Fatigue testing device for wind turbine blade testing, a method of testing wind turbine blades and a control system for a blade testing actuator
First Claim
Patent Images
1. A fatigue testing device for wind turbine blade testing, the device comprising:
- an actuator configured to deflect the blade at an excitation frequency, a first sensor configured to sense an input force to the blade from the actuator, a second sensor configured to sense an amplitude of deflection of the blade due to the actuator, and a control system in communication with the actuator and the first and second sensors, the control system including a controller,the control system configured to monitor the amplitude of the blade as sensed by the second sensor, to find an initial natural frequency of the blade based on the amplitude of the blade sensed by the second sensor, and to set the excitation frequency of the actuator to the initial natural frequency,the control system further including a frequency modulation algorithm and being further configured to modulate the excitation frequency so that the excitation frequency is repeatedly swept forwards above and backwards below the initial natural frequency, andthe control system being configured to find a subsequent natural frequency to set the excitation frequency to by, during modulation of the excitation frequency, monitoring blade amplitude via the second sensor and the input force of the actuator necessary to produce a desired blade amplitude via the first sensor, and if the necessary input force decreases during forward sweeping of the excitation frequency, to continue forward sweeping of the excitation frequency, and if the necessary input force increases during forward sweeping of the excitation frequency, to cause backward sweeping of the excitation frequency.
1 Assignment
0 Petitions
Accused Products
Abstract
The invention provides a fatigue exciter for wind turbine blades. Wind turbine blades require excitation at or near their natural frequency to induce bending moments that simulate in service loadings and must be easily controllable and with the minimum of unnecessary added mass or force. The invention provides a device and a method by which force controlled feedback is used for finding an optimal excitation frequency. This force could be provided e.g. by a digital signal generator.
28 Citations
23 Claims
-
1. A fatigue testing device for wind turbine blade testing, the device comprising:
-
an actuator configured to deflect the blade at an excitation frequency, a first sensor configured to sense an input force to the blade from the actuator, a second sensor configured to sense an amplitude of deflection of the blade due to the actuator, and a control system in communication with the actuator and the first and second sensors, the control system including a controller, the control system configured to monitor the amplitude of the blade as sensed by the second sensor, to find an initial natural frequency of the blade based on the amplitude of the blade sensed by the second sensor, and to set the excitation frequency of the actuator to the initial natural frequency, the control system further including a frequency modulation algorithm and being further configured to modulate the excitation frequency so that the excitation frequency is repeatedly swept forwards above and backwards below the initial natural frequency, and the control system being configured to find a subsequent natural frequency to set the excitation frequency to by, during modulation of the excitation frequency, monitoring blade amplitude via the second sensor and the input force of the actuator necessary to produce a desired blade amplitude via the first sensor, and if the necessary input force decreases during forward sweeping of the excitation frequency, to continue forward sweeping of the excitation frequency, and if the necessary input force increases during forward sweeping of the excitation frequency, to cause backward sweeping of the excitation frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
-
-
18. A fatigue testing device for wind turbine blade testing, the device comprising an actuator configured to deflect the blade at an excitation frequency, a first sensor configured to sense an input force to the blade from the actuator, a second sensor configured to sense an amplitude of deflection of the blade due to the actuator, and a control system in communication with the actuator and the first and second sensors, the control system including a controller,
the control system configured to monitor the amplitude of the blade as sensed by the second sensor, to find a natural frequency of the blade based on the amplitude of the blade as sensed by the second sensor, and to set the excitation frequency of the actuator to the natural frequency, wherein the control system further includes a frequency modulation algorithm and is further configured to find the natural frequency by modulation of the excitation frequency, the control system being further configured, during modulation of the excitation frequency, to provide an input signal significant of an increase or decrease of the input force necessary to deflect the blade and to provide an output signal significant of the amplitude of the deflection, wherein the control system is further configured to select a subsequent excitation frequency based on a ratio between the input force and the amplitude, the input signal, or the output signal, wherein the selection facilitates a minimal ratio between the input force and the amplitude.
-
19. A method of testing a wind turbine blade, the blade having a hub end and a tip end, the method comprising the steps of:
-
fixating the blade to a bench, providing an input force for an actuator to apply, at an excitation frequency, a cyclic load to the blade at a location at a distance from the hub end, modulating the excitation frequency so that the excitation frequency is repeatedly swept forwards above and backwards below an initial natural frequency of the blade, determining an amplitude of movement of the blade, modulating the input force during modulation of the excitation frequency to maintain a desired blade amplitude, and selecting a subsequent excitation frequency based on a ratio between the input force and the amplitude, wherein the step of selecting the subsequent excitation frequency further comprises monitoring the blade amplitude and the input force of the actuator necessary to produce the desired blade amplitude, and if the necessary input force decreases during forward sweeping of the excitation frequency, to continue forward sweeping of the excitation frequency, and if the necessary input force increases during forward sweeping of the excitation frequency, to cause backward sweeping of the excitation frequency. - View Dependent Claims (20, 21)
-
- 22. A control system for controlling a testing device for a wind turbine blade, the testing device comprising an actuator configured to deflect the blade at an excitation frequency, a first sensor configured to sense an input force to the blade from the actuator, and a second sensor configured to sense an amplitude of deflection of the blade due to the actuator, the control system being in communication with the actuator and the first and second sensors and including a controller, and being configured to monitor the amplitude of the blade as sensed by the second sensor, to find an initial natural frequency of the blade based on the amplitude of the blade as sensed by the second sensor, and to set the excitation frequency of the actuator to the initial natural frequency, the control system further including a frequency modulation algorithm and being further configured to modulate the excitation frequency so that the excitation frequency is repeatedly swept forwards above and backwards below the initial natural frequency of the blade, to determine the amplitude of the blade via the second sensor, to modulate the input force during modulation of the excitation frequency to maintain a desired blade amplitude, and to select a subsequent excitation frequency based on a ratio between the input force and the amplitude, wherein the control system being configured to select the subsequent excitation frequency further comprises the control system being configured to monitor the blade amplitude via the second sensor and the input force of the actuator necessary to produce the desired blade amplitude via the first sensor, and if the necessary input force decreases during forward sweeping of the excitation frequency, to cause continued forward sweeping of the excitation frequency, and if the necessary input force increases during forward sweeping of the excitation frequency, to cause backward sweeping of the excitation frequency.
Specification