Two-dimensional ring plug gauge thread measuring machine based on rotary encoder and thread measuring method

Abstract

The invention designs a two-dimensional ring plug gauge thread measuring machine based on a rotary encoder and a thread measuring method, and belongs to the field of precision measurement. The device is composed of a base, an X-axis displacement structure, a Z-axis displacement structure, a ring plug gauge clamp device and a micrometer structure, a rotary encoder is fixed to the rotation center of a probe lever structure, and displacement is fed back in real time in combination with an X / Z-axis grating ruler. The computer integrally controls the motor rotor, the X / Y / Z axis movement and the rotary encoder through the single-chip microcomputer to construct a closed-loop system. The innovation lies in that the lever structure is optimized, appropriate measuring force is provided for different types of ring plug gauge threads, a Y-axis displacement structure is introduced, rapid positioning of a thread inflection point is achieved, accurate measurement of a rotary encoder is achieved, and the accuracy is further improved by error compensation of a computer host. According to the method, the thread to be measured cannot be damaged, manual crutch searching is not needed, measurement of the contact type rotary encoder is more accurate, the accuracy is further improved through error compensation, and an efficient solution is provided for automatic measurement of the thread of the ring plug gauge.

Description

Technical Field

[0001] The present invention relates to a new type of ring plug gauge thread measuring device, and particularly to the field of thread measuring instruments. Background Art

[0002] As a precision geometric quantity measuring device, the core function of a thread measuring machine is to perform high-precision measurement on the thread to be measured through a contact probe. In the prior art, a spring is usually used to press a lever to make the probe fit the thread to be measured, and a non-contact sensor is used to detect the linear displacement of the lever to achieve thread measurement. Its obvious defects are: it is impossible to precisely control the contact force between the probe and the thread, and it is impossible to achieve an ideal contact state where the pressing force is not too large to cause damage to the thread to be measured and the pressing force is not too small to cause the probe to separate from the thread to be measured; the non-contact linear displacement sensor always maintains a certain distance from the lever structure during the measurement process. The measurement accuracy of this structural design is relatively low. After the displacement change of the probe tip is transmitted from the front arm of the lever through the rotation center to the rear arm of the lever and then the linear displacement of the non-contact sensor is collected, the measurement accuracy will inevitably be lost. Therefore, there is still room for improvement in the measurement accuracy of the current thread measuring machine. Summary of the Invention

[0003] (1) Technical Problems to be Solved

[0004] In view of the problems in the prior art that the probe pressure cannot be adjusted according to the model of the thread to be measured, and the measurement accuracy of the non-contact sensor is not high enough, and there is no error analysis modeling and compensation for the collected thread data, the present invention provides a two-dimensional ring plug gauge thread measuring machine based on a rotary encoder and its thread measuring method by designing a new type of sensor - a lever structure. It solves the problems that the existing ring plug gauge thread measuring machine cannot precisely control the contact force between the probe and the thread and the measurement accuracy will inevitably be lost, and realizes a new method for finding the inflection point in thread measurement and error compensation for the curve of the thread to be measured, and a new method for fitting and calculating the curve of the thread to be measured.

[0005] (2) Technical Solutions

[0006] To solve the above technical problems, the present invention provides a two-dimensional ring plug gauge thread measuring machine based on a rotary encoder and its thread measuring method, which is particularly suitable for rapid and high-precision measurement of ring plug gauge threads of different models. Through the angle change and direction change of the rotary encoder and the rotary encoder direction discrimination unit, it is possible to measure the displacement change of the probe tip during measurement, and it is possible to find the inflection point of the thread to be measured and complete the measurement of the parameters of the thread to be measured more safely in an ideal state where the pressing force is not too large to cause damage to the thread to be measured and the pressing force is not too small to cause the probe to separate from the thread to be measured, and the measurement accuracy is higher.

[0007] The technical solution adopted by the present invention to solve its technical problems is: a two-dimensional ring plug gauge thread measuring machine based on a rotary encoder. The device includes a base, an X-axis movement structure, a Z-axis movement structure, a micrometer structure, a ring plug gauge clamping structure, a rotary encoder direction discrimination unit, a processing circuit single-chip microcomputer, and a computer host;

[0008] Among them, the ring plug gauge clamping structure and the X-axis movement structure are fixed on the base; the Z-axis movement structure is fixed on the X-axis carrier table; the micrometer structure is fixed on the Z-axis carrier table; the rotary encoder direction discrimination unit is connected to the rotary encoder; the computer host is used to write control software programs and store measurement data; the processing circuit single-chip microcomputer is electrically connected to the X-axis servo motor, the Z-axis servo motor, the Y-axis servo motor, the X-axis micro-motion servo motor, and the rotary encoder direction discrimination unit to achieve motion control and information acquisition.

[0009] Preferably, the X-axis movement structure is fixed to the base through the X-axis base; the driving mechanism of the X-axis movement structure is driven by the X-axis servo motor to drive the X-axis carrier table, and drives the Z-axis movement structure to move along the X-axis through the X-axis linear displacement device; the Z-axis movement structure is fixed to the X-axis carrier table through the Z-axis base; the driving mechanism of the Z-axis movement structure is driven by the Z-axis servo motor to drive the Z-axis carrier table, and drives the micrometer structure to move along the Z-axis through the Z-axis linear displacement device.

[0010] Preferably, the Z-axis grating scale cooperates with the Z-axis grating scale reading head fixed on the micrometer base; the X-axis grating scale cooperates with the X-axis grating scale reading head fixed on the sensor bracket; the rotary encoder is fixed on the sensor bracket; the sensor bracket is fixed on the X-axis micro-motion carrier table; the rotation center of the lever structure is fixed on the rotary encoder probe head; the front arm of the lever structure is connected to the extension rod of the micrometer probe; the rear arm of the lever structure cooperates with the counterweight; the lever stop column is fixed on the sensor bracket; the tip of the T-shaped probe is a spherical structure.

[0011] Preferably, the micrometer structure is fixed to the Z-axis carrier table through the micrometer base; the driving mechanism of the micrometer structure includes a Y-axis movement structure and an X-axis micro-motion structure; the Y-axis movement structure is fixed to the micrometer base; the Y-axis movement structure is driven by the Y-axis servo motor to drive the Y-axis carrier table, and drives the X-axis micro-motion linear displacement device to move along the Y-axis through the Y-axis linear displacement device; the X-axis micro-motion structure is fixed to the Y-axis carrier table; the X-axis micro-motion structure is driven by the X-axis micro-motion servo motor to drive the X-axis micro-motion carrier table, and drives the sensor bracket to move along the X-axis through the X-axis micro-motion linear displacement device.

[0012] Preferably, in order to achieve the purpose of accurately measuring the ring plug gauge thread, the main technical solution of the present invention is:

[0013] S1. Equipment debugging: Fix the ring plug gauge to be measured on the ring plug gauge fixture. Determine the lengths of the T-type probe and the micrometer probe extension rod according to the model of the ring plug gauge. Adjust the counterweight of the rear arm of the lever to a reasonable position. Record the angle value k and direction of the rotary encoder through the computer host.

[0014] S2. Coarse positioning of the thread: Drive the X-axis motor to move the micrometer structure along the X-axis, so that the micrometer probe moves directly above the thread to be measured. Drive the Z-axis motor to move the micrometer structure along the Z-axis, so that the micrometer probe contacts the thread to be measured. When the angle value of the rotary encoder changes from k to k / 2, the coarse positioning of the thread is completed, and the Z-axis motor stops moving.

[0015] S3. Automatic inflection point measurement:

[0016] 1. Control the Y-axis stage to move along the Y-axis at a constant speed, and synchronously execute:

[0017] a. Continuously collect the displacement signal of the probe tip through the rotary encoder and the rotary encoder direction discrimination unit, and calculate the real-time displacement value.

[0018] b. Record the absolute position coordinates of the lever rotation center through the grating scale.

[0019] c. Calculate the displacement change rate of the probe tip on the rotary encoder. When the displacement change rate is greater than the preset threshold, it is determined that the thread inflection point area is entered.

[0020] 2. Trigger the fine-tuning mode of the Y-axis stage:

[0021] a. According to the gradient direction of the displacement change rate of the probe tip, control the Y-axis stage to move step by step along the Y-axis until the displacement change rate approaches zero, and lock the inflection point coordinates.

[0022] b. Repeat the above process to obtain at least three sets of inflection point coordinates.

[0023] S4. Precise positioning of the thread: Based on the accurately measured inflection point position, drive the Z-axis motor to move the micrometer structure along the Z-axis, and the movement direction is the angle value k / 2. When the angle value of the rotary encoder is k / 2, the precise positioning of the thread is completed, and the Z-axis motor stops moving.

[0024] S5. Precise measurement of the thread: Record the absolute position coordinates of the lever rotation center through the grating scale. Drive the X-axis micro-motor to move the rotary encoder along the X-axis away from the thread to be measured. Continuously collect the displacement signal of the probe tip through the rotary encoder and the rotary encoder direction discrimination unit, and calculate the real-time displacement value. When the probe tip leaves the thread to be measured, that is, when the angle value of the rotary encoder is k, the measurement of the thread to be measured is completed.

[0025] S6. Data fitting and output: Determine the precise measurement initial point from the inflection point coordinates. The rotary encoder and the rotary encoder direction discrimination unit continuously collect the angle and direction change signals of the lever rotation center. Use the nonlinear least squares solver lsqnonlin in the MATLAB optimization toolbox of the computer to solve the calibration constant of the thread to be measured, complete the error compensation of the fitting curve parameters of the thread to be measured, and output the measurement results of the thread parameters to be measured and the confidence evaluation (judged according to the dispersion of the inflection point coordinates).

[0026] Preferably, the grating ruler determines the absolute position of the lever rotation center. The rotary encoder and the direction discrimination unit collect the rotation angle and direction of the lever structure in real time, dynamically control the fine adjustment of the Y-axis stage through the Y-axis displacement change rate, realize the automatic locking of the thread inflection point, use the nonlinear least squares solver lsqnonlin in the MATLAB optimization toolbox of the computer to solve the calibration constant of the thread to be measured, complete the data fusion of the thread parameters, and output a high-precision thread curve. Brief Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is the overall schematic diagram of a new type of ring plug gauge thread measuring device and its measuring method of the present application;

[0029] Figure 2 It is the schematic diagram of the X-axis movement structure and the Z-axis movement structure of a new type of ring plug gauge thread measuring device and its measuring method of the present application;

[0030] Figure 3 It is the schematic diagram of the micrometer device structure of a new type of ring plug gauge thread measuring device and its measuring method of the present application;

[0031] Figure 4 It is the schematic diagram of the Y-axis movement structure and the X-axis fine movement structure of a new type of ring plug gauge thread measuring device and its measuring method of the present application;

[0032] Figure 5 It is the working principle diagram of the measuring device of a new type of ring plug gauge thread measuring device and its measuring method of the present application;

[0033] Figure 6 It is the schematic diagram of the measuring method principle of a new type of ring plug gauge thread measuring device and its measuring method of the present application; Detailed Embodiments

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0035] The following further elaborates on the embodiments of the present invention with reference to the accompanying drawings.

[0036] As Figure 1 shown, a two-dimensional ring plug gauge thread measuring machine based on a rotary encoder, the device includes a base 1, an X-axis motion structure 2, a Z-axis motion structure 3, a micrometer structure 4, a ring plug gauge clamping structure 5, a rotary encoder direction discrimination unit 6, a processing circuit single-chip microcomputer 7, and a computer host 8;

[0037] Among them, the ring plug gauge clamping structure is fixed to the base 1 together with the X-axis motion structure; the Z-axis motion structure 3 is fixed to the X-axis stage 2-1; the micrometer structure 4 is fixed to the Z-axis stage 3-3; the rotary encoder direction discrimination unit 6 is connected to the rotary encoder 4-6; the computer host 8 is used to write control software programs and store measurement data; the processing circuit single-chip microcomputer 7 is electrically connected to the X-axis servo motor 2-3, the Z-axis servo motor 3-0, the Y-axis servo motor 4-7-2, the X-axis micro-motion servo motor 4-8-0, and the rotary encoder direction discrimination unit 6 to achieve motion control and information acquisition.

[0038] As Figure 2 shown, the X-axis motion structure 2 is fixed to the base 1 through the X-axis base 2-0; the driving mechanism of the X-axis motion structure 2 is driven by the X-axis servo motor 2-3 to drive the X-axis stage 2-1, and drives the Z-axis motion structure 3 to move along the X-axis through the X-axis linear displacement device 2-2; the Z-axis motion structure 3 is fixed to the X-axis stage 2-1 through the Z-axis base 3-4; the driving mechanism of the Z-axis motion structure 3 is driven by the Z-axis servo motor 3-0 to drive the Z-axis stage 3-3, and drives the micrometer structure 4 to move along the Z-axis through the Z-axis linear displacement device 3-2.

[0039] As Figure 3The Z-axis grating scale 3-1 shown is mated with the Z-axis grating scale reading head 4-1 fixed to the micrometer base 4-0; the X-axis grating scale 4-3 is mated with the X-axis grating scale reading head 4-2 fixed to the sensor support 4-11; the rotary encoder 4-6 is fixed to the sensor support 4-11; the sensor support 4-11 is fixed to the X-axis micro-moving stage 4-8-2; the pivot center of the lever structure 4-4 is fixed to the probe head of the rotary encoder 4-6; the front arm of the lever structure 4-4 is connected to the micrometer probe extension rod 4-5; the rear arm of the lever structure 4-4 is mated with the counterweight 4-10; the lever stop post 4-9 is fixed to the sensor support 4-11; the tip of the T-shaped probe 4-12 has a spherical structure.

[0040] As Figure 4 The micrometer structure 4 shown is fixed to the Z-axis stage 3-3 through the micrometer base 4-0; the drive mechanism of the micrometer structure 4 includes a Y-axis movement structure 4-7 and an X-axis micro-movement structure 4-8; the Y-axis movement structure 4-7 is fixed to the micrometer base 4-0; the Y-axis movement structure 4-7 is driven by a Y-axis servo motor 4-7-2 to drive the Y-axis stage 4-7-1, and drives the X-axis micro-moving linear displacement device 4-8-1 to move along the Y-axis through the Y-axis linear displacement device 4-7-0; the X-axis micro-movement structure 4-8 is fixed to the Y-axis stage 4-7-1; the X-axis micro-movement structure 4-8 is driven by an X-axis micro-movement servo motor 4-8-0 to drive the X-axis micro-moving stage 4-8-2, and drives the sensor support 4-11 to move along the X-axis through the X-axis micro-moving linear displacement device 4-8-1.

[0041] As Figure 5 , Figure 6The method for measuring the thread of a ring plug gauge includes the following steps: firstly, debugging the equipment, fixing the ring plug gauge to be measured on the ring plug gauge fixture, determining the length of the extension rod of the T-type probe and the micrometer probe according to the model of the ring plug gauge, adjusting the counterweight block of the lever rear arm to a reasonable position, and recording the angle value k and direction of the rotary encoder through the computer host; performing rough positioning of the thread, driving the X-axis motor to move the micrometer structure along the X-axis, and moving the micrometer probe to the top of the thread to be measured; driving the Z-axis motor to move the micrometer structure along the Z-axis, and making the micrometer probe contact with the thread to be measured, and when the angle value of the rotary encoder changes from k to k / 2, the thread After the coarse positioning is completed, the Z-axis motor stops moving; automatic turning point measurement is performed by controlling the Y-axis stage to move along the Y-axis at a constant speed, synchronously collecting the displacement signals of the rotary encoder and the probe tip of the rotary encoder direction discrimination unit, calculating the real-time displacement value, and recording the absolute position coordinates of the lever rotation center through the grating ruler; calculating the displacement change rate of the probe tip on the rotary encoder, when the displacement change rate is greater than the preset threshold, it is determined to enter the thread turning point area, and according to the gradient direction of the displacement change rate of the probe tip, the Y-axis stage is controlled to move step by step along the Y-axis until the displacement change rate approaches zero. The inflection point coordinates are locked, and the above process is repeated to obtain at least three inflection point coordinates; the thread is precisely positioned, and based on the precisely measured inflection point position, the Z-axis motor is driven to move the micro-measuring structure along the Z-axis, and the movement direction is the angle value k / 2. When the angle value of the rotary encoder is k / 2, the thread is precisely positioned, and the Z-axis motor stops moving; the thread is precisely measured, and the absolute position coordinates of the lever rotation center are recorded by the grating ruler, and the X-axis micro-motor is driven to move the rotary encoder along the X-axis away from the direction of the thread to be measured. The probe tip displacement signal is continuously collected by the rotary encoder and the rotary encoder direction discrimination unit, and the real-time displacement value is calculated. When the probe tip is separated from the thread to be measured, that is, the rotary encoder angle value is k, the thread to be measured is measured. Finally, data fitting and output are performed, and the precise measurement initial point is determined by the inflection point coordinates. The rotary encoder and the rotary encoder direction discrimination unit continuously collect the angle and direction change signals of the lever rotation center. The calibration constant of the thread to be measured is solved by the nonlinear least squares solver lsqnonlin in the MATLAB optimization toolbox through a computer, and the error compensation of the fitting curve parameters of the thread to be measured is completed, and the measurement results of the thread parameters to be measured and the confidence evaluation are output.

[0042] Preferably, the processing circuit single-chip computer has the following functional modules built in: a displacement closed-loop control module based on the grating ruler and the grating ruler reading head; a real-time data acquisition module based on the rotary encoder and the rotary encoder direction determination unit; a turning point positioning algorithm module that automatically triggers the Y-axis stage according to the displacement change rate; and a linear displacement algorithm module that triggers the X / Z-axis stage according to the angle and direction changes of the rotary encoder and the rotary encoder direction determination unit.

[0043] Preferably, the rotary encoder should be installed strictly coaxially with the rotation center of the lever structure to ensure the accuracy of the rotary encoder in measuring the rotation angle and direction of the lever and reduce the coaxial error.

[0044] It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0045] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A two-dimensional ring plug gauge thread measuring machine based on a rotary encoder, characterized in that: It includes a base (1), an X-axis motion structure (2), a Z-axis motion structure (3), a micrometer structure (4), a ring plug gauge clamping structure (5), a rotary encoder direction discrimination unit (6), a processing circuit single-chip microcomputer (7), and a computer host (8); Among them, the ring plug gauge clamping structure (5) and the X-axis motion structure (2) are fixed on the base (1) to achieve the fixation of the thread to be measured and the X-axis motion control; the Z-axis motion structure (3) is fixed on the X-axis stage (2-1) to achieve the Z-axis motion control; the rotary encoder direction discrimination unit (6) is connected to the rotary encoder (4-6) to collect information on the angle and direction changes of the lever structure; the computer host (8) is used to write control software programs and store and analyze measurement data to complete the curve fitting of the thread to be measured; the processing circuit single-chip microcomputer (7) is electrically connected to the X-axis servo motor (2-3), the Z-axis servo motor (3-0), the Y-axis servo motor (4-7-2), the X-axis micro-motion servo motor (4-8-0), and the rotary encoder direction discrimination unit (6) to achieve motion control; the micrometer structure (4) is fixed on the Z-axis stage (3-3) and can complete automatic corner finding, high-precision measurement of the probe rotation angle and direction, and precise control of the measurement force; the measurement method can complete the accurate calculation of the inflection point position, error analysis, modeling, and compensation of the thread curve to be measured.

2. The two-dimensional ring plug gauge thread measuring machine based on a rotary encoder according to claim 1, characterized in that: It includes an X-axis base (2-0), an X-axis stage (2-1), an X-axis linear displacement device (2-2), an X-axis servo motor (2-3), a Z-axis base (3-4), a Z-axis stage (3-3), a Z-axis linear displacement device (3-2), and a Z-axis servo motor (3-0); the X-axis motion structure (2) is fixed to the base (1) through the X-axis base (2-0); the driving mechanism of the X-axis motion structure (2) is that the X-axis servo motor (2-3) drives the X-axis stage (2-1), and drives the Z-axis motion structure (3) to move along the X-axis through the X-axis linear displacement device (2-2); the Z-axis motion structure (3) is fixed to the X-axis stage (2-1) through the Z-axis base (3-4); the driving mechanism of the Z-axis motion structure (3) is that the Z-axis servo motor (3-0) drives the Z-axis stage (3-3), and drives the micrometer structure (4) to move along the Z-axis through the Z-axis linear displacement device (3-2).

3. A two-dimensional ring plug gauge thread measuring machine based on a rotary encoder according to claim 1, characterized in that: It includes a Z-axis grating scale (3-1), a micrometer base (4-0), a Z-axis grating scale reading head (4-1), an X-axis grating scale reading head (4-2), an X-axis grating scale (4-3), a lever structure (4-4), a micrometer probe extension rod (4-5), a rotary encoder (4-6), a lever stop column (4-9), a counterweight (4-10), a sensor bracket (4-11), and a T-shaped probe (4-12); the Z-axis grating scale (3-1) cooperates with the Z-axis grating scale reading head (4-1) fixed on the micrometer base (4-0); the X-axis grating scale (4-3) cooperates with the X-axis grating scale reading head (4-2) fixed on the sensor bracket (4-11); the rotary encoder (4-6) is fixed on the sensor bracket (4-11); the sensor bracket (4-11) is fixed on the X-axis micro-moving stage (4-8-2); the rotation center of the lever structure (4-4) is fixed on the measuring head of the rotary encoder (4-6); the front arm of the lever structure (4-4) is connected to the micrometer probe extension rod (4-5); the rear arm of the lever structure (4-4) cooperates with the counterweight (4-10); the lever stop column (4-9) is fixed on the sensor bracket (4-11); the tip of the T-shaped probe (4-12) is a spherical structure.

4. The micrometer structure of a two-dimensional ring plug gauge thread measuring machine based on a rotary encoder according to claim 3, characterized in that: It includes a micrometer base (4-0), a Y-axis servo motor (4-7-2), a Y-axis stage (4-7-1), a Y-axis linear displacement device (4-7-0), an X-axis micro-moving servo motor (4-8-0), an X-axis micro-moving linear displacement device (4-8-1), and an X-axis micro-moving stage (4-8-2); the micrometer structure (4) is fixed to the Z-axis stage (3-3) through the micrometer base (4-0); the drive mechanism of the micrometer structure (4) includes a Y-axis motion structure (4-7) and an X-axis micro-moving structure (4-8); the Y-axis motion structure (4-7) is fixed to the micrometer base (4-0); the Y-axis motion structure (4-7) drives the Y-axis stage (4-7-1) by the Y-axis servo motor (4-7-2), and drives the X-axis micro-moving linear displacement device (4-8-1) to move along the Y-axis through the Y-axis linear displacement device (4-7-0); the X-axis micro-moving structure (4-8) is fixed to the Y-axis stage (4-7-1); the X-axis micro-moving structure (4-8) drives the X-axis micro-moving stage (4-8-2) by the X-axis micro-moving servo motor (4-8-0), and drives the sensor bracket (4-11) to move along the X-axis through the X-axis micro-moving linear displacement device (4-8-1).

5. A thread measuring method for a two-dimensional ring plug gauge thread measuring machine based on a rotary encoder according to any one of claims 1-4, characterized in that, It includes the following steps: S1. Equipment debugging: Fix the ring plug gauge to be measured on the ring plug gauge fixture, determine the lengths of the T-shaped probe and the micrometer probe extension rod according to the ring plug gauge model, adjust the counterweight on the rear arm of the lever to a reasonable position, and record the angle value k and direction of the rotary encoder through the computer host. S2, thread coarse positioning: drive the X-axis motor to move the micrometer structure along the X-axis, so that the micrometer probe moves to the top of the thread to be measured; drive the Z-axis motor to move the micrometer structure along the Z-axis, so that the micrometer probe contacts the thread to be measured. When the angle value of the rotary encoder changes from k to k / 2, the thread coarse positioning is completed, and the Z-axis motor stops moving; S3, automatic measurement:

1. Control the Y-axis stage to move along the Y-axis at a constant speed and execute synchronously: a. Continuously collect the probe tip displacement signal through the rotary encoder and the rotary encoder direction determination unit to calculate the real-time displacement value; b. Record the absolute position coordinates of the lever rotation center through the grating ruler; c. Calculate the displacement change rate of the probe tip on the rotary encoder. When the displacement change rate is greater than a preset threshold, it is determined that the thread inflection point area has been entered; 2. Trigger the Y-axis stage fine-tuning mode: a. According to the gradient direction of the displacement change rate of the probe tip, control the Y-axis stage to move step by step along the Y-axis until the displacement change rate approaches zero and locks the inflection point coordinates; b. Repeat the above process to obtain at least three inflection point coordinates; S4, precise thread positioning: Based on the precisely measured inflection point position, the Z-axis motor is driven to move the micrometer structure along the Z-axis, and the movement direction is the angle value k / 2. When the rotary encoder angle value is k / 2, the precise thread positioning is completed, and the Z-axis motor stops moving; S5. Precise measurement of threads: The absolute position coordinates of the lever rotation center are recorded by the grating ruler, and the X-axis micro-motor is driven to move the rotary encoder along the X-axis away from the direction of the thread to be measured. The probe tip displacement signal is continuously collected through the rotary encoder and the rotary encoder direction discrimination unit, and the real-time displacement value is calculated. When the probe tip is separated from the thread to be measured, that is, the angle value of the rotary encoder is k, the measurement of the thread to be measured is completed; S6. Data fitting and output: The precise measurement initial point is determined by the inflection point coordinates, and the rotary encoder and the rotary encoder direction discrimination unit continuously collect the angle and direction change signals of the lever rotation center. The calibration constants of the thread to be measured are solved by the nonlinear least squares solver lsqnonlin in the MATLAB optimization toolbox through a computer, and the error compensation of the fitting curve parameters of the thread to be measured is completed. The measurement results of the thread parameters to be measured and the confidence evaluation (determined according to the discreteness of the inflection point coordinates) are output.

6. The measurement method according to claim 5, characterized in that: The Y-axis stage fine-tuning mode described in step 3 adopts a PID control algorithm to dynamically adjust the Y-axis stage movement step size according to the displacement change rate deviation value.

7. The measurement method according to claim 5, wherein: The calibration constant of the thread to be measured in step 6 is calculated by the following formula: Where: A is the confidence level, α is the standard deviation of the inflection point coordinate dispersion, and R is the average curvature radius.

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