Measuring device in a small five-axis machine tool spatial error measurement system based on r-test

Abstract

The application discloses a measuring device in a small five-axis machine tool space error measurement system based on R-test, which comprises a tool holder, a shell and a center mounting frame. The center mounting frame is a I-shaped cylindrical component, which is divided into three sections, the front, middle and rear sections. The front section of the center mounting frame is the mounting part of the sensor. The middle section of the center mounting frame is a connecting column. The rear section of the center mounting frame is the connecting end of the tool holder. The shell is assembled from the rear section to the front section of the center mounting frame, and wraps the center mounting frame. The application solves the problems of the existing R-test device, such as difficult flexible adaptation to small five-axis machine tool automatic tool changing, insufficient structural rigidity and small measurement range, by designing an integrated overall structure (a non-contact measurement system with a I-shaped center frame as the core), realizes the characteristics of high integration, high rigidity and in-situ measurement of the device, and improves the measurement sensitivity, stability and measurement space size through sensor mounting pose optimization.

Description

Technical Field

[0001] This application belongs to the field of measurement device technology, specifically relating to a measurement device in a small five-axis machine tool spatial error measurement system based on R-test. Background Technology

[0002] A contact-type R-test measuring instrument, disclosed in CN119057567A, specifically includes a mounting ring with three sliding mechanisms slidably connected to it. Each moving mechanism is fixedly connected to a lifting mechanism, each lifting mechanism has a swing arm mechanism, each swing arm mechanism has a oscillating mechanism, each oscillating mechanism has a rotating mechanism, and each rotating mechanism has a telescopic mechanism. A contact displacement sensor is mounted on the telescopic end of each telescopic mechanism. A standard ball is positioned between the three contact displacement sensors and mounted on the rotating spindle tool holder of a machine tool. The positions of the three contact displacement sensors relative to the standard ball can be adjusted according to different measurement and algorithm requirements. However, it has the following technical drawbacks: the contact-type R-test measurement method suffers from decreased measurement accuracy due to wear during measurement; mounting the measuring ball on the spindle and the measuring device on the platform limits measurement to single-point measurement, making it unable to efficiently identify 41 geometric errors; and it does not provide a calibration method for sensor installation errors, affecting measurement accuracy. Summary of the Invention

[0003] In view of the shortcomings or deficiencies of the prior art, the technical problem to be solved by this application is to provide a measuring device in a small five-axis machine tool spatial error measurement system based on R-test.

[0004] To solve the above-mentioned technical problems, this application provides the following technical solution:

[0005] This application proposes a measuring device in a small five-axis machine tool spatial error measurement system based on R-test, including: a tool holder, a housing, and a central mounting bracket;

[0006] Wherein: the central mounting frame is an I-shaped cylindrical component, which is divided into three sections: front, middle and rear;

[0007] The front section of the central mounting bracket is the sensor mounting section;

[0008] The middle section of the central mounting frame is a connecting column;

[0009] The rear section of the central mounting bracket is the connecting end of the tool holder;

[0010] The outer casing is assembled from the rear to the front of the central mounting frame, enclosing the central mounting frame.

[0011] Optionally, the device also includes a battery compartment cover, which covers a battery compartment opening on the outer casing and can be opened when replacing the battery.

[0012] Further optionally, it also includes: a push-button switch mounting hole, the push-button switch mounting hole being disposed on the housing, the push-button switch mounting hole being used to mount a push-button switch.

[0013] Further optionally, it also includes: a first eddy current sensor, a second eddy current sensor, and a third eddy current sensor, which are respectively installed in the sensor mounting holes corresponding to the sensor mounting part at the front of the central mounting frame, and are respectively fixed by the first fixing plate, the second fixing plate, and the third fixing plate.

[0014] Further optionally, the first eddy current sensor, the second eddy current sensor, and the third eddy current sensor are evenly distributed on the central mounting bracket at an angle of 120°, and the axes of the first eddy current sensor, the second eddy current sensor, and the third eddy current sensor converge at a point, with an elevation angle α of 45°.

[0015] Further optionally, it also includes: a calibration method integrating the error parameters of the pose installation error and the spherical measurement error of the first eddy current sensor, the second eddy current sensor and the third eddy current sensor.

[0016] Further, optionally, it also includes: determining a measurement model, To measure the center of the ball, for The distance from point i to the measurement plane of the eddy current sensor. To measure the minimum distance between the spherical surface and the measurement plane of the i-th eddy current sensor, To measure the radius of the sphere, Let be the unit normal vector of the measurement plane of the i-th eddy current sensor. Let be the center point of the measurement plane of the i-th eddy current sensor, then we have Equation 1.

[0017] ;

[0018] Determine the error caused by eccentricity when using an eddy current sensor to measure a spherical surface. For the actual measurement results displayed by the sensor, , , Let be the error parameter of the i-th eddy current sensor. To measure the distance from the center of the sphere to the axis of the i-th eddy current sensor, we have Formula 2.

[0019] ;

[0020] And there is formula 3,

[0021] ;

[0022] , Determined by three parameters, plus , , Therefore, one sensor has nine parameters to be calibrated, and three sensors have a total of 27 parameters to be calibrated. A coordinate measuring machine is used to determine the precise coordinates of 100 measuring points in the measurement space. and corresponding sensor data Solve , as well as , , This completes the integrated calibration of the installation posture error and spherical measurement error of the above three sensors;

[0023] After calibration, the center of the sphere can be determined by applying the above formulas 1, 2, and 3, the calibration results of the error parameters, and the measurement data displayed by the eddy current sensor. The precise coordinates.

[0024] Further optionally, the small five-axis machine tool has 41 geometric errors, which can be identified by measuring the positional error of the machine tool at multiple measuring points.

[0025] Further, optionally, determine the Jacobian matrix of the sphere's center offset with respect to 41 geometric errors; determine the observability index: the sum of the reciprocals of the matrix's singular values;

[0026] The DETMAX algorithm is used to minimize the index, generating an optimized spatial distribution of the measurement sphere.

[0027] The specific steps are as follows:

[0028] Discretize the five-dimensional parameter space (x, y, z, c, a) of the machine tool to generate 78,650 candidate spatial measurement points;

[0029] Ten candidate measurement points were randomly selected as the initial subset;

[0030] Iterative optimization involves adding a point that minimizes the observability index from the candidate point set in each iteration and removing a point that has the least impact on the observability index, until the points to be added and removed are the same, at which point the iteration stops.

[0031] The final set of 10 measurement points is obtained, and the spatial distribution of the measurement sphere is generated based on the optimized set of 10 measurement points.

[0032] Compared with the prior art, this application has the following technical effects:

[0033] This application solves the problems of existing R-test devices, such as difficulty in flexibly adapting to automatic tool changing on small five-axis machine tools, insufficient structural rigidity, and small measurement range, by designing an integrated overall structure (a non-contact measurement system with an I-shaped center frame as the core). It achieves high integration, high rigidity, and in-situ measurement characteristics of the device, and improves measurement sensitivity, stability, and measurement space size by optimizing the sensor installation posture.

[0034] This application solves the key problem of decreased accuracy in sphere center calculation due to installation deviation and inherent sensor characteristics in non-contact measurement by designing an integrated calibration method (simultaneously solving for installation posture error and sensor spherical characteristic parameters), and achieves high-precision calculation of sphere center coordinates under complex real conditions.

[0035] This application solves the problem of errors caused by traditional regular distribution schemes of measuring points by designing multi-standard ball workpieces and optimizing the spatial distribution of measuring balls based on the DETMAX algorithm.

[0036] The measurement method proposed in this application, which involves mounting a measuring device on a swing head and measuring multiple standard spherical workpieces, enables rapid measurement at multiple measuring points and efficiently identifies 41 geometric errors of the machine tool. The integrated calibration method proposed in this application for installation errors and spherical measurement errors can effectively improve measurement accuracy. The non-contact method proposed in this application avoids the decrease in accuracy caused by wear. Attached Figure Description

[0037] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0038] Figure 1 : An overall structural diagram of a non-contact R-test measuring device according to an embodiment of this application;

[0039] Figure 2 : A structural diagram of a non-contact R-test measuring device with a concealed outer casing according to an embodiment of this application;

[0040] Figure 3 : A structural diagram of the central mounting frame in one embodiment of this application;

[0041] Figure 4 : A schematic diagram of the non-contact R-test measurement principle in one embodiment of this application;

[0042] Figure 5A schematic diagram of sensor installation error and spherical measurement error in one embodiment of this application;

[0043] Figure 6 An optimized distribution diagram of multiple standard spherical workpieces in one embodiment of this application.

[0044] Figure label:

[0045] 1-Handle;

[0046] 2-Outer shell;

[0047] 3-Battery compartment cover;

[0048] 4-Push-button switch;

[0049] 5-Center mounting bracket;

[0050] 6-First eddy current sensor;

[0051] 7-Second eddy current sensor;

[0052] 8-Third eddy current sensor;

[0053] 9-First fixing plate;

[0054] 10 - Second fixing plate;

[0055] 11-Third fixing plate;

[0056] 501 - Tool holder connection end;

[0057] 502 - Connecting Post;

[0058] 503 - Sensor mounting hole. Detailed Implementation

[0059] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0060] like Figures 1 to 3 As shown, in one embodiment of this application, the measuring device in the R-test-based small five-axis machine tool spatial error measurement system includes: a tool holder 1, a housing 2, and a central mounting bracket 5.

[0061] Wherein: the central mounting frame 5 is an I-shaped cylindrical component, which is divided into three sections: front, middle and rear;

[0062] The front section of the central mounting bracket 5 is the sensor mounting section;

[0063] The middle section of the central mounting frame 5 is a connecting column 502, which serves to connect the front and rear sections and ensure the rigidity of the overall structure.

[0064] The rear section of the central mounting bracket 5 is the tool holder connection end 501 of the tool holder 1, which serves to connect the tool holder 1 and enable the entire device to be installed on the machine tool swing head.

[0065] The outer shell 2 is assembled from the rear to the front of the central mounting frame 5, enclosing the central mounting frame 5 and providing protection.

[0066] This embodiment solves the problems of existing R-test devices, such as difficulty in flexibly adapting to automatic tool changing on small five-axis machine tools, insufficient structural rigidity, and small measurement range, by designing an integrated overall structure (a non-contact measurement system with an I-shaped central frame as the core). It achieves high integration, high rigidity, and in-situ measurement characteristics of the device, and improves measurement sensitivity, stability, and measurement space size by optimizing the sensor installation posture.

[0067] Furthermore, in this embodiment, a battery compartment cover 3 is also included. The outer shell 2 has a battery compartment hole, which is covered by the battery compartment cover 3. When replacing the battery, the battery compartment cover 3 can be opened to facilitate battery replacement.

[0068] Furthermore, in this embodiment, it also includes: a button switch mounting hole, which is disposed on the housing 2, and is used to install a button switch 4 for controlling the on / off state of the internal circuit.

[0069] Furthermore, in this embodiment, it also includes: a first eddy current sensor 6, a second eddy current sensor 7, and a third eddy current sensor 8, which are respectively installed in the sensor mounting holes 503 corresponding to the sensor mounting part at the front of the central mounting bracket 5, and are respectively fixed by a first fixing plate 9, a second fixing plate 10, and a third fixing plate 11.

[0070] In this embodiment, optionally, the first eddy current sensor 6, the second eddy current sensor 7, and the third eddy current sensor 8 are evenly distributed on the central mounting frame 5 at an included angle of 120°, and the axes of the first eddy current sensor 6, the second eddy current sensor 7, and the third eddy current sensor 8 converge at a single point, with an elevation angle α of 45°. Furthermore, the distance μ from the center point of the measuring plane of the first eddy current sensor 6, the second eddy current sensor 7, and the third eddy current sensor 8 to the axis of the central mounting frame 5 is 10.25 mm. These two parameters determine the mounting posture of the sensors and are optimized parameters, ensuring high measurement sensitivity and stability of the sensors, and also ensuring that the measuring device has a large measurement space.

[0071] In this embodiment, the distance to the measuring sphere is measured using the three eddy current sensors, and the coordinates of the sphere's center are calculated based on the measurement data from the three sensors. Due to factors such as installation errors of the eddy current sensors and errors caused by deviations from the sphere's axis during sphere measurement, the accuracy of the sphere's center calculation can be affected. Therefore, an integrated calibration method for 27 error parameters targeting both the eddy current sensor's pose installation error and the sphere measurement error was designed.

[0072] Specifically, this also includes: determining the measurement model, To measure the center of the ball, for The distance from point i to the measurement plane of the eddy current sensor. To measure the minimum distance between the spherical surface and the measurement plane of the i-th eddy current sensor, To measure the radius of the sphere, Let be the unit normal vector of the measurement plane of the i-th eddy current sensor. Let be the center point of the measurement plane of the i-th eddy current sensor, then we have Equation 1.

[0073] ;

[0074] Determine the error caused by eccentricity when using an eddy current sensor to measure a spherical surface. For the actual measurement results displayed by the sensor, , , Let be the error parameter of the i-th eddy current sensor. To measure the distance from the center of the sphere to the axis of the i-th eddy current sensor, we have Formula 2.

[0075] ;

[0076] And there is formula 3,

[0077] ;

[0078] , Determined by three parameters, plus , , Therefore, one sensor has nine parameters to be calibrated, and three sensors have a total of 27 parameters to be calibrated. A coordinate measuring machine is used to determine the precise coordinates of 100 measuring points in the measurement space. and corresponding sensor data Solve , as well as , , This completes the integrated calibration of the installation posture error and spherical measurement error of the above three sensors;

[0079] After calibration, the center of the sphere can be determined by applying the above formulas 1, 2, and 3, the calibration results of the error parameters, and the measurement data displayed by the eddy current sensor. The precise coordinates.

[0080] In this embodiment, the small five-axis machine tool has 41 geometric errors, which can be identified by measuring the positional error of the machine tool at multiple measuring points. A multi-standard spherical workpiece is designed for the small five-axis machine tool to measure the center positions of multiple standard spheres. The spatial error of the machine tool is identified based on the errors measured at multiple measuring points by the measuring device. An optimization method is designed to optimize the spatial distribution of the multiple measuring points, improving the efficiency of spatial error measurement and identification.

[0081] Specifically, determine the Jacobian matrix of the sphere's center offset with respect to 41 geometric errors; determine the observability index: the sum of the reciprocals of the matrix's singular values;

[0082] The DETMAX algorithm is used to minimize the index, generating an optimized spatial distribution of the measurement sphere.

[0083] The specific steps are as follows:

[0084] Discretize the five-dimensional parameter space (x, y, z, c, a) of the machine tool to generate 78,650 candidate spatial measurement points;

[0085] Ten candidate measurement points were randomly selected as the initial subset;

[0086] Iterative optimization involves adding a point that minimizes the observability index from the candidate point set in each iteration and removing a point that has the least impact on the observability index, until the points to be added and removed are the same, at which point the iteration stops.

[0087] The final set of 10 measurement points is obtained, and the spatial distribution of the measurement sphere is generated based on the optimized set of 10 measurement points.

[0088] This application addresses the limitations of existing R-test devices, such as their inability to flexibly adapt to automatic tool changing on small five-axis machine tools, insufficient structural rigidity, and small measurement range, by designing an integrated overall structure (a non-contact measurement system with an I-shaped center frame as its core). It achieves high integration, high rigidity, and in-situ measurement characteristics, and improves measurement sensitivity, stability, and measurement space size through sensor installation posture optimization. Furthermore, this application solves the key problem of decreased accuracy in sphere center calculation due to installation deviations and inherent sensor characteristics in non-contact measurement by designing an integrated calibration method (simultaneously solving for installation posture errors and sensor spherical characteristic parameters), achieving high-precision calculation of sphere center coordinates under complex real-world conditions. Finally, this application addresses the problem of low error identification efficiency caused by traditional regular distribution schemes of measurement points by designing multiple standard spherical workpieces and optimizing the spatial distribution of the measurement spheres based on the DETMAX algorithm, significantly improving the overall identification accuracy and solution efficiency of geometric error parameters. In summary, this application has broad market application prospects.

[0089] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0090] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0091] In the description of this embodiment, the terms "upper," "lower," "left," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0092] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. The preferred embodiments have been described in detail. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the claims of this application.

Claims

1. A calibration method for the integrated error parameters of the measuring device in a small five-axis machine tool spatial error measurement system based on R-test, characterized in that, The error parameters include: errors of pose installation error and spherical measurement error; and the calibration method includes: determining a measurement model, For measuring the sphere center, For The distance between the point and the measurement plane of the i-th eddy current sensor, For measuring the minimum distance between the sphere and the measurement plane of the i-th eddy current sensor, For measuring the sphere radius, The unit normal vector of the measurement plane of the i-th eddy current sensor, The center point of the measurement plane of the i-th eddy current sensor, and the formula 1 is as follows, ； determining the error caused by eccentricity when measuring a spherical surface with an eddy current sensor, measuring the actual display result for the sensor, 、 、 error parameter for the i-th eddy current sensor, is the distance from the center of the measuring ball to the axis of the i-th eddy current sensor, then there is formula 2, ； And there is formula 3, ； , are determined by three parameters respectively, plus , , Therefore, one sensor has nine parameters to be calibrated, and three sensors have 27 parameters to be calibrated. The accurate coordinates of 100 measuring points in the measuring space are measured by using a three-coordinate measuring instrument and the corresponding sensor data , solve , and , , Thus, the integrated calibration of the installation pose error and the spherical measurement error of the above three sensors is completed. After the calibration is completed, the accurate coordinates of the ball center can be solved according to the above formula 1, formula 2, formula 3, error parameter calibration results and the measurement data displayed by the eddy current sensor . Wherein, the sensor comprises: a first eddy current sensor, a second eddy current sensor and a third eddy current sensor, which are respectively installed in the sensor mounting hole corresponding to the mounting part of the sensor of the front section of the center mounting frame, and the first eddy current sensor, the second eddy current sensor and the third eddy current sensor are fixed by the first fixed plate, the second fixed plate and the third fixed plate.

2. The calibration method of claim 1, wherein Also includes: Handle, shell and center mounting frame; Wherein: the center mounting frame is a H-shaped cylindrical member, which is divided into three sections of front, middle and rear; The front section of the center mounting frame is the mounting part of the sensor; The middle section of the center mounting frame is a connecting column; The rear section of the center mounting frame is the connecting end of the handle; The shell is assembled from the rear section to the front section of the center mounting frame, wrapping the center mounting frame.

3. The calibration method of claim 2, wherein, Also includes battery compartment cover, the shell is provided with battery compartment hole, which is covered by the battery compartment cover, when replacing the battery, the battery compartment cover can be opened.

4. The calibration method of claim 2, wherein Also includes: Button switch mounting hole, the button switch mounting hole is provided on the shell, and the button switch mounting hole is used for installing the button switch.

5. The calibration method of claim 1, wherein The first eddy current sensor, the second eddy current sensor and the third eddy current sensor are uniformly distributed on the center mounting frame with an included angle of 120°, and the axes of the first eddy current sensor, the second eddy current sensor and the third eddy current sensor converge at a point, and the elevation angle α of the axis is 45°.

6. The calibration method of claim 1, wherein The small five-axis machine tool has 41 geometric errors, which can be identified by measuring the position error of the machine tool at multiple measuring points.

7. The calibration method of claim 6, wherein, Determine the Jacobian matrix of the ball center offset with respect to the 41 geometric errors; determine the observability index: the reciprocal of the singular value of the matrix; Use the DETMAX algorithm to minimize the index to generate the optimized spatial distribution of the measuring ball.

8. The calibration method of claim 7, wherein, The specific steps are: Discretize the five-dimensional parameter space (x, y, z, c, a) of the machine tool to generate 78650 candidate spatial measuring points; Randomly select 10 candidate measuring points as the initial subset; Iterative optimization, each iteration adds a point that minimizes the observability index from the candidate point set and removes a point that has the least impact on the observability index, until the added point and the removed point are the same, stop iteration; Obtain the final set of 10 measuring points, and generate the spatial distribution of the measuring ball according to the optimized 10 measuring points.

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