High-precision measuring device and measuring method for five-degree-of-freedom error motion of rotating shaft system

Abstract

The application discloses a high-precision measurement device and a measurement method for five-degree-of-freedom error motion of a rotating shaft system, and comprises a rotating shaft system axial error motion measurement device, a rotating shaft system pitch error motion measurement device and a rotating shaft system radial error motion measurement device. The application realizes measurement of error motion of the rotating shaft system in the axial direction through an oblique laser triangulation method and a blade diffraction phenomenon, realizes measurement of error motion of the rotating shaft system in the pitch direction through a self-collimation principle and a small-hole diffraction phenomenon, realizes measurement of error motion of the rotating shaft system in the radial direction through a curved surface edge diffraction phenomenon, and finally realizes high-precision measurement of five-degree-of-freedom error motion of the rotating shaft system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of precision measurement, and particularly relates to a high-precision measurement device and method for five-degree-of-freedom error motion of a rotating shaft system based on diffraction principle. BACKGROUND

[0002] The rotating shaft system is a mechanical structure capable of rotating with high precision, and is widely used in measuring instruments such as articulated arm coordinate measuring machines, precision rotary tables, total stations, and laser trackers. Due to inevitable errors in the manufacturing and assembly processes, the rotating shaft system will produce some undesirable motions (i.e., radial, axial, and pitch error motions) when rotating, which will seriously affect the precision of the rotating shaft system.

[0003] Therefore, it is necessary to calibrate and eliminate the errors of the rotating shaft system for these high-precision measuring instruments. The common measurement methods currently include using capacitive displacement sensors for measurement, a machine vision-based error measurement method, and a traditional optical measurement method. However, these methods have certain limitations and shortcomings. For example, when using capacitive displacement sensors for measurement, the curved surface of a small-diameter shaft will cause distortion of the electric field of the capacitive sensor, resulting in measurement errors, and the measurement precision will be limited by the response frequency of the capacitive sensor. When using the machine vision method for measurement, the measurement precision is low and the response speed is poor, making it difficult to measure the error motion of a high-speed rotating shaft system. When using traditional optics for measurement, there are difficulties in installation, complex optical paths, and inconvenience in portability. Patent CN202010521028.5 invents a rotating shaft system five-degree-of-freedom error motion measurement method based on a flat-topped conical boss optical element, which is difficult to achieve high-precision machining of the platform conical boss optical element, thereby affecting the measurement precision. Patent CN201910734340.X invents a straightness error measurement method for a linear displacement stage based on the principle of oblique laser triangulation, but only achieves sub-micron measurement precision.

[0004] Therefore, under the current technical level, it is necessary to propose a novel, effective, simple, high-response, and low-cost measurement device and method for rotating shaft system error motion. SUMMARY

[0005] The purpose of the present application is to provide a high-precision measurement device and method for five-degree-of-freedom error motion of a rotating shaft system based on diffraction principle.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application is as follows:

[0007] A high-precision measurement device for five-degree-of-freedom error motion of a rotating shaft system, comprising a rotating shaft system axial error motion measurement device, a rotating shaft system pitch error motion measurement device, and a rotating shaft system radial error motion measurement device, wherein,

[0008] The rotating shaft axial error motion measuring device is arranged above the rotating shaft and comprises a first laser source (1), a first beam splitting prism (2), a first plane mirror (3), a first PD detection module (4) and the rotating shaft (7).

[0009] The rotating shaft axial error motion measuring device realizes rotating shaft axial error motion measurement through the oblique laser triangulation and the blade diffraction phenomenon. The light beam emitted by the first laser source (1) reaches the first plane mirror (3) through the first beam splitting prism (2) and part of the laser beam, is reflected to the second plane mirror (701) above the rotating shaft (7), is reflected to the blade (402) of the first PD detection module (4) again, forms the blade diffraction phenomenon, the diffraction pattern is captured by the PD detector (401) of the first PD detection module (4), the distance of the light beam movement is calculated according to the energy received by the PD detector (401), and finally the rotating shaft axial error motion measurement is realized through the oblique laser triangulation.

[0010] The rotating shaft pitch error motion measuring device is arranged above the rotating shaft and comprises a first laser source (1), a first beam splitting prism (2), the rotating shaft (7), a small hole (5) and a four-quadrant detector (6).

[0011] The rotating shaft pitch error motion measuring device realizes rotating shaft pitch error motion measurement through the autocollimation principle and the small hole diffraction phenomenon. The light beam emitted by the first laser source (1) reaches the second plane mirror (701) above the rotating shaft (7) through the first beam splitting prism (2) and part of the laser beam, returns to the original route through reflection, and reaches the small hole (5) through the first beam splitting prism (2), thereby forming the small hole diffraction phenomenon. The autocollimation principle is used to realize preliminary measurement of the rotating shaft pitch error motion, the small hole diffraction phenomenon is used to amplify the light spot and improve the imaging resolution of the light spot, and then high-precision rotating shaft pitch error motion measurement is realized.

[0012] The rotating shaft radial error motion measuring device is arranged in the radial direction of the rotating shaft and comprises a second laser source (8), a second beam splitting prism (9), a third beam splitting prism (10), a first right-angle prism (11), a second PD detection module (12), a third PD detection module (13), a second right-angle prism (14) and a fourth beam splitting prism (15).

[0013] The rotating shaft system radial error motion measuring device realizes rotating shaft system radial error motion measurement through curved surface edge diffraction phenomenon. The light beam emitted by the second laser source (8) forms two light beams with equal light intensity through the second beam splitting prism (9), one of which reaches the third beam splitting prism (10) and forms two light beams with equal light intensity again, one of which reaches the first right-angle prism (11) and is reflected to form the curved surface edge diffraction phenomenon with the other parallel light beam passing through the curved surface edge portions on both sides of the rotating shaft system (7), and the two diffraction patterns are captured by the PD detector (1301) and the PD detector (1302) respectively, and the other side is also captured by the PD detection detector (1201) and the PD detection detector (1202). The two signals in one direction are differentially processed to realize rotating shaft system radial error motion measurement.

[0014] Preferably, the light spots of the laser beams emitted by the first laser source (1) and the second laser source (8) are located at the middle positions of the sensitive areas of the detectors in the second PD detection module (12) and the third PD detection module (13) when the rotating shaft system is stationary.

[0015] Preferably, the diameters of the light beams emitted by the first laser source (1) and the second laser source (8) are equal to the side lengths of the sensitive areas of the detectors in the first PD detection module (4), the second PD detection module (12) and the third PD detection module (13).

[0016] The application also provides a high-precision rotating shaft system five-degree-of-freedom error motion measurement method, and the rotating shaft system axial error motion measurement process is as follows:

[0017] When the laser light wave encounters the cutting edge of the blade (402) in the propagation direction, diffraction or bending occurs, and the part of the light wave that is not cut off by the cutting edge moves in the propagation direction, and the cutting edge part signal is bent. The result of the diffraction light producing the blade diffraction is that:

[0018] L1 is the distance from the first laser source (1) to the cutting edge (402), L2 is the distance from the cutting edge (402) to the PD detector (401), the radius of curvature of the cutting edge is represented by p, the Gaussian light beam a is incident on the cutting edge (402) at a distance L1 from the light source (1), the height h is the distance from the center of the incident light beam to the cutting edge (402) along the y-axis, and the incident field (E) at z=0 can be represented by a spherical wave as formula (1)

[0019]

[0020] Wherein, k0 represents the wave number in air, and j is an imaginary number.

[0021] Using the Fourier transform formula, the transverse wave can be derived as follows:

[0022] Using the Fourier transform formula, the transverse wave can be derived as follows:

[0023] where ∫∫ Aperture dkdk represents the area integral of the incident wave for calculating the light flux, k x , k y represent the wave numbers in x, y directions, respectively;

[0024] Using the inverse Fourier transform of the edge transverse wave as the equation, the sum of the diffraction and the transverse field at the first PD detection module (4) position can be obtained E(z0) at z=z0 t ;

[0025]

[0026] where ∫∫ k-space dk x dk y represent the Fourier transform of the image data in real space, e is the natural logarithm, and E is the total electric field wave number and the distance vector from the incident to the diffraction field As follows

[0027]

[0028]

[0029]

[0030] where E x , E y , E z represent the electric field in x, y, z directions; k x , k y , k z are the wave numbers in x, y, z directions; is the distance vector in x, y, z directions, is the unit size in x, y, z directions;

[0031] Measuring near the z-axis, it is assumed that the field measurement is on the axis (x0=0, y0=0, L2>0), and the measured diffraction field along the z-axis is defined using the inverse Fourier transform relationship of the incident field, and is written in the form of error function

[0032]

[0033] where, erfc() represents the error complementary function;

[0034] The diffraction field and the conjugate diffraction field are multiplied to calculate the total power P caused by the clear blade edge smoothed by the terrain

[0035]

[0036] The power received by the PD detector (401) can be expressed as

[0037]

[0038] Wherein, P tot is the total power of the laser beam,

[0039] The distance of the laser beam moving in the vertical direction of the detector is linearly related to the power received by the PD detector (401), and the distance of the beam moving is calculated according to the energy received by the PD detector (401);

[0040] The distance δ z of the rotating shaft system (7) moving in the z direction is measured by using the oblique laser triangulation method, z The energy received by the PD detector (401) changes when the rotating shaft system (7) moves axially in the z direction, and δ z can be expressed by formula (10).

[0041] δ out = f (P x , β) (10)

[0042] Wherein, β is the included angle between the reflected light beam and the z axis;

[0043] Therefore, the axial error motion measurement of the rotating shaft system is realized.

[0044] The application also provides a high-precision measurement method for five-degree-of-freedom error motion of a rotating shaft system, and the pitch error motion measurement process of the rotating shaft system is:

[0045] The preliminary displacement of the pitch motion is obtained by the autocollimation principle. Through the diffraction phenomenon of the small hole, higher imaging resolution of the light spot is obtained, and the edge part of the light spot captured by the four-quadrant detector (6) is clearer, which improves the precision of the device. The pitch motion displacement ε x , ε y is obtained by formula (11) (12);

[0046] ε x = f (QPD x , l1, l2, a) (11)

[0047] ε y = f (QPD y , l1, l2, a) (12)

[0048] Wherein, QPD x , QPDy l1 is the distance from the pinhole (5) to the second plane mirror (701) of the rotating shaft system (7), l2 is the distance from the pinhole (5) to the four-quadrant detector (6), and a is the diameter of the pinhole.

[0049] The application also provides a high-precision measurement method for five-degree-of-freedom error motion of a rotating shaft system, and a radial error motion measurement method for the rotating shaft system is as follows:

[0050] By using the curved edge diffraction principle, when laser waves encounter a curved edge in the propagation direction, diffraction or bending occurs, and the unblocked incident waves, diffraction waves and reflected waves in the light waves are superimposed along the surface rays; the electromagnetic waves incident on the curved edge of the rotating shaft system (7) with a radius of curvature R generate incident waves (1601), diffraction waves (1603) and reflected waves (1602) that propagate along the surface; the total electric field is represented by the sum of the three waves and can be observed on the detector, and the sum can represent the scattering of the optical platform, the spatial domain Fresnel integral is used for the diffraction field, it is assumed that the second laser source (8) with a Gaussian intensity distribution is not divergent, compared with the distance L2 between the curved edge of the rotating shaft system (7) and the PD detector (1201), the PD detector (1201) is relatively small in size, and the PD detector (1201) is placed along the light propagation axis, then only the incident waves (1601) and the edge diffraction waves (1603) can be considered, the two waves are superimposed, and interference fringes are generated in the PD detector (1201) plane,

[0051] The incident field can be represented by a Gaussian distribution

[0052]

[0053] wherein E0 represents the amplitude of the incident field, k0 represents the wave number in air, and a represents the beam diameter, the incident field The diffraction fields generated on the curved surface are superimposed, the superposition wave can be obtained by Fourier transform (FFT), and the total field The total field (sum of the incident field and the diffraction field) can be obtained by inverse Fourier transform of the superposition wave;

[0054] The total field measured along the z-axis can be represented as

[0055]

[0056] wherein ∫∫ k-space dk x dk y represents the Fourier transform of the image data in the real space, and ∫∫ Aperture dxdy represents the area integral of the incident wave, k x , k ydenotes the wave number in the x, y direction, is the position vector from i to j in the coordinate system;

[0057] Finally, the power of the total field at the PD detector (1201) can be calculated as

[0058]

[0059] where * denotes the complex conjugate of and the total power induced at the PD detector (1201) by CED will be calculated by multiplying the total field and the conjugate field at each detector plane and integrating over the PD detector (1201) size (m x m);

[0060] The PD detector (1201) and the PD detector (1202) are placed in the x direction, and the PD detector (1301) and the PD detector (1302) are placed in the y direction to collect the total power of each light beam in a differential configuration;

[0061] The outputs of the second PD detection module (12) and the third detection module (13) can be represented as

[0062]

[0063]

[0064] where P1(x), P2(x) are the outputs of the PD detector (1201) and the PD detector (1202), and P1(y), P2(y) are the outputs of the PD detector (1301) and the PD detector (1302);

[0065] When the rotating shaft system (7) moves in the x and y axis directions, the power output by the second PD detection module (12) and the third PD detection module (13) changes, realizing the measurement of the radial error motion of the rotating shaft system; the movement distance δ x , δ y can be obtained from formula (18) and formula (19).

[0066] δ x = kP OUT (X) (18)

[0067] δ y = kP OUT (Y) (19) Where k is a constant coefficient.

[0068] Compared with the prior art, the beneficial results of the present application are:

[0069] The high-precision measurement device and method for five-degree-of-freedom error motion of rotating shaft systems based on the diffraction principle in this invention uses materials and manufacturing equipment with significantly lower costs than traditional measuring instruments and equipment. Compared to traditional measuring instruments and equipment, this invention is easier to integrate into precision machine tools, articulated coordinate measuring machines, laser trackers, and other devices. It has a higher response speed, can measure high-speed rotating shafts, and achieves high measurement accuracy, ultimately realizing high-precision real-time measurement and real-time compensation of five-degree-of-freedom error motion of rotating shaft systems. Attached Figure Description

[0070] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0071] Figure 1 This is a schematic diagram of the high-precision measurement device for five-degree-of-freedom error motion of a rotating shaft system based on the principle of diffraction according to the present invention.

[0072] Figure 2 This is a schematic diagram illustrating the principle of motion measurement of axial error in a rotating shaft system in this invention.

[0073] Figure 3 This is a schematic diagram of the blade diffraction principle in this invention;

[0074] Figure 4 This is a schematic diagram illustrating the motion measurement principle of the pitch error of the rotating shaft system in this invention;

[0075] Figure 5 This is a schematic diagram of the surface edge diffraction principle in this invention;

[0076] Figure 6 This is a schematic diagram illustrating the principle of radial error motion measurement of the rotating shaft system in this invention. Detailed Implementation

[0077] The technical solutions in the embodiments of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0078] like Figure 1 As shown, a high-precision measuring device and method for five-degree-of-freedom error motion of a rotating shaft system based on the diffraction principle is disclosed, including measuring devices and methods for axial error motion, pitch error motion, and radial error motion of the rotating shaft system. The axial error motion measuring device and the pitch error motion measuring device are located above the rotating shaft system, and the radial error motion measuring device is located in the radial direction of the rotating shaft system.

[0079] like Figure 1As shown, the axial error motion measuring device of the rotating shaft system is set above the rotating shaft system and includes a first laser source (1), a first beam splitter prism (2), a first plane mirror (3), a first PD detection module (4), and a rotating shaft system (7).

[0080] like Figure 2 As shown, the axial error motion measuring device of the rotating shaft system realizes the axial error motion measurement of the rotating shaft system through oblique laser triangulation and blade diffraction phenomenon. The beam emitted by the first laser source (1) passes through the first beam splitter prism (2) and part of the laser beam reaches the first plane mirror (3), which is reflected to the second plane mirror (701) above the rotating shaft system (7), and then reaches the blade (402) of the first PD detection module (4) through reflection, forming blade diffraction phenomenon. The diffraction pattern is captured by the PD detector (401).

[0081] like Figure 3 As shown, the axial error motion measuring device and method of the rotating shaft system adopts the blade diffraction principle. That is, when the laser light wave encounters the blade (402) laterally in the propagation direction, it will diffract or bend. The part of the light wave that is not cut by the blade continues to move in the propagation direction, and the signal of the blade part will bend. The result of blade diffraction generated by the diffracted light can be derived mathematically. L1 is the distance from the first laser source (1) to the blade (402), and L2 is the distance from the blade (402) to the PD detector (401). The radius of curvature of the blade is represented by ρ. A Gaussian beam α is incident from the first laser source (1) onto the blade (402) at a distance L1 from the light source. The height h is the distance from the center of the incident beam to the blade (402) along the y-axis. The incident field (E) at z=0 can be represented by a spherical wave as Equation (1).

[0082]

[0083] Where k0 represents the wave number in the air, and j is an imaginary number;

[0084] Using the Fourier transform formula, transverse waves can be derived.

[0085]

[0086] Among them, ∫∫ Aperture dxdy represents the surface integral with respect to the incident wave, used to calculate luminous flux, k x k y These represent the wave numbers in the x and y directions, respectively;

[0087] Using the inverse Fourier transform of the edge transverse wave as the equation, the sum of the detector position diffraction and the transverse field can be obtained. E at z = z0 t .

[0088]

[0089] where ∫ k-space dk x dk y denotes the Fourier transform of the image data in real space, e is the natural logarithm, Etotalis the total electric field wave number and the distance vector from the incident to the diffracted field as follows

[0090]

[0091]

[0092]

[0093] where E x , E y , E z denotes the electric field in x, y, z direction; k x , k y , K z is the wave number in x, y, z direction; is the distance vector in x, y, z direction, is the unit size in x, y, z direction;

[0094] If the PD detector size is small enough, measured near the z-axis, the field measurement is assumed to be on the axis (x0=0, y0=0, L2>0). Therefore, the measured diffracted field along the z-axis can be defined by the inverse Fourier transform relationship of the incident field, and written in the form of error function

[0095]

[0096] where, erfc() denotes the complementary error function.

[0097] The error coefficient is a complex parameter of the complementary error function. Therefore, by multiplying the diffracted field and the conjugate diffracted field, the total power P caused by the smooth and clear blade edge of the terrain can be calculated,

[0098]

[0099] The power received by the PD detector (401) in the present application can be represented as

[0100]

[0101] where P tot is the total power of the laser beam

[0102] Therefore, in this invention, the distance the laser beam moves in the vertical direction of the detector is linearly related to the power received by the PD detector (401). Based on this principle, the distance the beam moves can be calculated based on the energy received by the PD detector (401).

[0103] The axial error motion measuring device and method of the rotating shaft system adopts the oblique laser triangulation method for measurement. The distance δ of the rotating shaft system (7) moving in the z direction is measured. z The distance the laser beam moves is geometrically related to the distance the laser beam moves. When the rotating axis (7) moves axially in the z-direction, the laser beam also moves accordingly, and the energy received by the PD detector (401) changes, δ z It can be represented by equation (10).

[0104] δ z =f(P out ,β) (10) Where β is the angle between the reflected beam and the z-axis.

[0105] Therefore, this invention achieves axial error motion measurement of rotating shaft systems based on oblique laser triangulation and blade diffraction phenomena.

[0106] like Figure 1 As shown, the pitch error motion measuring device of the rotating axis system is set above the rotating axis system and includes a first laser source (1), a first beam splitter prism (2), a rotating axis system (7), a pinhole (5), and a four-quadrant detector (6).

[0107] The beam emitted by the first laser source (1) of the rotating axis pitch error motion measuring device and measuring method passes through the first beam splitter (2), and part of the laser beam reaches the second plane mirror (701) above the rotating axis (7). After reflection, it returns along the original path and passes through the first beam splitter (2) to reach the pinhole (5), forming a pinhole diffraction phenomenon. The diffraction pattern is captured by the four-quadrant detector (6).

[0108] like Figure 4As shown, the rotating shaft pitch error motion measurement device achieves the measurement of rotating shaft pitch error motion through the self-collimation principle and the pinhole diffraction phenomenon. The dashed line represents the tilt change of the rotating shaft (7) and the position change of the light spot in the four-quadrant detector (6) after pitch motion. When the rotating shaft (7) produces a small pitch displacement during pitch motion, according to the self-collimation principle, a larger displacement can be generated at the four-quadrant detector (6), realizing the preliminary measurement of the rotating shaft pitch error motion. In particular, the present invention places a pinhole with a suitable aperture and distance in front of the four-quadrant detector (6). When the laser beam passes through the pinhole, according to the Huygens-Fresnel principle, the light deviates from the original straight propagation direction, forming some alternating bright and dark rings, which is called the pinhole diffraction phenomenon. Through the pinhole diffraction phenomenon, the light spot of the laser beam is magnified, and the pitch motion of the rotating shaft (7) will cause the four-quadrant detector (6) to produce a larger displacement change, improving the sensitivity and accuracy of the device. Secondly, through the pinhole diffraction phenomenon, a higher spot imaging resolution can be obtained, and the edge of the spot captured by the four-quadrant detector (6) is clearer, thus improving the resolution and accuracy of the device. Its pitch displacement ε x ε y It is derived from equations (11) and (12).

[0109] ε x =f(QPD) x ,l1,l2,a) (11)

[0110] ε y =f(QPD) y ,l1,l2,a) (12)

[0111] Among them, QPD x QPD y l1 is the output of the quadrant detector (6), l2 is the distance from the small hole (5) to the second plane mirror of the rotating axis (7), l3 is the distance from the small hole (5) to the quadrant detector (6), and a is the diameter of the small hole.

[0112] Therefore, this invention achieves the measurement of pitch error motion of a rotating axis system through the principle of self-collimation and the phenomenon of pinhole diffraction.

[0113] like Figure 1 As shown, the radial error motion measuring device of the rotating shaft system is set in the radial direction of the rotating shaft system and includes a second laser source (8), a second beam splitter prism (9), a third beam splitter prism (10), a first right-angle prism (11), a second PD detection module (12), a third PD detection module (13), a second right-angle prism (14), and a fourth beam splitter prism (15).

[0114] like Figure 6As shown, the rotating shaft radial error motion measuring device realizes rotating shaft radial error motion measurement through curved edge diffraction phenomenon. The light beam emitted by the second laser source (8) passes through the second beam splitting prism (9) to form two light beams with equal intensity, one of which reaches the third beam splitting prism (10) to form two light beams with equal intensity again, and then one of the light beams reaches the first right-angle prism (11) to reflect a parallel light beam that passes through the curved edge portion on both sides of the rotating shaft (7), forming a curved edge diffraction phenomenon, and the two diffraction patterns are captured by the PD detection detector (1301) and the PD detection detector (1302) respectively, and the other side is also captured by the PD detection detector (1201) and the PD detection detector (1202).

[0115] As shown in the figure, Figure 5 The rotating shaft radial error motion measuring device and the measuring method adopt the curved edge diffraction principle, that is, when a laser wave encounters a curved edge in the propagation direction, diffraction phenomenon or bending occurs. The incident wave, diffraction wave and reflected wave that are not blocked in the light wave superimpose each other and propagate along the surface. The electromagnetic wave incident on the curved edge of the rotating shaft (7) with a radius of curvature R generates an incident wave (1601), a diffraction wave (1603) and a reflected wave (1602) that propagate along the surface. RB, SB and DSB represent the reflection boundary, the shadow boundary and the deep shadow boundary respectively. This surface ray field can also be excited in the transition region and can be separated into three different regions similar to KED. The total electric field can be represented by the sum of the three waves, and can be observed on the detector. This sum can represent the scattering of the optical platform, and the spatial domain Fresnel integral is used for the diffraction field. Assuming that the second laser source (8) with a Gaussian intensity distribution is not divergent, the PD detector (1201) size is relatively small compared with the distance L2 between the curved edge of the rotating shaft (7) and the PD detector (1201), and the PD detector (1201) is placed along the light propagation axis, only the incident wave (1601) and the edge diffraction wave (1603) can be considered. The two waves superimpose each other to produce interference fringes in the PD detector (1201) plane.

[0116] The incident field can be represented by a Gaussian distribution

[0117]

[0118] where E0 represents the amplitude of the incident field, k0 represents the wave number in air, and a represents the beam diameter. The incident field The diffraction fields generated in the curved surface superimpose each other, and the superposition wave can be obtained by Fourier transform (FFT), and the total field The inverse Fourier transform of the superposition wave can obtain the total field (the sum of the incident field and the diffraction field).

[0119] The total field measured along the z-axis can be expressed as

[0120]

[0121] where, ∫∫ k-space dk x dk y denotes the Fourier transform of the image data in real space, ∫∫ Aperture dxdy denotes the area integral over the incident wave, k x , k y denotes the wave number in the x, y direction, is the position vector from i to j in the coordinate system.

[0122] Finally, the power of the total field at the PD detector (1201) can be calculated as

[0123]

[0124] where, <> * denotes the complex conjugate, and the total power induced at the PD detector (1201) by the CED will be calculated by multiplying the total field and the conjugate field at each detector plane and integrating over the PD detector (1201) size (m x m).

[0125] As shown in Figure 6 , the present application places the PD detector (1201) and the PD detector (1202) in the x direction, and the PD detector (1301) and the PD detector (1302) in the y direction to collect the total power of each light beam in a differential configuration, which eliminates the dependence on the laser intensity. The outputs of the second PD detection module (12) and the third detection module (13) can be represented as

[0126]

[0127]

[0128] where, P1(x), P2(x) are the outputs of the PD detector (1201) and the PD detector (1202), and P1(y), P2(y) are the outputs of the PD detector (1301) and the PD detector (1302).

[0129] When the rotating shaft system (7) moves in the x and y axis directions, the power output of the second PD detection module (12) and the third PD detection module (13) changes, realizing the measurement of the radial error motion of the rotating shaft system. The moving distance δ x , δ y can be obtained from formula (18) and formula (19).

[0130] δx = kP OUT (X) (18)

[0131] δ y = kP OUT (Y) (19) wherein k is a constant coefficient.

[0132] The device can finally realize high-precision measurement of five-degree-of-freedom error motion of a rotating shaft system.

[0133] The above-described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

Claims

1. A high-precision measuring device for five-degree-of-freedom error motion of a rotating shaft system, characterized in that, The application relates to a rotating shaft system axial error motion measuring device, a rotating shaft system pitch error motion measuring device and a rotating shaft system radial error motion measuring device. The rotating shaft system axial error motion measuring device is arranged above the rotating shaft system and comprises a first laser source (1), a first beam splitting prism (2), a first plane mirror (3), a first PD detection module (4) and a rotating shaft system (7). The rotating shaft system axial error motion measuring device realizes rotating shaft system axial error motion measurement through an oblique laser triangulation method and a blade diffraction phenomenon; light beams emitted by the first laser source (1) pass through the first beam splitting prism (2) and reach the first plane mirror (3), are reflected to a second plane mirror (701) above the rotating shaft system (7), are reflected to a blade of the first PD detection module (4) again, form the blade diffraction phenomenon, the diffraction pattern is captured by a PD detector (401) of the first PD detection module (4), the distance of the light beam movement is calculated according to the energy received by the PD detector (401), and finally the rotating shaft system axial error motion measurement is realized through the oblique laser triangulation method. The rotating shaft system pitch error motion measuring device is arranged above the rotating shaft system and comprises the first laser source (1), the first beam splitting prism (2), the rotating shaft system (7), a small hole (5) and a four-quadrant detector (6). The rotating shaft system pitch error motion measuring device realizes rotating shaft system pitch error motion measurement through a self-collimation principle and a small hole diffraction phenomenon; light beams emitted by the first laser source (1) pass through the first beam splitting prism (2) and reach the second plane mirror (701) above the rotating shaft system (7), return to the first beam splitting prism (2) through reflection, and reach the small hole (5) to form the small hole diffraction phenomenon; the self-collimation principle is used to realize the preliminary measurement of the rotating shaft system pitch error motion, the small hole diffraction phenomenon is used to amplify the light spot and improve the imaging resolution of the light spot, and then the high-precision rotating shaft system pitch error motion measurement is realized. The rotating shaft system radial error motion measuring device is arranged in the radial direction of the rotating shaft system and comprises a second laser source (8), a second beam splitting prism (9), a third beam splitting prism (10), a first right-angle prism (11), a second PD detection module (12), a third PD detection module (13), a second right-angle prism (14) and a fourth beam splitting prism (15). The rotating shaft radial error motion measuring device realizes rotating shaft radial error motion measurement through curved surface edge diffraction phenomenon; the light beams emitted by the second laser source (8) pass through the second beam splitting prism (9) to form two light beams with equal light intensity, one of which reaches the third beam splitting prism (10) to form two light beams with equal light intensity again, one of which reaches the first right-angle prism (11) to reflect and, together with the other parallel light beam, pass through the curved surface edge portions on both sides of the rotating shaft (7) to form the curved surface edge diffraction phenomenon, and two diffraction patterns are captured by the PD detector (1301) and the PD detector (1302) respectively, and the other side is also captured by the PD detector (1201) and the PD detector (1202); the two signals in one direction are differentiated to realize rotating shaft radial error motion measurement.

2. The high-precision measurement device for five-degree-of-freedom error motion of a rotating shaft system according to claim 1, characterized by The laser beam spots emitted by the first laser source (1) and the second laser source (8) are located at the middle positions of the sensitive areas of the detectors in the second PD detection module (12) and the third PD detection module (13) when the rotating shaft is stationary.

3. The high-precision measurement device for five-degree-of-freedom error motion of a rotating shaft system according to claim 1, characterized by The diameters of the light beams emitted by the first laser source (1) and the second laser source (8) are equal to the side lengths of the sensitive areas of the detectors of the first PD detection module (4), the second PD detection module (12) and the third PD detection module (13).

4. A measuring method using the high-precision device for five-degree-of-freedom error motion of a rotating shaft system according to any one of claims 1 to 3, characterized by, The rotating shaft axial error motion measurement process is as follows: When the laser light wave encounters the blade edge (402) in the propagation direction, diffraction or bending occurs, the part of the light wave that is not cut off by the blade edge moves in the propagation direction, the blade edge part signal is bent, and the diffraction light produces the result of blade diffraction, which is as follows: L1 is the distance from the first laser source (1) to the blade edge (402), L2 is the distance from the blade edge (402) to the PD detector (401), the radius of curvature of the blade edge is represented by p, the Gaussian light beam a is incident on the blade edge (402) at a distance L1 from the light source, the height h is the distance from the center of the incident light beam to the blade edge (402) on the y-axis, and the incident field E at z=0 is represented by a spherical wave as formula (1) Wherein, E0 represents the amplitude of the incident field, a represents the beam diameter, k0 represents the wave number in air, and j is an imaginary number; The Fourier transform formula is used to derive the transverse wave; where ∫∫ Aperture dxdy represents an area integral of the incident wave for calculating the light flux, k x , k y represent the wave numbers in the x and y directions, respectively; Using the inverse Fourier transform of the edge shear wave as the equation, the sum of the first PD detection module (4) position diffraction and the transverse field is obtained E at z = z0 t ; where ∫∫ k-space dk x dk y denotes the Fourier transform of the image data in real space, e is the natural logarithm, Total electric field Wave number And distance vector from incidence to diffraction field As follows where E x , E y , E z represents the electric field in the x, y, z direction; k x , k y , K z is the wave number in the x, y, z direction; is the distance vector in the x, y, z direction, is the unit size in the x, y, z direction; The z-axis is measured, it is assumed that the field measurement is on the axis, the position is x0=0, y0=0, L2>0, the Fourier inverse transform relationship of the incident field is used to define the measured diffraction field along the z-axis, and it is written in the form of an error function wherein erfc() denotes the error complementary function; The diffraction field and the conjugate diffraction field are multiplied to calculate the total power P caused by the smooth and clear blade edge of the terrain, The power received by the PD detector (401) is represented as where P tot is the total power of the laser beam, The distance of the laser beam moving in the vertical direction of the detector is linearly related to the power received by the PD detector (401), and the distance of the beam moving is calculated according to the energy received by the PD detector (401); The distance δ in the z direction in which the rotating shaft system (7) moves is measured using an oblique laser triangulation method z The distance δ in the z direction in which the rotating shaft system (7) moves is measured using an oblique laser triangulation method z is expressed by formula (10) δ z = f(P out , β) (10) Wherein, β is the included angle between the reflected light beam and the z-axis; Therefore, the axial error motion measurement of the rotating shaft is realized.

5. A measuring method using the high-precision device for five-degree-of-freedom error motion of a rotating shaft system according to any one of claims 1 to 3, characterized by, The pitch error motion measurement process of the rotating shaft is as follows: The preliminary displacement of the pitching movement is obtained through the principle of autocollimation, and the higher imaging resolution of the light spot is obtained through the small aperture diffraction phenomenon, so that the edge part of the light spot captured by the four-quadrant detector (6) is clearer, and the resolution and accuracy of the device are improved. its pitch displacement ε x , ε y is derived from equations (11) (12); ε x = f(QPD x , l1, l2, a) (11) ε y = f(QPD y , l1, l2, a) (12) where QPD x , QPD y is the output of the quadrant photodetector (6), li is the distance from the pinhole (5) to the second plane mirror (701) of the rotation axis system (7), and 12 is the distance from the pinhole (5) to the quadrant photodetector (6), and a is the diameter of the pinhole.

6. A measuring method using the high-precision device for five-degree-of-freedom error motion of a rotating shaft system according to any one of claims 1 to 3, characterized by, The radial error motion measurement method of the rotating shaft system is, The curved edge diffraction principle is adopted, when the laser wave encounters a curved edge in the propagation direction, diffraction or bending occurs, the incident wave, diffraction wave and reflected wave that are not blocked in the light wave are superimposed along the surface ray propagation; the electromagnetic wave incident on the curved edge of the rotating shaft system (7) with a curvature radius R generates incident wave (1601), diffraction wave (1603), and reflected wave (1602), which propagates along the surface; the total electric field is represented by the sum of the three waves, and is observed on the detector, the sum represents the scattering of the optical platform, the spatial domain Fresnel integral is used for the diffraction field, assuming that the second laser source (8) with Gaussian intensity distribution is not divergent, compared with the distance L2 between the curved edge of the rotating shaft system (7) and the PD detector (1201), the PD detector (1201) is relatively small in size, and the PD detector (1201) is placed along the light propagation axis, then only the incident wave (1601) and the edge diffraction wave (1603) are considered, the two waves are superimposed, and interference fringes are generated in the PD detector (1201) plane, The incident field is represented by a Gaussian distribution where E0represents the amplitude of the incident field, k0represents the wave number in air, a represents the beam diameter, the incident field The diffracted fields generated at the curved edges are superimposed, the superimposed wave is obtained by Fourier transform (FFT), and the total field That is, the sum of the incident field and the diffracted field, which is obtained by inverse Fourier of the superimposed wave; The total field measured along the z-axis is represented as where ∫∫ k-space dk x dk y denotes the Fourier transform of the image data in real space, ∫∫ Aperture dxdydenotes the area integral over the incident wave, k x , k y denotes the wave number in the x, y direction, is the position vector from i to j in the coordinate system; Finally, the power of the total field at the PD detector (1201) is calculated as wherein, * represents the complex conjugate of E and the total power sensed at the PD detector (1201) will be calculated by multiplying the total field and the conjugate field at each detector plane and integrating over the PD detector (1201) with size m x m; The PD detector (1201) and the PD detector (1202) are placed in the x direction, and the PD detector (1301) and the PD detector (1302) are placed in the y direction to collect the total power of each light beam in a differential configuration; The outputs of the second PD detection module (12) and the third PD detection module (13) can be represented as Where P1(x), P2(x) are the outputs of the PD detector (1201) and the PD detector (1202), P1(y), P2(y) are the outputs of the PD detector (1301) and the PD detector (1302). When the rotating shaft system (7) moves in the x and y axis directions, the power output by the second PD detection module (12) and the third PD detection module (13) changes, and the radial error motion measurement of the rotating shaft system is realized; the moving distance δ x 、δ y From formula (18) and formula (19), δ x = kP OUT (X) (18) δ y = kP OUT (Y) (19) Where k is a constant coefficient.

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