A tension constraint distribution control method of a three-rope auxiliary butt joint system of a marine wind power blade

Abstract

This invention discloses a tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades, applicable to hoisting and docking where three winches are integrated into the tower / hub and the cables are subjected to unidirectional force. The method includes: pre-tensioning and calibrating the three cables; during the approach phase, the main crane completes macroscopic displacement, and the three winches maintain constant tension while superimposing virtual damping to suppress sway; the active rotating head adjusts phase, and alignment is confirmed based on laser interlock signals; after alignment, the main crane switches to either follow-up or floating mode, and the three winches take over the docking; during the docking phase, task space control requirements are generated based on the target state, and tension distribution and redistribution are performed under the constraints of the lower limit of cable pretension, the upper limit of rated tension, and the rate of change, driving the three winches to collaboratively pull in and complete the fit; if the interlock fails, the tension is abnormal, or there is a slack trend, a retraction strategy is executed. This method improves the stability and safety of docking under sea state disturbances, reduces impact, and minimizes the risks of slack and overload.

Description

Technical Field

[0001] This invention relates to the field of offshore wind power installation and offshore lifting control technology, and in particular to a control method for precise docking of offshore wind turbine blades using a three-winch pull-in method. Specifically, under sea disturbance conditions, based on segmented control, laser interlock trigger control switching, and constrained distribution of three-winch tension, a safe, stable, and low-impact docking of the blade and hub is achieved. Background Technology

[0002] Offshore wind turbine blade hoisting and docking operations typically involve: the main crane moving the blade near the hub, gradually aligning the blade's orientation, and finally fitting the blade root to the hub and tightening the bolts. The offshore environment presents challenges such as wave-induced hook heave and swaying, and wind-induced random disturbances, which can cause fluctuations in the relative position and orientation of the blade during the approach and docking phases.

[0003] Traditional methods relying on the fine movements of the main crane and manual traction have the following problems: large impact during docking and low efficiency. Under disturbance, the blades and hub repeatedly "approach-deviate-recorrect," making the docking process time-consuming and with frequent impacts; high rope risk. When using winch-assisted docking, if there is a lack of control strategies for multi-winch coordination, some ropes may become slack (loss of control) or experience sudden increases in stress (overload risk); unreliable control switching. If the main crane rigidly dominates the docking phase, it is easy to have "control conflicts" with the winch's fine pulling movements, inducing impacts and oscillations.

[0004] Therefore, a tension constraint distribution control method is needed for a three-rope assisted docking system for offshore wind turbine blades to achieve stable approach, reliable weight transfer, and precise pull-in docking with controllable tension without relying on continuous high-precision optical error input. Summary of the Invention

[0005] The purpose of this invention is to provide a tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades, in order to solve the technical problems of unstable control during the docking stage under sea state disturbances, high risk of rope slack and overload, and unreliable switching of control between the main crane and the winch.

[0006] This invention provides the following technical solution:

[0007] A tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades is applied to a pull-in docking system in which three winches are installed inside the tower or hub, three cables are respectively connected to the upper, lower, and side connection points of the blade root, and the cables can only withstand tensile force. The method includes the following steps: The three cables are pre-tensioned and calibrated to ensure that the cable tension meets the preset pre-tension threshold, so as to avoid slack during the approach and docking stages. In approach mode, the main crane is controlled to perform macroscopic displacement, while the three winches are controlled to perform constant tension follow-up and superimposed virtual damping to suppress swaying. This constant tension follow-up is achieved by performing tension closed-loop control on the three winches respectively, and the virtual damping is achieved by introducing a suppression term related to the swaying speed into the tension closed-loop command. Preferably, this step also includes fusing the output of the inertial measurement unit to generate a disturbance compensation command to offset the effect of wave-induced inertial disturbance of the spreader on the tension. The system acquires the alignment success interlock signal output by the laser interlock guidance system. When the signal continuously meets the preset confirmation time threshold, it triggers the switch from proximity mode to docking mode and controls the main crane to enter follow-up or floating mode. In docking mode, task space control requirements are generated based on the target docking status. Under the conditions of satisfying the pretension lower limit constraint, rated upper limit constraint and tension change rate constraint of the three cables, the target tension and / or target take-up and release amount of the three winches are calculated through tension optimization allocation, and the three winches are driven to work together to pull in and complete the docking. The task space control requirements are generated by impedance control or admittance control, which takes the docking error and error change rate as input and outputs the control requirements for driving the bonding. The tension optimization allocation simultaneously meets the following objectives: to make the effect produced by the target tension approximate the task space control requirements; to suppress the tension imbalance of the three cables and reduce the tension difference or variance of the three cables; and to suppress the sudden change of the target tension in adjacent control cycles. Preferably, in the docking mode, the active rotating head is further controlled to perform phase adjustment to meet the docking phase requirements, and the load change caused by the phase adjustment is compensated during tension constraint distribution; During the docking process, abnormal conditions are detected. When an interlock signal failure, excessive tension of any cable, or a slack trend is detected, a retreat strategy is executed to return to the approach mode. A slack trend includes any cable tension falling below the pre-tension threshold for more than a preset duration, or a tension decrease rate exceeding a preset threshold. The retreat strategy includes: when any cable tension reaches the rated upper limit threshold, priority is given to redistributing tension and reducing the pull-in speed; when the tension continues to exceed the limit or the interlock fails, the approach mode is returned. Preferably, when a decrease in the pull-in direction control effect or a tendency for control commands to saturate is detected, a softening strategy is executed, including reducing the control demand weight in some directions or increasing the smooth constraint strength of tension distribution.

[0008] Compared with the prior art, the present invention, which adopts the above technical solution, has the following advantages: This invention employs two-stage control during the docking process, clearly defining the roles of macroscopic displacement and fine docking, thus reducing control conflicts and impacts during the docking phase. The laser interlocking transfer of rights solidifies the "permission to enter docking" criterion into a physical interlocking condition, improving safety and operability. The tension-constrained distribution ensures that the three ropes do not slack or overload, reducing off-center loading and suppressing sudden command changes, thereby improving docking stability. The abnormal retreat strategy enhances the system's robustness and recoverability under sea state disturbances and sensor anomalies.

[0009] By superimposing constant tension servo control with virtual damping, the swaying and tension fluctuations caused by sea state disturbances are effectively suppressed, keeping the cable in an effective stress state at all times. By introducing disturbance compensation commands, the impact of periodic inertial disturbances caused by waves on cable tension is further reduced, making the tension curve smoother and the winch operation more continuous. By generating task space control requirements through impedance control or admittance control, the control process has buffering capabilities to reduce impact. Through tension change rate constraints and softening strategies, winch control jitter and impact loads are reduced, maintaining control feasibility and preventing tension from exceeding limits. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a flowchart illustrating the overall workflow of the control method of the present invention. Figure 2 This is a schematic diagram of the control unit's functional modules; Figure 3 A block diagram of the approach phase control strategy; Figure 4 Diagram of the control strategy for the docking phase; Figure 5 This is a schematic diagram of the interlock confirmation and rollback logic; Figure 6 This is a schematic diagram of the layout of the three rope connection points; Figure 7 This is the overall layout diagram of the device structure; Figure 8 This is a partial layout diagram of the device structure.

[0012] In the diagram: 100, main crane; 200, lifting device; 210, active rotating head; 300, wind turbine blade; 310, blade root; 311, upper connection point; 312, lower connection point; 313, side connection point; 400, wind turbine tower; 500, three-winch pull-in execution system; 510, first winch; 520, second winch; 530, third winch; 611, first cable; 612, second cable; 613, third cable; 700, laser interlocking guidance system; 710, laser transmitter; 720, laser receiver target. Detailed Implementation

[0013] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are only some embodiments of the present invention, and not all embodiments; in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0014] Example 1: This example focuses on the pull-in docking of offshore wind turbine blades. (Refer to...) Figure 7 The diagram shows the overall layout of the device structure and Figure 8 The partial layout diagram of the device structure shown depicts three winches installed inside the tower 400, namely the first winch 510, the second winch 520, and the third winch 530. Three cables 611, 612, and 613 are respectively connected to the upper part 311, the lower part 312, and the side connection point 313 at the blade root, forming a multi-directional pulling and attitude constraint capability at the blade root. The layout is as follows... Figure 6 The diagram shows the layout of the three-rope connection points. An active rotary head 210 is installed above the lifting device for blade phase adjustment around the axis; the laser guidance system only outputs an interlock signal indicating successful or failed alignment, used for control mode switching and safety interlocking. The control unit receives signals from the inertial measurement unit, winch encoder, tension sensor, and laser interlock signal, and outputs control commands to the main crane 100, the three winches, and the active rotary head 210.

[0015] Reference Figure 1 The overall workflow diagram of the control method shown indicates that, before the operation begins, the following initialization and calibration steps S1 are performed: First, connection confirmation is performed, ensuring the three cables are reliably connected to the upper part 311, lower part 312, and side connection point 313 of the blade root, respectively. Next, pre-tensioning is performed by slowly tightening the three winches until all three cables reach the preset pre-tension threshold, set at 10% to 15% of the rated working tension, to prevent slack during subsequent operations. Then, signal calibration is performed, calibrating the zero point of the tension sensor and the reference of the winch encoder to ensure the accuracy of tension detection and take-up / delay detection. Next, an interlock self-test is performed, checking whether the laser interlock guidance system outputs a successful or failed alignment signal normally. Finally, a check of the rotating head 210 is executed, performing zero-position and limit checks on the active rotating head to ensure its usability. After these steps are completed, the control unit enters the proximity mode preparation state.

[0016] Reference Figure 2 The control unit functional module diagram shown is as follows: Figure 3 The approach phase control strategy block diagram shown below leads to approach phase control step S2: During the approach phase, the main crane 100 performs macroscopic displacement, moving the blades to the vicinity of the hub docking area. The control unit simultaneously controls three winches to implement an anti-sway control strategy during the approach phase, which includes three parts: constant tension follow-up, virtual damping to suppress sway, and disturbance compensation.

[0017] In constant tension follow-up control, the control unit collects the tension detection signals of the three cables and the winch take-up / release detection signals in real time. Based on a preset target tension range, it adjusts each winch accordingly. The target tension range is set above the pre-tension threshold and below the rated upper limit threshold. The control unit performs closed-loop tension control on each winch to keep the tension of each cable within a controllable range. The tension of any cable is not lower than the preset pre-tension threshold to avoid slack, and does not exceed the preset rated upper limit threshold to avoid overload.

[0018] In virtual damping sway control, to suppress the sway energy caused by waves, wind loads, etc. during the approach phase, the control unit generates a virtual damping sway control quantity based on the sway state information obtained by the inertial measurement unit. This virtual damping sway control quantity is achieved by introducing a suppression term related to the sway speed into the tension closed-loop command. It is used to apply a reverse suppression effect on the sway speed or equivalent sway index, so that the sway energy is gradually dissipated and the sway amplitude is reduced. Under the premise of not violating the safety constraint of constant tension follow-up, the output is superimposed under the condition that the cable tension is not relaxed and does not exceed the limit.

[0019] When sea conditions are complex or the spreader motion disturbances are significant, the control unit activates disturbance compensation control. The disturbance compensation control constructs a disturbance estimate based on the spreader motion state information output by the inertial measurement unit and generates a feedforward compensation quantity to offset the impact of periodic inertial disturbances caused by waves on cable tension, making the cable tension curve smoother and the winch operation more continuous.

[0020] Constant tension follow-up, virtual damping sway suppression, and disturbance compensation are superimposed to generate target tension and target take-up / release commands for each winch, which are then converted into winch drive commands by the actuator closed-loop control module. During the superposition output process, the control unit applies lower limit constraints, upper limit constraints, and rate of change limits to the final command.

[0021] After the blades enter the docking preparation area, the control unit enters the interlock capture step S3 and the mode switching step S4, as described above. Figure 5 The diagram below illustrates the interlock confirmation and rollback logic: The control unit controls the active rotating head 210 to adjust the phase of the blades, gradually aligning the laser emitting end 710 at the blade root with the receiving target 720 inside the hub. The control unit reads the laser interlock signal. To avoid momentary interruptions caused by sea state disturbances, a confirmation condition is used to determine the interlock signal: the alignment success signal must continuously meet a preset confirmation time threshold, such as 2 to 5 seconds, before switching can be triggered. After confirmation, the control unit triggers a mode switch: controlling the main crane to enter follow-up or floating mode, releasing the rigid micro-motion control during the docking phase; simultaneously switching to docking mode, with three winches taking over the docking phase pull-in drive. If the interlock signal is lost or the confirmation condition is not met, the proximity mode is maintained, and phase adjustment and stabilization control continue.

[0022] Reference Figure 4 The control strategy block diagram for the docking phase shown below leads to step S5, which generates control requirements for the docking phase, and step S6, which involves tension constraint allocation and coordinated pull-in. In docking mode, the control unit generates docking control requirements based on the target docking state and the current state. These control requirements are generated by impedance control or admittance control, with docking error and error change rate as inputs. The output is used to drive the bonding control requirements, which characterize the pull-in requirements in the bonding direction, the lateral error reduction requirements, and the attitude stabilization requirements, giving the control process a buffering capability to reduce impact.

[0023] Then, tension is allocated under constraints: Under the following constraints, the control unit allocates the docking control requirements to the target tension and target release / retraction commands of the three winches: the pretension lower limit constraint ensures that the tension of any cable is not lower than the preset pretension threshold; the rated upper limit constraint ensures that the tension of any cable does not exceed the rated threshold; the rate of change limit restricts the change amplitude of tension release / retraction commands in adjacent control cycles, reducing shock and vibration.

[0024] Tension optimization allocation simultaneously satisfies the following objectives: ensuring the effect of the target tension approximates the mission space control requirements; suppressing uneven tension loading of the three cables, reducing the tension difference or variance among the three cables; and suppressing abrupt changes in target tension between adjacent control cycles. When a decrease in control effectiveness or saturation of control commands is detected in the pull-in direction during the docking phase, a softening strategy is implemented, including reducing the weight of control requirements in some directions or increasing the smoothing constraint strength of tension allocation, to maintain control feasibility and prevent tension from exceeding limits.

[0025] During the docking process, the control unit continuously monitors for abnormal conditions and executes the abnormality detection and rollback step S7: If the laser interlock signal fails or continues to fail, the tension of any cable approaches or exceeds the upper limit threshold, any cable shows a slack trend (e.g., tension is below the pre-tension threshold and persists for more than a preset time), or the tension fluctuates abnormally, a retreat strategy is triggered. The retreat strategy includes: reducing the pull-in speed; redistributing tension to reduce the overload on the over-limit rope; and, if necessary, switching back to the approach mode, allowing the main crane to readjust its position and re-enter the interlock capture process.

[0026] Once the blades and hub reach the predetermined fit, the locking and handover step S8 is executed: the control unit controls the three winches to enter the brake locking state or maintain the tension locking state, and then the bolts are handed over to the manual tightener; after the tightening is completed, the control is released and the operation is completed.

[0027] This embodiment achieves stable approach, reliable power transfer, and precise pull-in docking with controllable tension under sea state disturbances through the above control process, which improves docking stability and safety, reduces impact, and minimizes the risks of slack and overload.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades, applied to a pull-in docking system in which three winches are installed inside the tower or hub, three cables are respectively connected to the upper, lower, and side connection points of the blade root, and the cables can only withstand tensile force, characterized in that... Includes the following steps: S1: Pre-tension and calibrate the three cables to ensure that the cable tension meets the preset pre-tension threshold; S2: In proximity mode, control the main crane to perform macroscopic displacement, and simultaneously control the three winches to perform constant tension follow-up and superimpose virtual damping to suppress swaying; S3: Obtain the alignment success interlock signal output by the laser interlock guidance system. When the signal continuously meets the preset confirmation time threshold, trigger the switch from proximity mode to docking mode and control the main crane to enter the follow-up or floating mode. S4: In docking mode, the task space control requirements are generated according to the target docking status. Under the conditions of satisfying the pretension lower limit constraint, rated upper limit constraint and tension change rate constraint of the three cables, the target tension and / or target take-up and release amount of the three winches are calculated through tension optimization allocation, and the three winches are driven to work together to pull in and complete the docking. S5: Detect abnormal conditions during docking. When an interlock signal failure, excessive tension of any cable, or a tendency to slack off is detected, execute a reversal strategy to return to the approach mode.

2. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 1, characterized in that, The constant tension follow-up in step S2 is achieved by performing tension closed-loop control on the three winches respectively, and the virtual damping is achieved by introducing a suppression term related to the swing speed in the tension closed-loop command.

3. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 1, characterized in that, Step S2 further includes fusing the output of the inertial measurement unit to generate a disturbance compensation command to counteract the effect of wave-induced inertial disturbance on the tension.

4. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 1, characterized in that, The task space control requirements mentioned in step S4 are generated by impedance control or admittance control. The impedance control or admittance control takes the docking error and the error change rate as input and outputs the control requirements for driving the bonding.

5. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 1, characterized in that, The tension optimization allocation described in step S4 aims to simultaneously satisfy the following objectives: to make the effect produced by the target tension approximate the task space control requirements; to suppress the tension eccentricity of the three cables, thereby reducing the tension difference or variance of the three cables; and to suppress the abrupt change in target tension between adjacent control cycles.

6. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 1, characterized in that, Step S4 further includes controlling the active rotating head to perform phase adjustment actions to meet the docking phase requirements, and compensating for the load changes caused by phase adjustment during tension constraint distribution.

7. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 1, characterized in that, The relaxation trend mentioned in step S5 includes any cable tension being lower than the pre-tension threshold and lasting for more than a preset duration, or the tension decrease rate exceeding a preset threshold.

8. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 1, characterized in that, The backoff strategy described in step S5 includes: when the tension of any cable reaches the rated upper limit threshold, priority is given to redistributing the tension and reducing the pull-in speed; when the limit is continuously exceeded or the interlock fails, the approach mode is returned.

9. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 8, characterized in that, When a decrease in the pull-in direction control effect or a tendency for control commands to saturate is detected, a softening strategy is executed, including reducing the control demand weight in some directions or increasing the smooth constraint strength of tension distribution.

10. The tension constraint distribution control method for a three-rope assisted docking system for offshore wind turbine blades according to claim 1, characterized in that, The pre-tensioning mentioned in step S1 includes ensuring that the tension of each cable is not less than a preset pre-tensioning threshold in order to avoid slack during the approach and docking phases.

Images