Distributed Precision Measurement Device and Method for Spatial Posture of Large-Size Flat Dies

Abstract

The present invention discloses a distributed precision measurement device and method for the spatial attitude of large-size flat molds, which relates to the technical field of geometric measurement of mold workpieces. It aims to improve the positioning accuracy and efficiency of molds, expand their applicable range, and protect the mold surface. The measurement device includes four sets of three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2, an XYZ three-way declination measurement and control system 3, and a control computer 4. The XYZ three-way declination measurement and control system 3 is used to obtain, analyze the three-dimensional data collected by the laser profiler 2 in real time, and calculate and evaluate the declinations of the spatial attitude of the mold 5 in the XYZ three directions. The measurement device of the present invention can realize the function of calculating and evaluating the declinations of the spatial attitude of the measured mold, with fast measurement speed, high efficiency and accuracy, and overcomes the deficiencies of the traditional measurement methods and devices for the spatial attitude of large-size flat molds.

Description

Technical Field

[0001] The present invention relates to the technical field of geometric measurement of mold workpieces, and specifically relates to a distributed precise measurement method and device for the spatial attitude of large-size flat molds. Background Art

[0002] When a large flat mold is positioned and installed by hoisting at the processing site, the mold often has errors such as unevenness, incorrectness, and skew, that is, the upper surface of the mold has angular error with respect to the X-axis and Y-axis and rotational error about the Z-axis relative to the reference plane XYZ coordinate system.

[0003] Specifically, the mold installation error mainly includes the parallelism error between the parallelism measurement reference plane of the mold and the parallelism reference plane of the numerical control machine tool, and the angular error between the center line connection of the measurement reference circles in the measurement reference holes of the mold angular tilt and the angular tilt error reference axis of the numerical control machine tool. When processing, parts are laid on the mold surface, and the installation position accuracy of the mold directly affects the processing accuracy of the parts. To ensure the processing accuracy of the parts, it is required that the position error of the mold in the horizontal plane ≤ 0.03 (±0.015 mm), including the Z-axis direction and the Z-axis rotation direction.

[0004] Currently, there are already many methods for measuring the spatial attitude of molds, as follows:

[0005] For example, a Chinese invention patent named "Rigid Body Spatial Pose Measurement Device and Its Measurement Method" announced on July 5, 2006, with the application number "200410009083.7" gives a rigid body spatial pose measurement device and its measurement method, including a measurement execution mechanism, a data acquisition device, and a computer storing a calculation program. By selecting a suitable connection position on the rigid body and obtaining initial data through the above device, the spatial pose information of the measured rigid body is obtained using an iterative equation set. In this method, a wire-drawing encoder is used, and the measurement accuracy of the measurement method is low, and the applicable occasions are also limited to a certain extent.

[0006] For example, a Chinese invention patent named "A Mold Positioning System, Method and Device" announced on April 7, 2020, with the application number "201811160286.4" gives a mold positioning system, method and device that is based on ultra-wideband wireless communication technology (UWB) for mold positioning. The system includes positioning devices, multiple UWB base stations, and a server. The mold is positioned by sending UWB signals of mold information to multiple UWB base stations, and its positioning accuracy can only reach the centimeter level.

[0007] A Chinese invention patent titled "A Spatial Pose Measurement System and Method Based on Active Vision" and with an application number of "201811415367.4", published on February 5, 2019, provides a spatial pose measurement system and method based on active vision, including an infrared light-emitting target board, a camera, and a monitoring terminal. The spatial pose of an object is obtained by extracting the image feature information of the pose state of a marker installed on the object to be measured through the camera. This method requires installing markers on the object surface, which not only brings installation errors, is relatively cumbersome in the operation process, but also has low positioning accuracy.

[0008] A Chinese invention patent titled "A Large Workpiece Pose Measurement System and Method Based on Stereo Vision and Structured Light Vision" and with an application number of "201810764075.5", announced on November 6, 2020, provides a large workpiece pose measurement system and method based on stereo vision and structured light vision. This method first uses a computer to detect and roughly locate the positions of the positioning markers on the large workpiece, and then the robotic arm carries the laser structured light vision sensor at its end to move to the target position to perform local precise measurement on the positioning markers, completing the precise measurement of the pose of the large workpiece. The positioning method in this method will result in a very complex algorithm structure, which is time-consuming when writing and modifying. Then, it is necessary to install positioning markers, and training is required before each target detection of the positioning markers. Secondly, the movement of the robotic arm carrying the laser structured light vision sensor at its end to the target position will result in this accuracy only reaching the accuracy of the robotic arm, and the accuracy cannot be improved further.

[0009] Based on the above patents, there are still many deficiencies in the positioning of this mold. For example: the measurement devices and instruments used are not applicable in some occasions, the positioning process is time-consuming, the positioning accuracy of some positioning devices themselves has a certain range, which will lead to the inability to improve the positioning accuracy of the mold, and the low automation level of some devices will result in low real-time performance of the measurement method and is not applicable in many demanding occasions; thus, it can be seen that the applicable range of the pose calculation methods for many large flat molds is restricted. Summary of the Invention

[0010] In view of the above problems, the present invention proposes a distributed precision measurement device and method for the spatial pose of large-size flat molds, which can effectively solve various problems existing in the prior art, such as troublesome operation, low accuracy, small applicable range, large limitations, etc., and can effectively realize the automatic precision measurement of the spatial pose of large molds. To achieve the improvement of the mold positioning accuracy and efficiency, expand its applicable range, and protect the mold surface.

[0011] The technical solution of the present invention is as follows: The measuring device includes four three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2, an XYZ three-way deflection measurement and control system 3, and a control computer 4. The four three-dimensional high-precision motion mechanisms 1 and the control computer 4 are all installed on a workbench 8. The XYZ three-way deflection measurement and control system 3 is installed on the control computer 4. The four three-dimensional high-precision motion mechanisms 1 are respectively controlled by the XYZ three-way deflection measurement and control system 3, so that the four line laser profilers 2 fixedly installed on the transverse rails of the four three-dimensional high-precision motion mechanisms 1 perform motions in the X, Y, and Z directions respectively;

[0012] The XYZ three-way deflection measurement and control system 3 is used to collect, analyze the three-dimensional measurement data of the laser profiler 2 in real time, and evaluate the deflection angles of the mold 5 in the X, Y, and Z directions.

[0013] A plurality of vertically arranged adjustable support columns are fixedly connected to the workbench 8. The mold 5 is placed on the plurality of adjustable support columns, and the lengths of the plurality of adjustable support columns are respectively adjusted in combination with the data of the control computer 4, so that the mold 5 is finally kept in a horizontal state;

[0014] The convex surface of the mold 5 is the surface to be processed, and the bottom surface is flat. Four sinking grooves are opened at the edge of the upper surface of the mold 5. The four sinking grooves are evenly distributed around the mold 5. The bottom of the sinking groove is a small plane 6. Two conical holes 7 are opened on two of the small planes 6. The two conical holes 7 are symmetrically arranged along the center of the mold 5.

[0015] The four three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2 are distributed and installed in four directions of the workbench 8. The control computer 4 installed with the XYZ three-way deflection measurement and control system 3 is also placed on the workbench 8.

[0016] The three-dimensional high-precision motion mechanism 1 includes a longitudinal rail, a vertical rail, and a transverse rail that are perpendicular to each other in pairs. The longitudinal rail is horizontally arranged and fixedly connected to the workbench. The vertical rail is vertically arranged and its bottom is slidably connected to the longitudinal rail. The transverse rail is horizontally arranged and its middle part is slidably connected to the vertical rail. The laser profiler 2 is installed on the transverse rail, and the installation position of the laser profiler 2 can be finely adjusted;

[0017] The three-dimensional high-precision motion mechanism 1 further includes three servo linear drivers powered by servo motors. The three servo linear drivers are respectively connected to the ends of the longitudinal guide rail, the bottom of the vertical guide rail, and the ends of the transverse guide rail. By driving the three servo linear drivers, the vertical guide rail can move up and down in the vertical direction, or the longitudinal guide rail can move back and forth linearly in the horizontal direction, or the transverse guide rail fixedly installed with the line laser profiler 2 can move back and forth left and right in the horizontal direction.

[0018] The control computer 4 sends motion displacement commands to the multi-axis motion controller, and the multi-axis motion controller controls the servo motors in each servo linear driver to move, so as to control the three-dimensional high-precision motion mechanism 1 carrying the laser profiler 2 to perform XYZ three-way motion.

[0019] The measurement is carried out according to the following method:

[0020] S1. System calibration: Establish a coordinate transformation model for the system, mainly including the coordinate system of the laser profiler (O L -X L Y L Z L ), the coordinate system of the three-dimensional high-precision motion mechanism (O P -X P Y P Z P ), and the machine tool coordinate system (O M -X M Y M Z M ). In order to achieve the unification of the coordinate systems in the measurement system, the transformation matrix between the coordinate systems needs to be obtained through calibration. First, calibrate the coordinate system of the laser profiler to the coordinate system of the motion mechanism, and use the Gauss-Newton iteration method to solve the coordinate transformation relationship between the coordinate system of the three-dimensional high-precision motion mechanism and the machine tool coordinate system to achieve the unification of the coordinate systems;

[0021] S2. Mechanism initialization: Initialize the XYZ three-way deflection measurement and control system, the laser profiler, and the three-dimensional high-precision motion mechanism;

[0022] S3. Control of the three-dimensional high-precision motion mechanism: Four three-dimensional high-precision motion mechanisms 1 carrying the line laser profiler 2 respectively perform automatic scanning measurements on the measured surfaces at the four corners or four sides of the upper surface of the mold 5 from one side to the other side; First, measure several small planes 6 on the upper surface of the mold 5, and then measure any two conical holes 7 on the diagonal or opposite side small planes 6;

[0023] S4. Real-time displacement data acquisition: During the scanning measurement process, the line laser profiler 2 is in the contour mode. The XYZ three-axis declination measurement and control system 3 reads a contour line data generated by the line laser profiler 2 at regular intervals until the scanning is completed. Finally, a series of measured surface contour line data are obtained, and these contour data containing surface information are collected.

[0024] S5. Data processing:

[0025] S5.1. Fitting the small plane on the upper surface of the mold to obtain the plane equation: Sort the data points of each small plane 6 obtained by acquisition according to the Z coordinate value, remove a small part of the largest points at the front and a small part of the smallest points at the back. Convert all the remaining data points from the local coordinate system of the line laser profiler to the machine tool coordinate system, and perform spatial plane fitting by the least squares method. The principle of the least squares evaluation method is that the most reliable value of the measurement result should be solved under the condition that the sum of the squares of the residual errors is the smallest. Let: be the smallest, that is

[0026]

[0027] x i 、y i 、z i : The coordinate values of the measured data points

[0028] Q: The sum of the squares of the residual errors

[0029] A, B, C are the equation coefficients of the plane equation Ax + By - z + C = 0;

[0030] After determining the values of A, B, C in the coefficient matrix, the equation of the fitted plane can be obtained as Ax + By - z + C = 0. After obtaining the plane, find the normal vector of the plane, and the declinations of the upper surface of the mold with respect to the two coordinate axes, that is, with respect to the X-axis and Y-axis of the machine tool coordinate system, can be obtained.

[0031] S5.2. Fitting a straight line through the center coordinates of two holes on the small plane of the upper surface of the mold to obtain the straight line equation: For the two center coordinates obtained by measuring the two conical holes 7, convert them from the local coordinate system of the line laser profiler to the machine tool coordinate system respectively, calculate the spatial straight line equation represented by these two points, and obtain the angle between the projection of this straight line on the XOY plane and the X-axis (or Y-axis), that is, the rotation angle around the Z-axis.

[0032] S5.3. Obtaining the spatial pose of the mold: After obtaining the declinations of the upper surface of the mold 5 with respect to the X-axis and Y-axis of the machine tool coordinate system and the rotation angle around the Z-axis through steps S5.1 and S5.2, the spatial pose of the mold 5 can be obtained.

[0033] The present invention has the following advantages compared with the existing technologies: First, the device of the present invention adopts a three-dimensional high-precision motion mechanism equipped with a line laser profiler for measurement in the XYZ three-way deflection measurement and control system, which can complete the positioning of large flat molds in industrial scenarios, and has high stability and measurement accuracy. The repeated measurement accuracy can reach 10 to 20 microns, and the pose of the measured mold can be directly measured. Not only is the system real-time performance high, but also the measurement efficiency and measurement accuracy in the measurement of large flat molds are improved.

[0034] The measurement device of the present invention can realize the function of calculating and evaluating the deflection angle of the spatial attitude of the measured mold, with fast measurement speed, high efficiency and accuracy, and overcomes the deficiencies of the traditional measurement methods and devices for the spatial attitude of large flat molds. Brief Description of the Drawings

[0035] Figure 1 is the structural schematic diagram of this case,

[0036] Figure 2 is the working flow chart of this case,

[0037] Figure 3 is the system structure diagram of this case,

[0038] Figure 4 is the control schematic diagram of the line laser profiler of this case,

[0039] Figure 5 is the schematic diagram of the working state of this case;

[0040] In the figure, 1 is a three-dimensional high-precision motion mechanism, 2 is four sets of line laser profilers, 3 is an XYZ three-way deflection measurement and control system, 4 is a control computer, 5 is a mold, 6 is a small plane, 7 is a conical hole, and 8 is a workbench. Detailed Description of the Preferred Embodiment

[0041] To clearly illustrate the technical features of this patent, the following will elaborate on this patent in detail through specific embodiments and in conjunction with its drawings.

[0042] The embodiment of the present invention provides a distributed precision measurement method and device for the spatial attitude of large flat molds. The measurement object is a large flat mold, and the measurement object used is as Figure 1 (Schematic diagram of the distributed measurement device for the spatial attitude of a mold with a flat bottom) shown in mold 5, as Figure 1 shown, the flat plate on the bottom surface of mold 5 is a rectangle with a length of 600 mm, a width of 350 mm, and a thickness of 30 mm. The fillet radius at the four corners is 20 mm, and there are four small planes on the four sides. There are two conical holes on two opposite small planes. During the experiment, mold 5 is placed horizontally.

[0043] The measurement device includes four three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2, an XYZ three-way declination measurement and control system 3, and a control computer 4. The four three-dimensional high-precision motion mechanisms 1 and the control computer 4 are both installed on a workbench 8. The XYZ three-way declination measurement and control system 3 is installed on the control computer 4. The four three-dimensional high-precision motion mechanisms 1 are respectively controlled by the XYZ three-way declination measurement and control system 3, so that the four line laser profilers 2 fixedly installed on the transverse guide rails of the four three-dimensional high-precision motion mechanisms 1 perform motions in the X, Y, and Z directions respectively;

[0044] The XYZ three-way declination measurement and control system 3 includes a plane rotation angle calculation module, a plane rotation angle evaluation module, a positioning line rotation angle calculation module, and a positioning line rotation angle evaluation module. The XYZ three-way declination measurement and control system 3 is used for real-time collection and analysis of the three-dimensional measurement data of the laser profiler 2 and the declination evaluation of the mold 5 in the XYZ three directions.

[0045] A plurality of vertically arranged adjustable support columns are also fixedly connected to the workbench 8. The mold 5 is placed on the plurality of adjustable support columns. The lengths of the plurality of adjustable support columns are respectively adjusted in combination with the data of the control computer 4, and finally the mold 5 is kept in a horizontal state. Thus, problems such as unevenness, incorrectness, and skewness that occur after the mold is hoisted and placed are overcome, that is, the declination errors of the mold upper surface relative to the reference plane XYZ coordinate system in the X-axis and Y-axis directions and the rotation angle error around the Z-axis are overcome.

[0046] The convex surface of the mold 5 is the surface to be machined, and the bottom surface is flat. Four sinking grooves are opened at the edge of the upper surface of the mold 5. The four sinking grooves are evenly distributed around the mold 5. The bottom of the sinking groove is a small plane 6. Two conical holes 7 are opened on two of the small planes 6. The two conical holes 7 are symmetrically arranged along the center of the mold 5.

[0047] As Figure 2 and Figure 3As shown in the figure, it is respectively the flow chart of the distribution measurement method of the spatial attitude of the mold with a flat bottom surface and the schematic diagram of the composition structure of the measurement system. The measurement device consists of four parts: a three-dimensional high-precision motion mechanism 1 equipped with a line laser profiler 2, an XYZ three-way angular deviation measurement and control system 3, and a control computer 4. The four three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2 automatically scan and measure several small planes 6 distributed at the four corners or four edges of the upper surface of the mold 5 and any two conical holes 7 on the diagonal or opposite-side small planes under the control of the control system, and calculate the angular deviations of the upper surface of the mold 5 in the X, Y, and Z directions according to the measurement results, so as to determine the spatial attitude of the mold 5. In addition, the XYZ three-way angular deviation measurement and control system 3 also includes a plane rotation angle calculation module, a plane rotation angle evaluation module, a positioning line rotation angle calculation module, and a positioning line rotation angle evaluation module, which are used for real-time acquisition and analysis of the three-dimensional measurement data of the line laser profiler 2 and the angular deviation evaluation of the mold 5 in the XYZ three directions.

[0048] The four three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2 are distributed and installed at four positions on the workbench 8, and the control computer 4 installed with the XYZ three-way angular deviation measurement and control system 3 is also placed on the workbench 8.

[0049] The three-dimensional high-precision motion mechanism 1 includes a longitudinal guide rail, a vertical guide rail, and a transverse guide rail that are perpendicular to each other in pairs. The longitudinal guide rail is horizontally arranged and fixedly connected to the workbench. The vertical guide rail is vertically arranged, and its bottom is slidably connected to the longitudinal guide rail. The transverse guide rail is horizontally arranged, and its middle part is slidably connected to the vertical guide rail. The laser profiler 2 is installed on the transverse guide rail, and the installation position of the laser profiler 2 can be finely adjusted.

[0050] The three-dimensional high-precision motion mechanism 1 also includes three servo linear drivers powered by servo motors. The three servo linear drivers are respectively connected to the ends of the longitudinal guide rail, the bottom of the vertical guide rail, and the ends of the transverse guide rail. By driving the sliders on the vertical guide rail with the three servo linear drivers, the transverse guide rail can move up and down in the vertical direction, or by driving the sliders on the longitudinal guide rail, the vertical slide rail can move back and forth in the horizontal direction, or by driving the sliders on the transverse guide rail fixedly installed with the line laser profiler 2, the sliders can move back and forth in the horizontal direction.

[0051] As Figure 4 As shown in the figure, it is the schematic diagram of the control principle of the XYZ three-way angular deviation measurement and control system. The upper computer software in the control computer 4 sends motion displacement commands to the multi-axis motion controller, and the multi-axis motion controller controls the servo motors in each servo linear driver, so as to control the three-dimensional high-precision motion mechanism 1 equipped with the laser profiler 2 to perform XYZ three-way motion.

[0052] During the movement, the multi-axis motion controller can read the values of the grating scales in each servo linear drive and combine with the servo motor encoder to achieve precise control of the motor movement, so as to achieve the purpose of closed-loop control. The closed-loop feedback control ensures the motion accuracy of the module.

[0053] The parallelism error measurement can be divided into contact measurement using a contact displacement sensor and non-contact measurement using laser scanning measurement according to different measurement sensors; in this case, the non-contact parallelism error measurement method is adopted, as Figure 5 shown, and the contact measurement is used to measure the repeat positioning accuracy of the three-dimensional motion mechanism.

[0054] The measurement data acquisition can be carried out by scanning measurement in the point cloud mode and the profile mode of the online laser profiler. In the point cloud mode, scanning measurement is carried out in the profile mode by four sets of three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2. The line laser profiler represents the profile using a series of measurement points, and each measurement point represents the distance relative to the origin. Each measurement point contains a height (Z-axis) and a position (X-axis) coordinate in the sensor's field of view.

[0055] The data generated in the profile mode can be in two formats: with and without uniform spacing. In this case, the format with uniform spacing is adopted. The uniform spacing is enabled in the scan mode panel of the scan page. After enabling the uniform spacing, the range that constitutes the profile is resampled so that the spacing along the laser line (X-axis) is evenly distributed. When the line laser sensor is in the profile mode, each scan can generate a line profile. By moving the sensor a certain distance along a straight line on the measured surface, a series of surface profile data can be obtained. By collecting these profile data containing surface information and performing data processing, the measurement process can be realized.

[0056] The automatic measurement mode of the line laser movement means that after the three-dimensional high-precision motion mechanism 1 is initialized, it automatically returns to the initial point, then moves to the safety waiting point and triggers the line laser sensor. The line laser sensor mode is set to the profile mode and the distance measurement tool is started to judge the height distance h from the workpiece. The line laser sensor moves downward. When h is less than the specified value, it stops moving and switches to the point cloud or profile mode, and then moves horizontally to perform the scan measurement operation.

[0057] The line laser sensor adopts the encoder trigger method during the measurement process. Therefore, it needs to interact with the three-dimensional motion control. When the three-dimensional motion mechanism reaches the initial point position of the measurement, the encoder signal in the motion control data is transmitted to the line laser sensor for triggering.

[0058] Meanwhile, in view of the deviation between the measurement features and the ideal measurement reference that may occur during the scanning measurement process, a line laser sensor with a line width exceeding the diameter of the reference hole is used to perform a linear scanning measurement on the measurement area. The scanning speed is fast, and the requirements for the motion mechanism are relatively low compared to contact measurement. To make the measurement features of the forming die adapt to the line laser scanning measurement method, it is necessary to perform a certain modification on the measurement feature holes and then use a line laser profiler for measurement. The modification method used is to chamfer or countersink the intersection circle of the measurement feature plane and the measurement feature hole. After modification, there is still an intersection circle, but it is not a measurement feature. The modified feature hole and the modified area have an intersection circle, and this intersection circle is used as the measurement feature of the angular error, which is not affected by bumps, wear, etc. during the handling process.

[0059] This case is measured according to the following method:

[0060] S1. System calibration: Establish a coordinate transformation model for the system, mainly including the coordinate system of the laser profiler (O L -X L Y L Z L ), the coordinate system of the three-dimensional high-precision motion mechanism (O P -X P Y P Z P ), and the coordinate system of the machine tool (O M -X M Y M Z M ). To achieve the unification of the coordinate systems in the measurement system, it is necessary to obtain the transformation matrix between the coordinate systems through calibration. First, calibrate the coordinate system of the laser profiler to the coordinate system of the motion mechanism, and solve the coordinate transformation relationship between the three-dimensional high-precision motion mechanism coordinate system and the machine tool coordinate system through the Gauss-Newton iteration method to achieve the unification of the coordinate systems. Due to the installation error, there is a deviation between the actual position and the theoretical position of the laser profiler. Therefore, a reliable laser profiler pose calibration method is required. In this case, the coordinate system of the laser profiler O L -X L Y L Z L is unified with the three-dimensional motion mechanism coordinate system O P -X P Y P Z P through the Gauss-Newton iteration.

[0061] S2. Mechanism initialization: Initialize the XYZ three-way angular measurement and control system, the laser profiler, and the three-dimensional high-precision motion mechanism;

[0062] S3. Three-dimensional high-precision motion mechanism control: The four sets of three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2 automatically scan and measure four small planes 6 distributed at the four corners or four sides of the mold 5 surface and two conical holes 7 under the control of the control system. Specifically: The four sets of three-dimensional high-precision motion mechanisms 1 equipped with line laser profilers 2 automatically scan and measure the measured surfaces distributed at the four corners or four sides of the upper surface of the mold 5 from one side to the other; first measure several small planes 6 on the upper surface of the mold 5, and then measure any two conical holes 7 on the diagonal or opposite-side small planes 6.

[0063] Before scanning, a certain modification is made to the measurement feature holes and then measured using the line laser profiler 2. The data generated in the contour mode can be enabled in the scan mode panel of the scan page with a uniform spacing. After enabling the uniform spacing, the range constituting the contour will be resampled so that the spacing along the laser line (X-axis) is evenly distributed.

[0064] S4. Real-time displacement data acquisition: During the scanning and measurement process, the line laser profiler 2 is in the contour mode. The XYZ three-way deflection measurement and the control system 3 read a contour line data generated by the line laser profiler 2 at regular intervals until the scanning is completed, and finally obtain a series of measured surface contour line data, and collect this contour data containing surface information.

[0065] S5. Data processing:

[0066] S5.1. Fitting the small plane on the upper surface of the mold to obtain the plane equation: Sort the data points of each small plane 6 collected according to the Z coordinate value, remove a small part of the largest points at the front and a small part of the smallest points at the back, convert all the remaining data points from the local coordinate system of the line laser profiler to the machine tool coordinate system, and perform spatial plane fitting by the least squares method. The principle of the least squares evaluation method is that the most reliable value of the measurement result should be solved under the condition that the sum of the squares of the residual errors is the smallest. Let: Be the smallest, that is

[0067]

[0068] x i 、y i 、z i : The coordinate values of the measured data points

[0069] Q: The sum of the squares of the residual errors

[0070] B, B, C are the equation coefficients of the plane equation Ax + By - z + C = 0;

[0071] After determining the values of A, B, and C in the coefficient matrix, the equation of the fitting plane can be obtained as Ax + By - z + C = 0. After obtaining the plane, find the normal vector of the plane to obtain the deflection angles of the upper surface of the mold with respect to the two coordinate axes, that is, with respect to the X-axis and Y-axis of the machine tool coordinate system.

[0072] S5.2. Fit a straight line through the center coordinates of two holes on the small plane of the upper surface of the mold to obtain the straight line equation: For the two center coordinates (i.e., the fixed points of the conical surface of the conical hole) measured on the two conical holes 7, convert them from the local coordinate system of the line laser profiler to the machine tool coordinate system respectively, calculate the spatial straight line equation represented by these two points, and obtain the angle between the projection of this straight line on the XOY plane and the X-axis (or Y-axis), that is, the rotation angle around the Z-axis; thus, obtain the rotation angle of the upper surface of the mold 5 around the Z-axis.

[0073] S5.3. Obtain the spatial pose of the mold: After obtaining the deflection angles of the upper surface of the mold (5) with respect to the X-axis and Y-axis of the machine tool coordinate system and the rotation angle around the Z-axis through steps S5.1 and S5.2, the spatial pose of the mold (5) can be obtained.

[0074] Finally, according to the deflection angles of the upper surface of the mold 5 with respect to the X-axis and Y-axis of the machine tool coordinate system and the rotation angle around the Z-axis, the lengths of the respective adjustable support columns can be adjusted separately to keep the mold 5 in a horizontal state for facilitating the machining of the top surface of the mold.

[0075] In summary, the embodiment of the present invention provides a distributed precision measurement method and device for the spatial pose of large-size flat molds. The measurement device can realize the function of calculating and evaluating the deflection angles of the spatial pose of the measured mold, with fast measurement speed, high efficiency and accuracy, a repeated measurement accuracy of up to 10 to 20 microns, high system real-time performance, and can also realize the function of calculating and evaluating the deflection angles of the spatial pose of the measured mold, overcoming the deficiencies of the traditional measurement methods and devices for the spatial pose of large-size flat molds.

[0076] There are many specific implementation ways of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements can be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A distributed precision measurement method for the spatial attitude of large-sized flat molds, characterized in that, The described measurement method is implemented based on a measurement device; The measurement device includes four three-dimensional high-precision motion mechanisms (1) equipped with line laser profilers (2), an XYZ three-way deflection measurement and control system (3), and a control computer (4). The four three-dimensional high-precision motion mechanisms (1) and the control computer (4) are both installed on a workbench (8), and the XYZ three-way deflection measurement and control system (3) is installed on the control computer (4). The four three-dimensional high-precision motion mechanisms (1) are respectively controlled by the XYZ three-way deflection measurement and control system (3) so that the four line laser profilers (2) fixedly installed on the transverse guide rails of the four three-dimensional high-precision motion mechanisms (1) perform motions in the X, Y, and Z directions respectively; The XYZ three-way deflection measurement and control system (3) is used for real-time acquisition and analysis of the three-dimensional measurement data of the laser profiler (2) and evaluation of the deflection angles of the mold (5) in the XYZ three directions; The measurement is carried out according to the following method: S1. System calibration: Establish a coordinate transformation model for the system, mainly including the coordinate system of the laser profiler (O L -X L Y L Z L ), the coordinate system of the three-dimensional high-precision motion mechanism (O P -X P Y P Z P ), and the machine tool coordinate system (O M -X M Y M Z M ). In order to unify the coordinate systems in the measurement system, it is necessary to obtain the transformation matrix between the coordinate systems through calibration; first, calibrate the coordinate system of the laser profiler to the coordinate system of the motion mechanism, and solve the coordinate transformation relationship between the three-dimensional high-precision motion mechanism coordinate system and the machine tool coordinate system through the Gauss-Newton iteration method to achieve the unification of the coordinate systems; S2. Mechanism initialization: Initialize the XYZ three-way deflection measurement and control system, the laser profiler, and the three-dimensional high-precision motion mechanism; S3. Control of the three-dimensional high-precision motion mechanism: The four three-dimensional high-precision motion mechanisms (1) equipped with line laser profilers (2) respectively perform automatic scanning measurements on the measured surfaces at the four corners or four edges of the upper surface of the mold (5) from one side to the other side. First, measure several small planes (6) on the upper surface of the mold (5), and then measure any two conical holes (7) on the diagonal or opposite-side small planes (6); S4. Real-time displacement data acquisition: During the scanning measurement process, the line laser profiler (2) is in the contour mode. The XYZ three-way deflection measurement and control system (3) reads a contour line data generated by the line laser profiler (2) at regular intervals until the scanning is completed, and finally obtains a series of measured surface contour line data, and collects these contour data containing surface information; S5. Data processing: S5.

1. Fit the small plane on the upper surface of the mold to obtain the plane equation: Sort the data points of each small plane (6) collected according to the Z coordinate value, remove a small part of the largest points at the front and a small part of the smallest points at the back, convert all the remaining data points from the local coordinate system of the line laser profiler to the machine tool coordinate system, and perform spatial plane fitting by the least squares method. The principle of the least squares evaluation method is that the most reliable value of the measurement result should be solved under the condition that the sum of the squares of the residual errors is the smallest. Let: be the smallest, that is x i 、y i 、z i : Coordinate values of the measured data points Q: Sum of squares of residual errors A, B, and C are the equation coefficients of the plane equation Ax + By - z + C = 0; After determining the values of A, B, and C in the coefficient matrix, the equation of the fitted plane can be obtained as Ax + By - z + C = 0. After obtaining the plane, find the normal vector of the plane, and then the deflection angles of the upper surface of the mold with respect to the two coordinate axes, that is, with respect to the X-axis and Y-axis of the machine tool coordinate system, can be obtained; S5.

2. Obtain the straight line equation by fitting a straight line through the center coordinates of two holes on the small plane of the upper surface of the mold: The two center coordinates obtained by measuring the two conical holes (7) are respectively converted from the local coordinate system of the line laser profiler to the machine tool coordinate system, calculate the spatial straight line equation represented by these two points, and obtain the included angle between the projection of this straight line on the XOY plane and the X-axis or Y-axis, that is, the rotation angle around the Z-axis; S5.

3. Obtain the spatial pose of the mold: After obtaining the deflection angles of the upper surface of the mold (5) with respect to the X and Y axes of the machine tool coordinate system and the rotation angle around the Z-axis through steps S5.1 and S5.2, the spatial pose of the mold (5) can be obtained.

2. The distributed precision measurement method for the spatial attitude of a large-size flat die according to claim 1, wherein A plurality of vertically arranged adjustable support columns are fixedly connected to the workbench (8), and the mold (5) is placed on the plurality of adjustable support columns. The lengths of the plurality of adjustable support columns are respectively adjusted in combination with the data of the control computer (4), and finally the mold (5) is kept in a horizontal state; The convex surface of the mold (5) is the surface to be processed, and the bottom surface is flat. Four sinking grooves are formed at the edge of the upper surface of the mold (5). The four sinking grooves are evenly distributed around the mold (5). The bottom of the sinking groove is a small plane (6), and two of the small planes (6) are provided with conical holes (7). The two conical holes (7) are symmetrically arranged about the center of the mold (5).

3. A distributed precise measurement method for the spatial attitude of a large-sized flat mold according to claim 1, characterized in that Four three-dimensional high-precision motion mechanisms (1) equipped with line laser profilers (2) are respectively installed in four directions of the workbench (8), and the control computer (4) equipped with the XYZ three-direction deviation measurement and control system (3) is also placed on the workbench (8).

4. A distributed precision measurement method for the spatial attitude of a large-size flat mold according to claim 1, characterized in that The three-dimensional high-precision motion mechanism (1) includes a longitudinal guide rail, a vertical guide rail and a transverse guide rail that are perpendicular to each other in pairs. The longitudinal guide rail is horizontally arranged and fixedly connected to the workbench. The vertical guide rail is vertically arranged and its bottom is slidably connected to the longitudinal guide rail. The transverse guide rail is horizontally arranged and its middle part is slidably connected to the vertical guide rail. The laser profiler (2) is installed on the transverse guide rail, and the installation position of the laser profiler (2) can be finely adjusted; The three-dimensional high-precision motion mechanism (1) further includes three servo linear drivers with servo motors as power sources. The three servo linear drivers are respectively connected to the ends of the longitudinal guide rail, the bottom of the vertical guide rail and the ends of the transverse guide rail. The vertical guide rail is driven to move up and down in the vertical direction, or the longitudinal guide rail is driven to move back and forth linearly in the horizontal direction, or the transverse guide rail fixedly installed with the line laser profiler (2) is driven to move back and forth in the horizontal direction by the three servo linear drivers.

5. A distributed precision measurement method for the spatial attitude of a large-size flat mold according to claim 1, characterized in that The control computer (4) sends motion displacement commands to the multi-axis motion controller, and the multi-axis motion controller controls the servo motors in each servo linear driver, so as to control the three-dimensional high-precision motion mechanism (1) equipped with the laser profiler (2) to perform XYZ three-direction motion.

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