Error separation and compensation method for high-precision surface shape measurement system

Abstract

The invention relates to an error separation and compensation method for a high-precision surface shape measurement system. The system comprises a high-precision measurement instrument, a shafting motion link module, a high-precision measurement link module and an upper computer processing module. The invention innovatively provides a two-step error separation compensation method based on a double-link architecture, and constructs a novel error processing system in which a kinematic link and a metering link cooperatively work by analyzing a motion structure and a measurement strategy of a high-precision measurement instrument. Establishing a kinematic link space error model by adopting an off-line measurement calibration technology of a kinematic link error, and realizing on-line compensation of a shafting positioning error; and a metering link error on-line measurement and off-line separation technology is used, and a metering link space error transmission model is used to complete off-line post-processing compensation of a measurement result error. According to the invention, high-precision measurement and separation of various error sources are realized, the overall precision is improved by more than 85%, and the technical bottleneck that the meter-scale range and the nano-scale precision are difficult to consider in the traditional measurement technology is successfully broken through.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano measurement technology, and particularly to a method for separating and compensating system errors of a high-precision surface shape measurement system. Background Art

[0002] With the rapid development of society, the development of high-precision measuring machines has brought significant impacts on aspects such as the production mode, industrial structure, talent cultivation mechanism, and management mode in the field of mechanical manufacturing. Its precision level is not only an important symbol to measure a country's industrial automation level but also an important measure for the development of the national economy.

[0003] The precision of high-precision measuring instruments is affected by many error sources. These error sources cause changes in the geometric shapes of machine components in the machine structure loop, resulting in the actual position of the probe relative to the workpiece being different from its nominal position, thereby causing measurement errors. The prior art has insufficient handling of the coupling effects of multiple error sources, especially limited compensation ability for dynamic errors. The error sources of high-precision measuring instruments mainly include the motion error sources of the machine table axis system of the measuring instrument, the metrology system error sources, the probe error, the environmental error, the force deformation error, etc. Among them, the kinematic error of the axis system is an important source, which is caused by the imperfect geometric shapes, alignment, and dimensions of machine components and their assembly errors in the machine structure loop. Traditional error separation methods are difficult to accurately identify and compensate for these complex errors.

[0004] The direct errors of complex surface shape measuring instruments mainly come from the internal mechanism components of the measuring instrument, which is the most important link affecting the precision of the measuring instrument. It is caused by factors such as insufficient precision of measuring instrument components, mechanical wear, improper assembly, etc., resulting in the overall geometric error of the axis system of the motion mechanism of the measuring instrument, various errors of the high-precision metrology system, the internal force deformation error of the measuring instrument, and the measuring error of the probe mechanism. The existing compensation technologies have insufficient compensation precision for these direct errors and are difficult to achieve real-time dynamic compensation.

[0005] Currently, the main methods for separating and calibrating the geometric errors of measuring machines are divided into "direct" and "indirect" methods. These traditional methods have obvious limitations: although "direct" measurement can measure the geometric errors of a single machine axis, its precision is limited; "indirect" measurement requires complex multi-axis motion trajectories, with complex operations and low efficiency. Both methods are difficult to meet the requirements of modern high-precision measurement. The existing measuring machine error compensation technologies mainly include three types: software compensation, hardware compensation, and post-processing compensation. These technologies each have obvious deficiencies: software compensation has limited precision (up to only the micron level); although hardware compensation has high precision (nanometer level), it has high costs and a small measurement range; post-processing compensation cannot achieve real-time compensation. None of the three methods can simultaneously meet the requirements of high precision, large range, and real-time performance.

[0006] Therefore, there is an urgent need to implement a method for separating and compensating errors in a high-precision surface shape measurement system. Summary of the Invention

[0007] The object of the present invention is to provide a method for separating and compensating errors in a high-precision surface shape measurement system. This method can solve the deficiencies in the prior art, measure various errors of the measuring machine, and compensate for these errors in the measurement results to obtain a high measurement accuracy and a high error compensation rate, and have good repeatability and good stability in measurement performance.

[0008] To achieve the above object, the present invention adopts the following technical solutions: A method for separating and compensating errors in a high-precision surface shape measurement system, the high-precision surface shape measurement system includes: a high-precision measuring instrument, an axis system motion link module, a high-precision metrology link module, and a host computer processing module.

[0009] The error separation and compensation method includes: The axis system motion link module obtains the motion error data of the high-precision measuring instrument. The host computer processing module establishes a motion link space error model based on the motion error data and compensates for the axis positioning error of the high-precision measuring instrument. The high-precision metrology link module obtains the metrology error data of the high-precision measuring instrument. The host computer processing module establishes a metrology link space error transfer model based on the metrology error data and compensates for the metrology error of the high-precision measuring instrument.

[0010] As a further improvement of the above technical solution, the axis system motion link module includes: a laser interferometer, an autocollimator, a high-precision optical mirror group, a sensing probe, a standard ball, and a positioning bracket. The laser interferometer, the autocollimator, and the sensing probe are fixed on the positioning bracket; the high-precision optical mirror group and the standard ball are installed on the high-precision measuring instrument, and the high-precision optical mirror group is respectively combined with the laser interferometer and the autocollimator to form an optical path; the light rays emitted by the laser interferometer and the autocollimator respectively pass through the high-precision optical mirror group and move forward parallel or perpendicular, and finally return to the laser interferometer and the autocollimator, thereby forming an interference optical path and a reflection optical path to realize the off-line measurement of the motion error data of the high-precision measuring instrument.

[0011] As a further improvement of the above technical solution, the high-precision surface shape measurement system further includes a signal transmission module; the output ends of the laser interferometer, the autocollimator, and the sensing probe are connected to the signal transmission module. The signal transmission module plays a key role in connecting each module and transmitting data in the high-precision surface shape measurement system, ensuring the information flow and collaborative work of the entire measurement system, and is an important link for realizing error separation and compensation. The signal transmission module is implemented using existing technologies.

[0012] As a further improvement of the above technical solution, the high-precision measurement link module includes: a standard part, a high-precision displacement sensor, a data acquisition card, and a positioning mechanism. The standard part is cylindrical and is fixedly placed on the moving shaft of the high-precision measuring instrument; the high-precision displacement sensor is fixed on the positioning mechanism; the positioning mechanism is fixed on the outer periphery of the moving shaft of the high-precision measuring instrument; the high-precision displacement sensor is connected to the data acquisition card, and the high-precision displacement sensor is used to measure the radial data and axial data of the standard part online and transmit the measurement data to the data acquisition card; the data acquisition card performs signal conversion on the measurement data of the high-precision displacement sensor and transmits the converted data to the computer through the signal transmission module.

[0013] As a further improvement of the above technical solution, the upper computer processing module includes: a computer, a data acquisition unit, an environmental compensation unit, and an error separation and compensation unit; the outputs of the shaft system motion link module and the high-precision measurement link module are respectively transmitted to the data acquisition unit on the computer through the signal transmission module; the output end of the environmental compensation unit is connected to the computer; the computer acquires the measurement data of the shaft system motion link module and the high-precision measurement link module through the data acquisition unit; the data acquisition unit outputs the measurement data and transmits it to the error separation and compensation unit for processing, and according to the processing structure of the error separation and compensation unit, generates a compensation feedback instruction and feeds back the compensation instruction to the drive system of the high-precision measuring instrument, and according to the compensation feedback instruction, performs offline measurement and online compensation of the shaft system motion link module and online measurement and offline compensation of the high-precision measurement link module respectively.

[0014] As a further improvement of the above technical solution, the "shaft system motion link module obtains the motion error data of the high-precision measuring instrument, and the upper computer processing module compensates the shaft system positioning error of the high-precision measuring instrument according to the motion error data; the high-precision measurement link module obtains the measurement error data of the high-precision measuring instrument, and the upper computer processing module compensates the measurement error of the high-precision measuring instrument according to the measurement error data", specifically includes the following steps: S1. Install the high-precision optical lens group on the moving shaft of the high-precision measuring instrument, and at the same time fix the laser interferometer on the metrology reference position of the high-precision measuring instrument through the positioning bracket, connect the computer with the laser interferometer and the environmental compensation unit, after preheating each device, synchronously initialize the measurement environment of the shaft system motion link module and the high-precision measurement link module through the data acquisition unit, and adjust the positioning bracket, the laser interferometer and the high-precision optical lens group to make the laser emitted by the laser interferometer return to its receiving end after passing through the interference optical path.

[0015] S2. Control the moving axis of the high-precision measuring instrument to reciprocate along a preset route. At the same time, the temperature and humidity are corrected in real time through the environmental compensation unit. Use a laser interferometer and a high-precision optical mirror group to offline collect the linear error, straightness, angular deviation of the moving axis of the high-precision measuring instrument, and the degrees of freedom of the moving axis, and transmit the measured data to the computer through the data acquisition unit.

[0016] S3. Use an autocollimator and a high-precision optical mirror group to offline measure the roll angle of the moving axis of the high-precision measuring instrument, and transmit the measured data to the computer through the data acquisition unit.

[0017] S4. The moving axis of the high-precision measuring instrument rotates, driving the standard ball to rotate. Use a sensing probe to measure the apex data during the rotation of the standard ball, and transmit the measured data to the computer through the data acquisition unit.

[0018] S5. Input the offline measurement data of the motion link collected in steps S2 to S4 into the error separation and compensation unit. The error separation and compensation unit calculates the positioning error compensation values of the moving axis system of the high-precision measuring instrument in each direction.

[0019] S6. Fix the standard part on the moving axis of the high-precision measuring instrument and make their axes coincide. Fix the positioning mechanism at intervals on the outer periphery of the moving axis of the high-precision measuring instrument in a manner parallel or perpendicular to the axis of the moving axis, and fix multiple high-precision displacement sensors on the positioning mechanism. Use the multiple high-precision displacement sensors to measure the radial data and axial data of the standard part, and transmit the measured data to the computer through the data acquisition card.

[0020] S7. Through the computer, control the moving axis of the high-precision measuring instrument to drive the standard part to rotate at a constant speed. At the same time, the high-precision displacement sensors online measure the radial error data and axial error data of the standard part, and convert the measurement data of the high-precision displacement sensors into signals recognizable by the data acquisition unit through the data acquisition card. The data acquisition unit transmits the converted data to the error separation and compensation unit. The error separation and compensation unit decouples and separates the data through the three-point method and the four-point method on the surface to obtain the metrology error data of the moving axis of the high-precision measuring instrument.

[0021] S8. Offline compensate the metrology error of the high-precision measuring instrument according to the metrology error data of the moving axis of the high-precision measuring instrument and the amount of motion after real-time compensation of the moving axis.

[0022] As a further improvement of the above technical solution, in step S5, the "error separation and compensation unit calculates the positioning error compensation values of the moving axis system of the high-precision measuring instrument in each direction" specifically includes the following steps: S51. Based on the relationship between the spatial position of the probe tip of the high-precision measuring instrument and the multi-axis mechanical coordinates, the screw theory is used to establish a multi-axis kinematic model of the high-precision measuring instrument stage.

[0023] Obtain the spatial error model of the motion structure of the axis system stage of the measuring instrument.

[0024] S52. Using the multi-axis kinematic model, obtain the forward spatial error of the motion axis system of the high-precision measuring instrument, and use the screw theory and inverse kinematic algorithm to establish a spatial error model for the motion structure of the high-precision measuring instrument.

[0025] S53. Control the motion of the motion axis of the high-precision measuring instrument through the computer, and use a laser interferometer to measure the motion positioning error during the motion of the motion axis in real time.

[0026] S54. Based on the motion positioning error, use the spatial error model to compensate the high-precision measuring instrument, and determine the motion amounts of each motion axis of the high-precision measuring instrument after error compensation.

[0027] As a further improvement of the above technical solution, in step S8, the offline compensation for the measurement error of the high-precision measuring instrument (1) according to the measurement error data of the motion axis of the high-precision measuring instrument and the motion amounts after real-time compensation of the motion axis includes: Based on the measurement error data of the motion axis of the high-precision measuring instrument and the motion amounts after real-time compensation of the motion axis, establish a spatial error transfer model for the measurement link, and use the spatial error transfer model for the measurement link to perform offline compensation for the measurement error of the high-precision measuring instrument.

[0028] Compared with the prior art, the advantages of the present invention are: (1) The present invention adopts a method of offline separation and online compensation of errors based on the motion structure of the high-precision measuring instrument. This method can significantly reduce the positioning errors of each motion axis system, the Abbe error of the probe axis, and the probe alignment error, avoid the large measurement uncertainty brought by a large range, and provide a basis for reliably realizing the separation and compensation of the measurement structure error. The present invention has high sensitivity and good repeatability, can realize high-sensitivity measurement in a large range, and is easy to operate.

[0029] (2) The present invention adopts a method of online separation and offline compensation of errors based on the measurement structure of the high-precision measuring instrument. This method realizes the offline error separation and compensation processing by real-time monitoring and decoupling and identifying the fusion signal of the measured workpiece topography and the main geometric errors, thereby can further improve the accuracy of error separation and compensation and ensure the nano-level measurement accuracy of the system.

[0030] (3) As can be seen from the above, the present invention adopts a two-step error separation and compensation method based on a dual-link structure. By constructing a motion link of the axis system and a high-precision measurement link, a spatial error model of the motion link and a spatial error transfer model of the measurement link are established, thereby completing the comprehensive error compensation research of error compensation inverse kinematics. This helps to significantly reduce the influence of the original error sources of the system on the measurement accuracy, and provides accuracy guarantee and theoretical technical basis for the development of a large-aperture complex surface profiler with nanometer-level measurement uncertainty. Description of the Drawings

[0031] Figure 1 is the principle block diagram of the error separation and compensation method for the high-precision surface profiler system in the present invention; Figure 2 is the method flow chart of the error separation and compensation method for the high-precision surface profiler system in the present invention.

[0032] Figure 3 is the schematic diagram of the geometric error measurement and calibration of the translation axis for the error separation and compensation method of the high-precision surface profiler system in the present invention.

[0033] Wherein: 1. High-precision profiler, 2. Laser interferometer, 3. Autocollimator, 4. High-precision optical lens group, 5. Sensing probe, 6. Standard sphere, 7. Positioning bracket, 8. Standard part, 9. High-precision displacement sensor, Detailed Embodiment

[0034] The present invention will be further described below with reference to the drawings: The present invention discloses a method for error separation and compensation of a high-precision surface profiler system, which is used for two-step error separation and compensation of the dual-link structure of a large-range high-precision surface profiler.

[0035] As Figure 1 shown, the method for error separation and compensation of the high-precision surface profiler system includes: a high-precision profiler 1, an axis system motion link module, a high-precision measurement link module, a signal transmission module, and a host computer processing module. The innovation and key point of the present invention lie in constructing two links: an axis system motion link and a high-precision measurement link, and respectively performing motion error separation and compensation and measurement error separation and compensation through the two-link structures.

[0036] As Figure 2 shown, the error separation and compensation method includes: The axis system motion link module obtains the motion error data of the high-precision profiler, and the host computer processing module compensates the axis positioning error of the high-precision profiler according to the motion error data. The high-precision metrology link module obtains the metrology error data of the high-precision measuring instrument, and the host computer processing module compensates for the metrology error of the high-precision measuring instrument according to the metrology error data.

[0037] As a further improvement of the above technical solution, the shafting motion link module includes: a laser interferometer 2, an autocollimator 3, a high-precision optical lens group 4, a sensing probe 5, a standard ball 6, and a positioning bracket 7. The laser interferometer 2, the autocollimator 3, and the sensing probe 5 are fixed on the positioning bracket 7 for positioning; the high-precision optical lens group 4 and the standard ball 6 are installed on the high-precision measuring instrument 1 to complete the measurement together with the laser interferometer 2, the autocollimator 3, and the sensing probe 5; the output ends of the laser interferometer 2, the autocollimator 3, and the sensing probe 5 are connected to the signal transmission module to realize the transmission of measurement data. The high-precision optical lens group 4 is combined with the laser interferometer 2 and the autocollimator 3 respectively; the light rays emitted by the laser interferometer 2 and the autocollimator 3 pass through the high-precision optical lens group 4 parallel or perpendicular respectively and can return to the laser interferometer 2 and the autocollimator 3 to form an interference optical path and a reflection optical path.

[0038] In the shafting motion link module, the laser interferometer 2 is used to measure the linear error, straightness, angular deviation, and degrees of freedom of the moving axis of the high-precision measuring instrument 1, etc. The working principle of the laser interferometer 2 is to emit laser light, which forms an interference optical path after passing through the high-precision optical lens group 4, and the displacement information of the moving axis is obtained by detecting the phase change of the interference beam, thereby obtaining various motion error data. The autocollimator 3 is based on the principle of optical autocollimation imaging and is used to measure the roll angle of the moving axis of the high-precision measuring instrument 1. The light ray emitted by the autocollimator 3 is reflected by the reflector in the high-precision optical lens group 4 and returns along the original optical path. When there is a roll angle on the moving axis, the reflected light ray will deviate from the original optical path, and the change of the roll angle is calculated by measuring this deviation. The high-precision optical lens group 4 is used in cooperation with the laser interferometer 2 and the autocollimator 3 to change the light propagation path, so that the light rays emitted by the laser interferometer 2 and the autocollimator 3 pass through the high-precision optical lens group 4 parallel or perpendicular respectively and form an interference optical path and a reflection optical path to realize the measurement of various errors of the moving axis. Different high-precision optical lens groups need to be replaced for different measurement requirements to meet the measurement requirements of different errors. The sensing probe 5 is used to detect the vertex data during the rotation of the standard ball 6 driven by the rotation of the moving axis of the high-precision measuring instrument 1. Through the analysis and processing of these data, the geometric error items of the high-precision measuring instrument can be obtained. The standard ball 6 is installed on the high-precision measuring instrument 1 and rotates with the moving axis. The vertex data during its rotation is measured by the sensing probe to provide data support for calculating the geometric error. The positioning bracket 7 is used to fix the laser interferometer 2, the autocollimator 3, and the sensing probe 5 to ensure the relative positions of these devices are stable during the measurement process, thereby ensuring the accuracy of the measurement data.

[0039] In this embodiment, the laser of the laser interferometer 2 outputs dual-longitudinal-mode laser containing two orthogonal modes. The light intensities of these two modes are measured by a photosensitive diode, and the frequency is stabilized by controlling the length of the laser tube with a heater. As Figure 3 shown, in the linear and angular error measurements of the high-precision measuring instrument 1, the laser beam emitted by the laser interferometer 2 sequentially passes through the interference mirror in the high-precision optical mirror group 4 and the reflecting mirror that moves with the moving mechanism of the high-precision measuring instrument 1 to form an interference optical path and then returns to the receiving end. By calculating the phase change of the interference signal, the linear positioning error and the pitch angle and yaw angle errors of the moving axis are obtained in real time. In the straightness measurement, the laser emitted by the laser interferometer 2 passes through the straightness interference mirror in the high-precision optical mirror group 4 that moves with the moving mechanism of the high-precision measuring instrument 1 and then enters the straightness reflecting mirror in the high-precision optical mirror group 4. After the laser passes through the interference mirror to superimpose and interfere with the light beams with each other, it returns to the laser receiving end of the laser interferometer 2. By analyzing the returned light intensity signal, the straightness errors in the vertical and horizontal directions can be decoupled. Changing the length of the measurement optical path will cause the relative phase of the interference light beams to change, and the resulting cycle of constructive interference and destructive interference will cause the intensity of the superimposed light beam to change periodically between bright and dark. Based on this, the errors of different degrees of freedom of the translation axis can be measured. For the measurement of the errors of different degrees of freedom of the translation axis of different motion structures, different combinations and placement methods of high-precision optical mirror groups need to be used. The common compositions and usage methods of high-precision optical mirror groups are as Figure 3 shown.

[0040] In this embodiment, during the measurement process, the laser interferometer 2 and the autocollimator 3 are not used simultaneously. When obtaining the linear error, straightness, angular deviation, and degrees of freedom of the moving axis, the laser interferometer 2 is mainly used; while when measuring the roll angle of the moving axis, the autocollimator 3 is replaced for measurement. They play their respective roles according to the measurement requirements in different measurement steps and jointly complete the off-line measurement of various errors of the moving axis. The autocollimator 3 is based on the principle of optical autocollimation imaging. As Figure 3 shown, the collimated light beam emitted by the autocollimator 3 forms an autocollimation optical path after being affected by two specific optical elements in the high-precision optical mirror group 4: first, a 90° right-angle turn is achieved through a 45° reflecting mirror fixed on the high-precision measuring instrument 1, and then it returns along the incident path to the receiving end of the autocollimator through a fixed plane mirror. When the system is running, due to the existence of the roll angle, the light beam emitted by the reflecting mirror will deviate from the original optical path, and the convergence point of the autocollimator 3 will also deviate from the original position accordingly. By measuring this deviation, the change in the roll angle of the high-precision measuring instrument can be calculated.

[0041] The sensing probe 5 and the standard ball 6 are both mounted on the positioning bracket 7. The standard ball 6 and the sensing probe 5 are respectively mounted at the center position of the rotary axis workbench and on the rotary axis workbench. When the moving axis rotates to different angles, the standard ball 6 will rotate together with the moving axis. The sensing probe 5 is used to measure the motion trajectory profile of the measured points on the standard ball 6. For the error components of the total geometric error measured in the X, Y, and Z directions, the existing EMD method is used to identify and separate the mixed signals of PIGEs (position-independent geometric errors) and PDGEs (position-dependent geometric errors), so as to obtain the independent signals of PIGEs and PDGEs, and then the algorithm separation of each geometric error term is carried out. Combining with the geometric error coordinate transformation matrix of the rotary axis, considering the coordinate measurement results and the nominal motion amount, the error components of the geometric error in the X, Y, and Z axis directions and each PIGEs and PDGEs error term are obtained.

[0042] As a further improvement of the above technical solution, the high-precision metrology link module includes: the moving axis of the high-precision measuring instrument 1, a cylindrical standard part 8, a high-precision displacement sensor 9, a data acquisition card 10, and a positioning mechanism 11. The standard part 8 is fixedly placed on the moving axis of the high-precision measuring instrument 1 of the high-precision measuring instrument and ensures that the axes coincide. The high-precision displacement sensor 9 is fixed on the positioning mechanism 11; the positioning mechanism 11 is arranged around the moving axis of the high-precision measuring instrument and is fixed on the high-precision measuring instrument 1. The number of the high-precision displacement sensors 9 is 7. Among them, 3 high-precision displacement sensors 9 surround the standard part 8 and are fixed on the positioning mechanism 11 at the same horizontal plane at certain intervals respectively, and the other 4 high-precision displacement sensors 9 are located above the cylindrical standard part 8 and are fixed on the positioning mechanism 11 at the same horizontal plane at certain intervals respectively. The high-precision displacement sensor 9 is connected to the data acquisition card 10, and the output end of the data acquisition card 10 is connected to the signal transmission module.

[0043] In the high-precision measurement link module: The moving axis of the high-precision measuring instrument serves as the installation carrier of the cylindrical standard part, providing the motion basis for the measurement process. During measurement, the moving axis drives the standard part 8 to perform a uniform rotational motion, enabling the high-precision displacement sensor 9 to measure the error data of the standard part 8 during rotation. These data indirectly reflect the metrological accuracy of the moving axis. The standard part 8 is the reference object for measurement, fixed on the moving axis of the high-precision measuring instrument with their axes coinciding. The high-precision displacement sensor 9 obtains the position deviation information of the moving axis during rotation by measuring the radial and axial data of the cylindrical standard part, and then analyzes the metrological error of the moving axis. Its accuracy and stability directly affect the accuracy of the measurement results. The high-precision displacement sensor 9 is also used to measure the radial error data and axial error data of the standard part 8 in real time. Multiple high-precision displacement sensors 9 are fixed on the positioning mechanism according to a specific layout, measuring the standard part 8 from different positions and angles to obtain comprehensive error data, providing the original data support for subsequent error analysis. The data acquisition card 10 converts the analog signal measured by the high-precision displacement sensor 9 into a digital signal recognizable by the computer data acquisition unit. The data acquisition card 10 plays a role as a bridge for signal conversion and transmission between the sensor and the computer, ensuring that the measurement data can be accurately transmitted to the upper computer processing module for subsequent processing. The positioning mechanism 11 is used to fix the high-precision displacement sensor 9 so that it surrounds the standard part 8 and the moving axis. Through a reasonable fixing method, it is ensured that the position of the high-precision displacement sensor 9 is stable during the measurement process and can accurately measure the radial and axial data of the standard part 8.

[0044] As a further improvement of the above technical solution, the upper computer processing module includes: a computer 12, a data acquisition unit 13, an environmental compensation unit 14, and an error separation and compensation unit 15. The output of the signal transmission module is transmitted to the data acquisition unit 13 on the computer 12. The output end of the environmental compensation unit 14 is connected to the computer 12; the computer 12 collects measurement data through the data acquisition unit 13; the measurement data is output by the data acquisition unit 13 and transmitted to the error separation and compensation unit 15 for processing.

[0045] In the upper computer processing module, the computer 12 serves as the core of the entire upper computer processing module, and uniformly controls and coordinates various parts of the system. It can control the movement axes of the high-precision measuring instrument to move along a preset route, and can also control the timing and frequency of data acquisition, etc. For example, during the measurement process of the axis system movement link module, the computer controls the movement axes of the high-precision measuring instrument to reciprocate along a preset route to complete the acquisition of corresponding error data. The computer is also used to receive the measurement data transmitted by the data acquisition unit, and perform preliminary processing and analysis. At the same time, it can also issue compensation instructions to the drive system of the high-precision measuring instrument according to the calculation results of the error separation and compensation unit, so as to compensate for the positioning error and metrological error of the measuring instrument axis system. The data acquisition unit 13 is used to collect the measurement data from the signal transmission module. These data include the measurement data of the laser interferometer, autocollimator, and sensing probe in the axis system movement link module, as well as the measurement data after conversion by the data acquisition card 10 of the high-precision displacement sensor 9 in the high-precision metrology link module. The data acquisition unit 13 accurately transmits the collected measurement data to the error separation and compensation unit 15, providing raw data support for error analysis and compensation. The environmental compensation unit 14 is used to monitor various factors in the measurement environment in real time, such as temperature and humidity. Because changes in the measurement environment may affect the measurement results. For example, temperature changes may cause the components of the measuring instrument to expand and contract thermally, thereby affecting the measurement accuracy. According to the monitored changes in environmental factors, the measurement data is corrected accordingly. By connecting to the computer, the correction parameters are transmitted to the computer, and the computer considers these correction factors when processing the measurement data, thereby reducing the influence of environmental factors on the measurement results and improving the measurement accuracy.

[0046] The error separation and compensation unit 15 is used to process the measurement data transmitted by the data acquisition unit, and decouple and separate different types of errors by using the three-point method and the surface four-point method in the existing technology. Based on the separated error data and the real-time compensated movement amount of the movement axis, calculate the specific value that needs to be compensated for the high-precision measuring instrument, and feedback the calculated compensation instructions to the drive system of the high-precision measuring instrument. The drive system compensates for the positioning error and metrological error of the measuring instrument axis system according to these instructions, thereby improving the measurement accuracy.

[0047] In order to achieve high-precision measurement of large-caliber complex surface shapes, the present invention proposes a method for error separation and compensation of a high-precision surface shape measurement system. This method improves the error separation and calibration accuracy of a high-precision measuring instrument through a two-step error separation and compensation method with a dual-link structure, achieving a higher compensation accuracy, and providing strong technical support for large-scale micro-nano measurement. On the basis of fully considering the motion structure and measurement strategy of high-precision measuring instruments in the prior art, the present invention proposes a two-step error separation and compensation method with a dual-link structure, realizing high-precision measurement and separation of various error sources affecting the measurement accuracy of high-precision surface shape measuring instruments. The dual-link structure refers to the axis system motion link module and the high-precision metrology link module. The two-step error separation and compensation method based on the dual-link structure includes an off-line measurement and calibration technology for motion link errors and an on-line measurement and off-line separation technology for metrology link errors. By establishing a motion link space error model and a metrology link space error transfer model, on-line compensation of the axis system positioning errors of the motion link and off-line post-processing compensation of the measurement result errors of the metrology link are completed. Through the comprehensive error two-step compensation technology combining the error compensations of the two links, the present invention can significantly reduce the influence of the original various error sources of the high-precision measuring instrument on the measurement accuracy, providing accuracy guarantee and theoretical technical basis for the development of large-range high-precision surface shape measuring instruments.

[0048] The present invention innovatively proposes a two-step error separation and compensation method based on a dual-link architecture. By deeply analyzing the motion structure and measurement strategy of the measuring machine, a new error processing system for the collaborative work of the motion link and the metrology link is constructed. This technical solution includes two core technologies: one is to adopt an off-line measurement and calibration technology for motion link errors, and realize on-line compensation of axis system positioning errors by establishing a motion link space error model; the other is to apply an on-line measurement and off-line separation technology for metrology link errors, and complete off-line post-processing compensation of measurement result errors based on the metrology link space error transfer model. This innovative dual-track parallel mechanism and two-step compensation strategy not only achieve high-precision measurement and separation of various error sources, but also improve the overall system accuracy by more than 85%, successfully breaking through the technical bottleneck that it is difficult to balance the meter-level range and nanometer-level accuracy in traditional measurement technologies. This technology provides a solid theoretical technical basis and accuracy guarantee for the development of large-range high-precision surface shape measuring instruments, and is a major technical breakthrough in the field of high-precision measurement of complex surface shapes.

[0049] As Figure 2 shown, the method for error separation and compensation of the high-precision surface shape measurement system specifically includes the following steps: (1) Install the high-precision optical lens group 4 on the moving axis of the high-precision measuring instrument 1. At the same time, fix the laser interferometer 2 at the metrology reference position through the positioning bracket 7. Connect the computer 12 with the laser interferometer 2 and the environmental compensation unit 14. After preheating the equipment, synchronously initialize the measurement environment of the motion link and the metrology link through the data acquisition unit 13. Adjust the positioning bracket 7, the positioning device of the laser interferometer 2 itself, and the high-precision optical lens group 4 installed on the high-precision measuring instrument 1, so that the laser emitted by the laser interferometer can return to the receiving end completely after passing through the interference optical path to ensure normal use.

[0050] (2) Control the moving axis of the high-precision measuring instrument 1 to perform a preset reciprocating motion, and replace the high-precision optical lens group 4 to enable the laser interferometer 2 to collect the linear error, straightness, and angular deviation of the moving axis offline. At the same time, the environmental compensation unit 14 of the metrology link corrects interference factors such as temperature and humidity in real time, and transmits the measured degrees of freedom of the moving axis to the computer 12 through the corresponding data acquisition unit 13.

[0051] (3) Replace the autocollimator 3 and the corresponding high-precision optical lens group 4, and measure the roll angle of the moving axis of the high-precision measuring instrument 1 offline, and transmit the data to the computer 12 through the data acquisition unit 13.

[0052] (4) Install the sensing probe 5 and the standard ball 6 on the high-precision measuring instrument 1 through the positioning bracket 7, connect the computer 12 with the sensing probe 5, and turn on the data acquisition unit 13 on the computer 12; detect the vertex data during the rotation of the standard ball 6 driven by the rotation of the moving axis through the sensing probe 5, and transmit the measurement data to the computer 12.

[0053] (5) Import the offline measurement data of the motion link in steps (2) to (4) collected by the data acquisition unit 13 on the computer 12 into the error separation and compensation unit 15 for processing.

[0054] (6) Based on the relationship between the spatial position of the tip of the probe of the high-precision measuring instrument 1 and the multi-axis mechanical coordinates, establish a five-axis kinematic model of the measuring instrument table. Use screw theory to establish a multi-axis kinematic model and a spatial error model, and obtain the spatial error model of the axis system machine table motion structure of the high-precision measuring instrument 1.

[0055] (7) Based on the screw theory, the forward spatial error mapping modeling of the motion axis system of the high-precision measuring instrument 1 is completed. The screw theory and inverse kinematics algorithm are further used to establish a spatial error compensation algorithm for the motion structure of the high-precision measuring instrument 1. The motion of the motion axis of the high-precision measuring instrument 1 is controlled by the computer 12, and the motion positioning error of the motion axis during the motion correction process is measured in real time by the laser interferometer 2 to improve the alignment and positioning accuracy between the probe and the measured surface. The motion amount of each motion axis after error compensation is obtained by inverse kinematics. The iterative cycle is repeated until the tolerance requirements are met, and the motion amount of each motion axis after compensation that meets the tolerance requirements is derived.

[0056] (8) The cylindrical standard part 8 is fixedly placed on the moving axis of the high-precision measuring instrument 1 so that the axes of the two coincide, and the positioning mechanism 11 is fixed around the moving axis of the high-precision measuring instrument 1 at certain intervals in a manner parallel to or perpendicular to the axis of the moving axis, and a plurality of high-precision displacement sensors 9 are fixed on the positioning mechanism 11, wherein three high-precision displacement sensors can measure the radial data of the cylindrical standard part 8 and four high-precision displacement sensors can measure the axial data of the cylindrical standard part 8 on the same horizontal plane, and at the same time, the high-precision displacement sensors 9 are connected to the data acquisition card 10, and the data acquisition card 10 is connected to the computer 12.

[0057] (9) Connect the computer 12 to the moving axis of the high-precision measuring instrument, and control the moving axis of the high-precision measuring instrument to rotate at a uniform speed together with the cylindrical standard part 8 through the computer 12. At the same time, the high-precision displacement sensor 9 measures the radial error data and axial error data of the cylindrical standard part 8 online, and converts the measurement signal of the high-precision displacement sensor 9 into a signal that can be recognized by the data acquisition unit 13 of the computer 12 through the data acquisition card 10 for reading. The error separation and compensation unit 15 decouples and separates the various error data of the moving axis through the three-point method and the surface four-point method.

[0058] (10) The motion amount after real-time compensation of the motion axis derived from the error separation and compensation unit step (7) and the motion axis error obtained by real-time decoupling and separation in step (9) are used to establish a spatial error transmission model of the metrology link, and on this basis, the measurement results are compensated offline.

[0059] With the rapid development of the mechanical manufacturing field, higher requirements will be put forward for the accuracy of measurement systems. For example, the measurement range reaches the meter level, and the measurement accuracy even reaches the nanometer level, so that the error compensation rate reaches more than 80%. Aiming at the deficiencies in the existing technologies, the present invention develops a novel multi-stage error separation algorithm, breaks through the limitations of traditional direct / indirect measurement methods, and realizes the accurate identification of full-scale errors from the macroscopic to the nanometer level. By constructing a dual-link real-time compensation architecture, the flexibility of software compensation is combined with the high-precision advantage of hardware compensation; through the axis system motion link module, motion error data is collected, and a multi-axis kinematic model and a spatial error model are established based on screw theory to realize the dynamic compensation of the axis system positioning error of the high-precision measuring instrument; through the metrology link module, error data is obtained online, the metrology error is decoupled and separated by combining the three-point method and the surface four-point method, and a spatial error transfer model is established to complete the offline compensation of the metrology error. In the various error separation calibration and error compensation technologies of the high-precision measuring instrument, the present invention fully considers the motion structure and measurement strategy of the high-precision measuring instrument, and designs a two-step error separation compensation method with a dual-link structure. Compared with the traditional error compensation method of the measuring machine, the two-step error separation compensation method with a dual-link structure shows significant advantages. This method not only solves the problems of insufficient accuracy and poor real-time performance in the existing technologies, but also can realize large-range measurement under nanometer-level accuracy. Through the innovative technical solution, the present invention effectively solves the key problems faced by the existing measurement technologies and provides a reliable technical guarantee for future high-precision measurement requirements.

[0060] The above-described embodiments are only used to describe the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for error separation and compensation of a high-precision surface shape measurement system, characterized in that The high-precision surface shape measurement system includes: a high-precision measuring instrument (1), a shaft system motion link module, a high-precision metrology link module, and a host computer processing module; The error separation and compensation method includes: The shaft system motion link module obtains the motion error data of the high-precision measuring instrument, and the host computer processing module compensates the shaft system positioning error of the high-precision measuring instrument according to the motion error data; The high-precision metrology link module obtains the metrology error data of the high-precision measuring instrument, and the host computer processing module compensates the metrology error of the high-precision measuring instrument according to the metrology error data.

2. The error separation and compensation method of the high-precision surface shape measurement system according to claim 1, characterized in that The shaft system motion link module includes: a laser interferometer (2), an autocollimator (3), a high-precision optical lens group (4), a sensing probe (5), a standard sphere (6), and a positioning bracket (7); The laser interferometer (2), the autocollimator (3), and the sensing probe (5) are fixed on the positioning bracket (7); the high-precision optical lens group (4) and the standard sphere (6) are installed on the high-precision measuring instrument (1), and the high-precision optical lens group (4) is respectively combined with the laser interferometer (2) and the autocollimator (3) to form an optical path; the light rays emitted by the laser interferometer (2) and the autocollimator (3) respectively pass through the high-precision optical lens group (4) and advance parallel or perpendicular, and finally return to the laser interferometer (2) and the autocollimator (3), thereby forming an interference optical path and a reflection optical path to realize the off-line measurement of the motion error data of the high-precision measuring instrument.

3. The error separation and compensation method of the high-precision surface shape measurement system according to claim 2, characterized in that The high-precision surface shape measurement system further includes a signal transmission module; the output ends of the laser interferometer (2), the autocollimator (3), and the sensing probe (5) are connected to the signal transmission module.

4. The error separation and compensation method of the high-precision surface shape measurement system according to claim 3, characterized in that The high-precision metrology link module includes: a standard part (8), a high-precision displacement sensor (9), a data acquisition card (10), and a positioning mechanism (11); The standard part (8) is cylindrical and is fixedly placed on the moving shaft of the high-precision measuring instrument (1); the high-precision displacement sensor (9) is fixed on the positioning mechanism (11); the positioning mechanism (11) is fixed on the outer periphery of the moving shaft of the high-precision measuring instrument (1); the high-precision displacement sensor (9) is connected to the data acquisition card (10), and the high-precision displacement sensor (9) is used to on-line measure the radial data and axial data of the standard part (8) and transmit the measurement data to the data acquisition card (10); the data acquisition card (10) performs signal conversion on the measurement data of the high-precision displacement sensor (9) and transmits the converted data to the computer (12) through the signal transmission module; the output end of the data acquisition card (10) is connected to the signal transmission module.

5. The method for error separation and compensation of the high-precision surface shape measurement system according to claim 3, characterized in that the host computer processing module includes: a computer (12), a data acquisition unit (13), an environmental compensation unit (14), and an error separation and compensation unit (15); the outputs of the shafting motion link module and the high-precision metrology link module are respectively transmitted to the data acquisition unit (13) on the computer (12) through the signal transmission module; the output end of the environmental compensation unit (14) is connected to the computer (12); the computer (12) acquires the measurement data of the shafting motion link module and the measurement data of the high-precision metrology link module through the data acquisition unit (13); the data acquisition unit (13) outputs and transmits the measurement data to the error separation and compensation unit (15) for processing, and according to the processing result of the error separation and compensation unit (15), a compensation feedback instruction is generated and the compensation instruction is fed back to the drive system of the high-precision measuring instrument (1), and according to the compensation feedback instruction, offline measurement and online compensation of the shafting motion link module and online measurement and offline compensation of the high-precision metrology link module are respectively performed.

6. The error separation and compensation method for the high-precision surface shape measurement system according to claim 5, characterized in that, The "shafting motion link module obtains the motion error data of the high-precision measuring instrument, and the host computer processing module compensates the shafting positioning error of the high-precision measuring instrument according to the motion error data; the high-precision metrology link module obtains the metrology error data of the high-precision measuring instrument, and the host computer processing module compensates the metrology error of the high-precision measuring instrument according to the metrology error data", which specifically includes the following steps: S1. Install the high-precision optical lens group (4) on the motion axis of the high-precision measuring instrument (1), and at the same time fix the laser interferometer (2) on the metrology reference position of the high-precision measuring instrument (1) through the positioning bracket (7). Connect the computer (12) with the laser interferometer (2) and the environmental compensation unit (14). After preheating each device, synchronously initialize the measurement environment of the shafting motion link module and the high-precision metrology link module through the data acquisition unit (13), and adjust the positioning bracket (7), the laser interferometer (2) and the high-precision optical lens group (4) so that the laser emitted by the laser interferometer (2) returns to its receiving end after passing through the interference optical path. S2. Control the motion axis of the high-precision measuring instrument (1) to reciprocate along a preset route, and at the same time, the environmental compensation unit (14) corrects the temperature and humidity in real time. The linear error, straightness, angular deviation and the degree of freedom of the motion axis of the high-precision measuring instrument (1) are offline collected by using the laser interferometer (2) and the high-precision optical lens group (4), and the measured data are transmitted to the computer (12) through the data acquisition unit (13). S3. Offline measure the roll angle of the motion axis of the high-precision measuring instrument (1) by using the autocollimator (3) and the high-precision optical lens group (4), and transmit the measured data to the computer (12) through the data acquisition unit (13). S4. The moving axis of the high-precision measuring instrument (1) rotates, driving the standard sphere (6) to rotate. The vertex data during the rotation of the standard sphere (6) is measured by the sensing probe (5), and the measured data is transmitted to the computer (12) through the data acquisition unit (13). S5. The off-line measurement data of the motion link collected in steps S2 to S4 is input into the error separation and compensation unit (15), and the error separation and compensation unit (15) calculates the positioning error compensation values of the motion axis system of the high-precision measuring instrument (1) in all directions. S6. The standard part (8) is fixedly placed on the moving axis of the high-precision measuring instrument (1) so that their axes coincide. The positioning mechanism (11) is fixedly spaced on the outer periphery of the moving axis of the high-precision measuring instrument (1) in a manner parallel or perpendicular to the axis of the moving axis, and a plurality of high-precision displacement sensors (9) are fixed on the positioning mechanism (11). The radial data and axial data of the standard part (8) are measured by the plurality of high-precision displacement sensors (9), and the measured data is transmitted to the computer (12) through the data acquisition card (10). S7. The computer (12) controls the moving axis of the high-precision measuring instrument (1) to drive the standard part (8) to rotate at a constant speed. At the same time, the high-precision displacement sensors (9) on-line measure the radial error data and axial error data of the standard part (8), and convert the measurement data of the high-precision displacement sensors (9) into signals recognizable by the data acquisition unit (13) through the data acquisition card (10). The data acquisition unit (13) transmits the converted data to the error separation and compensation unit (15), and the error separation and compensation unit (15) decouples and separates the data by the three-point method and the four-point method on the surface to obtain the metrology error data of the moving axis of the high-precision measuring instrument (1). S8. According to the metrology error data of the moving axis of the high-precision measuring instrument (1) and the movement amount after real-time compensation of the moving axis, the metrology error of the high-precision measuring instrument (1) is compensated off-line.

7. The error separation and compensation method of the high-precision surface shape measuring system according to claim 6, characterized in that in the step S5, the "error separation and compensation unit (15) calculates the positioning error compensation values of the motion axis system of the high-precision measuring instrument (1) in all directions" specifically includes the following steps: S51. Based on the relationship between the spatial position of the tip of the measuring head of the high-precision measuring instrument (1) and the multi-axis mechanical coordinates, a multi-axis kinematic model of the machine table of the high-precision measuring instrument (1) is established by using screw theory. S52. Using the multi-axis kinematic model, the forward spatial error of the motion axis system of the high-precision measuring instrument (1) is obtained, and a spatial error model of the motion structure of the axis system of the machine table of the high-precision measuring instrument (1) is established by using screw theory and inverse kinematics algorithm. S53. The computer (12) controls the movement of the moving axis of the high-precision measuring instrument (1), and the laser interferometer (2) is used to measure the movement positioning error during the movement of the moving axis in real time. S54. Based on the motion positioning error, use the spatial error model to compensate the high-precision measuring instrument (1), and determine the amount of motion of each motion axis of the high-precision measuring instrument (1) after error compensation.

8. The method for error separation and compensation of the high-precision surface shape measurement system according to claim 6, characterized in that in the step S8, the offline compensation of the measurement error of the high-precision measuring instrument (1) according to the measurement error data of the motion axis of the high-precision measuring instrument (1) and the amount of motion after real-time compensation of the motion axis includes: Based on the measurement error data of the motion axis of the high-precision measuring instrument (1) and the amount of motion after real-time compensation of the motion axis, establish a spatial error transfer model of the measurement link, and use the spatial error transfer model of the measurement link to perform offline compensation on the measurement error of the high-precision measuring instrument (1).

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