System for automatically testing positioning precision of servo motor and servo joint

Abstract

The invention belongs to the technical field of servo system performance testing methods, and particularly relates to an automatic testing system for positioning precision of a servo motor and a servo joint. Comprising a reference positioning module, a time grating signal acquisition module, a servo drive control module, a load simulation module, a multi-dimensional sensing module, a main control and data processing module and a man-machine interaction module. According to the invention, the high-precision time grating encoder is used as a position measurement reference, and the time grating encoder based on the principle of measuring space by time is used as a measurement reference, so that the method has the advantages of ultrahigh measurement precision, strong anti-interference capability and high cost performance, and can still keep stable measurement performance under the low-speed and heavy-load working conditions; meanwhile, the equipment cost and the environment use requirement are greatly reduced, the scene limitation of high-precision test equipment is broken through, and the full-scene application requirements of laboratory precision test and production line batch test can be met at the same time.

Description

Technical Field

[0001] This invention belongs to the technical field of servo system performance testing methods, and particularly relates to an automatic testing system for the positioning accuracy of servo motors and servo joints. Background Technology

[0002] Servo motors and servo joints are core actuators in industrial robots, precision machining equipment, and automated production lines. Their positioning accuracy directly determines the operational accuracy and stability of the final equipment. With the rapid development of the precision manufacturing industry, higher requirements are being placed on the positioning accuracy and repeatability of servo systems. Correspondingly, high-precision and highly automated testing systems are needed to comprehensively test and evaluate the positioning accuracy of servo motors and servo joints.

[0003] Existing positioning accuracy testing systems for servo motors and servo joints still suffer from unresolved industry pain points, primarily manifested in two dimensions. First, the measurement benchmark cannot simultaneously address measurement accuracy, cost, and scenario adaptability. High-precision solutions like laser interferometers are expensive, have stringent requirements for environmental conditions such as temperature, humidity, vibration, and airflow, and have high operational and debugging barriers, making mass deployment in production sites difficult. Conventional solutions like photoelectric encoders, limited by grating engraving processes, are prone to insufficient accuracy and weak anti-interference capabilities under low-speed, heavy-load conditions. Neither of these mainstream solutions can simultaneously meet the diverse needs of both precision laboratory testing and mass industrial testing. Simultaneously, existing testing solutions also exhibit significant deficiencies in testing performance and functional completeness. They are prone to sampling delays due to the driver's communication data reading mode, leading to asynchronous acquisition of control commands, device-under-test (DUT) feedback, and benchmark position data, introducing systematic errors into the test results. Furthermore, they generally suffer from low automation, poor compatibility with various DUT types, and the inability to perform only numerical accuracy measurements without quantifying and tracing errors. Ultimately, this severely limits testing efficiency, result accuracy, and the practical value of the solutions. Summary of the Invention

[0004] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide an automatic testing system for the positioning accuracy of servo motors and servo joints. Using a time encoder as a high-precision position reference, a fully automatic testing platform compatible with multiple types of test devices and multiple working conditions is built. This system enables accurate measurement and error source analysis of positioning accuracy-related indicators, solving the problems of insufficient accuracy, low automation, poor compatibility, and difficulty in error source tracing in traditional testing systems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: An automatic testing system for the positioning accuracy of servo motors and servo joints is provided. The main hardware of the entire system is mounted on a high-rigidity support test bench and includes a reference positioning module, a time grid signal acquisition module, a servo drive control module, a load simulation module, a multi-dimensional sensing module, a main control and data processing module, and a human-machine interaction module.

[0006] As a further optimization of the present invention, the reference positioning module is the core of the system's measurement reference, using a high-precision time-grating encoder as the core component, combined with a coaxial adapter assembly and a fixed platform. The time-grating encoder adopts an absolute time-grating displacement sensor, which utilizes the principle of spatiotemporal coordinate transformation to measure displacement by measuring "space" in "time". Compared with traditional photoelectric encoders, it has higher resolution, stronger anti-interference ability, and lower low-speed measurement error. Its resolution is better than ±0.5 arcseconds, and its measurement accuracy is better than ±1 arcsecond, which can meet the testing requirements of ultra-high precision servo systems. The coaxial adapter assembly includes a corresponding shape adapter plate, a corresponding shape adapter shaft, and a high-rigidity diaphragm coupling. Through the high-rigidity coaxial connection structure, it eliminates the coaxiality error between the output shaft of the test piece and the measuring shaft of the time encoder, avoiding measurement deviations caused by installation errors. The fixed stand is set on the counter-support test stand, and the table surface is equipped with a high-precision positioning reference surface and multiple adjustable mounting positions, which can be adapted to servo motors, robot servo joints and frameless torque servo systems with different flange sizes and different output shaft diameters, including SCARA robot joints, six-axis industrial robot joints, etc.

[0007] As a further optimization of the present invention, the time grating signal acquisition module is connected to the time grating encoder of the reference positioning module. Its core function is to acquire the position signal output by the time grating encoder in real time and complete signal decoding, filtering and preprocessing. The module is based on an FPGA chip to build a full hardware signal processing link, supports hardware decoding of mainstream communication protocols such as BiSS-C and SSI, and can realize high-speed, zero-delay acquisition of time grating position signals. At the same time, it has a built-in digital filtering unit to eliminate signal noise caused by electromagnetic interference on site and ensure the accuracy of reference position data.

[0008] As a further optimization of the present invention, the servo drive control module is connected to the servo motor / servo joint / frameless torque servo system under test, and mainly includes a sine wave servo driver, a high-speed communication unit, and an encoder signal splitting unit. The sine wave servo driver is used to send motion control commands to the device under test, driving the device under test to move according to a preset trajectory and parameters. The encoder signal splitting unit divides the output signal of the encoder built into the device under test into two paths. One path is connected to the servo driver for servo closed-loop control, and the other path is directly connected to the FPGA chip for position data synchronous acquisition. This completely avoids the delay and distortion problems caused by reading encoder data through driver communication in traditional solutions, and ensures the synchronization of the feedback data of the device under test and the reference data.

[0009] As a further optimization of the present invention, the load simulation module is connected to the output shaft of the test component and is used to provide an adjustable simulated load for the test component to reproduce various working conditions in its actual operation process. The module mainly includes a hysteresis dynamometer, a servo electric cylinder, a torque and speed sensor, and a load controller. The hysteresis dynamometer is used to provide continuously adjustable resistance torque for rotary servo motors, rotary joints, and frameless torque servo systems, and can realize stepless adjustment from no load to rated load. The servo electric cylinder, in conjunction with a high-precision force sensor, is used to provide axial load for linear motion servo joints to simulate actual working conditions such as assembly and handling. The load controller can receive instructions from the main control and data processing modules, automatically adjust the load size and maintain load stability, and support continuous testing of constant load and dynamic testing of variable load.

[0010] As a further optimization of the present invention, the multi-dimensional sensing module is used to collect multi-dimensional operating data during the testing process of the test component, providing data support for the comprehensive evaluation of positioning accuracy and error tracing. It mainly includes a torque and speed sensor, a triaxial vibration sensor, an infrared temperature array sensor, and a noise sensor. The torque and speed sensor is coaxially mounted between the output shaft of the test component and the load simulation module, used to collect the real-time output torque and speed of the test component and analyze the impact of torque pulsation on positioning accuracy. The triaxial vibration sensor is fixed at the shell, output end, and transmission components of the test component, used to collect vibration data in different directions and analyze the interference of mechanical vibration on positioning accuracy. The infrared temperature array sensor is used to monitor the real-time temperature distribution of the stator, bearings, and transmission components of the test component, and analyze the positioning error caused by temperature rise deformation. The noise sensor is used to collect noise data during the testing process to assist in judging the operating status of the test component.

[0011] As a further optimization of the present invention, the main control and data processing module is the core control and data processing hub of the system. It communicates bidirectionally with the time grating signal acquisition module, servo drive control module, load simulation module, and multi-dimensional sensing module, respectively. It adopts an STM32+FPGA dual-core collaborative architecture, in which the STM32 chip serves as the main control core, realizing fully automatic control of the test process, collaborative scheduling of various modules, load adjustment logic, and data interaction between the upper and lower computers; the FPGA chip is responsible for the synchronous parallel acquisition of multi-channel signals, ensuring that the sampling synchronization error of the time grating reference signal, the encoder signal of the device under test, and the multi-dimensional sensing signal is less than 1. .

[0012] As a further optimization of the present invention, the main control and data processing module incorporates a standardized test program library, a data preprocessing unit, and an error tracing and analysis unit. The standardized test program library is constructed based on the national standard GB / T12642-2013 "Performance Specifications and Test Methods for Industrial Robots," and includes a standardized test program with 36 evenly distributed points per circle and reciprocating cycles in both directions. It can automatically execute the entire process of zeroing the tested part, performing 36 step rotations per circle, and conducting multiple reciprocating cycles. It can also automatically execute standardized test procedures for positioning accuracy testing, repeatability accuracy testing, reverse difference testing, and trajectory tracking accuracy testing. The entire testing process requires no manual intervention. Intervention can be completed automatically, and a built-in accuracy index calculation unit can process test data and calculate accuracy indexes according to the statistical methods specified in the aforementioned national standards. The data preprocessing unit uses the SG filtering algorithm to reduce noise in the collected position and torque signals, eliminating the interference of random errors and encoder marking errors on the test results. The error source analysis unit can break down the test process into motion planning, servo drive, motor body, and mechanical transmission stages. By comparing the command data, feedback data, and time encoder reference position data corresponding to each stage, it quantifies the impact of each stage on positioning accuracy and quickly identifies the main sources of positioning accuracy error.

[0013] As a further optimization of the present invention, the main control and data processing module is equipped with a host computer management system developed based on LabVIEW, which can realize fully automatic control of the test process, synchronous acquisition of multi-source data, real-time data processing and in-depth analysis, and at the same time complete the visualization display of test data, automatic generation and output of test reports. Relying on the graphical programming advantages of LabVIEW, the operability and scalability of the system are improved, the consistency of the test process is ensured, and unmanned test management is realized.

[0014] As a further optimization of the present invention, the human-machine interaction module is connected to the main control and data processing module, and adopts the form of combining an industrial touch screen and LabVIEW host computer software. It mainly realizes the functions of test parameter configuration, test process start and stop, real-time display of test data, and automatic generation of test reports. The module has a variety of standardized test templates pre-set, including servo motor test templates, SCARA robot servo joint test templates, six-axis robot joint test templates, frameless torque servo system test templates, etc. The templates are preset with standard test parameters, test points and pass thresholds corresponding to the test parts, which users can directly call to achieve one-click testing. At the same time, it supports user-defined test processes, and can set multi-segment test strokes, multi-point cyclic tests, and variable speed / variable load continuous tests. After the test is completed, the system can automatically generate a standardized test report, which includes raw test data, accuracy index calculation results, error analysis conclusions and pass / fail judgment, and supports export and printing.

[0015] As a further optimization of the present invention, the present invention also provides an automatic testing method based on the above system, which specifically includes the following steps: Step 1: Installation and connection of the device under test (DUT) to the system. Depending on the type of DUT (servo motor / servo joint / frameless torque servo system), fix the DUT on the fixed mounting position of the test bench. Use a coaxial adapter to rigidly connect the output shaft of the DUT to the measuring shaft of the time encoder and the torque input shaft of the load simulation module. Complete the hardware wiring, power supply and communication connection of each module.

[0016] Step 2: Test parameter configuration. Through the LabVIEW host computer interface of the human-computer interaction module, select the test template corresponding to the test device, or customize the test parameters, including test point coordinates, motion speed, acceleration, number of test cycles, load size, sampling frequency, etc. The main control and data processing module automatically generates a standardized test process based on the configured parameters.

[0017] Step 3: System initialization and calibration. After the system is powered on, a full-process self-test is performed, including the communication status detection of each module, the sensor status detection, and the driver status detection. After the self-test passes, the zero-position calibration of the time grid encoder and the encoder built into the device under test is completed, the zero-point calibration of each sensing module is performed, and the no-load debugging of the load simulation module is performed to ensure that the system is in a normal testing state.

[0018] Step 4: Automated test execution. The main control and data processing module sends motion commands to the device under test (DUT) through the servo drive control module, controlling the DUT to move to the target test point according to the preset process. During the movement, the reference position data of the time grating encoder is collected synchronously through the time grating signal acquisition module, the feedback position data of the encoder built into the DUT is collected through the servo drive control module, and torque, vibration, temperature and noise data are collected synchronously through the multi-dimensional sensing module. All data are timestamped and stored in the main control unit.

[0019] Step 5: Cyclic Testing and Data Acquisition. At each target test point, control the device under test to complete a forward and reverse cyclic test. Record the actual position data, motion response data, and multi-dimensional sensor data of each point reached. When performing a single-cycle 36-point standardized test, after controlling the device under test to return to zero, rotate it step by step in 1 / 36 of a revolution. When rotating to the target point, synchronously read the grid reference position and the feedback position of the device under test. After completing 36 forward cycles, perform 36 reverse cyclic tests. The entire forward and reverse cyclic process is executed a total of 5 full cycles until all test processes are completed and all cyclic tests of all test points are completed.

[0020] Step 6: Accuracy Index Calculation and Error Source Tracing. After completing all test actions, the main control and data processing module automatically calculates the core accuracy indicators of the tested part, such as positioning accuracy, repeatability, and reverse difference, according to the collected reference position data and national standards. At the same time, error source tracing analysis is initiated. By comparing motion planning command data, encoder feedback data, time grating reference data, and multi-dimensional sensor data, the influence of each link of motion planning, servo drive, motor body, and mechanical transmission on positioning accuracy is separated and quantified, and the main sources of positioning error are identified.

[0021] Step 7: Test results output. After completing all data analysis, the system automatically saves the original test data and analysis results, generates a standardized test report based on the test results, displays it in real time in the human-computer interaction module, and supports the export, printing, and storage of the report.

[0022] The technical effects and advantages of the automatic testing system for the positioning accuracy of servo motors and servo joints of the present invention are as follows: 1. This invention uses a high-precision time encoder as the position measurement reference and adopts a time encoder based on the principle of "measuring space with time" as the measurement reference. It has the advantages of ultra-high measurement accuracy, strong anti-interference ability and high cost performance. It can maintain stable measurement performance under low-speed heavy load conditions. At the same time, it significantly reduces equipment cost and environmental usage requirements, breaks the scene limitations of high-precision testing equipment, and can meet the full-scenario application needs of laboratory precision testing and production line batch testing.

[0023] 2. This invention, through an FPGA+STM32 dual-core collaborative architecture and encoder signal splitting design, achieves synchronous acquisition of multi-source signals, effectively eliminating system errors caused by sampling delay and significantly improving the accuracy of test results. Simultaneously, based on a LabVIEW-built fully automated control system, coupled with a modular hardware architecture, it achieves compatibility and adaptation for various types of test devices and unmanned, fully automated testing. It can also perform quantitative source analysis of positioning accuracy errors, greatly improving testing efficiency and the practical value of the solution, and providing precise data support for the performance optimization of servo products. Attached Figure Description

[0024] Figure 1 This is a system workflow diagram of the present invention; Figure 2 This is a flowchart of the testing method of the present invention; Figure 3 This is a diagram of the standardized loop test program architecture of the present invention; Figure 4 This is a flowchart of the communication and position acquisition of the tested joint in the LabVIEW program of this invention; Figure 5This is a flowchart of the time encoder communication and position acquisition process in the LabVIEW program of this invention; Figure 6 This is a flowchart of the joint forward motion data acquisition and accuracy calculation in the LabVIEW program of this invention; Figure 7 This is a flowchart of the joint reverse movement data acquisition and accuracy calculation in the LabVIEW program of this invention; Figure 8 This is a schematic diagram of the structure of the test bench of the present invention. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0027] Example 1: Reference Figures 1-2 This embodiment takes the direct-drive servo joint of an industrial SCARA robot as the core test object, covering four core performance test requirements: positioning accuracy, repeatability, reverse difference, and trajectory tracking accuracy. Through the automatic test system proposed in this invention, the entire process of hardware deployment, parameter configuration, initialization calibration, automated testing, index calculation, and report generation is completed. It supplements the implementation details of core technologies, hardware selection parameters, and quantitative test results, providing a directly referable operational standard for the engineering implementation of technical solutions.

[0028] In this embodiment, the main hardware of the test system is mounted on a high-precision platform's support test bench. Leveraging the platform's high flatness and stability, the system's installation accuracy and anti-interference capabilities during operation are ensured. The entire hardware system is coaxially constructed around the SCARA direct-drive servo joint under test. The hardware selection, deployment method, and core parameters of each module are as follows: The reference positioning module, serving as the core of the system's measurement reference, employs a 23-bit absolute circular time-grating encoder. This encoder, based on the principle of spatiotemporal coordinate transformation, measures displacement by measuring space in time, achieving an angular resolution of 0.4 arcseconds and a measurement accuracy of ±0.8 arcseconds, fully meeting the testing reference requirements of ultra-high precision servo joints. The encoder is fixed to a dedicated support on the test bench via a high-precision flange, ensuring stable dimensional and positional tolerances during installation. The coaxial adapter assembly uses a high-precision 45# steel adapter shaft and a double diaphragm coupling, with the coaxiality error of the coupling controlled within 0.01mm. This effectively eliminates installation coaxiality deviations between the SCARA servo joint output shaft and the time-grating encoder measurement shaft, preventing additional measurement deviations introduced by installation errors. The fixed bench has pre-set mounting holes that perfectly match the SCARA joint flange, ensuring repeatable positioning accuracy after multiple disassemblies and reassemblies, while also adapting to the installation requirements of SCARA robot joints of different specifications.

[0029] Furthermore, the time grating signal acquisition module is directly connected to the time grating encoder signal output terminal of the reference positioning module. It uses an EP4CE22E22C8 FPGA chip to build a fully hardware signal acquisition and processing circuit, which supports full hardware decoding of the BiSS-C protocol and has a sampling frequency of up to 20MHz. This enables high-speed, zero-delay acquisition of the time grating encoder position signal. The module also has a built-in second-order Butterworth digital filter unit, which can effectively filter out signal noise caused by electromagnetic interference in the industrial field, ensuring that the output reference position data is stable and accurate.

[0030] Furthermore, the servo drive control module is electrically connected to the tested SCARA direct-drive servo joint. Its core utilizes a high-precision sinusoidal servo driver, perfectly compatible with the SCARA joint's direct-drive torque motor. It features a built-in three-loop control architecture (position loop, speed loop, and current loop), enabling precise motion control commands and stable joint operation according to preset trajectories and parameters. The module's encoder signal splitter unit employs a differential signal splitter circuit, dividing the A, B, and Z phase differential signals from the SCARA joint's built-in encoder into two paths. One path connects to the servo driver for servo closed-loop control, while the other directly connects to the FPGA chip for synchronous position data acquisition. The transmission delay between the two signals can be controlled within 0.5 seconds. Within this scope, the delay and distortion problems caused by reading encoder data through the driver communication interface in the traditional solution are completely solved, ensuring the time synchronization between the feedback data of the device under test and the time grating reference data.

[0031] Furthermore, the load simulation module is coaxially connected to the output shaft of the SCARA joint under test to reproduce various load conditions during actual joint operation. The core module uses a hysteresis dynamometer as the load unit, with a rated torque of [missing information]. Torque adjustment range covers It can achieve stepless adjustment from no-load to rated load, accurately simulating the load conditions of SCARA joints under different operating scenarios; the module is equipped with a 0.1-level high-precision torque and speed sensor, which is coaxially installed between the output shaft of the SCARA joint and the hysteresis dynamometer, and can collect the output torque and speed data during the joint operation in real time; the load controller adopts an STM32 control board, which can receive control commands from the main control and data processing modules, automatically adjust the output load torque of the dynamometer and keep it stable, and supports two modes: constant load continuous test and variable load dynamic test.

[0032] Furthermore, a multi-dimensional sensing module is deployed around the tested SCARA joint to collect multi-dimensional operational data of the joint during testing, providing comprehensive data support for the overall evaluation of positioning accuracy and error tracing. The triaxial vibration sensor uses a piezoelectric accelerometer, fixed to the motor housing and output flange of the SCARA joint, with a sampling frequency set to 10kHz. This allows for accurate acquisition of vibration data in different directions during joint operation, analyzing the interference of mechanical vibration on positioning accuracy. The infrared temperature array sensor uses a 32×32 pixel infrared temperature measurement module, aligned with the stator and bearing of the SCARA joint, to monitor the temperature distribution and rise of the joint's core components in real time, analyzing the positioning error caused by temperature-induced deformation. The noise sensor uses a capacitive sound level meter, deployed at a fixed position next to the test platform to collect noise data during testing, assisting in determining whether the tested joint's operating status is abnormal.

[0033] Furthermore, the main control and data processing module, as the core control and data processing hub of the system, adopts STM32H743 as the main control chip, and forms a dual-core collaborative architecture with the FPGA chip of the time grid signal acquisition module. The two interact with each other through the SPI high-speed bus, with the communication frequency set to 5MHz. The main control chip has 2MB of built-in Flash memory to store standardized test programs and acquired test data, and at the same time, it achieves high-speed communication with the human-machine interaction module through Ethernet. The module incorporates a standardized test program library built according to the national standard GB / T12642-2013 "Performance Specifications and Test Methods for Industrial Robots". It can automatically calculate core indicators such as positioning accuracy, repeatability, and reverse error. It also includes an SG filter data preprocessing unit and an error source analysis algorithm, enabling noise reduction of test data and quantitative analysis of positioning accuracy error sources. The SG filter data preprocessing unit uses a 5-point sliding window and second-order polynomial filtering parameters to smooth and reduce noise in the original position and torque signals. The error source analysis algorithm uses variance decomposition to break down the total positioning error into error components of each stage. By calculating the Pearson correlation coefficient between the data deviation of each stage and the total positioning error, it quantifies the contribution of each stage to the positioning accuracy error, enabling rapid location of error sources. The module is equipped with a host computer control system developed based on LabVIEW, enabling fully automated control and data processing of the entire testing process.

[0034] Furthermore, the human-machine interaction module communicates bidirectionally with the main control and data processing module, adopts a 15.6-inch industrial touch screen, and is equipped with host computer testing software developed based on LabVIEW. The software has built-in test templates for SCARA robot servo joints, and presets standardized processes that comply with national standards, such as 5-point cycle test, forward and reverse reciprocating test, and single-circle 36-point cycle test. It also supports user-defined test parameters, real-time curve display of test data, automatic generation and export of test reports, and has low operation threshold and strong adaptability.

[0035] Based on the above hardware system, this embodiment focuses on the positioning accuracy test of the direct-drive servo joint of a SCARA robot. The specific implementation process is as follows: The first step is to install and connect the joint under test to the system. The SCARA servo joint is fixed to the special mounting base of the test bench on the platform through the flange. The joint output shaft, the time encoder measuring shaft, the torque and speed sensor and the hysteresis dynamometer are rigidly connected coaxially in sequence through the high-precision adapter shaft and the double diaphragm coupling. The hardware wiring, power supply line connection and communication link of each module are completed simultaneously to ensure that the communication of each module is normal.

[0036] The second step is to configure the test parameters. The operator selects the SCARA joint-specific test template through the LabVIEW host computer interface of the human-machine interaction module and completes the test parameter configuration within the template: the test points are set to 5 target angles evenly distributed within the joint stroke, the movement speed is set to 100 r / min, the number of test cycles for each point is set to 30, the load during the test is set to 50% of the joint's rated load, and the data sampling frequency of each module is uniformly set to 10kHz. After the parameter configuration is completed, the main control and data processing modules automatically generate a standardized test procedure that conforms to national standards. The system also supports dynamic testing with variable load. It can be set to increase the load linearly from 0 to the rated load during joint movement, and simultaneously complete the positioning accuracy test of the entire load range, reproducing the variable load conditions in actual joint handling operations.

[0037] The third step is system initialization and calibration. After the system is powered on, it performs a full-process self-test to confirm that the communication status of each module, the operating status of the sensors, and the operating status of the servo driver are all normal. After the self-test is passed, the system automatically completes the zero-position calibration of the time encoder and the encoder built into the joint, the zero-point calibration of the torque sensor and the vibration sensor, and the no-load debugging of the hysteresis dynamometer. After all calibrations are completed, the system enters the test-ready state. During the self-test and calibration process, if faults such as driver overcurrent, sensor no signal, encoder communication abnormality, or load over-limit are detected, the system immediately triggers emergency stop protection, cuts off the power supply to the servo drive and the load module, and displays fault alarm information and troubleshooting guidance on the human-machine interface.

[0038] The fourth step is automated test execution. The main control and data processing module sends motion control commands to the SCARA joint through the servo drive control module, controlling the joint to move sequentially to 5 target test points according to a preset process. Each point completes 30 forward and reverse reciprocating movements. During the joint movement, the FPGA chip synchronously and in parallel collects the reference angle data of the time encoder and the feedback angle data of the joint's built-in encoder. The multi-dimensional sensing module synchronously collects torque, vibration, temperature, and noise data during the joint's operation. All collected data are timestamped and stored in real time to the main control unit. No manual intervention is required throughout the process, realizing unmanned testing.

[0039] The fifth step is the calculation of accuracy indicators and error source analysis. After completing the cyclic testing of all points, the main control and data processing module first uses the built-in SG filtering algorithm to perform noise reduction preprocessing on the collected raw position and torque signals to eliminate the interference of random errors and encoder marking errors. Then, according to the statistical methods specified in the national standard GB / T12642-2013, based on the reference position data collected by the time-grating encoder, it automatically calculates the core accuracy indicators of the tested joint, including positioning accuracy, repeatability, and reverse difference. At the same time, the error source analysis algorithm is activated to break down the test process into motion planning, servo drive, motor body, and mechanical transmission links. By comparing the motion planning command data, encoder feedback data, and time-grating reference data corresponding to each link, combined with the collected torque pulsation, vibration, and temperature rise data, the influence of each link on the positioning accuracy is quantified, and the main error sources causing the positioning accuracy deviation are quickly located.

[0040] The sixth step is test report generation and output. After all data analysis is completed, the system automatically saves the original test data and analysis results, and automatically generates a standardized test report containing test parameters, accuracy index calculation results, error analysis conclusions, and pass / fail determination. The report is displayed in real time on the touch screen and supports export, printing, and local storage in PDF format. The report format and core content comply with the requirements of GB / T12642-2013 "Industrial Robot Performance Specifications and Test Methods" for test reports and can be directly used for product performance testing and compliance declaration.

[0041] The testing system in this embodiment shows that the positioning accuracy test results of the SCARA direct-drive servo joint deviate from the measurement results of the laser tracker by less than ±0.002mm, and the repeatability test deviation is less than ±0.001mm, fully meeting the testing requirements of precision servo joints; the sampling synchronization error between the time grating reference signal and the encoder signal of the device under test can be stably controlled within 1. Within this range, compared to the traditional method of reading data through a driver, the sampling latency is reduced by more than 90%; compared to the traditional manual testing method, the full-process testing time for a single joint is shortened from 120 minutes to 20 minutes, and the testing efficiency is improved by 83%; the error source analysis results match the actual error sources of joint disassembly and testing with a degree of ≥95%, which fully verifies the technical advantages of this invention in terms of testing accuracy, synchronization, automation and scenario adaptability.

[0042] Example 2: Reference Figures 3-8 This embodiment uses a frameless torque servo system as the core test object. Addressing the industry pain point of difficult positioning accuracy testing of frameless torque motors, it utilizes the support test bench architecture and LabVIEW automated control system of this invention to complete the full-process positioning accuracy testing of the frameless torque servo system. The specific implementation method is as follows: The main hardware of the test system in this embodiment is mounted on a horizontal, high-rigidity counterweight test bench. The bench adopts a one-piece cast iron structure, which has high rigidity and vibration resistance, ensuring the reference stability during the installation and testing of the frameless torque motor. The entire system is coaxially built around the frameless torque servo system under test, and the core hardware configuration is as follows: The reference positioning module uses a 23-bit absolute circular grating encoder, which measures displacement by measuring space using time based on the principle of spatiotemporal coordinate transformation. It has an angular resolution of 0.4 arcseconds and a measurement accuracy of ±0.8 arcseconds. The encoder is fixed to the fixed end of the test bench via a high-precision flange. Its measuring axis is coaxially connected to the rotor of the frameless torque motor via a high-rigidity adapter shaft. The coaxial adapter assembly uses a double-diaphragm high-rigidity coupling with a coaxiality error of ≤0.01mm, which can eliminate measurement errors caused by installation coaxiality deviations. The fixed bench is equipped with an adjustable mounting position to adapt to the stator of the frameless torque motor, which can accommodate frameless torque servo systems with different inner diameters and flange sizes.

[0043] The hardware configuration of the time grating signal acquisition module, servo drive control module, load simulation module, multi-dimensional sensing module, and main control and data processing module is consistent with that of Example 1. The servo drive control module is adapted to the permanent magnet synchronous servo driver of the frameless torque motor, which can realize high-precision closed-loop control of the frameless torque motor. The rated torque of the hysteresis dynamometer of the load simulation module is adapted to the rated torque of the frameless torque motor under test, which can realize stepless adjustment from 0 to rated load.

[0044] The LabVIEW host computer software of the human-computer interaction module has a built-in dedicated test template for frameless torque servo systems. The template has a pre-set standardized 36-point test procedure for a single revolution. Specifically, after the motor under test returns to zero, it rotates in 1 / 36 revolution increments. After each rotation to a target point, the reference position data of the time encoder and the feedback data of the motor's built-in encoder are collected simultaneously. After completing 36 cycles of forward rotation, the reverse rotation test is performed. The reverse rotation is performed in 1 / 36 revolution increments to complete 36 reverse cycle tests. The entire forward and reverse reciprocating test is performed in 5 cycles, and no manual intervention is required throughout the process.

[0045] The specific testing procedure for the frameless torque servo system in this embodiment is as follows: Step 1: Installation of the test component: Fix the stator of the frameless torque motor on the adjustable mounting position of the test bench. The motor rotor is rigidly connected to the time encoder measuring shaft, torque and speed sensor and hysteresis dynamometer through a high-precision adapter shaft and coupling, thus completing the hardware wiring and communication connection.

[0046] The second step is parameter configuration: Select the frameless torque servo system test template through the LabVIEW host computer, and configure parameters such as motor rated speed, test load, number of cycle tests, and sampling frequency. The system will automatically generate a standardized 36-point cycle test process.

[0047] The third step is system initialization: After the system is powered on, it completes a full-process self-test, including zero-position calibration of the time encoder and motor encoder, zero-point calibration of each sensor, and no-load debugging of the dynamometer. After the self-test is passed, it enters the test-ready state.

[0048] The fourth step is automated test execution: The system controls the frameless torque motor to rotate 1 / 36 of a turn in the forward direction to complete the forward cycle test of 36 points, and then rotate 1 / 36 of a turn in the reverse direction to complete the reverse cycle test of 36 points. The entire forward and reverse reciprocating process is executed 5 times. During the test, the FPGA synchronously collects the time grid reference position data, motor encoder feedback data, and multi-dimensional sensor data. All data is stored with synchronous timestamps.

[0049] Step 5: Data Processing and Analysis: After completing all loop tests, the system uses the SG filtering algorithm to reduce noise in the raw data. It automatically calculates the core indicators of the frameless torque motor, such as positioning accuracy, repeatability, and reverse difference, according to national standards. At the same time, it performs error source analysis to quantify the impact of each step on positioning accuracy.

[0050] Step 6: Report Output: The system automatically generates a standardized test report, displaying test data, accuracy indicators, and error analysis results, and supports exporting and printing.

[0051] This embodiment completely solves the problems of difficult positioning accuracy testing, unstable installation benchmark, and poor test consistency of frameless torque motors through a high-rigidity support test bench architecture and standardized cyclic testing process. The test results deviate from the laser interferometer calibration value by ≤±1 arcsecond, and the testing efficiency is improved by more than 75% compared with the traditional manual method. This fully verifies the adaptability and technical advantages of this invention to various types of test parts.

[0052] The above embodiments can be implemented in whole or in part by software, hardware, firmware or other arbitrary combinations. When implemented by software, the above embodiments can be implemented in whole or in part in the form of a computer program product.

[0053] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0054] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0055] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0056] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automatic testing system for the positioning accuracy of a servo motor and a servo joint, characterized in that, The entire system hardware is mounted on a high-rigidity test bench, including a reference positioning module, a time grid signal acquisition module, a servo drive control module, a load simulation module, a multi-dimensional sensing module, a main control and data processing module, and a human-machine interaction module. The reference positioning module is based on a high-precision time encoder and is used to provide an absolute position reference for the servo motor, servo joint or frameless torque servo system under test. The measuring axis of the time encoder is rigidly connected to the output axis of the device under test. The time encoder adopts an absolute time encoder displacement sensor, which realizes displacement measurement by measuring "space" with "time" based on the principle of time-space coordinate transformation. The time grating signal acquisition module is connected to the reference positioning module and is used to acquire the position signal output by the time grating encoder in real time, and to complete signal decoding, filtering and preprocessing. The servo drive control module is connected to the servo motor / servo joint under test and is used to send motion control commands to the device under test, while simultaneously collecting real-time feedback data from the encoder built into the device under test. The load simulation module is connected to the output shaft of the device under test and is used to provide an adjustable simulated load for the device under test, reproducing different working conditions such as no-load, rated load, and variable load. The multi-dimensional sensing module is used to collect torque, vibration, temperature and noise data of the test piece during the testing process, providing multi-dimensional data support for positioning accuracy error analysis; The main control and data processing module communicates bidirectionally with the time grid signal acquisition module, servo drive control module, load simulation module, and multi-dimensional sensing module, respectively. It is equipped with a host computer management system developed based on LabVIEW to realize fully automatic control of the test process, synchronous acquisition and fusion analysis of multi-source data, and at the same time complete the calculation of positioning accuracy-related indicators and error tracing. The human-computer interaction module is connected to the main control and data processing module and is used for test parameter configuration, test process start and stop, real-time display of test data and automatic generation of test reports.

2. The automatic positioning accuracy testing system for servo motors and servo joints as described in claim 1, characterized in that, The reference positioning module includes a high-precision time-grating encoder, a coaxial adapter assembly, and a fixed platform. The time-grating encoder uses an absolute time-grating displacement sensor with a resolution better than ±0.5 arcseconds and a measurement accuracy better than ±1 arcsecond. The coaxial adapter assembly includes a corresponding shape adapter plate, a corresponding shape adapter shaft, and a high-rigidity diaphragm coupling to eliminate coaxiality errors between the output shaft of the test piece and the measuring shaft of the time-grating encoder. The fixed platform is set on a counter-support test platform and has a positioning reference surface and an adjustable mounting position to adapt to servo motors, servo joints, and frameless torque servo systems with different flange sizes.

3. The automatic positioning accuracy testing system for servo motors and servo joints as described in claim 1, characterized in that, The time grating signal acquisition module and the servo drive control module adopt an FPGA+STM32 dual-core collaborative architecture. The FPGA chip is used to achieve synchronous parallel acquisition of the time-grid encoder signal and the encoder signal of the device under test. The sampling synchronization error between the two signals is less than 1. Simultaneously, it completes full hardware decoding of the BiSS-C protocol for the time grating signal; the STM32 chip serves as the main control core, used to implement motion control logic, load adjustment logic, and data interaction.

4. The automatic positioning accuracy testing system for a servo motor and servo joint as described in claim 3, characterized in that, The servo drive control module includes a sine wave servo driver, a high-speed communication unit, and an encoder signal splitting unit. The encoder signal splitting unit divides the output signal of the encoder built into the device under test into two paths. One path is connected to the servo driver for servo closed-loop control, and the other path is connected to the FPGA chip for synchronous acquisition of position data, avoiding sampling delay and data distortion caused by the communication rate limitation of traditional drivers.

5. The automatic positioning accuracy testing system for a servo motor and servo joint as described in claim 1, characterized in that, The load simulation module includes a hysteresis dynamometer, a servo electric cylinder, a torque and speed sensor, and a load controller. The hysteresis dynamometer provides continuously adjustable resistance torque to the tested servo motor / servo joint to simulate the load under rotational conditions. The servo electric cylinder, in conjunction with the force sensor, provides axial load to the linear motion servo joint to simulate actual working conditions. The load controller receives instructions from the main control and data processing modules, automatically adjusts the load size, and maintains load stability.

6. The automatic positioning accuracy testing system for a servo motor and servo joint as described in claim 1, characterized in that, The multi-dimensional sensing module includes a torque and speed sensor, a triaxial vibration sensor, an infrared temperature array sensor, and a noise sensor. The torque and speed sensor is coaxially mounted between the output shaft of the test piece and the load simulation module to collect real-time output torque and speed. The triaxial vibration sensor is fixed to the housing and output end of the test piece to collect vibration data. The infrared temperature array sensor is used to monitor the real-time temperature distribution of the stator, bearings, and transmission components of the test piece. The noise sensor is used to collect noise data during the testing process.

7. The automatic positioning accuracy testing system for a servo motor and servo joint as described in claim 1, characterized in that, The main control and data processing module has a built-in standardized test program library, which can automatically execute positioning accuracy test, repeatability accuracy test, reverse difference test, and trajectory tracking accuracy test processes. It has a built-in standardized test program with 36 points evenly distributed in a single circle and reciprocating in both directions. It can perform fully automated operation of the test piece returning to zero, 36 step rotations in a single circle, and multiple cycles of reciprocating in both directions. It has a built-in accuracy index calculation unit, which can complete the processing of test data and the calculation of accuracy index through preset statistical methods. At the same time, it has a built-in error source analysis unit, which can break down the test process into motion planning, servo drive, motor body, and mechanical transmission links. By comparing the position command data, encoder feedback data, and time encoder reference position data of each link, the influence of each link on positioning accuracy can be quantified.

8. The automatic positioning accuracy testing system for a servo motor and servo joint as described in claim 1, characterized in that, The main control and data processing module is also equipped with a data preprocessing unit. The data preprocessing unit uses the SG filtering algorithm to reduce noise in the acquired position and torque signals, eliminating the interference of random errors and encoder marking errors on the test results. At the same time, the timestamps of the data acquired by each channel are synchronously corrected through the pre-calculated system delay to ensure the time consistency of multi-source data.

9. The automatic positioning accuracy testing system for a servo motor and servo joint as described in claim 1, characterized in that, The human-machine interaction module has built-in parameter configuration templates, including servo motor test templates, SCARA robot servo joint test templates, six-axis robot joint test templates, and frameless torque servo system test templates. The templates are preset with standard test parameters, test points, and pass thresholds for the corresponding test parts. It also supports custom test processes, allowing for the setting of multi-segment test strokes, multi-point cyclic tests, and continuous tests with variable speed / variable load. It can also automatically generate standardized test reports, which include test data, accuracy indicators, error analysis results, and pass / fail judgments.

10. An automatic testing method for the positioning accuracy of servo motors and servo joints based on time-grating encoders, characterized in that, The testing system according to any one of claims 1-9 includes the following steps: Step 1: According to the type of the test piece, complete the installation of the servo motor, servo joint or frameless torque servo system under test on the fixed frame of the test bench. Connect the output shaft of the test piece to the time encoder and load simulation module coaxially through the coaxial adapter component, and complete the hardware wiring and communication connection of each module. Step 2: Select the corresponding test template through the LABVIEW host computer interface of the human-computer interaction module, or customize the test parameters, including test points, movement speed, number of cycle tests, load size, and sampling frequency. The main control and data processing module will automatically generate the test process according to the configured parameters. Step 3: The system performs an initialization self-test, completes the zero-position calibration of the time grid encoder and the encoder built into the device under test, the zero-point calibration of each sensing module, and the no-load debugging of the load simulation module. After the self-test passes, it enters the test state. Step 4: The main control and data processing module sends motion commands to the test piece through the servo drive control module, controlling the test piece to move to the target test point according to the preset process. At the same time, the reference position data of the time grating encoder is collected synchronously through the time grating signal acquisition module, the feedback position data of the encoder built into the test piece is collected through the servo drive control module, and torque, vibration and temperature data are collected synchronously through the multi-dimensional sensing module. Step 5: Perform a specified number of reciprocating cycle tests at each test point, and record the actual position data, motion response data, and multi-dimensional sensor data of each point reached. When performing a single-cycle 36-point standardized test, after controlling the device under test to return to zero, rotate it step by step with a step size of 1 / 36 of a cycle. When rotating to the target point, read the grid reference position and the feedback position of the device under test simultaneously. After completing 36 forward cycles, perform 36 reverse cycle tests. The entire forward and reverse reciprocating process is executed a total of 5 full cycles. After completing all point tests, the main control and data processing module automatically calculates the positioning accuracy, repeatability, and reverse difference of the device under test as core indicators. Step 6: The system performs error source analysis. By comparing the reference position data, encoder feedback data, motion planning command data, and multi-dimensional sensor data, the influence of each link of motion planning, servo drive, motor body, and mechanical transmission on positioning accuracy is separated, and the main sources of positioning error are identified. Step 7: After completing all testing processes, the system automatically saves the original test data, generates a standardized test report based on the test results, and displays and outputs it in the human-computer interaction module.

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