Rotor Blade Condition Monitoring via Guided Elastic Waves
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Solution Overview
Problem
Current condition monitoring methods for wind turbine rotor blades are limited by the lack of reference spectra for certain faults, leading to inaccurate fault localization and complex evaluation processes, especially for cracks and delaminations that can occur in various positions and dimensions.
Innovation Solution
A model-based method using a sensor and actuator network to detect natural vibrations and guided elastic waves, with acoustic signature analysis and finite element modeling to determine structural damage and localize faults with high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If natural frequency spectra are detected and compared with reference spectra, then condition monitoring can be performed, but fault localization is limited and evaluation becomes very complex when no reference spectrum is available
Solution Approach 1:
The patent changes the monitoring parameters from global natural frequency spectra to local guided elastic waves with specific frequency ranges. By using waves confined to specific frequency ranges that propagate along defined paths, the system can localize faults precisely without requiring comprehensive reference spectra for all possible fault conditions. The evaluation complexity is reduced by focusing on localized wave behavior rather than global spectral comparison.
Solution Approach 2:
The patent segments the rotor blade into multiple monitoring zones with sensors distributed throughout. Each sensor monitors local conditions independently, allowing fault localization to specific segments rather than requiring global spectral analysis. This segmentation enables precise fault positioning and simplifies evaluation by isolating problems to specific blade regions.
2Reliability
If reference spectra are used for fault detection, then existing faults can be identified, but new or unknown fault types cannot be detected
Solution Approach 1:
The system uses the rotor blade's own structure to guide and detect elastic waves. By analyzing changes in wave propagation characteristics through the blade structure itself, the system can detect both known and unknown fault types without relying on pre-defined reference spectra. The blade structure serves as both the monitored object and the detection medium, enabling universal fault detection across all fault types.
3Measurement precision
If manual condition monitoring is performed at periodic intervals, then inspection can be carried out, but the effort and time required are very high
Solution Approach 1:
The patent implements continuous automated monitoring using distributed sensors that permanently detect guided elastic waves and natural vibrations. This eliminates the need for periodic manual inspections while maintaining high measurement precision. The continuous monitoring provides real-time condition assessment, immediately detecting faults as they occur without time delays associated with scheduled manual inspections.
4Measurement precision
If sensors are distributed throughout the rotor blade, then fault localization precision is improved, but the device complexity and cost increase
Solution Approach 1:
The patent employs sensors that perform multiple functions: detecting guided elastic waves for fault localization, measuring natural vibrations for structural health assessment, and monitoring various frequency ranges simultaneously. This multi-functionality reduces the need for separate specialized sensors, thereby limiting the increase in device complexity while maintaining high fault localization precision through distributed sensing.
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 precise localization and description of faults on rotor blades, improving the accuracy of condition monitoring and enabling timely maintenance decisions by comparing measurement signals with reference models and updating finite element simulations to reflect damage.
Implementation Method 1
a sensor and actuator network attached to a rotor blade or a network arrangement of ultrasonic transducers permanently detect natural rotor blade vibrations occurring globally on the rotor blade and locally guided elastic waves
Implementation Method 2
natural rotor blade vibrations occurring globally on the rotor blade and locally guided elastic waves
Implementation Method 3
An acoustic signature analysis is carried out with one or more sensor(s) or ultrasonic transducer(s)
Data Source
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AI summary
The invention relates to a method for monitoring the condition of rotor blades for wind turbines. It is therefore the object of the invention to increase the accuracy of the monitoring of the condition of rotor blades of wind turbines and to allow a localization of faults or defects and their exact description. In the method in accordance with the invention, eigenvibrations of a rotor blade occurring globally at the rotor blade and locally guided elastic waves are permanently detected with time and spatial resolution using a sensor network and actuator network attached to the rotor blade or using a network arrangement of ultrasound transducers. In addition, elastic waves which are guided periodically at predefinable time intervals and which are respectively emitted by an actuator or ultrasound transducer and detected by sensors or ultrasound transducers are in so doing inspected for variations of the emitted waves.