METHOD AND SYSTEM FOR DETERMINING DAMAGE TO AT LEAST ONE ROTOR BLADE

Abstract

The invention relates to a method and a system (100) as well as a computer program for determining damage to at least one component (34), comprising Measuring a time course of a surface temperature (50) and of natural environmental boundary conditions of the component (34) by selectively changing an interaction of the at least one component (34) with the natural environmental boundary conditions during the measurement; and / or Measuring the time course of a surface temperature (50) and the natural environmental boundary conditions of the component (34) when a change occurs in the natural environmental boundary conditions acting on the component (34); Determining a time course of a simulated surface temperature (60, 62) with a digital model of the component (34) for different damages of the component (34) simulated on the digital model under the recorded time course of the environmental boundary conditions; Determining the damage to the component (34) by comparing the time course of the measured surface temperature (50) and the surface temperature simulated for the different damages to the component (34) (60, 62).

Description

[0001] The invention relates to a method and a system for determining damage to at least one rotor blade of a wind turbine, a computer program and a data processing device for determining damage to a rotor blade of a wind turbine, and a digital model of a rotor blade of a wind turbine. State of the art

[0002] The share of renewable energies in electricity generation, especially wind turbines, will increase significantly in the coming years. In addition to the planned expansion of existing capacities, existing turbine technology must be reliably maintained to achieve these targets, ensuring the highest possible utilization rate of wind turbines throughout their operating license period.

[0003] Condition monitoring is a common practice in the wind energy sector. All digitally measurable turbine conditions (such as speed, oil condition, vibrations, noise emissions, etc.) are typically recorded, centrally collected, and evaluated. Predictive maintenance based on this data, among other things, leads to fewer turbine failures and reduced personnel deployment.

[0004] Rotor blades typically consist of a glass fiber (GRP) component coated with a gel coat and a paint layer. Damage is often caused by prolonged, heavy loads, manufacturing defects, or various external influences, such as lightning strikes.

[0005] In offshore installations, specific weather conditions and the influence of salty air and water also negatively impact durability. Furthermore, these installations are associated with high inspection and maintenance costs, and inspection or maintenance poses a significant risk to the occupational safety of personnel. Common types of damage to rotor blades include cracks, erosion damage, and internal structural damage. Unlike surface erosion damage, such as paint damage, cracks can occur both internally and on the surface. Internal damage, such as delamination or adhesive delamination, is difficult to detect or quantify even with the naked eye.

[0006] DE 10022568 A1 describes a method for monitoring measurement objects, particularly outdoor measurement objects, by determining measured values ​​relevant to the respective object, particularly in the form of anomaly values, as well as the respective conditions of the measured values, from which a visible and analyzable image is created. Additional localizing and individualizing data and general measured values ​​relating to the respective measurement object are recorded beforehand and / or together with the measured values, thus objectifying them, and / or retrieved from appropriate storage devices and included in the monitoring.

[0007] DE 10 2012 203 455 A1 describes a method for monitoring the surface condition of components whose surface comprises multiple layers, in order to detect external damage of varying severity in a localized manner. The surface of a component is illuminated in sections, using a broad- or narrow-band electromagnetic radiation, using an illumination unit. Electromagnetic radiation reflected from the component is captured by a recording unit and frequency-selectively evaluated by an evaluation unit, so that damage to a layer of the component's surface can be determined based on the frequency-dependent absorption behavior or fluorescence behavior of that layer. Disclosure of the invention

[0008] The object of the invention is to provide an improved method for determining damage to at least one rotor blade of a wind turbine.

[0009] A further object of the invention is to provide an improved system for determining damage to at least one rotor blade of a wind turbine using an improved method.

[0010] A further object of the invention is to provide a computer program for determining damage to a rotor blade of a wind turbine according to an improved method.

[0011] Another object of the invention is to provide a data processing device for an improved system for determining damage to a rotor blade of a wind turbine.

[0012] Another object of the invention is to provide a digital model of a rotor blade of a wind turbine for an improved method.

[0013] The objects are achieved by the features of the independent claims. Advantageous embodiments and advantages of the invention emerge from the further claims, the description, and the drawings.

[0014] According to one aspect of the invention, a method for determining damage to at least one rotor blade of a wind turbine is proposed. The method comprises at least the following steps: A temporal profile of a surface temperature and natural environmental boundary conditions of the rotor blade are measured using a system with at least one aircraft, with a targeted change in the interaction of the at least one rotor blade with the natural environmental boundary conditions during the measurement of the temporal profile of the surface temperature of the component, in particular with a targeted change in an orientation and / or a position and / or a speed of the rotor blade.

[0015] Alternatively or additionally, a temporal progression of a surface temperature and of natural environmental boundary conditions of the rotor blade is measured by means of an airborne system with at least one aircraft, when a change in natural environmental boundary conditions acting on the rotor blade occurs.

[0016] Furthermore, a temporal progression of a simulated surface temperature is determined using a digital model of the rotor blade for various types of damage to the rotor blade simulated on the digital model under the temporal progression of the environmental boundary conditions recorded during the measurement. Furthermore, the damage to the component is determined by comparing the temporal progression of the measured surface temperature with the surface temperature simulated for the various types of damage to the component.

[0017] The method according to the invention exploits the fact that a material heats or cools at different rates depending on its thickness. This is used in transient thermography.

[0018] The method presented here differs from the state of the art in that it actively seeks a natural change in the natural environmental conditions that would cause a change in the surface temperature of the rotor blade. By varying the heating of a wind turbine's rotor blade over time due to the changed environmental conditions, damage to the material can be detected. No complex, artificially induced change, such as heating, is necessary. Nor are random changes in the environmental conditions acting on the rotor blade used; instead, the changes are actively sought, for example, by moving the rotor blade into a different orientation, or by setting it in motion or stopping it.

[0019] A digital model is used to identify damage and provide quantitative information about the extent of the damage. Unlike the current state of the art, this makes it possible to obtain varying spatial resolutions of the measurement object, depending on the positioning of a temperature measuring device using an aircraft, such as a drone. The use of an aircraft, such as a drone, in particular, makes the method suitable for offshore wind farms.

[0020] The digital model can, for example, be a classical mathematical-physical model, e.g., discretized differential equations. Alternatively, data-based digital models can be used, which can be trained using artificial intelligence methods, for example.

[0021] According to the proposed method, the temporal temperature profile of the surface of the rotor blade is determined by flying over it with one or more drones equipped with a temperature measuring device.

[0022] This involves inducing a change in the environmental boundary conditions, and simultaneously determining or estimating the temporal profiles of these environmental boundary conditions at the measurement surface, such as solar radiation, ambient air temperature, wind speed (to determine convection by air flow), sky radiation temperature, and ground radiation temperature. The surface temperature of the rotor blade is thus determined during this actively sought, but natural, excitation by solar radiation or another changing environmental boundary condition, such as ambient air temperature, convection by air flow, sky radiation temperature, and ground radiation temperature.

[0023] Furthermore, simulations of the surface temperature of the rotor blade are carried out using the measured environmental boundary conditions by means of a digital (numerical) model, whereby the digital model shows different damages of the rotor blade and the corresponding real damage of the rotor blade is determined according to the measured temperature change.

[0024] For example, the digital model can include sections of a wind turbine's rotor blade, representing the intact rotor blade and various damage effects, such as delaminations at varying depths, inclusions, web delamination, and cracks. Transient surface temperatures are calculated for these different damage effects under the ambient boundary conditions. Since the rotor blade structure differs in different areas, different configurations can be simulated, within which the damage series exist.

[0025] To compare the temporal progression of the measured surface temperature and the surface temperature simulated for the different types of damage to the rotor blade and to subsequently select the correct digital model with the corresponding damage, either classical methods, such as the RMS deviation between the curves as a measure of agreement, or artificial intelligence (AI) methods are suitable.

[0026] The proposed method can be advantageously used as an inspection technique for wind turbine rotor blades. The structural integrity of the turbines can thus be regularly checked. The described active thermography, particularly on unmanned aerial vehicles such as drones, has the potential to enable reliable, more time- and cost-efficient, and less labor-intensive inspection of wind turbine rotor blades.

[0027] According to a favorable embodiment of the method, the natural environmental boundary conditions may comprise at least one of the following conditions: solar radiation absorbed by the rotor blade, in particular a global inclined solar radiation, ambient air temperature, wind speed, in particular in the vicinity of the rotor blade, radiation temperatures of the sky and / or ground.

[0028] If the interaction of the rotor blade with the natural environmental boundary conditions cannot be specifically changed, or as an additional variation, other changing environmental boundary conditions can also be used, such as changes in the ambient air temperature, changes in natural solar radiation, changes in the flow conditions / relative wind on the rotor blade due to changes in the natural wind speed.

[0029] Advantageously, the environmental boundary conditions, in particular at least the wind speed and / or the ambient air temperature, can be measured in the vicinity of the rotor blade.

[0030] According to a favorable embodiment of the method, the orientation of the rotor blade relative to the sun and / or the wind direction can be specifically changed during the measurement of the rotor blade's surface temperature. In particular, the azimuth angle of the wind turbine and / or the angle of attack of the rotor blade can be changed during the measurement. Alternatively or additionally, the speed of the wind turbine can be changed during the measurement of the rotor blade's surface temperature.

[0031] For example, an actively induced rotation of the rotor blades via an azimuth drive can be used as excitation, for example from a position in which the solar radiation is approximately parallel to the surface sweeping over the rotors to a position in which the solar radiation is approximately perpendicular to the rotor surface, so that more radiation power falls on the rotor blade or vice versa.

[0032] As a further variant, instead of the azimuth angle of the wind turbine, the angle of attack of the rotor blades can be adjusted so that the solar radiation on the areas to be examined changes.

[0033] Another excitation method is to start the wind turbine from a standstill. This changes the convection through airflow. This can also be achieved through azimuth movement. Conversely, the wind turbine can also be brought to a standstill from a rotating state. To do this, the wind turbine can be actively braked or the brake can be released. Furthermore, the angle of attack of the rotor blades can be changed accordingly.

[0034] Combinations of the different excitation types to change the environmental boundary conditions are also possible.

[0035] According to a favorable embodiment of the method, at least one of the following devices can be used to measure the surface temperature: infrared camera, infrared sensor, multispectral camera, or multispectral sensor. This allows the surface temperature to be determined with sufficient spatial and temporal resolution.

[0036] According to a favorable embodiment of the method, the solar absorption coefficient of the rotor blade surface can be determined using a camera in the visible range. In particular, the solar radiation absorbed by the rotor blade material can be determined based on the absorption coefficient. The absorbed solar radiation can thus be estimated with greater accuracy. For example, it can be detected and corrected if the surface's absorption coefficient is increased due to contamination. Advantageously, the solar radiation absorbed by the material can be corrected using images in the visible wavelength range and by correcting the angle of incidence on the material.

[0037] According to a favorable design of the method, the absorbed solar radiation can be calculated by taking into account the angular orientation of the corresponding surface element of the rotor blade relative to the sun. This allows the absorbed solar radiation to be determined with greater accuracy.

[0038] According to a favorable embodiment of the method, the comparison of the temporal course of the measured surface temperature and the surface temperature simulated for the different damages of the rotor blade can be carried out by comparing amplitude responses and / or phase responses of the measured and simulated courses, in particular as a function of a frequency of the temporal courses, in particular by a Fourier transformation.

[0039] The simulation with the digital model provides the simulated surface temperature as a time profile, as well as an amplitude and phase as a function of frequency. This advantageously allows a comparison of the amplitude and / or phase responses of the measured temperature profiles with the simulated temperature profiles of the digital model. This allows the digital model to be assigned to the corresponding damage, so that the difference between the measured and simulated temperature profiles is minimal.

[0040] Advantageously, the evaluation of the temporal characteristics on the measurement object and on the digital model can be carried out by a fast Fourier transformation (FFT) or similar methods and an output of the spatially resolved amplitude and phase responses of the temperature as a function of frequency.

[0041] The amplitude response or phase response is a function of the frequency Ω, the thickness of the material, and the size λ / (ρ*c p ). Here, λ is the thermal conductivity of the material, ρ the density, c p the specific heat capacity. With the two measured quantities (amplitude and phase) two unknown target quantities can be determined, e.g. λ / (ρ*c p ) and the material thickness, i.e. depth of damage in the rotor blade.

[0042] It is advantageous to measure the material properties for the digital model (λ / (ρ*c p )) can be used as a material calibration, even if only the temperature curves are compared and the evaluation is not based on amplitude and phase response. For this purpose, a location on the rotor blade can be used where the thickness is exactly known and no damage is present. This allows (λ / (ρ*c p )) can be determined from only one measured value.

[0043] With a favorable design of the method, the comparison of the temporal progression of the measured surface temperature and the simulated surface temperature for the various types of damage to the rotor blade can be carried out using an artificial intelligence method. Other methods, such as artificial intelligence (AI), can also be advantageously used to determine the digital model with the corresponding damage that provides the most similar simulated temperature progression.

[0044] In more complex KL methods, the temporal progression of the natural environmental boundary conditions acting on the rotor blade section can also be incorporated.

[0045] When it comes to AI methods, a distinction is usually made between supervised learning methods and unsupervised learning methods. An example of an applicable unsupervised learning method is the K-Means clustering method. By using digital models, even large amounts of virtual data can be generated and used to train the AI. This also allows supervised learning methods to be used. Examples include the K-NN method (k nearest neighbors), methods of hierarchical cluster analysis, Bayesian networks (e.g., Naive Bayes classifier), or simpler models such as decision trees or regression analyses. These methods are mentioned only as examples because developments in the AI ​​field are very dynamic.

[0046] Compensation for movements of the rotor blades of a wind turbine at standstill when comparing the temporal course of the measured surface temperature and the surface temperature simulated for the different damages of the rotor blade can be achieved by image processing, for example by detecting spots, edges or the like.

[0047] With a favorable design of the method, the temporal progression of the measured surface temperature and the simulated surface temperature for the various types of damage to the rotor blade can be compared for selected areas of the rotor blade with different material thicknesses. This allows the damage mechanism to be further narrowed down.

[0048] With a favorable design of the method, the comparison of the temporal progression of the measured surface temperature and the surface temperature simulated for the various types of damage to the rotor blade can be performed automatically in an airborne system or in a ground-based facility. Automatic evaluation can advantageously be performed during flight on the drone or offline on the ground, for example, by comparing the preprocessed measurement results with an existing catalog of results from the digital model with different types of damage.

[0049] If the method is designed to be advantageous, several rotor blades can be measured simultaneously using several aircraft.

[0050] Using only one drone and high-resolution spatial images, a zone of the rotor blade can be measured while the drone is stationary or by flying along the rotor blade, so that each zone of the rotor blade is imaged multiple times during the measurement time. Multiple rotor blades can be measured simultaneously with multiple drones. The measured thermograms and visual photo sections can be combined, for example, using knowledge of the camera orientation from SLAM algorithms (SLAM = Simultaneous Localization and Mapping) or photogrammetry.

[0051] According to a further aspect of the invention, a system is proposed for determining damage to at least one rotor blade of a wind turbine using the described method, at least comprising a temperature measuring device for measuring a surface temperature of the rotor blade, devices for measuring natural environmental boundary conditions of the rotor blade, and an evaluation device for carrying out a comparison of a time profile of a measured surface temperature of the rotor blade and a surface temperature simulated for the different damages of the rotor blade.

[0052] The proposed system is designed to determine the surface temperature of the rotor blade as well as the natural environmental conditions of the rotor blade as a function of time and to compare the measured temperature profiles with simulated temperature profiles calculated under the assumption of different levels of damage to the rotor blade. The comparison of the measured and simulated temperature profiles then allows conclusions to be drawn about the damage present in the rotor blade.

[0053] The system can be used advantageously as an inspection technology for wind turbine rotor blades. The structural integrity of the turbines can thus be regularly checked. The described active thermography, particularly on unmanned aerial vehicles such as drones, has the potential to enable reliable, more time- and cost-efficient, and less labor-intensive inspection of wind turbine rotor blades.

[0054] According to a favorable design of the system, the natural environmental boundary conditions may include at least one of the following conditions: solar radiation absorbed by the rotor blade, in particular a global inclined solar radiation, ambient air temperature, wind speed, in particular in the vicinity of the rotor blade, radiation temperatures of the sky and / or ground.

[0055] If the interaction of the rotor blade with the natural environmental boundary conditions cannot be specifically changed, or as an additional variation, other changing environmental boundary conditions can also be used, such as changes in the ambient air temperature, changes in natural solar radiation, changes in the flow conditions / relative wind on the rotor blade due to changes in the natural wind speed.

[0056] Advantageously, the environmental boundary conditions, in particular at least the wind speed and / or the ambient air temperature, can be measured in the vicinity of the rotor blade.

[0057] According to a favorable embodiment of the system, the temperature measuring device and the devices for measuring the natural environmental conditions can be arranged at least partially on an aircraft, in particular an unmanned aircraft. In particular, a device for measuring wind speed can be arranged on the aircraft. The air temperature or the solar radiation temperature can also advantageously be measured on the aircraft. By determining at least some of the environmental conditions directly on the aircraft in the vicinity of the rotor blade, greater accuracy in determining damage to the rotor blade can advantageously be achieved.

[0058] According to a favorable system design, the temperature measuring device can comprise at least one of the following devices: infrared camera, infrared sensor, multispectral camera, or multispectral sensor. This allows the surface temperature to be determined with sufficient spatial and temporal resolution.

[0059] According to a favorable embodiment, the system can include a visual camera for detecting the angular orientation of a corresponding surface element of the rotor blade relative to the sun. This allows the angular orientation of the corresponding surface element of the rotor blade relative to the sun to be taken into account when calculating the absorbed solar radiation. In this way, the absorbed solar radiation can be determined with greater accuracy.

[0060] According to a favorable embodiment, the system can further comprise a ground-based facility with devices for measuring natural environmental conditions and / or the evaluation device. Environmental conditions such as radiation temperatures of the sky and / or ground can advantageously be determined on the ground. Solar radiation and air temperature can be determined, for example, on the ground or in the aircraft.

[0061] An automatic evaluation can advantageously be carried out offline on the ground in the evaluation facility, for example by comparing the pre-processed measurement results with an existing catalogue of results from the digital model with different damages.

[0062] In a favorable system design, the evaluation device can be located on the aircraft. Automatic evaluation can advantageously be performed on the aircraft in the evaluation device, for example, by comparing the preprocessed measurement results with an existing catalog of results from the digital model with different damage levels.

[0063] According to a favorable design, the system can further comprise several aircraft for the simultaneous measurement of several rotor blades.

[0064] Using only one drone and high-resolution spatial images, a zone of the rotor blade can be measured while the drone is stationary or by flying along the rotor blade, ensuring that each zone of the rotor blade is imaged multiple times during the measurement period. Multiple rotor blades can be measured simultaneously using multiple drones.

[0065] According to a further aspect of the invention, a computer program for determining damage to a rotor blade of a wind turbine is proposed, comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the described method.

[0066] The computer program can advantageously be used to control the acquisition of measured data such as surface temperatures and / or environmental conditions, as well as for simulation with the digital model and evaluation of the measured and simulated temperature profiles. Furthermore, the computer program can also be used to control an aircraft during a flight along the rotor blade to record the surface temperature.

[0067] According to a further aspect of the invention, a data processing device for a system for determining damage to a rotor blade of a wind turbine is proposed, comprising at least a measurement data acquisition unit for acquiring measurement data from a temperature measuring device, as well as devices for measuring natural environmental boundary conditions and an evaluation device with at least one computer.

[0068] The system can advantageously comprise an aircraft, in particular an unmanned aircraft such as a drone. The data processing device can be organized as a single unit or distributed. The measurement data acquisition unit for recording surface temperatures as well as at least some of the environmental boundary conditions can be arranged on the aircraft. A further part of the environmental boundary conditions can also be recorded at a ground station if necessary. The evaluation device can also be arranged on the aircraft or in the ground station. The aircraft and ground station can advantageously have wireless communication devices and exchange data via them.

[0069] According to a further aspect of the invention, a digital model of a rotor blade of a wind turbine is proposed, which is used in the described method.

[0070] The digital model can include an image of the rotor blade or at least parts of it. The digital model can be modeled as an intact rotor blade or with various types of damage.

[0071] The digital model can, for example, be a classical mathematical-physical model, e.g. discretized differential equations.

[0072] For use with artificial intelligence methods for the comparison of measured and simulated temperature profiles, an alternative approach is to use a data-based digital model, which can be trained using measurement data from preliminary tests to enable rapid identification of damage in the rotor blade with high accuracy. drawing

[0073] Further advantages will become apparent from the following description of the drawings. The figures illustrate exemplary embodiments of the invention. The figures, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0074] Examples include: Fig. 1 is a schematic representation of a system for determining damage to at least one rotor blade of a wind turbine according to an embodiment of the invention; Fig. 2 a schematic representation of a wind turbine; Fig. 3 a cross-section through a rotor blade of a wind turbine with marked measuring areas; Fig. 4 a digital model of a measuring area of ​​the rotor blade; Fig. 5 a digital model of a first measuring area without damage; Fig. 6 the digital model of the first measuring area with a surface damage; Fig. 7 the digital model of the first measuring area with a delamination in the outer area; Fig. 8 the digital model of the first measuring area with a delamination in the inner area; Fig. 9 a digital model of a second measuring area without damage; Fig. 10 the digital model of the second measuring area with a surface damage; Fig. 11 the digital model of the second measuring area with a delamination in the outer area; Fig. 12 the digital model of the second measuring area with a delamination in the inner area; and Fig. 13 a comparison of time courses of a measured surface temperature and of two simulated surface temperatures on a rotor blade according to the method according to the invention. Embodiments of the invention

[0075] In the figures, components of the same type or function similarly are designated by the same reference numerals. The figures are merely examples and are not to be construed as limiting.

[0076] Before describing the invention in detail, it should be noted that it is not limited to the specific components of the device, as these components may vary. The terms used herein are intended solely to describe particular embodiments and are not intended to be limiting. Furthermore, when the singular or indefinite articles are used in the description or claims, this also refers to the plural of these elements, unless the overall context clearly indicates otherwise.

[0077] The directional terminology used below, including terms such as "left," "right," "top," "bottom," "before," "behind," "after," and the like, is intended solely to enhance understanding of the figures and is in no way intended to limit the scope of the invention. The components and elements depicted, as well as their design and use, may vary according to the considerations of a person skilled in the art and may be adapted to specific applications.

[0078] Fig. 1 shows a schematic representation of a system 100 for determining damage to at least one component 34 in the form of a rotor blade 32 of a wind turbine 30 according to an embodiment of the invention.

[0079] Using a drone as an unmanned aerial vehicle (UAV) 12 with a built-in infrared camera 14, the temporal change in the surface temperature 50 of a rotor blade 32 is recorded. Likewise, the temporal profiles of the environmental boundary conditions, such as solar radiation, ambient air temperature, wind speed to determine convection by air flow, sky radiation temperature, and ground radiation temperature, are recorded.

[0080] The system 100 comprises the unmanned aerial vehicle 12 in the form of a drone with a temperature measuring device 14 for measuring the surface temperature 50 of the rotor blade 32 as the component 34 to be examined in the form of a rotor blade 32, as well as a device 16 for measuring a wind speed. The system further comprises devices 18 for measuring natural environmental boundary conditions of the rotor blade 32 and a ground-based device 22 with an evaluation device 20.

[0081] The devices 18 for measuring the natural environmental boundary conditions can be electrically coupled to the ground-based device 22 in order to make the data available to the evaluation device 20.

[0082] In an alternative embodiment, the evaluation device 20 can also be arranged in the aircraft 10 itself.

[0083] Aircraft 10 and ground station 22 may conveniently have wireless communication facilities and exchange data via them.

[0084] For this purpose, the system 100 can have a data processing device which comprises at least one measurement data acquisition unit for acquiring measurement data from the temperature measuring device 14, as well as the devices 16, 18 for measuring natural environmental boundary conditions and the evaluation device 20 with at least one computer.

[0085] In Fig. Figure 2 schematically shows a wind turbine 30 with three rotor blades 32. The wind turbine 30 can be adjusted around a vertical axis with an azimuth angle 70 to align it according to a wind direction. An angle of attack 72 of the rotor blades 32 around the longitudinal axes of the rotor blades 32 can also be adjusted to accelerate or decelerate the rotation speed.

[0086] With the Fig. The system 100 shown in FIG. 1 can be used to determine damage to at least one rotor blade 32 of a wind turbine 30. This method records a temporal profile of natural environmental boundary conditions of the rotor blade 32 and measures a temporal profile of a surface temperature 50 of the rotor blade 32. For this purpose, the temperature measuring device 14 can comprise, for example, an infrared camera, an infrared sensor, a multispectral camera, or a multispectral sensor.

[0087] The natural environmental boundary conditions include at least one of the following conditions: solar radiation 52 absorbed by the rotor blade 32, in particular a global inclined solar radiation, ambient air temperature, wind speed, in particular in the vicinity of the rotor blade 32, radiation temperatures of the sky and / or ground.

[0088] The environmental boundary conditions, in particular at least the wind speed and / or the ambient air temperature, are expediently measured in the vicinity of the rotor blade 32.

[0089] In this case, an interaction of the rotor blade 32 with the natural environmental boundary conditions is specifically changed during the measurement of the temporal course of the surface temperature 50 of the component 34, in particular by specifically changing an orientation and / or a position and / or a speed of the component 34.

[0090] During the measurement of the surface temperature 50 of the component 34, the orientation of the rotor blade 32 relative to the sun and / or the wind direction can be specifically changed. In particular, the azimuth angle 70 of the wind turbine 30 and / or the angle of attack 72 of the rotor blade 32 of the wind turbine 30 can be changed for this purpose.

[0091] In addition, the speed of the wind turbine 30 can also be changed by actively braking the rotor or releasing the brake or by changing the angle of attack 72 of the rotor blades 32.

[0092] Alternatively or additionally, the surface temperature 50 and the environmental boundary conditions of the rotor blade 32 may be measured when a change in the natural environmental boundary conditions acting on the rotor blade 32 occurs.

[0093] Using a digital model of the rotor blade 32, different damages to the rotor blade 32 are simulated on the digital model and a temporal progression of a simulated surface temperature 60, 62 ( Fig. 13) under the temporal course of the ambient boundary conditions of the measurement recorded during the measurement.

[0094] The damage to the rotor blade 32 is now determined by comparing the time course of the measured surface temperature 50 and the surface temperature 60, 62 simulated for the different damages to the rotor blade 32.

[0095] The comparison of the temporal progression of the measured surface temperature 50 of the rotor blade 32 and the surface temperature 60, 62 simulated for the different damages of the rotor blade 32 can be carried out in particular in an automated manner in the evaluation unit 20 arranged in the ground-based device 22 or in the aircraft 10.

[0096] In an alternative embodiment of the system 100, several aircraft 10 can also be used to measure several rotor blades 32 simultaneously.

[0097] The comparison of the temporal profile of the measured surface temperature 50 and the simulated surface temperature 60, 62 for the different damages to the rotor blade 32 can advantageously be carried out by comparing the amplitude and / or phase responses of the measured and simulated profiles. In particular, this can be performed as a function of the frequency of the temporal profiles, in particular by means of a fast Fourier transform (FFT).

[0098] Advantageously, the comparison of the temporal progression of the measured surface temperature 50 and the surface temperature 60, 62 simulated for the different damages of the rotor blade 32 can also be carried out using an artificial intelligence method.

[0099] Fig. 3 shows a cross section through a rotor blade 32 of a wind turbine 30 with marked measuring areas 40, 42.

[0100] The rotor blade 32 has a streamlined cross-section and features a rounded leading edge 36 and a tapered trailing edge 38. The central region is designed as a reinforced web 39. The measuring area 40 is located in the area of ​​the web 39 and has a thicker material. The measuring area 42 is located closer to the trailing edge 38 and has a thinner material.

[0101] In Fig. 4 is a digital model of a measuring area 40, 42 of the rotor blade 32 from Fig. 3. The measuring area 40, 42 is schematically modeled with individual material layers. The surface temperature 50 is measured on the surface of the rotor blade 32. Furthermore, the heat incident from absorbed solar radiation 52, as well as the heat dissipated by convection 54 to the environment and by convection 56 into the interior of the rotor blade 32, are represented by arrows.

[0102] The solar absorption coefficient of the surface of the rotor blade 32 can additionally be determined using a camera in the visual range. For this purpose, the system can include a visual camera for detecting the angular orientation of a corresponding surface element of the rotor blade 32 relative to the sun. This allows the angular orientation of the corresponding surface element of the rotor blade 32 relative to the sun to be taken into account when calculating the absorbed solar radiation. In this way, the absorbed solar radiation can be determined with greater accuracy.

[0103] Fig. Figure 5 shows a digital model of the first measuring area 40 with high material thickness without damage. Fig. 6 to 8 show the digital model of the first measuring area 40 with different damages. Fig. 6 shows the digital model of the first measuring area 40 with a surface damage, for example a paint damage, Fig. 7 with a delamination in the outer area and Fig. 8 with delamination in the inner area.

[0104] Fig. 9 shows a digital model of the second measuring area 42 without damage. Fig. 10 to 12 show the digital model of the second measuring area 42 with the different damages. Fig. 10 shows the digital model of the second measuring area 42 with a surface damage, Fig. 11 with a delamination in the outer area and Fig. 12 with delamination in the inner area.

[0105] The simulation of the surface temperature 60, 62 of the rotor blade 32 is performed using the digital model with the different types of damage. The temporal profiles of the simulated surface temperature 60, 62 can then be compared with the measured surface temperature 50. The temporal profile of the simulated surface temperature 60, 62 that most closely matches the temporal profile of the measured surface temperature 50 can then be used to identify the corresponding damage to the rotor blade 32.

[0106] In Fig. 13 shows such a schematic comparison of temporal courses of a measured surface temperature 50 and of two simulated surface temperatures 60, 62 on a rotor blade 32 as rotor blade 32 according to the method according to the invention.

[0107] The temperature 82 is plotted as a function of time 80. The temporal profiles of the simulated surface temperatures 60, 62 correspond to two different types of damage to the rotor blade 32. Since the profile of the simulated surface temperature 60 essentially corresponds to the measured surface temperature 50, it can be concluded that the damage underlying the digital model used to simulate the profile of the surface temperature 60 is present.

[0108] To evaluate the measured temporal profiles of the surface temperature 50 of the rotor blade 32, a computer program can advantageously be used which includes instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the described method.

[0109] A digital model of the component 34 in the form of the rotor blade 32 of the wind turbine 30, trained, for example, using an artificial intelligence method, can also be used. Reference symbol 10 aircraft 12 unmanned aerial vehicles 14 Temperature measuring device 16 Device for measuring wind speed 18 Device for measuring the environmental boundary conditions 20 Evaluation device 22 ground-based facilities 30 wind turbines 32 rotor blades 34 component 36 leading edge 38 trailing edge 39 jetty 40 measuring range 42 measuring range 44 Surface damage 46 Delamination in the outer area 48 Delamination in the inner area 50 measured surface temperature 52 absorbed solar radiation 54 Convection to the environment 56 Convection into the interior 60 simulated surface temperature 62 simulated surface temperature 70 azimuth angle 72 angle of attack 80 timescale 82 temperature scale 100 systems

Claims

[1] Method for determining damage to at least one rotor blade (32) of a wind turbine (30), at least comprising Measuring a temporal profile of a surface temperature (50) and of natural environmental boundary conditions of the rotor blade (32), by means of a system (100) with at least one aircraft (10), with a targeted change in an interaction of the at least one rotor blade (32) with the natural environmental boundary conditions during the measurement of the temporal profile of the surface temperature (50) of the rotor blade (32), in particular with a targeted change in an orientation and / or a position and / or a speed of the rotor blade (32); and / or Measuring a temporal profile of a surface temperature (50) and the natural environmental boundary conditions of the rotor blade (32) by means of an airborne system (100) with at least one aircraft (10) upon the occurrence of a change in the natural environmental boundary conditions acting on the rotor blade (32); Determining a temporal progression of a simulated surface temperature (60, 62) with a digital model of the rotor blade (32) for different damages to the rotor blade (32) simulated on the digital model under the temporal progression of the environmental boundary conditions recorded during the measurement; Determining the damage to the rotor blade (32) based on a comparison of the time course of the measured surface temperature (50) and the surface temperature (60, 62) simulated for the different damages to the rotor blade (32). [2] Method according to claim 1, wherein the natural environmental boundary conditions comprise at least one of the following conditions: solar radiation (52) absorbed by the rotor blade (32), in particular a global inclined solar radiation, ambient air temperature, wind speed, in particular in the vicinity of the rotor blade (32), radiation temperatures of the sky and / or ground. [3] Method according to claim 1 or 2, wherein during the measurement of the surface temperature (50) of the rotor blade (32) the orientation of the rotor blade (32) to the sun and / or to the wind direction is deliberately changed, in particular, wherein during the measurement an azimuth angle (70) of the wind turbine (30) and / or an angle of attack (72) of the rotor blade (32) of the wind turbine (30) is changed, and / or wherein a rotational speed of the wind turbine (30) is changed during the measurement of the surface temperature (50) of the rotor blade (32). [4] Method according to one of the preceding claims, wherein at least one of the following devices is used to measure the surface temperature (50): infrared camera, infrared sensor, multispectral camera, multispectral sensor. [5] Method according to one of the preceding claims, wherein a solar absorption coefficient of the surface of the rotor blade (32) is determined by means of a camera in the visual range, in particular wherein a solar radiation absorbed in the material of the rotor blade (32) is determined via the absorption coefficient. [6] Method according to claim 5, wherein the absorbed solar radiation is calculated by taking into account the angular orientation of the corresponding surface element of the rotor blade (32) to the sun. [7] Method according to one of the preceding claims, wherein the comparison of the temporal profile of the measured surface temperature (50) and the surface temperature (60, 62) simulated for the different damages of the rotor blade (32) is carried out by comparing amplitude responses and / or phase responses of the measured and simulated profiles, in particular as a function of a frequency of the temporal profiles, in particular by a Fourier transformation. [8] Method according to one of the preceding claims, wherein the comparison of the temporal course of the measured surface temperature (50) and the surface temperature (60, 62) simulated for the different damages of the rotor blade (32) is carried out by means of an artificial intelligence method, in particular wherein the temporal courses of the natural environmental boundary conditions are processed. [9] Method according to one of the preceding claims, wherein the comparison of the time course of the measured surface temperature (50) and the surface temperature (60, 62) simulated for the different damages of the rotor blade (32) is carried out for selected areas (40, 42) of the rotor blade (32) with different material thickness. [10] Method according to one of the preceding claims, wherein the comparison of the time course of the measured surface temperature (50) and the surface temperature (60, 62) simulated for the different damages of the rotor blade (32) is carried out automatically in an airborne system (100) or in a ground-based device (22). [11] Method according to one of the preceding claims, wherein several rotor blades (32) are measured simultaneously with several aircraft (10). [12] System (100) for determining damage to at least one rotor blade (32) of a wind turbine (30), with a method according to one of the preceding claims, at least comprising - a temperature measuring device (14) for measuring a surface temperature (50) of the rotor blade (32), - means (16, 18) for measuring natural environmental boundary conditions of the rotor blade (32), - an evaluation device (20) for carrying out a comparison of a time profile of a measured surface temperature (50) of the rotor blade (32) and a surface temperature (60, 62) simulated for the different damages to the rotor blade (32). [13] System according to claim 12, wherein the natural environmental boundary conditions comprise at least one of the following conditions: solar radiation (52) absorbed by the rotor blade (32), in particular a global inclined solar radiation, ambient air temperature, wind speed, in particular in the vicinity of the rotor blade (32), radiation temperatures of the sky and / or ground. [14] System according to claim 12 or 13, wherein the temperature measuring device (14) and the devices (18) for measuring the natural environmental boundary conditions are arranged at least partially on an aircraft (10), in particular an unmanned aircraft (12), in particular wherein a device (16) for measuring the wind speed is arranged on the aircraft (10). [15] System according to one of claims 12 to 14, wherein the temperature measuring device (14) comprises at least one of the following devices: infrared camera, infrared sensor, multispectral camera, multispectral sensor. [16] The system of any one of claims 12 to 15, further comprising a visual camera for detecting an angular orientation of a corresponding surface element of the rotor blade (32) to the sun. [17] System according to one of claims 12 to 16, further comprising a ground-based device (22) with devices (18) for measuring natural environmental boundary conditions and / or the evaluation device (20). [18] System according to one of claims 14 to 16, wherein the evaluation device (20) is arranged on the aircraft (10). [19] System according to one of claims 14 to 18, further comprising a plurality of aircraft (10) for simultaneously measuring a plurality of rotor blades (32). [20] A computer program for determining damage to a rotor blade (32) of a wind turbine (30), comprising instructions which, when executed by a computer, cause the computer to carry out the steps of a method according to any one of claims 1 to 11. [21] Data processing device for a system (100) according to one of claims 12 to 19 for determining damage to a rotor blade (32) of a wind turbine (30), at least comprising a measurement data acquisition unit for acquiring measurement data from a temperature measuring device (14), as well as devices (16, 18) for measuring natural environmental boundary conditions and an evaluation device (20) with at least one computer. [22] A digital model of a rotor blade (32) of a wind turbine (30) used in a method according to any one of claims 1 to 11.

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