Linear laser on-machine measurement tooling and pose calibration method

Abstract

The present disclosure provides a line laser on-machine measurement tool and a pose calibration method thereof. The tool comprises a spindle clamping module and a line laser sensor arranged at the center of the line laser on-machine measurement tool, an upper connecting plate and a lower connecting plate connected by the spindle clamping module, a plurality of pose adjustment knobs uniformly arranged between the upper and lower connecting plates, and a power supply and a communication module arranged on one side of the lower connecting plate. The installation pose error of the tool includes error components θ T (x), θ T (y), θ s and displacement error components δ T (x), δ T (y) of the line laser sensor around the X, Y and Z axes of the line laser coordinate system. The calibration method uses a standard gauge block installed on the spindle of the machine tool, then calibrates each error component and calculates the virtual tool length of the line laser sensor, and finally compensates for the installation pose error of the tool according to the calibrated error components and the virtual tool length. The pose adjustment of the tool is accurate and portable, and the accuracy of the line laser sensor on-machine measurement can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of line laser measurement technology, specifically to a line laser in-machine measurement fixture and its pose calibration method. Background Technology

[0002] To improve the machining accuracy of complex curved surfaces, it is necessary to inspect the machining quality during five-axis machining. In-machine measurement has become an essential process for high-precision machining of complex curved surfaces. Compared with coordinate measuring machine (CMM), in-machine measurement is widely used in the machining of complex parts due to its significant advantages of significantly reducing secondary clamping time and integrating machining and measurement. Although contact measurement has high accuracy, its single-point touch measurement mode limits its inspection efficiency, which cannot meet the requirements of full-size accurate measurement of large-sized, multi-feature industrial parts in industrial scenarios. Compared with contact probes, line laser sensors can measure a large number of data points in a single measurement, and the measurement frequency is much higher than that of contact measurement. Although not yet included in ISO standards, the use of line laser sensors to replace contact probes has become a trend in recent years, greatly improving measurement efficiency.

[0003] Integrating line laser sensors with five-axis machine tools can fully leverage the high efficiency, high precision, and stable measurement capabilities of line lasers, as well as their immunity to surface reflections from milling processes. However, due to the lack of international technical standards, integrating line laser sensors into machine tools still presents numerous challenges. Line lasers are inherently two-dimensional laser sensors, requiring the movement of the machine tool to achieve three-dimensional measurement. The five-axis machine tool's measurement motion alters both the measurement position and direction of the line laser, enabling the detection of complex curved surface contours. The on-machine measurement accuracy of line laser sensors depends not only on the sensor's measurement accuracy but also on the mounting accuracy of the line laser on the five-axis machine tool. Therefore, designing a high-precision on-machine measurement fixture for line lasers and calibrating and compensating for the line laser's clamping posture are crucial for achieving high-precision on-machine measurement with line lasers.

[0004] Although some scholars have proposed a method for calibrating the installation posture error of a line laser based on a standard sphere (Bi, C., et al., Extrinsic calibration of a laser displacement sensor in a non-contactcoordinate measuring machine. Chinese Journal of Aeronautics, 2017, 30(4): p. 1528-1537.), in reality, due to the large measurement error of the line laser itself and the low accuracy of the small-range sphere center fitting algorithm, the actual standard sphere fitting radius and sphere center position error are difficult to be less than 0.02 mm, resulting in low calibration accuracy of the installation posture error of the line laser.

[0005] For example, patent CN 209978833 U discloses a fixture for fixing a line laser profile scanner, used for mounting a line laser sensor on a machine tool. However, this fixture lacks pose adjustment functionality and is only applicable to three-axis CNC machine tools. Patent document CN110530296 A discloses a method for identifying the pose error angle of a line laser sensor installation. However, this method uses a honeycomb core of a hexagonal structural unit as a standard part and involves multiple scanning measurements, making the process relatively cumbersome. Patent document CN 111060025A discloses a pose calibration method for in-situ mounting of a line laser sensor on a five-axis machine tool. However, this method requires multiple measurements along the A-axis and the extraction of circular feature points, resulting in a large computational load. Summary of the Invention

[0006] This disclosure aims to at least partially address one of the technical problems in the related art.

[0007] Therefore, this disclosure provides a method for calibrating the pose of a line laser in-machine measurement fixture. This fixture, in conjunction with a line laser, enables in-machine measurement, allowing for stable and reliable clamping, and its pose adjustment is portable and precise. The pose calibration method utilizes standard gauge blocks to quickly calibrate the installation pose error of the line laser, thereby improving the accuracy of in-machine measurement of the line laser sensor.

[0008] To achieve the above objectives, the present disclosure adopts the following technical solution:

[0009] The first aspect of this disclosure provides a line laser in-machine measurement fixture, including a spindle clamping module, an upper connecting plate, a lower connecting plate, a line laser sensor, a power supply, a communication module, and several pose adjustment knobs. A line laser coordinate system is defined, with the origin being the laser emission point of the line laser sensor, the X-axis being the movement direction of the line laser sensor, the Y-axis being the positive direction of the measurement line measured by the line laser sensor each time, and the Z-axis being the emission laser direction of the line laser sensor.

[0010] The spindle clamping module is located at the center of the line laser in-machine measurement fixture, and is used to connect the upper connecting plate and the lower connecting plate to the machine tool spindle tool holder, and allows a small rotation of the Z-axis of the line laser coordinate system between the upper connecting plate and the lower connecting plate.

[0011] Several pose adjustment knobs are evenly distributed between the upper connecting plate and the lower connecting plate to adjust the rotation angle of the line laser sensor around the X-axis and Y-axis of the line laser coordinate system.

[0012] The line laser sensor is located at the center of the line laser in-machine measurement fixture and on the side of the lower connecting plate facing away from the machine tool spindle, and is used to measure the contour of the workpiece on the machine tool.

[0013] The power supply is located on the side of the lower connecting plate facing away from the machine tool spindle, and is used to power the line laser sensor;

[0014] The communication module is located on the side of the lower connecting plate facing away from the machine tool spindle, and is used to transmit the data collected by the line laser sensor.

[0015] In some embodiments, the spindle clamping module includes a bearing, a bolt, a lock nut, and a collet connected in sequence. A through hole for mounting the bearing is provided at the center of the upper connecting plate and the lower connecting plate. One end of the bolt is installed in the bearing, and the other end of the bolt is fitted with the lock nut. The collet is fitted on the lock nut and is connected to the tool holder of the machine tool spindle.

[0016] In some embodiments, the line laser in-machine measurement fixture is provided with three pose adjustment knobs. The first pose adjustment knob is set on the Y-axis of the line laser coordinate system and is used to adjust the rotation angle of the line laser sensor around the X-axis of the line laser coordinate system. The second and third pose adjustment knobs are symmetrically arranged about the Y-axis of the line laser coordinate system and are used to adjust the rotation angle of the line laser sensor around the Y-axis of the line laser coordinate system.

[0017] In some embodiments, the pose adjustment knob employs a precision differential head.

[0018] The second aspect of this disclosure provides a pose calibration method for the line laser in-machine measurement fixture according to any embodiment of the first aspect of this disclosure, characterized in that the installation pose error of the line laser in-machine measurement fixture includes an error component θ of the rotation of the line laser sensor around the X-axis of the line laser coordinate system. T (x) Error component θ of rotation around the Y-axis of the linear laser coordinate system T (y), the error component θ of the rotation around the Z-axis of the linear laser coordinate system. s The displacement error component δ along the X-axis of the laser coordinate system T (x) Displacement error component δ along the Y-axis of the laser coordinate system T (y) and the displacement error components along the Z-axis of the laser coordinate system, wherein the error component θ s Caused by the rotational positioning error of the machine tool spindle, the displacement error component along the Z-axis is ignored; the pose calibration method includes the following steps:

[0019] The line laser in-machine measurement fixture is connected to the tool holder of the machine tool spindle. A standard gauge block is fixed on the machine tool spindle with its nominal plane facing upwards. The machine tool spindle rotation angle is defined as S. When S = 0°, the machine tool Z-axis coordinate system and the machine tool spindle coordinate system coincide. The Z-axis of the machine tool spindle coordinate system and the Z-axis of the line laser coordinate system are collinear, and the other axes are parallel. The origin of the machine tool Z-axis coordinate system and the machine tool spindle coordinate system is the rotation center of the machine tool spindle end face, and the XYZ axis directions are in the same direction as the machine tool axes. A standard gauge block coordinate system is defined, with its origin at the center point of the nominal plane of the standard gauge block. The X-axis and Y-axis are located in the nominal plane of the standard gauge block, and the X-axis of the standard gauge block coordinate system is parallel to the X-axis of the machine tool Z-axis coordinate system. The Z-axis of the standard gauge block coordinate system is parallel to the Z-axis of the line laser coordinate system.

[0020] Align the measurement position of the line laser sensor with the edge of the standard gauge block, activate the machine tool's tool tip follow motion, and rotate the C-axis in both forward and reverse directions until the line laser intersects the edge of the standard gauge block. Then, calculate the spindle angle deviation of the machine tool by reverse-engineering the C-axis angle, thus completing the calculation of the error component θ. s Calibration;

[0021] With S = 90° and machine tool A-axis rotation angle A = 0°, the error component θ T (x) represents the angle between the measurement result of the line laser sensor and the horizontal line. By adjusting the pose adjustment knob, the error component θ is adjusted. T If (x) is less than the first preset threshold, the error component θ is processed. T Calibration of (x); Set S = 0° and rotate the machine tool A axis to an angle A = A1, at which point the error component θ is determined. T (y) is calculated based on the theoretical distance the line laser moves along the Z-axis of the line laser coordinate system and the difference between the measured distance of the line laser sensor. The error component θ is obtained by adjusting the pose adjustment knob. T If (y) is less than the second preset threshold, the error component θ is processed. T The calibration of (y);

[0022] The displacement component δ is calculated by adjusting the rotation angle A of the machine tool A axis to A0 and the average deviation of the measurement results from the 180° rotation of the laser sensor. T (x) and the displacement error component δ T (y);

[0023] The virtual tool length d of the line laser sensor is calculated based on the machine tool's mechanical coordinate Z value, the height of the standard gauge block, and the distance from the laser emission point of the line laser sensor to the nominal plane of the standard gauge block.

[0024] According to the calibrated error component θ T (x),θ T (x),θ s ,δ T (x),δ T (y) and the virtual blade length d of the line laser sensor are used to compensate for the installation posture error of the line laser sensor.

[0025] In some embodiments, the error component θ s Calculate according to the following formula:

[0026] θ s = (C0 + C1) / 2

[0027] Wherein, C0 is the angle of rotation of the machine tool C-axis in the positive direction after the machine tool tip point follows the motion, and C1 is the angle of rotation of the machine tool C-axis in the opposite direction after the machine tool tip point follows the motion. When the machine tool C-axis rotation angle is C1, the measurement result of the line laser sensor is horizontally symmetrical with the measurement result of the line laser sensor when the machine tool C-axis rotation angle is C0.

[0028] In some embodiments, the error component θ is calibrated. T When (x), it is approximately equal to the slope of the measurement data of the line laser sensor;

[0029] Calibrate the error component θ T When (y) is true, calculate according to the following formula:

[0030]

[0031] Where ΔZ is the distance the line laser sensor moves along the Z-axis of the machine tool within the measurement range when S = 0° and A = A1, and Δz1 is the measurement result z of the line laser sensor. l The average deviation.

[0032] In some embodiments, the error component δ is calibrated. T When (x), calculate according to the following formula:

[0033]

[0034] Wherein, Δz2 is the measurement result z of the line laser sensor corresponding to the machine tool spindle rotation angle S = 0° and the machine tool spindle rotation angle S = 180° when A = A0. l The average deviation.

[0035] Calibrate the error component δ T When (y) is true, calculate according to the following formula:

[0036]

[0037] Wherein, Δz3 is the measurement result of the line laser sensor corresponding to the machine tool spindle rotation angles S=90° and S=270° when A=A0. l The average deviation.

[0038] In some embodiments, the virtual blade length d of the line laser sensor is calculated according to the following formula:

[0039] d=H Z -H l -H s

[0040] Among them, H Z H represents the machine tool's Z-coordinate value. l H is the measurement height of the line laser sensor. s This refers to the height of the standard gauge block.

[0041] In some embodiments, compensation for the mounting pose error of the line laser sensor specifically includes:

[0042] Based on the machine tool spindle rotation angle S, the theoretical transformation matrix from the machine tool Z-axis coordinate system to the machine tool spindle coordinate system is defined as M0. Based on the virtual tool length d of the line laser sensor, the theoretical transformation matrix from the machine tool spindle coordinate system to the line laser coordinate system is defined as M1. The error component θ is defined as... s The resulting error matrix of the line laser sensor is E0, based on the error component θ. T (x),θ T (x),δ T (x),δ T (y) Define the installation error matrix of the line laser sensor on the machine tool spindle as E1, and define the result obtained by the line laser sensor measuring a certain point in the line laser coordinate system as Q. l =[0,y l ,z l ] T After considering the installation pose error of the line laser sensor, the result obtained by the line laser sensor measuring a certain point in the Z-axis coordinate system of the machine tool is Q. Za =M0E0M l E l Q l Then, based on the calibrated error component θ T (x),θ T (x),θ s ,δ T (x),δ T (y) and the virtual blade length d of the line laser sensor are used to calculate the error matrix E1 and the error matrix E0, thereby compensating for the installation pose error of the line laser sensor.

[0043] This disclosure has the following characteristics and beneficial effects:

[0044] This fixture is stable and reliable, easy to connect to a five-axis machine tool, and its posture adjustment method is simple and easy to implement. Combined with the linear laser posture calibration method, this fixture can accurately calibrate and compensate for the installation posture error of the linear laser, efficiently and rapidly improving the accuracy of in-machine measurements using the linear laser. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the overall structure of a line laser in-machine measurement fixture provided in the first aspect of this disclosure.

[0046] Figure 2 yes Figure 1 A schematic diagram of the laser sensor pose adjustment structure in the tooling shown.

[0047] Figure 3 This is a flowchart of a method for calibrating the installation posture error of a line laser in-machine measurement fixture, provided in a second aspect embodiment of this disclosure.

[0048] Figure 4 (a) and (b) are side and top views of the spindle error measurement in the calibration method provided in the second aspect of the present disclosure.

[0049] Figure 5 (a) and (b) are schematic diagrams of calibrating the angle deviation of a line laser sensor in the calibration method provided in the second aspect of the present disclosure.

[0050] Figure 6 (a) and (b) are schematic diagrams of the calibration method for calibrating the displacement deviation of a line laser sensor in the second aspect of the present disclosure.

[0051] Figure 7 This is a schematic diagram of the virtual blade length calibration of a line laser sensor in the calibration method provided in the second aspect of this disclosure.

[0052] In the picture:

[0053] 1. Spindle clamping module; 11. Bearing; 12. Bolt; 13. Locking nut; 14. Chuck; 2. Upper connecting plate; 3. Lower connecting plate; 4. Line laser sensor; 5. Power supply; 6. Communication module; 71. First position adjustment knob; 72. Second position adjustment knob; 73. Third position adjustment knob; 8. Tool holder. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0055] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0056] See Figure 1 The first aspect of this disclosure provides a line laser in-machine measurement fixture suitable for a five-axis machine tool. This fixture mainly includes a spindle clamping module 1, an upper connecting plate 2, a lower connecting plate 3, a line laser sensor 4, a power supply 5, a communication module 6, and several pose adjustment knobs; it defines the machine tool Z-axis coordinate system, the machine tool spindle coordinate system, and the line laser coordinate system, as follows: Figure 1 As shown, when the machine tool spindle rotation angle is 0°, the machine tool Z-axis coordinate system coincides with the machine tool spindle coordinate system. The machine tool spindle coordinate system and the line laser coordinate system are collinear along the Z-axis, and the other axes are parallel. The origin of the machine tool Z-axis coordinate system and the machine tool spindle coordinate system is the rotation center of the machine tool spindle end face. The XYZ axis directions are in the same direction as the machine tool axes. The origin of the line laser coordinate system is defined as the laser emission point of the line laser sensor 4, the Z-axis is defined as the emission laser direction of the line laser sensor 4, the Y-axis is defined as the positive direction of the measurement line of each measurement by the line laser sensor 4, and the X-axis is defined as the movement direction of the line laser sensor 4.

[0057] The spindle clamping module 1 is located at the center of this tooling and is used to connect the upper connecting plate 2 and the lower connecting plate 3 to the machine tool spindle tool holder 8, and allows for a small rotation of the Z-axis of the wound laser coordinate system between the upper connecting plate 2 and the lower connecting plate 3.

[0058] Several pose adjustment knobs are evenly distributed between the upper connecting plate 2 and the lower connecting plate 3 to adjust the rotation angle of the line laser sensor 4 around the X and Y axes of the line laser coordinate system.

[0059] The line laser sensor 4 is located at the center of this fixture and on the side of the lower connecting plate 3 facing away from the machine tool spindle, and is used to measure the contour of the workpiece on the machine tool.

[0060] Power supply 5 is located on the side of the lower connecting plate 3 facing away from the machine tool spindle, and is used to power the line laser sensor 4;

[0061] The communication module 6 is located on the side of the lower connecting plate 3 facing away from the machine tool spindle, and is used to transmit the data collected by the line laser sensor 4.

[0062] In some embodiments, see Figure 1 , Figure 2 The spindle clamping module 1 includes a bearing 11, a bolt 12, a locking nut 13, and a collet 14 connected in sequence. A through hole for mounting the bearing 11 is provided at the center of the upper connecting plate 2 and the lower connecting plate 3. The bearing 11 can be a fisheye bearing. One end of the bolt 12 is installed inside the bearing 11, and the other end of the bolt 12 is fitted with the locking nut 13. The collet 14 is fitted onto the locking nut 11 and is connected to the tool holder of the machine tool spindle. The bolt 12 and the locking nut 13 connect and lock the upper and lower connecting plates. The bearing 11 allows for a small angular displacement between the upper connecting plate 2 and the lower connecting plate 3.

[0063] In some embodiments, see Figure 2 This fixture has three pose adjustment knobs. The first pose adjustment knob 71 is located on the Y-axis of the linear laser coordinate system and is used to adjust the rotation angle θ of the linear laser sensor 4 around the X-axis of the linear laser coordinate system. T (x); The second pose adjustment knob 72 and the third pose adjustment knob 73 are symmetrically arranged about the Y-axis of the line laser coordinate system, and are used to adjust the rotation angle θ of the line laser sensor 4 around the Y-axis of the line laser coordinate system. T (y). To improve adjustment accuracy, all posture adjustment knobs use precision differential micrometer heads, with coarse and fine adjustment modes. The coarse adjustment pitch is 0.3mm, and the fine adjustment pitch is 0.03mm.

[0064] In some embodiments, the power source 5 is a lithium battery.

[0065] In some embodiments, the communication module 6 is a router.

[0066] Before using the aforementioned line laser on-machine measurement fixture, its installation pose error needs to be calibrated. Therefore, the second aspect of this disclosure proposes a method for calibrating the installation pose error of the aforementioned line laser on-machine measurement fixture. The installation pose error of this fixture has six spatial degrees of freedom, including the error component θ of the line laser sensor rotating around the X-axis of the line laser coordinate system. T (x) Error component θ of rotation around the Y-axis of the linear laser coordinate system T (y), the error component of rotation around the Z-axis of the linear laser coordinate system, and the displacement error component δ along the X-axis of the linear laser coordinate system. T (x) Displacement error component δ along the Y-axis of the laser coordinate system T(y) and the displacement error components along the Z-axis of the line laser coordinate system. The error component of the line laser sensor's rotation around the Z-axis is mainly caused by the machine tool spindle rotation positioning error. Since the line laser sensor's Z-axis distance measurement is accurate, the displacement error component of the fixture along the Z-axis is ignored. Define S as the machine tool spindle rotation angle, and define matrix M0 as the theoretical transformation matrix from the machine tool Z-axis coordinate system to the machine tool spindle coordinate system. The expression for matrix M0 is:

[0067]

[0068] Analogous to the general concept of a five-axis machine tool, let d be the virtual tool length of the line laser sensor, and let matrix M1 be the theoretical transformation matrix from the machine tool spindle coordinate system to the line laser coordinate system. The expression of matrix M1 is:

[0069]

[0070] During the machine measurement process, the machine tool spindle clamping line laser drives the line laser sensor 4 to scan using the machine measurement fixture. Due to a small spindle rotation angle deviation θ during tool holder disassembly... s The spindle rotation angle deviation θ s For the small rotation angle around the Z-axis, i.e., the error component of the line laser sensor 4 rotating around the Z-axis, the spindle rotation angle deviation θ is defined. s The resulting error matrix of the line laser sensor 4 is E0, and the expression for the error matrix E0 is:

[0071]

[0072] According to the error component θ T (x),θ T (x),δ T (x),δ T (y) Define the installation error matrix of the line laser sensor on the machine tool spindle as E1, which represents the displacement deviation of the line laser emission point and the direction deviation of the laser line caused by insufficient manufacturing and assembly precision of the tooling itself. The expression for the error matrix E1 is:

[0073]

[0074] In the online laser coordinate system, the result obtained by the line laser sensor 4 measuring a certain point is defined as Q. l =[0,y l ,z l ] T After considering the installation pose error of the line laser sensor, the result obtained by the line laser sensor measuring a certain point in the machine tool's Z-axis coordinate system is Q. Za =M0E0M l E l Q lTherefore, as long as θ is calibrated T (x),θ T (x),θ s ,δ T (x),δ T By using the parameters (y) and d, the error matrices E0 and E1 can be calculated, thereby compensating for the installation pose error of the line laser sensor.

[0075] See Figure 3 The calibration method provided in the second aspect of this disclosure includes the following steps:

[0076] S1. Installation of tooling and standard gauge blocks

[0077] The line laser in-machine measurement fixture is connected to the tool holder of the machine tool spindle via the spindle clamping module, thus achieving the installation of the line laser in-machine measurement fixture on the machine tool spindle. A standard gauge block is fixed on the machine tool spindle, with its nominal plane facing vertically upwards. A coordinate system for the standard gauge block is constructed, with its origin at the center point of the nominal plane of the standard gauge block. The X and Y axes are located within the nominal plane of the standard gauge block, and the X-axis of the standard gauge block coordinate system is parallel to the X-axis of the machine tool's Z-axis coordinate system. The Z-axis of the standard gauge block coordinate system is parallel to the Z-axis of the line laser coordinate system. See [link to relevant documentation]. Figure 4 (a)

[0078] S2, Machine tool spindle rotation angle deviation calibration

[0079] Align the line laser sensor's measurement position with the edge of the standard gauge block, activate the machine tool's tool tip follow motion, and rotate the machine tool's C-axis in both forward and reverse directions until the line laser intersects the edge of the standard gauge block. Then, calculate the machine tool spindle angle deviation θ in reverse order using the C-axis rotation angle. s .

[0080] S3, Line Laser Sensor Installation Angle Deviation Calibration

[0081] When the machine tool spindle rotation angle S = 90° and the machine tool A-axis rotation angle A = 0°, the error component θ of the line laser sensor's rotation around the X-axis of the line laser coordinate system is... T (x) represents the angle between the measurement result of the line laser sensor and the horizontal line. By adjusting the pose adjustment knob, the error component θ is adjusted. T If (x) is less than the first set threshold, the error component θ is processed. T Calibration of (x); Set the machine tool spindle rotation angle S = 0° and rotate the machine tool A axis to make the machine tool A axis rotation angle A = A1. At this time, the error component θ of the line laser sensor rotating around the Y-axis of the line laser coordinate system. T (y) is calculated based on the theoretical distance the line laser moves along the Z-axis of the line laser coordinate system and the difference between the measured distance of the line laser sensor. The error component θ is obtained by adjusting the pose adjustment knob.T If (y) is less than the second set threshold, the error component θ is processed. T The calibration of (y).

[0082] S4. Line laser sensor installation displacement deviation calibration

[0083] The machine tool's A-axis rotation angle is set to A = A0. The displacement component δ of the line laser sensor along the X-axis of the line laser coordinate system is calculated by the deviation of the average value of the measurement results from the rotating line laser sensor at 180°. T (x) and the displacement error component δ along the Y-axis of the laser coordinate system. T (y).

[0084] S5, Linear Laser Sensor Virtual Blade Length Calibration

[0085] The virtual tool length of the line laser sensor is calculated based on the machine tool's mechanical coordinate Z value, the height of the standard gauge block, and the distance from the laser emission point of the line laser sensor to the nominal plane of the standard gauge block, and then input into the CNC system.

[0086] S6, Line Laser Sensor Mounting Pose Error Compensation

[0087] θ is calibrated based on the above steps. T (x),θ T (x),θ s ,δ T (x),δ T Substitute the parameters (y) and d into the error matrix E0, E1, and obtain the result Q from the laser sensor measuring a certain point in the machine tool's Z-axis coordinate system. Za =M0E0M l E l Q l This allows for the compensation of the installation pose error of the line laser sensor.

[0088] In some embodiments, step S2 is implemented as follows:

[0089] See Figure 4 In (a) and (b), the spindle rotation angle deviation θ of the machine tool is calibrated using standard gauge blocks installed parallel to the machine tool's Z-axis coordinate system. s This allows for the calibration of the error component of the line laser sensor rotating around the Z-axis. Specifically, the center of the line laser measurement beam is positioned close to the edge of the standard gauge block. The machine tool's tool tip follow motion is activated, and the machine tool's C-axis is rotated in the positive direction. When the rotation angle of the machine tool's C-axis is C0, the measurement result of the line laser sensor is as follows: Figure 4As shown in (b), stop rotating the machine tool and rotate the C-axis in the opposite direction until the measurement result of the line laser sensor is horizontally symmetrical to the measurement result of the line laser sensor when the C-axis rotation angle is C0. Record the rotation angle of the C-axis at this point as C1. The corresponding spindle rotation angle is then calculated using the formula θ. s = (C0 + C1) / 2. Because the C-axis rotary table of the machine tool has very high motion accuracy, repeated calibration experiments have shown that the accuracy is higher than 0.01°.

[0090] In some embodiments, step S3 is implemented as follows:

[0091] like Figure 5 As shown in (a) and (b), θ T (x) and θ T (y) corresponds to the small rotation angles of the line laser sensor around the X and Y axes, respectively. When the machine tool spindle rotation angle S = 90° and the machine tool A-axis rotation angle A = 0°, θ T (x) represents the angle between the measurement result of the line laser sensor and the horizontal line, which can be approximated by the measurement data y of the line laser sensor. l ,z l The slope. Adjust the first attitude adjustment knob 71 multiple times until θ... T (x) is almost 0. In one measurement instance, θ is considered to be... T When (x) < 0.01°, the adjustment is stopped, thus completing the adjustment of the error component θ. T The labeling of (x).

[0092] When the machine tool spindle rotation angle S = 0° and the machine tool A-axis rotation angle A = A1, the line laser sensor moves ΔZ along the machine tool Z-axis direction within its measurement range. The measurement result z of the line laser sensor is recorded. l If the average deviation is Δz1, then the error components are calculated according to the following formula:

[0093]

[0094] Adjust the second pose adjustment knob 72 and the third pose adjustment knob 73 multiple times, with the two knobs adjusting in opposite directions, i.e., adjusting by loosening and tightening, until θ is reached. T (y) is almost 0. In one measurement instance, θ is considered to be... T When (y) < 0.01°, the adjustment is stopped, thus completing the adjustment of the error component θ. T The calibration of (y).

[0095] It should be noted that the setting of A1 needs to be constrained by the accuracy of the line laser sensor's rotation angle around the Y-axis. For example, in this embodiment, the line laser sensor can ensure high-precision measurement even when the line laser rotates within ±30° around the Y-axis. Therefore, A1 can be set to [10°, 30°].

[0096] In some embodiments, step S4 is implemented as follows:

[0097] like Figure 6 As shown in (a) and (b), δ T (x) and δ T (y) corresponds to the displacement error components along the X-axis and Y-axis of the line laser sensor to be calibrated, respectively.

[0098] When the machine tool's A-axis rotation angle is A0, record the measurement results z of the line laser sensor corresponding to the machine tool spindle rotation angles S = 0° and S = 180°. l If the average deviation is Δz2, then the error component δ T The formula for calculating (x) is:

[0099]

[0100] When the machine tool's A-axis rotation angle is A0, record the measurement results z of the line laser sensor corresponding to the machine tool spindle rotation angles S = 90° and S = 270°. l If the average deviation is Δz3, then the error component δ T The formula for calculating (y) is:

[0101]

[0102] It should be noted that the setting of A0 needs to be constrained by the accuracy of the line laser sensor's rotation angle around the X-axis. At the same time, A0 should not be too small, which would reduce the measurement accuracy. For example, in the practical embodiment of this disclosure, the line laser sensor can ensure high-precision measurement even when the line laser rotates within ±18° around the X-axis. Therefore, A1 can be set to [10°, 18°].

[0103] In some embodiments, step S5 is implemented as follows:

[0104] like Figure 7 As shown, the machine tool's mechanical coordinate Z value is defined as H. Z (i.e., the distance between the origin of the machine tool's Z-axis coordinate system and the upper surface of the machine tool's rotary table), the height of the standard gauge block is H. s The measurement height of the line laser sensor is H. l (That is, the Z-axis distance from the laser emission point of the line laser sensor to the origin of the standard gauge block coordinate system). There are no requirements for the machine tool spindle angle during the measurement process. Taking a machine tool spindle angle of 90° as an example, the measurement height H of the line laser sensor is adjusted by adjusting the machine tool's Z-axis. l It is within the optimal measurement range of the line laser sensor. Therefore, the formula for calculating the virtual blade length d of the line laser sensor is:

[0105] d=H Z -H l -H s

[0106] Understandably, this method fully calibrates and compensates for all degrees of freedom of the mounting pose error of the line laser sensor. The proposed calibration method is feasible and efficient, and a reasonable calibration sequence is designed to avoid coupling between different mounting pose errors. The mounting pose error of the line laser is calibrated with high precision and effective compensation is achieved, thereby improving the accuracy of in-machine measurement of the line laser.

[0107] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0108] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A line laser in-machine measurement fixture, characterized in that, It includes a spindle clamping module, an upper connecting plate, a lower connecting plate, a line laser sensor, a power supply, a communication module, and several pose adjustment knobs. A line laser coordinate system is defined, with the origin being the laser emission point of the line laser sensor, the X-axis being the movement direction of the line laser sensor, the Y-axis being the positive direction of the measurement line measured by the line laser sensor each time, and the Z-axis being the emission laser direction of the line laser sensor. The spindle clamping module is located at the center of the line laser in-machine measurement fixture, and is used to connect the upper connecting plate and the lower connecting plate to the machine tool spindle tool holder, and allows a small rotation of the Z-axis of the line laser coordinate system between the upper connecting plate and the lower connecting plate. Several pose adjustment knobs are evenly distributed between the upper connecting plate and the lower connecting plate to adjust the rotation angle of the line laser sensor around the X-axis and Y-axis of the line laser coordinate system. The line laser sensor is located at the center of the line laser in-machine measurement fixture and on the side of the lower connecting plate facing away from the machine tool spindle, and is used to measure the contour of the workpiece on the machine tool. The power supply is located on the side of the lower connecting plate facing away from the machine tool spindle, and is used to power the line laser sensor; The communication module is located on the side of the lower connecting plate facing away from the machine tool spindle, and is used to transmit the data collected by the line laser sensor; The line laser in-machine measurement fixture is equipped with three pose adjustment knobs. The first pose adjustment knob is set on the Y-axis of the line laser coordinate system and is used to adjust the rotation angle of the line laser sensor around the X-axis of the line laser coordinate system. The second and third pose adjustment knobs are symmetrically set about the Y-axis of the line laser coordinate system and are used to adjust the rotation angle of the line laser sensor around the Y-axis of the line laser coordinate system. The installation pose error of the line laser in-machine measurement fixture includes the error component of the line laser sensor's rotation around the X-axis of the line laser coordinate system. Error components of rotation around the Y-axis of the linear laser coordinate system Error components of rotation around the Z-axis of the linear laser coordinate system Displacement error components along the X-axis of the laser coordinate system Displacement error components along the Y-axis of the laser coordinate system and the displacement error component along the Z-axis of the laser coordinate system, the error component This is caused by the rotational positioning error of the machine tool spindle.

2. The line laser in-machine measurement fixture according to claim 1, characterized in that, The spindle clamping module includes a bearing, a bolt, a lock nut, and a collet connected in sequence. A through hole for installing the bearing is provided at the center of the upper connecting plate and the lower connecting plate. One end of the bolt is installed in the bearing, and the other end of the bolt is fitted with the lock nut. The collet is fitted on the lock nut and is connected to the tool holder of the machine tool spindle.

3. The line laser in-machine measurement fixture according to claim 1, characterized in that, The posture adjustment knob uses a precision differential dial.

4. A method for pose calibration of a line laser in-machine measurement fixture according to any one of claims 1 to 3, characterized in that, Ignoring the displacement error component along the Z-axis, the pose calibration method includes the following steps: The line laser in-machine measurement fixture is connected to the tool holder of the machine tool spindle. A standard gauge block is fixed on the machine tool spindle with its nominal plane facing upwards. The machine tool spindle rotation angle is defined as S. When S = 0°, the machine tool Z-axis coordinate system and the machine tool spindle coordinate system coincide. The Z-axis of the machine tool spindle coordinate system and the Z-axis of the line laser coordinate system are collinear, and the other axes are parallel. The origin of the machine tool Z-axis coordinate system and the machine tool spindle coordinate system is the rotation center of the machine tool spindle end face, and the XYZ axis directions are in the same direction as the machine tool axes. A standard gauge block coordinate system is defined, with its origin at the center point of the nominal plane of the standard gauge block. The X-axis and Y-axis are located in the nominal plane of the standard gauge block, and the X-axis of the standard gauge block coordinate system is parallel to the X-axis of the machine tool Z-axis coordinate system. The Z-axis of the standard gauge block coordinate system is parallel to the Z-axis of the line laser coordinate system. Align the measurement position of the line laser sensor with the edge of the standard gauge block, activate the machine tool's tool tip follow motion, and rotate the C-axis in both forward and reverse directions until the line laser intersects the edge of the standard gauge block. Then, calculate the spindle angle deviation of the machine tool by reverse-engineering the C-axis angle, thus completing the calculation of the error component. Calibration; With S = 90° and machine tool A-axis rotation angle A = 0°, the error component at this time... This refers to the angle between the measurement result of the line laser sensor and the horizontal line. By adjusting the pose adjustment knob, the error component is adjusted. If the error component is less than a first preset threshold, the error component is processed. Calibration; set S = 0° and rotate the machine tool A axis so that the machine tool A axis rotation angle A = A1, at which point the error component... The error component is calculated based on the theoretical distance the line laser moves along the Z-axis of the line laser coordinate system and the difference between the measured distance from the line laser sensor. This error is then adjusted by turning the pose adjustment knob. If the error component is less than the second preset threshold, the error component is processed. Calibration; The displacement error component is calculated by setting the machine tool A-axis rotation angle A=A0 and using the average deviation of the measurement results from the 180° rotation of the linear laser sensor. and the displacement error components ; The virtual tool length d of the line laser sensor is calculated based on the machine tool's mechanical coordinate Z value, the height of the standard gauge block, and the distance from the laser emission point of the line laser sensor to the nominal plane of the standard gauge block. According to the calibrated error components The virtual blade length d of the line laser sensor is used to compensate for the installation posture error of the line laser sensor.

5. The pose calibration method according to claim 4, characterized in that, The error component Calculate according to the following formula: in, To enable the machine tool's tool tip to follow the movement, rotate the machine tool's C-axis by an angle in the positive direction. To enable the machine tool tool tip to follow the motion, rotate the machine tool C-axis in the opposite direction by an angle, and the machine tool C-axis rotation angle is... The measurement results of the time-line laser sensor are related to the C-axis rotation angle of the machine tool. The measurement results from the time-line laser sensor are horizontally symmetrical.

6. The pose calibration method according to claim 4, characterized in that, Calibrate the error components At that time, it is approximately equal to the slope of the measurement data from the line laser sensor; Calibrate the error components When calculating, use the following formula: in, When S = 0° and At that time, the distance the line laser sensor moves along the Z-axis of the machine tool within its measurement range. The measurement results of the line laser sensor The average deviation.

7. The pose calibration method according to claim 4, characterized in that, Calibrate the error components When calculating, use the following formula: in, For when The measurement results of the line laser sensor at machine tool spindle rotation angles S = 0° and S = 180° are as follows. The average deviation; Calibrate the error components When calculating, use the following formula: in, For when The measurement results of the line laser sensor at machine tool spindle rotation angles S = 90° and S = 270° are as follows. The average deviation.

8. The pose calibration method according to claim 4, characterized in that, The virtual blade length d of the line laser sensor is calculated according to the following formula: in, The Z-value of the machine tool's mechanical coordinates. The measurement height is for the line laser sensor. This refers to the height of the standard gauge block.

9. The pose calibration method according to claim 4, characterized in that, Compensation for the mounting pose error of the line laser sensor specifically includes: Based on the machine tool spindle rotation angle S, the theoretical transformation matrix from the machine tool Z-axis coordinate system to the machine tool spindle coordinate system is defined as follows: Based on the virtual tool length d of the line laser sensor, the theoretical transformation matrix from the machine tool spindle coordinate system to the line laser coordinate system is defined as follows: Defined by the error components The resulting error matrix of the line laser sensor is as follows: According to the error components The installation error matrix of the line laser sensor on the machine tool spindle is defined as follows: The result obtained by the line laser sensor measuring a certain point in the line laser coordinate system is defined as follows: After considering the installation pose error of the line laser sensor, the result obtained by the line laser sensor measuring a certain point in the Z-axis coordinate system of the machine tool is as follows: Then, based on the calibrated error components... and the error matrix for calculating the virtual blade length d of the line laser sensor. and error matrix This allows for compensation of the mounting pose error of the line laser sensor.

Images