Positioning of lifting yoke uptower

Problem to be Solved

Wind turbine blades are commonly handled using lifting yokes. To lift and control a blade safely, the yoke should be attached at a defined position on the blade; this is typically aligned with the blade’s centre of gravity (CoG) in both the spanwise (length) and edgewise directions.

When a blade is on the ground, it is usually in a known, fixed orientation and the correct yoke interface location can be determined relatively easily. Uptower, the blade orientation and spatial reference are more complex (e.g., due to pitch, rotor azimuth, coning and turbine geometry), and determining the correct attachment position becomes challenging. Camera-equipped yokes may still be insufficient to accurately identify the correct interface position. As a result, operators may need manual measurements and iterative adjustments, creating inefficiency and a higher risk of yoke mispositioning.

The aim is to de-risk the potential mispositioning of the lifting yoke and reduce reliance on manual measurement and human judgement.

Ørsted’s Concept
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Ørsted’s concept is to use accurate positioning (e.g., GPS/GNSS optionally combined with inertial sensors) together with known turbine and blade geometry/configuration data to compute and verify the correct yoke position in real time.

In an example implementation:

• A positioning tracker is secured to the lifting yoke, and outputs the yoke’s real-time position in space as coordinates (x, y, z). The tracker may be GPS, GNSS, GNSS with RTK corrections, or GPS/GNSS combined with a gyro/accelerometer (IMU).
• A controller (or software tool) is provided with input parameters defining the turbine configuration and coordinate reference, such as: turbine variant, tower height, rotor azimuth, coning angle, blade pitch angle and/or the blade CoG location.
• Using these inputs, the controller calculates the theoretical 3D coordinate of the blade attachment target (e.g., blade CoG) for the current rotor/blade state.
• The yoke is brought towards the blade using visual means (e.g., camera guidance), and then fine positioning is completed by comparing the yoke reference coordinate (e.g., “yoke CoG” or another defined point on the yoke) with the calculated blade target coordinate.
• When the coordinate mismatch falls within an allowable tolerance, the system indicates correct positioning and the blade can be secured.

This concept provides a simpler and more accurate method than alternative approaches that may be more complex, less accurate and therefore associated with higher risk.

This idea has been developed by Peter Fynbo and Michael Kastrup.

Advantages of the Solution

• Reduces risk by providing an objective, coordinate-based verification of yoke placement uptower.
• Reduces or removes the need for manual measurements, improving process efficiency.
• Enables repeatable positioning across different blade types and turbine variants by parameterising the calculation.
• Supports different sensor stacks (GNSS, RTK GNSS, GNSS+IMU), allowing accuracy to be matched to operational needs.

Example System

A system for positioning a lifting yoke relative to a wind turbine blade uptower, comprising:

a positioning device mounted on the lifting yoke configured to determine a real-time position of the lifting yoke;

a data interface configured to obtain turbine geometry and configuration data; and

a controller configured to calculate a target position for the lifting yoke corresponding to a predefined blade attachment location and to provide an output indicating whether the real-time position satisfies a tolerance relative to the target position.

The positioning device may comprise a GNSS receiver configured to use differential corrections and/or RTK to improve positional accuracy, optionally combined with an inertial measurement unit to provide orientation information.

The controller may determine the target position as a function of one or more of rotor azimuth, blade pitch angle, coning angle, tower height, turbine variant and blade centre-of-gravity data, and may update the target position during the operation.

The ideas and concepts are published in an effort to show them to all interested companies that may be able to build on Ørsted’s efforts, to create implementable solutions. We welcome an open dialogue with these companies.

Jonathan Foster
Lead IP Specialist