Online Measurement Method for Wear Amount of Rolling Contact Surface Based on Line Structured Light

Abstract

The present invention discloses an on-line measurement method for the wear amount of a rolling contact surface based on line structured light, which relates to the technical field of rolling contact surface wear detection. The present invention includes constructing a measurement system for the wear amount of a rolling contact surface based on the principle of line structured light; data acquisition and preprocessing, preprocessing the noise points in the original point cloud; designing a wear amount calculation method, and finally obtaining the rolling contact fatigue wear amount of the specimen surface. The present invention collects the point cloud of the specimen surface through a line structured light sensor installed on a rolling contact fatigue testing machine; adopts the k-dimensional tree nearest neighbor search method to perform neighborhood analysis and statistics point by point, and uses a distance threshold to eliminate the outlier points in the point cloud; according to the obtained point cloud data of the specimen surface, designs a wear amount calculation method for plastic material specimens, and performs angle and temperature compensation on the measured height, so as to accurately calculate the rolling contact fatigue wear amount of the specimen.

Description

Technical Field

[0001] The present invention relates to the technical field of rolling contact surface wear detection, and specifically to an on-line measurement method for the wear amount of a rolling contact surface based on line structured light. Background Technique

[0002] The rolling contact fatigue experiment is a failure verification experiment that simulates the working conditions of bearings, gears, turbines, etc. under rolling contact conditions. It is an important means to evaluate and study the contact fatigue performance of materials under simulated working conditions and obtain the basic design data of mechanical parts. There is friction between the relatively moving parts in mechanical equipment, and excessive wear of the parts caused by improper lubrication will affect the normal operation of the machine. Therefore, it is crucial to study the wear resistance of materials through rolling contact friction and wear experiments.

[0003] The wear amount is an important index for evaluating the wear resistance of materials and controlling the product quality of mechanical parts. The wear amount is often evaluated by the weight wear amount, length wear amount and volume wear amount, and can be obtained by measuring the changes in the weight, length and volume of the parts before and after wear respectively.

[0004] The weighing method is most commonly used to measure the weight wear amount of parts, but using this method requires disassembling the parts to be measured, and it is not easy to monitor the change in the wear amount during the test under continuous test conditions. If the measured object undergoes plastic deformation, the wear state of the target cannot be simply evaluated from the wear weight.

[0005] For obtaining the wear length and volume of parts, the wear amount can be accurately measured by contact measurement methods and non-contact measurement methods.

[0006] As a wear amount measurement method studied earlier by scholars, the contact method has more and more experts tending to study non-contact measurement methods due to its disadvantages such as low measurement efficiency and easy scratching of the surface of the object to be measured.

[0007] J.Furustig et al. used an atomic force microscope (AFM) to measure the surface height before and after wear, and used a repositioning method to calculate the wear depth and distribution on the surface of the steel specimen.

[0008] Nurul et al. used a microscope to observe the worn surface of the specimen in a micro test bench, and measured the surface roughness, plastic deformation and wear amount of the rolling contact surface of the specimen.

[0009] S.Hutt et al. used acoustic emission (AE) technology to measure the surface changes, wear state and micropitting during the gear test process.

[0010] Hu, Ning et al. proposed an in-situ measurement method for bearing wear based on ultrasonic waves, and realized the measurement of the static wear thickness of water-lubricated engineering plastic bearings.

[0011] Peng, Liu, etc. proposed an automatic tool wear monitoring system based on machine vision, which calculates the current wear length of the tool by using the obtained two-dimensional tool image, and the measurement error is below 5.17%.

[0012] Rogério, etc. based on image processing technology, used optical interferometry to compare the surface roughness before and after wear, and mapped the point clouds obtained before and after wear onto a 2D image to calculate the volume wear and mass wear.

[0013] The above non-contact measurement methods mainly adopt physical measurement technologies such as light and sound, precision instrument measurement and image measurement technology. In the rolling contact friction and wear test, what needs to be obtained is not only the total wear amount before and after the test, but also the wear amount values at different cycle numbers during the test, so as to obtain the relative wear change trend of the specimen under different working conditions. The above non-contact measurement methods are not easy to monitor the wear amount and surface topography state of the specimen in the current state during the test operation in real time. In the rolling contact fatigue test, the specimen to be tested is in a rotating operation state. When obtaining the surface data of the specimen, it is necessary to overcome the influence of mechanical vibration and axial jump as much as possible. Therefore, the measurement method needs to meet the requirements of measurement speed and accuracy, have a certain anti-interference ability, and at the same time cannot cause damage to the specimen surface.

[0014] Laser triangulation is a commonly used non-contact measurement method. While obtaining the surface topography of the measured object, it can obtain its three-dimensional coordinates. It has the advantages of fast speed, high accuracy and strong anti-interference ability, and has been widely used in the research of measuring wear amount. Ge, Deng, etc. used laser triangulation to obtain the grinding depth of the weld seam in real time, and associated the obtained data with the robotic arm to optimize the adaptive parameters of the robotic weld grinding.

[0015] Filippo and Lorenzo, etc. scanned the plowshare through a structured 3D scanner, and analyzed and calculated the wear mode and wear volume of the plowshare. Bálint and Christoph, etc. used the equipment based on laser triangulation developed by MEGT to measure the wear change of the inner diameter of the radial shaft seal, and studied the influence of static aging and the viscoelasticity of the sealing material on the clamping force and predicted wear.

[0016] The line structured light method can, under the condition of meeting the above conditions, measure the wear change of the specimen in real time during the test, and at the same time can also obtain the topography change of the specimen surface. Therefore, it is of great significance to study the use of the line structured light method to measure the wear amount of the specimen in the rolling contact fatigue test. Summary of the Invention

[0017] The purpose of the present invention is to provide an on-line measurement method for the wear amount of the rolling contact surface based on line structured light.

[0018] To achieve the above object, the present invention provides the following technical solutions: An online measurement method for the wear amount of a rolling contact surface based on line structured light. The online measurement method for the wear amount of a rolling contact surface based on line structured light at least includes the following steps:

[0019] Construct a measurement system for the wear amount of a rolling contact surface based on the principle of line structured light;

[0020] Data acquisition and preprocessing, obtain complete point cloud data of the specimen surface, and preprocess the noise points in the original point cloud;

[0021] Design a calculation method for the wear amount, and finally obtain the wear amount of the actual weight of the specimen.

[0022] Preferably, the three-dimensional point cloud of the specimen surface formed by the principle of line structured light at least includes the following steps:

[0023] The laser Op emits a laser beam that vertically irradiates the surface to be measured to form a laser line AB. After diffuse reflection, the reflected light is received by the lens f and imaged on the CMOS;

[0024] Let the corresponding imaging point of point O be Oq, then the coordinates of the imaging point P' corresponding to point P on the laser line AB can be calculated through coordinate transformation. Similarly, the coordinate data of each point collected on AB can be obtained;

[0025] When the surface to be measured moves in the X-axis direction, the system continuously records the surface information reflected by the laser each time, thereby forming a three-dimensional point cloud of the specimen surface.

[0026] Preferably, the measurement system for the wear amount of a rolling contact surface at least includes a hardware system, a software system, and a data acquisition system. The hardware system at least includes a loading system, a computer specimen, a servo motor, a motion controller, and a temperature measuring device. The software system at least includes data and algorithm programs;

[0027] The specimen is divided into a main specimen and a companion specimen. The main specimen is the specimen to be tested and the research object. The loading system controls the companion specimen to apply contact stress to the main specimen and rolls in contact with the main specimen during the test;

[0028] The data acquisition system is composed of a line structured light sensor, a PLC, and an industrial computer;

[0029] During the test, the system periodically collects the surface point cloud data of the roller main specimen, and performs online processing and calculation on the obtained initial data through the software system to obtain the wear amount values of the specimen weight under different cycle numbers, and analyzes the relative wear change trend of the specimen.

[0030] Preferably, the point cloud on the surface of the test piece is composed of discrete points on the three coordinates of x, y, and z, where the x-axis is the contour sampling direction, and the fixed interval of the contour points is 16 μm;

[0031] The z-axis is the contour height direction, representing the height value of the contour in the sensor's field of view;

[0032] The y-axis is the linear velocity direction, and the calculation method of the interval Δy is as shown in Equation 1:

[0033]

[0034] v y represents the rotational linear velocity of the test piece, and f s represents the sensor sampling frequency, which is determined by the sensor sampling frequency and the linear velocity of the test piece;

[0035] The linear velocity of the test piece is controlled by the testing machine. When the velocity is constant, setting the sensor sampling frequency to match the velocity can obtain the complete point cloud data of the test piece surface.

[0036] Preferably, the preprocessing of the noise points in the original point cloud includes at least the following steps:

[0037] Based on the statistical filtering method, statistically calculate the average distance between each point on the surface of the test piece and its neighboring points, and determine and remove the noise points according to the distribution characteristics obtained from the statistics;

[0038] The points on the surface of the test piece are approximately subject to a Gaussian distribution, which is determined by the mean and standard deviation, and its probability density function is Equation 2:

[0039]

[0040] In the formula, d i is the average distance between each point on the surface and its neighboring points; μ is the mean of the average distance; and σ is the standard deviation;

[0041] Set the number of points k in each neighborhood, and use the k-d tree to quickly search and traverse each point P i (i = 1, 2,..., n) corresponding to each neighborhood of k points Q i (i = 1, 2,..., k), calculate all P i and the corresponding Q i The distance d i between them is obtained, and the mean μ and standard deviation σ are obtained. Define the decision threshold D for outliers as Equation 3:

[0042]

[0043] In the formula: is the proportionality coefficient;

[0044] Set the distance threshold according to the distribution characteristics obtained by statistics to determine and remove noise points. The effect of outlier removal is related to the number k of selected nearest neighbors and the proportionality coefficient related.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] In the present invention, the point cloud on the surface of the specimen is collected by a line-structured light sensor installed on a rolling contact fatigue testing machine; the k-dimensional tree nearest neighbor search method is used to perform neighborhood analysis and statistics point by point, and the outlier points in the point cloud are removed by using the distance threshold; according to the obtained point cloud data of the specimen surface, a wear amount calculation method for plastic material specimens is designed, and angle and temperature compensation are performed on the measured height, so as to accurately calculate the rolling contact fatigue wear amount of the specimen. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0048] Figure 1 is a schematic diagram of the principle of the line-structured light of the present invention;

[0049] Figure 2 is a schematic diagram of the rolling contact surface wear amount measurement system of the present invention;

[0050] Figure 3 is a structural design drawing of the standard part of the rolling contact fatigue specimen of the present invention;

[0051] Figure 4 is a schematic diagram of the point cloud on the surface of the specimen of the present invention;

[0052] Figure 5 is a schematic diagram of the comparison of point cloud denoising of the present invention;

[0053] Figure 6 is a schematic diagram of the wear amount calculation model (Y-Z coordinates) of the present invention;

[0054] Figure 7 is a schematic diagram of the wear amount calculation model (X-Y coordinates) of the present invention;

[0055] Figure 8 is a schematic diagram of the surface adhesion condition (X-Y-Z coordinates) of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0056] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0057] In order to analyze the wear performance of gear plastic material specimens under different PV value working conditions, an on-line detection method for the wear amount of rolling contact surfaces based on line structured light is proposed, and an on-line measurement and analysis system is constructed.

[0058] Measurement System Design

[0059] The surface data of the test specimen is obtained by a line structured light sensor, and its measurement principle is as Figure 1 shown. The laser O p emits a laser beam that vertically irradiates the surface to be measured to form a laser line AB. After diffuse reflection, the reflected light is received by the lens f and imaged on the CMOS. Let the corresponding imaging point of point O be O q . Then, the coordinates of the imaging point P' corresponding to point P on the laser line AB can be calculated through coordinate transformation. Similarly, the coordinate data of each point collected on AB can be obtained. When the surface to be measured moves in the X-axis direction, the system continuously records the surface information reflected by the laser each time, thereby forming a three-dimensional point cloud of the specimen surface.

[0060] Measurement Scheme Design

[0061] Based on the above principle, a rolling contact surface wear amount measurement system as Figure 2 shown is constructed. In the hardware system, the rolling contact fatigue test system consists of a specimen, a servo motor, a motion controller, a temperature measuring device, etc. The specimen is divided into a main specimen and a companion specimen. The main specimen is the test specimen and the research object. The loading system controls the companion specimen to apply contact stress to the main specimen and rolls in contact with the main specimen during the test. The data acquisition system consists of line structured light sensor components. During the test, the system periodically collects the surface point cloud data of the roller main specimen, and online processes and calculates the obtained initial data through the software system to obtain the wear amount values of the specimen weight under different cycle numbers, and analyzes the relative wear change trend of the specimen.

[0062] Since in the rolling contact fatigue test, the specimen is in a rotating and rolling state when being measured, the surface height of the specimen decreases as the wear test progresses, and its surface height changes slightly. If one wants to observe the wear amount change of the specimen under a certain number of cycles in the test, the selected line structured light sensor needs to have high precision in the Z direction and also meet the requirements of the acquisition rate and resolution.

[0063] The specific parameters of the line structured light sensor used in the present invention are shown in Table 1. The test was carried out on the rolling contact fatigue testing machine CQHH-RCF-A independently developed by the research group. According to YB / T 5345-2014 "Rolling Contact Fatigue Test Method", the contact surface width of the main specimen was processed and set to 5 mm, and the shape of the rolling contact fatigue standard specimen is as Figure 3 shown. It should be noted that in different embodiments, the line structured light sensor can be of different models.

[0064] Table 1

[0065]

[0066] Data Acquisition and Preprocessing

[0067] Partial point cloud on the surface of the main specimen is as Figure 4 shown, which is composed of discrete points on the x, y, and z coordinate axes. Among them, the x-axis is the contour sampling direction, and the fixed interval of the contour points is 16 μm; the z-axis is the contour height direction, representing the height value of the contour in the sensor's field of view; the y-axis is the linear velocity direction. The calculation method of the interval Δy is as shown in Equation 1:

[0068]

[0069] v y represents the rotational linear velocity of the specimen, and f s represents the sensor sampling frequency, which is determined by the sensor sampling frequency and the specimen linear velocity.

[0070] The specimen linear velocity is controlled by the testing machine. When the velocity is constant, by setting the sensor sampling frequency to match the velocity, the complete point cloud data of the specimen surface can be obtained.

[0071] When using the sensor to collect the specimen surface data, due to the platform vibration caused by the testing machine environment during the test, the influence of dust in the air and other external factors, there are some outlier points in the obtained specimen surface point cloud that do not originally belong to the contact surface. These points deviate from the original point cloud by a large distance, which will affect the subsequent analysis of the relative wear change trend of the specimen and the calculation of the specimen wear amount. Therefore, it is necessary to preprocess the noise points in the original point cloud first.

[0072] Based on the statistical filtering method, the present invention statistically calculates the average distance between each point on the specimen surface point cloud and its neighboring points, and determines and removes the noise points according to the distribution characteristics obtained from the statistics. The points on the specimen surface are approximately subject to a Gaussian distribution, and the Gaussian distribution is determined by the mean and standard deviation. Its probability density function is as shown in Equation 2:

[0073]

[0074] In the formula, d iis the average distance between each point on the surface and its neighboring points; μ is the mean of the average distances; and σ is the standard deviation.

[0075] Set the number k of points in each neighborhood, and use the k-d tree to quickly retrieve and traverse each point P of the complete contour i For the k points Q in each corresponding neighborhood of (i = 1, 2, …, n) i (i = 1, 2, …, k), calculate all P i and the corresponding Q i The distance d between them i , and obtain the mean μ and the standard deviation σ, and define the determination threshold D of the outlier as shown in Equation 3:

[0076]

[0077] In the formula: is the proportionality coefficient. Set the distance threshold to determine and remove the noise points according to the distribution characteristics obtained by statistics. The outlier removal effect is related to the number k of the selected neighboring points and the proportionality coefficient is related, and the result is as Figure 5 shown;

[0078] Design of the wear amount calculation method

[0079] In Figure 6 , the three arc lines from the outside to the inside respectively represent the surface of the specimen before wear, the surface after wear and the step. The line structured light sensor is fixed above the main specimen to obtain the change in the vertical direction of the height of point P. Let the center of the specimen be point O, the distance H along the radius direction between the surface of the specimen before wear and the step is known, and the radius R of the specimen before wear is known. Figure 7 In, the surface width X before wear is known. According to the above known conditions, the volume S of the cuboid after straightening the circular ring volume between the surface of the specimen before wear and the step can be calculated by Equation 4, S = 2πRHX;

[0080] After the surface of the test piece is worn, the sensor measures the height change Δh of PA in the vertical direction of the surface before and after wear. However, in the calculation model, the change amount r in the radial direction of the test piece surface after wear needs to be obtained. During the test, the system controls the mating test piece to apply contact stress to the main test piece. As the wear amount increases, the position of the mating test piece approaches the main test piece, while the position of the main test piece remains unchanged. At the same time, the measurement angle and position of the sensor remain unchanged. Given the known angle ∠α between the perpendicular line at the measurement position and OP, the distance r between PB can be obtained through angle relationship compensation conversion. In addition, considering that when the sensor collects data on the surface of the test piece during the test, the test piece undergoes thermal expansion due to friction and machine influence, resulting in an increase in the measured height by the sensor. Temperature compensation needs to be performed on the measured height. Let the height increase of the test piece due to thermal expansion be h. Considering that the test piece will undergo plastic deformation during the test and the width of the contact surface of the test piece will change, the width of the test piece surface after wear is X'. Then, based on the above conditions, the wear volume of the test piece can be directly calculated. From Equation 5, The wear volume S1 of the test piece is calculated by calculation method 1;

[0081] The wear volume of the test piece can also be calculated indirectly by subtracting the remaining volume after wear from the total volume S before wear. From Equation 6, The wear volume S2 of the test piece is calculated by calculation method 2;

[0082] Theoretically, the calculation results of the two methods S1 and S2 are the same. However, in actual calculation, it is necessary to consider the phenomenon of dust accumulation on the surface of the test piece during the test, such as Figure 8 shown. More or less attachments will be generated on the surface of the test piece during the test, which will affect the acquisition of the height value of the test piece surface, resulting in calculation errors. The accumulation of surface attachments will increase the measured height. Let the increased height be h + , then the theoretical calculated value S1 is greater than the actual calculated result S1' affected by the attachments, as shown in Equation 7:

[0083]

[0084] The theoretical calculated value S2 is less than the actual calculated result S2', as shown in Equation 8:

[0085]

[0086] As known above, the dust accumulation on the surface will make calculation method 1 smaller and calculation method 2 larger. Considering the errors brought by the surface attachments to the two calculation methods, the wear amount calculation method adopted in this paper is as shown in Equation 9:

[0087] S3 = (S1 + S2) / 2

[0088] Take the average of the calculation results of the two wear volumes. After obtaining the wear volume S′ of the specimen, according to the density value of the specimen material, it can be calculated through Equation 10:

[0089] m w = ρ·S3

[0090] Finally, the wear amount of the actual weight of the specimen is obtained.

[0091] The experimental results show that the average relative error of the measured wear amount of the specimen is 6.31%, which meets the requirements of wear amount detection accuracy. This system can estimate the wear process of the specimen online, observe the change of the specimen surface morphology, and provide a basis for analyzing the wear change process of plastic gear materials under different experimental conditions.

[0092] To achieve online measurement of the wear amount, 5 groups of experiments were carried out according to the test conditions in Table 2. Each group of experiments only carried out 50,000 cycles. After every 5,000 cycles, the machine automatically reduced the speed to 10 r / min and then recorded the surface data of the specimen. The thermal compensation value corresponding to different temperatures within a certain temperature range was determined by the height difference between the fully cooled surface height and the height after heating obtained from the previous experiments 1 and 2. During the test process, the surface height of the specimen was measured online and the wear amount of the specimen was calculated. The comparison between the calculation results and the true wear value is shown in Table 3.

[0093]

[0094] Table 2 Test parameters

[0095]

[0096] Table 3 Data comparison

[0097] The data comparison between the true wear value obtained by weighing and the calculated value after thermal compensation in Table 3 verifies the accuracy of the wear amount calculation method proposed in this paper. The average relative error is 6.31%, and the online measurement of the wear amount during the rolling contact fatigue experiment is realized.

[0098] The method for measuring the wear amount of the rolling contact surface based on line structured light proposed by the present invention can perform online measurement of the surface wear amount of plastic specimens, analyze the relative wear change of the specimen surface, and make up for the deficiencies of the existing rolling contact fatigue testing machine. From the overall test results, it shows that this method can accurately calculate the wear amount value of the specimen during the test process in real time, monitor the relative wear change amount during the wear process of the specimen, and meet the requirements of wear amount measurement in the rolling contact fatigue test. By online measuring the wear change process of the specimen surface, it provides a new test reference and data support for studying the characteristics and wear performance of plastic materials.

[0099] However, for the proposed method of calculating the wear amount of plastic specimens, the accuracy needs to be further improved. The errors are mainly caused by the following aspects: 1. There is plastic deformation caused by non-wear reasons and extrusion in the experiment of plastic specimens; 2. The plastic material specimens are greatly affected by temperature; 3. Dust will accumulate on the surface of POM materials during the experiment, affecting the height measurement value.

[0100] In future research, we will use this method to further explore the influence of PV value on the wear of POM and different plastic materials of gears, expand the experimental data, and obtain the wear curves of different plastic gear materials under different PV values. Moreover, we will design a three-dimensional point cloud measurement method for the rolling contact fatigue test of plastic gears, use line-scanning laser to obtain the gear profile and restore it to the gear tooth profile, and finally obtain the change of the wear amount of plastic gears under the rolling contact fatigue test.

[0101] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. An on-line measurement method for the wear amount of a rolling contact surface based on line structured light, characterized in that: At least the following steps are included: Construct a rolling contact surface wear measurement system based on the principle of line structured light; Data acquisition and preprocessing: obtain complete specimen surface point cloud data and preprocess the noise points in the original point cloud; Design a wear calculation method and finally obtain the rolling contact fatigue wear of the specimen; The wear calculation method is designed as follows: The three arc lines from outside to inside represent the surface before wear, the surface after wear and the step of the specimen respectively; The line structured light sensor is fixed above the main specimen to obtain the vertical change of the height of point P. Assume that the center of the specimen is point O, the distance H along the radial direction between the unworn specimen surface and the step is known, the radius R of the unworn specimen is known, and the surface width X is known. Based on the above known conditions, the volume of the circular ring between the unworn specimen surface and the step can be calculated by formula 4, S=2πRHX, and the volume of the rectangular parallelepiped after the straightening transformation is obtained; After the specimen surface is worn, the sensor measures the height change Δh of the PA in the vertical direction before and after the wear. However, in the calculation model, it is necessary to obtain the change r along the radial direction of the specimen surface after the wear. During the test, the system controls the companion specimen to apply contact stress to the main specimen. As the amount of wear increases, the position of the companion specimen moves closer to the main specimen, and the position of the main specimen remains unchanged. At the same time, the sensor measurement angle and position remain unchanged. If the angle ∠α between the vertical line at the measurement position and OP is known, the distance r between PB can be obtained through angle relationship compensation conversion; In addition, considering that when the sensor collects the data on the surface of the test piece during the test, the test piece undergoes thermal expansion due to friction and machine influence, resulting in an increase in the measured height of the sensor, temperature compensation for the measured height is required. Let the height increase of the test piece due to thermal expansion be h. Considering that the test piece will undergo plastic deformation during the test and the width of the contact surface of the test piece will change, the surface width of the test piece after wear is X'. Then, based on the above conditions, the wear volume of the test piece can be directly calculated. From Equation 5, the wear volume S1 of the test piece is calculated by calculation method 1 of The wear volume of the specimen can also be calculated indirectly by subtracting the remaining volume after wear from the total volume S before wear. According to Equation 6, the wear volume S2 of the specimen is calculated by Calculation Method 2; Theoretically, the calculation results of the S1 and S2 methods are the same, but in actual calculation, it is necessary to take into account the phenomenon of dust accumulation on the specimen surface during the test. More or less attachments will be generated on the specimen surface during the test, which will affect the acquisition of the height value of the specimen surface, thus causing calculation errors. The accumulation of surface attachments will increase the measured height. Let the increased height be h + , then the theoretical calculated value S1 is greater than the actual calculated result S'1 affected by the attachments, as shown in Equation 7: The theoretical calculated value S2 is smaller than the actual calculated result S′2, as shown in Formula 8: As mentioned above, the dust accumulation on the surface will make the calculation method 1 smaller and the calculation method 2 larger. Considering the errors caused by the surface attachments to the two calculation methods, the wear calculation method adopted in this paper is shown in formula 9: S3=(S1+S2) / 2 The calculation results of the two wear volumes are averaged to obtain the wear volume S3 of the specimen. According to the density value of the specimen material, it can be calculated by formula 10: m w = ρ·S3 Finally, the actual weight of the specimen is obtained.

2. The online measurement method for the wear amount of a rolling contact surface based on line structured light according to claim 1, wherein: The three-dimensional point cloud of the specimen surface is constructed by the line structured light principle, which includes at least the following steps: The laser Op emits a laser beam which is vertically irradiated on the surface to be measured to form a laser line AB. After diffuse reflection, AB forms a reflected light which is received by the lens f and then forms an image on the CMOS. Assuming the corresponding image of point O is Oq, the coordinates of the imaging point P' corresponding to point P on the laser line AB can be calculated through coordinate transformation. Similarly, the coordinate data of each point collected on AB can be obtained; When the surface to be tested moves along the X-axis direction, the system continuously records the surface information reflected by the laser each time, thereby forming a three-dimensional point cloud of the specimen surface.

3. The online measurement method for the wear amount of a rolling contact surface based on line structured light according to claim 1, characterized in that: The rolling contact surface wear measurement system at least includes a hardware system, a software system, and a data acquisition system. The hardware system at least includes a loading system, a computer specimen, a servo motor, a motion controller, and a temperature measurement device. The software system at least includes data and algorithm programs; The specimen is divided into a main specimen and a companion specimen. The main specimen is the specimen to be tested and the research object. The companion specimen is controlled by the loading system to apply contact stress to the main specimen and makes rolling contact with the main specimen during the test; The data acquisition system consists of a line structured light sensor, a PLC, and an industrial control computer.

4. The online measurement method for the wear amount of a rolling contact surface based on line structured light according to claim 1, characterized in that: The point cloud on the specimen surface is composed of discrete points on the three coordinates of x, y, and z. Among them, the x-axis is the contour sampling direction, and the fixed interval of the contour points is 16 μm; The z-axis is the contour height direction, representing the height value of the contour within the sensor's field of view; The y-axis is the linear velocity direction, and the calculation method of the interval Δy is as shown in Equation 1: v y represents the rotational linear velocity of the test piece, f s represents the sensor sampling frequency, which is determined by the sensor sampling frequency and the linear velocity of the test piece; The linear velocity of the specimen is controlled by the testing machine. When the velocity is constant, setting the sensor sampling frequency to match the velocity can obtain the complete point cloud data of the specimen surface.

5. The on-line measurement method for the wear amount of a rolling contact surface based on line structured light according to claim 4, characterized in that: The preprocessing of the noise points in the original point cloud at least includes the following steps: Based on the statistical filtering method, the average distance between each point on the specimen surface point cloud and its neighboring points is statistically calculated; The distribution of points on the specimen surface approximately follows a Gaussian distribution. The Gaussian distribution is determined by the mean and standard deviation, and its probability density function is Equation 2: where d i is the average distance between each point on the surface and its neighboring points; μ is the mean of the average distances; and σ is the standard deviation; Set the number of points \(k\) in each neighborhood, and use the \(k\)-dtree to quickly retrieve and traverse each point \(P\) of the complete contour i For each of the \(k\) points \(Q\) in the corresponding neighborhood of \((i = 1, 2, \ldots, n)\) i (i = 1, 2, \ldots, k), calculate all \(P\) i and the corresponding \(Q\) i The distance \(d\) between them i , and obtain the mean \(\mu\) and the standard deviation \(\sigma\). Define the outlier determination threshold \(D\) as Equation 3: In the formula: is the proportionality coefficient; Set a distance threshold according to the distribution characteristics obtained from statistics to determine and remove noise points. The effect of outlier removal is related to the number k of selected nearest neighbors and the proportionality coefficient related.

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