Pitch angle measuring device and method for fan blade

Abstract

The invention relates to a pitch angle measuring device and a pitch angle measuring method for fan blades. The measuring device comprises a propeller pitch measuring transmission end, a propeller pitch measuring transmission end, a propeller pitch measuring transmission end, a propeller pitch measuring transmission end and a propeller pitch measuring transmission end, wherein the measuring rod can drive the rolling body under the action of the compression spring, so that the rolling body is tightly attached to the propeller pitch adjusting rocker arm; the propeller pitch adjusting rocker arm comprises a propeller pitch adjusting reference rocker arm and a propeller pitch adjusting measuring rocker arm; and a pitch measurement receiving end; wherein the propeller pitch adjustment reference rocker arm is provided with a circular hub correction surface, and the propeller pitch adjustment measurement rocker arm is provided with a cam hub measurement surface.

Description

Technical Field

[0001] The present application relates to a pitch angle measuring device and a measuring method for a fan blade. Background Art

[0002] An open fan engine adjusts the pitch angle of the fan blade through a pitch control system, enabling the fan blade to operate at an appropriate incoming flow angle of attack under different working conditions, improving the working efficiency and reducing the fuel consumption rate of the engine.

[0003] In order to perform real-time calculation and feedback on the pitch angle, it is necessary to measure and collect data on the pitch angle of the fan blade under working conditions. By means of the relationship between the blade angle, the blade rotation speed, and the engine power, closed-loop control of the blade angle is achieved, thereby improving the working efficiency of the open fan. For most propeller aircraft, since the turbine output shaft and the propeller input shaft of many turboprop engines are not coaxial, in the existing technology solutions, generally, an LVDT (Linear Variable Displacement Transducer) is installed inside the actuator to measure the displacement of the actuator piston, and the pitch angle of the propeller fan is calculated based on the piston displacement.

[0004] However, for open rotor engines and some propeller aircraft, since the propeller fan input shaft and the turbine output shaft are coaxial, it is impossible to measure the pitch angle of the propeller fan by using the technical solution with an LVDT. Instead, a non-contact Hall sensor is arranged near the root of the blade to measure the pitch angle of the propeller fan.

[0005] However, for the above-described existing technology solutions, due to the introduction of a reference angular displacement measuring mechanism and a displacement angle measuring mechanism, a rotor unbalance amount will be generated when they are symmetrically arranged, and this unbalance amount varies with different pitch angles and cannot be directly balanced, increasing the vibration of the propeller fan during the working state and affecting flight safety.

[0006] Therefore, for an open fan engine with a coaxial turbine output shaft and fan input shaft, there is a need in the art for an effective pitch angle measuring device and a measuring method that can reduce or avoid the generation of dynamic unbalance. Summary of the Invention

[0007] One object of the present application is to provide a pitch angle measuring device for a fan blade.

[0008] One object of the present application is to provide a measuring method.

[0009] A pitch angle measuring device for a fan blade according to the first aspect of the present application, the measuring device comprising: a pitch measurement driving end, including a rolling body, a measuring rod, a compression spring, and a sensor sensing end; wherein, the measuring rod can drive the rolling body under the action of the compression spring to make the rolling body closely adhere to the pitch adjustment rocker arm; the pitch adjustment rocker arm includes a pitch adjustment reference rocker arm and a pitch adjustment measurement rocker arm; and a pitch measurement receiving end; wherein, the pitch adjustment reference rocker arm has a circular hub calibration surface, and the pitch adjustment measurement rocker arm has a cam hub measurement surface; when the pitch adjustment reference rocker arm is driven, the distance between the sensor sensing end and the pitch measurement receiving end is a first distance, and this first distance remains unchanged; when the pitch adjustment measurement rocker arm is driven, the rolling body drives the sensor sensing end to move, so that the distance between the pitch measurement driving end and the pitch measurement receiving end is a second distance, and this second distance changes.

[0010] In one or more embodiments of the measuring device, the sensor sensing end and the pitch measurement receiving end form a Hall, eddy current, or laser sensing structure.

[0011] In one or more embodiments of the measuring device, the number of the pitch measurement receiving ends is multiple, and they are arranged on the engine stator, and the multiple pitch measurement receiving ends are symmetrically arranged.

[0012] In one or more embodiments of the measuring device, the change range of the measured distance corresponding to the working contour line of the cam does not exceed the range of the sensor.

[0013] A measuring method according to the second aspect of the present application, using the pitch angle measuring device as described in the first aspect to measure the pitch angle of the fan blade, the measuring method comprising the following steps:

[0014] Arrange the pitch adjustment rocker arm and the pitch measurement driving end;

[0015] Perform measurement to obtain the first distance, the second distance, and the theoretical measured distance of the pitch adjustment rocker arm;

[0016] Obtain the pitch angle according to the relationship between the first distance, the second distance, and the theoretical measured distance of the pitch adjustment rocker arm and the pitch angle, and the relationship is as follows:

[0017] (1)

[0018] L1 is the first distance, L2 is the second distance, is the theoretical measured distance of the pitch adjustment rocker arm.

[0019] In one or more embodiments of the measuring method, arranging the pitch adjustment rocker arm and the pitch measurement driving end includes the following steps:

[0020] Select two fan blades in completely symmetric positions, defined as the first fan blade and the second fan blade, and set the pitch adjustment measurement rocker arm at the roots of the first fan blade and the second fan blade, and set the pitch adjustment reference rocker arm at the roots of the remaining fan blades;

[0021] Set the pitch measurement drive end at the fan support hub corresponding to the first fan blade and the second fan blade. Select the third fan blade and the fourth fan blade with symmetric distribution from the remaining fan blades, and set the pitch measurement drive end at the fan support hub corresponding to the third fan blade and the fourth fan blade;

[0022] Among them, the circumferential phases of the first fan blade and the second fan blade differ by , the circumferential phases of the third fan blade and the fourth fan blade differ by , and the included angle between the line connecting the first fan blade and the second fan blade and the line connecting the third fan blade and the fourth fan blade satisfies the following formula:

[0023] (2)

[0024] In the above formula, , N is the number of fan blades, is the floor function.

[0025] In one or more embodiments of the measurement method, the sampling frequency of the pitch measurement receiving end matches the fan speed , and the sampling frequency satisfies the following formula:

[0026] (3).

[0027] In one or more embodiments of the measurement method, averaging the measurement signals at each position includes the following steps:

[0028] Assume that at different positions ( ) the signals measured by the pitch measurement receiving end at different positions ( ) at the pitch measurement receiving end are . Respectively average the measurement distance signals at the first fan blade, the second fan blade and the third fan blade, the fourth fan blade:

[0029] (4)

[0030] (5)

[0031] Average the distance signals measured by the receiving end for different pitch measurements:

[0032] (6)

[0033] (7)

[0034] Substitute formulas (4)-(7) into formula (1) to obtain the pitch angle calculation formula for the control system:

[0035] (8)

[0036] In the above formula .

[0037] In one or more embodiments of the measurement method, when the pitch measurement drive end at a certain position fails, the pitch angle calculation formula is as follows:

[0038] When the pitch measurement drive end at position a fails, the pitch angle calculation formula becomes:

[0039] (9);

[0040] When the pitch measurement drive end at position b fails, the pitch angle calculation formula becomes:

[0041] (10);

[0042] When the pitch measurement drive end at position c fails, the pitch angle calculation formula becomes:

[0043] (11);

[0044] When the pitch measurement drive end at position d fails, the pitch angle calculation formula becomes:

[0045] (12).

[0046] In one or more embodiments of the measurement method, when the pitch measurement receiving end at a certain position fails, the pitch angle is calculated based on the signals of other pitch measurement receiving ends. A total of n pitch measurement receiving ends are arranged, and the kth pitch measurement receiving end fails. The pitch angle calculation formula is:

[0047] (13);

[0048] Where , both k and n are positive integers.

[0049] The progressive effects of the present application include, but are not limited to, achieving effective pitch angle measurement by reasonably arranging the rocker arm and pitch measurement components, performing arithmetic processing on measurement signals, and avoiding introducing imbalance. Specifically, the beneficial effects include, but are not limited to, one or a combination of the following:

[0050] 1. It has a wide range of adaptability and can be paired with different types of non-contact displacement measurement sensors. Hall, eddy current, and laser non-contact displacement measurement sensors can be configured, and the receiving end of the sensor is arranged at the stator end, facilitating electrical transmission. It can also be adapted to almost all types of propeller engines and open fan engines with more than 4 blades (the fan input shaft and turbine output shaft can be coaxial or non-coaxial), and can also be adapted to different types of pitch-changing mechanisms, including hydraulic, electric, and mechanical types, without introducing additional rotor imbalance during operation and reducing the risk of engine vibration exceeding the limit;

[0051] 2. To a certain extent, the basic vibration interference can be eliminated through the Boolean operation of different sensor signals, improving the pitch angle measurement accuracy;

[0052] 3. Redundant design can be carried out for the transmission end and receiving end of the pitch measurement signal to improve reliability;

[0053] 4. By selecting appropriate lightweight materials for the angular displacement measurement mechanism, it has the characteristics of light weight and relatively simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The above and other features, properties, and advantages of the present application will become more apparent from the following description in conjunction with the drawings and embodiments. It should be noted that the drawings are only examples and are not drawn under the condition of equal scale, and should not be used to limit the actual protection scope required by the present application, where:

[0055] Figure 1 is a schematic structural diagram of a pitch angle measurement device according to an embodiment.

[0056] Figure 2A and Figure 2B is a schematic structural diagram of the rocker arm of a pitch angle measurement device according to an embodiment.

[0057] Figures 3A to 3C is a schematic diagram of different pitch measurement signals obtained by a pitch angle measurement device according to an embodiment.

[0058] Figure 4 is a schematic layout diagram of the rocker arm and pitch measurement components of a pitch angle measurement device according to an embodiment.

[0059] Figure 5 is a schematic flowchart of a pitch angle measurement method according to an embodiment.

[0060] Figure 6 It is a schematic diagram of the pitch angle measuring device and the blade of an embodiment. Specific embodiments

[0061] The following discloses various embodiments or examples for implementing the described subject technical solutions. To simplify the disclosure, specific examples of each element and arrangement are described below. Of course, these are merely examples and do not limit the protection scope of this application.

[0062] In addition, it should be understood that terms such as "an embodiment", "one embodiment", and / or "some embodiments", "one or more embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that the repeated mention of "an embodiment" or "one embodiment" or "some embodiments" or "one or more embodiments" at different positions in this specification does not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0063] As shown in the attached Figure 1 As shown, there are multiple fan blades 1 in a circle at the front end of an open fan engine (the number of blades is usually even, such as 4, 6, 8, 10, 12, etc.). Each fan blade 1 is installed on the fan support hub 2 through a fan support bearing 3. The intake cone 6 is fixed on the fan support hub 2, and the fan support hub 2 is fixedly connected to the fan input shaft / turbine output shaft 9. The input end of the variable pitch mechanism 5 is generally fixed on the fan support hub 2 or the fan input shaft / turbine output shaft 9 of the fan support. The output end of the variable pitch mechanism 5 is connected to the pitch adjustment rocker arm 4, and the pitch adjustment rocker arm 4 is fixedly connected to the root of the fan blade 1. When the variable pitch mechanism 5 operates, it drives the rocker arm to rotate around the axis of the fan support bearing 3, thereby driving the fan blade to rotate and realizing the adjustment of the pitch angle. During the pitch angle adjustment process, the pitch angle of the open fan is measured in real time through the pitch measurement drive end 7 and the pitch measurement receiving end 8, thereby realizing the closed-loop feedback control of the pitch angle.

[0064] The following introduces the principle of measuring the pitch angle of an open fan according to the solution of the embodiment.

[0065] As shown in the attached Figure 2A And Figure 2BAs shown, the pitch measurement component includes two parts: the pitch measurement drive end 7 and the pitch measurement receiving end 8. Among them, the pitch measurement drive end 7 further includes a rolling body 701, a measurement rod 702, a compression spring 703, a measurement bracket 704, and a sensor induction end 705. The measurement rod 702 drives the rolling body 701 under the action of the compression spring 703. For example, as shown in the figure, it drives the rolling body 701 to the left, making the rolling body 701 closely adhere to the pitch adjustment rocker arm 4. The pitch adjustment rocker arm 4 includes two configurations, including the pitch adjustment reference rocker arm 401 and the pitch adjustment measurement rocker arm 402. As shown in the figure, compared with the pitch adjustment reference rocker arm 401, the pitch adjustment measurement rocker arm 402 has an added cam. This cam can be integrally manufactured with the rocker arm or separately manufactured and installed on the basis of the pitch adjustment reference rocker arm 401. Due to the non-contact form of measurement, in some embodiments, the specific forms of the sensor induction end 705 and the pitch measurement receiving end 8 can be designed using non-contact distance measurement principles such as Hall, eddy current, and laser.

[0066] The pitch adjustment reference rocker arm 401 is designed to include a calibration surface with a circular hub. When the pitch adjustment reference rocker arm 401 drives the fan blade 1 to change the pitch angle, its outer hub always contacts the rolling body 701. Because the pitch adjustment reference rocker arm 401 adopts a circular hub calibration surface design, the distance L1 between the sensor induction end 705 and the pitch measurement receiving end 8 remains unchanged; when the pitch adjustment measurement rocker arm 402 drives the fan blade 1 to change the pitch angle, its outer hub always contacts the rolling body 701. Because the pitch adjustment measurement rocker arm 402 adopts a cam hub measurement surface design, the rolling body 701 drives the sensor induction end 705 to move under the drive of the cam hub measurement surface, causing the distance L2 between the sensor induction end 705 and the pitch measurement receiving end 8 to change. By comparing L1 and L2, the pitch angle of the fan moving blade can be calculated inversely. Since the difference between L2 and L1 is used as the input for pitch measurement, this measurement method can avoid pitch measurement errors caused by axial deformation or vibration of the fan support hub 2 and the pitch adjustment rocker arm 4 compared to directly measuring the pitch using L2. As Figure 3A , Figure 3B shown in the pitch adjustment actuation stroke (assuming the rocker arm rotates clockwise), there are many basic noise spikes on the two curves due to deformation and vibration. Among them represents the theoretical measurement distance of the pitch adjustment reference rocker arm 401 (the theoretical distance between the sensor induction end 705 and the pitch measurement receiving end 8 corresponding to the pitch adjustment reference rocker arm 401), which is a constant; subtracting the three curves of L2, L1, and can eliminate most of the basic noise spikes, as Figure 3C shown.

[0067] For the structural design of the cam and the measurement drive components, it is generally based on the open fan structure layout and the pitch angle adjustment range (generally not exceeding ), design the cam of the pitch adjustment measurement rocker arm 402, and select the measurement sensor. The design of the cam and the selection of the sensor generally need to ensure that the change range of the measurement distances (L1, L2) corresponding to the working profile of the cam can adapt to the effective range of the sensor.

[0068] For the layout of the rocker arm and the pitch measurement components, the pitch measurement receiving end 8 is arranged on the engine stator part, and is generally arranged in a completely symmetrical manner. Assuming that there are n sets of pitch measurement receiving ends 8 ( ), then these receiving ends are symmetrically arranged on the stator, and the spacing angle is . Assuming n = 4, as shown in Figure 6 , the spacing between the receiving ends is , and it can be considered to be arranged at the 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock positions of the engine. If the space is not enough, the positions of the receiving ends can be adjusted appropriately, or the number of receiving ends can be reduced, but at least 2 sets should be ensured, with redundant design.

[0069] The rocker arm and the pitch measurement drive end 7 are respectively matched with the fan blade 1 and the fan support hub 2, which belong to the engine rotor parts. Their layout generally needs to consider the cooperation with the fan blade, and at the same time, the rotor balance also needs to be considered. Since L1 and L2 are not consistent during the pitch adjustment process, and the centers of mass of the two rocker arms, namely the pitch adjustment reference rocker arm 401 and the pitch adjustment measurement rocker arm 402, are not consistent. If the pitch adjustment reference rocker arm 401 and the pitch adjustment measurement rocker arm 402 are symmetrically arranged (circumferentially different by ), an unbalanced couple will inevitably be generated, posing a challenge to the dynamic rotor balance of the engine.

[0070] Therefore, in some embodiments, the layout scheme of the pitch adjustment rocker arm 4 and the pitch measurement drive end 7 as shown in Figure 4 can be adopted:

[0071] Select two fan blades (points a and c in the figure) in completely symmetrical positions, and configure and install the pitch adjustment measurement rocker arm 402 at the roots of the corresponding blades, and arrange and install the pitch adjustment reference rocker arm 401 at the roots of the remaining fan blades.

[0072] Arrange and install the pitch measurement drive end 7 on the fan support hub 2 corresponding to positions a and c, and select two symmetrical position points b and d, and install the pitch measurement drive end 7 on the corresponding fan support hub 2, that is, arrange the pitch measurement drive end 7 at 4 position points.

[0073] For the position points a, b, c, and d, there are the following requirements: The circumferential phases of the position points a and c differ by ; The circumferential phase difference between position points b and d is ; The angle between the line connecting positions a and c and the line connecting position points c and d (the smaller angle, ) satisfies the following formula:

[0074] (1)

[0075] In the above formula, N is the number of open - type fan moving blades, is the floor function. For an engine with 4 fan blades, let it be ; For an engine with 6 fan blades, let it be ; For an engine with 8 fan blades, let it be ; For an engine with 12 fan blades, let it be .

[0076] In the embodiment, the scheme selects 4 position points to arrange 4 sets of pitch - measurement drive ends 7. The beneficial effects are as follows: it can more effectively eliminate the rotor unbalance couple caused by the inconsistent distances of L1 and L2 during the working process, reducing the risk of excessive engine vibration; on the other hand, it enables the measurement system to have a redundant backup function, ensuring the continuous measurement of the pitch angle when a certain pitch - measurement component fails. Since the pitch - measurement component is not stressed, in some embodiments, lightweight materials such as plastics, aluminum alloys, composite materials, etc. can be used, which can further reduce the weight of the entire measurement device.

[0077] As introduced above, referring to Figure 5 shown, the present application also provides a method for measuring the pitch angle, including the following steps:

[0078] S100. Arrange the pitch - adjustment rocker arm and the pitch - measurement drive end.

[0079] The specific arrangement method can refer to the above introduction of the structural design of the pitch - adjustment rocker arm and the arrangement position of the pitch - measurement drive end, and will not be elaborated here.

[0080] S200. Conduct measurement to obtain the first distance, the second distance, and the theoretical measurement distance of the pitch - adjustment rocker arm. As introduced above, by comparing L1 and L2, the pitch angle of the fan moving blade can be inversely calculated, and subtracting the three curves of L2, L1, and can eliminate most of the basic noise burrs.

[0081] S300. Obtain the pitch angle according to the relational formula between the first distance, the second distance, and the theoretical measurement distance of the pitch - adjustment rocker arm and the pitch angle.

[0082] The specific calculation steps may include:

[0083] S301. For pitch angle calibration, in some embodiments, the blade pitch angle can be obtained according to the cam working profile function or the actual measurement and calibration method. The functional relationships with L1 and L2 are as follows:

[0084] (2)

[0085] L1 is the first distance, and L2 is the second distance. is the theoretical measurement distance of the pitch adjustment rocker arm.

[0086] Continuing to refer to Figure 5 As shown, the calculation steps may further include: S302. Extracting and correcting the pitch measurement signal.

[0087] In some embodiments, since the induction signal of rotation is extracted, the sampling frequency of the pitch measurement receiving end 8 needs to match the open fan speed (rotating around the engine axis, unit: rpm) and the layout of the pitch measurement driving end 7. The sampling frequency (unit: Hz) requirements are as follows:

[0088] (3)

[0089] In the above formula The definition of is shown in formula (1).

[0090] In some embodiments, the measurement signals at each position can be averaged to more comprehensively reflect the overall pitch angle.

[0091] Assume that at different positions ( ) the signals measured by the pitch measurement receiving end 8 at different positions ( ) measured by the pitch measurement receiving end 8 are . To more comprehensively reflect the overall pitch angle, the measurement distance signals at a, c and b, d are averaged respectively:

[0092] (4)

[0093] (5)

[0094] The distance signals measured by different pitch measurement receiving ends 8 are averaged:

[0095] (6)

[0096] (7).

[0097] Continuing to refer to Figure 5 As shown, the calculation steps may further include: S303. Pitch angle calculation.

[0098] Continuing to refer to Figure 5 , for the pitch angle calculation, substituting formulas (4)-(7) into formula (2), the pitch angle calculation formula for the control system is obtained:

[0099] (8).

[0100] In the above formula , since the system has a redundant design, when the pitch measurement drive end 7 or the pitch measurement receiving end 8 at a certain position fails, the pitch angle can still be measured and calculated.

[0101] When the pitch measurement drive end 7 at position a fails, the pitch angle calculation formula becomes:

[0102] (9).

[0103] When the pitch measurement drive end 7 at position b fails, the pitch angle calculation formula becomes:

[0104] (10).

[0105] When the pitch measurement drive end 7 at position c fails, the pitch angle calculation formula becomes:

[0106] (11).

[0107] When the pitch measurement drive end 7 at position d fails, the pitch angle calculation formula becomes:

[0108] (12).

[0109] When the pitch measurement receiving end 8 at a certain position fails, the pitch angle is calculated based on the signals of other pitch measurement receiving ends 8. Assuming that a total of n pitch measurement receiving ends 8 are arranged, and the kth pitch measurement receiving end 8 fails, the pitch angle calculation formula becomes:

[0110] (13)

[0111] Wherein , where k and n are both positive integers.

[0112] As introduced above, the beneficial effects of the pitch angle measuring device and the measuring method for fan blades provided by the present application include, but are not limited to, one or a combination of the following:

[0113] 1. It has a wide range of adaptability and can be paired with different types of non-contact displacement measurement sensors. Hall, eddy current, and laser non-contact displacement measurement sensors can be configured, and the receiving end of the sensor is arranged at the stator end, which is easy for electrical transmission. It can also be adapted to almost all types of propeller engines and open fan engines with more than 4 blades (the fan input shaft and the turbine output shaft can be coaxial or non-coaxial), and can also be adapted to different types of pitch-changing mechanisms, including hydraulic, electric, and mechanical types, without introducing additional rotor unbalance during operation, reducing the risk of exceeding the engine vibration limit;

[0114] 2. To a certain extent, the basic vibration interference can be eliminated through the Boolean operation of different sensor signals, improving the pitch angle measurement accuracy;

[0115] 3. Redundant design can be carried out for the driving end and the receiving end of the pitch measurement signal to improve reliability;

[0116] 4. By selecting appropriate lightweight materials for the angular displacement measurement mechanism, it has the characteristics of light weight and relatively simple structure.

[0117] Although the present application is disclosed as above with the above embodiments, it is not used to limit the present application. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, any modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present application without departing from the technical solution of the present application shall fall within the protection scope defined by the claims of the present application.

Claims

1. A pitch angle measuring device for a fan blade, characterized in that The measurement device includes: A pitch measurement transmission end, including a rolling body, a measurement rod, a compression spring, and a sensor sensing end; wherein, the measurement rod can drive the rolling body under the action of the compression spring to make the rolling body closely contact the pitch adjustment rocker arm; the pitch adjustment rocker arm includes a pitch adjustment reference rocker arm and a pitch adjustment measurement rocker arm; and A pitch measurement receiving end; Wherein, the pitch adjustment reference rocker arm has a circular hub calibration surface, and the pitch adjustment measurement rocker arm has a cam hub measurement surface; When the pitch adjustment reference rocker arm is driven, the distance between the sensor sensing end and the pitch measurement receiving end is a first distance, and this first distance remains unchanged; When the pitch adjustment measurement rocker arm is driven, the rolling body drives the sensor sensing end to move, so that the distance between the pitch measurement transmission end and the pitch measurement receiving end is a second distance, and this second distance changes.

2. The measuring device according to claim 1, wherein, The sensor sensing end and the pitch measurement receiving end form a Hall, eddy current, or laser sensing structure.

3. The measuring device according to claim 2, characterized in that, The number of the pitch measurement receiving ends is multiple, and they are arranged on the engine stator, and the multiple pitch measurement receiving ends are symmetrically arranged.

4. The measuring device according to claim 2, wherein, The change range of the measurement distance corresponding to the working contour line of the cam does not exceed the range of the sensor.

5. A measurement method, characterized in that, Using the measurement device according to any one of claims 1-4 to measure the pitch angle of the fan blade, the measurement method includes the following steps: Arrange the pitch adjustment rocker arm and the pitch measurement transmission end; Perform measurement to obtain the first distance, the second distance, and the theoretical measurement distance of the pitch adjustment rocker arm; Obtain the pitch angle according to the relationship formula between the first distance, the second distance, and the theoretical measurement distance of the pitch adjustment rocker arm and the pitch angle. The relationship formula is as follows: （1） L1 is the first distance, and L2 is the second distance. It is the theoretical measurement distance of the pitch adjusting rocker arm.

6. The measuring method according to claim 5, characterized in that Arranging the pitch adjustment rocker arm and the pitch measurement transmission end includes the following steps: Select two fan blades in completely symmetric positions, defined as the first fan blade and the second fan blade, and set the pitch adjustment measurement rocker arm at the roots of the first fan blade and the second fan blade, and set the pitch adjustment reference rocker arm at the roots of the remaining fan blades; Set the pitch measurement transmission end at the fan support hubs corresponding to the first fan blade and the second fan blade, select the third fan blade and the fourth fan blade with symmetric distribution from the remaining fan blades, and set the pitch measurement transmission end at the fan support hubs corresponding to the third fan blade and the fourth fan blade; Among them, the circumferential phases of the first fan blade and the second fan blade differ by , the circumferential phases of the third fan blade and the fourth fan blade differ by , and the angle between the line connecting the first fan blade and the second fan blade and the line connecting the third fan blade and the fourth fan blade satisfies the following formula: （2） In the above formula, , N is the number of fan blades, is the floor function.

7. The measuring method according to claim 6, wherein, The sampling frequency of the pitch measurement receiving end matches the fan speed , the sampling frequency satisfies the following formula: （3）。 8. The measurement method according to claim 7, wherein, Averaging the measurement signals at each position, including the following steps: Assume different positions ( ) The pitch measurement receiver at a different position measures different positions ( ) The signal of the pitch measurement receiver at the position is , and the measured distance signals at the first fan blade, the second fan blade, the third fan blade, and the fourth fan blade are averaged respectively: （4） （5） Average the distance signals measured by different pitch measurement receiving ends: （6） （7） Substitute formulas (4)-(7) into formula (1) to obtain the calculation formula for the pitch angle of the control system: （8） In the above formula .

9. The measuring method according to claim 8, characterized in that When the pitch measurement transmission end at a certain position fails, the pitch angle calculation formula is as follows: When the pitch measurement transmission end at position a fails, the pitch angle calculation formula becomes: （9）； When the pitch measurement transmission end at position b fails, the pitch angle calculation formula becomes: （10）； When the pitch measurement transmission end at position c fails, the pitch angle calculation formula becomes: （11）； When the pitch measurement transmission end at position d fails, the pitch angle calculation formula becomes: （12）。 10. The measuring method according to claim 8, characterized in that, When the pitch measurement receiver at a certain position fails, the pitch angle is calculated based on the signals of other pitch measurement receivers. A total of n pitch measurement receivers are arranged. When the k-th pitch measurement receiver fails, the pitch angle calculation formula is as follows: （13）； where , both k and n are positive integers.

Images