DE112018004704T5 - Sensor arrangement for the detection of bending moments in an elongated component, elongated component, sensor system and wind turbine - Google Patents

Abstract

A sensor arrangement for detecting bending moments in an elongated component (e.g. a rotor blade of a wind turbine). The sensor arrangement comprises a measuring rod which extends at least at a predetermined distance parallel to the direction of elongation of the elongate component and transversely to the bending axis. The sensor arrangement further comprises a fixing element that is attached to a distal end of the measuring rod, wherein the fixing element is designed to firmly attach the measuring rod to a surface of the elongate component, and a support element that is attached to a proximal end of the measuring rod opposite the distal end is configured with the support element for fixed attachment to the surface and for sucking the measuring rod in such a way that it enables an axial displacement thereof. Furthermore, the sensor arrangement comprises a displacement sensor (for example inductive sensor) which is arranged adjacent to and at a distance from the proximal end of the measuring rod and is set up to output a signal which indicates the axial displacement (for example a metal tip) of the measuring rod. The measuring rods are made of the same material (e.g. fiberglass) as an elongated component. Preferably three or four of the sensor arrangements are arranged at angular intervals around an inner circumferential surface of the rotor blade root. Furthermore, an elongated component, a sensor system and a wind turbine are disclosed.

Description

The invention relates to techniques for detecting bending moments in components and, in particular, to an improved sensor arrangement for detecting bending moments in an elongated component (such as a rotor blade of a wind turbine) and an elongated component, sensor system and wind turbine.

In systems such as wind turbines, significant bending moments are induced in elongated components, particularly in the case of rotor blades and the turbine tower. In other industries, e.g. B . similar problems arise with components made of glass fiber, metal etc.; In order to ensure safe and trouble-free operation, it is desirable to measure the bending moments that occur in the components precisely.

1. (i) Bereitstellen einer wesentlichen Eingabe für intelligente Steuerungszwecke, Erleichterung der Ausrüstungsgewichtsreduktion;
2. (ii) direkte Schätzung/Bewertung des Windfeldes vor dem Rotor (Windgeschwindigkeit, Windscherung vertikal & horizontal);
3. (iii) Rotorblattsteigungsausrichtung; und
4. (iv) Zählen von Zyklen für Lebensdauerzwecke für die Rotorblätter und die Rotorwelle.

Knowledge of the rotor blade bending moments with regard to the following design aspects of a wind turbine is of particular importance:

1. (i) providing essential input for intelligent control purposes, facilitating equipment weight reduction;
2. (ii) direct estimation / evaluation of the wind field in front of the rotor (wind speed, wind shear vertical &horizontal);
3. (iii) rotor pitch alignment; and
4. (iv) Counting life cycle cycles for the rotor blades and rotor shaft.

It is known to measure the bending moments arising in the rotor blades of wind power plants by means of dynamic mechanical spectroscopy (DMS) applied directly to the rotor blades. However, the equipment for such techniques has a limited lifespan and complex signal amplification is required.

It is also known to measure the bending moments on the basis of indirectly applied strain gauges. With such techniques, however, there can be a strong influence on the adhesive layer, which manifests itself as the influence of temperature and signs of aging; and the selective attachment makes the sensor susceptible to strain gradients / bulge effects in the rotor blade.

Techniques are also known in which active or passive fiber-optic sensors are used and methods in which the glass fibers are laid on or in the rotor blade wall. Such techniques are for example in EP2778602B1 disclosed. However, these techniques require very expensive analysis units to implement the optical signal, so that they can have a low level of reliability and a temperature-driven expansion component only has to be compensated for by extensive learning.

Another known technique involves the use of laser or light beams and transmitters, receivers and possibly mirrors in the rotor blade in order to detect the movement of the rotor blade tip (an outer part of the rotor blade) relative to the rotor blade root. However, these techniques suffer from similar drawbacks in the above-mentioned fiber optic based methods.

Another known technique involves integrating the sensed acceleration of a portion / portion of the rotor blade that is outside the rotor blade root with the rotor blade speed or rotor blade tip deviation. WO2015 / 014366 discloses a wind turbine with at least one rotor blade and a load sensor arranged at a root end of the rotor blade. An optical accelerometer is disposed within the rotor blade near a tip thereof, and a controller is connected to the accelerometer via one or more optical fibers that extend the length of the rotor blade and are configured to adjust the wind turbine based on the measured load and the control measured acceleration to keep the load on the rotor blade below a predetermined threshold level.

EP2898216B 1 discloses a method for monitoring the condition of a rotor blade of a wind turbine, comprising: measuring an acceleration of the rotor blade with a first signal using a fiber-optic acceleration sensor, the acceleration being measured at a first radial position at a predetermined distance from the rotor blade root in at least one direction a first directional component orthogonal to the axis of the rotor blade, measuring an elongation of the rotor blade with a second signal by means of a fiber optic strain sensor, the elongation being measured at a second radial position which is arranged in the region of the first radial position relative to the rotor blade root, by bending moments in two , typically measuring orthogonal directions; Determining a first change in position by integrating the acceleration over time; Determining a first value corresponding to the rotor blade stiffness by calculation based on the first position change and the elongation; and determining the rotor blade condition from the first value. The first radial position can be arranged approximately at half the blade radius or between half the blade radius and a rotor blade tip and / or the second radial position may be 5 meters or less from the root of the leaf.

Other techniques based on acceleration signals are in DE102010032120A1 disclosed.

In the case of techniques with integration of the detected acceleration, due to the rotary movement of the rotor blade, the azimuth movement of the nacelle around the tower shaft / axis (active, passive) of the wind turbine and the tower movement, as well as other errors that occur due to permanent integration, the accuracy, in particular of the deviation result, is limited. In addition, when using conventional acceleration sensors, there is a high risk of destruction / damage to the electrical lines and sensors in the rotor blade due to the effect of a lightning strike.

• - Robustheit/Zuverlässigkeit ist nicht ausreichend;
• - für elektrische Bauteile im Rotorblatt, die in einem Abstand von der Rotorblattwurzel positioniert sind, besteht die Gefahr einer Zerstörung durch Blitzeinschläge;
• - für Expansion-oder Abweichungs-basierte Verfahren, gewöhnlich nicht-triviale Verfahren zum Kompensieren des Temperatureinflusses/ -effekts auf die Rotorblattleistung/ - reaktion, die in der Praxis verwendet oder gelernt werden müssen, was zum Teil separate Sensoren erfordert;
• - bei Verfahren mit faseroptischen Sensoren, die bei der Herstellung in Rotorblattwände integriert sind, besteht keine Reparaturmöglichkeit, wenn die faseroptischen Kabel fehlerhaft, beschädigt oder nicht funktionieren; und
• - die Kosten der bekannten Lösungen können extrem hoch sein.

Accordingly, known solutions have the following disadvantages or lead to the following problems:

• - Robustness / reliability is not sufficient;
• - For electrical components in the rotor blade, which are positioned at a distance from the rotor blade root, there is a risk of being destroyed by lightning strikes;
• for expansion or deviation-based methods, usually non-trivial methods for compensating the temperature influence / effect on the rotor blade power / response, which have to be used or learned in practice, which in some cases requires separate sensors;
• - In the case of processes with fiber-optic sensors that are integrated in the rotor blade walls during manufacture, there is no possibility of repair if the fiber-optic cables are faulty, damaged or not working; and
• - The cost of the known solutions can be extremely high.

The object of the present invention is to overcome the aforementioned problems and to provide an improved sensor arrangement for detecting bending moments in an elongated component, a sensor system and a wind energy installation.

Summary

According to one aspect of the invention, a sensor arrangement for detecting bending moments in an elongated component, for example a rotor blade of a wind energy installation, is provided, the sensor arrangement comprising: a measuring rod which is at least at a predetermined distance parallel to the elongation direction of the elongated component and transversely to the bending axis extends; a fixing element, which at one of a proximal end and a distal end of the measuring rod, wherein the fixing element is configured to fix the measuring rod firmly to a surface of the elongate component; a support member attached to the other of the proximal end and the distal end of the dipstick, the support member configured to be fixedly attached to the surface and to support the dipstick so as to allow axial displacement thereof; and a displacement sensor which is arranged adjacent and spaced from the proximal end of the measuring rod, the sensor being designed to output a signal which indicates the axial displacement of the measuring rod; the measuring rods are made of the same material as the elongated component.

The predetermined distance is preferably in the range of 10-200 cm, preferably 20-100 cm and more preferably 20-50 cm.

The measuring rod preferably has a diameter which is in the range from 1-10 mm, preferably 2-8 mm and particularly preferably 4-6 mm.

The distance is preferably in the range 2-30%, preferably 5-20% and particularly preferably 10-15% of the length of the elongate component.

The fixing element is preferably designed to support an axis of the measuring rod at a predetermined distance from the surface.

The predetermined distance is preferably in the range 1-10x , more preferred 2-5x and particularly preferred 2-3x of the diameter of the measuring rod.

The support element preferably has a bearing or bearing surface which is set up to enable the measuring rod to slide relative to the latter.

A metal tip is preferably arranged at the proximal end of the measuring rod. In one embodiment, the displacement sensor comprises an inductive sensor.

In another embodiment, the displacement sensor comprises a capacitive sensor, a magnetic sensor or an optical sensor.

The displacement sensor is preferably set up to detect axial displacements of the measuring rod in the range of ± 10 mm

The displacement sensor is preferably set up to detect axial displacements of the measuring rod with a resolution of 0.1%.

The measuring rod preferably consists of glass fiber or carbon.

According to a further aspect of the invention, an elongated component, for example a knife of a wind power installation, is provided, on which a sensor arrangement according to one of claims 1 to 13 of the appended claims is attached.

A plurality of the sensor arrangements are preferably attached to the elongate component, the displacement sensor of each sensor arrangement issuing a respective signal which indicates a displacement detected by this sensor arrangement.

The sensor arrangements are preferably attached to the surface spaced around the cross-sectional circumference of the measuring rod.

The sensor arrangements are preferably arranged on the surface at equal angles around the cross-sectional circumference of the measuring rod.

In one embodiment, three sensor arrangements are attached to the surface. Such sensors are preferably attached to the circumference of the rotor blade root in order to measure or calculate the two orthogonal rotor blade root bending moments and the acting axial force.

In another embodiment, four sensor arrays are attached to the surface. The sensor arrangements are preferably arranged as two pairs of diametrically opposite sensor arrangements. With four sensors facing each other, the two bending moments can be measured directly, with the axial force being compensated for directly.

Preferably the elongate member is hollow and the surface is an inner surface. Preferably, the sensor assemblies are attached to a portion of the surface at one end of the elongate member.

The elongate component is preferably a rotor blade for a wind energy installation. The section of the surface is preferably located at or adjacent to the root end of the rotor blade.

The elongate component is preferably formed from glass fiber or carbon.

According to a further aspect of the invention, a sensor system for detecting bending moments in an elongated component, for example a rotor blade of a wind energy installation, is provided, the sensor system comprising: a plurality of sensor arrangements according to one of claims 1 to 13 of the appended claims or an elongated component according to any of claims 14 to 25 of the appended claims; and a processing circuit is coupled to receive the signal output by the displacement sensor of each sensor arrangement; wherein the processing circuit is configured to determine the bending moment in an elongate member based on the signals indicative of the axial displacements of the measuring rods.

Each displacement sensor is preferably coupled to the processing circuit via an overvoltage protection circuit.

Preferably, the processing circuit is coupled to one or more pitch sensors, each pitch sensor configured to provide the processing circuit with a signal indicative of a pitch sensor of a respective elongated component, the processing circuit configured to adjust the bending moment based on to determine the signals indicating the axial displacements and the pitch angle.

According to a further aspect of the invention there is provided a wind turbine comprising: a plurality of sensor arrangement units according to one of claims 1 to 13 of the appended claims, an elongated component according to one of claims 14 to 25 of the appended claims or a sensor system according to one of claims 26 to 28 of the accompanying claims.

An advantage of the invention is that the use of position / displacement sensors significantly improves robustness and / or reliability.

Another advantage is that no electrical components are arranged in the rotor blade at a distance from the rotor blade root, as a result of which the risk of destruction by lightning is reduced.

Another advantage of the invention is that in embodiments there is a direct compensation of the temperature influence.

A further advantage is that the devices used in embodiments offer the possibility of simple retrofitting / reassembly or repair.

Another advantage of the invention is that compared to known solutions Costs, e.g. B . can be significantly reduced by two thirds in certain embodiments.

Another advantage is that the detection of the presence of ice on the rotor blade and the identification of vibration forms and / or the influence of turbulence in the wind direction behind the wind turbine generators (WTGs) are improved.

Figure list

• 1 (Stand der Technik) zeigt eine bekannte Windenergieanlage mit mehreren Rotorblättern;
• 2 zeigt eine axiale Querschnittsansicht einer Rotorblattwurzel eines Rotorblattes von 1, die Sensoranordnungen gemäß einer Ausführungsform der Erfindung zeigt;
• 3 zeigt eine vergrößerte Ansicht des Details B von 2;
• 4 zeigt eine vergrößerte Ansicht des Details a von 2; und
• 5 ist eine transversale Querschnittsansicht einer Rotorblattwurzel eines Rotorblatts von 1, bei (a) drei gleichmäßig beabstandeten Sensoranordnungen und (b) zwei Paaren von diametral gegenüberliegenden Sensoranordnungen.

Further details of the invention emerge from the drawings according to the description. The drawings show:

• 1 (State of the art) shows a known wind turbine with several rotor blades;
• 2nd shows an axial cross-sectional view of a rotor blade root of a rotor blade of FIG 1 10 showing sensor arrangements according to an embodiment of the invention;
• 3rd shows an enlarged view of the detail B from 2nd ;
• 4th shows an enlarged view of detail a of 2nd ; and
• 5 10 is a transverse cross-sectional view of a rotor blade root of a rotor blade of FIG 1 , with (a) three equally spaced sensor arrangements and (b) two pairs of diametrically opposed sensor arrangements.

1 (State of the art) shows a known wind turbine 1 with several rotor blades. The wind turbine 1 includes a tower 3rd and a gondola 2nd that are rotatable on the tower 3rd is mounted. The gondola 2nd includes a nacelle cover 4th attached to a main frame (not shown), which is discussed in more detail below. On a rotor shaft (not shown) inside the nacelle 2nd is a rotor 7 arranged, which in turn is a hub 5 and at least one rotor blade 6 includes (here three).

Near the axis of the hub 5 becomes an end section or rotor blade root 8th of the rotor blade 6 held in place, eg inside the jacket 9 . It is desirable to provide devices for measuring bending moments about the y and / or z axis and / or axial forces (along the x axis), as described in more detail below.

2nd shows a longitudinal sectional view of a rotor blade root 8th of a rotor blade 6 from 1 , the sensor arrays 10th according to an embodiment of the invention. The rotor blade 6 consists of glass fiber. However, it is understood that the rotor blade 6 can be made of other materials, such as carbon or carbon composites. Any sensor arrangement 10th is on a surface section 12 at or near the end 14 of the rotor blade 6 arranged, ie around in the sensor arrangement according to the invention 10th not the expansion of the wall material of the rotor blade 6 in the area of the rotor blade root 8th To measure, the strain between two points, which are at a sufficiently large distance from one another, is measured directly, as a result of which the influence of stress expansion gradients and bulges is kept negligibly small.

Any sensor arrangement 10th is structured as follows. A measuring rod 16 extends along the length of the surface section 12 and therefore essentially spans the length of the rotor blade root 8th . The measuring rod 16 consists of the same material as the rotor blade 6 , ie glass fiber (or from other materials such as carbon or possibly carbon composites). This serves a "natural" temperature compensation with regard to temperature effects on the rotor blade root 8th to guarantee. It should be noted that the temperature distribution in the spatial extent of a rotor blade root 8th is not uniform and therefore the temperature compensation must be specific to the sensor position.

3rd shows an enlarged view of the detail B of the 2nd . A fastener 18th is firmly on the surface section 12 attached, e.g. B. by a strong adhesive (not shown). It is also the distal end 20th the measuring rod 16 again over a rigid angle bracket 19th firmly with the fastener 18th connected to the dipstick 16 (which is glued into a recess of the same with the strong adhesive, for example).

Returning to 2nd is at or near the proximal end 22 the measuring rod 16 a support element 24th provided that firmly on the surface section 12 is attached, e.g. B. with a strong adhesive. In this embodiment, the measuring rod passes through 16 an axial passage (not shown) in the support member 24th with play, causing an axial / longitudinal movement of the measuring rod 16 relative to the support element 24th is made possible. In embodiments, bearings and / or lubricant, such as grease, can be located between engagement surfaces of the support member 24th and the measuring rod 16 be provided. A number of additional support elements 24 ' , 24 " can between the fastener 18th and the support member 24th be provided (e.g. equally spaced).

Any sensor arrangement 10th also includes a position / displacement sensor 26 . With reference to 4th shows an enlarged view of the Details A from 2nd . The displacement sensor 26 is on the surface section 12 the rotor blade wall 27th appropriate. In this embodiment is a metal tip 28 (e.g. steel) at the proximal end 22 the measuring rod 16 provided, and the displacement sensor 26 includes an inductive sensor for detecting position or changes in position. In this way a movement / change in position of a point (e.g. the proximal end 22 ) against another (e.g. B . Support element 24th or displacement sensor 26 ) can be measured using a simple, robust position sensor, usually without further signal processing. It is understood that the displacement sensor 26 alternatively can comprise a capacitive sensor, a magnetic sensor or an optical sensor.

In this embodiment, signals are transmitted by the displacement sensors 26 on the rotor blade 6 (a "first rotor blade") are generated via the lines 28 and the surge protection unit 30th to the first entrances 32 connected to the processing circuit 34. The latter also includes a second entrance 36 and a third entrance 38 for receiving signals indicating movement / change in position from second and third rotor blades (not shown). The processing circuit 34 also includes a fourth input 38 configured to receive a signal that is a pitch angle of the first rotor blade 6 from the pitch sensor 40 displays. The processing circuit 34 also includes a fifth entrance 42 and a sixth entrance 44 for receiving signals indicative of movement / change in position from the second and third rotor blades (not shown).

The processing circuit 34 preferably includes a wind turbine generator programmable logic controller (WTG-PLC) configured to apply bending moments in the rotor blade root 8th ( 1 ) to calculate the y and / or z axis and / or axial forces (along the x axis) based on the various position / displacement signals and pitch angle signals using techniques known in the art.

5 (a) is an axial cross-sectional view of a rotor blade root 8th , in one embodiment with three equally spaced sensor arrangements 10th , 10 ' and 10 " .

These are at equal (120 degrees) angular intervals around the inner surface 12 the rotor blade root 8th arranged. If three such sensors on the circumference of the rotor blade root 8th are attached, the two orthogonal leaf root bending moments and the acting axial force, as mentioned above, can be measured or calculated.

5 (b) is an axial cross-sectional view of a rotor blade root 8th , in another embodiment (corresponding 2nd ) with two pairs of diametrically opposed sensor arrangements 10th , 11 . If four sensors are used so that two within a pair face each other and are connected to each other and a signal addition is used, the two bending moments can be measured directly, whereby the axial force influence is directly compensated for.

Although the invention has been described above with respect to rotor blades of wind turbines, it is understood that the techniques are applicable to any slim / elongated structure or structural component, such as the tower / shaft of a wind turbine.

List of reference characters

1

Wind turbine

2nd

gondola

3rd

tower

4th

Nacelle cover

5

hub

6

Rotor blade

7

rotor

8th

Rotor blade root

9

coat

10th

Sensor arrangement

10 '

Sensor arrangement

10 "

Sensor arrangement

11

Sensor arrangement

12

Surface section

14

The End

16

Dipstick

18th

Fastener

19th

rigid angle bracket

20th

distal end

22

proximal end

24th

Carrier element

24 '

Carrier element

24 "

Carrier element

26

Position / displacement sensor

27th

Rotor blade wall

28

Metal tip

29

cables

30th

Surge protection unit

32

first entrance

34

Processing circuit

36

second entrance

38

third entrance

39

fourth entrance

40

Pitch angle sensor

42

fifth entrance

44

sixth entrance

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 2778602 B1 [0006]
• WO 2015/014366 [0008]
• EP 2898216 B [0009]
• DE 102010032120 A1 [0010]

Claims (19)

Sensor arrangement for detecting bending moments in an elongated component, for example a rotor blade of a wind power plant, the sensor arrangement comprising: a measuring rod which extends at least a predetermined distance parallel to the direction of elongation of the elongate component and transversely to the bending axis; a fixation member attached to one of a proximal end and a distal end of the dipstick, the fixation member configured to securely attach the dipstick to a surface of the elongate member; a support member attached to the other of the proximal end and the distal end of the measurement rod, the support element configured to be fixedly attached to the surface and to support the measurement rod so as to allow axial displacement thereof; and a displacement sensor located adjacent and spaced from the proximal end of the measuring rod, the sensor being configured to output a signal which indicates the axial displacement of the measuring rod; the measuring rods are made of the same material as the elongated component. Sensor arrangement after Claim 1 , characterized in that the predetermined distance is in the range of 10-200 cm, preferably 20-100 cm, and more preferably 20-50 cm. Sensor arrangement (1) after Claim 1 or 2nd , characterized in that the measuring rod has a diameter which is in the range 1-10 mm, preferably 2-8 mm and more preferably 4-6 mm. Sensor arrangement (1) after Claim 1 , 2nd or 3rd , characterized in that the predetermined distance is in the range 2-30%, preferably 5-20% and more preferably 10-15%, of the length of the elongated component. Sensor arrangement (1) according to one of the Claims 1 to 4th , characterized in that the fixing element is designed to support an axis of the measuring rod at a predetermined distance from the surface. Sensor arrangement (1) according to one of the preceding claims, characterized in that the predetermined distance is in the range 1-10x, preferably 2-5x and more preferably 2-3x of the diameter of the measuring rod. Sensor arrangement (1) according to one of the preceding claims, characterized in that the supporting element has a bearing or bearing surface which is set up to enable the measuring rod to slide relative to the latter. Sensor arrangement (1) according to one of the preceding claims, characterized in that a metal tip is arranged at the proximal end of the measuring rod. Sensor arrangement after Claim 8 , characterized in that the displacement sensor comprises an inductive sensor. Sensor arrangement (1) according to one of the Claims 1 to 8th , characterized in that the displacement sensor comprises a capacitive sensor, a magnetic sensor or an optical sensor. Sensor arrangement (1) according to one of the preceding claims, characterized in that the displacement sensor is set up to detect axial displacements of the measuring rod in the range of ± 10 mm. Sensor arrangement (1) according to one of the preceding claims, characterized in that the displacement sensor is set up to detect axial displacements of the measuring rod with a resolution of 0.1%. Sensor arrangement (1) according to one of the preceding claims, characterized in that the measuring rod consists of glass fiber or carbon. Elongated component, for example a rotor blade of a wind power plant, the elongated component having a sensor arrangement according to one of the preceding claims. Elongated component after Claim 14 , characterized in that several of the sensor arrangements are attached to it, the displacement sensor of each sensor arrangement outputing a respective signal which indicates a displacement detected by this sensor arrangement. Sensor system for detecting bending moments in an elongated component, for example a rotor blade of a wind power plant, the sensor system comprising: a plurality of sensor arrangements according to one of the Claims 1 to 13 or an elongated component according to one of the Claims 14 to 25; and a processing circuit coupled to receive the signal output from the displacement sensor of each sensor array; wherein the processing circuit is configured to determine the bending moment in an elongate member based on the signals indicative of the axial displacements of the measuring rods. 27. The sensor system according to claim 26, wherein each displacement sensor is coupled to the processing circuit via an overvoltage protection circuit. 28. The sensor system of claim 26 or 27, wherein the processing circuit is coupled to one or more pitch sensors, each pitch sensor configured to provide the processing circuit with a signal indicative of a pitch sensor of a respective elongated component, the processing circuit configured is to determine the bending moment based on the signals indicating the axial displacements and the pitch angle. Wind turbine, comprising: several sensor arrangements according to one of the Claims 1 to 13 , an elongated component according to one of the Claims 14 to 25 or a sensor system according to any one of claims 26 to 28.

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