A spindle rotation error measurement method and device based on optical principles

Abstract

The application discloses a kind of main shaft rotation error measurement method and device based on optical principle.The main shaft rotation error measurement method is as follows: one, constructs coordinate system;Two, the axial error of main shaft is measured using light interference principle, and a beam is separated in the test light of axial error measurement and is shot to PSD, and radial error is obtained.The application sets up taper angle reflector at the end of main shaft, and the axial error of main shaft is measured using laser interference principle, the axial error measured by this mode is not influenced by radial error, the influence of inclination error can also be ignored, the complexity of axial error settlement is greatly reduced, and the detection precision is improved.In addition, while detecting axial and radial error, the application synchronously detects inclination error using annular reflector and laser autocollimator, and separates the measurement error caused by the inclination change of main shaft in radial error using the value of measured inclination error, and improves the detection accuracy of radial error.

Description

Technical Field

[0001] This invention belongs to the field of spindle rotation error measurement in precision measurement technology, specifically relating to a method and apparatus for simultaneously detecting axial, radial, and tilt errors of a spindle using a laser interferometer, a PSD sensor, and a laser autocollimator. Background Technology

[0002] The precision of a machine tool largely determines the precision of the machined parts. To ensure the quality of machined products, the development of machine tools towards higher precision is an inevitable trend. The spindle is the core component of a CNC machine tool, and its rotational error is a significant factor affecting machining accuracy. Experimental studies have shown that in precision machining, spindle rotational error accounts for 30% to 70% of the total error, and the higher the precision level of the machine tool, the larger the proportion of spindle rotational error in the total error. Measuring rotational error is of great practical significance for evaluating the precision of machine tool spindles, monitoring their operating status, and promptly detecting and diagnosing spindle faults.

[0003] Currently, there are many methods for measuring spindle rotation error. A common method is error separation using a standard bar, employing one-dimensional displacement sensors such as capacitive and eddy current sensors to measure the spindle's error motion. However, this method requires a standard bar, increasing manufacturing costs and complexity, and necessitates error separation. Some researchers have proposed a method based on optical target marking tracking to measure spindle rotation error, but this method is only sensitive to radial error and struggles to measure other errors. This invention designs a spindle rotation error measurement method based on laser interferometry. Utilizing the principle of laser interferometry, it offers high precision; it eliminates the need for a standard bar, saving costs; and when measuring radial and axial errors, the two are decoupled, simplifying data calculation. Furthermore, it enables high-precision spindle error measurement and evaluation using only a laser interferometer, a single PSD sensor, and a laser autocollimator. Summary of the Invention

[0004] The purpose of this invention is to propose a method and device for measuring spindle rotation error based on optical principles.

[0005] In a first aspect, the present invention provides a method for measuring spindle rotation error based on laser interferometry. The measuring device used includes a laser interferometer, a first pyramidal reflector, a second pyramidal reflector, and a first beam splitter. The laser interferometer, the first beam splitter, and the second pyramidal reflector are arranged sequentially along the axial direction of the spindle being measured. During the measurement process, the second pyramidal reflector is coaxially fixedly installed at the end of the spindle being measured. The first pyramidal reflector is installed on the side of the first beam splitter.

[0006] The method for measuring spindle rotation error includes the following steps:

[0007] Step 1: Establish a coordinate system on the plane perpendicular to the axis of the main spindle being measured. The main spindle being measured rotates, and the laser interferometer emits a laser beam.

[0008] Step 2: Spindle rotation error detection.

[0009] The laser beam passes through the first beam splitter and the first pyramidal reflector to form a standard beam that enters the detection area of ​​the laser interferometer; the laser beam passes through the second pyramidal reflector to form a test beam that enters the detection area of ​​the laser interferometer; the standard beam and the test beam form interference fringes.

[0010] Calculate the axial error z of the measured spindle. θ as follows:

[0011]

[0012] Where, N θ λ represents the change in the number of interference fringes; λ0 is the laser wavelength; and n is the air refractive index.

[0013] Preferably, the measuring device further includes a second beam splitter and a PSD sensor; the second beam splitter is disposed between the laser interferometer and the second pyramidal reflector; the PSD sensor is disposed on the side of the second beam splitter.

[0014] In step two, the test light forms a second beam splitter at the second beam splitter; the second beam splitter enters the PSD sensor; while detecting the axial error of the main shaft in step two, the radial error of the main shaft (X′(θ), Y′(θ)) is calculated as follows:

[0015] X′(θ)=X(θ)-base(X)

[0016] Y′(θ)=Y(θ)-base(Y)

[0017] Where base(X) is the average x-axis coordinate of the spot position on the PSD sensor during one revolution of the spindle under test; base(Y) is the average y-axis coordinate of the spot position during one revolution of the spindle under test; (X(θ), Y(θ)) are the spot position coordinates on the PSD sensor.

[0018] Preferably, the measuring device further includes an annular plane mirror and a laser autocollimator; the annular plane mirror is fixed on the main shaft being measured; the laser autocollimator is mounted on the frame and is perpendicular to the mirror surface of the annular plane mirror.

[0019] In step one, the laser interferometer emits a laser beam simultaneously with the laser autocollimator. This laser beam is reflected by the annular plane mirror and enters the detection area of ​​the laser autocollimator. In step two, while detecting the axial and radial errors of the principal shaft, the components α of the principal shaft tilt angle error in the x-axis and y-axis directions are calculated. θ(x), α θ (y) is as follows:

[0020]

[0021] Where, γ θ (x), γ θ (y) represents the components of the autocollimator reading in the x-axis and y-axis directions, respectively; These represent the components of the installation error of the annular plane mirror in the x-axis and y-axis directions, respectively.

[0022] Preferably, the coordinate system constructed in step one has the y-axis direction perpendicular to the plane containing the incident laser beam and the first split beam, and the x-axis direction perpendicular to both the incident laser beam and the y-axis direction.

[0023] After obtaining the spindle radial error (X′(θ), Y′(θ)) and spindle tilt angle error, the spindle tilt angle error is updated to (X″(θ), Y′(θ)); where the expression for X″(θ) is as follows:

[0024]

[0025] Where L is the distance between the incident laser beam and the reflected beam; the x-axis is parallel to the plane containing the incident laser beam and the first beam splitter.

[0026] Secondly, the present invention provides a spindle rotation error measurement device based on laser interferometry, comprising a laser interferometer, a first pyramidal reflector, a second pyramidal reflector, a first beam splitter, a second beam splitter, a PSD sensor, an annular plane mirror, and a laser autocollimator; wherein the laser interferometer, the first beam splitter, the second beam splitter, and the second pyramidal reflector are arranged sequentially along the axial direction of the spindle being measured; during the measurement process, the second pyramidal reflector is coaxially fixedly installed at the end of the spindle being measured; the first pyramidal reflector is installed on the side of the first beam splitter; the PSD sensor is set on the side of the second beam splitter; the annular plane mirror is fixed on the spindle being measured; and the laser autocollimator is installed on a frame and perpendicularly faces the mirror surface of the annular plane mirror.

[0027] During the test, the incident laser emitted from the laser interferometer passes through the first beam splitter and enters the second pyramidal reflector; the incident laser forms a first split beam at the first beam splitter; the first split beam is reflected by the first pyramidal reflector and re-enters the first beam splitter, and after being reflected again by the first beam splitter, it is directed towards the detection area of ​​the laser interferometer; the incident laser is reflected by the second pyramidal reflector to form a reflected beam; the reflected beam is directed towards the detection area of ​​the laser interferometer and forms a second split beam at the second beam splitter; the second split beam enters the PSD sensor. The laser emitted from the laser autocollimator is reflected by the annular plane mirror and illuminates the laser autocollimator.

[0028] Preferably, the coating directions of both the first and second beam splitters are at a 45° angle to the laser emission direction.

[0029] Preferably, the reflecting surface of the second pyramidal reflector is a cone with a cone angle of 90°.

[0030] Preferably, the reflecting surface of the first pyramidal reflector is in the shape of a right-angled L or a cone with a cone angle of 90°.

[0031] Preferably, the incident laser does not coincide with the axis of the measured spindle.

[0032] Preferably, the distance between the straight line containing the portion of the first beam that enters the first pyramidal reflector and the tip of the first pyramidal reflector is equal to the distance between the straight line containing the incident laser and the tip of the second pyramidal reflector in the initial state.

[0033] The beneficial effects of this invention are as follows:

[0034] 1. The present invention sets a tapered reflector at the end of the spindle and uses the principle of laser interference to measure the axial error of the spindle. The axial error measured by this method is not affected by the radial error and the influence of the tilt angle error can be ignored, which greatly reduces the complexity of axial error calculation and improves the detection accuracy.

[0035] 2. This invention adds a set of beam mirrors and a PSD sensor to the axial detection, and realizes radial error detection simultaneously without adding an additional light source, which reduces equipment cost, simplifies operation, and avoids the additional errors caused by asynchronous error detection.

[0036] 3. While detecting axial and radial errors, this invention uses a ring mirror and a laser autocollimator to simultaneously detect tilt angle errors. By using the measured tilt angle error values, the measurement error caused by the change in the principal shaft tilt angle in the radial error is separated, thereby improving the accuracy of radial error detection.

[0037] 4. This invention can simultaneously measure axial error, radial error, and tilt error. The measured axial and radial errors are uncoupled, and the tilt error has a negligible impact on the axial error measurement. Only the spindle tilt error has a non-negligible impact on the spindle radial error measurement, and the separation of this measurement error is very convenient. Therefore, this invention avoids the use of a standard bar, saving costs, and significantly reduces the computational workload of error separation, thus improving measurement efficiency. It is evident that this invention achieves a high degree of integration in the measurement of axial, radial, and tilt errors, with each error operating independently to achieve high precision.

[0038] 5. The high-precision measurement of this invention only requires high precision of optical components, while the requirements for the processing precision and installation precision of the detection and mounting parts are low, and there is no need to control factors such as surface roughness and spindle material. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the overall optical path of the measuring device used in this invention.

[0040] Figure 2 This is a schematic diagram of the installation of the second pyramidal reflector in this invention.

[0041] Figure 3 This is a schematic diagram of the measurement principle of the laser autocollimator used in this invention.

[0042] Figure 4 This is a schematic diagram illustrating the effect of tilt angle error around the y-axis on radial and axial errors according to the present invention.

[0043] Figure 5 This is a theoretical analysis diagram showing the influence of the tilt angle error around the x-axis on the measurement of radial and axial errors in this invention.

[0044] Figure 6 This is a theoretical analysis diagram showing the influence of radial error on axial error measurement according to the present invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings.

[0046] like Figure 1 As shown, a spindle rotation error measurement method based on laser interferometry is used, and the measuring device includes a laser interferometer, a first pyramidal reflector a, a second pyramidal reflector b, a first beam splitter 1, a second beam splitter 2, a PSD sensor, a ring plane mirror c, and a laser autocollimator 3.

[0047] The laser interferometer, the first beam splitter 1, the second beam splitter 2, and the second pyramidal reflector b are arranged sequentially along the axis of the main shaft being measured. The laser interferometer, the first beam splitter 1, and the second beam splitter 2 are all mounted on a frame; during measurement, the second pyramidal reflector b is coaxially fixed at the end of the main shaft. The mirror surface of the second pyramidal reflector b faces the laser interferometer.

[0048] The reflecting surface of the first pyramidal reflector a is right-angled L-shaped. The reflecting surface of the second pyramidal reflector b is conical, and the cone angle is 90°. The coating directions of the first beam splitter 1 and the second beam splitter 2 are both at a 45° angle to the axis of the measured principal axis.

[0049] The first pyramidal reflector a is mounted on the side of the first beam splitter 1. The PSD sensor is mounted on the rack below the second beam splitter 2 perpendicular to the axis, so that the reflected light from the second beam splitter 2 can hit the PSD sensor.

[0050] The reflective surface of the first pyramidal reflector a is installed opposite to the coating of the first beam splitter 1, so that the light reflected by the first beam splitter 1 is reflected by the first pyramidal reflector a and then enters the coating of the first beam splitter 1 perpendicular to the initial incident direction of the laser.

[0051] During the test, the incident laser emitted from the laser interferometer passes through the first beam splitter 1 and the second beam splitter 2 and enters the second pyramidal reflector b. The incident laser forms a first split beam at the first beam splitter 1; the first split beam is reflected by the first pyramidal reflector a and then re-enters the first beam splitter 1, and after being reflected by the first beam splitter 1, it is directed towards the detection area of ​​the laser interferometer.

[0052] The incident laser beam is reflected by the second pyramidal reflector b to form a reflected beam; the reflected beam passes through the second beam splitter 2 and the first beam splitter 1 and is directed towards the detection area of ​​the laser interferometer; the reflected beam forms a second split beam at the second beam splitter 2; the second split beam enters the PSD sensor. The first split beam serves as the standard beam, and the reflected beam serves as the test beam, forming interference fringes in the detection area of ​​the laser interferometer.

[0053] The incident laser beam does not coincide with the axis of the measured principal axis. The distance between the line containing the portion of the first beam that enters the first pyramidal reflector a and the tip of the first pyramidal reflector a is equal to the distance between the line containing the incident laser beam and the tip of the second pyramidal reflector b in the initial state, so that the positions of the first beam and the reflected beam entering the detection area of ​​the laser interferometer are the same or similar.

[0054] The portion of the first beam splitter passing through the first beam splitter 1, the beam splitter reflected from the incident laser by the second beam splitter 2, and the beam splitter reflected from the first beam splitter 1 do not strike any component of the measuring device, have no effect, and do not affect the detection results, so they will not be described in detail.

[0055] The annular plane mirror c is coaxially fixed on the outer circumference of the main shaft being measured. While ensuring the surface quality of the annular plane mirror c, the perpendicularity of the mirror surface to the main shaft axis must also be guaranteed. The laser autocollimator 3 is mounted on the frame, facing the mirror surface of the annular plane mirror c, and is used to emit and receive laser light.

[0056] The specific steps of this laser interferometry-based method for measuring principal axis tilt angle error are as follows:

[0057] Step 1: Assemble and install the first beam splitter 1 and the second beam splitter 2, ensuring that their splitting surfaces are parallel and both form a 45° angle with the axis of the main shaft being measured to guarantee the accuracy of the optical path measurement. The first pyramidal reflector a is installed on the upper part of the first beam splitter 1 to generate standard light; the second pyramidal reflector b is installed at the center of the main shaft end face to generate experimental light. Install a PSD sensor on the side of the second beam splitter 2 to receive the light reflected from it and obtain the radial error of the main shaft. During installation, align the center of the sensor with the optical path to ensure efficient use of the PSD sensor and prevent the loss of optical signals.

[0058] An error analysis coordinate system is constructed with the plane perpendicular to the incident laser and the plane containing the first split beam as the y-axis direction, and the direction perpendicular to both the incident laser and the y-axis direction as the x-axis direction.

[0059] Step 2: Run the spindle under test. The spindle under test drives the second pyramidal reflector b to rotate. After the motion stabilizes, run the laser interferometer. The laser emitted by the laser interferometer is split into two beams by the first beam splitter 1. One beam is reflected at the first beam splitter 1 and returns to the laser interferometer under the secondary reflection of the first pyramidal reflector a and the first beam splitter 1. This beam is the standard beam. The other beam passes through the first beam splitter 1 and is reflected by the second pyramidal reflector b installed at the spindle under test. This beam also returns to the laser interferometer. This beam is the experimental beam. Since the standard beam and the experimental beam are obtained by splitting the same laser beam, they meet the coherence condition and thus interfere.

[0060] Because the spindle will be displaced along its axis during the spindle's movement, i.e., there is an axial error, the interference fringes between the two beams of light will change with the rotation of the spindle. When the corner bevel mirror moves half a laser wavelength along the axis of the spindle, an interference fringe intensity change cycle (bright-dark-bright) will appear. By calculating this change, the axial error of the spindle can be solved. This part is the axial detection module part1 used to measure the axial error of the spindle.

[0061] Step 3: Calculate the axial error of the principal spindle. The changes in interference fringes are recorded by computer to calculate the axial error of the principal spindle.

[0062] Based on the fundamental principles of laser interferometry, the axial error z of the measured principal axis in phase θ is... θ It can be represented as:

[0063]

[0064] Where, N θλ0 is the change in the number of interference fringes on the measured principal axis at phase θ relative to the initial time (i.e., the difference between the number of interference fringes on the laser interferometer at phase θ and the number of interference fringes on the laser interferometer at the initial time); λ0 is the laser wavelength; and n is the air refractive index.

[0065] Step 4: After the experimental light is acted upon by the second pyramidal reflector b mounted on the main shaft, it is subjected to the action of the second beam splitter 2 on its way back to the receiving end of the laser interferometer. The experimental light is split into two beams by the second beam splitter 2. One beam passes directly through the beam splitter and returns to the detection area of ​​the laser interferometer; the other beam is reflected at the second beam splitter 2, thus changing its path and projecting onto the PSD sensor on the side of the second beam splitter 2. Because the radial movement of the main shaft causes the incident point of the laser at the second pyramidal reflector b to change, its exit point also changes. Therefore, the laser incident position signal detected by the PSD sensor will also change. The vector of the position signals detected by the PSD sensor at different phases θ and the initial position signal, respectively, represents the radial error of the main shaft at different phases θ. This part is the radial detection module part 2 used to measure the radial error of the main shaft.

[0066] The principle behind this step is that, due to the geometric relationship between the optical paths, the radial displacement of the spindle can be inferred from the position of the light spot trajectory on the PSD sensor. For example... Figure 1 As shown, a rectangular coordinate system XOY is established at the second pyramidal reflector b. Assuming the radial offset of the measured spindle during rotation is Δx in the positive X-axis direction and Δy in the positive Y-axis direction, a corresponding offset will occur on the PSD sensor. The light spot before the offset on the PSD sensor will move to a new position after being offset Δx in the X-direction and Δy in the Y-direction. Based on this theoretical foundation, it can be concluded that the data changes of the light spot trajectory points on the PSD sensor correspond one-to-one with the radial error of the spindle.

[0067] Step 5: Calculate the spindle radial error. First, set the dataset of the spot trajectory points used to calculate the radial error as P = [X(θ)]. i ), Y(θ) i )], i = 1, 2, ..., m. θ i Let P be the phase angle of the spindle under test when the PSD sensor acquires the i-th data point; m is the number of data points acquired by the PSD sensor during one revolution of the spindle under test. The process of calculating the radial error of the spindle using the dataset P is as follows:

[0068] 5-1. First, distribute the X and Y coordinate values ​​of dataset P in the ΔX-t and ΔY-t coordinate systems respectively, according to time, as follows: Figure 2As shown, due to the existence of a baseline value, the overall curve will fluctuate around this baseline value. To more intuitively represent the numerical value of the principal axis radial error, the X-axis coordinate X(θ) of each sampling point is... i The following calculations are performed to obtain the X-axis component X′(θ) of the radial error. i ).

[0069]

[0070] X′(θ i )=X(θ i )-base(X)

[0071] Where base(X) is the average X-axis coordinate of each sampling point in dataset P.

[0072] Through this calculation, X′(θ) i The image will fluctuate around ΔX=0, which can more intuitively reflect the radial error of the spindle.

[0073] Similarly, for the Y-axis coordinate Y(θ) of each sampling point i The following calculations are performed to obtain the Y-axis component Y′(θ) of the radial error. i ).

[0074]

[0075] Y′(θ i )=Y(θ i )-base(Y)

[0076] Where base(Y) is the average Y-axis coordinate of each sampling point in dataset P.

[0077] (X′(θ i ), Y′(θ i That is, the measured principal axis at phase θ i Radial error; using radial error to evaluate spindle rotation error is of great significance for improving spindle accuracy.

[0078] Step Six: Calculate the spindle tilt angle error. The process of measuring the tilt angle error using a laser autocollimator is as follows: Figure 3 As shown, the laser emitted from the laser autocollimator 3 is reflected back to the detection area of ​​the laser autocollimator 3 after being reflected by the annular plane mirror c. When the annular plane mirror c rotates with the main shaft, the tilt angle error of the main shaft is reflected on the mirror surface, causing the landing point of the laser beam received by the laser autocollimator 3 to shift. Based on this principle, the tilt angle error of the main shaft can be calculated. This part is the tilt angle detection module part 3 used to measure the tilt angle error of the main shaft.

[0079] Installation error of plane mirror After calibration, the γ value can be read from the autocollimator during spindle rotation. θ The tilt angle error α of the spindle is separated from the spindle. θ The yaw angle errors of the main spindle in the X and Y directions are:

[0080]

[0081] Where, α θ (x), α θ (y) represents the principal axis tilt angle error α θ Components in the x and y directions; γ θ (x), γ θ (y) represents the autocollimator reading γ. θ Components in the x and y directions; Installation error Components in the x and y directions.

[0082] The starting point for measuring the spindle tilt angle must be consistent with the starting point for calibrating the plane mirror installation error; that is, the above error separation is a point-to-point separation.

[0083] Step 7: Error Separation. When there is an angular error in the spindle, the optical path will shift as the angular angle changes. This step is used to remove measurement errors between different errors.

[0084] 7-1. Analyze the influence of tilt angle error around the y-axis on axial and radial errors.

[0085] like Figure 4 As shown, analysis reveals that when the main shaft deflects around the y-axis, the reflected light path of the second pyramidal reflector b remains the same as the original reflected light path; only the difference in the optical path between the incident point before deflection and the exit point after deflection causes a change in the optical path length (when the incident point of the second pyramidal reflector b deflects away from the laser interferometer). Therefore, the tilt angle error of the main shaft around the y-axis does not affect the measurement of the radial error of the main shaft, but only affects the measurement of the axial error of the main shaft.

[0086] The measurement error analysis of the axial error caused by the tilt angle error of the spindle around the y-axis is as follows:

[0087] The non-overlapping portions of the incident and reflected laser beams are calculated before and after the main shaft y-axis oscillates around the y-axis.

[0088] The optical path length S of the non-coincident optical path before the y-axis oscillation 前 for:

[0089]

[0090] Where, α yThe angle of inclination of the measured principal axis after deflection around the y-axis. L is the distance between the incident laser and the outgoing laser beam of the second pyramidal reflector b.

[0091] The optical path length S of the non-coincident optical path after y-axis oscillation 后 for:

[0092]

[0093] The expression for the optical path difference ΔS before and after the yaw is:

[0094]

[0095] When α x When L is 1 mm, ΔS θ (y) = 1.789 × 10 -11 The error is in mm, which is far below the measurement accuracy of a laser interferometer, so the error can be ignored.

[0096] 7-2. Analyze the influence of tilt angle error around the x-axis on axial error.

[0097] like Figure 6 As shown in the left part, assume that the vertex of the second pyramidal reflector b forms a characteristic plane with the incident laser; by intercepting the characteristic plane before and after the y-axis deflection, two triangles with different vertex angles can be obtained, thus creating an error in the optical path. However, the impact of this y-axis deflection error is much smaller than the impact of the y-axis deflection. Analysis shows that when the principal axis deflects α around the x-axis... x When the yaw is 5', the change in vertex angle θ is only 1.25 × 10⁻⁶. -5 The effect of the tilt angle error around the x-axis on the optical path difference is further calculated as follows:

[0098] Figure 6 The middle part is a side view of the left part. Assuming the incident points are on the same plane, and based on geometric relationships, the laser beam must pass through the center of the circle intersected by the plane of the incident point. Therefore, we have... Figure 6 The laser path trajectory shown on the right side is used to calculate the optical path S' of the trajectory as follows:

[0099]

[0100] Where, α x Let L be the yaw angle of the principal axis about the x-axis, L be the distance between the incident laser and the outgoing laser beam of the second pyramidal reflector b, and the optical path difference be:

[0101]

[0102] When α x When the value is 5' and L is 1mm, ΔS(x) = 1.0576 × 10 -6mm, meaning the optical path difference is in the nanometer range, which is negligible compared to the order of magnitude of the axial error.

[0103] 7-3. Analyze the influence of tilt angle error around the x-axis on radial error.

[0104] PSD sensor detection error caused by tilt angle error around the x-axis When L is 1 mm and 5' is used, the resulting measurement error is 0.727 micrometers, which is on the same order of magnitude as the measured physical quantity, and therefore cannot be ignored. Thus, the radial error X""θ" after separation of the spindle" i )as follows:

[0105] X"(g i )=X'(θ i )-ΔX

[0106] 7-5. Analyze the influence of radial error on the measurement of axial error.

[0107] When the spindle has radial error, its radial movement may also introduce errors into the measurement of axial error. For example... Figure 5 As shown ( Figure 5 The left side of the image represents the end view of the second pyramidal reflector b, and the right side is a sectional view of the conical mirror along the main axis. When the radial offset is Δx and Δy, since the entire mirror is conical, the incident point of the light rays is different when the main axis is radially offset, causing the reflected light rays to deflect as well. Therefore, the two outgoing light rays are not on the same plane. For ease of analysis, the offset light path plane is rotated back to the plane where the light path is located before offset, so that the two planes coincide.

[0108] Depend on Figure 5 As seen on the right side, the differences are only in segments AC, CA', B'D, and DB. However, because the selected reflecting mirror is a 90° conical mirror, theoretically ACA' and B'DB are two equal isosceles right triangles, so AC = A'C and B'D = BD. Therefore, the optical path length remains unchanged before and after the offset. From the above analysis, it can be concluded that the radial error of the principal axis does not affect the measurement of the axial error.

Claims

1. A method for measuring spindle runout error based on optical principle, characterized in that: The measuring device comprises a laser interferometer, a first corner cube reflector, a second corner cube reflector and a first beam splitter (1); the laser interferometer, the first beam splitter (1) and the second corner cube reflector are arranged along the axial direction of the main shaft to be measured in sequence; during the measurement, the second corner cube reflector is coaxially fixedly installed at the end of the main shaft to be measured; and the first corner cube reflector is installed at the side of the first beam splitter (1); The measuring device further comprises a second beam splitter (2) and a PSD sensor; the second beam splitter (2) is arranged between the laser interferometer and the second corner cube reflector; and the PSD sensor is arranged at the side of the second beam splitter (2); the reflecting surface of the second corner cube reflector is in the shape of a circular cone with a cone angle of 90°; The measuring device further comprises a ring-shaped plane mirror and a laser autocollimator; the ring-shaped plane mirror is fixed on the main shaft to be measured; and the laser autocollimator is installed on a rack and vertically faces the mirror surface of the ring-shaped plane mirror; The main shaft rotation error measurement method comprises the following steps: Step one: constructing a coordinate system on the vertical plane of the axial line of the main shaft to be measured; the main shaft to be measured is rotated, and the laser interferometer emits laser; At the same time when the laser interferometer emits laser, the laser autocollimator emits laser; the laser is reflected by the ring-shaped plane mirror and enters the detection area of the laser autocollimator; The coordinate system takes the direction perpendicular to the plane where the incident laser and the first split beam are located as the y-axis direction, and takes the direction perpendicular to the incident laser and the y-axis direction as the x-axis direction; Step two: detecting the main shaft rotation error; The laser forms standard light entering the detection area of the laser interferometer through the first beam splitter (1) and the first corner cube reflector; and forms test light entering the detection area of the laser interferometer through the second corner cube reflector; the standard light and the test light form interference fringes; Computing axial error of a measured spindle As follows: ； wherein is the amount of change in the number of interference fringes; is the wavelength of the laser light; n is the refractive index of air; The test light forms a second light beam at the second beam splitter (2); the second light beam enters the PSD sensor; while detecting the spindle axial error in step two, the spindle radial error is calculated As follows: ； ； wherein, is the average value of the x-axis coordinate of the spot position on the PSD sensor during one revolution of the main shaft being measured; is the average value of the y-axis coordinate of the spot position during one revolution of the main shaft being measured; is the coordinate of the spot position on the PSD sensor; Simultaneously detect the axial error and the radial error of the main shaft, and calculate the components of the inclination error of the main shaft in the x-axis direction and the y-axis direction , as follows: ； wherein, , are the components of the autocollimator reading in the x-axis direction, y-axis direction, respectively; , are the components of the mounting error of the annular mirror in the x-axis direction, y-axis direction, respectively; After obtaining the spindle radial error and the spindle tilt error, the spindle radial error is updated to ; wherein The expression of is as follows: ； Wherein, L is the distance between the incident laser and the reflected beam; the x-axis direction is parallel to the plane where the incident laser and the first split beam are located.

2. A laser-interference-based spindle runout error measuring device, characterized by: The main shaft rotation error measurement device is used for performing the main shaft rotation error measurement method as claimed in claim 1; the main shaft rotation error measurement device comprises a laser interferometer, a first corner cube reflector, a second corner cube reflector, a first beam splitter (1), a second beam splitter (2), a PSD sensor, a ring-shaped plane mirror and a laser autocollimator; the laser interferometer, the first beam splitter (1), the second beam splitter (2) and the second corner cube reflector are arranged along the axial direction of the main shaft to be measured in sequence; during the measurement, the second corner cube reflector is coaxially fixedly installed at the end of the main shaft to be measured; the first corner cube reflector is installed at the side of the first beam splitter (1); the PSD sensor is arranged at the side of the second beam splitter (2); the ring-shaped plane mirror is fixed on the main shaft to be measured; and the laser autocollimator is installed on a rack and vertically faces the mirror surface of the ring-shaped plane mirror; During the test, the incident laser emitted by the laser interferometer is incident into the second corner cube reflector through the first beam splitter (1); the incident laser forms a first split beam at the first beam splitter (1); the first split beam is reflected by the first corner cube reflector and then re-incident into the first beam splitter (1), and is reflected by the first beam splitter (1) and then shot to the detection area of the laser interferometer; the incident laser is reflected by the second corner cube reflector to form a reflected beam; the reflected beam is shot to the detection area of the laser interferometer and forms a second split beam at the second beam splitter (2); the second split beam is shot into the PSD sensor; the laser emitted by the laser collimator is reflected by the annular plane mirror and irradiates the laser collimator.

3. A laser-interference-based spindle-rotation-error measuring device according to claim 2, characterized in that: The film coating directions of the first beam splitter (1) and the second beam splitter (2) are all 45° angles with the laser emission direction.

4. The laser-interference-based spindle-rotation-error measuring device according to claim 2, characterized in that: The reflecting surface of the first corner cube reflector is a right angle L shape or a circular cone shape with a cone angle of 90°.

5. The laser-interference-based spindle-rotation-error measuring device according to claim 2, characterized in that: The incident laser is not coincident with the axis of the measured main shaft.

6. A laser-interference-based spindle-rotation-error measuring device according to claim 5, characterized in that: The distance between the straight line where the part of the first split beam incident into the first corner cube reflector is located and the tip of the first corner cube reflector is equal to the distance between the straight line where the incident laser is located and the tip of the second corner cube reflector in the initial state.

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