifting yoke is always maintained, thereby reducing the risk of, for example, the blade lifting device suddenly moving at the end of the release sequence.

[0020] The actuator length can be changed according to a predetermined pattern that can be programmed into the control unit, although it is currently believed to be advantageous for the change to occur in response to changes in the load affecting the blade lifting yoke. Just as some portions of the rotor blade lift can follow a predetermined pattern, there can also be a combination of some predetermined patterns that are initiated following input from an operator that a particular process step has been reached or completed, while other portions are controlled solely based on live data and / or user input.

[0021] The control unit can communicate data with a control system, such as an external control system, that may be performing live calculations of required changes to the actuator length. These calculations can be based on data obtained from sensors on or within the blade lifting yoke, weather data, and / or user input, such as an operator's indication that the rotor blades need to be lowered, lifted, tilted, or inclined. Sensors on or within one or more of the actuators, such as pressure or force sensors, can provide data regarding the loads acting on each actuator. Other examples of sensors are stroke length sensors and angle sensors. Vision-based sensor systems can also be used to provide data regarding the status and / or position of the actuators, yoke units, or other related components.

[0022] In a second aspect of the present invention, the above and further objects are achieved by a blade lifting yoke of the kind mentioned in the introduction, further characterized in that the first, second and third actuators are individually controllable by a control unit, each of the actuators having an adjustable length and at least controllable so that one can be extended simultaneously with the other being retracted, the yoke attachment points to which the first and second actuators are attached being spaced apart from one another in the longitudinal direction, and the yoke attachment point to which the third actuator is attached being spaced apart in the width direction from at least one of the yoke attachment points to which the first and second actuators are attached, the width direction being perpendicular to the longitudinal and height directions.

[0023] The above description of the method includes several example embodiments of the blade lifting yoke, and it should be understood that these and the advantages they provide also apply to the second aspect of the invention. Similarly, it should be understood that the embodiments and advantages described below with reference to one aspect of the invention also apply to the other aspects, unless otherwise specified. Generally, embodiments and advantages will be described only with reference to one embodiment to avoid undue repetition.

[0024] In the following description, embodiments of the present invention will be described with reference to the following schematic drawings. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram of a wind turbine and a crane lifting a blade lifting yoke holding a rotor blade. [Figure 2] FIG. 1 is a perspective view of a portion of a rotor blade being carried by a blade lifting yoke suspended from a crane. [Figure 3] FIG. 2 is a cross-sectional view of a rotor blade carried by a blade lifting yoke. [Figure 4] FIG. 1 is a cross-sectional view of a blade lifting yoke and rotor blades suspended from a crane. [Figure 5] 4 but with the rotor blades carried by the blade lifting yoke. [Figure 6] 5, but showing three different positions of the blade lifting yoke; and [Figure 7] FIG. 10 is a perspective view of another blade lifting yoke for holding rotor blades. DETAILED DESCRIPTION OF THE INVENTION

[0026] Referring first to Figure 1, a blade lifting yoke 1 holds a rotor blade 2 as it is lifted by a crane 4 into a nacelle 31 of a wind turbine 3. Here, the installation is offshore, with both the crane and the wind turbine supported on the seabed 51 below sea level 52, although it should be understood that the present invention is not limited to offshore use and can be used for any operation involving lifting rotor blades.

[0027] In the following, the same reference numbers are used for elements having substantially the same function, even if they are not necessarily identical.

[0028] The blade lifting yoke 1 is shown in more detail in Figures 2 and 3, including a portion of the rotor blade 2. The blade lifting yoke comprises a yoke unit 6 and a suspension unit 7, the yoke unit comprising a base 61 and two retaining devices 62 arranged at opposite ends of the base and spaced apart from each other in the longitudinal direction L.

[0029] As best seen in FIG. 2, the suspension unit 7 is connected to the hook 41 of the crane at a crane attachment point P.

[0030] Each retention device 62 comprises a frame 63 in the shape of the letter C, with a lower clamping member 64 on the lower leg 631 of the C that supports the rotor blade 2, and an upper clamping member 65 on the upper leg 632 that presses the rotor blade against the lower clamping member. Here, the C-shape straddles the leading edge 21 of the rotor blade, with the trailing edge 22 extending outward from the C-shape. This is considered advantageous as the part of the rotor blade closer to the leading edge is heavier than the part closer to the trailing edge, although it is not excluded that the C-shape could also straddle the trailing edge.

[0031] The lower clamp member 64 and the upper clamp member 65 are spaced apart from each other in a height direction H that is perpendicular to the longitudinal direction L. The width direction D is perpendicular to both the longitudinal direction and the height direction. Here, the holding device further includes a support member 66 that is spaced apart from the lower clamp member 64 in the width direction.

[0032] 3, looking in the longitudinal direction L, a reinforcing web 23 extends vertically inside the rotor blade 2, and lower and upper clamping members 64, 65 engage the rotor blade where the web joins the rotor blade shell 24. The center of gravity 8 of the blade lifting yoke and the entire rotor blade is located near the web, slightly towards the trailing edge of the rotor blade.

[0033] In the embodiment of Figure 2, the suspension unit 7 includes four yoke attachment points 70, two on each support device 62, spaced apart in the width direction W. Actuators 71, 72, 73, 74 are connected at one end to each yoke attachment point and at the other end to cables 75 that extend to a crane attachment point P. Because the yoke attachment points 70 are spaced apart in both the width direction W and the longitudinal direction L, the actuators extend at angles to each other in both the longitudinal and width directions. The widthwise distance between the yoke attachment points is slightly different in Figures 2 and 3.

[0034] The actuators 71, 72, 73, 74 shown in Figure 2 are all hydraulic cylinders, although it will be appreciated that other types of actuators may be used.

[0035] 4 and 5 show the procedure for placing the rotor blades 2 in / onto the blade lifting yoke 1.

[0036] 4 shows the center of gravity 81 of the blade lifting yoke 1 alone located to the left of the clamp members 64, 65, and the center of gravity 82 of the rotor blade 2 alone to the right of the web 23. The crane attachment point P is located vertically above the center of gravity 81 of the blade lifting yoke 1, as shown by the dashed-dotted line. This is achieved by retracting the left actuator 71 and extending the right actuator 73 compared to what is shown in FIG. 2.

[0037] As shown by the arrows in Figure 4, when rotor blade 2 is inserted into retaining device 62 (or blade lifting yoke 1 is displaced in the opposite direction), the rotor blade comes to rest on lower clamp member 64 and support member 66, and the overall center of gravity 8 is then located as shown in Figure 5. To compensate for this displacement of the center of gravity of the load carried by the crane, left actuator 71 is extended and right actuator 73 is retracted so that crane attachment point P is displaced to the right until it is positioned vertically above center of gravity 8, as shown by the arrows.

[0038] Figure 6 shows three positions of the same blade lifting yoke 1 holding rotor blades 2, with the position on the left corresponding to the example in Figure 5. In the position shown in the center of Figure 6, the blade lifting yoke 1 is tilted to the right by retracting the left actuator 71 and extending the right actuator 73, and in the position shown on the right, the blade lifting yoke 1 is tilted to the left by extending the left actuator 71 and retracting the right actuator 73. As shown by lines A and B, the vertical distance between the crane attachment point P and the center of gravity 8 remains the same regardless of tilting, which contributes to the stability and control of the blade lifting yoke 1 in use.

[0039] 6 can serve several different purposes, including facilitating the latching or release of the rotor blades and compensating for wind loads, but is particularly advantageous in allowing the rotor blade roots (not shown) to be aligned with the hub of the wind turbine.

[0040] As shown in Figure 6, the height direction H, defined as extending between the lower clamping member 64 and the upper clamping member 65, rotates with the blade lifting yoke when tilted in this manner. The same is true for the direction W, which is perpendicular to the height direction.

[0041] In the embodiments of Figures 2, 4, 5 and 6, the actuators 71, 72, 73, 74 can be retracted and extended independently, but it is also possible for two actuators to be interconnected so that retracting one extends the other and vice versa.

[0042] Another embodiment of a blade lifting yoke 1 for holding a portion of a rotor blade 2 is seen in Figure 7. In this embodiment, the base 61 has the shape of the letter C, and the holding device comprises a lower portion (not visible) on the lower leg of the C and an upper portion 621 on the upper leg 611 of the C. The C-shape straddles the leading edge 21 of the rotor blade, with the trailing edge 22 extending outward from the C-shape. It should be understood that an upper clamping member 65 is disposed on the upper portion 621 of the holding device, and a lower clamping member (not visible) is found on the lower portion of the holding device such that the rotor blade is held in the same manner as shown in Figure 3, except that this embodiment does not include a support member.

[0043] In Figure 7, the first actuator 71 is an electric cable winch, while the second and third actuators 72, 73 are hydraulic actuators as in Figure 2. This combination is intended to illustrate different embodiments of the actuators, although it is usually advantageous for all of the actuators to be of the same type.

[0044] Here, the yoke attachment points to which the first and second actuators 71 , 72 are connected are found on the upper portion 621 of the holding device, and the yoke attachment point to which the third actuator 73 is connected is on the base 61 .

[0045] The various portion embodiments of the blade lifting yoke 1 described herein can be combined in various ways, which may result in a blade lifting yoke different from that shown. The embodiments shown in the drawings are intended as examples only and variations are possible within the scope of the claims.

Claims

1. 1. A method for controlling the attitude of a blade lifting yoke for a rotor blade for a wind turbine, comprising: the blade lifting yoke comprises a yoke unit and a suspension unit; The yoke unit includes a base and a retaining device; the suspension unit is connected to a crane at a crane attachment point; the holding device includes a lower clamp member configured to support the rotor blade, and an upper clamp member configured to press the rotor blade against the lower clamp member and spaced apart from the lower clamp member in a height direction perpendicular to the longitudinal direction, the suspension unit comprises a plurality of actuators, each attached to the yoke unit at a yoke attachment point and extending from the yoke attachment point toward the crane attachment point; the yoke attachment points are spaced apart from one another so that the actuators are angled relative to one another; a first actuator, a second actuator, and a third actuator independently controlled by a control unit to vary a length of at least one of the first actuator, the second actuator, and the third actuator to move a position of the lower clamp member relative to the crane attachment point; the yoke attachment points to which the first actuator and the second actuator are attached are spaced apart from one another in the longitudinal direction; the yoke attachment point to which the third actuator is attached is spaced apart in a width direction from at least one of the yoke attachment points to which the first actuator and the second actuator are attached; The method, wherein the width direction is perpendicular to the length direction and the height direction.

2. changing the length of a fourth actuator attached to a yoke attachment point spaced apart in the longitudinal direction from the yoke attachment point to which the first actuator is attached, extending in the width direction and located in the same plane as the yoke attachment point to which the second actuator is attached; The method of claim 1 , wherein the fourth actuator is individually controlled by the control unit.

3. 3. The method of claim 1, wherein the rotor blade roots are aligned with the hub of the wind turbine by changing the lengths of actuators attached to yoke attachment points spaced apart in the spanwise direction, thereby changing the pitch of the rotor blades.

4. 4. The method according to claim 1, wherein all actuators are retracted to raise the blade lifting yoke or extended to lower the blade lifting yoke.

5. 5. A method according to one or more of the preceding claims, wherein the length of the actuator is changed in response to a change in load acting on the blade lifting yoke.

6. 6. The method according to one or more of the preceding claims, wherein one or more control units are in data communication with an external control system.

7. 7. The method of claim 1, wherein the calculation of the required change to the length of one or more actuators is based on data obtained from sensors on or provided at the blade lifting yoke, weather data, and / or user input.

8. 1. A blade lifting yoke for a rotor blade for a wind turbine, comprising: the blade lifting yoke comprises a yoke unit and a suspension unit; The yoke unit includes a base and a retaining device; the suspension unit includes a crane attachment point; the holding device includes a lower clamp member configured to support the rotor blade, and an upper clamp member configured to press the rotor blade against the lower clamp member and spaced apart from the lower clamp member in a height direction perpendicular to the longitudinal direction, the suspension unit comprises a plurality of actuators, each attached to the yoke unit at a yoke attachment point and extending from the yoke attachment point toward the crane attachment point; the yoke attachment points are spaced apart from one another so that the actuators are angled relative to one another; the first actuator, the second actuator, and the third actuator are individually controllable by a control unit; each of said actuators having an adjustable length and at least controllable such that one can be extended simultaneously with the other being retracted; the yoke attachment points to which the first actuator and the second actuator are attached are spaced apart from one another in the longitudinal direction; the yoke attachment point to which the third actuator is attached is spaced a widthwise distance from at least one of the yoke attachment points to which the first actuator and the second actuator are attached; A blade lifting yoke, wherein the width direction is perpendicular to the length direction and the height direction.

9. a fourth actuator disposed spaced apart from the first actuator in the longitudinal direction, extending in the width direction and in the same plane as the second actuator; The blade lifting yoke of claim 8 , wherein the fourth actuator is individually controlled by the control unit.

10. the blade lifting yoke includes two holding devices at opposite ends of the base, the holding devices being spaced apart from each other in the longitudinal direction; the first actuator and the third actuator are disposed on one of the holding devices; 10. A blade lifting yoke according to claim 8 or 9, wherein the second actuator and, if present, the fourth actuator are arranged on the other holding device.

Images