Rotor Blade Oscillation Measurement via Spectral Power Density
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Solution Overview
Problem
Existing methods for evaluating oscillation signals on rotor blades of wind power installations require shutdown of the system and use large, heavy devices, limiting their applicability during operation and failing to detect energy-absorbing states.
Innovation Solution
A method that evaluates spectral power density instead of Fourier transform, allowing for the detection of energy-absorbing states and enabling analysis of rotor blade loading and damage during operation using oscillation sensors connected to evaluation electronics within the hub, which can process stochastic harmonic and transient signals to form a power density spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fourier transform is used to evaluate oscillation signals, then the method is simple and widely known, but it cannot detect energy-absorbing states of the rotor blades
Solution Approach 1:
The patent changes the evaluation parameter from Fourier transform (amplitude spectrum) to spectral power density (power spectrum). This parameter change enables the detection of energy-absorbing states in addition to excited oscillations, as the power spectrum captures both the magnitude and energy distribution characteristics of the oscillation signals across different frequency components.
2Reliability
If large and heavy devices are used for excitation of oscillations, then the oscillation measurement can be performed, but the devices are too heavy and complex to be applied during operation
Solution Approach 1:
The patent applies the self-service principle by utilizing the wind itself as the excitation source. The wind-induced oscillations of the rotor blades are directly measured and evaluated through spectral power density analysis, eliminating the need for external heavy excitation devices. The system serves itself by using the natural operating environment (wind) to generate the necessary oscillation signals for measurement.
3Device complexity
If smaller devices are used for excitation, then the device size is reduced, but the wind power installation must be shut down for measurement
Solution Approach 1:
The system uses the natural wind-induced oscillations during normal operation as the excitation source, requiring no additional devices and no shutdown of the wind power installation. The measurement is performed self-service during operational conditions, maintaining productivity while reducing device complexity to minimal sensors and evaluation electronics.
4Measurement precision
If oscillation sensors are located on the balance machine bearings, then unbalance measurement is possible, but the measurement cannot be performed during operation of the rotor blade
Solution Approach 1:
The patent replaces the mechanical balance machine system with a field-based measurement approach. Instead of using physical contact sensors on bearings in a controlled balance machine, the system uses oscillation sensors mounted on the rotor blade itself to detect wind-induced oscillations during operational state, substituting mechanical measurement infrastructure with direct field measurement.
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 more reliable analysis of rotor blade loading and damage detection, including energy-absorbing states not visible in Fourier spectra, allowing for real-time monitoring and comparison of rotor blades, and informing control adjustments.
Implementation Method 1
an oscillation sensor (12) is mounted in the rotor blade (11) in the vicinity of a flange (10) for connection of the blade (11) to a hub (19)
Implementation Method 2
The acceleration sensors generate an electrical signal which reproduces the oscillation state of a rotor blade
Implementation Method 3
A Fourier transform is named as the sole example for computing the spectra
Implementation Method 4
the spectral power density is recorded
Data Source
AI summary
Method for spectral evaluation of oscillation signals which have been obtained on a rotor blade of a wind power installation with an accelerations sensor. In doing so, instead of the otherwise conventional Fourier transform calculation, the spectral power density is computed. In the evaluation, also signal portions are considered which are not detected in the Fourier transform because they do not go back to oscillations which have been excited in the rotor blade.