A method and apparatus for high-precision separation and measurement of spindle rotation error

Abstract

This invention relates to the field of CNC machine tool spindle accuracy testing and error separation technology, specifically to a high-precision measurement method and device for spindle rotation error separation. The high-precision measurement method for spindle rotation error separation includes the following steps: data acquisition under any angle combination; solving for the optimal angle; acquiring data at the optimal angle and removing installation errors; and performing error separation based on the optimized three-point method from the data after removing installation errors to obtain the rotation error and the bar shape error. The high-precision measurement device for spindle rotation error separation includes a base, an annular guide slide assembly, a sensor slide assembly, a bar, a worm gear fine-tuning assembly, and a locking device. This invention enables rapid adjustment of the three-sensor angle combination, effectively reducing the ill-conditioning and noise amplification of the three-point method separation, improving the stability and reliability of the separation of spindle rotation error and bar shape error, and providing technical support for the engineering measurement and evaluation of machine tool spindle rotation accuracy.

Description

Technical Field

[0001] This invention relates to the field of CNC machine tool spindle accuracy testing and error separation technology, specifically to a high-precision separation and measurement method and device for spindle rotation error. Background Technology

[0002] CNC machine tools play a crucial role in equipment manufacturing, aerospace, and semiconductor industries. The spindle system is considered the "heart" of the machine tool, and its rotational error—the offset of the actual spindle axis from the ideal axis—is one of the most critical factors affecting the overall performance of the machine tool. During precision machining and measurement, the spindle's rotational error changes with speed, load, and temperature rise under the combined effects of cutting force, centrifugal force, bearing preload, and thermal load, leading to deviations in the relative position of the tool and workpiece. This, in turn, causes deviations in workpiece roundness, cylindricity, and coaxiality, resulting in surface ripples, vibration noise, and decreased machining stability. In extreme cases, it may even induce abnormal bearing wear, rotor rubbing, and fatigue failure. Therefore, accurate measurement of spindle rotational error is of great significance for improving the accuracy retention, reliability, and service life of CNC machine tools.

[0003] Currently, considerable research has been conducted on measurement devices and methods for spindle rotation errors. Patent CN104482849A discloses a spindle dynamic rotation accuracy testing system and method, which uses an industrial control computer acquisition card and encoder, and arranges multiple capacitive displacement sensors on a ball bar structure to achieve spindle dynamic rotation accuracy testing and synchronous / asynchronous error calculation. Patent CN117428571A discloses a machine tool spindle rotation error detection device, which uses a lifting drive and radial positioning structure, positioning disk, and other mechanisms to align and position the spindle and arrange retractable sensors for detection. Patent CN117890105A discloses an ultra-precision spindle measurement method based on a fusion three-point error separation technology. Three displacement sensors are installed radially around a test bar, and the roundness profile of the test bar and the radial dynamic rotation error of the spindle in the X / Y directions are separated based on a three-point method model. An example is given showing how to set the sensor angle. Patent CN121008535A discloses a spindle radial rotation error separation method based on a multi-point approach. It establishes an error separation model by collecting data from X / Y displacement sensors and proposes a method to eliminate sensor installation offset errors and probe roundness errors to obtain a "pure spindle radial rotation error." This includes an implementation route that uses algorithms such as CEEMDAN to eliminate offset errors. Patent CN121140695A discloses a spindle rotation error detection device and calculation method. It uses an arc-shaped tooling and an annular cover / shell to form a clamping structure. A detection component consisting of upper and lower standard balls is installed at the top of the spindle, and multiple detectors are arranged on the shell to acquire radial distance data for error calculation and identification.

[0004] Analysis of existing research on spindle rotation error testing reveals the following: (1) The dual-sensor orthogonal method is currently the mainstream method for spindle rotation error testing, but this method relies on high-precision test bars and cannot eliminate the influence of test bar shape error on the test results; (2) Existing three-point separation methods often use preset angles, but lack an adaptive determination mechanism for the "optimal angle combination" under different machine tool structure avoidance, different harmonic ranges of concern, and different noise levels; (3) There is a lack of an angle-adjustable mechanism that can achieve rapid coarse positioning and high-precision fine adjustment, and ensure repeatable positioning, making it difficult to stably implement angle optimization even if it is valid at the algorithm level. Based on this, this invention proposes a high-precision separation measurement method and device for spindle rotation error, which significantly reduces separation ill-conditioning and noise amplification, and improves the separation accuracy and robustness of test bar shape error and spindle rotation error. Summary of the Invention

[0005] This invention provides a method and apparatus for high-precision separation measurement of spindle rotation error. It optimizes the installation angle of the sensor in the three-point method and realizes rapid adjustment and locking of the angle through the testing device, thereby significantly reducing separation ill-conditioning and noise amplification, and improving the separation accuracy and robustness of probe shape error and spindle rotation error.

[0006] To solve the above-mentioned technical problems, the invention provides the following technical solution: a high-precision separation and measurement method for spindle rotation error, comprising the following steps:

[0007] Step 1: Collect data from any combination of angles;

[0008] Step two: Calculate the optimal angle based on the collected data. The specific method is as follows:

[0009] In the target harmonic set An angle combination stability index is constructed based on the three-point method to separate the equations, and the optimal angle combination is obtained by solving the equations. ;

[0010] Among them, the first The three-point separation equation in the first harmonic domain is:

[0011]

[0012]

[0013]

[0014] in, This represents the measurement complex coefficients of the three radial displacement sensors at the nth order. Represented by angle vector The determined error separation matrix; This represents the nth-order true error vector. The nth harmonic of the test bar shape error; It is the nth order of the spindle rotation error in the X direction; It is the nth order of the spindle rotation error in the Y direction; j The imaginary unit is represented; the angle of the radial displacement sensor relative to the X direction is... , ;

[0015] Noise amplification Minimization is used as the criterion to determine the optimal angle combination, minimizing the following expression:

[0016]

[0017] in, For the target frequency band weight, It is the smallest singular value;

[0018]

[0019] in, The permissible angle range of the measuring device. Minimum included angle constraint between radial displacement sensors; This represents the angular difference between radial displacement sensors.

[0020] Step 3: Collect data at the optimal angle and remove installation errors from it;

[0021] Step four: From the data after removing installation errors, error separation is performed based on the optimized three-point method to obtain the rotation error and the test bar shape error.

[0022] Step one specifically involves:

[0023] Adjust the measuring device so that the three radial displacement sensors are positioned at any angle combination. Acquire three-path displacement signals during the spindle rotation process. ,in, The main axis rotation angle, and Establish measurement relationships based on the three-point superposition model:

[0024]

[0025] in, This indicates the error in the shape of the standard sphere measured by the radial displacement sensor at the current position. spindle rotation error Directional components, spindle rotation error Directional components, For noise and unmodeled error, The angle of the radial displacement sensor relative to the X direction; extracting the target harmonic set from the three-path displacement signal data. .

[0026] The specific method for step three is as follows:

[0027] Harmonic complex coefficients are extracted once from the displacement signals along each path acquired at the optimal angle. Constructing the first harmonic component ;

[0028]

[0029] in, This indicates that after performing a Fourier transform on the radial displacement signal, the complex coefficients of the first harmonic are extracted. Representing complex numbers The phase angle is the phase offset of the first harmonic in the angular domain; Indicates the magnitude of the complex coefficient of the first harmonic;

[0030] The first harmonic component is removed from the radial displacement signal obtained based on the optimal angle measurement to obtain the signal after removing the first harmonic component. ;

[0031] The For subsequent Stable separation.

[0032] The specific method for error separation based on the optimized three-point method in step four is as follows:

[0033] optimal angle combination After acquiring the signal and eliminating installation errors, Harmonic decomposition yields ,exist Above, by Composition vector , ; This indicates that the optimal angle vector is used. The determined error separation matrix;

[0034] The nth harmonic of the probe shape error at the optimal angle is obtained by regularized least squares solution. The nth order of spindle rotation error in the X direction at the optimal angle The nth order of the spindle rotation error in the Y direction at the optimal angle :

[0035]

[0036] express The square of the second norm;

[0037] Where λ is the regularization parameter;

[0038]

[0039] in, For the shape error of the test bar, Main spindle rotation error X-direction component The X-direction component of the spindle rotation error.

[0040] A high-precision separation and measurement device for spindle rotation error, employing a high-precision separation and measurement method for spindle rotation error, includes a base, an annular guide slide rail assembly, a sensor slide assembly, a probe, a worm gear fine-tuning assembly, and a locking device, used to adjust the circumferential angular position of a radial displacement sensor in a three-point method measurement. The annular guide slide rail assembly is located on an annular structure on the upper part of the base, with its surface forming a slide rail, creating a guide channel along the circumferential direction. The sensor slide assembly is mounted on the annular guide slide rail assembly and moves circumferentially along the slide rail. A sensor mount is installed on the slide of the sensor slide assembly. The mounting base is used to install the radial displacement sensor and keep the probe facing the test bar surface; by pushing the slide along the slide rail, the radial displacement sensor is quickly moved to the vicinity of the target angle, realizing rapid coarse positioning of the three-point angle combination; the worm gear fine adjustment assembly includes a worm and a ring gear meshing with it. The worm is driven by a handle to cause the ring gear meshing with it to produce angular displacement, thereby driving the sensor slide assembly to make a small angle adjustment in the circumferential direction; the locking device is set between the sensor slide assembly and the base, and is used to lock the position of the slide and the angle position after the angle adjustment is completed.

[0041] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0042] (1) This invention proposes a high-precision separation measurement method for spindle rotation error, which covers the initial measurement of arbitrary angle, extraction of target harmonic frequency band, construction of angle combination stability index and solution of optimal angle, removal of first harmonic and optimization of three-point method error separation and evaluation, etc. It can effectively suppress separation ill-conditioning and noise amplification within the target frequency band, and realize synchronous, fast and robust separation measurement of spindle rotation error and probe shape error.

[0043] (2) Based on the above measurement method, this invention is designed to meet the engineering implementation requirements of angle optimization. It is a high-precision separation measurement device for spindle rotation error that is adjustable from 0° to 360°. It adopts an angle adjustment structure of "circular arc slide rail for rapid positioning and worm gear for precise fine adjustment" to realize the rapid switching and precise fine adjustment of the angular positions of the three radial displacement sensors, providing reliable hardware support for the realization of the optimal angle combination and stable measurement. Attached Figure Description

[0044] Figure 1 This is a flowchart of a high-precision separation and measurement method for spindle rotation error.

[0045] Figure 2 This is a schematic diagram of a high-precision separation and measurement device for spindle rotation error.

[0046] Figure 3 The simulation diagram is based on the optimized three-point method for error separation; (a) is the test bar shape error; (b) is the main shaft error.

[0047] In the diagram: 1. Base; 2. Annular guide rail assembly; 3. Sensor slide assembly; 4. Inspection bar; 5. Worm gear fine-tuning assembly; 6. Locking device. Detailed Implementation

[0048] The following detailed, non-limiting description of the technical solution of the present invention, in conjunction with preferred embodiments and accompanying drawings, is provided. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0049] The following describes the implementation of the "High-precision Separation and Measurement Method and Device for Spindle Rotation Error" of the present invention, taking the measurement of spindle rotation error of a vertical machining center as an example.

[0050] The high-precision separation and measurement device for spindle rotation error of the present invention is fixed on the machine tool worktable or a special bracket. The probe 4 is installed on the end of the machine tool spindle and rotates synchronously with the spindle. Three radial displacement sensors are installed on the sensor mounting base of the high-precision separation and measurement device for spindle rotation error, with the probes facing the probe 4. The angle adjustment process in this embodiment includes: after loosening the locking device 6, moving the slide along the annular slide rail and then moving each sensor mounting base to make the sensor angular position close to the target angle, achieving rapid positioning; then, making a small adjustment to the diagonal position through the worm gear fine-tuning component 5 to achieve precise fine-tuning; after adjusting to the target angle, activating the locking device 6 to fix the slide position, completing the stable maintenance of the angle position. The above process can realize the switching and reproduction of the angle combination of the three radial displacement sensors, providing device support for the subsequent implementation of the optimal angle combination.

[0051] Step 1: Collect data from any combination of angles;

[0052] The three radial displacement sensors can be quickly positioned and locked using a slide rail, allowing them to be combined at any feasible angle. Start the spindle and acquire the three-path displacement signals of the spindle rotation, denoted as . ,in Main axis rotation angle, A measurement model is established based on the fundamental superposition principle of the three-point method:

[0053]

[0054] in: This indicates the error in the shape of the standard sphere measured by the radial displacement sensor at the current position. spindle rotation error Directional components, spindle rotation error Directional components; This represents noise and unmodeled error.

[0055] Target harmonic frequency band information is extracted from initial measurement data at any angle for subsequent angle optimization. For the first... First harmonic wave is defined by complex coefficients:

[0056]

[0057] And determine the target harmonic set:

[0058]

[0059] Simultaneously construct weights of each order :

[0060]

[0061] In equation (3), the default is from It started because There is a three-point separation degradation, see step three for details.

[0062] Step 2: Determine the optimal angle based on the collected data;

[0063] An angle combination stability index is constructed based on the three-point method separation matrix, and the optimal angle combination is solved by combining the target harmonic frequency band information obtained in step one. .

[0064] For equation (1) in the first In the first harmonic domain, we can obtain:

[0065]

[0066] Written in matrix form:

[0067]

[0068] in,

[0069]

[0070]

[0071] The optimal angular stability criterion is proposed: minimizing noise amplification. This is because error separation is highly sensitive to noise amplification. Related, and Therefore, the objective function is defined as follows:

[0072]

[0073] Equation (9) means that within the target harmonic set of interest, we should try to avoid the occurrence of "singular / near-singular" at a certain order, so as to fundamentally suppress the abnormal amplification of the separation results.

[0074] Meanwhile, the angle optimization device can achieve constraints:

[0075]

[0076] Solving equation (9) for the optimal solution under constraint (10), we obtain... Then, the locking device 6 is released, and the radial displacement sensor is quickly moved along the slide rail to near the optimal angle. Then, a precise fine-tuning is performed using a worm gear. And lock it in place, completing the data acquisition at the optimized angle. For the optimal angle The solution employs an adaptive grid search algorithm, which can stably obtain the optimal solution under non-convex and non-smooth objective function conditions. Due to the objective function in equation (9)... It is only related to the relative angular relationship between the three radial displacement sensors. The simultaneous translation of the overall angle does not change the singular value structure of the matrix, so it is preferable to use... Fixed as reference angle Only for Perform a search.

[0077] Step 3: Collect data at the optimal angle and remove installation errors;

[0078] The error component caused by installation errors mainly manifests as the first harmonic, and in the three-point method model, it is related to... The presence of correlation can easily lead to the degradation of the separation model and cause amplification. Therefore, in this embodiment, it is preferable to perform harmonic removal once before error separation.

[0079] Extract the harmonic complex coefficients once for each path displacement signal:

[0080]

[0081] This represents the amplitude of the first harmonic complex coefficient of the radial displacement signal;

[0082] Constructing the first harmonic component:

[0083]

[0084] And remove it from the original radial displacement signal:

[0085]

[0086] Obtain the signal after removing the first harmonic component. For subsequent Stable separation.

[0087] Step 4: Error separation based on the optimized three-point method;

[0088] The optimal angle combination obtained in step two The three-way displacement signals were collected and the installation error removal step three was performed to obtain the results. Harmonic decomposition of it yields and in (Preferred) ) on the build:

[0089]

[0090] This embodiment preferably uses regularized least squares to solve the problem:

[0091]

[0092] Its closed-form solution is:

[0093]

[0094] Thus, the various orders are obtained. This allows for the reconstruction of the gyration error components.

[0095]

[0096] The final output includes the rotation error trajectory and the corresponding evaluation results.

[0097] The present invention further explains that the high-precision separation and measurement device for spindle rotation error consists of a base 1, an annular guide slide rail assembly 2, a sensor slide assembly 3, a test bar 4, a worm gear fine-tuning assembly 5, and a locking device 6. It is used to adjust the circumferential angular position of the radial displacement sensor in the three-point method measurement. The rapid positioning relies on the slide rail, the precise fine-tuning relies on the worm gear, and the angular position is fixed by the locking device after the adjustment is completed.

[0098] The invention further describes that the annular guide rail assembly 2 is disposed on the annular structure at the top of the device, forming a guide channel along the circumferential direction; the sensor slide assembly 3 is mounted on the annular guide rail and can move circumferentially along the rail, and a sensor mounting seat is provided on the slide for mounting the radial displacement sensor and keeping the probe facing the surface of the probe. By pushing the slide along the rail, the radial displacement sensor can be quickly moved to the vicinity of the target angle, realizing rapid coarse adjustment positioning using the three-point angle combination method.

[0099] The present invention further explains that the worm gear fine-tuning component 5 includes a worm and a meshing annular gear ring. The worm is driven by a handle to cause a slight angular displacement in the meshing annular gear ring, thereby driving the sensor slide assembly 3 to make a slight angular adjustment in the circumferential direction. Compared with the coarse adjustment method of the slide rail, the worm gear transmission has the characteristics of high adjustment resolution and strong controllability. It can be used to precisely adjust the sensor angular position to near the calculated optimal angle combination, realizing precise alignment of the three-point method in angle error-sensitive scenarios.

[0100] The present invention further explains that the locking device is disposed between the sensor slide assembly 3 and the base 1 to lock the slide position and angle position after the angle adjustment is completed, preventing angle drift caused by vibration or external force during the measurement process. The locking method adopts the form of a fastening screw, so that the sensor angular position remains stable during the measurement.

[0101] The invention further explains that, in use, the device first moves the sensor slide assemblies 3 on the slide rail to achieve rapid positioning, so that the radial displacement sensors roughly reach the expected angle distribution; then, precise fine-tuning is performed through the worm gear fine-tuning assembly 5 to adjust the angular position to the target angle combination; finally, the locking device 6 is activated to complete the fixation, and subsequent data acquisition and error separation calculation are performed. This structure enables the device to simultaneously possess both "rapid angle adjustment" and "fine angle adjustment" capabilities, and maintains angle stability after locking, meeting the engineering implementation requirements of the three-point angle optimization method.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-precision separation and measurement method for spindle rotation error, characterized in that, Includes the following steps: Step 1: Collect data from any combination of angles; Step two: Calculate the optimal angle based on the collected data. The specific method is as follows: In the target harmonic set An angle combination stability index is constructed based on the three-point method to separate the equations, and the optimal angle combination is obtained by solving the equations. ; Among them, the first The three-point separation equation in the first harmonic domain is: in, This represents the measurement complex coefficients of the three radial displacement sensors at the nth order. Represented by angle vector The determined error separation matrix; This represents the nth-order true error vector. The nth harmonic of the test bar shape error; It is the nth order of the spindle rotation error in the X direction; It is the nth order of the spindle rotation error in the Y direction; j The imaginary unit is represented; the angle of the radial displacement sensor relative to the X direction is... , ; Noise amplification Minimization is used as the criterion to determine the optimal angle combination, minimizing the following expression: in, For the target frequency band weight, It is the smallest singular value; in, The permissible angle range of the measuring device. Minimum included angle constraint between radial displacement sensors; This indicates the angular difference between radial displacement sensors; Step 3: Collect data at the optimal angle and remove installation errors from it; Step four: From the data after removing installation errors, error separation is performed based on the optimized three-point method to obtain the rotation error and the test bar shape error.

2. The high-precision separation and measurement method for spindle rotation error according to claim 1, characterized in that, Step one specifically involves: Adjust the measuring device so that the three radial displacement sensors are positioned at any angle combination. Acquire three-path displacement signals during the spindle rotation process. ,in, The main axis rotation angle, and Establish measurement relationships based on the three-point superposition model: in, This indicates the error in the shape of the standard sphere measured by the radial displacement sensor at the current position. spindle rotation error Directional components, spindle rotation error Directional components, To account for noise and unmodeled errors; extract the target harmonic set from three-path displacement signal data. .

3. The high-precision separation and measurement method for spindle rotation error according to claim 2, characterized in that, The specific method for step three is as follows: Harmonic complex coefficients are extracted once from the displacement signals along each path acquired at the optimal angle. Constructing the first harmonic component ; in, This indicates that after performing a Fourier transform on the radial displacement signal, the complex coefficients of the first harmonic are extracted. Representing complex numbers The phase angle is the phase offset of the first harmonic in the angular domain; Indicates the magnitude of the complex coefficient of the first harmonic; The first harmonic component is removed from the radial displacement signal obtained based on the optimal angle measurement to obtain the signal after removing the first harmonic component. ; The For subsequent Stable separation.

4. The high-precision separation and measurement method for spindle rotation error according to claim 3, characterized in that, The specific method for error separation based on the optimized three-point method in step four is as follows: optimal angle combination After acquiring the signal and eliminating installation errors, Harmonic decomposition yields ,exist Above, by Composition vector , ; This indicates that the optimal angle vector is used. The determined error separation matrix; The nth harmonic of the probe shape error at the optimal angle is obtained by regularized least squares solution. The nth order of spindle rotation error in the X direction at the optimal angle The nth order of the spindle rotation error in the Y direction at the optimal angle : express The square of the second norm; Where λ is the regularization parameter; in, For the shape error of the test bar, Main spindle rotation error X-direction component The X-direction component of the spindle rotation error.

5. A high-precision separation and measurement device for spindle rotation error, characterized in that, The high-precision separation measurement method for spindle rotation error according to any one of claims 1-4 includes a base (1), an annular guide slide rail assembly (2), a sensor slide assembly (3), a probe (4), a worm gear fine-tuning assembly (5), and a locking device (6), used to adjust the circumferential angle position of the radial displacement sensor in the three-point method measurement; the annular guide slide rail assembly (2) is located on the annular structure on the upper part of the base (1), and its surface is a slide rail, forming a guide channel along the circumferential direction; the sensor slide assembly (3) is installed on the annular guide slide rail assembly (2) and moves circumferentially along the slide rail; the slide of the sensor slide assembly (3) is provided with The sensor mounting base is used to install the radial displacement sensor and keep the probe facing the surface of the probe (4); by pushing the slide along the slide rail, the radial displacement sensor is quickly moved to the vicinity of the target angle to achieve rapid coarse positioning of the three-point angle combination; the worm gear fine adjustment assembly (5) includes a worm and a ring gear meshing with it. The worm is driven by the handle to cause the ring gear meshing with it to produce angular displacement, thereby driving the sensor slide assembly (3) to make a small angle adjustment in the circumferential direction; the locking device (6) is set between the sensor slide assembly (3) and the base (1) to lock the slide position and angle position after the angle adjustment is completed.

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