Complex shape blade profile characteristic test system and test method thereof

Abstract

The invention provides a complex profile blade profile characteristic test system and a test method thereof.The test system comprises a measuring device, a screw rod sliding table device, a blade root clamping device, a loading device and a framework, one end of a blade to be tested is installed at the top of the framework through the blade root clamping device, and the other end of the blade to be tested is connected with the loading device; the measuring device is installed on the side portion of the frame through the lead screw sliding table device. And the paddle root clamping device is matched with the loading device to realize loading in the flapping, shimmy and torsion directions of the paddle. According to the invention, distributed measurement of deformation displacement under blade waving, shimmy and torsional load can be realized, and distribution of blade section waving, shimmy and torsional rigidity can be analyzed and determined. Strain sensors do not need to be pasted on the blades, laser is used for non-contact measurement, the lead screw sliding table is used for accurately controlling measurement points, the test preparation time is greatly shortened, the influence of human factors is avoided, and the method has the advantages of being easy to operate, good in repeatability and high in measurement precision.

Description

Technical Field

[0001] The invention relates to the technical field of helicopter blade measurement, in particular to a complex-shaped blade profile characteristic testing system and a testing method thereof. Background Art

[0002] The rotor blade is the core component of the helicopter. The dynamic characteristics of the blade directly determine the performance of the helicopter, such as vibration level, aeroelastic stability and structural fatigue. The design of the blade dynamic characteristics is a key link in the design of helicopter blades. In order to accurately calculate the dynamic characteristics of the blade, it is necessary to accurately measure the distribution of the profile stiffness of the helicopter blade in the flapping, swing and torsion directions along the span of the blade. In the design of helicopters, it is an indispensable and important link to measure the profile characteristics of manufactured blades. The measurement data can not only be used to confirm the gap between the design stiffness and the actual stiffness, but also provide input data for the aeroelastic dynamics analysis of helicopters to ensure the validity of the analysis results.

[0003] Traditional helicopter blade profile characteristic measurement technology measures the strain distribution of the blade under different loads by pasting resistance strain gauges or fiber grating sensors at different positions on the blade surface. The pasting and loading processes are cumbersome, the pre-test preparation work is large, and the post-test cleaning is difficult.

[0004] The new generation of rotor blades mostly adopts complex shapes such as swept back and reversed single or double folds to improve the rotor aerodynamic performance and reduce the noise level. However, the complex geometric shape makes the tip load applied when measuring the blade profile characteristics produce obvious bending-torsion coupling deformation on the inner side of the blade profile, and more sensors need to be arranged to measure the distribution of blade deformation, which greatly increases the difficulty of testing. Therefore, a test method and test system are urgently needed to achieve high-precision and efficient measurement of complex blade profile characteristics. Summary of the invention

[0005] In order to solve the problems of the prior art, the present invention provides a complex-shaped blade profile characteristic testing system and a testing method thereof, so as to achieve non-contact, high-precision and efficient measurement of the blade profile characteristics.

[0006] The present invention provides a complex-shaped blade profile characteristic testing system, comprising a measuring device, a screw slide device, a blade root clamping device, a loading device and a frame, wherein one end of the blade to be tested is mounted on the top of the frame through the blade root clamping device, and the other end is connected to the loading device, and the measuring device is mounted on the side of the frame through the screw slide device;

[0007] The measuring device comprises a laser Doppler vibrometer and a fixing box, wherein the fixing box is connected to a screw slide device and can slide vertically and horizontally through the horizontal screw slide device and align with the loading device;

[0008] The frame includes a column and a supporting frame located on the top of the column, and a blade root clamping device is fixed to the supporting frame; a short pulley rod and a long pulley rod are arranged between the columns, and the loading device includes a blade clamp, a pulley and a weight, and the pulley is respectively connected to the short pulley rod and the long pulley rod of the frame, and the blade clamp, pulley and weight are connected by a thin wire.

[0009] Further improvement, the screw slide device includes a transverse screw slide device and two vertical screw slide devices, wherein the vertical screw slide device is fixed to the frame through a fixing plate, the transverse screw slide device is connected to the vertical screw slide device and slides vertically along the vertical screw slide device, and the measuring device is connected to the transverse screw slide device and slides laterally along the transverse screw slide device. The transverse screw slide device and the vertical screw slide device both include a bearing seat, a fixing plate, a screw, a screw slider, a coupling and a stepper motor, wherein the vertical screw slide device is fixed to the frame through a fixing plate, and the transverse screw slide device is fixed to the screw slider of the vertical screw slide device through a fixing plate.

[0010] As a further improvement, the propeller root clamping device includes a heel clamp, a hole for fixing to the helicopter blade is provided at the bottom of the heel clamp, and a groove parallel to the blade chord when the blade is clamped is provided at the top of the heel clamp for confirming the degree of the dial.

[0011] The present invention also provides a method for testing a complex-shaped blade profile characteristic testing system, using the above-mentioned complex-shaped blade profile characteristic testing system, including three testing methods for measuring blade flapping bending stiffness distribution, measuring blade swing bending stiffness distribution, and measuring blade torsional stiffness distribution;

[0012] When measuring the distribution of blade flapping bending stiffness, the dial in the blade root clamping device is used to make the upper surface of the blade face the laser Doppler vibrometer. When there is no load and when there is a load in the flapping direction, the stepper motor is controlled to move the measuring point of the laser Doppler vibrometer from the blade root to the blade tip along the blade pitch axis. The distribution of the distance between the blade pitch axis and the laser Doppler vibrometer before and after loading along the blade span direction is measured to determine the deflection distribution in the blade flapping direction, and the flapping stiffness of different blade sections is calculated by the following formula:

[0013]

[0014] Where, F is the concentrated load in the flapping direction, L is the spanwise position of the concentrated load on the blade, w1 is the flapping deflection of the micro-segment with the endpoint position x1, and w2 is the flapping deflection of the micro-segment with the endpoint position x2;

[0015] When measuring the blade shimmy bending stiffness distribution, the dial in the blade root clamping device is used to make the leading edge line of the blade face the laser Doppler vibrometer. When there is no load and when there is a load in the shimmy direction, the stepper motor is controlled to measure the distribution of the distance between the leading edge line of the blade and the laser Doppler vibrometer along the blade span before and after loading, and the deflection distribution in the shimmy direction of the blade is determined. The shimmy stiffness of different sections of the blade is determined using the above formula.

[0016] When measuring the torsional stiffness distribution of the blade, the dial in the blade root clamping device is used to make the upper surface of the blade face the laser Doppler vibrometer. When the torque load is not loaded and loaded, the stepper motor is controlled to move the measuring point of the laser Doppler vibrometer from the blade root to the blade tip along the leading edge line and the trailing edge line of the blade respectively. The distribution of the distance between the leading edge line and the trailing edge line of the blade and the laser Doppler vibrometer along the span direction of the blade is measured before and after loading. The distribution of the blade torsion angle along the span direction is determined according to the following formula:

[0017]

[0018] In the formula, and z L (x), z T (x), the distances from the leading edge line and the trailing edge line to the laser Doppler vibrometer before and after loading, c is the blade chord length, and the torsional stiffness of different blade sections is calculated by the following formula:

[0019]

[0020] Where m is the weight of a single weight that applies torque, φ1 is the torsion angle of the micro-segment with the endpoint position x1, and φ2 is the torsion angle of the micro-segment with the endpoint position x2.

[0021] The beneficial effects of the present invention are:

[0022] 1. The complex-shaped blade profile characteristic testing system described in the present invention realizes non-contact, high-precision measurement of blade deformation displacement through laser technology, simplifies test preparation time, and greatly improves the efficiency of blade profile characteristic measurement.

[0023] 2. The present invention uses a motor-driven screw slide device to achieve rapid positioning and precise movement of the laser Doppler vibrometer in the vertical plane of the measuring device. The operation is simple, the influence of human factors is reduced, and the test repeatability is good. By defining the motion path of the laser rangefinder, the distributed measurement of the deformation displacement of the blade with complex shape can be achieved, and the profile characteristics of its flapping, shimmying and torsion direction can be determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a schematic diagram of a complex blade profile characteristic test system;

[0026] Figure 2 is a schematic diagram of the measuring device;

[0027] Figure 3 It is a schematic diagram of the screw slide device;

[0028] Figure 4 This is a schematic diagram of the blade root clamping device;

[0029] Figure 5 is a schematic diagram of the loading device;

[0030] Figure 6 It is a schematic diagram of the framework;

[0031] Among them, 1-measuring device, 2-screw slide device, 3-propeller root clamping device, 4-loading device, 5-frame, 6-laser Doppler vibrometer, 7-fixing box, 8-vertical screw bearing seat, 9-vertical screw fixing plate, 10-vertical screw, 11-vertical screw slider, 12-vertical screw coupling, 13-vertical screw stepper motor, 14-transverse screw bearing seat, 15-transverse screw fixing plate, 16-transverse screw, 17-transverse screw coupling, 18-transverse screw stepper motor, 19-transverse screw slider, 20-propeller root clamp, 21-dial, 22-blade clamp, 23-pulley, 24-weight, 25-support frame, 26-short pulley rod, 27-long pulley rod, 28-second long pulley rod, 29-second short pulley rod. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a complex blade profile characteristic testing system. Figures 1 to 6As shown, it includes a measuring device 1, a screw slide device 2, a blade root clamping device 3, a loading device 4 and a frame 5.

[0035] The measuring device comprises a laser Doppler vibrometer 6 and a fixing box 7. The fixing box 7 is fixed to the transverse screw slider 19 by bolts through two holes at the upper end.

[0036] The screw slide device includes two vertical screw slide devices and a transverse screw slide device. The vertical screw slide device includes a vertical screw bearing seat 8, a vertical screw fixing plate 9, a vertical screw 10, a vertical screw slider 11, a vertical screw coupling 12 and a vertical screw stepper motor 13. The transverse screw slide device includes a transverse screw bearing seat 14, a transverse screw fixing plate 15, a transverse screw 16, a transverse screw coupling 17, a transverse screw stepper motor 18 and a transverse screw slider 19. The vertical screw slide device is fixed to the support frame 25 through the vertical screw fixing plate 9, and the transverse screw slide device is fixed to the vertical screw slider 11 through the transverse screw fixing plate 15.

[0037] The blade root clamping device comprises a blade root clamp 20 and a dial 21. The dial 21 is fixed on a support frame 25 through four through holes thereof for confirming the installation angle.

[0038] The loading device comprises a blade fixture 22, a pulley 23 and a weight 24. The blade fixture 23 is fixed to the tip of the blade to be tested. The blade fixture 22, the pulley 23 and the weight 24 are connected by a thin wire.

[0039] The frame includes a support frame 25, a short pulley rod 26 and a second short pulley rod 29, a long pulley rod 27 and a second long pulley rod 28. The support frame 25 is connected to the blade root clamping device by bolts in the center of the support frame. The short pulley rod 26 and the second short pulley rod 29 and the long pulley rod 27 and the second long pulley rod 28 are used to fix the pulleys.

[0040] Furthermore, the screw and bearing seat of the vertical and transverse screw slide devices are fixed in the bearing seat, and the screw and the stepper motor are connected through a coupling. The rotation of the stepper motor will drive the screw to rotate, and the stepper motors of the transverse screw slide device and the two vertical screw slide devices cooperate with each other to realize the horizontal and vertical movement of the measuring point of the laser Doppler vibrometer 6 fixed on the transverse screw slider 19.

[0041] Furthermore, the propeller root clamp 20 in the propeller root clamping device is fixed to the propeller blade through two holes at the bottom, and has a groove at the top that is parallel to the propeller blade chord when the propeller blade is clamped, which is used to confirm the degree of the dial.

[0042] Furthermore, the pulley 23 can be connected to the short pulley rod 26 and the second short pulley rod 29 and the long pulley rod 27 and the second long pulley rod 28 of the support frame 25 respectively, and cooperate with the blade root clamping device 3 to realize loading on the blade in the flapping, swinging and torsional directions.

[0043] Example 2

[0044] This embodiment provides a specific method for measuring the distribution of blade bending stiffness in flapping and swing directions using a complex-shaped blade profile characteristic testing system. The blade flapping bending stiffness is measured according to the following steps.

[0045] Step 1: Align the mounting hole at the root of the blade to be tested with the mounting hole of the blade root fixture, fix it with bolts, and fix it to the support frame, so that the dial of the blade root clamp is at 0 degrees, that is, the upper surface of the blade faces the laser Doppler vibrometer;

[0046] Step 2: Start the stepper motors on the vertical and transverse screw slides, so that the transverse screw slides drive the laser Doppler vibrometer to move, so that the laser emitted by the laser Doppler vibrometer is aligned with the pitch axis position of the blade root section;

[0047] Step 3: When the blade is not loaded, start the laser Doppler vibrometer to start recording data. Use the stepper motor to control the laser Doppler vibrometer to move along the blade pitch axis toward the blade tip at a certain speed, and record the distance between the blade pitch axis and the laser Doppler vibrometer when there is no load.

[0048] Step 4: Use a stepper motor to return the laser Doppler vibrometer to the starting point of step 2, arrange the pulley on the short pulley rod 26, add weights to the loading device, and make the helicopter blade bend and deform in the swinging direction;

[0049] Step 5: Control the laser Doppler vibrometer by the stepper motor to move downward along the blade pitch axis at a certain speed under loading, and record the distance between the blade pitch axis and the laser Doppler vibrometer under loading;

[0050] Step 6: Repeat steps 4 and 5 to record the distance between the blade pitch axis and the laser Doppler vibrometer under different weights;

[0051] Step 7: Remove the blade fixture and remove the helicopter blades for data processing:

[0052] Since the blade is a slender beam structure, the displacement in the blade flapping direction is much greater than the displacement in the blade tensile direction, so the deformation displacement in the tensile direction of the blade section under the blade loading state is ignored. Subtract the distance between the laser Doppler vibrometer and the blade pitch axis under the loading state measured in step 5 from the result measured in the unloaded state in step 3 to obtain the bending deflection distribution function w(x) of the blade pitch axis under the bending load in the flapping direction. Assume the blade to be a cantilever beam whose bending stiffness varies along the span direction. According to the knowledge of material mechanics, the following relationship exists between the bending moment M and the deflection w of the beam under the bending state:

[0053]

[0054] Among them, EI y is the blade flapping bending stiffness. When a concentrated load F is applied at the end of the beam at x = L, the bending moment at this time is distributed along the span of the beam as M(x) = F(Lx). Take one of the micro-segments, with the span positions of the two ends being x1 and x2 respectively. Assuming that the flapping bending stiffness of this segment does not change, perform a second integration of w” in the interval [x1, x2] to obtain the deflection increment of the micro-segment:

[0055]

[0056] The flapping bending stiffness of the blade section is obtained as follows:

[0057]

[0058] The blade is divided into multiple micro-segments (greater than 10), and the distribution of blade flapping bending stiffness is calculated using the above formula using the measured deflections on both sides of the micro-segments starting from the root of the blade. The blade flapping bending stiffness under different loads is calculated, and the distribution of blade flapping bending stiffness can be obtained by taking the average value.

[0059] When using a complex blade profile characteristic test system to measure the blade swing direction stiffness distribution, the blade installation position needs to be adjusted. Adjust step one so that when the blade is fixed to the support frame through the blade root clamp, the dial of the blade root clamp is at 90 degrees, that is, the leading edge of the blade faces the laser Doppler vibrometer; and during the measurement process, the laser Doppler vibrometer measures the spatial position of the leading edge line at different profile positions. The remaining implementation steps are the same, and the distribution of the blade swing bending stiffness can be determined in the end.

[0060] Embodiment 3:

[0061] This embodiment provides a specific method for measuring the torsional stiffness distribution of a blade using a complex-shaped blade profile characteristic test system. The method for measuring the torsional stiffness distribution of a blade using a complex-shaped blade profile characteristic test system based on a laser Doppler vibrometer is quite different from the method for measuring the stiffness in the flapping and swinging bending directions, and the measurement is performed in the following steps.

[0062] Step 1: Align the mounting hole at the root of the blade to be tested with the mounting hole of the blade root fixture, fix it with bolts, and fix it to the support frame, so that the dial of the blade root clamp is at 0 degrees, that is, the upper surface of the blade faces the laser Doppler vibrometer;

[0063] Step 2: Start the stepper motors on the vertical and transverse screw slides, so that the transverse screw slide drives the laser Doppler vibrometer to move, so that the laser emitted by the laser Doppler vibrometer is aligned with the leading edge line of the blade root section;

[0064] Step 3: When the blade is not loaded, start the laser Doppler vibrometer to start recording data. Use the stepper motor to control the laser Doppler vibrometer to move along the leading edge of the blade toward the blade tip at a certain speed, and record the distance between the leading edge of the blade and the laser Doppler vibrometer when there is no load.

[0065] Step 4: Start the stepper motors of the vertical and transverse screw slides, so that the transverse screw slide drives the laser Doppler vibrometer to move, and align the laser emitted by the laser Doppler vibrometer with the trailing edge line of the blade root section;

[0066] Step 5: When the blade is not loaded, start the laser Doppler vibrometer to start recording data. The laser Doppler vibrometer is controlled by the stepper motor to move along the trailing edge line of the blade toward the blade tip at a certain speed, and the distance between the trailing edge line of the blade and the laser Doppler vibrometer when there is no load is recorded.

[0067] Step 6: Use a stepper motor to return the laser Doppler vibrometer to the starting point of step 2, arrange two pulleys on the short pulley rod 26 and the short pulley rod 27 respectively, and add weights with a weight of m to the loading device respectively, so that the helicopter blades produce bending deformation in the torsional direction;

[0068] Step 7: Control the laser Doppler vibrometer by the stepper motor to move downward along the leading edge line and the trailing edge line of the blade at a certain speed under loading, and record the distance between the leading edge line and the trailing edge line of the blade under loading and the laser Doppler vibrometer;

[0069] Step 8: Repeat steps 6 and 7 to record the distribution of the distances between the leading and trailing edge lines and the laser Doppler vibrometer after the blades are deformed in the torsional direction under different weights;

[0070] Step 9: Remove the blade fixture and remove the helicopter blades for data processing:

[0071] Since the blade is a slender beam structure, the distance distribution between the leading edge line and the trailing edge line of the blade under the loading state measured by the laser Doppler vibrometer in step 7 is recorded as z L (x) and z T (x), the distance distribution between the leading edge line and the trailing edge line in the unloaded state in step 3 and step 5 and The distribution function φ(x) of blade torsional deformation can be obtained as follows:

[0072]

[0073] Where c is the blade chord length.

[0074] Assume the blade to be a cantilever beam with varying torsional stiffness along the span direction. According to the knowledge of material mechanics, the torque T and torsional deformation φ(x) of the beam in torsion state have the following relationship:

[0075]

[0076] Where GJ is the torsional stiffness of the blade. When a torque T is applied at the end of the beam at x = L, take out one of the micro-segments, whose spanwise positions are x1 and x2 respectively. Assuming that the torsional stiffness of the segment does not change, integrate φ' in the interval [x1, x2] to obtain the torsional angle increment of the micro-segment:

[0077]

[0078] There is also a torque T = mc, so the torsional stiffness of this section of the blade is:

[0079]

[0080] The blade is divided into multiple micro-segments (greater than 10), and the distribution of the blade torsional bending stiffness is calculated using the above formula using the measured torsional angles on both sides of the micro-segment starting from the root of the blade. The blade torsional bending stiffness under different torsional loads is calculated, and the average value is taken to obtain the distribution of the blade torsional stiffness.

[0081] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

[0082] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, the above is only a preferred embodiment of the present invention. Since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field is within the technical scope disclosed by the present invention. For ordinary technicians in the technical field, changes or replacements that can be easily thought of should be covered within the protection scope of the present invention without departing from the principle of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A complex blade profile characteristics testing system, characterized by: It includes a measuring device, a screw slide device, a blade root clamping device, a loading device and a frame. One end of the blade to be measured is installed on the top of the frame through the blade root clamping device, and the other end is connected to the loading device. The measuring device is installed on the side of the frame through the screw slide device. The measuring device comprises a laser Doppler vibrometer and a fixing box, wherein the fixing box is connected to a screw slide device and can slide vertically and horizontally through the horizontal screw slide device and align with the loading device; The frame includes a column and a supporting frame located on the top of the column, and a blade root clamping device is fixed to the supporting frame; a short pulley rod and a long pulley rod are arranged between the columns, and the loading device includes a blade clamp, a pulley and a weight, and the pulley is respectively connected to the short pulley rod and the long pulley rod of the frame, and the blade clamp, pulley and weight are connected by a thin wire.

2. A complex-shaped blade profile characteristic testing system according to claim 1, characterized in that: The screw slide device includes a transverse screw slide device and two vertical screw slide devices, wherein the vertical screw slide device is fixed to the frame through a fixing plate, the transverse screw slide device is connected to the vertical screw slide device and slides vertically along the vertical screw slide device, and the measuring device is connected to the transverse screw slide device and slides laterally along the transverse screw slide device.

3. A complex-shaped blade profile characteristic testing system according to claim 2, characterized in that: The transverse screw slide device and the vertical screw slide device both include a bearing seat, a fixed plate, a screw, a screw slider, a coupling and a stepper motor, wherein the vertical screw slide device is fixed to the frame through a fixed plate, and the transverse screw slide device is fixed to the screw slider of the vertical screw slide device through a fixed plate.

4. A complex-shaped blade profile characteristic testing system according to claim 1, characterized in that: The blade root clamping device includes a blade heel clamp, a hole for fixing the blade to the helicopter blade is provided below the blade heel clamp, and a groove parallel to the blade chord when the blade is clamped is provided at the top of the blade heel clamp for confirming the degree of the dial.

5. A method for testing a complex-shaped blade profile characteristic testing system, using a complex-shaped blade profile characteristic testing system as claimed in any one of claims 1 to 4, characterized in that: It includes three test methods: measuring the blade flapping bending stiffness distribution, measuring the blade swing bending stiffness distribution and measuring the blade torsional stiffness distribution; When measuring the distribution of blade flapping bending stiffness, the dial in the blade root clamping device is used to make the upper surface of the blade face the laser Doppler vibrometer. When there is no load and when there is a load in the flapping direction, the stepper motor is controlled to move the measuring point of the laser Doppler vibrometer from the blade root to the blade tip along the blade pitch axis. The distribution of the distance between the blade pitch axis and the laser Doppler vibrometer before and after loading along the blade span direction is measured to determine the deflection distribution in the blade flapping direction, and the flapping stiffness of different blade sections is calculated by the following formula: Where, F is the concentrated load in the flapping direction, L is the spanwise position of the concentrated load on the blade, w1 is the flapping deflection of the micro-segment with the endpoint position x1, and w2 is the flapping deflection of the micro-segment with the endpoint position x2; When measuring the blade shimmy bending stiffness distribution, the dial in the blade root clamping device is used to make the leading edge line of the blade face the laser Doppler vibrometer. When there is no load and when there is a load in the shimmy direction, the stepper motor is controlled to measure the distribution of the distance between the leading edge line of the blade and the laser Doppler vibrometer along the blade span before and after loading, and the deflection distribution in the shimmy direction of the blade is determined. The shimmy stiffness of different sections of the blade is determined using the above formula. When measuring the torsional stiffness distribution of the blade, the dial in the blade root clamping device is used to make the upper surface of the blade face the laser Doppler vibrometer. When the torque load is not loaded and loaded, the stepper motor is controlled to move the measuring point of the laser Doppler vibrometer from the blade root to the blade tip along the leading edge line and the trailing edge line of the blade respectively. The distribution of the distance between the leading edge line and the trailing edge line of the blade and the laser Doppler vibrometer along the span direction of the blade is measured before and after loading. The distribution of the blade torsion angle along the span direction is determined according to the following formula: In the formula, and z L (x), z T (x), the distances from the leading edge line and the trailing edge line to the laser Doppler vibrometer before and after loading, c is the blade chord length, and the torsional stiffness of different blade sections is calculated by the following formula: Where m is the weight of a single weight that applies torque, φ1 is the torsion angle of the micro-segment with the endpoint position x1, and φ2 is the torsion angle of the micro-segment with the endpoint position x2.

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