Wind Turbine Blade Stress Sensing Using Radar Backscatter
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Solution Overview
Problem
Conventional methods for measuring stress and load in wind turbine blades are not reliable and fast enough, failing to accurately keep these within acceptable limits during operation.
Innovation Solution
A method using radar equipment to emit and receive signals, analyzing the secondary radar signal to derive stress-related quantities such as blade acceleration and its temporal derivatives, allowing for continuous measurement and control of wind turbine operations to maintain acceptable load and stress levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods (strain gauges, radar units) are used to measure stress and load, then measurement capability is provided, but reliability and speed of measurement are insufficient
Solution Approach 1:
The patent replaces conventional mechanical measurement systems (strain gauges mounted on the blade) with a radar-based electromagnetic measurement system. The radar unit transmits signals that interact with the blade, and the backscattered signals are analyzed to derive stress-related quantities, eliminating the need for physical contact sensors and improving both reliability and measurement speed.
Solution Approach 2:
The patent introduces radar signals as an intermediary medium to measure blade stress indirectly. Instead of directly measuring strain with gauges, the system uses electromagnetic waves that interact with the blade structure, and the changes in backscattered signal characteristics (phase, frequency, time delay) serve as intermediaries to infer stress-related quantities with higher reliability.
2Reliability
If conventional measurement methods are used, then basic stress detection is possible, but response speed is too slow for real-time control
Solution Approach 1:
The radar-based system replaces slow mechanical strain gauge measurements with rapid electromagnetic signal interactions. The radar can continuously transmit and receive signals at high frequencies, enabling real-time detection of blade stress changes without the mechanical response limitations of conventional sensors.
Solution Approach 2:
The radar unit operates by periodically transmitting pulses or continuous waves and receiving backscattered signals at high repetition rates. This periodic measurement approach enables continuous, high-speed monitoring of blade stress with temporal resolution sufficient for real-time control applications.
3Measurement precision
If strain gauges are used to measure blade deflection, then stress information is obtained, but the system complexity and installation requirements increase
Solution Approach 1:
The patent extracts the measurement function from the blade structure itself by using radar signals that interact with the blade without requiring embedded sensors. The blade's natural backscattering of radar signals is utilized, eliminating the need to install, wire, and maintain complex strain gauge systems while preserving measurement capability.
Solution Approach 2:
The radar unit serves multiple functions: it measures blade position, velocity, acceleration, and stress-related quantities using the same electromagnetic signal interaction. This multi-functionality reduces overall system complexity compared to specialized sensors for each measurement type.
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
Enables accurate, reliable, and rapid determination of stress and load on wind turbine blades, improving performance and extending component lifetime by controlling yawing, pitching, and generator torque based on derived stress values.
Implementation Method 1
emitting a primary radar signal towards a portion of the blade; receiving a secondary radar signal emanating from the blade due to interaction with the primary radar signal
Implementation Method 2
receiving a secondary radar signal emanating from the blade due to interaction with the primary radar signal
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
It is described a method of determining a value (12) of a stress related quantity of a rotor blade (3) of a wind turbine (1), the method comprising: emitting a primary radar signal (9) towards a portion (21, 22) of the blade (3); receiving a secondary radar signal (10) emanating from the blade (3) due to interaction with the primary radar signal (9); analysing at least the received secondary radar signal (10); and deriving, based on the analysis, the value (12) of the stress related quantity as related to or indicating a blade acceleration and/or a first temporal derivative of the blade acceleration and/or a higher temporal derivative of the blade acceleration.