A device and method for automatic calibration of a smooth ring gauge

Abstract

The application discloses a kind of smooth ring gauge automatic calibration device and method, the device includes clamping positioning unit, visual identification unit, measuring unit and computer control system, measuring unit includes metrology coordinate measuring machine, automatic calibration module and temperature acquisition unit, visual identification unit includes line laser vision sensor and image processing module, computer control system is used to realize the data transmission and cooperation between each module or unit, line laser vision sensor is scanned to point cloud data using laser triangulation to smooth ring gauge 3D profile, image processing module identifies and analyzes point cloud data, obtains the geometric characteristic information of smooth ring gauge, automatic calibration module adjusts measurement scheme in real time according to geometric characteristic information, metrology coordinate measuring machine executes the full parameter measurement of smooth ring gauge according to adjusted measurement scheme.The application can realize the full parameter, high efficiency, high precision, integrated automatic calibration of smooth ring gauge.

Description

Technical Field

[0001] This invention belongs to the field of metrology, calibration and testing, and specifically relates to an automatic calibration device and method for smooth ring gauges. Background Technology

[0002] Smooth ring gauges are physical measuring tools used to control the limit dimensions of workpieces and reproduce the high-precision internal dimensions of various parts. Their measurement parameters cover diameter, diameter variation, roundness, and straightness. To ensure the accuracy and reliability of smooth ring gauge measurements across various industries, periodic value transfer or traceability is necessary. Current research focuses primarily on improving the measurement accuracy of length measuring machines and enhancing temperature measurement systems. However, there is insufficient research on automating the overall calibration process for all parameters and addressing issues such as low accuracy and efficiency in measuring special limit dimensions. Existing technologies, which use high-grade standard ring gauges in conjunction with high-precision length measuring instruments to measure the diameter and diameter variation of smooth ring gauges, and roundness and straightness using roundness meters, have the following limitations:

[0003] 1) Due to the limited number of high-grade standard ring gauges, the machining consistency error of the double measuring hooks of the length measuring instrument will gradually increase with the increase of the measurement stroke, ultimately affecting the accuracy of the measurement results;

[0004] 2) When using the comparison method for measurement, the clamping of the smooth ring gauge will introduce a secondary centering error;

[0005] 3) Due to limitations in the machining of double measuring hooks, worktable stroke, and load-bearing capacity, high-precision measurement capabilities cannot be achieved or guaranteed for smooth ring gauges smaller than φ15mm and larger than φ150mm.

[0006] 4) In addition to measuring the diameter and variation of the smooth ring gauge, it is also necessary to use a roundness tester to measure the straightness and roundness, and to perform isothermal, secondary clamping, and leveling operations again, which results in low measurement efficiency. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the prior art by providing an automatic calibration device and method for smooth ring gauges, which can achieve full-parameter, high-efficiency, high-precision, and integrated automated calibration of smooth ring gauges.

[0008] To achieve the above objectives, one aspect of the present invention provides an automatic calibration device for smooth ring gauges, comprising a clamping and positioning unit, a vision recognition unit, a measurement unit, and a computer control system.

[0009] The measurement unit includes a metrological coordinate measuring machine, an automated calibration module, and a temperature acquisition unit. The visual recognition unit includes a line laser vision sensor and an image processing module. The computer control system is connected to the metrological coordinate measuring machine, the automated calibration module, the temperature acquisition unit, the line laser vision sensor, and the image processing module to realize data transmission and collaboration between the metrological coordinate measuring machine, the automated calibration module, the temperature acquisition unit, the line laser vision sensor, and the image processing module.

[0010] The clamping and positioning unit is installed on the movable worktable of the metrology coordinate measuring machine for clamping and positioning the smooth surface ring gauge to be measured. The line laser vision sensor is installed above the movable worktable of the metrology coordinate measuring machine and works in conjunction with the movable worktable to scan the 3D contour of the smooth surface ring gauge using laser triangulation to obtain point cloud data. The image processing module uses a deep learning-based image recognition algorithm to identify and analyze the point cloud data of the 3D contour of the smooth surface ring gauge to obtain the geometric feature information of the smooth surface ring gauge, which is transmitted to the automatic calibration module in real time. The automatic calibration module adjusts the measurement scheme in real time according to the received geometric feature information of the smooth surface ring gauge. The metrology coordinate measuring machine performs full parameter measurement of the smooth surface ring gauge according to the adjusted measurement scheme.

[0011] The temperature acquisition unit includes multiple temperature sensors installed on the metrological coordinate measuring machine and the smooth ring gauge under test. These sensors are used to monitor and acquire the temperature changes of the environment during the measurement process in real time and transmit the data to the automated calibration module. The automated calibration module corrects the measurement results of the smooth ring gauge based on the received environmental temperature changes.

[0012] Another aspect of the present invention provides an automatic calibration method for a smooth ring gauge, which utilizes the above-described apparatus to perform automatic calibration of the smooth ring gauge, comprising:

[0013] Place the smooth ring gauge on the clamping and positioning unit to complete the clamping, and align the center of the smooth ring gauge with the center of the measurement coordinate system;

[0014] The movable worktable of the metrology coordinate measuring machine moves and works with the line laser vision sensor to complete the 3D contour scanning of the smooth surface ring gauge. The image processing module extracts the geometric feature information and transmits it to the automatic calibration module.

[0015] The automated calibration module adaptively adjusts the measurement scheme of the metrology coordinate measuring machine based on the received geometric feature information, and the metrology coordinate measuring machine performs full parameter measurement of the smooth ring gauge according to the adjusted measurement scheme.

[0016] The computer control system transmits the data measured by the metrological coordinate measuring machine to the paperless certificate entry system in real time. The paperless certificate entry system then outputs a calibration report for the smooth ring gauge, thus completing the entire calibration process for the smooth ring gauge from measurement to report output.

[0017] The automatic calibration device and method for smooth ring gauges described above combine machine vision and coordinate measurement technology, overcoming the problems of incomplete standard ring gauge configuration, secondary clamping error, consistency error in the processing of double measuring hooks, limited measurement range, and low measurement efficiency in traditional smooth ring gauge calibration. Through a single clamping, full-parameter, high-efficiency, high-precision, and integrated automated calibration can be achieved. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0019] Figure 1 This is a schematic block diagram of an automatic calibration device for a smooth ring gauge according to an embodiment of the present invention;

[0020] Figure 2 This is a three-dimensional structural schematic diagram of an automatic calibration device for a smooth ring gauge according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] One embodiment of the present invention provides an automatic calibration device for a smooth ring gauge. For example... Figure 1 As shown, the automatic calibration device for smooth ring gauges in this embodiment of the invention includes a clamping and positioning unit, a vision recognition unit, a measurement unit, and a computer control system. The measurement unit includes a metrology coordinate measuring machine, a temperature acquisition unit, and an automatic calibration module. The vision recognition unit includes a line laser vision sensor and an image processing module.

[0023] like Figure 2 As shown, the metrology coordinate measuring machine 2, as the measuring body, is located at the center of the overall device. The clamping and positioning unit 5 is installed on the movable worktable 6 of the metrology coordinate measuring machine 2 for clamping and positioning the light surface ring gauge to be measured. The line laser vision sensor 3 is installed directly above the movable worktable 6 of the metrology coordinate measuring machine 2 to acquire the three-dimensional (3D) contour information of the light surface ring gauge.

[0024] The visual recognition unit includes a line laser vision sensor 3 and an image processing module. The line laser vision sensor 3 collaborates with the movable worktable 6 of the metrology coordinate measuring machine 2, using the laser triangulation measurement principle to scan the 3D contour of the smooth ring gauge. The image processing module utilizes a deep learning-based image recognition algorithm to identify and analyze the collected point cloud data, accurately identifying key elements such as the shape, size range, and special markings of the smooth ring gauge, separating the effective diameter and thickness of the smooth ring gauge, and providing real-time information to the automated calibration module for adaptive calibration. The automated calibration module dynamically adjusts the measurement scheme based on the smooth ring gauge feature information output by the visual recognition unit, such as probe selection, path planning, and measurement point distribution, generating a new measurement program. This program drives the metrology coordinate measuring machine to perform full-parameter measurement tasks for different types of smooth ring gauges. The full parameters of the smooth ring gauge include diameter, diameter variation, roundness, and straightness measurements.

[0025] The clamping and positioning unit 5 employs a self-centering fixture to clamp different types of smooth ring gauges. Through servo motor stepping, the servo motor outputs appropriate torque and speed to achieve accurate clamping and positioning, reducing positioning errors and preventing interference with the probe path of the metrology coordinate measuring machine. The self-centering fixture can be of any centering principle and structural form, such as air-bearing or mechanical elastic centering, as long as clamping accuracy is guaranteed and it is suitable for smooth ring gauges of different shapes.

[0026] Temperature acquisition unit 4 is used to acquire the real-time temperature of the smooth ring gauge and monitor ambient temperature fluctuations during the measurement process, thereby enabling temperature monitoring and correction of measurement results. Specifically, the ambient temperature acquisition unit may include multiple temperature sensors installed on the metrological coordinate measuring machine and the smooth ring gauge under test, for real-time monitoring and acquisition of ambient temperature changes during the measurement process and transmission to the automated calibration module. The automated calibration module corrects the measurement results of the smooth ring gauge based on the received ambient temperature changes.

[0027] The computer control system 1 is connected to the metrology coordinate measuring machine 2, the automatic calibration module, the temperature acquisition unit 4, the line laser vision sensor 3, and the image processing module. It is used to realize signal interaction, data transmission, cooperation, and synchronization among the metrology coordinate measuring machine, the automatic calibration module, the temperature acquisition unit, the line laser vision sensor, and the image processing module.

[0028] The automatic calibration device for smooth ring gauges in this embodiment of the invention may further include a paperless certificate entry system. This system is a data processing unit for smooth ring gauge certificates and is connected to a computer control system and a metrological coordinate measuring machine (CMM). The computer control system transmits the data measured by the CMM to the paperless certificate entry system in real time, completing the entire calibration process for the smooth ring gauge from measurement to report output. The computer control system includes a data transmission module to achieve efficient and accurate data connection and synchronization between the CMM and the paperless entry system, ensuring that calibration result data is transmitted to the paperless entry system in real time and completely, while also guaranteeing correct data format conversion. Data transmission is performed using a reliable network communication protocol based on the data format requirements of both systems through a dedicated data interface program.

[0029] The automatic calibration device for smooth ring gauges in this invention utilizes the laser triangulation measurement principle and coordinate measurement technology. It enables a line laser vision sensor to work in conjunction with a movable worktable and a self-centering fixture to scan the 3D contour of the smooth ring gauge. The image processing module analyzes the geometric features and outputs the data. Simultaneously, the automatic calibration module generates a calibration program based on the data output by the image processing module and drives a metrology coordinate measuring machine to perform the measurement task, thereby achieving high-precision automatic measurement of all parameters of the smooth ring gauge.

[0030] This invention also provides an automatic calibration method for smooth ring gauges, which utilizes the automatic calibration device for smooth ring gauges according to this invention to perform automatic calibration of smooth ring gauges, including the following stages:

[0031] 1. Preparation stage before calibration

[0032] Place the smooth ring gauge on the self-centering fixture and turn on the power supply of the self-centering fixture. At this time, the three-jaw support arm on the self-centering fixture completes the clamping under the interaction of the servo motor and the spiral mechanical structure, aligning the center of the smooth ring gauge with the center of the measurement coordinate system.

[0033] 2. Image recognition stage

[0034] The automated calibration module is activated, triggering the movement of the movable worktable of the metrology coordinate measuring machine. In collaboration with the line laser vision sensor, it completes the 3D contour scanning of the smooth ring gauge. The image processing module automatically measures key elements such as the size and thickness of the smooth ring gauge, and the output file is stored in txt format in a specified path for the automated calibration module to read in real time.

[0035] 3. Calibration procedure generation and measurement task execution phase

[0036] The automated calibration module adaptively adjusts the coordinate measuring machine's measurement program and path planning based on the received data information, generates a measurement plan, and the metrology-type coordinate measuring machine executes the measurement plan to complete the measurement of all parameters of the smooth ring gauge.

[0037] In one embodiment, the automated calibration module utilizes the LOAPRC command in the Quindos7 operating system to automatically import information such as ring gauge height and inner / outer diameter automatically generated by the image processing module. It reads the smooth ring gauge information in real time and automatically integrates it as variables into the automatic measurement program to generate a calibration program. The calibration program includes: importing external TXT text data, converting the TXT text data into character variable data, processing the data into a data type recognizable by Quindos7, assigning the imported data as variables to the ring gauge inspection program, generating inspection elements and measurement elements, and evaluating the fit to output the measurement results.

[0038] By utilizing an image processing module and a metrology-type coordinate measuring machine (Quindos7) operating system, and employing highly user-friendly TXT text data as the medium for information transmission, this approach bypasses the traditional, costly, and technically challenging control cabinet systems. This allows for the integration of different measuring and automated equipment, significantly improving measurement efficiency and reducing the integration cost of intelligent inspection automation systems. Ultimately, the metrology-type coordinate measuring machine performs calibration tasks, completing the measurement of all parameters of the smooth ring gauge, including the detection, acquisition, separation, extraction, fitting, and evaluation of the smooth ring gauge's surface profile.

[0039] 4. Data processing and transmission stage

[0040] The computer control system interfaces with the coordinate measuring machine via a dedicated data interface, transmitting measurement data in real time to the paperless certificate entry system, thus completing the closed loop of the entire calibration process for the smooth ring gauge, from measurement to the synchronous output of the certificate report.

[0041] Before performing calibration, the method of this invention also includes, in order to improve calibration accuracy, calibration of the geometric parameter error of the coordinate measuring machine, effective compensation for probe diameter and detection error, temperature monitoring and result correction, and optimization of probe detection speed and approximation distance.

[0042] 1. Calibration of geometric parameter errors of coordinate measuring machine

[0043] The calibration accuracy of the coordinate measuring machine (CMM) determines the measurement capability of the device of this invention. Its geometric parameter errors, based on their effect in each degree of freedom of motion, are divided into 3 positional errors, 6 straightness errors, 9 angular pendulum errors, and 3 perpendicularity errors between the three axes, totaling 21 parameter errors. Because the functional relationships of these 21 parameter errors are complex and cannot be analyzed individually, calibration is performed separately in seven spatial directions to reflect the comprehensive error of the CMM, providing significant representativeness. Compared to calibration using laser interferometers and gauge blocks, this method offers greater flexibility in spatial arrangement and more refined measurement intervals.

[0044] The calibration method of this invention is based on the principle of spatial geometric similarity and a multi-parameter fitting algorithm. First, a 620mm step gauge, along with a special fixture, is mounted on the worktable of a coordinate measuring machine (CMM) to form a specific geometric relationship with the machine's coordinate axes. The CMM probe measures the standard spacing of the step gauge according to a predetermined path in the calibration program, acquiring a series of measurement data. By comparing these measurement data with the reference values ​​of the step gauge, the measurement error is decomposed into the directions of the CMM's various motion axes and inter-axis coupling directions using spatial geometric similarity transformation. Then, a multi-parameter fitting algorithm is used to construct a geometric error model in each direction. This model accurately describes the geometric error variation of the CMM under different positions and attitudes. When actually measuring a smooth ring gauge, the corresponding error compensation value is extracted from the error model based on the coordinate information of the measurement points, and the measurement results are corrected in real time to ensure measurement accuracy.

[0045] In one embodiment, a step gauge is used at 20mm intervals. Through the cooperation of the computer control system and the measurement unit, calibration is performed in seven directions in space. The calibration error is compensated into the coordinate measuring machine, and the overall error can be controlled within 0.6μm. This provides a higher measurement capability for the device of the present invention to achieve adaptive calibration of multi-specification smooth ring gauges.

[0046] Traditional calibration methods struggle to comprehensively and accurately quantify the complex geometric errors of coordinate measuring machines (CMMs). This invention's geometric parameter error calibration method employs a step gauge with ultra-high precision and stability, combined with advanced software compensation algorithms. This method can accurately identify and subdivide the geometric parameter errors of the CMM in seven spatial directions, including minute positioning errors, rotational errors, and inter-axis perpendicularity errors. It effectively overcomes the limitations of traditional calibration techniques, significantly improving the accuracy and reliability of CMM geometric parameter calibration, and providing a solid foundation for subsequent high-precision measurements using smooth ring gauges.

[0047] 2. Effective compensation for probe diameter and detection error

[0048] The calibration of a smooth ring gauge requires the probe to probe the inner surface contour of the gauge. Therefore, the effective diameter and shape error of the probe directly affect the final calibration accuracy of the smooth ring gauge. Thus, it is necessary to correct the probe diameter and probe error before calibration to better suit the high-precision measurement requirements of the smooth ring gauge.

[0049] Traditional calibration methods involve using a standard sphere and following a corresponding calibration procedure, writing the probe's actual diameter and detection error into the program. However, this type of calibration, performed according to a predetermined procedure, involves the probe detecting the overall contour of the standard sphere, and the data written into the program is actually the probe's sphere diameter and sphericity. Since the calibration of the diameter and roundness of a smooth ring gauge is in two-dimensional space, using the calibrated sphere diameter and sphericity to approximate the diameter and roundness introduces calibration errors.

[0050] Therefore, the method of this embodiment of the invention adopts the in-situ calibration method, selecting a probe with a roundness error of <0.2μm as a reference probe. A high-precision length measuring machine and a roundness meter are used to measure the diameter and roundness error respectively. Combining the open-source functions of the metrological coordinate measuring machine operating system (Quindos7) in the measurement unit, the measured diameter and roundness error are written into the program to correct the effective diameter of the probe and the detection error. Subsequently, the method is repeated 10 times using a calibrated standard ring gauge (roundness 0.5μm, diameter 40.0001mm) to verify its effectiveness. The measurement results are shown in Table 1.

[0051]

[0052] As shown in Table 1, the differences between the diameter and roundness measurements and the reference values ​​are all ≤0.2μm, which verifies the accuracy and feasibility of the in-situ calibration method.

[0053] By using the in-situ calibration method to calibrate the probe diameter and detection error, the true value of roundness and the radial diameter of the probe can be cleverly separated from the approximate diameter and roundness obtained from traditional calibration. This provides reliable measurement accuracy for accurately measuring the roundness and straightness of smooth ring gauges, making the probe more suitable for high-precision measurement needs.

[0054] 3. Temperature monitoring and result correction

[0055] Ensuring a constant temperature during the measurement process is the primary condition for achieving high-precision calibration of the smooth ring gauge. The method of this invention is based on heat conduction theory and a multivariate regression analysis algorithm. First, high-precision temperature sensors are strategically placed in key structural components of the coordinate measuring machine (CMM), such as the coordinate axis guide rails and the smooth ring gauge being measured, constructing a complete temperature sensing network as a temperature acquisition unit. This network collects temperature data from various components in real time and transmits this data to the CMM's automated calibration module. Simultaneously, using a multivariate regression analysis algorithm, a quantitative relationship model between temperature change and measurement error is established based on extensive experimental and actual measurement data. During the measurement process, the real-time monitored temperature data is substituted into the relationship model to calculate the temperature-induced measurement error. This error is then corrected by the automated calibration module, effectively separating the temperature-induced measurement error from the measurement results.

[0056] The method of this invention adopts a temperature compensation optimization scheme based on a high-precision temperature sensing network and dynamic model correction. Considering the impact of temperature changes on measurement accuracy during the measurement process, multiple high-precision, high-response temperature sensors are used, which can monitor the temperature changes of key parts of the coordinate measuring machine and the smooth ring gauge in real time and accurately. The measurement error caused by temperature changes is accurately quantified, and the measurement results are corrected in real time through an automated calibration module. This effectively eliminates the interference of temperature changes on measurement accuracy and significantly improves the measurement stability and accuracy of the coordinate measuring machine under different ambient temperatures.

[0057] In one embodiment, 10 temperature sensors are used, with 9 evenly distributed within the travel range of the X, Y, and Z axes of the metrological coordinate measuring machine and 1 attached to the ring gauge of the measured surface. These sensors are used to monitor and collect the temperature changes of the environment during the measurement process in real time. The measurement results are corrected according to formula (1), and the corrected values ​​of the measurement results are written into the automatic calibration module and simultaneously transmitted to the paperless certificate entry system. The actual temperature value and the compensation value are recorded in the electronic certificate. The entire correction process is completely embedded in the automatic calibration process and requires no manual intervention.

[0058] (1)

[0059] In the formula:

[0060] — Correction value for the measurement result, in mm;

[0061] —Nominal diameter of smooth ring gauge, mm;

[0062] —Temperature of the coordinate measuring machine's grating ruler, in °C;

[0063] —Coefficient of linear expansion of the coordinate measuring machine's grating ruler, mm / ℃;

[0064] —Temperature of the smooth ring gauge, °C;

[0065] —Coefficient of linear expansion of smooth ring gauge, mm / ℃.

[0066] The temperature variation range during the measurement process was controlled within (20±0.5) ℃. Ten repeated measurements were performed using a smooth ring gauge with a diameter of φ320.022mm. The measurement data before and after temperature variation correction are shown in Table 2.

[0067]

[0068] The measurement data and comparison results in Table 2 show that the measurement results after correcting for temperature changes are closer to the reference values. This is especially important for measuring large-sized smooth ring gauges, where the impact of temperature changes and corrections during the measurement process must be carefully considered.

[0069] 4. Optimization of probe detection speed and approximation distance

[0070] As a key component of a metrology-type coordinate measuring machine, the trigger probe is crucial for reproducing high-precision measurements. In actual measurement processes, to improve measurement efficiency, the probe often approaches the workpiece at a relatively high speed, then reduces the speed when it reaches the approximate distance. The entire measurement process involves acceleration and deceleration phases, and the motion parameters change constantly. The dynamic error of the probe is the main factor affecting measurement accuracy.

[0071] The method of this invention measures a smooth ring gauge under different combinations of detection speed and approximation distance, collects performance index data such as measurement accuracy, measurement time, and repeatability, analyzes the intrinsic relationship between detection speed, approximation distance and measurement performance index, derives the optimal detection speed and approximation distance, and applies the optimized parameters to a coordinate measuring machine to achieve high efficiency while meeting the requirements of high-precision measurement.

[0072] Traditional detection parameter settings often rely on experience, making it difficult to achieve global optimization. The method in this invention, through extensive experimental measurements, has collected rich data on the relationship between detection speed, approximation distance, and the measurement accuracy and range of smooth ring gauges. By employing big data analytics to uncover the patterns behind this data, the optimal combination of detection speed and approximation distance can be automatically found, maximizing the dynamic measurement accuracy of the coordinate measuring machine. This meets the high-precision measurement requirements of smooth ring gauges across different size ranges, effectively improving measurement efficiency and quality.

[0073] In one embodiment, by changing the detection speed under different approach and retreat distances, the effective diameter (φ24.98604mm) of the calibrated standard ball was measured, and the difference was compared to confirm the optimal detection speed and approach distance parameters that the probe needs to be set. The test results are shown in Tables 3, 4, and 5.

[0074]

[0075] The experimental data in Tables 3, 4, and 5 show that the probe speed and approximation distance parameters should be set consistently with those used during probe calibration. Furthermore, the probe speed has a far greater impact on the measurement results than the approximation distance; therefore, this factor should be given full attention in high-precision measurements. Based on the above experimental data, the probe speed and approximation distance parameters in the automated calibration module should be consistent with those set during calibration to ensure that the dynamic error of the probe remains stable within ±0.2 μm during measurement.

[0076] The measurement capability of the automatic calibration device for smooth ring gauges according to embodiments of the present invention is verified below:

[0077] 1. Verification of repeatability and stability of the device

[0078] Measurement errors caused by factors such as the interaction between the line laser vision sensor and the metrological coordinate measuring machine, changes in environmental factors during the measurement process, and drift of the measurement system can all affect the measurement results. First, three smooth ring gauges of different sizes were selected within the measurement range, and the repeatability of the device was tested 10 times. Second, the stability of the standard ring gauge (φ40.0001mm) was tested 6 times at different time points. The test results show that the dispersion of the device's measurement repeatability and stability test results is ≤0.4μm, meeting the expected requirements.

[0079] 2. Accuracy verification based on second-class standard ring gauges

[0080] Once the measurement repeatability and stability of the device meet the expected requirements, an accuracy verification based on a second-class standard ring gauge is proposed to evaluate the calibration accuracy of the device. According to JJF 1117-2010 "Technical Specification for Metrological Comparison", the normalized deviation is calculated (see Formula 2) to verify the accuracy of the calibration results. The comparison data of the device calibration results are shown in Table 6.

[0081] (2)

[0082] —Normalization bias: if the positive data is <1, the result is satisfactory; if the positive data is >1, the result is unsatisfactory.

[0083] —Calibration results of the device, mm;

[0084] —Reference value for Class II standard ring gauges, mm;

[0085] — Measurement uncertainty of the apparatus, μm;

[0086] — Measurement uncertainty during traceability of a second-class standard ring gauge, in μm.

[0087]

[0088] Based on the comparison data and verification results in Table 6, the En values ​​are all less than 1, indicating satisfactory verification results. The calibration accuracy of the device meets the requirements, and its measurement capability is satisfactory. U =0.6μm +3.3×10 -6 L ( k =2).

[0089] Compared with the prior art, the automatic calibration device for smooth ring gauges in this invention has the following advantages:

[0090] (1) The measurement range has been expanded.

[0091] Compared to existing calibration methods for smooth ring gauges, which are typically limited to the φ15mm to φ150mm range due to the limitations of the length measuring instrument's grating ruler's measurement stroke and the minimum machining limit of the double measuring hooks, calibration technology for smooth ring gauges based on metrological coordinate measuring machines (CMMs) overcomes the measurement range limitations caused by the structure and probe of traditional length measuring instruments. The upper limit of the smooth ring gauge's measurement is determined by the working stroke of the CMM's grating ruler, while the lower limit of the smooth ring gauge's measurement is determined by the machining limit of the probe. Currently, the minimum machining limit of the probe can reach φ0.5mm, enabling the measurement of smooth ring gauges from φ2mm to φ500mm, significantly improving the measurement range.

[0092] (2) The measurement is more representative and comprehensive.

[0093] Based on the relevant requirements of JJG 343-2012 "Verification Procedure for Smooth Limit Gauges" and JJG 894-1995 "Verification Procedure for Standard Ring Gauges", the length measuring instrument needs to measure four positions of the smooth ring gauge in the vertical direction at sections A and B to reflect the shape error of the smooth ring gauge with the diameter variation. However, the position and wear of the smooth ring gauge in actual use are random. Controlling the diameter variation cannot fully reflect the actual shape error of the smooth ring gauge, and the representativeness of its measurement points is insufficient. In particular, for smooth gauges used in the aerospace field (such as dial indicator rings and dial indicator components), it is necessary to add roundness and straightness measurement requirements to fully reflect its shape characteristics. However, using a metrological coordinate measuring machine can realize uniform distribution of detection or scanning points throughout the entire measurement range of the smooth ring gauge, which more intuitively and comprehensively reflects its shape error.

[0094] (3) Improved measurement efficiency

[0095] The calibration items for smooth ring gauges include diameter, diameter variation, roundness, and straightness. Traditional calibration methods involve comparing the diameter and variation with a standard ring gauge using a length measuring instrument, followed by a second clamping with a roundness meter, and finally measuring roundness and straightness after centering and leveling. For experienced operators, this process takes approximately 30 minutes per piece. However, the device in this invention, through its self-centering fixture and collaborative measurement system, can simultaneously calibrate all parameters—diameter, diameter variation, roundness, and straightness—in a single clamping operation. Furthermore, the combination of visual recognition technology and an adaptive calibration module reduces the programming time for measurement parameters, resulting in an overall measurement time of approximately 3 minutes per piece, significantly improving measurement efficiency.

[0096] (4) The measurement accuracy is accurate and reliable.

[0097] The self-centering clamp of the device in this embodiment of the invention can clamp and position smooth ring gauges of different specifications with a positioning accuracy of <0.3mm, effectively avoiding interference of the probe path, which is especially important for the measurement of small smooth ring gauges;

[0098] The measurement process is unmanned, which can effectively reduce the impact of temperature fluctuations and air disturbances on the measurement results. The configured multi-channel temperature sensor can monitor the temperature changes of the three axes of the coordinate measuring machine and the smooth ring gauge in real time, and correct the measurement results through formula (1), which significantly improves the measurement accuracy of the large-size smooth ring gauge.

[0099] The in-situ calibration method effectively compensates for the errors in probe diameter and roundness, greatly improving the measurement accuracy. As shown in Table 1, the differences between the measured diameter and roundness values ​​and the reference values ​​are all ≤0.2μm, verifying the accuracy and feasibility of the in-situ calibration method.

[0100] The measurement results of this device were verified by using a second-class standard ring gauge (see Table 6). En≤0.5, indicating that the measurement results are accurate and reliable.

[0101] (5) Improve the level of automation and intelligence

[0102] The automated calibration module, visual recognition, and coordinate measurement technologies developed based on the Quindos 7 open-source system collectively achieve automation and intelligence in the calibration process. The visual recognition system automatically acquires the geometric feature information of the ring gauge, and the adaptive calibration module adjusts the measurement scheme in real time based on the input geometric feature information, driving the coordinate measuring machine to execute the measurement task. The entire calibration process requires no manual intervention. The collaborative work of these modules transforms the calibration process from traditional manual operation to automation and intelligence, reducing the impact of human factors on the calibration results and improving the stability and reliability of the measurement results.

[0103] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. An automatic calibration device for a smooth ring gauge, characterized in that, It includes a clamping and positioning unit, a vision recognition unit, a measurement unit, and a computer control system. The measurement unit includes a metrological coordinate measuring machine, an automated calibration module, and a temperature acquisition unit. The visual recognition unit includes a line laser vision sensor and an image processing module. The computer control system is connected to the metrological coordinate measuring machine, the automated calibration module, the temperature acquisition unit, the line laser vision sensor, and the image processing module to realize data transmission and collaboration between the metrological coordinate measuring machine, the automated calibration module, the temperature acquisition unit, the line laser vision sensor, and the image processing module. The clamping and positioning unit is installed on the movable worktable of the metrology coordinate measuring machine for clamping and positioning the smooth surface ring gauge to be measured. The line laser vision sensor is installed above the movable worktable of the metrology coordinate measuring machine and works in conjunction with the movable worktable to scan the 3D contour of the smooth surface ring gauge using laser triangulation to obtain point cloud data. The image processing module uses a deep learning-based image recognition algorithm to identify and analyze the point cloud data of the 3D contour of the smooth surface ring gauge to obtain the geometric feature information of the smooth surface ring gauge, which is transmitted to the automatic calibration module in real time. The automatic calibration module adjusts the measurement scheme in real time according to the received geometric feature information of the smooth surface ring gauge. The metrology coordinate measuring machine performs full parameter measurement of the smooth surface ring gauge according to the adjusted measurement scheme. The temperature acquisition unit includes multiple temperature sensors installed on the metrological coordinate measuring machine and the smooth ring gauge under test. These sensors are used to monitor and acquire the temperature changes of the environment during the measurement process in real time and transmit the data to the automated calibration module. The automated calibration module corrects the measurement results of the smooth ring gauge based on the received environmental temperature changes.

2. The apparatus as claimed in claim 1, characterized in that, It also includes a paperless certificate entry system, which is connected to the computer control system to receive measurement data from the metrology coordinate measuring machine in real time and output a smooth ring gauge calibration report.

3. The apparatus as described in claim 1 or 2, characterized in that, The clamping and positioning unit is a self-centering fixture, which can clamp and position smooth ring gauges of different specifications with a positioning accuracy of <0.3mm.

4. The apparatus as described in claim 1 or 2, characterized in that, The measurement scheme includes probe selection, path planning, and measurement point distribution. The full parameters of the smooth ring gauge include diameter, diameter variation, roundness, and straightness measurement.

5. An automatic calibration method for a smooth ring gauge, characterized in that, Automatic calibration of smooth ring gauges using the apparatus according to any one of claims 1-4 includes: Place the smooth ring gauge on the clamping and positioning unit to complete the clamping, and align the center of the smooth ring gauge with the center of the measurement coordinate system; The movable worktable of the metrology coordinate measuring machine moves and works with the line laser vision sensor to complete the 3D contour scanning of the smooth surface ring gauge. The image processing module extracts the geometric feature information and transmits it to the automatic calibration module. The automated calibration module adaptively adjusts the measurement scheme of the metrology coordinate measuring machine based on the received geometric feature information, and the metrology coordinate measuring machine performs full parameter measurement of the smooth ring gauge according to the adjusted measurement scheme. The computer control system transmits the data measured by the metrological coordinate measuring machine to the paperless certificate entry system in real time. The paperless certificate entry system then outputs a calibration report for the smooth ring gauge, thus completing the entire calibration process for the smooth ring gauge from measurement to report output.

6. The method as described in claim 5, characterized in that, Also includes: Using a high-precision step gauge, and through the cooperation of the computer control system and the measurement unit, the geometric parameter errors of the metrology coordinate measuring machine are calibrated in seven directions in space, and the calibrated errors are compensated to the metrology coordinate measuring machine.

7. The method as described in claim 5 or 6, characterized in that, Also includes: The in-situ calibration method was adopted, and a probe with a roundness error of <0.2μm was selected as the reference probe. A high-precision length measuring machine and a roundness meter were used to measure the diameter and roundness error of the probe of the metrology coordinate measuring machine, and the measured diameter and roundness error were compensated to the metrology coordinate measuring machine.

8. The method as described in claim 5 or 6, characterized in that, Also includes: High-precision temperature sensors are arranged on the grating ruler and the ring gauge of the optical surface to be measured in the metrological coordinate measuring machine to monitor the temperature data of each temperature sensor in real time and transmit the temperature data to the automatic calibration module. A multivariate regression analysis algorithm is used to establish a relationship model between temperature change and measurement error. During the measurement process, the real-time monitored temperature data is substituted into the relationship model to calculate the measurement error caused by temperature. The measurement results are then corrected through an automated calibration module.

9. The method as described in claim 8, characterized in that, The measurement results should be corrected according to the following formula: In the formula: —Correction value for measurement results; —The nominal diameter of the smooth ring gauge; —Temperature of the grating ruler of the coordinate measuring machine; —Coefficient of linear expansion of the grating ruler of a coordinate measuring machine; —Temperature of the smooth ring gauge; —The coefficient of linear expansion of a smooth ring gauge.

10. The automatic calibration method for smooth ring gauges as described in claim 5 or 6, characterized in that, Also includes: The smooth ring gauge was measured under different combinations of detection speed and approximation distance. Measurement performance data were collected, and the intrinsic relationship between detection speed, approximation distance and measurement performance indicators was analyzed. The optimal detection speed and approximation distance were derived as the optimization parameters of the probe of the metrology coordinate measuring machine.

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