A laser tracker base station calibration device based on an external reference benchmark

Abstract

A laser tracker base station calibration device based on an external reference benchmark includes a precision turntable device. The precision turntable device is connected to an electromagnet adjustment device and a target mirror adjustment device. The electromagnet adjustment device and the target mirror adjustment device work together to achieve high-precision determination of the target mirror position. The precision turntable device consists of a base, a rotating frustum, a support, and a pull rod. Electromagnet adjustment devices are installed at the four corners of the base, providing two degrees of freedom of movement to achieve precise adjustment of the electromagnet position. The target mirror adjustment device is installed on the rotating frustum, enabling fine-tuning of the target mirror assembly in three degrees of freedom to ensure precise adsorption between the precision ball and the electromagnet, thereby accurately determining the target mirror position. This invention has a compact structure, is easy to adjust, and can efficiently and accurately complete the base station calibration of a laser tracker, significantly reducing the impact of human error and improving the reliability and efficiency of calibration.

Description

Technical Field

[0001] This utility model belongs to the field of precision measurement technology, specifically relating to a laser tracker base station calibration device based on an external reference benchmark. Background Technology

[0002] As a high-precision three-dimensional dynamic measuring instrument, the laser tracker has inherent advantages in machine tool error detection and has been widely used in the field of CNC machine tool precision testing. The detection process of the laser tracker mainly includes two parts: base station calibration and measurement point measurement. The accuracy of the measurement point measurement depends on the accuracy of the base station calibration. Therefore, improving the accuracy of the base station calibration is crucial to improving the measurement accuracy of the laser tracker.

[0003] Currently, scholars and enterprises have conducted extensive research on the calibration of laser tracker base stations. Base station calibration has evolved through several stages: single-station method (Zhang Yajuan. Research on Single-Station Laser Tracking Coordinate Measurement System [D]. Tianjin: Tianjin University, 2012. DOI:10.7666 / d.D285786.), multi-station method (Ma Shoudong, Gao Dong, Lu Yong. Optimization of Sequential Multi-Station Measurement Stations for Trackers Based on Minimum PDOP [J]. Acta Metrologica Sinica, 2023, 44(02):157-164.), and multi-station time-sharing measurement method (Wang Jindong, Sun Rongkang, Zeng Xiaotao, et al. Research on Base Station Layout for Multi-Station Time-Sharing Laser Tracking [J]. Chinese Journal of Lasers, The evolution process of base station calibration (2018, 45(04):231-238.) In addition, some scholars have studied the spatial layout of base stations (Yan Yang, Xia Wenjie, Lin Hu. Research on calibration point layout of laser tracking multi-sided asynchronous measurement system [J]. Journal of Metrology, 2023, 44(08):1188-1195.). All of the above studies have had a positive impact on the accuracy of base station calibration, but there is a common problem. When calibrating base stations using the above methods, the coordinate readings of the machine tool system are often used. The machine tool itself contains various errors of the CNC machine tool, which will introduce the calibration results into the machine tool's own errors, making it impossible to trace the source and evaluate the error. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a laser tracker base station calibration device based on an external reference standard. This device calibrates the laser tracker base station using an external physical standard. Target mirror positioning is achieved by sequentially attracting four sets of non-coplanar electromagnets to three non-coplanar precision spheres. Subsequently, the laser tracker base station is calibrated using a polygonal method. This base station calibration device not only effectively avoids errors introduced by machine tool system coordinate readings but also enables traceability of measurement values ​​and error assessment, thus positively impacting the application of laser trackers in machine tool error measurement.

[0005] To achieve the above objectives, the technical solution of this utility model is as follows:

[0006] A laser tracker base station calibration device based on an external reference benchmark includes a precision turntable device, which is connected to an electromagnet adjustment device and a target mirror adjustment device. The electromagnet adjustment device and the target mirror adjustment device work together to achieve high-precision determination of the target mirror position.

[0007] The precision rotary table device includes a base 2, on which a rotating frustum 4 is mounted. The rotating frustum 4 is connected to the output shaft of a stepper motor 16. The stepper motor 16 is fixedly mounted on one side of the rotating frustum 4. A symmetrical support bracket 1 is provided below the base 2 on the opposite side of the stepper motor 16. A pull rod 37 is installed at the center of the bottom of the base 2 for reliably connecting the precision rotary table device to the machine tool spindle.

[0008] The electromagnet adjustment device comprises four sets of electromagnet components, each with an identical structure and symmetrical arrangement. Each set includes a column 3, with its bottom connected to a base 2 and its top connected to a movable base plate 5. The movable base plate 5, movable base side plates 6, and movable base top plate 7 form a closed frame structure. The movable base plate 5 and movable base top plate 7 are each connected to an electromagnet base 8. Both the movable base plate 5 and movable base top plate 7 have elongated slots extending in the left-right direction, allowing the electromagnet base 8 to slide within these slots, thus adjusting the electromagnet 10 in the horizontal direction. An electromagnet base 8 is equipped with an electromagnet connecting plate 9. The electromagnet base 8 has a long slot extending in the front-back direction, allowing the electromagnet connecting plate 9 to slide within the slot, thereby adjusting the displacement of the electromagnet 10 in the front-back direction. An electromagnet 10 is fixed on the electromagnet connecting plate 9. There are two electromagnets 10 inside the closed frame structure and one electromagnet 10 outside the closed frame structure, for a total of three electromagnets 10. All three electromagnets 10 have the ability to make fine adjustments in two orthogonal directions, left and right and front and back, ensuring that they can accurately attract the precision ball 11 in the target mirror adjustment device, thereby achieving high-precision determination of the position of the target mirror 15.

[0009] The target mirror adjustment device is used for high-precision adjustment and positioning of the target mirror 15 during the calibration of the laser tracker base station. It includes a precision ball target mirror base plate 17, which is fixedly mounted on a rotating frustum 4. The precision ball target mirror base plate 17, the precision ball target mirror base side plate 18, and the precision ball target mirror base top plate 28 are connected to form a frame structure. Guide rails 32 are provided on the inner sides of the precision ball target mirror base top plate 28 and the precision ball target mirror base plate 17. The precision ball moving block 19 cooperates with the guide rails 32 via a slider 26. The precision ball 11... The precision ball moving block 19 is connected to the double-headed stud 12. The precision ball moving block 19 is connected to the precision ball fixing seat 23 through the support plate 24 and the support frame 20. The support frame 20 is adjusted up and down on the bolt 22. The transverse slotted structure on the support frame 20 gives it the ability to adjust in the left and right directions, thereby realizing the fine adjustment of the precision ball in the three degrees of freedom of up and down, left and right, and front and back, ensuring accurate alignment with the electromagnet adsorption end. The electric push rod assembly drives the target mirror assembly and the laser tracker to obtain the accurate position of the laser tracker in the machine tool coordinate system.

[0010] The target mirror assembly includes a precision ball holder 23, which is connected to a target mirror holder side plate 13. The target mirror holder side plate 13 is connected to a target mirror holder base plate 14. A target mirror base 29 is installed on the target mirror holder base plate 14, and a target mirror 15 is connected to the target mirror base 29 to maintain the adjusted position of the target mirror 15.

[0011] The electric push rod assembly includes an electric push rod connecting plate 35, which is connected to the side plate 18 of the precision ball target mirror base. The electric push rod 31 is mounted on the rotating frustum 4 via the electric push rod base plate 30 and drives the target mirror assembly to move forward. A spring rod 33 and a spring 36 are provided between the precision ball moving block 19 and the side plate 18 of the precision ball target mirror base, which are used to automatically reset the target mirror assembly after the electric push rod 31 retracts.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0013] First, the use of an external reference standard avoids systematic errors caused by the machine tool's own coordinate system, effectively improving the calibration accuracy of the laser tracker base station and enabling error separation and traceability, ensuring high precision and consistency. Second, the electromagnet adjustment device has a two-degree-of-freedom fine-tuning function, the target mirror adjustment device achieves three-degree-of-freedom fine-tuning and automatic reset, and the precision turntable device is stable and reliable. The overall structural design is reasonable, ensuring the stability and adaptability of the system. This device uses four sets of three-point electromagnetic adsorption positioning methods to ensure high repeatability and reliability of the target mirror; simultaneously, the electric push rod drive and spring pull rod structure achieve smooth movement and automatic reset of the target mirror, greatly improving the efficiency and simplicity of operation and reducing human error. Attached image description:

[0014] Figure 1 This is a front view of an embodiment of the present utility model.

[0015] Figure 2 This is an isometric view of an embodiment of the present invention.

[0016] Figure 3 This is a schematic diagram of the electromagnet adjustment device according to an embodiment of the present invention.

[0017] Figure 4 This is a front view of the target mirror adjustment device according to an embodiment of this utility model.

[0018] Figure 5 This is a side view of the target mirror adjustment device according to an embodiment of the present invention.

[0019] 1. Bracket; 2. Base; 3. Column; 4. Rotating frustum; 5. Movable seat base plate; 6. Movable seat side plate; 7. Movable seat top plate; 8. Electromagnet base; 9. Electromagnet connecting plate; 10. Electromagnet; 11. Precision ball; 12. Double-ended stud; 13. Target mirror mounting base side plate; 14. Target mirror mounting base base plate; 15. Target mirror; 16. Stepper motor; 17. Precision ball target mirror base base plate; 18. Precision ball target mirror base side plate; 19. 20. Precision ball moving block; 21. Support frame; 22. Set screw; 23. Bolt; 24. Precision ball fixing seat; 25. Support plate; 26. Nut; 27. Slider; 28. Baffle plate; 29. ​​Top plate of precision ball target mirror base; 30. Target mirror base; 31. Electric push rod base plate; 32. Electric push rod; 33. Guide rail; 34. Spring pull rod; 35. Electric push rod support frame; 36. Electric push rod connecting plate; 37. Tension spring; 38. Pull rod. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0021] Reference Figure 1 , Figure 2 A laser tracker base station calibration device based on an external reference benchmark includes a precision turntable device, which is connected to an electromagnet adjustment device and a target mirror adjustment device. The electromagnet adjustment device and the target mirror adjustment device work together to achieve high-precision determination of the position of the target mirror 15.

[0022] Reference Figure 1 , Figure 2The precision rotary table device includes a base 2, a rotating frustum 4, a stepper motor 16, a bracket 1, and a tie rod 37. The rotating frustum 4 is mounted on the base 2 and is connected to the output shaft of the stepper motor 16. The stepper motor 16 is fixedly mounted on one side of the rotating frustum 4 and drives the rotating frustum 4 to achieve precise angle rotation adjustment. To improve the overall stability of the rotating device, a symmetrical support bracket 1 is provided below the base 2 on the opposite side of the stepper motor 16 to form a structural balance support. At the same time, a tie rod 37 is installed at the center of the bottom of the base 2 to reliably connect the precision rotary table device to the machine tool spindle. It has the advantages of high rotational accuracy, good support stability, and reliable installation and connection.

[0023] Reference Figure 1 , Figure 2 , Figure 3 The electromagnet adjustment device comprises four sets of electromagnet components, each with an identical structure and symmetrical arrangement. The following description uses the first set of electromagnet components as an example. Each electromagnet component includes a column 3, a base plate 5, a side plate 6, a top plate 7, an electromagnet base 8, an electromagnet connecting plate 9, and an electromagnet 10. The bottom of the column 3 is connected to the base 2, and the top of the column 3 is connected to the base plate 5 by bolts. The base plate 5, side plate 6, and top plate 7 form a closed frame structure with bolts, providing adjustment space for the electromagnet 10. The base plate 5 and top plate 7 are each connected to an electromagnet base 8 by bolts. Both the base plate 5 and top plate 7 have elongated slots extending in the left-right direction, allowing the electromagnet base 8 to slide within these slots. The device allows for horizontal adjustment of the electromagnet 10. Each electromagnet base 8 is bolted to an electromagnet connecting plate 9. The electromagnet base 8 has a long slot extending in the front-to-back direction, allowing the connecting plate 9 to slide within the slot, thus adjusting the electromagnet 10's displacement in the front-to-back direction. The electromagnet 10 is fixed to the connecting plate 9 with bolts. Two electromagnets 10 are located inside the closed frame structure, and one electromagnet 10 is located outside the closed frame structure, totaling three electromagnets 10. All three electromagnets 10 possess fine-tuning capabilities in two orthogonal directions (left-right and front-to-back), ensuring accurate attraction to the precision ball 11 in the target mirror adjustment device, thereby achieving high-precision positioning of the target mirror 15. This device is compact, flexible in adjustment, and easy to install, improving the reliability and repeatability of the calibration process.

[0024] Reference Figure 1 , Figure 2 , Figure 4 , Figure 5The target mirror adjustment device is used for high-precision adjustment and positioning of the target mirror during the calibration process of the laser tracker base station. It includes a precision ball target mirror base plate 17, a precision ball target mirror base side plate 18, a precision ball target mirror base top plate 28, a guide rail 32, a slider 26, a precision ball moving block 19, a support plate 24, a support frame 20, a precision ball fixing seat 23, a double-ended stud 12, a precision ball 11, a target mirror fixing seat side plate 13 and a target mirror fixing seat base plate 14, a target mirror base 29, a target mirror 15, an electric push rod connecting plate 35, an electric push rod 31, an electric push rod base plate 30, a spring pull rod 33, a spring 36, and a baffle 27, etc. The precision ball target mirror base plate 17 is fixedly installed on the rotating frustum 4. The precision ball target mirror base plate 17, the precision ball target mirror base side plate 18, and the precision ball target mirror base top plate 28 are connected by bolts to form a frame structure. The precision ball target mirror base plate 17 has a guide rail 32 on its inner side. The precision ball moving block 19 is connected to the guide rail 32 by a slider 26 and can slide along the guide rail 32 in the front and back direction. The precision ball moving block 19 is connected to the precision ball fixing seat 23 by a support plate 24 and a support frame 20. The precision ball 11 is connected to the precision ball fixing seat 23 by a double-headed stud 12. The support frame 20 can be adjusted up and down by adjusting the height on the bolt 22. The transverse slotted structure on the support frame 20 gives it the ability to adjust in the left and right direction, thereby realizing the fine adjustment of the precision ball in the three degrees of freedom of up and down, left and right, and front and back, ensuring accurate alignment with the electromagnet adsorption end. The precision ball target mirror base top plate 28 and the precision ball target mirror base base plate 17 are equipped with baffles 27 to prevent the slider 26 from disengaging from the guide rail 32. The electric push rod assembly drives the target mirror assembly and the laser tracker to obtain the accurate position of the laser tracker in the machine tool coordinate system.

[0025] The target mirror assembly includes a precision ball mount 23, which is connected to the target mirror mount side plate 13 by bolts. The target mirror mount side plate 13 is connected to the target mirror mount base plate 14 by bolts. A target mirror base 29 is installed on the target mirror mount base plate 14, and a target mirror 15 is connected to the target mirror base 29 to maintain the adjusted position of the target mirror 15.

[0026] The electric push rod assembly includes an electric push rod connecting plate 35, which is connected to the side plate 18 of the precision ball target mirror base. The electric push rod 31 is mounted on the rotating frustum 4 via the electric push rod base plate 30 and drives the target mirror assembly to move forward. A spring rod 33 and a spring 36 are provided between the precision ball moving block 19 and the side plate 18 of the precision ball target mirror base, which are used to automatically reset the target mirror assembly after the electric push rod 31 retracts. It has a three-degree-of-freedom fine adjustment function and automatic reset capability, and can efficiently and accurately complete the alignment and calibration of the laser tracker target mirror.

[0027] The working principle of this utility model is as follows:

[0028] Start the stepper motor 16, and the rotating platform 4 drives the target mirror 15 to move. When the target mirror 15 reaches the first set of electromagnet components, stop the stepper motor 16, start the electric push rod 31, and push the precision ball moving block 19 forward. After the electric push rod 31 reaches its maximum stroke, energize the first set of electromagnets, manually adjust the position of the precision ball 11 and the first set of electromagnets until they are perfectly attracted. Then, use bolts to fix the position of the electromagnets at this time, thereby determining the first spatial position of the target mirror 15. Then, return the electric push rod 31 to the initial position. After that, the first set of electromagnets is de-energized. Due to the tension of the tension spring 36, the precision ball fixing seat 23 and the precision ball moving block 19 drive the target mirror 15 back to the initial position.

[0029] Then, the stepper motor 16 is started, and the rotating platform 4 continues to drive the target mirror 15 to rotate by 90°. At this time, the target mirror 15 reaches the second set of electromagnet components. The stepper motor 16 is turned off, and the process of the first set of electromagnets and precision ball adsorption is repeated. The position of the electromagnets is fixed with bolts, and then the second spatial position of the target mirror is obtained. After that, the second set of electromagnets is de-energized and demagnetized, and the target mirror 15 continues to return to the initial position.

[0030] The process of determining the third and fourth spatial positions of the target mirror 15 is the same as that of the first and second spatial positions. After determining the four spatial positions of the target mirror 15, the spatial coordinates of the four target mirror positions in the high-precision three-coordinate calibration instrument are used to deduce the relative positional relationship of the target mirror 15 in the instrument. Thus, the position of the target mirror at the other three positions can be represented by the first target mirror position, thereby completing the spatial calibration of the target mirror position.

[0031] After completing the above spatial calibration, the laser tracker base station calibration is performed. First, the calibration instrument used by the device is connected to the CNC machine tool spindle via pull rod 37. Then, the first set of electromagnets is energized to generate magnetism, and then the stepper motor 16 runs, sending the target mirror 15 to the first set of electromagnet components via the rotating frustum 4. Then, the electric push rod 31 pushes the target mirror 15 forward. When the precision ball 11 and the target mirror 15 are completely attracted, the first position of the target mirror 15 is determined. The distance L1 between the target mirror 15 and the laser tracker is measured using the laser tracker's length measurement technology. Then, through coordinate system transformation, the spatial coordinate system of the measuring instrument and the machine tool coordinate system are made consistent, thereby determining the spatial coordinates P1(x, y, z) of the target mirror 15 at the first position. Then, the stepper motor 16 continues... The system operates, moving the target mirror 15 to the second set of electromagnet components. The distance value L2 measured by the laser tracker at this time is recorded. Then, the distance values ​​L3 and L4 of the target mirror 15 moving to the third and fourth sets of electromagnet components are recorded respectively. Since the spatial position relationship of the four target mirrors has been derived in the above calibration process, after determining the spatial coordinates of the first target mirror, the coordinates of the other three target mirrors P2, P3, and P4 can be expressed by spatial transformation. After obtaining the four spatial coordinates of the target mirror 15 and the distances between these four positions and the laser tracker, the polygonal method measurement principle can be used to solve the problem using the formula for the distance between two points. Since there are only three unknowns, four equations can be established, thus the accurate position of the laser tracker in the machine tool coordinate system can be solved.

[0032] As can be seen from the above, the base station calibration device of this utility model not only has good positioning accuracy, but also adopts an external reference standard, which can effectively avoid the influence of the coordinate reading error of the machine tool system, and can perform value traceability and error separation of the measurement results. It has the advantages of high efficiency, convenience and easy operation.

Claims

1. An external reference based laser tracker base station alignment apparatus, characterized by: It includes a precision turntable device, which is connected to an electromagnet adjustment device and a target mirror adjustment device. The electromagnet adjustment device and the target mirror adjustment device work together to achieve high-precision determination of the target mirror position.

2. The laser tracker base station calibration apparatus of claim 1, wherein: The precision rotary table device includes a base (2), on which a rotating frustum (4) is mounted. The rotating frustum (4) is connected to the output shaft of a stepper motor (16). The stepper motor (16) is fixedly mounted on one side of the rotating frustum (4). A pull rod (37) is installed at the center of the bottom of the base (2) for connecting the precision rotary table device to the machine tool spindle.

3. The laser tracker base station calibration apparatus of claim 2, wherein: The electromagnet adjustment device has four sets of electromagnet components, each with the same structure and symmetrical arrangement. Each set of electromagnet components includes a column (3), the bottom of which is connected to the base (2), and the top of which is connected to the movable seat base plate (5). The movable seat base plate (5), the movable seat side plate (6), and the movable seat top plate (7) form a closed frame structure. The movable seat base plate (5) and the movable seat top plate (7) are respectively connected to an electromagnet base (8). Both the movable seat base plate (5) and the movable seat top plate (7) are provided with long slots extending in the left and right directions. The electromagnet base (8) is located on the long... Sliding within the slot; each electromagnet base (8) is equipped with an electromagnet connecting plate (9), and the electromagnet base (8) is provided with a long slot extending in the front-back direction, so that the electromagnet connecting plate (9) slides within the long slot; an electromagnet (10) is fixed on the electromagnet connecting plate (9), and two electromagnets (10) are provided inside the closed frame structure, and one electromagnet (10) is provided outside the closed frame structure, for a total of three electromagnets (10). All three electromagnets (10) have the ability to make fine adjustments in the two orthogonal directions of left and right and front and back, so as to ensure that they can accurately attract the precision ball in the target mirror adjustment device and realize the high-precision determination of the target mirror position.

4. The laser tracker base station calibration apparatus of claim 3, wherein: The target mirror adjustment device is used for high-precision adjustment and positioning of the target mirror position during the calibration process of the laser tracker base station. It includes a precision ball target mirror base plate (17), which is fixedly installed on a rotating frustum (4). The precision ball target mirror base plate (17), the precision ball target mirror base side plate (18), and the precision ball target mirror base top plate (28) are connected to form a frame structure. The precision ball target mirror base top plate (28) and the precision ball target mirror base base plate (17) are provided with guide rails (32). The precision ball moving block (19) is connected by a guide rail (32) on the inner side of the precision ball target mirror base top plate (28) and the precision ball target mirror base base plate (17). The slider (26) cooperates with the guide rail (32); the precision ball moving block (19) is connected to the precision ball fixing seat (23) through the support plate (24) and the support frame (20). The support frame (20) can be adjusted up and down. The transverse slotted structure on the support frame (20) enables it to be adjusted in the left and right directions, thereby realizing the fine adjustment of the precision ball in the three degrees of freedom of up and down, left and right, and front and back, ensuring accurate alignment with the electromagnet adsorption end; the electric push rod assembly drives the target mirror assembly and the laser tracker to obtain the accurate position of the laser tracker in the machine tool coordinate system.

5. The laser tracker base station calibration apparatus of claim 4, wherein: The target mirror assembly includes a precision ball mount (23), which is connected to the target mirror mount side plate (13). The target mirror mount side plate (13) is connected to the target mirror mount base plate (14). The target mirror base (29) is installed on the target mirror mount base plate (14), and the target mirror (15) is connected to the target mirror base (29) to maintain the adjusted position of the target mirror (15).

6. The laser tracker base station calibration apparatus of claim 4, wherein: The electric push rod assembly includes an electric push rod connecting plate (35), which is connected to the side plate (18) of the precision ball target mirror base. The electric push rod (31) is mounted on the rotating frustum (4) through the electric push rod base plate (30) and drives the target mirror assembly to move forward. A spring rod (33) and a spring (36) are provided between the precision ball moving block (19) and the side plate (18) of the precision ball target mirror base, so that the target mirror assembly can be automatically reset after the electric push rod (31) retracts.

Images