Helicopter tail transmission shaft coaxiality measuring and calculating method and system

Abstract

The invention provides a helicopter tail transmission shaft coaxiality measuring and calculating method and system, and the method comprises the steps: selecting two cross sections from a reference shaft segment, measuring the distance from a laser displacement sensor to the surface of the shaft segment, and measuring the distance between the two cross sections at the same time; two sections are selected from the shaft section to be measured, the distance between the laser displacement sensor and the surface of the shaft section is measured, and the distance between the two sections is measured at the same time; the measured data are preprocessed; reconstructing a coaxiality calculation model based on a preprocessing result; reconstructing a space geometric model of the tail transmission shaft system based on the space geometric model of the reference shaft section and the space geometric model of the measured shaft section, and calculating the coaxiality deviation of the reference shaft section and the measured shaft section; high-precision coaxiality deviation calculation is achieved, problems can be found in time and adjustment suggestions can be given through real-time evaluation and feedback of a coaxiality calculation result, real-time monitoring and optimization of a helicopter tail transmission shaft system are achieved, and safe operation of a helicopter is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter manufacturing and maintenance, and in particular relates to a method and system for measuring and calculating the coaxiality of a helicopter tail transmission shaft. Background Art

[0002] The helicopter's tail drive shaft is a crucial component of the helicopter's power transmission system, transferring engine power to the tail rotor and ensuring flight stability and maneuverability. The coaxiality of the tail drive shaft is crucial to the helicopter's overall performance and reliability. Poor coaxiality can cause excessive vibration and noise during operation, accelerate component wear, reduce power transmission efficiency, and even cause serious mechanical failures, threatening the helicopter's flight safety.

[0003] Existing methods for measuring the coaxiality of helicopter tail drive shafts have limitations. Some traditional methods rely heavily on manual measurement and empirical judgment, resulting in low accuracy and susceptibility to human influence, making it difficult to accurately reflect the actual coaxiality of the tail drive shaft. While some advanced optical measurement methods offer high accuracy, they are expensive, complex, require specialized technicians, and are significantly limited by the measurement environment in practical applications. Summary of the Invention

[0004] In order to solve the technical problems that the coaxiality measurement method of the helicopter tail drive shaft relies on manual measurement and experience judgment, has low measurement accuracy, is easily affected by human factors, and is difficult to accurately reflect the actual coaxiality of the tail drive shaft; the equipment cost is expensive and the operation is complicated. The present invention provides a method and system for measuring and calculating the coaxiality of the helicopter tail drive shaft, which can be used to accurately evaluate the coaxiality of the helicopter tail drive shaft and provide strong support for the safe operation and performance optimization of the helicopter. The technical solution is as follows:

[0005] In a first aspect, a method for measuring and calculating the coaxiality of a helicopter tail drive shaft is provided, comprising:

[0006] Step 1: Select two first sections in the reference shaft segment, measure the distance from the laser displacement sensor to the surface of the reference shaft segment, obtain two sets of reference shaft segment data, and simultaneously measure the distance between the two first sections; select two second sections in the measured shaft segment, measure the distance from the laser displacement sensor to the surface of the measured shaft segment, obtain two sets of measured shaft segment data, and simultaneously measure the distance between the two second sections;

[0007] Step 2: preprocessing the data measured in step 1, wherein the preprocessing includes filtering, calibration and fitting;

[0008] Step 3: reconstructing a coaxiality calculation model based on the preprocessing result of step 2, wherein the coaxiality calculation model includes a spatial geometric model of the reference shaft segment and a spatial geometric model of the measured shaft segment;

[0009] Step 4: Reconstruct the spatial geometric model of the tail drive shaft system based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment, and calculate the angular adjustment amount and spatial offset amount of the reference shaft segment and the measured shaft segment in the spatial geometric model of the tail drive shaft system to obtain the coaxiality deviation between the reference shaft segment and the measured shaft segment, wherein the coaxiality deviation includes the spatial angle deviation and the distance deviation.

[0010] When measuring data in step 1, the laser displacement sensor is installed on the annular guide rail of the support and positioning system. The laser displacement sensor can rotate circumferentially along the annular guide rail, and can also move along the linear guide rail of the support and positioning system with the annular guide rail; the support and positioning system includes a bracket, annular guide rail, and linear guide rail. The plane of the bracket is perpendicular to the axis of the tail drive shaft. The linear guide rail is installed on the bracket along the axial direction of the tail drive shaft. The annular guide rail is fixed on the slider of the linear guide rail and can move along the axial direction of the tail drive shaft on the linear guide rail with the slider. The bracket is fixed by a locking nut.

[0011] Optionally, in step 2,

[0012] When filtering the acquired data, the Kalman tracking filter method is used to perform adaptive mean filtering on the data to remove outliers and noise, making the consistency of adjacent data points better;

[0013] During the calibration process, the filtered data is calibrated according to the calibration parameters of the laser displacement sensor to eliminate the measurement error of the laser displacement sensor. The data is zero-calibrated with the initial position of the shaft segment as the zero point to ensure the accuracy of the measurement data.

[0014] During the fitting process, the complete shape of the cross section is fitted based on the filtered data. If the annular guide rail is completely perpendicular to the axis of the tail drive shaft, the cross section after fitting is a complete circle; if the annular guide rail is not completely perpendicular to the axis of the tail drive shaft, the cross section after fitting is an ellipse.

[0015] Optionally, step 3 includes:

[0016] Establish an absolute coordinate system: Take the center of the circular guide rail near the bracket end as the coordinate origin and establish an absolute coordinate system. The X-axis of the absolute coordinate system is parallel to the linear guide rail, the Y-axis is perpendicular to the X-axis, and the Z-axis direction is determined according to the right-hand rule.

[0017] Establishing a spatial geometric model of the reference shaft segment: reconstructing the spatial geometric model of the reference shaft segment based on the cross section on the reference shaft and the axial sliding distance of the laser displacement sensor. The parameters of the spatial geometric model of the reference shaft segment include the radius of the reference shaft segment, the spatial coordinates (x1, y1, z1) on the axis centerline, and the angles α1, β1, and γ1 between the axis centerline and the X, Y, and Z directions in the absolute coordinate system.

[0018] Establish a spatial geometric model of the measured shaft segment: reconstruct the spatial geometric model of the measured shaft segment based on the cross-section of the measured shaft segment and the axial sliding distance of the laser displacement sensor. The parameters in the spatial geometric model of the measured shaft segment include the radius of the measured shaft segment, the spatial coordinates on the axis centerline (x2, y2, z2), and the angles α2, β2, and γ2 between the axis centerline and the X, Y, and Z directions in the absolute coordinate system.

[0019] Optionally, step 4 includes:

[0020] The spatial geometric model of the tail drive shaft system is reconstructed based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment using the third-order linear interpolation fitting method; the spatial geometric model curve of the tail drive shaft system can be fitted using the third-order linear interpolation fitting method;

[0021] According to the radius of the reference shaft segment, the spatial coordinates (x1, y1, z1) on the axis centerline, and the included angles α1, β1, γ1, and the radius of the measured shaft segment, the spatial coordinates (x2, y2, z2) on the axis centerline, and the included angles α2, β2, γ2, the angle adjustment amounts θ, φ, Ω and the spatial offsets δ, η, ζ between the reference shaft segment and the measured shaft segment, as well as the spatial angle deviation Ψ and the distance deviation ε of the coaxiality deviation between the reference shaft segment and the measured shaft segment are calculated, and an adjustment suggestion is given, the adjustment suggestion being: adjusting the position of the measured shaft according to the calculated angle adjustment amounts θ, φ, Ω and the spatial offsets δ, η, ζ, as well as the spatial angle deviation Ψ and the distance deviation ε;

[0022] Among them, the angles θ, φ, and Ω are the spatial deviation angles between the measured axis and the reference axis. The rotation axis of θ is the x-line of the reference axis, the rotation axis of φ is the y-line of the reference axis, and the rotation axis of Ω is the z-line of the reference axis. The spatial offsets δ, η, and ζ are the parallelism deviations between the measured axis and the reference axis. δ is the x-direction offset relative to the reference axis, η is the y-direction offset relative to the reference axis, and ζ is the z-direction offset relative to the reference axis.

[0023] The spatial angular deviation Ψ is the angle between the reference axis and the measured axis. The angle between two straight lines in space is defined as the minimum angle between the direction vectors of the two straight lines, and its value range is 0~90°.

[0024] The distance deviation ε is the spatial distance between the reference axis and the measured axis. It is a scalar quantity and has no measurement direction.

[0025] Optionally, the calculation formulas for the angle adjustment amounts θ, φ, Ω and the spatial offset amounts δ, η, ζ between the reference shaft segment and the measured shaft segment are:

[0026] θ=α1-α2, φ=β1-β2, Ω=γ1-γ2,

[0027] δ=x1-x2, η=y1-y2, ζ=z1-z2,

[0028] The calculation formulas for spatial angle deviation Ψ and distance deviation ε are:

[0029] Ψ=arcos(|cosα1 / cosα2+ cosβ1 / cosβ2+ cosγ1 / cosγ2|),

[0030] ε=|(x1-x2)*(cosβ1*cosγ2-cosγ1*cosβ2)+(y1-y2)*( cosα1*cosγ2-cosγ1*cosα2)+(z1-z2)*(cosα1*cosβ2+ cosβ1*cosα2)|.

[0031] Furthermore, the method further comprises:

[0032] If the direction cosines of the two axes meet the proportionality condition, the two axes are determined to be parallel. If the two axes are parallel, it is determined whether the two axes coincide. If the two axes coincide, a no-adjustment suggestion is given, which means that there is no need to adjust the position of the measured axis and the coaxiality of the two axes is qualified. The proportionality condition is cosα1 / cosα2=cosβ1 / cosβ2=cosγ1 / cosγ2.

[0033] If the two axes are not parallel, proceed to step 4.

[0034] Alternatively, calculate whether there is a unique real number m such that the three equations x1=x2+m*cosα2, y1=y2+m*cosβ2, and z1=z2+m*cosγ2 are simultaneously true. If so, determine that the two axes are coincident.

[0035] In the second aspect, a helicopter tail drive shaft coaxiality measurement and calculation system is provided, comprising: a laser displacement sensor, a processor,

[0036] The processor is used to preprocess the data measured by the laser displacement sensor and the cross-sectional distance data, calculate the angular adjustment amount and spatial offset between the reference shaft segment and the measured shaft segment, and the coaxiality deviation between the reference shaft segment and the measured shaft segment, wherein the coaxiality deviation includes the spatial angle deviation and the distance deviation.

[0037] Among them, the laser displacement sensor is installed on the annular guide rail of the support and positioning system. The laser displacement sensor can rotate circumferentially along the annular guide rail, and can also move along the linear guide rail of the support and positioning system with the annular guide rail; the support and positioning system includes a bracket, annular guide rail, and linear guide rail. The plane of the bracket is perpendicular to the axis of the tail drive shaft. The linear guide rail is installed on the bracket along the axial direction of the tail drive shaft. The annular guide rail is fixed on the slider of the linear guide rail and can move along the axial direction of the tail drive shaft on the linear guide rail with the slider. The bracket is fixed by a locking nut.

[0038] The beneficial effects of this application are at least:

[0039] 1. High calculation accuracy: The use of high-precision laser displacement sensors to collect data, combined with adaptive filtering and calibration technology, effectively improves the accuracy and reliability of the data. At the same time, by establishing an accurate coaxiality calculation model, high-precision coaxiality deviation calculation is achieved.

[0040] 2. Low cost: The cost of the laser displacement sensor and support and positioning system used is relatively low, and the calculation process is simple and easy.

[0041] 3. Strong practicability: It can adapt to the coaxiality calculation of helicopter tail drive shaft under different operating conditions and has good versatility and adaptability.

[0042] 4. Real-time feedback and adjustment: Through real-time evaluation and feedback of coaxiality calculation results, problems can be discovered in a timely manner and adjustment suggestions can be given, realizing real-time monitoring and optimization of the helicopter tail drive shaft system to ensure the safe operation of the helicopter. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the support and positioning system;

[0044] Figure 2 It is a schematic cross-sectional view of the fitting when the annular guide rail is completely perpendicular to the axis of the tail drive shaft;

[0045] Figure 3 It is a cross-sectional diagram of the fitting when the annular guide rail is not completely perpendicular to the axis of the tail drive shaft;

[0046] Figure 4 Schematic diagram of the spatial relationship between the reference shaft segment and the measured shaft segment. DETAILED DESCRIPTION

[0047] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention.

[0048] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed in order to provide a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is in no way limited to any specific arrangement and method proposed below, but rather encompasses any improvements, replacements, and modifications to structures, methods, and devices without departing from the spirit of the present invention. In the accompanying drawings and the following description, well-known structures and techniques are not shown to avoid unnecessary ambiguity in the present invention.

[0049] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other, and the various embodiments may refer to and quote each other.

[0050] The present invention is further described in detail below through specific implementation methods and drawings.

[0051] An embodiment of the present invention provides a method for measuring and calculating the coaxiality of a helicopter tail drive shaft, comprising the following steps:

[0052] 1. Collect data

[0053] See also Figure 1 The support and positioning system consists of two sets of height- and angle-adjustable brackets, annular guides, linear guides, and locking nuts. The brackets are constructed of high-strength aluminum alloy and provide stable and reliable support for the annular guides and laser displacement sensors. The brackets are installed across the axis, with the bracket plane perpendicular to the tail drive shaft axis, and securely fastened with locking nuts. The linear guides are mounted on the brackets along the axial direction of the tail drive shaft. The annular guides are fixed to the linear guide slider and can move along the linear guide slider along the axial direction of the tail drive shaft.

[0054] In one embodiment, the support and positioning system may also be replaced by a robotic arm with a movable base.

[0055] See also Figure 1When arranging the laser displacement sensor, the laser displacement sensor is installed on the annular guide rail. The laser displacement sensor can rotate along the circumference of the annular guide rail, and can also move along the linear guide rail with the annular guide rail.

[0056] See also Figure 4 On the one hand, two first sections are selected in the reference shaft segment, and the distance from the laser displacement sensor to the surface of the reference shaft segment is measured to obtain two sets of reference shaft segment data, and the distance between the two first sections is measured at the same time; on the other hand, two second sections are selected in the measured shaft segment, and the distance from the laser displacement sensor to the surface of the measured shaft segment is measured to obtain two sets of measured shaft segment data, and the distance between the two second sections is measured at the same time.

[0057] 2. Data Preprocessing

[0058] Data filtering: Perform adaptive mean filtering on a single set of data, such as Kalman tracking filtering, LMS filtering and other algorithms, to remove outliers and noise, making adjacent data points more consistent.

[0059] Data calibration: The filtered data is calibrated according to the calibration parameters of the laser displacement sensor to eliminate the measurement error of the laser displacement sensor. At the same time, the data is zero-calibrated, with the initial position of the shaft segment as the zero point to ensure the accuracy of the measured data.

[0060] Data fitting: Based on the filtered data, fit the complete shape of the cross section. If the annular guide rail is completely perpendicular to the tail drive shaft axis, the cross section after fitting will be a complete circle. Figure 2 If the annular guide rail is not completely perpendicular to the tail drive shaft axis, the cross section after fitting will be an ellipse, see Figure 3 .

[0061] 3. Reconstructing the coaxiality calculation model

[0062] 31. Establish an absolute coordinate system: Take the center of the circular guide rail close to the bracket end as the origin to establish an absolute coordinate system. The X-axis of the absolute coordinate system is parallel to the linear guide rail, and the Y-axis is perpendicular to the X-axis. The Z-axis direction is determined according to the right-hand rule.

[0063] 32. Establish a spatial geometric model of the reference shaft segment: Reconstruct the spatial geometric model of the reference shaft segment based on the cross section on the reference shaft and the axial sliding distance of the laser displacement sensor. The parameters in the spatial geometric model of the reference shaft segment include the radius of the reference shaft segment, the spatial coordinates on the axis centerline (x1, y1, z1), and the angles α1, β1, and γ1 between the axis centerline and the X, Y, and Z directions in the absolute coordinate system.

[0064] 33. Establish a spatial geometric model of the measured shaft segment: reconstruct the spatial geometric model of the measured shaft segment based on the cross section of the measured shaft segment and the axial sliding distance of the laser displacement sensor. The parameters in the spatial geometric model of the measured shaft segment include the radius of the measured shaft segment, the spatial coordinates on the axis centerline (x2, y2, z2), and the angles α2, β2, and γ2 between the axis centerline and the X, Y, and Z directions in the absolute coordinate system.

[0065] Direction cosines can be directly calculated based on the direction angle. The direction cosines of the reference axis are: cosα1, cosβ1, cosγ1, and the direction cosines of the measured axis are: cosα2, cosβ2, cosγ2. Calculate whether (cosα1) satisfies the following conditions: 2 +(cosβ1) 2 +(cosγ1) 2 =1, (cosα2) 2 +(cosβ2) 2 +(cosγ2) 2 =1 to ensure correct measurement.

[0066] 4. If the direction cosines of the two axes meet the proportionality condition, the two axes are determined to be parallel. If the two axes are parallel, determine whether the two axes coincide. If the two axes coincide, a no-adjustment suggestion is given: there is no need to adjust the position of the measured axis, and the coaxiality of the two axes is qualified.

[0067] Among them, the proportionality condition is cosα1 / cosα2=cosβ1 / cosβ2=cosγ1 / cosγ2.

[0068] If the two axes are not parallel, calculate the coaxiality deviation.

[0069] In one possible implementation, when determining whether two axes coincide, calculate whether there is a unique real number m such that the three equations x1=x2+m*cosα2, y1=y2+m*cosβ2, and z1=z2+m*cosγ2 all hold true. If so, the two axes are determined to coincide.

[0070] 5. Calculate coaxiality: If the two shafts are not parallel, reconstruct the spatial geometric model of the tail drive shaft system based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment. Calculate the coaxiality deviation between the reference shaft segment and the measured shaft segment in the spatial geometric model of the tail drive shaft system, and provide adjustment suggestions.

[0071] 51. Model Input: Import the reconstructed spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment into the calculation program, and use an interpolation fitting algorithm to reconstruct the spatial geometric model of the tail drive shaft system. A third-order linear interpolation fitting method can be used to fit the curve. For detailed procedures, please refer to relevant technologies.

[0072] 52. According to the radius of the reference axis segment, the spatial coordinates (x1, y1, z1) on the axis center line and the included angles α1, β1, γ1, and the radius of the measured axis segment, the spatial coordinates (x2, y2, z2) on the axis center line and the included angles α2, β2, γ2, the angle adjustment amount θ, φ, Ω and the spatial offset amount δ, η, ζ of the reference axis segment and the measured axis segment, and the spatial angle deviation Ψ and the distance deviation ε of the coaxiality deviation of the reference axis segment and the measured axis segment are calculated, wherein the included angles θ, φ, Ω are the spatial deviation angles between the measured axis center line and the reference axis center line, the rotation axis of θ is the x line of the reference axis center line, the rotation axis of φ is the y line of the reference axis center line, and the rotation axis of Ω is the z line of the reference axis center line; the spatial offset amount δ, η, ζ is the parallelism deviation between the measured axis center line and the reference axis center line, δ is the x direction offset amount compared with the reference axis, η is the y direction offset amount compared with the reference axis, and ζ is the z direction offset amount compared with the reference axis.

[0073] The spatial angle deviation Ψ is the included angle between the reference axis and the measured axis, and the definition of the included angle of two straight lines in space is the minimum included angle between the direction vectors of the two straight lines, and the value range is 0-90°.

[0074] The distance deviation ε is the spatial distance between the reference axis and the measured axis, which is a scalar without a measurement direction.

[0075] Among them, the calculation formula of the angle adjustment amount θ, φ, Ω and the spatial offset amount δ, η, ζ of the reference axis segment and the measured axis segment is:

[0076] θ=α1-α2, φ=β1-β2, Ω=γ1-γ2,

[0077] δ=x1-x2, η=y1-y2, ζ=z1-z2,

[0078] The calculation formula of the spatial angle deviation Ψ and the distance deviation ε is:

[0079] Ψ=arcos(|cosα1 / cosα2+ cosβ1 / cosβ2+ cosγ1 / cosγ2|),

[0080] ε=|(x1-x2)*(cosβ1*cosγ2-cosγ1*cosβ2)+(y1-y2)*( cosα1*cosγ2-cosγ1*cosα2)+(z1-z2)*(cosα1*cosβ2+ cosβ1*cosα2)|.

[0081] 53. Adjustment suggestions are given: adjust the position of the measured axis according to the calculated angle adjustment amount θ, φ, Ω and spatial offset amount δ, η, ζ, and spatial angle deviation Ψ and distance deviation ε.

[0082] It should be noted that if the two axes are parallel but not coincident, the coaxiality deviation is also calculated, at this time, the angle adjustment amount and the space offset amount of the obtained reference axis segment and the measured axis segment are both zero.

[0083] The application establishes an absolute coordinate system with the center of the circular guide rail near the end of the support as the coordinate origin, selects two cross sections of the reference axis segment as the reference, obtains the space data of the measured cross section circle by measuring the distance from the laser measuring instrument to the axis surface, and establishes the space coordinates of the reference axis; selects two cross sections of the measured axis segment, measures the cross section circle, and establishes the space coordinates of the measured axis; uses a signal processing method to eliminate measurement errors and fit the most real cross section circle; based on the positional relationship of the reference axis and the measured axis in the space coordinates, the coaxiality relationship between the two axes is calculated, and the corresponding adjustment strategy is given.

[0084] The above only expresses the embodiments of the application, the description is more specific and detailed, but it cannot be understood as the limitation of the patent scope. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the application, which belongs to the protection scope of the application. In addition, the non-exhaustive parts of the application are all conventional technologies.

Claims

1. A method for measuring and calculating the coaxiality of a helicopter tail drive shaft, characterized in that: include: Step 1: Select two first sections in the reference shaft segment, measure the distance from the laser displacement sensor to the surface of the reference shaft segment, obtain two sets of reference shaft segment data, and simultaneously measure the distance between the two first sections; select two second sections in the measured shaft segment, measure the distance from the laser displacement sensor to the surface of the measured shaft segment, obtain two sets of measured shaft segment data, and simultaneously measure the distance between the two second sections; Step 2: preprocessing the data measured in step 1, wherein the preprocessing includes filtering, calibration and fitting; Step 3: reconstructing a coaxiality calculation model based on the preprocessing result of step 2, wherein the coaxiality calculation model includes a spatial geometric model of the reference shaft segment and a spatial geometric model of the measured shaft segment; Step 4: reconstructing the spatial geometric model of the tail drive shaft system based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment, and calculating the angular adjustment amount and spatial offset amount between the reference shaft segment and the measured shaft segment, as well as the coaxiality deviation between the reference shaft segment and the measured shaft segment in the spatial geometric model of the tail drive shaft system, wherein the coaxiality deviation includes the spatial angular deviation and the distance deviation. When measuring data in step 1, the laser displacement sensor is installed on the annular guide rail of the support and positioning system. The laser displacement sensor can rotate circumferentially along the annular guide rail, and can also move along the linear guide rail of the support and positioning system with the annular guide rail; the support and positioning system includes a bracket, annular guide rail, and linear guide rail. The plane of the bracket is perpendicular to the axis of the tail drive shaft. The linear guide rail is installed on the bracket along the axial direction of the tail drive shaft. The annular guide rail is fixed on the slider of the linear guide rail and can move along the axial direction of the tail drive shaft on the linear guide rail with the slider. The bracket is fixed by a locking nut.

2. The method according to claim 1, characterized in that In step 2, When filtering the acquired data, the data is subjected to adaptive mean filtering to remove outliers and noise, making the consistency of adjacent data points better; During the calibration process, the filtered data is calibrated according to the calibration parameters of the laser displacement sensor to eliminate the measurement error of the laser displacement sensor. The data is zero-calibrated with the initial position of the shaft segment as the zero point to ensure the accuracy of the measurement data. During the fitting process, the complete shape of the cross section is fitted based on the filtered data. If the annular guide rail is completely perpendicular to the axis of the tail drive shaft, the cross section after fitting is a complete circle; if the annular guide rail is not completely perpendicular to the axis of the tail drive shaft, the cross section after fitting is an ellipse.

3. The method according to claim 1, characterized in that Step 3 includes: Establish an absolute coordinate system: Take the center of the circular guide rail near the bracket end as the coordinate origin and establish an absolute coordinate system. The X-axis of the absolute coordinate system is parallel to the linear guide rail, the Y-axis is perpendicular to the X-axis, and the Z-axis direction is determined according to the right-hand rule. Establishing a spatial geometric model of the reference shaft segment: reconstructing the spatial geometric model of the reference shaft segment based on the cross section on the reference shaft and the axial sliding distance of the laser displacement sensor. The parameters of the spatial geometric model of the reference shaft segment include the radius of the reference shaft segment, the spatial coordinates (x1, y1, z1) on the axis centerline, and the angles α1, β1, and γ1 between the axis centerline and the X, Y, and Z directions in the absolute coordinate system. Establish a spatial geometric model of the measured shaft segment: reconstruct the spatial geometric model of the measured shaft segment based on the cross-section of the measured shaft segment and the axial sliding distance of the laser displacement sensor. The parameters in the spatial geometric model of the measured shaft segment include the radius of the measured shaft segment, the spatial coordinates on the axis centerline (x2, y2, z2), and the angles α2, β2, and γ2 between the axis centerline and the X, Y, and Z directions in the absolute coordinate system.

4. The method according to claim 3, characterized in that Step 4 includes: The spatial geometric model of the tail drive shaft system is reconstructed based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment using an interpolation fitting algorithm. According to the radius of the reference shaft segment, the spatial coordinates (x1, y1, z1) on the axis centerline, and the included angles α1, β1, γ1, and the radius of the measured shaft segment, the spatial coordinates (x2, y2, z2) on the axis centerline, and the included angles α2, β2, γ2, the angle adjustment amounts θ, φ, Ω and the spatial offsets δ, η, ζ between the reference shaft segment and the measured shaft segment, as well as the spatial angle deviation Ψ and the distance deviation ε of the coaxiality deviation between the reference shaft segment and the measured shaft segment are calculated, and an adjustment suggestion is given, the adjustment suggestion being: adjusting the position of the measured shaft according to the calculated angle adjustment amounts θ, φ, Ω and the spatial offsets δ, η, ζ, as well as the spatial angle deviation Ψ and the distance deviation ε; Among them, the angles θ, φ, and Ω are the spatial deviation angles between the measured axis centerline and the reference axis centerline, the rotation axis of θ is the x-line of the reference axis centerline, the rotation axis of φ is the y-line of the reference axis centerline, and the rotation axis of Ω is the z-line of the reference axis centerline; the spatial offsets δ, η, and ζ are the parallelism deviations between the measured axis centerline and the reference axis centerline, δ is the x-direction offset compared to the reference axis, η is the y-direction offset compared to the reference axis, and ζ is the z-direction offset compared to the reference axis.

5. The method according to claim 4, characterized in that The calculation formulas for the angle adjustment θ, φ, Ω and the spatial offset δ, η, ζ between the reference shaft segment and the measured shaft segment are as follows: θ=α1-α2, φ=β1-β2, Ω=γ1-γ2, δ=x1-x2, η=y1-y2, ζ=z1-z2, The calculation formulas for spatial angle deviation Ψ and distance deviation ε are: Ψ=arcos(|cosα1 / cosα2+ cosβ1 / cosβ2+ cosγ1 / cosγ2|), ε=|(x1-x2)*(cosβ1*cosγ2-cosγ1*cosβ2)+(y1-y2)*( cosα1*cosγ2-cosγ1*cosα2)+(z1-z2)*(cosα1*cosβ2+ cosβ1*cosα2)|.

6. The method according to claim 4, characterized in that The method further comprises: If the direction cosines of the two axes meet the proportionality condition, the two axes are determined to be parallel. If the two axes are parallel, it is determined whether the two axes coincide. If the two axes coincide, a no-adjustment suggestion is given, which means that there is no need to adjust the position of the measured axis and the coaxiality of the two axes is qualified. The proportionality condition is cosα1 / cosα2=cosβ1 / cosβ2=cosγ1 / cosγ2. If the two axes are not parallel, proceed to step 4.

7. The method according to claim 6, characterized in that Calculate whether there is a unique real number m such that the three equations x1=x2+m*cosα2, y1=y2+m*cosβ2, and z1=z2+m*cosγ2 are simultaneously true. If so, the two axes are considered to be coincident.

8. A helicopter tail drive shaft coaxiality measurement and calculation system, characterized in that: include: Laser displacement sensor, processor, The processor is used to preprocess the data measured by the laser displacement sensor and the cross-sectional distance data, calculate the angular adjustment amount and spatial offset between the reference shaft segment and the measured shaft segment, and the coaxiality deviation between the reference shaft segment and the measured shaft segment, wherein the coaxiality deviation includes the spatial angle deviation and the distance deviation.

9. The system according to claim 8, characterized in that The laser displacement sensor is installed on the annular guide rail of the support and positioning system. The laser displacement sensor can rotate circumferentially along the annular guide rail, and can also move along the linear guide rail of the support and positioning system with the annular guide rail; the support and positioning system includes a bracket, annular guide rail, and linear guide rail. The plane of the bracket is perpendicular to the axis of the tail drive shaft. The linear guide rail is installed on the bracket along the axial direction of the tail drive shaft. The annular guide rail is fixed on the slider of the linear guide rail and can move along the axial direction of the tail drive shaft on the linear guide rail with the slider. The bracket is fixed by a locking nut.

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