Impulse ball for generating a force impulse to mechanically excite a structural element under investigation, aircraft with the same, and system for detecting a defect with the aircraft

Abstract

Impulse ball (7) for generating a force impulse to mechanically excite a structural element under investigation, in particular a structural element made of laminates, such as a rotor blade or a tower of a wind turbine, or in particular a large and / or difficult-to-access structural element, such as a wind turbine, a bridge structure or an aircraft, or such as a watercraft, in particular for carrying out a method for detecting a defect in the structural element under investigation, comprising: - a ball-like body, - at least one measuring device located in the ball-like body, in particular a force sensor and / or an acceleration sensor, for measuring a force impulse generated with the impulse ball, - at least one reaction detection device, in particular a microphone and / or a laser vibrometer, for measuring a reaction of the structural element,and a wireless and / or wired data transmission device located in the ball-like body, which is data-technically connected to and configured with the at least one measuring device for measuring a force impulse generated by the impulse ball and with the at least one reaction detection device for measuring a reaction of the structural element in order to forward measurement data from the at least one measuring device and the at least one reaction detection device to an evaluation unit located outside the impulse ball, wherein the impulse ball further comprises an elongated, preferably coilable, connecting element which is attached or attachable to the ball-like body and / or wherein the ball-like body is configured to be attached to an elongated, preferably coilable, connecting element.

Description

The present invention relates to a momentum ball for generating a force momentum for mechanically exciting a structural element to be examined, in particular a structural element made of laminates, such as, for example, a rotor blade or a tower of a wind turbine, in particular a large and / or poorly accessible structural element, such as, for example, a wind turbine, a bridge structure or an aircraft, or such as, for example, a watercraft, a manned or unmanned aircraft, in particular rotorcraft, in particular a drone, and a system for detecting a defect location by means of mechanical and / or acoustic momentum excitation in a structural element to be examined, in particular a structural element made of laminates, such as, for example, a rotor blade or a tower of a wind turbine, or in particular a large and / or poorly accessible structural element, such as, for example, a wind turbine, a bridge structure or an aircraft, or such as, for example, a watercraft. Technical fields which may be mentioned are, in particular, surface inspection, material inspection and maintenance. The term "aircraft" is intended to mean, in particular, aircraft with a power drive, such as, for example, an airship.The problem underlying the present invention is explained merely by way of example on rotor blades for wind turbines. However, it is not limited thereto.Industrial pallets are currently used to visually and acoustically check rotor blades of wind power installations. For this purpose, a visual inspection of the entire rotor blade takes place and, if necessary, a manual acoustic excitation / detection of the possible defect location for the detection of material defects takes place. In the case of the so-called belt-web bonds and beam structures, the entire region is also fully acoustically excited and checked independently of a visual test in order to identify invisible damage points.The use of industrial climbing machines represents an economic outlay, a lack of availability and a risk for persons or ergonomic impairment. In addition, human errors are involved in the detection of defective sites, because both the visual inspection and the acoustic excitation / detection are carried out subjectively and individually for each individual person. If necessary, relevant test areas can also be examined only superficially, for example in the case of poor weather.The use of drones (flying drones) for automatic optical surface inspection of wind turbines is state of research. The complete optical detection of the wind turbines has been known as prior art for approximately 2 to 3 years, which is supplemented by a subsequent manual visual inspection and optionally manual sound inspection of areas previously determined as relevant.JP 2021-1 823 A discloses an aircraft-based method for detecting a defect by means of mechanical and / or acoustic impulse excitation in a structural element to be examined, comprising providing a manned or unmanned aircraft, wherein the aircraft comprises a mechanical and / or acoustic impulse generation device for mechanical and / or acoustic excitation of a structural element to be examined and a reaction determination device for determining a reaction of the structural element to an excitation of the structural element by means of a mechanical and / or acoustic impulse, with or without pilot intervention, controlled flying of at least one region of the structural element by means of the aircraft, wherein the flying comprises at least assuming a first predefined position at a distance from a second predefined position on the structural element, applying a mechanical and / or acoustic pulse by means of the pulse generation to the second position on the structural element, determining a reaction of the structural element to the application of the generated pulse to the second predefined position by means of the reaction determination device, comparing the determined reaction with a predefined reference reaction and determining a deviation of the determined reaction from the predefined reference reaction, and outputting a signal that a defect has been determined as a function of the determined deviation. JP 2020-12 676 A, DE 10 2016 214 655 A 1, JP 2019-196 973 A and U.S. Pat. No. 2019) / 0 391 059 A1 relate to similar facts.DE 10 2016 214 655 A1 and JP 2019-196 973 A each relate to a manned or unmanned aircraft, comprising a loudspeaker for generating an acoustic pulse and a reaction determination device.The object of the present invention is to enable automated recognition of damage sites on, in particular large and / or poorly accessible, structural elements, in particular made of fiber composite materials.According to the invention, this object is achieved according to a first aspect by a impulse ball according to claim 1.In the evaluation unit, the data determined with the measuring device and the data determined with the reaction determination device are preferably used for evaluating a predefined reaction related to a force pulse in comparison to a measured reaction related to a force pulse. A predefined or pre-definable minimum deviation corresponds to a detection of a possible defect.Furthermore, according to a second aspect, this object is achieved by a manned or unmanned aerial vehicle according to claim 5.In the impulse ball, it can be provided that the ball-like body consists of steel and / or aluminum and / or plastic and / or rubber.The cable-bound data transmission device advantageously comprises a data cable which extends within the connecting element.Advantageously, the at least one or at least one microphone is arranged in the envelope of the ball-like body.In the case of the aircraft according to claim 5, it can be provided that the impulse ball launcher comprises a cable winch.According to a particular embodiment, the aircraft further comprises an evaluation unit which is connected by data technology via the communication device and the data transmission device of the impulse ball to the at least one force sensor of the impulse ball.In addition, it can be provided that the at least one reaction determination device comprises: a preferably optical reaction determination device, in particular a structure-borne sound measurement device, in particular wherein the structure-borne sound measurement device comprises a laser viscometer, for determining a natural frequency of the structural element in response to an applied acoustic pulse, and / or a preferably acoustic reaction determination device, in particular an airborne sound measurement device, for determining an airborne sound emanating from the structural element in response to an applied acoustic pulse, in particular wherein the airborne sound measurement device comprises a microphone.According to a further particular embodiment, the aircraft further comprises a camera, in particular a wide-angle camera, for determining the measurement position on the structural element, and / or a camera, in particular a zoom camera, for optically checking the surface of the structural element.Furthermore, it can be provided that the aircraft further comprises a position determination device for determining the position of the aircraft.In particular, it can be provided that the position determination device comprises a global position determination system and / or an altimeter.The present invention is based on the surprising finding that, by using an aircraft in combination with mechanical and / or acoustic impulse excitation, no direct contact with a structural element to be examined, for example a rotor blade, has to be produced. For example, an aircraft, in particular a rotorcraft, in particular a drone, would only have to approach a structural element over approximately 10 cm. The method can also be carried out in an automated manner. In addition, the method leads to uniform reproducible and non-individual results.Further features and advantages of the invention are apparent from the appended claims and from the following description of several exemplary embodiments with reference to the schematic drawings, in which: FIG. 1 shows a schematic representation of a system for detecting damage points by means of mechanical and acoustic impulse excitation in a rotor blade to be examined according to a particular embodiment of the present invention; and FIG. 2 shows a schematic illustration of a system for detecting damage points by means of mechanical and acoustic impulse excitation in a rotor blade to be examined according to a further particular embodiment of the present invention.Exemplary embodiments of the present invention are described below using the example of a rotor blade of a wind turbine. However, the invention can also be applied to other objects and structural elements, such as bridge structures, towers, chimneys, buildings, made of concrete / reinforced concrete, which can be checked, for example, by means of the impact-echo method. Quite generally, the aim is the detection of damage sites on an object or structural element to be examined, which can be a rotor blade, but in other examples also, for example, a tower or the like. In the two exemplary embodiments described below, damage sites are detected automatically by means of a drone. In connection with a rotor blade, a defect is in particular a material defect, for example delamination, fiber breakage or the like. Material defects, such as scratches, material breaks, deposits, etc., can weaken the structural element and can potentially be hazardous locations for material fatigue or component failure. In particular in the case of fiber composite materials (FVM), the force-carrying fibers are important for a design-appropriate function of the component.In FIG. 1, the system 100 comprises a drone 2 and an evaluation unit 9 in a control device on the drone 2. the drone 2 has a pulse ball 7 for generating a force pulse for mechanically exciting the rotor blade 1, wherein the pulse ball 7 has a ball-like body and a force sensor (force measurement sensor) 6 located in the ball-like body for measuring a force pulse generated with the pulse ball 7 on the rotor blade 1 and an acceleration sensor 5 located in the ball-like body for measuring an acceleration acting on the pulse ball 7, and a microphone 3.Furthermore, the impulse ball 7 has an antenna 12 for data transmission and a cable 17 for connecting the impulse ball 7 to the drone 2.Furthermore, the drone 2 has a momentum ball launcher 15 for launching the momentum ball 7 in the direction of the rotor blade 1. The impulse ball launcher 15 includes a winch 14 and launcher accelerating rollers 19.In the example shown in FIG. 1, the drone 2 moves systematically on a predefined path along the rotor blade 1 to be examined by controlling flight-mechanical elements 8. For this purpose, one would resort to the flight-mechanical systems known in the prior art.During the flight of the drone 2, the absolute position of the drone 2 with respect to the rotor blade 1 is determined at different times, for example at a distance of two seconds, for example by means of sensor fusion from GPS, altimeter (not shown) and / or evaluation by means of a wide-angle camera (see further-angle camera 21 in FIG. 2 ).For detecting a defect, the drone 2 assumes a first position (in space) which is in a relationship to a second position 16 on the rotor blade 1. The recognition of the defect should thus take place at the second position 16. The second position 16 (or the area or defect) is excited in this example only by a mechanical impulse which is output by the drone 2 by means of the impulse ball 7. The emitted pulse could, however, fundamentally take place mechanically and / or acoustically. When using a mechanical pulse for defect location detection, it is / can be used, for example, the experimental modal analysis according to VDI 4550 and / or local acoustic resonance spectroscopy according to DGZfP-USo6.In the case of an acoustic impulse, this would be generated via a loudspeaker (not shown) located on or on the drone 2.The vibration or natural frequency of the rotor blade 1 arising as a result of the mechanical and / or as a result of an acoustic pulse can be recorded, for example, by means of a laser vibrometer 4 (structure-borne sound), and the airborne sound arising as a result of the mechanical and / or acoustic pulse can be recorded, for example, by means of the microphone 3. By analyzing the recording(s), i.e. the natural frequency or the structure-borne sound or the airborne sound, damage points on the rotor blade 1 can be identified.The drone 2 used for detecting damage locations can be a commercially available drone which has the necessary payload. The drone 2 is configured to perform the method described above. For this purpose, the drone 2 is equipped with the impulse ball 7 together with impulse ball firing device 15 and a microphone 3 as well as a laser vibrometer 4 as reaction determination devices as well as the antenna 12 on the impulse ball 7 and an antenna 12 on the evaluation unit 9 and signal cables 13 for communication between the impulse ball 7 and the control device with the evaluation unit 9 and between the control device and the other components of the drone 2.In this exemplary embodiment, the data evaluation takes place directly on the drone 2. For this purpose, the evaluation unit 9 is equipped, for example, with a data input 10 and a data output 11 and is configured to receive and process the data of the reaction determination devices. The data evaluation could also take place at a central point separate from the drone 2. For this purpose, the data would be transmitted, for example, via the communication device ( 12, 13) to an evaluation unit separate from the drone 2.If a defect site is detected, the data value of the second position 16 at which the defect site was determined is stored, for example, in a memory 18 on or on the drone 2 by data technology.Quite generally, the method for detecting defective sites could proceed as follows:- the drone 2 assumes a first predefined position in space, wherein the first predefined position is characterized by a distance from a second predefined position 16 on the rotor blade 1,applying a pulse by the drone 2 to the second predefined position 16 on the rotor blade 1,determining a response occurring in response to applying the pulse to the second predefined position 16; anddetecting a deviation of a response from a predefined reference and, in response thereto, outputting a signal.The mode of operation of the impulse ball launcher 15 and its elements is described in more detail below by way of example: the drone 2 is linked to the impulse ball launcher 15 by information technology via the signal cable 13. The impulse ball 7, in analogy to an impulse hammer, can consist of different materials (for example steel, aluminum, plastic, rubber etc.) and sizes with which the usable frequency range can be adjusted. In this application, a rubber ball having a diameter of, for example, approximately 2 to 5 cm is preferably used as the starting point, which rubber ball does not damage the rotor blade 1 during the impact.The force sensor 6, the acceleration sensor 5 and the microphone 3 within the impulse ball 7 are connected to the evaluation unit 9 by data technology via the antenna 12. The evaluation unit 9 can be located on the drone 2 or at another location, for example in a computer on the ground, in the vicinity of the rotor blade 1. The data connection between the impulse ball 7 and the evaluation unit 9 is wired (signal cable 13) in this example, but could also be wireless (for example WLAN, Bluetooth) via an antenna 12. The impulse ball 7 is firmly connected to the cable 17 with the cable winch 14 in the impulse ball launcher 15. The cable 17 could be equipped with a data cable on the inside.When a first predefined position has been reached in the space at which a mechanical impulse is to be output, a signal is output from the control device to the impulse ball launcher 15. If a signal for ejecting the impulse ball 7 is present, the cable winch 14 is released and the impulse ball 7 is accelerated at a predefined speed via the launcher acceleration rollers 19 and in this way "shot" onto the second predefined position 16 on the rotor blade 1. By means of the acceleration sensor 5 and the force sensor 6, the impulse applied to the rotor blade 1 is detected by measurement technology. In addition, measurement data of the effect of the mechanical pulse are recorded with the laser viscometer 4 and / or the microphone 3. The measurement data is transmitted to the evaluation unit 9 by information technology. The evaluation unit 9 is configured to perform a sound test on the basis of the determined reaction. Depending on the embodiment, a structure-borne sound test with the laser vibrometer 4 or an airborne sound test with the microphone 3 can be carried out here. In airborne sound testing, wind noises must be compensated, which can preferably be realized with classic wind protection covering for microphones and / or the construction of the microphones directly in the impulse ball 7. The impulse ball 7 is then retracted again into the impulse ball launcher 15 by the cable winch 14 with the connection element (cable 17 in this example) being drawn in and can then be fired again.The embodiment shown in FIG. 2 is different from the embodiment shown in FIG. 1 in that it additionally includes a zoom camera 20 and a wide-angle camera 21. The wide-angle camera 21 serves for defining the position of the drone 2 with respect to the rotor blade 1, while the zoom camera 20 serves for optically capturing the rotor blade surface.The recognition of defective locations can take place in combination with a preceding, optical defective location recognition (see FIG. 2 ). If a visual examination was carried out beforehand by means of a drone, subsequent detection of the defect can be supplemented by the same drone, for example drone 2, which was used for the visual detection of the defect. The measurement can be carried out directly following the optical determination of the defect or at a later point in time. During the (preliminary) flight, the surface of the rotor blade 1 can be visually inspected. The surface inspection can be carried out by means of an optical detection of the rotor blade surface by the zoom camera 20. The determined data can be sent to the same evaluation unit 9 and can be evaluated there with regard to possible damage points, for example using a deep machine learning algorithm. If a defect site is identified, the data value of the absolute second position 16, for which the image data were determined, is stored with the information about the defect site in the memory 18 by data technology.The features of the invention disclosed in the above description, in the drawings and in the claims can be essential for the realization of the invention in its various embodiments both individually and in any combinations.

Claims

Impulse ball (7) for generating a force impulse for mechanically exciting a structural element to be examined, in particular a structural element made of laminates, such as a rotor blade or a tower of a wind turbine, or in particular a large and / or poorly accessible structural element, such as a wind turbine, a bridge structure or an aircraft, or such as a watercraft, in particular for carrying out a method for detecting a defect in the structural element to be examined, comprising - a ball-like body, - at least one measuring device located in the ball-like body, in particular a force sensor and / or an acceleration sensor, for measuring a force impulse generated with the impulse ball, - at least one reaction determination device, in particular a microphone and / or a laser viscometer, for measuring a reaction of the structural element, and - a wireless and / or cable-bound data transmission device located in the ball-like body, which is connected in terms of data technology to the at least one measuring device for measuring a force impulse generated with the impulse ball and to the at least one reaction determination device for measuring a reaction of the structural element and is configured to forward measurement data from the at least one measuring device and the at least one reaction determination device to an evaluation unit located outside the impulse ball, wherein the impulse ball further comprises an elongated, preferably windable, connecting element which is fastened or can be fastened to the ball-like body and / or wherein the ball-like body is configured to be fastened to an elongated, preferably windable, connecting element.Impulse ball (7) according to claim 1, wherein the ball-like body consists of steel and / or aluminum and / or plastic and / or rubber.The impulse ball (7) according to claim 1 or 2, wherein the wired data transmission device comprises a data cable extending within the connection element.The impulse ball (7) according to any one of claims 1 to 3, wherein the at least one or at least one microphone is arranged in the shell of the ball-like body.Manned or unmanned aircraft, in particular rotorcraft, in particular drone (2), in particular for carrying out a method for detecting a defect location in a structural element to be examined, comprising: - a momentum ball (7) according to one of Claims 1 to 4, - a momentum ball firing device (15) for firing the momentum ball (7), wherein the momentum ball (7) is connected via its connecting element or a connecting element to the momentum ball firing device (15) for retrieving the momentum ball (7) after a firing, - a communication device for communication with the data transmission device of the momentum ball (7).The aircraft of claim 5, wherein the impulse ball launcher (15) comprises a winch (14).Aircraft according to claim 5 or 6, further comprising - an evaluation unit (9) which is connected via the communication device and the data transmission device of the impulse ball (7) to the at least one force sensor (6) and / or the at least one acceleration sensor (5) and / or the at least one microphone (3) of the impulse ball (7) in terms of data technology.Aircraft according to one of claims 5 to 7, wherein the at least one reaction determination device comprises: - a preferably optical reaction determination device, in particular a structure-borne sound measurement device, in particular wherein the structure-borne sound measurement device comprises a laser viscometer, for determining a natural frequency of the structural element in response to an applied acoustic impul, and / or a preferably acoustic reaction determination device, in particular an airborne sound measurement device, for determining an airborne sound emanating from the structural element in response to an applied acoustic pulse, in particular wherein the airborne sound measurement device comprises a microphone.Aircraft according to one of claims 5 to 8, further comprising a camera, in particular a wide-angle camera (21), for determining the measurement position on the structural element, and / or a camera, in particular a zoom camera (20), for optically checking the surface of the structural element.Aircraft according to one of claims 5 to 9, further comprising a position determination device for determining the position of the aircraft.Aircraft according to claim 10, wherein the position determining device comprises a global position determining system and / or an altimeter.System for detecting a defect by means of mechanical and / or acoustic impulse excitation in a structural element to be examined, in particular a structural element made of laminates, such as a rotor blade (1) or a tower of a wind turbine, or in particular a large and / or poorly accessible structural element, such as a wind turbine, a bridge structure or an aircraft, or such as a watercraft, comprising: - a manned or unmanned aircraft according to Claim 5 and - an evaluation unit (9) which is arranged on or on the rotorcraft or separately therefrom, e.g. on the ground.

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