Wind Turbine Blade Fatigue Testing With Automatic Actuator Decoupling
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Solution Overview
Problem
Existing fatigue testing methods for wind turbine blades face inefficiencies due to the influence of actuator inertia and gearbox dynamics, especially when excitation is close to the blade root, leading to off-resonance excitation and increased strain on the exciter, which can be costly and require suboptimal placement.
Innovation Solution
A test arrangement that decouples the actuator from the wind turbine blade during movement reversals, using a coupling device with a wheel and contact element to automatically disengage and reengage based on deflection thresholds or controlled by a sensor, allowing efficient excitation closer to the blade root without requiring high power or large exciters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a push rod coupled to a motor via a gearbox is used to achieve limited stroke depth, then the stroke length is controlled, but the inertia of the motor and gearbox strongly influences the oscillation and affects the eigenfrequency of the blade
Solution Approach 1:
The patent extracts the disturbing inertial elements (motor and gearbox) from the oscillation system by using a hydraulic actuator that can be decoupled from the blade during oscillation. The hydraulic actuator provides stroke control without continuously coupling the high-inertia motor-gearbox assembly to the blade, thereby eliminating the strong inertial influence on eigenfrequency determination.
Solution Approach 2:
The patent introduces a hydraulic actuator as an intermediary between the motor and the blade. This intermediary allows stroke control to be achieved while decoupling the high-inertia motor-gearbox from direct connection to the blade during oscillation, thus preventing the inertia from strongly influencing the oscillation and eigenfrequency measurement.
2Ease of operation
If the motor and gearbox are reversed periodically to achieve bidirectional excitation, then the stroke direction is controlled, but the reversal causes relatively high strain on the motor and gearbox
Solution Approach 1:
The patent replaces the mechanical reversal system (motor and gearbox reversing directions) with a hydraulic actuation system. The hydraulic actuator can change force direction by controlling fluid flow direction, eliminating the need for mechanical reversal of high-inertia components and thereby reducing strain on the motor and gearbox.
Solution Approach 2:
The hydraulic actuator serves as an intermediary that mediates between the motor and the blade, allowing bidirectional excitation without requiring the motor and gearbox to reverse direction. The hydraulic system absorbs the directional changes, protecting the motor-gearbox from high strain during reversals.
3Reliability
If the exciter is placed further away from the blade root to reduce strain, then the motor and gearbox are protected, but the excitation efficiency decreases due to off-resonance conditions
Solution Approach 1:
The hydraulic actuator acts as an intermediary that enables close placement of the exciter to the blade root while protecting the motor-gearbox from excessive strain. The hydraulic system can deliver high forces near the root without requiring the motor and gearbox to operate under high strain conditions, thus maintaining excitation efficiency while protecting the drive components.
Solution Approach 2:
The patent employs a dynamic coupling approach where the hydraulic actuator can be engaged and disengaged during oscillation cycles. This dynamic operation allows the exciter to be placed close to the root for efficient excitation while the hydraulic system manages the strain on the motor-gearbox through controlled engagement and decoupling.
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
This approach minimizes the impact of actuator inertia on eigenfrequency, reduces strain on the exciter, and allows for efficient fatigue testing with reduced costs by enabling excitation closer to the blade root, improving testing accuracy and efficiency.
Implementation Method 1
minimizes the impact of actuator inertia on eigenfrequency
Implementation Method 2
allowing the actuator to exert a force in at least one direction on the second section... excite oscillations of the blade... off-resonance excitation
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Test arrangement for fatigue testing a wind turbine blade (2), wherein a first section (3) of the wind turbine blade (2) is attached to a fixing device (4) and wherein a second section (5) of the wind turbine blade (2) is attached to an excitation device (6), wherein the excitation device (6) comprises an actuator (7) and a coupling device (8) that couples the second section (5) to the actuator (7) in an engaged state (9), allowing the actuator (7) to exert a force in at least one direction on the second section (5), wherein the coupling device (8) is designed to automatically disengage, therefore decoupling the actuator (7) from the second section (5), when a disengagement condition is met, and to automatically return to the engaged state (9), when an engagement condition is met during the operation of the excitation device (6).