Encoder calibration system and method based on constant temperature vibration isolation and laser array
By constructing an internal 'absolute reference' through an encoder calibration system based on constant temperature vibration isolation and laser array, high-precision and stable encoder calibration is achieved. This solves the problems of environmental sensitivity and high cost in traditional technologies, reduces calibration costs, and improves accuracy and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-13
- Publication Date
- 2026-07-03
AI Technical Summary
Existing high-precision encoder calibration technologies are sensitive to the environment, have poor anti-interference capabilities, and rely on high-cost standards, resulting in high calibration costs and limited accuracy.
An encoder calibration system based on constant temperature vibration isolation and laser array is adopted, including a ground constant temperature vibration isolation base, mechanical transmission chain, laser emission and vision inspection system and data processing and automatic compensation system, to build an internal 'absolute benchmark' and realize fully automated calibration.
It achieves high-precision and stable encoder calibration, reduces construction and maintenance costs, avoids human intervention errors, and achieves calibration accuracy and long-term stability better than 5 arcseconds.
Smart Images
Figure CN122329384A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of precision measurement and instrument calibration technology, and particularly relates to an encoder calibration system and method based on constant temperature vibration isolation and laser array. Background Technology
[0002] The accuracy of rotary encoders is one of the core factors determining the motion control performance of high-end equipment (such as high-precision machine tools, industrial robots, and astronomical telescopes). Pre-shipment calibration and regular calibration are therefore crucial.
[0003] Currently, traditional high-precision encoder calibration techniques mainly rely on higher-precision photoelectric encoders or circular gratings as benchmarks for direct comparative measurements. This method has several inherent bottlenecks: High environmental sensitivity: The calibration process is extremely demanding in terms of environment (especially temperature). Even small temperature fluctuations (usually > ±1℃) can cause thermal deformation of mechanical references (such as standard shaft system and mounting base), introducing significant measurement reference drift and making it impossible to guarantee the long-term stability of calibration results.
[0004] Poor anti-interference capability: External environmental vibrations (such as ground vibration and air flow) are difficult to effectively isolate and are easily coupled into the measurement signal, which generally limits the calibration accuracy and makes it difficult to stably exceed 30 arcseconds.
[0005] Reliance on high-cost standards and the existence of technological monopolies: The higher-precision standards used as benchmarks (such as ultra-high-precision photoelectric encoders) are themselves extremely expensive to manufacture and complex to maintain, resulting in high construction and operation costs for the entire calibration system. At the same time, this chain dependence also means that the calibration accuracy is ultimately limited by the availability and technological level of the highest standard, forming a technological barrier.
[0006] Therefore, there is an urgent need in this field for a new encoder calibration technology that can eliminate the dependence on expensive high-precision scalers and achieve ultra-high precision, high stability and economy in conventional industrial environments. Summary of the Invention
[0007] The purpose of this invention is to address the above-mentioned problems by providing an encoder calibration system based on constant temperature vibration isolation and a laser array; The purpose of this invention is to address the above-mentioned problems by providing an encoder calibration method based on constant temperature vibration isolation and laser array.
[0008] To achieve the above objectives, the present invention adopts the following technical solutions: An encoder calibration system based on constant temperature vibration isolation and laser array includes a ground constant temperature vibration isolation base, a mechanical transmission chain, a laser emission and vision inspection system, and a data processing and automatic compensation system; The ground-based constant temperature vibration isolation base provides the system with a physical basis for high stability, constant temperature and vibration isolation; The mechanical transmission chain includes a reference shaft, a measured shaft, and a speed-increasing mechanism. The reference shaft is connected to a reference drive device, the measured shaft is connected to the motor of the encoder to be calibrated, and the input end of the speed-increasing mechanism is connected to the reference shaft, while the output end is connected to a laser emitting disk, which is used to amplify the angular difference between the reference shaft and the laser emitting disk. The laser emission and visual inspection system includes a laser emission array disposed on the laser emission disk, a beam shaping component, a calibration target disposed at a distance, and a visual recognition component for photographing the calibration target. The beam emitted by the laser emission array is shaped and then illuminates the calibration target. The data processing and automatic compensation system is electrically connected to the visual recognition component, and is used to receive the visual recognition result, calculate the encoder angle error based on the offset of the light spot on the calibration target, generate an error compensation table, and write the error compensation table into the encoder to be calibrated to achieve automatic compensation.
[0009] In the aforementioned encoder calibration system based on constant temperature vibration isolation and laser array, the ground constant temperature vibration isolation base includes: a high-stability floor, a precision temperature control system, and an active vibration isolation design; the high-stability floor is a composite structural layer; the precision temperature control system controls the system ambient temperature within a set temperature range; the active vibration isolation design includes vibration isolation grooves set around the foundation to suppress the natural frequency of the foundation and isolate the transmission of ground vibration.
[0010] In the encoder calibration system based on constant temperature vibration isolation and laser array described above, the reference drive device is a high-torque direct drive motor, and the speed-increasing mechanism is a harmonic reducer with a transmission ratio of 100:1.
[0011] In the encoder calibration system based on constant temperature vibration isolation and laser array described above, the laser emission array consists of 32 lasers evenly distributed on the circumference of the laser emission disk, and the beam shaping component is a laser beam reducer set at the front end of each laser. The beam reducer is composed of a double aspherical lens group and is used to compress the laser divergence angle.
[0012] In the encoder calibration system based on constant temperature vibration isolation and laser array described above, the calibration target is a high-precision scale plate located 100 meters away from the laser emitting disk, and the visual recognition component includes a high-resolution CCD industrial camera and a telecentric lens.
[0013] In the aforementioned encoder calibration system based on constant temperature vibration isolation and laser array, the visual recognition software module built into the data processing and automatic compensation system performs the following steps: Image acquisition, ROI extraction and preprocessing, sub-pixel localization of the spot center using an algorithm combining gray-scale centroid method and Gaussian fitting method, and calculation of the deviation between the spot center point coordinates and the theoretical coordinates.
[0014] In the encoder calibration system based on constant temperature vibration isolation and laser array described above, the data processing and automatic compensation system is used to automatically calculate the angle error of the encoder to be calibrated according to the following formula: Δθ = arctan(Δx / L) / N, where Δθ is the angle error of the encoder to be calibrated, Δx is the spot offset on the calibration target measured by the vision recognition component, L is the distance from the laser emitting disk to the calibration target, and N is the transmission ratio of the speed-increasing mechanism.
[0015] An encoder calibration method based on isothermal vibration isolation and laser array includes the following steps: System temperature control and preheating startup; The reference shaft is driven to rotate at a constant speed by the reference driving device. The visual recognition component acquires images of laser spots on the calibration target, and the visual recognition software module automatically calculates the spot offset at all angular positions. The data processing and automatic compensation system calculates the full-range angle error of the encoder to be calibrated according to the formula Δθ = arctan(Δx / L) / N, and generates an error compensation table. The error compensation table is written into the non-volatile memory of the encoder to be calibrated to complete automatic compensation.
[0016] In the encoder calibration method based on constant temperature vibration isolation and laser array described above, the specific steps of automatically calculating the spot offset using the visual recognition software module include: Image acquisition: The camera is triggered at a specific angle position of the encoder to capture the image of the scale plate.
[0017] ROI Extraction and Preprocessing: The software automatically delineates the region of interest based on the theoretical location and performs grayscale conversion, filtering, and noise reduction to enhance the signal-to-noise ratio.
[0018] Center positioning: An algorithm combining gray-scale centroid method and Gaussian fitting method is used to perform sub-pixel calculations to accurately solve the coordinates of the energy center point of the light spot, with a positioning accuracy better than 0.1 pixels.
[0019] Deviation calculation: The calculated actual center coordinates are compared with the theoretical coordinates to obtain the deviation value Δx, which is then automatically recorded in the data table corresponding to that angle point.
[0020] In the encoder calibration method based on constant temperature vibration isolation and laser array described above, the calibration is performed in an environment with constant temperature of 20±0.05℃, vibration isolation, and a system natural frequency of less than 2Hz.
[0021] Compared with existing technologies, the advantages of this invention are: A brand-new "absolute benchmark" calibration system has been constructed: the accuracy of this invention comes from multiple independent and stable physical and mechanical elements (constant temperature environment, high stability foundation, direct drive motor motion stability, accurate mechanical transmission ratio, laser linear propagation characteristics and precision scale), which together constitute an internal "absolute benchmark" that does not need to be compared with a higher precision external standard. This breaks the technical monopoly of traditional chain traceability and significantly reduces the construction cost and maintenance threshold of the calibration system.
[0022] This system achieves "three-stage amplification" and automated detection: It pioneers a three-stage amplification and detection architecture combining "mechanical speed increase (100x) + ultra-long optical lever (100-meter optical path) + visual sub-pixel recognition." First, mechanical speed increase amplifies minute angular errors at the nanoradian level. Then, an optical lever constructed from a 100-meter optical path converts the angular error into a linear displacement at the 100-micrometer level for secondary amplification. Finally, a high-precision vision system performs sub-pixel-level automated detection. This non-contact detection path offers extremely high resolution and avoids the friction and backlash errors associated with contact measurements.
[0023] It achieves extremely high calibration accuracy and stability: Under the basic guarantee of constant temperature (20±0.05℃) and ultra-low vibration (system natural frequency <2Hz), combined with the above-mentioned high-resolution detection methods, this system can achieve a calibration accuracy better than 5 arcseconds, and the results have good repeatability and excellent long-term stability.
[0024] The entire process is fully automated and closed-loop compensation is achieved: from data acquisition, spot recognition, error calculation to generating and writing the compensation table, the whole process is completely automated and controlled by computer software, which completely eliminates the errors and uncertainties introduced by manual intervention. It is highly efficient and consistent, laying the foundation for the industrial-scale batch calibration of encoders. Attached Figure Description
[0025] Figure 1 This is an overall schematic diagram of the present invention.
[0026] In the figure: 101, ground constant temperature vibration isolation base; 102, reference axis; 103, measured axis; 104, 1:100 harmonic reducer; 105, laser emitting disk; 106, laser; 107, high-precision scale plate (remote calibration target) and CCD vision system; 108, laser beam reducer. Detailed Implementation
[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0028] This embodiment provides an encoder calibration system based on constant temperature vibration isolation and a laser array, combined with... Figure 1 As shown, Figure 1 As shown, this embodiment provides a high-precision encoder calibration system based on ground constant temperature vibration isolation and laser array, which is set up in a precision temperature control laboratory.
[0029] Ground-based constant temperature vibration isolation base (101): This consists of a three-layer structure: a lower reinforced concrete foundation, a middle granite platform, and an upper marble workbench. The overall laboratory environment temperature is controlled at 20±0.05℃ by a precision air conditioning system. A vibration isolation trench, 1.5 meters deep and 0.3 meters wide, is excavated around the foundation and filled with high-damping polyurethane material to isolate the system from ground vibration. The overall natural frequency of the system is below 2Hz.
[0030] Mechanical transmission chain: The reference drive device uses a high-torque direct drive (DD) motor (102) with an output torque of 500 N·m as a high-stability rotation reference. The servo motor (103) to be calibrated has a built-in encoder that is directly connected to the main shaft of the DD motor (102) through a high-rigidity coupling. The input end of a 1:100 precision harmonic reducer (104) is connected to the main shaft of the DD motor (102), and a laser emitting disk (105) is mounted on its output shaft.
[0031] Laser emission and visual inspection system: A laser emission disk (105) with a diameter of 200 mm has 32 semiconductor lasers (106) with a wavelength of 650 nm evenly installed on its circumference. Each laser (106) is equipped with a laser beam reducer (108) composed of two aspherical lenses at its front end, which compresses the divergence angle of the laser beam to within 0.1 mrad, forming a fine beam with excellent collimation. A high-precision optical glass scale plate is installed parallel to the laser emission disk (105) as a calibration target (107). A Basler ace acA2440-75um CCD industrial camera with a telecentric lens is aligned with the scale plate to capture the laser spot image.
[0032] Data processing and automatic compensation system: This is a high-performance industrial computer with built-in dedicated vision processing software and calibration algorithm software. The CCD camera is connected to the computer via a gigabit network cable.
[0033] The calibration process is as follows: System preheating: Turn on the temperature control system and preheat the laboratory for 48 hours, with temperature fluctuations less than 0.02℃. Run the DD motor (102) at a low speed of 0.05rpm for 2 hours to preheat the bearings.
[0034] Data Acquisition: The calibration procedure is initiated. The DD motor (102) rotates at a constant low speed of 0.1 rpm. Based on the feedback signal from the encoder, the system uniformly selects at least 1000 angular positions as sampling points within one revolution of the encoder. At each sampling point, the computer triggers the CCD camera to capture an image of the scale plate (107).
[0035] Image processing and data processing: The vision software automatically reads the image and performs grayscale and filtering processing within the predetermined region of interest (ROI). Then, an algorithm combining the grayscale centroid method and Gaussian fitting method is used to perform sub-pixel-level center positioning for each laser spot, calculate the actual coordinates of the center of each spot, and compare them with its theoretical coordinates to obtain the offset Δx (unit: micrometers).
[0036] Error Calculation and Compensation: The computer collects Δx data from all sampling points and substitutes it into the formula Δθ = arctan(Δx / L) / N, where L = 100 meters = 100,000 millimeters and N = 100, to calculate the encoder's angular error Δθ at each sampling point. Using this data, the system fits and generates a high-resolution error compensation table covering the entire encoder range.
[0037] Write the compensation table: The error table is written to the encoder's non-volatile memory via serial port, and the generated error compensation table is written to the EEPROM of the encoder inside the servo motor (103) to be calibrated. In subsequent operations, the encoder can call this table in real time to compensate its output signal, thereby outputting a higher precision angle value.
[0038] Through the above steps, the system described in this embodiment successfully calibrated a 23-bit multi-turn absolute encoder. The residual error after calibration was verified by a third party to be less than 5 arcseconds, and the entire process was completed automatically without manual intervention.
[0039] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
[0040] Although this paper frequently uses terms such as 101, ground-based constant temperature vibration isolation base; 102, reference axis; 103, measured axis; 104, 1:100 harmonic reducer; 105, laser emitting disk; 106, laser; 107, high-precision scale plate (remote calibration target) and CCD vision system; and 108, laser beam shortener, these terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any kind of additional limitation would be contrary to the spirit of the invention.
Claims
1. An encoder calibration system based on constant temperature vibration isolation and laser array, characterized in that, This includes a ground-based constant temperature vibration isolation base, a mechanical transmission chain, a laser emission and vision inspection system, and a data processing and automatic compensation system; The ground-based constant temperature vibration isolation base provides the system with a physical basis for high stability, constant temperature and vibration isolation; The mechanical transmission chain includes a reference shaft, a measured shaft, and a speed-increasing mechanism. The reference shaft is connected to a reference drive device, the measured shaft is connected to the motor of the encoder to be calibrated, and the input end of the speed-increasing mechanism is connected to the reference shaft, while the output end is connected to a laser emitting disk, which is used to amplify the angular difference between the reference shaft and the laser emitting disk. The laser emission and visual inspection system includes a laser emission array disposed on the laser emission disk, a beam shaping component, a calibration target disposed at a distance, and a visual recognition component for photographing the calibration target. The beam emitted by the laser emission array is shaped and then illuminates the calibration target. The data processing and automatic compensation system is electrically connected to the visual recognition component, and is used to receive the visual recognition result, calculate the encoder angle error based on the offset of the light spot on the calibration target, generate an error compensation table, and write the error compensation table into the encoder to be calibrated to achieve automatic compensation.
2. The encoder calibration system based on constant temperature vibration isolation and laser array according to claim 1, characterized in that, The ground-based constant temperature vibration isolation base includes: a high-stability floor, a precision temperature control system, and an active vibration isolation design; the high-stability floor is a composite structural layer; the precision temperature control system controls the system ambient temperature within a set temperature range; the active vibration isolation design includes vibration isolation grooves set around the foundation to suppress the natural frequency of the foundation and isolate the transmission of ground vibrations.
3. The encoder calibration system based on constant temperature vibration isolation and laser array according to claim 1, characterized in that, The reference drive device is a high-torque direct drive motor, and the speed-increasing mechanism is a planetary speed-increasing machine with a transmission ratio of 100:
1.
4. The encoder calibration system based on constant temperature vibration isolation and laser array according to claim 1, characterized in that, The laser emitting array consists of 32 lasers evenly distributed on the circumference of the laser emitting disk. The beam shaping component is a laser beam reducer located at the front end of each laser. The beam reducer is composed of a double aspherical lens group and is used to compress the laser divergence angle.
5. The encoder calibration system based on constant temperature vibration isolation and laser array according to claim 1, characterized in that, The calibration target is a high-precision scale plate located 100 meters away from the laser emission disk, and the visual recognition component includes a high-resolution CCD industrial camera and a telecentric lens.
6. The encoder calibration system based on constant temperature vibration isolation and laser array according to claim 1, characterized in that, The visual recognition software module built into the data processing and automatic compensation system performs the following steps: Image acquisition, ROI extraction and preprocessing, sub-pixel localization of the spot center using an algorithm combining gray-scale centroid method and Gaussian fitting method, and calculation of the deviation between the spot center point coordinates and the theoretical coordinates.
7. The encoder calibration system based on constant temperature vibration isolation and laser array according to claim 1 or 6, characterized in that, The data processing and automatic compensation system is used to automatically calculate the angle error of the encoder to be calibrated according to the following formula: Δθ = arctan(Δx / L) / N, where Δθ is the angle error of the encoder to be calibrated, Δx is the spot offset on the calibration target measured by the vision recognition component, L is the distance from the laser emitting disk to the calibration target, and N is the transmission ratio of the speed-increasing mechanism.
8. A high-precision calibration method for an encoder based on isothermal vibration isolation and a laser array, employing the system described in any one of claims 1 to 7, characterized in that, Includes the following steps: System temperature control and preheating startup; The reference shaft is driven to rotate at a constant speed by the reference driving device. The visual recognition component acquires images of laser spots on the calibration target, and the visual recognition software module automatically calculates the spot offset at all angular positions. The data processing and automatic compensation system calculates the full-range angle error of the encoder to be calibrated according to the formula Δθ = arctan(Δx / L) / N, and generates an error compensation table. The error compensation table is written into the non-volatile memory of the encoder to be calibrated to complete automatic compensation.
9. The calibration method according to claim 8, characterized in that, The specific steps for automatically calculating the light spot offset using the visual recognition software module include: Image acquisition: The camera is triggered at a specific angle position on the encoder to capture an image of the scale plate; ROI extraction and preprocessing: The software automatically delineates the region of interest based on the theoretical location and performs grayscale conversion, filtering and noise reduction, etc., to enhance the signal-to-noise ratio; Center positioning: An algorithm combining gray-scale centroid method and Gaussian fitting method is used to perform sub-pixel calculations to accurately solve the coordinates of the energy center point of the light spot, with a positioning accuracy better than 0.1 pixels; Deviation calculation: The calculated actual center coordinates are compared with the theoretical coordinates to obtain the deviation value Δx, which is then automatically recorded in the data table corresponding to that angle point.
10. The calibration method according to claim 8 or 9, characterized in that, The calibration was performed in an environment with a constant temperature of 20±0.05℃, vibration isolation, and a system natural frequency of less than 2Hz.