Helicopter rotor cone detection system and method based on position sensitive detector

Abstract

The invention relates to the technical field of helicopter rotor detection. The invention provides a helicopter rotor cone detection system and method based on a position sensitive detector. The system comprises a dynamic balance analyzer, an imaging system, a position sensitive detector and a rotating speed sensor, the imaging system is used for imaging a blade tip on a light sensing surface of the position sensitive detector; the position sensitive detector is used for realizing photoelectric conversion and generating an electric signal which can be used for determining the imaging position of the blade tip edge on a photosensitive surface; the dynamic balance analyzer is used for calculating the imaging position of the blade tip on the photosensitive surface according to the electric signal, calculating the common taper of the rotor blade according to the related geometric parameters of the imaging system, and calculating the shimmy of the helicopter rotor according to the electric signal; and the rotating speed sensor is used for providing an electric pulse signal generated when the reference blade passes through so as to determine the corresponding relation between the shimmy and the common taper and each blade. According to the system provided by the invention, the detection efficiency is improved, and the installation requirement is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of helicopter rotor detection technology, and in particular to a helicopter rotor vertebra detection system and method based on a position sensitive detector. Background Art

[0002] One of the routine maintenance tasks for helicopters is to inspect the rotor cone. Inspection items include: common taper and blade swing amplitude. Common taper refers to whether the blades are on the same cone surface. Its inspection is generally marked by the vertical height difference between the blade tips; the blade swing amplitude refers to whether the angle between the blades deviates from the design angle. The blade swing amplitude is marked in angular units or in length units. The conversion relationship between them is that the swing length is equal to the swing angle (radian) multiplied by the rotor radius. If the blades are not on the same cone surface, due to the different lift of each blade, its aerodynamic effect will cause vibration of the helicopter. The swing of each blade is also related to the vibration of the helicopter. This not only reduces the comfort of the crew, but also poses a safety risk.

[0003] Currently, rotor cone inspection methods include strobe lights and universal track devices. These devices are used as components of helicopter dynamic balance analyzers to inspect helicopter rotor cones. The strobe light method requires mounting a reflective target with a blade number on each blade. Using the rotational speed signal provided by the dynamic balance analyzer, a flash is generated when each blade passes in the direction of the flash directed by the strobe light, creating a stable image of all blade targets aligned in the air. The height of each target is visually observed, and the blade co-taper is then adjusted by adjusting the pitch lever of the corresponding blade. However, strobe lights cannot measure blade swing amplitude. Universal track devices use triangulation to measure rotor trajectory. While this device can simultaneously measure blade co-taper and swing amplitude, before using the universal track device to measure blade co-taper, it must ensure that the angles formed by the device's two photodetectors with the shaft axis are equal. Errors in these angles significantly impact the measurement results, resulting in strict requirements for the device's geometrical mounting position.

[0004] A position-sensitive detector is a photoelectric device based on the lateral photoelectric effect that can detect the center of gravity of a light spot on a photosensitive surface. When a light spot strikes the photosensitive surface, the electrical signals generated by its multiple output motors are processed by subsequent circuitry to determine the location of the center of gravity of the light spot on the photosensitive surface. Summary of the Invention

[0005] The purpose of the present invention is to solve the defects of the above-mentioned prior art and provide a helicopter rotor cone detection system and method based on a position sensitive detector to solve the shortcomings of the prior art strobe light method that requires the installation of a target and cannot detect vibration.

[0006] The present invention adopts the following technical solutions:

[0007] Helicopter rotor cone detection system based on position sensitive detector, including:

[0008] Dynamic balance analyzer, rotor cone sensing device, speed sensor; wherein the rotor cone sensing device includes: imaging system, position sensitive detector;

[0009] The imaging system is used to image the blade tip onto the photosensitive surface of the position sensitive detector;

[0010] The position-sensitive detector is used to perform photoelectric conversion and output an electrical signal. When the blade passes through the optical axis of the imaging system, this electrical signal can directly indicate the center of gravity of the illuminated portion of the photosensitive surface, thereby indirectly inferring the position of the blade tip edge on the photosensitive surface. The principle is as follows: when the imaging system is aimed at the tip of the blade, the image formed by it will inevitably divide the photosensitive surface into two light and dark areas. Under the condition of uniform illumination, the imaging position of the edge of the blade tip on the photosensitive surface can be determined according to the center of gravity position of the illuminated part of the photosensitive surface. The distance between the imaging position and the end point of the photosensitive surface on the bright side should be twice the distance between the center of gravity position of the illuminated part and the end point of the photosensitive surface on the bright side. During the continuous rotation of the rotor, the photosensitive surface of the position-sensitive detector is in a fully illuminated state for most of the time, and is in a partially illuminated state only when the blade passes through the optical axis of the imaging system. Therefore, the electrical signal generated by the position-sensitive detector is also in the form of a pulse, and the moment when the pulse appears corresponds to the moment when the blade passes through the optical axis of the imaging system. Therefore, the position-sensitive detector is also used to generate a pulse electrical signal, which is provided to the dynamic balancing analyzer to determine the moment when the blade passes through the optical axis of the imaging system.

[0011] The rotor cone sensing device is placed at a preset angle so that the optical axis of the imaging system intersects the rotor rotation axis, and when the blade rotates, the image of the blade tip edge formed by the imaging system falls on the photosensitive surface of the position sensitive detector;

[0012] The rotation speed sensor is used to generate an electrical pulse signal when the reference blade passes through the sensor to provide a time reference;

[0013] The dynamic balancing analyzer is configured to calculate the imaging position of the blade tip edge on the photosensitive surface based on the electrical signal output by the position sensitive detector, and calculate the relative height between the blade tips, i.e., the rotor common taper, based on the imaging position and the geometric relationship between the blade tip, the optical center of the imaging system, and the photosensitive surface of the position sensitive detector in the imaging system;

[0014] The dynamic balancing analyzer is further configured to determine the time when each blade crosses the optical axis of the imaging system based on the time when the pulse of the electrical signal output by the position sensitive detector appears; and to obtain the opening angle of adjacent blades based on the time it takes for the rotor to rotate one circle and the time it takes for two adjacent blades to pass through the optical axis of the imaging system; and to obtain the shimmy of each rotor blade by subtracting the design value of the opening angle from the measured adjacent blade angle;

[0015] The dynamic balancing analyzer is further used to determine the corresponding relationship between the blade common taper and the swing array and each blade based on the electrical pulse signal generated by the speed sensor, the installation position of the speed sensor, and the orientation of the optical axis of the imaging system.

[0016] The present invention also provides a method for detecting a helicopter rotor cone based on a position sensitive detector, comprising:

[0017] When the helicopter rotor is operating at a rated speed, the position of each blade tip edge imaged on the photosensitive surface of the position sensitive detector by the imaging system is obtained based on the electrical signal generated by the position sensitive detector, as well as the time when each blade passes through the optical axis of the imaging system;

[0018] Based on the imaging position of the blade tip edge on the photosensitive surface and the optical geometric relationship between the blade tip, the optical center of the imaging system, and the photosensitive surface of the position sensitive detector in the imaging system, the relative height Δh between two adjacent blade tips is calculated using the following formula:

[0019]

[0020] Wherein, d is the distance between the optical center of the imaging system and the photosensitive surface; L is the horizontal distance between the optical center of the imaging system and the tip of the blade; α is the angle between the optical axis of the imaging system and the horizontal direction; d1 is the distance from the position where the tip edge of a blade is imaged on the photosensitive surface to the edge of the photosensitive surface; d2 is the distance from the position where the tip edge of a blade adjacent to the above-mentioned blade is imaged on the photosensitive surface to the edge of the photosensitive surface.

[0021] The angle between two adjacent blades is determined based on the moment when the blade tip passes through the optical axis of the imaging system. This is achieved by determining the moment when the blade tip passes through the optical axis of the imaging system based on the rising or falling edge of the pulsed electrical signal output by the position-sensitive detector. The angle between two adjacent blades is easily determined based on the total time it takes for the rotor to rotate once and the time difference between adjacent blades passing through the optical axis of the imaging system. The error angle between the two adjacent blades, measured based on the time difference, is subtracted from the designed angle between the two blades. The rotor's swing is calculated as the error angle. The swing array expressed in degrees can also be converted to length. The relationship is: the swing expressed in length is equal to the swing expressed in degrees (radians) multiplied by the rotor radius.

[0022] Based on the electrical pulse signals provided by the speed sensor, the corresponding relationship between the co-taper and the wobble of the helicopter blades and each blade is determined. This is achieved by determining, based on the speed sensor's installation position and the orientation of the imaging system's optical axis, which blade first crosses the imaging system's optical axis when the speed sensor generates a trigger signal when a reference blade passes over it. The reference blade is a special blade on the rotor, such as the only blade covered with reflective tape, which is the only one that passes over the speed sensor to generate a trigger signal. Therefore, the corresponding relationship between the acquired rotor co-taper and wobble and each blade can be determined based on the order in which the blades cross the imaging system's optical axis.

[0023] The rotor taper and shimmy are measured continuously for multiple revolutions of the rotor, and the average value is taken as the final measurement result of the rotor taper and shimmy for helicopter rotor cone inspection.

[0024] Beneficial effects of the present invention: After placing the rotor cone sensing device at a preset angle, the present invention determines the relative vertical height between each blade tip, that is, the common taper, by obtaining the imaging position of the blade tip on the photosensitive surface, and the optical geometric relationship between the blade tip, the optical center of the imaging system, and the photosensitive surface of the position sensitive detector in the imaging system; and determines the swing of each rotor blade by obtaining the moment when the blade passes through the optical axis of the imaging system and the time it takes for the rotor to rotate one circle. On the one hand, this method avoids the high requirement of the universal track device that the two photodetectors must be precisely installed at a preset angle, and further avoids the measurement error caused by the deviation of the installation angle of the universal track device in the horizontal direction, thereby improving the measurement accuracy; on the other hand, compared with the strobe light, it avoids the trouble of installing a target to measure the common taper, thereby improving the measurement efficiency. At the same time, the system provided by the present invention can simultaneously measure the common taper and the swing of the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is a structural schematic diagram of a helicopter rotor cone detection system based on a position sensitive detector provided by the present invention.

[0026] Figure 2 This is a schematic diagram of the geometric relationship between the rotor cone sensor device provided by the present invention and the helicopter blade.

[0027] In the figure: 1- rotor cone sensor device, 2- dynamic balance analyzer, 3- speed sensor, 4- helicopter rotor shaft, 5- blade;

[0028] 11-imaging system, 12-position sensitive detector;

[0029] 31-Optical axis of imaging system. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] like Figure 1 、 Figure 2 As shown, the helicopter rotor cone detection system based on position sensitive detector of the present invention includes: rotor cone sensing device 1, dynamic balance analyzer 2, and speed sensor 3. The rotor cone sensing device 1 includes: imaging system 11 and position sensitive detector 12.

[0032] The imaging system 11 is configured to image the blade tip on the photosensitive surface of a position-sensitive detector 12. The position-sensitive detector 12 is configured to perform photoelectric conversion and output an electrical signal that identifies the imaging position of the blade tip edge on the photosensitive surface. The position-sensitive detector 12 is also configured to generate an electrical pulse signal when the blade tip passes through the optical axis 31 of the imaging system. The rotor cone sensor device 1 is positioned at a preset angle so that the optical axis 31 of the imaging system intersects the helicopter rotor shaft 4. When the blade 5 rotates, the image of the blade tip edge formed by the imaging system 11 falls on the photosensitive surface of the position-sensitive detector 12. The speed sensor 3 is configured to provide an electrical pulse signal generated when a reference blade 5 passes through the detection range of the speed sensor 3. The dynamic balancing analyzer 2 is configured to calculate the imaging position of the blade tip edge on the photosensitive surface based on the electrical signal output by the position-sensitive detector 12, and to calculate the relative height between the blade tips, i.e., the rotor common taper, based on the imaging position and the geometric relationship in the imaging system 11. The imaging position and the geometric relationship in the imaging system 11 are the geometric relationships between the blade tip, the optical center of the imaging system, and the photosensitive surface of the position sensitive detector 12 .

[0033] The following is a detailed description of a method for detecting a helicopter rotor cone using the system, which includes:

[0034] Step 101. When the helicopter rotor is operating at the rated speed, based on the electrical signal generated by the position sensitive detector 12, the position of the image of the tip edge of each blade formed by the imaging system on the photosensitive surface of the position sensitive detector is obtained, as well as the moment when each blade 5 passes through the optical axis of the imaging system.

[0035] Specifically, the imaging position of the blade tip on the photosensitive surface is calculated by position-sensitive detector 12 itself. Different sensors have different calculation methods. The present invention does not impose any restrictions on this. As long as imaging system 11 can image the blade tip on the photosensitive surface, position-sensitive detector 12 can calculate the imaging position.

[0036] The method for calculating the imaging position in the embodiment of the present invention is as follows: after the position sensitive detector 12 performs photoelectric conversion, it outputs at least two electrical signals, which are amplified by a supporting circuit and then transmitted back to the dynamic balancing analyzer 2 through a coaxial cable; the dynamic balancing analyzer 2 quantizes and collects the returned electrical signals to obtain at least two digital signal sequences; the center of gravity position of the light spot is calculated through the at least two digital signal sequences; and the imaging position of the blade tip edge on the photosensitive surface is calculated through the center of gravity position of the light spot.

[0037] Step 102. Calculate the relative heights between the blade tips, i.e., the rotor common taper, based on the imaging position of the blade tip edge on the photosensitive surface and the optical geometric relationship of the imaging system.

[0038] Specifically, the dynamic balancing analyzer 2 calculates the vertical height from the blade tip to the imaging through the triangular geometric relationship based on the imaging position of the blade tip edge on the photosensitive surface, the distance from the position sensitive detector 12 to the optical center of the imaging system, and the horizontal distance between the imaging system 11 and the blade tip.

[0039] See also Figure 2 , the following is a detailed introduction to the triangle geometric relationship:

[0040] This embodiment of the present invention assumes that the helicopter rotor shaft 4 is perpendicular to the ground, and the rotation plane of the blade 5 is approximately horizontal. The imaging system 11 is positioned at an angle α to the horizontal, with the imaging system optical axis 31 extending downward and rearward to approximately intersect the helicopter rotor shaft 4. The value of the upward angle α is determined based on the following condition: when the blade 5 rotates through the imaging system optical axis 31, the image of the blade tip formed by the imaging system 11 falls within the photosensitive area of ​​the position-sensitive detector 12. In this embodiment, the position-sensitive detector 12 is a one-dimensional position-sensitive detector 12.

[0041] In this embodiment, the imaging system 11 uses a small hole, and its optical center is at point O. Through the principle of small hole imaging, the blade tip edge point A passes through the small hole O and is imaged at point A on the photosensitive surface of the position sensitive detector 12. ′ Point. And the optical axis of the imaging system OO ′ Perpendicular to the one-dimensional position sensitive detector photosensitive surface E1E2.

[0042] This embodiment uses a one-dimensional position-sensitive detector 12 based on silicon material with a peak response wavelength of 960 nm. The photosensitive surfaces E1 and E2 are 6 mm long. By covering the aperture with an infrared filter to remove visible light while allowing the near-infrared band to pass through, the infrared light received by the one-dimensional position-sensitive detector primarily comes from the near-infrared light in the sky. Generally speaking, the near-infrared light in the stray light reflected from the lower surface of the blade is essentially negligible.

[0043] Assume that at time t0, blade 1 first passes through the optical axis 31 of the imaging system, and its blade tip edge is at point A. The imaging system forms an image on the photosensitive surface of the position sensitive detector at point A. ′ Point, E1A ′ The corresponding length is d1 in formula (1). When blade 1 leaves the optical axis of the imaging system, blade 2 crosses the optical axis of the imaging system at time t1, and the tip of the blade is at point B. The imaging system forms an image on the photosensitive surface of the position sensitive detector at point B.′ Point, E1B ′ The corresponding length is d2 in formula (1). At time t0, the distance from the upper end point E1 to A ′ The point area will be illuminated to become a bright area, and the lower end point E2 to A of the photosensitive surface of the one-dimensional position sensitive detector ′ The point area will become a dark area because it is blocked by the blades. Since the near-infrared light from the sky is uniformly illuminated, the center of the bright area, i.e., the center of gravity, can be directly obtained through the output of the relevant circuit of the one-dimensional position sensitive detector. ′ It should be twice the distance from the center of gravity of the light spot to E1 at this time, which is set as d1. The situation at time t1 is the same as the above E1A ′ The calculation is similar, E1B ′ This can be considered known, let d2 be the distance d from the pinhole optical center O of imaging system 11 to the photosensitive surface E1E2 of the one-dimensional position-sensitive detector 12. The distance d should be designed to be significantly greater than the length of the one-dimensional position-sensitive detector, for example, d = 15 cm. Therefore, as the position of the image of the blade tip edge on the one-dimensional position-sensitive detector varies from the upper endpoint E to the lower endpoint E2 within the entire photosensitive surface range (E1E2), the angle formed by the line connecting the blade tip edge to its image point on the photosensitive surface and the photosensitive surface E1E2 is always approximately a right angle, with an error of less than 1.2 degrees.

[0044] Based on the above approximation, draw BC perpendicular to OO ′ , and compared with A ″ , then:

[0045]

[0046] again Therefore, it can be obtained that the height difference between adjacent blades is:

[0047]

[0048] Therefore, when the helicopter rotor rotates one circle, the relative height between the entire rotor blades can be obtained, that is, the rotor taper.

[0049] Step 103: Determine the rotor blade's swing array based on the time it takes for the blade tip to pass through the photosensitive surface.

[0050] The following is a detailed description of how to determine the rotor blade swing array, which specifically includes the following steps:

[0051] The time when each blade passes through the optical axis 31 of the imaging system is determined based on the pulse occurrence time of the electrical signal output by the position sensitive detector 12; the opening angles of adjacent blades are obtained based on the time it takes for the rotor to rotate one circle and the time it takes for two adjacent blades to pass through the optical axis 31 of the imaging system; and the swing array of each rotor blade is obtained by subtracting the design value of the opening angle from the measured adjacent blade angles;

[0052] Specifically, after photoelectric conversion, the one-dimensional position-sensitive detector outputs at least two electrical signals, which are then amplified by a supporting circuit and transmitted back to the dynamic balance analyzer 2 via a coaxial cable. The dynamic balance analyzer 2 quantizes and collects the returned electrical signals to obtain at least two digital signal sequences. Because the time the blades block the optical axis of the imaging system during rotor rotation is much shorter than the time when they do not, when the helicopter blades continuously pass through the imaging system 11, the at least two electrical signals output by the position-sensitive detector are in the form of pulse signals. These pulse signals can be amplified, quantized, and collected to form a digital signal sequence. Therefore, based on the digital signal sequence, the peak moments of the two pulse signals can be averaged to determine the moment when the blade tip passes through the optical axis of the imaging system.

[0053] By subtracting the time it takes for the blade tips to cross the imaging system's optical axis during one rotation of the rotor, we can determine the time it takes for adjacent blades to cross the imaging system's optical axis. Dividing this time by the total time it takes for the rotor to complete one rotation can yield the angles of the adjacent blades. More specifically, for a helicopter rotor with five blades, the first through sixth blade tip crossings of the imaging system's optical axis constitute one rotation. Subtracting the designed blade angle from the actual measured adjacent blade angles yields the rotor blade's oscillation array.

[0054] Step 104. Based on the speed pulse signal provided by the speed sensor 3, the corresponding relationship between the obtained rotor common taper and the blade, as well as the corresponding relationship between the swing array and the blade can be determined. Specifically, the blades of the helicopter rotor are generally numbered with numbers and colors. For example, the blades of a certain type of helicopter rotor are marked as blades one to five according to the reverse rotation direction, and blade number one is affixed with reflective tape. When blade number one passes through a photoelectric speed sensor, the speed sensor can generate a pulse electrical signal to the dynamic balance analyzer 2. Obviously, the installation position of the photoelectric speed sensor and the installation position of the rotor cone sensor device are fixed and known. Therefore, using the pulse electrical signal of the speed sensor as a reference, the corresponding relationship between the measured rotor common taper and the blade, as well as the corresponding relationship between the swing array and the blade can be determined.

[0055] Step 105: Record the rotor conicity and shimmy measured when the helicopter rotor rotates multiple times, and average them as the final output result of the helicopter rotor cone detection.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A helicopter rotor cone detection system based on a position sensitive detector is characterized by: include: Dynamic balance analyzer, speed sensor, rotor cone sensor device; The rotor cone sensor device includes: an imaging system, a position sensitive detector; An imaging system for imaging the blade tip onto a photosensitive surface of a position sensitive detector; A position-sensitive detector, configured to perform photoelectric conversion and generate an electrical signal, wherein the electrical signal is used to determine the imaging position of the blade tip edge on the photosensitive surface; the electrical signal is in the form of a pulse and is used to determine the moment when the blade passes through the optical axis of the imaging system; The speed sensor is used to provide an electrical pulse signal generated when a reference blade passes by; A dynamic balancing analyzer is used to calculate the imaging position of the blade tip on the photosensitive surface based on the electrical signal generated by the position sensitive detector, and to calculate the common taper of the rotor blade in combination with the relevant geometric parameters of the imaging system; and to calculate the swing vibration of each blade based on the electrical signal generated by the position sensitive detector; and to determine the corresponding relationship between the common taper and the swing array and each blade based on the electrical pulse signal provided by the speed sensor.

2. The method for detecting a helicopter rotor cone using the position sensitive detector-based detection system according to claim 1, characterized in that: include: When the helicopter rotor is operating at a rated speed, the position of the image of each blade tip edge formed on the photosensitive surface of the position sensitive detector by the imaging system is obtained based on the electrical signal generated by the position sensitive detector, as well as the time when each blade passes through the optical axis of the imaging system; Calculating the relative heights between the blade tips, i.e., the rotor common taper, based on the imaging positions of the blade tip edges on the photosensitive surface and the optical geometric relationship of the imaging system; determining the angle between two adjacent blades based on a time difference between adjacent blades passing through the optical axis of the imaging system and a time required for the rotor to make one rotation; The swing array of the blades is obtained by subtracting the opening angle between two adjacent blades as shown in the drawing from the opening angle between the two adjacent blades obtained by the measurement. Determining the correspondence between the rotor common taper and the blades, and the correspondence between the swing array and each blade, based on an electrical pulse signal provided by a rotation speed sensor and generated by a reference blade passing therethrough, and the orientation of the optical axis of the imaging system; The rotor taper and shimmy are measured continuously for multiple revolutions of the rotor, and the average value is taken as the final measurement result of the rotor taper and shimmy of the helicopter rotor cone.

3. The method according to claim 2, characterized in that Determining the relative height of each blade tip according to the imaging position of the blade tip edge on the photosensitive surface includes: determining the relative vertical height Δh between two adjacent blade tips according to the following formula; Wherein, d is the distance between the optical center of the imaging system and the photosensitive surface; L is the horizontal distance between the optical center of the imaging system and the tip of the blade; α is the angle between the optical axis of the imaging system and the horizontal direction; d1 is the distance from the position where the tip edge of a blade is imaged on the photosensitive surface to the edge of the photosensitive surface; d2 is the distance from the position where the tip edge of an adjacent blade is imaged on the photosensitive surface to the edge of the photosensitive surface.

4. The method according to claim 2, characterized in that Determining the angle between two adjacent blades according to the moment when the blade tip passes through the optical axis of the imaging system includes: determining a passing moment of the blade tip across the optical axis of the imaging system based on a rising edge or a falling edge of a pulse electrical signal output by the position sensitive detector when the blade tip passes across the optical axis of the imaging system; The angle between the two adjacent blades is obtained based on the total time of one rotation of the rotor and the time difference between the two adjacent blades passing through the optical axis of the imaging system; The error angle between the two adjacent blades obtained from actual measurement is subtracted from the designed angle between the two blades, and the error angle is the rotor's swing array.

5. The method according to claim 2, characterized in that Based on the electrical pulse signal provided by the speed sensor, the corresponding relationship between the common taper of the helicopter blade and the blade, as well as the corresponding relationship between the shimmy and each blade are determined, including: Determine, based on the installation position of the speed sensor and the direction of the optical axis of the imaging system, which blade will first cross the optical axis of the imaging system when the speed sensor generates a trigger signal when the reference blade crosses it; The corresponding relationship between the acquired rotor common taper and the blades, as well as the corresponding relationship between the shimmy and each blade, is determined according to the sequence of moments when the blades pass through the optical axis of the imaging system.

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