Retro-reflective Blade Tip Tower Clearance Measurement
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Solution Overview
Problem
Current tip-tower clearance measurement systems in wind turbines are either inaccurate, expensive, or unreliable for commercial applications, and lack the ability to estimate clearance at the next closest approach position, which is essential for proactive turbine control.
Innovation Solution
A system comprising an indicator-stripe on the blade-tip and an indicator-ring on the tower, captured by a camera inside the nacelle, which calculates the physical separation distance using image processing to provide accurate and low-cost measurements, and a computational unit that estimates tip-tower clearance in advance by building a functional relationship between blade deflection and clearance signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active transmitters (light-emitting, acoustic, radar, or electromagnetic inductance systems) are placed on the tower to measure tip-tower clearance, then measurement capability is provided, but the system becomes expensive and requires maintenance due to lightning strike vulnerability
Solution Approach 1:
The patent uses a passive retro-reflective marker on the blade tip that reflects light back to the camera, creating a measurable optical signal without requiring active transmitters on the tower. This replaces expensive active sensing systems with a simple passive optical reflection approach, reducing system complexity and cost while maintaining measurement capability
Solution Approach 2:
The patent replaces active electromagnetic or acoustic transmitters with a passive optical system using a camera and retro-reflective marker. This substitution eliminates the need for powered transmitters on the tower, making the system immune to lightning strikes and reducing maintenance requirements
2Adaptability or versatility
If multiple sensors are positioned around the circumference of the tower to cover all yaw angles, then complete coverage is achieved, but the system cost and maintenance difficulty increase significantly
Solution Approach 1:
The patent uses a single camera mounted on the tower that can capture blade tip position data for all yaw angles by utilizing the retro-reflective marker's property of reflecting light back to the source. This single sensor performs the function that would otherwise require multiple sensors positioned around the tower circumference, reducing system complexity while maintaining complete coverage
Solution Approach 2:
The patent changes the measurement approach from requiring multiple fixed sensors at different tower positions to using a single sensor that leverages the optical properties of retro-reflection. The retro-reflective marker reflects light back to the camera regardless of the blade's yaw angle, allowing one sensor to capture all necessary data
3Measurement precision
If sensors are placed on the tower above 100 meters to measure clearance, then measurement is possible, but access for installation and maintenance becomes extremely difficult
Solution Approach 1:
The patent places the measurement function on the blade tip through a retro-reflective marker rather than on the tower. The camera remains on the tower but the actual measurement target moves with the blade, allowing installation and maintenance of the marker to occur at blade level where access is easier, while the camera can be positioned at optimal heights
4Object-affected harmful factors
If a passive system at the blade tip is used to avoid lightning strikes, then system reliability improves, but measurement accuracy and robustness decrease
Solution Approach 1:
The patent converts the challenge of using passive systems into an advantage by employing a retro-reflective marker that actively reflects light back to the camera with high intensity. This passive marker provides a strong, measurable signal that improves measurement accuracy while maintaining immunity to lightning strikes, as no electrical components are present on the blade tip
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides robust, accurate, and low-maintenance tip-tower clearance measurements and estimates, enabling proactive control actions to ensure safety and efficiency by being passive, resistant to lightning, and capable of predicting clearance before the closest approach.
Implementation Method 1
an indicator-stripe positioned in the blade-tip section and encircling the blade-tip section, an indicator-ring encircling the tower... the camera or first camera digitally recording the image on the image-plane or first image plane
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
In a wind turbine comprising a tower supporting a nacelle, at least one blade rotationally attached to the nacelle and having a blade-tip section, a system for measuring the separation distance between the tower and the blade-tip-section of the wind turbine, connprising an indicator stripe on the surface of the blade-tip section, an indicator ring encircling the tower, a camera in the nacelle and positioned such that the blade-tip section and the indicator ring are within the camera's field of view when the blade-tip is at its closest approach position to the tower, the camera digitally recording an image of its field of view at this closest approach position, the distance between indicator ring and camera being essentially equal to the distance between the indicator stripe and the camera at this closest approach position, and an image processor and tip-tower clearance calculator unit receiving the digitally recorded image and calculating a physical separation distance between the indicator stripe and the indicator ring using the digitally recorded image information, the physical separation distance being indicative of the blade tip-tower clearance.