Automatic calibration method and system for overturning rigidity of joint module

Abstract

The invention discloses an automatic calibration method and system for the overturning rigidity of a joint module, and relates to the technical field of robot joint performance testing and calibration, and the method comprises the steps: rigidly fixing a tested joint module on a mounting seat, electrifying a sensor, and executing the zero calibration of the sensor; controlling the force application measuring unit to operate according to a preset moment loading spectrum, and synchronously acquiring and recording the reading of the sensor; calculating a net overturning angle and an overturning moment; drawing a torque-angle hysteretic curve, and calculating overturning stiffness values of the detected joint module under forward and reverse loads; and the overturning rigidity parameter obtained through calibration is written into a nonvolatile memory of the tested joint module driver through a communication interface. The sensor and high-frequency data acquisition are adopted, micron-order displacement and tiny angle changes are conveniently captured, high-confidence rigidity parameters and hysteretic curves are obtained accordingly, in addition, the torque loading process and other processes are automatically completed through program control, the single piece calibration time is short, and batch operation is facilitated.

Description

Technical Field

[0001] This invention relates to the field of robot joint performance testing and calibration technology, specifically an automated calibration method and system for the overturning stiffness of a joint module. Background Technology

[0002] Overturning stiffness is a key mechanical performance parameter characterizing the ability of a robot joint module to resist angular displacement of its output end relative to its mounting end when subjected to radial overturning moment. For humanoid robots with high dynamic performance, the overturning stiffness of the joint module directly affects the overall control accuracy, dynamic response speed, and motion stability. Insufficient stiffness may lead to excessive flexural deformation and local vibration in the structure, which in turn can cause low-frequency resonance of the entire machine. In particular, the return clearance near the zero position will seriously affect the continuity of kinematic and dynamic control.

[0003] The joint module is a precision power unit that integrates a driver, motor, reducer, multi-stage bearings, and complex support structure. During mass production, due to factors such as component machining tolerances and assembly stress, it is difficult to guarantee the consistency of overturning stiffness between modules. Therefore, it is necessary to perform precise calibration on a unit-by-unit or batch-by-batch basis and feed the calibration parameters back to the robot's overall control system to achieve optimal motion control.

[0004] Currently, existing methods primarily focus on testing the stiffness or clearance of individual components within the joint (such as reducers and bearings). For example, patent CN118168737A describes a bearing stiffness testing device. However, for the overall overturning stiffness of the joint module as an integrated unit, there is a lack of a clear, efficient, and engineering-applicable calibration method. Existing methods often rely on non-standardized manual testing, which suffers from low efficiency, poor data repeatability, and inability to match production cycles, making it difficult to meet the urgent need for rapid and accurate calibration of joint module performance consistency in large-scale production.

[0005] Based on this, an automated calibration method and system for the overturning stiffness of joint modules is now provided, which can eliminate the drawbacks of existing technical solutions. Summary of the Invention

[0006] The purpose of this invention is to provide an automated calibration method and system for the overturning stiffness of joint modules, so as to solve the problems of low efficiency, poor data repeatability, and inability to match production cycle caused by the reliance on manual testing in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: An automated calibration method for the overturning stiffness of a joint module includes the following steps: Step S1: Rigidly fix the joint module under test to the mounting base through its output flange, connect all sensors to the data acquisition and processing unit, power on and perform sensor zero-position calibration; Step S2: Control the force measurement unit to operate according to the preset torque loading spectrum, and synchronously collect and record the readings of the force sensor and the four displacement sensors; Step S3: Based on the collected raw data, calculate the net overturning angle and overturning moment at each sampling time; Step S4: Plot the torque-angle hysteresis curve with the calculated net overturning angle as the abscissa and the overturning moment as the ordinate. Analyze the torque-angle hysteresis curve to calculate the overturning stiffness value of the tested joint module under positive and negative loads. Step S5: Write the calibrated overturning stiffness parameters into the non-volatile memory of the test joint module driver through the communication interface; Step S6: Install the calibrated joint module under test onto the humanoid robot. The control system of the humanoid robot calls the overturning stiffness parameter of the joint module under test in the motion planning to calculate the compensation torque.

[0008] Furthermore, the specific operation of step S2 according to the preset torque loading spectrum is as follows: starting from zero, gradually loading positively to the module's rated peak torque, then slowly unloading to zero, then gradually loading in the opposite direction to the negative peak torque, then unloading to zero, and finally loading positively again to the rated torque, forming a complete loading and unloading cycle.

[0009] Furthermore, the formula for calculating the net overturning angle in step S3 is as follows: ; ; ; in, The tilt angle of the mounting end. For displacement sensor The reading at the measuring point on the mounting flange. For displacement sensor The reading at the measuring point on the mounting flange. For the mounting flange and Calibration spacing of measuring points The output tilt angle. For displacement sensor The reading at the measuring point on the output flange. For displacement sensor The reading at the measuring point on the output flange. For the output flange and Calibration spacing of measuring points The net overturning angle.

[0010] Furthermore, the formula for calculating the overturning moment in step S3 is as follows: ; in, For overturning moment, For force sensor readings, It is the vertical lever arm from the point of force application to the center of joint rotation.

[0011] Furthermore, the data acquisition frequency in step S3 is not less than 1 kHz.

[0012] Furthermore, in step S4, the hysteresis curve is analyzed by taking the slope of the linear segment of the unloading curve and performing piecewise linear and nonlinear fitting on the data.

[0013] Furthermore, in step S5, the overturning stiffness parameter is either the overturning stiffness value or a fitted higher-order characterization formula.

[0014] An automated calibration system for the overturning stiffness of a joint module, applied to an automated calibration method for the overturning stiffness of a joint module, includes: Mounting bracket, used to mount the joint module under test, providing a high-rigidity reference for the automated calibration system; The force measurement unit includes a force actuator, a force rod, and a force sensor. The force actuator is used to provide controllable linear thrust and tension. The force rod is fixed to the output flange of the measured joint module and is used to convert the linear force of the force actuator into an overturning moment acting on the output end. The force sensor is connected in series between the force actuator and the force application point and is used to measure the applied force value in real time. The displacement measurement unit includes at least four displacement sensors, which are divided into two groups. One group is arranged vertically at the upper and lower symmetrical points of the mounting end flange of the joint module under test, and is used to measure the relative displacement of the mounting end flange under force. The other group is arranged vertically at the upper and lower symmetrical points of the output end flange of the joint module under test, and is used to measure the relative displacement of the output end flange under force. The data acquisition and processing unit is used to control the force application process, synchronously acquire data from force sensors and displacement sensors, and perform calculations, analysis, curve plotting, and result storage.

[0015] Furthermore, the force-applying actuator is any one of a servo electric cylinder, a linear motor, and a high-precision cylinder.

[0016] Furthermore, the force sensor is either a spoke-type or an S-type tension / compression sensor, and the signal from the force sensor is processed by a transmitter and output as a digital signal.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention proposes a solution for overall overturning stiffness calibration of an integrated system, namely a robot joint module. It adopts the differential displacement measurement principle to effectively offset the error introduced by the deformation of the mounting base. Combined with force sensors, displacement sensors and high-frequency data acquisition, it is easy to capture micron-level displacement and minute angle changes, thereby obtaining high-confidence stiffness parameters and hysteresis curves. In addition, the torque loading, data acquisition and calculation analysis processes of this invention are all automatically completed by program control, with short calibration time for a single part, which greatly improves the production testing cycle and facilitates batch operation, showing good application prospects. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the method steps of the present invention.

[0019] Figure 2 This is a schematic diagram of the hysteresis curve of the present invention.

[0020] Figure 3 This is a schematic diagram of the system structure of the present invention.

[0021] Figure 4 This is a schematic diagram of the overall structure of the present invention.

[0022] Figure 5 This is a schematic diagram of the displacement sensor arrangement according to the present invention.

[0023] Figure reference numerals: Mounting base 10, force measurement unit 20, force actuation mechanism 21, force rod 22, force sensor 23, displacement measurement unit 30, data acquisition and processing unit 40, measured joint module 50. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Example 1 In this embodiment, as Figure 1 As shown, an automated calibration method for the overturning stiffness of a joint module includes the following steps: Step S1: The joint module 50 under test is rigidly fixed to the mounting base 10 through its output flange, all sensors are connected to the data acquisition and processing unit 40, power on and perform sensor zero-position calibration. Step S2: Control the force measurement unit 20 to operate according to the preset torque loading spectrum, and synchronously collect and record the readings of the force sensor and the four displacement sensors; Step S3: Based on the collected raw data, calculate the net overturning angle and overturning moment at each sampling time; Step S4: Plot the moment-angle hysteresis curve with the calculated net overturning angle as the abscissa and the overturning moment as the ordinate (a typical hysteresis curve is shown in Figure 1). Figure 2 As shown in the figure, the overturning stiffness value of the tested joint module 50 under positive and negative loads is calculated by analyzing the torque-angle hysteresis curve. Step S5: Write the calibrated overturning stiffness parameter (which can be a simple stiffness value or a fitted second-order / higher-order characterization formula) into a specified address in the non-volatile memory (such as FLASH) of the driver of the tested joint module 50 through a communication interface (such as CAN, RS485). This overturning stiffness parameter can be read in real time by the upper control system of the humanoid robot and used in advanced control algorithms such as feedforward compensation and vibration suppression. Step S6: Install the calibrated test joint module 50 onto the humanoid robot. The humanoid robot's control system calls the overturning stiffness parameters of the test joint module 50 in the motion planning to calculate the compensation torque. In this embodiment, the present invention provides a method for measuring and calibrating the overall overturning stiffness of a robot joint module, filling the technical gap in integrated system-level parameter calibration. It can accurately capture and analyze the torque-angle hysteresis characteristics of the tested joint module 50 within a small angle near the zero position, and can solve the problems of low efficiency and poor consistency of traditional manual or semi-automatic testing methods, meeting the requirements of test cycle time and traceability in industrial production.

[0026] Specifically, the operation in step S2 according to the preset torque loading spectrum is as follows: starting from zero, gradually loading positively to the module's rated peak torque (e.g., +380 N·m), then slowly unloading to zero, then gradually loading in the opposite direction to the negative peak torque (e.g., -380 N·m), then unloading to zero, and finally loading positively again to the rated torque, forming a complete loading and unloading cycle.

[0027] Specifically, the formula for calculating the net overturning angle in step S3 is as follows: ; ; ; in, The tilt angle of the mounting end. For displacement sensor The reading at the measuring point on the mounting flange. For displacement sensor The reading at the measuring point on the mounting flange. For the mounting flange and Calibration spacing of measuring points The output tilt angle. For displacement sensor The reading at the measuring point on the output flange. For displacement sensor The reading at the measuring point on the output flange. For the output flange and Calibration spacing of measuring points The net overturning angle is calculated to eliminate errors caused by minor deformations that may occur in the mounting base 10.

[0028] Specifically, the formula for calculating the overturning moment in step S3 is as follows: ; in, For overturning moment, For force sensor readings, It is the vertical lever arm (constant value) from the point of force application to the center of joint rotation.

[0029] Specifically, the data acquisition frequency in step S3 is no less than 1 kHz.

[0030] Specifically, in step S4, the hysteresis curve is analyzed by taking the slope of the linear segment of the unloading curve and performing piecewise linear and nonlinear fitting on the data.

[0031] Specifically, in step S5, the overturning stiffness parameter is either the overturning stiffness value or a fitted higher-order characterization formula.

[0032] Example 2 The difference from Example 1 is that, as in Example 1, Figures 3-5 As shown, the present invention also provides an automated calibration system for the overturning stiffness of a joint module, applied to an automated calibration method for the overturning stiffness of a joint module as shown in Embodiment 1. The automated calibration system includes: Mounting base 10 is used to securely mount the joint module 50 under test, providing a high-rigidity reference for the automated calibration system. It can be adapted to different models and torque levels of joint modules by changing different specifications of mounting clamps and adapting force arms. The force measurement unit 20 includes a force actuator 21, a force rod 22, and a force sensor 23. The force actuator 21 is used to provide controllable linear thrust and pull. The force rod 22 is fixed to the output flange of the measured joint module 50 and is used to convert the linear force of the force actuator 21 into an overturning moment acting on the output end. The force sensor 23 is connected in series between the force actuator 21 and the force application point and is used to measure the applied force value in real time. The displacement measurement unit 30 includes at least four displacement sensors (e.g., LVDT differential transformer linear displacement sensors), which are divided into two groups, one of which is located in... and The measuring points are arranged vertically at the upper and lower symmetrical points of the mounting flange of the tested joint module 50, and are used to measure the relative displacement of the mounting flange under force. Another set (located at...) and The measuring points are vertically arranged at the upper and lower symmetrical points of the output flange of the measured joint module 50 to measure the relative displacement of the output flange under force. All displacement sensor outputs are modulated and uploaded in the form of digital signals. The data acquisition and processing unit 40 includes an industrial computer (IPC) or embedded controller, a data acquisition card (or directly via RS485 bus), and dedicated control and data processing software, used to control the force application process, synchronously acquire data from the force sensor 23 and the displacement sensor, and perform calculation, analysis, curve plotting, and result storage operations. Specifically, the force-applying actuator 21 adopts any one of a servo electric cylinder, a linear motor, and a high-precision cylinder.

[0033] Specifically, the force sensor 23 is either a spoke-type or an S-type tension / compression sensor, and the signal of the force sensor 23 is processed by the transmitter and output as a digital signal (such as RS485). The knee joint module (tested joint module 50) of a humanoid robot with a peak torque of 380 N·m was used as the calibration object. The specific operation process is as follows; 1. System hardware configuration: Mounting base 10: A welded steel structure platform is used as the mounting base 10. The mounting surface is precision milled. Customized mounting fixtures use high-strength bolts to rigidly lock the flange at the mounting end of the knee joint module. Force measurement unit 20: A servo electric cylinder with a rated thrust of 5kN is selected as the force actuation mechanism 21. The end of the push rod of the servo electric cylinder is connected to a rigid force rod (force rod 22) through an S-type force sensor (range 2kN, accuracy 0.1%). The end of the rigid force rod acts on the lever arm of the output flange. Place; Displacement measurement unit 30: Selects four LVDT sensors (model example: S series) with a range of ±1mm and linearity better than ±0.05%. and Mounted on the reference surface of the mounting fixture, with spacing Displacement sensor and It is mounted on the outer edge of the output flange of the knee joint module via a lightweight bracket, with a spacing of... The sensor signal is output via an RS485 digital transmitter; Data acquisition and processing unit 40: adopts an industrial computer to centrally acquire all sensor data via RS485 bus and control the servo electric cylinder via manual bus; 2. Calibration software process: The software modules are developed using LabVIEW or Python, and the main modules include: Parameter settings interface: Input spacing ,spacing lever arm Set the loading spectrum (e.g., loading rate of 10 N·m / s, peak value of ±380 N·m). Automated testing process: Click Start to drive the electric cylinder to execute the preset torque loading spectrum of "0→+380→0→-380→0→+380" N·m, and simultaneously acquire data at a frequency of 1000Hz from the S-shaped force sensor and four displacement sensors. , , and A total of 5 channels of data were collected, and the torque-angle hysteresis curve was calculated and displayed in real time during the test. curve); Post-processing and analysis: After the test, the software automatically analyzes the data and calculates the average stiffness of the forward and reverse loading segments. The expression is: , ,in, and These are the average stiffnesses of the forward and reverse loading segments, respectively. The average overturning moment, To obtain the mean overturning angle, the least squares method is used to fit the hysteresis curve data into the following formula: (Consider nonlinearity) For overturning moment, The net overturning angle is the goodness of fit. ; Data output and writing: This involves transferring the fitting coefficients. , The test report is saved to the database, and simultaneously, the test report is sent via the CAN debugging interface reserved in the knee joint module. , Write to the specified parameter area of ​​its driver FLASH; 3. Calibration Results and Applications: After the calibrated knee joint module is installed on the humanoid robot, its control system calls the overturning stiffness parameters of the knee joint module in motion planning to calculate the compensation torque, which effectively suppresses the structural elastic vibration in leg movement and improves the stability of single-leg standing and walking.

[0034] In summary, this invention provides an automated calibration method and system for the overturning stiffness of a joint module. Through a sophisticated electromechanical measurement system, a controllable and continuous radial overturning torque is applied to the output end of the tested joint module 50. Simultaneously, high-precision torque values ​​and key displacement changes at the module's input / output ends are acquired. After data processing, the relationship between the overturning angle and the torque is directly calculated, and hysteresis curves are plotted and stiffness parameters are extracted. Ultimately, automated parameter calibration and storage are achieved. The torque loading, data acquisition, and calculation analysis processes are all automatically completed under program control. The calibration time for a single component is short, facilitating batch operations and significantly improving the production testing cycle time.

[0035] 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 technical scope 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 the claims.

Claims

1. An automated calibration method for the overturning stiffness of a joint module, characterized in that, Specifically, the following steps are included: Step S1: The joint module (50) under test is rigidly fixed to the mounting base (10) through its output flange, all sensors are connected to the data acquisition and processing unit (40), power on and perform sensor zero-position calibration; Step S2: Control the force measurement unit (20) to operate according to the preset torque loading spectrum, and synchronously collect and record the readings of the force sensor and the readings of the four displacement sensors; Step S3: Based on the collected raw data, calculate the net overturning angle and overturning moment at each sampling time; Step S4: Using the calculated net overturning angle as the abscissa and the overturning moment as the ordinate, plot the moment-angle hysteresis curve. Analyze the moment-angle hysteresis curve to calculate the overturning stiffness value of the tested joint module (50) under positive and negative loads. Step S5: Write the calibrated overturning stiffness parameters into the non-volatile memory of the driver of the tested joint module (50) through the communication interface; Step S6: Install the calibrated joint module (50) onto the humanoid robot. The control system of the humanoid robot calls the overturning stiffness parameter of the joint module (50) in motion planning to calculate the compensation torque.

2. The automated calibration method for the overturning stiffness of a joint module according to claim 1, characterized in that, The specific operation of step S2, which follows the preset torque loading spectrum, is as follows: starting from zero, gradually loading positively to the module's rated peak torque, then slowly unloading to zero, then gradually loading in the opposite direction to the negative peak torque, then unloading to zero, and finally loading positively again to the rated torque, forming a complete loading and unloading cycle.

3. The automated calibration method for the overturning stiffness of a joint module according to claim 2, characterized in that, The formula for calculating the net overturning angle in step S3 is as follows: ； ； ； in, The tilt angle of the mounting end. For displacement sensor The reading at the measuring point on the mounting flange. For displacement sensor The reading at the measuring point on the mounting flange. For the mounting flange and Calibration spacing of measuring points The output tilt angle. For displacement sensor The reading at the measuring point on the output flange. For displacement sensor The reading at the measuring point on the output flange. For the output flange and Calibration spacing of measuring points The net overturning angle.

4. The automated calibration method for the overturning stiffness of a joint module according to claim 1, characterized in that, The formula for calculating the overturning moment in step S3 is as follows: ； in, For overturning moment, For force sensor readings, It is the vertical lever arm from the point of force application to the center of joint rotation.

5. The automated calibration method for the overturning stiffness of a joint module according to claim 1, characterized in that, The data acquisition frequency in step S3 is no less than 1 kHz.

6. The automated calibration method for the overturning stiffness of a joint module according to claim 1, characterized in that, In step S4, the hysteresis curve is analyzed by taking the slope of the linear segment of the unloading curve and performing piecewise linear and nonlinear fitting on the data.

7. The automated calibration method for the overturning stiffness of a joint module according to claim 1, characterized in that, In step S5, the overturning stiffness parameter is either the overturning stiffness value or a fitted higher-order characterization formula.

8. An automated calibration system for the overturning stiffness of a joint module, applied to the automated calibration method for the overturning stiffness of a joint module as described in any one of claims 1-7, characterized in that, include: Mounting base (10) is used to mount the joint module (50) under test, providing a high-rigidity reference for the automated calibration system; The force measurement unit (20) includes a force actuator (21), a force rod (22), and a force sensor (23). The force actuator (21) is used to provide controllable linear thrust and pull. The force rod (22) is fixed to the output flange of the measured joint module (50) and is used to convert the linear force of the force actuator (21) into an overturning torque acting on the output end. The force sensor (23) is connected in series between the force actuator (21) and the force application point and is used to measure the applied force value in real time. The displacement measurement unit (30) includes at least four displacement sensors, which are divided into two groups. One group is arranged vertically at the upper and lower symmetrical points of the mounting end flange of the joint module (50) under test, and is used to measure the relative displacement of the mounting end flange under force. The other group is arranged vertically at the upper and lower symmetrical points of the output end flange of the joint module (50) under test, and is used to measure the relative displacement of the output end flange under force. The data acquisition and processing unit (40) is used to control the force application process, synchronously acquire data from the force sensor (23) and displacement sensor, and perform calculation, analysis, curve plotting and result storage operations.

9. An automated calibration system for the overturning stiffness of a joint module according to claim 8, characterized in that, The force-applying actuator (21) can be any one of a servo electric cylinder, a linear motor, or a high-precision cylinder.

10. An automated calibration system for the overturning stiffness of a joint module according to claim 8, characterized in that, The force sensor (23) is either a spoke-type or an S-type tension / compression sensor, and the signal of the force sensor (23) is processed by the transmitter and output as a digital signal.

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