Cylindrical roller trajectory tracking method and device

Abstract

The invention discloses a cylindrical roller trajectory tracking method and device, and the cylindrical roller trajectory tracking method comprises the following steps: obtaining an actual measurement displacement sequence of a key point on the end surface of a roller under a global coordinate system based on a multi-reference matching digital image correlation method; drawing a key point displacement curve about key points and time according to the actually measured displacement sequence; judging the motion state of a roller according to the shape characteristics of the key point displacement curve, dividing a smooth part in the key point displacement curve into a rolling area, and dividing a part with jumping or sharp points into a sliding area; calculating the actual revolution angular velocity and the actual rotation angular velocity of the roller based on the actually measured displacement sequence corresponding to the sliding area; according to the method and the device, the image matching precision can be improved, meanwhile, the rolling and sliding components of the roller are accurately distinguished, the precision of the track of the cylindrical roller is improved, and high-precision and visual experimental data are provided for existing dynamics and tribology models.

Description

Technical Field

[0001] This invention relates to the field of bearing testing technology, specifically to a method and apparatus for tracking the trajectory of cylindrical rollers. Background Technology

[0002] Cylindrical roller bearings are key basic components in mechanical equipment, widely used in high-end equipment fields such as wind turbine main shafts, high-speed railways, heavy machine tools, and aero engines. Their performance directly affects the precision, efficiency, reliability, and lifespan of the entire equipment. In these bearings, the ideal state between the rollers and the raceways of the raceways is pure rolling. However, due to factors such as machining errors, loads, and rotational speeds, contact and friction occur between the rollers and the guide flanges. The motion state of this contact area is very complex, typically a combination of rolling and sliding.

[0003] Traditional methods for studying the rolling slip state of bearing rollers have significant limitations. Researchers primarily analyze the internal motion state of bearings through theoretical modeling, indirect measurement, and electrical methods. Theoretical modeling is based on complex mathematical models built from elastohydrodynamic lubrication theory or dynamics theory. However, these models require numerous assumptions and struggle to accurately simulate real boundary conditions and complex transient operating conditions. Indirect measurement involves measuring the bearing's temperature rise, vibration, or torque to indirectly infer the internal friction state. This method cannot directly observe and quantify the actual roller motion, has low resolution, and is easily affected by various factors. Electrical methods involve applying electricity to the rollers and determining contact by measuring the continuity of the circuit. This method can interfere with the system and cannot provide continuous, full-field motion information. A common limitation of these traditional methods is that they cannot directly and accurately capture and quantify the actual, instantaneous motion trajectory and rolling slip details of the rollers inside the bearing, resulting in a lack of reliable experimental verification for theoretical research and a lack of precise data support for design optimization.

[0004] Digital Image Correlation (DIC) is an advanced optical non-contact full-field deformation and motion measurement technology. It tracks the changes in random speckle patterns on an object's surface before and after deformation, and uses correlation algorithms to accurately calculate the displacement and strain fields of the object's surface. DIC technology effectively overcomes the shortcomings of traditional methods: non-contact detection does not interfere with the normal operation of the bearing. Full-field measurement can simultaneously obtain motion data from all points on the roller end face, and the macroscopic displacement measurement accuracy of the DIC system can reach the micrometer level. Therefore, standard DIC can be applied to the motion detection of the roller end faces of high-speed rotating cylindrical roller bearings. However, conventional detection methods have two problems: (1) The sliding state of the roller is ignored, resulting in low accuracy of the tracked roller trajectory.

[0005] (2) Due to the continuous high-speed rotation of the roller, the speckle pattern on its end face will rapidly undergo huge angular changes in the camera's field of view. The standard DIC method relies on a fixed initial image as a reference. When the similarity between the subsequent image and the initial reference image drops sharply due to the excessive rotation angle of the roller, the DIC's correlation matching algorithm will suffer a sharp drop in accuracy or even fail completely due to image mismatch.

[0006] The aforementioned problems prevent standard DIC technology from achieving continuous and accurate tracking of the roller's full-cycle motion trajectory. Therefore, it is necessary to design a cylindrical roller trajectory tracking method and device to address these issues. Summary of the Invention

[0007] The purpose of this invention is to propose a method and apparatus for tracking cylindrical roller trajectories. This method and apparatus can improve the accuracy of image matching, accurately distinguish the rolling and sliding components of the roller, improve the accuracy of the cylindrical roller trajectory, and provide high-precision and visualized experimental data for existing dynamic and tribological models.

[0008] The technical solution adopted in this invention is a cylindrical roller trajectory tracking method, comprising the following steps: Based on the digital image correlation method of multi-reference matching, the measured displacement sequence of key points on the roller end face in the global coordinate system is obtained; Based on the measured displacement sequence, key point displacement curves with respect to time are plotted. The motion state of the roller is determined based on the shape characteristics of the key point displacement curve, and the smooth part of the key point displacement curve is divided into the rolling zone, and the part with jumping or sharp points is divided into the sliding zone. Based on the measured displacement sequence corresponding to the sliding zone, the actual revolution angular velocity and actual rotation angular velocity of the roller are calculated. By substituting the actual revolution angular velocity and the actual rotation angular velocity into the roller kinematic trajectory model, the roller motion trajectory under actual rolling and sliding conditions of the bearing is obtained.

[0009] As a preferred approach, the digital image correlation method based on multi-reference matching includes the following calculation process: The speckle region on the roller end face is divided into multiple sub-regions, and the coordinate mapping relationship between the sub-regions between the reference image and the deformed image is established through shape functions; A function is defined to measure the similarity between the reference sub-region and the transformed candidate sub-region. The sub-region matching is achieved by finding the extreme value of the correlation coefficient through a search algorithm.

[0010] As a preferred approach, the baseline of the reference image is dynamically updated during the matching process.

[0011] As a preferred approach, firstly, a threshold for the relative rotation angle of the image or a threshold for the bearing rotation time is preset, and during the process of dynamically updating the reference image benchmark: In real time, determine whether the relative rotation angle between the current deformed image and the current reference image during image matching is greater than the relative rotation angle threshold of the images; or In real time, determine whether the difference between the bearing rotation time of the current deformed image and the current reference image during the image matching process is greater than the bearing rotation time threshold. If so, the image of the current or subsequent frame is updated to a new reference image, and matching with subsequent images continues based on the new reference image.

[0012] As a preferred method, the steps for calculating the actual revolution angular velocity and actual rotation angular velocity of the roller include: Within the sliding zone, multiple unit time intervals are selected; Calculate the roller's rotation angle and revolution angle based on the measured displacement sequence data within each unit time interval; Calculate the average of the roller's rotation angle and revolution angle over all unit time intervals to obtain the actual revolution angular velocity and actual rotation angular velocity.

[0013] As a preferred option, the revolution angle and rotation angle of the roller are calculated using the following formula: in, Indicates the angle of rotation; Indicates the revolution angle. and These represent key points in time. and Global coordinates at time; and These represent the roller center at time. and Global coordinates; and These represent the initial and final times of each unit time interval, respectively.

[0014] As a preferred option, the kinematic trajectory model of the roller is as follows: in, Indicates the radius of revolution of the roller center; This indicates the actual angular velocity of the roller's revolution. This indicates the actual angular velocity of the roller's rotation; Indicates a point in time; This represents the measured displacement sequence of key point A in the global coordinate system. This represents the coordinates of key point A in the roller coordinate system.

[0015] A cylindrical roller trajectory tracking device includes: Bearing testing machine: used to fix bearings and provide speed and load; Scattered speckle pattern: Attached to the end face of the roller to form a random speckle pattern containing key points; High-speed camera: perpendicular to the end face of the roller, used to acquire image sequences; Computer: Used to receive image sequences acquired by a high-speed camera and execute the described cylindrical roller trajectory tracking method.

[0016] As a preferred option, a stable light source is also included to illuminate the roller end face.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. By tracking the changes in random speckle patterns on an object's surface before and after deformation, relevant algorithms are used to accurately calculate the displacement and strain fields of the object's surface. DIC (Displacement-Induced Collision) technology directly visualizes and quantifies the complex motion between the roller end face and the flange, accurately distinguishing between rolling and sliding components, and measuring key parameters such as sliding speed and sliding distance. It provides high-precision, visualized experimental data for various existing dynamic and tribological models to verify their correctness. Applying DIC technology to the detection of rolling-slip condition of cylindrical roller bearing roller end faces has extremely important theoretical and engineering value.

[0018] 2. In the process of image matching, it can overcome the image mismatch problem caused by the high speed and large angle rotation of the roller, and solve the core problems of failure in this scenario and inability to accurately quantify the roller sliding displacement. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of speckle matching on the end faces of the multi-reference rollers in this invention; Figure 2 This is a schematic diagram of the cylindrical roller trajectory tracking device in this invention; Figure 3 This is a schematic diagram of the rolling position of the roller in this invention. Detailed Implementation

[0021] The present invention will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0022] It should be noted that, unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "a," "an," or "the," etc., used in the specification and claims of this patent application do not express a limitation on quantity, but rather indicate the presence of at least one; the terms "first," "second," and "third," as used herein, should not be considered as a limitation on the order of components, but are merely for distinguishing different components; the terms "comprising," "including," etc., indicate that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including" and their equivalents, but do not exclude other elements or objects having the same function.

[0023] To more clearly describe the cylindrical roller trajectory tracking method and device, in conjunction with the attached... Figure 1-3 This embodiment is described as follows: like Figure 1-3 As shown, the cylindrical roller trajectory tracking method includes the following steps: Based on the digital image correlation method with multi-reference matching, the measured displacement sequence of key point A on the roller end face in the global coordinate system is obtained. Based on the measured displacement sequence Plot the keypoint displacement curve of keypoint A with respect to time; determine the motion state of the roller based on the shape characteristics of the keypoint displacement curve, and divide the smooth part of the keypoint A displacement curve into the rolling zone, and the part with jumping or sharp points into the sliding zone; based on the measured displacement sequence corresponding to the sliding zone... Calculate the actual angular velocity of the roller's revolution. and actual rotational angular velocity ; the actual orbital angular velocity and actual rotational angular velocity By substituting the roller kinematic trajectory model, the roller motion trajectory under actual rolling and sliding conditions of the bearing is obtained.

[0024] The digital image correlation method based on multi-reference matching includes the following calculation process: dividing the speckle region of the roller end face into multiple sub-regions, and establishing the coordinate mapping relationship between the sub-regions of the reference image and the deformed image through shape functions; defining a function to measure the similarity between the reference sub-region and the deformed candidate sub-regions, and using a search algorithm to find the extreme value of the correlation coefficient to achieve sub-region matching.

[0025] Specifically, the two-dimensional digital image correlation (DIC) method calculates the two-dimensional displacement and strain fields of an object's surface by tracking the changes in naturally or artificially created random speckle patterns before and after deformation. A two-dimensional DIC measurement system / cylindrical roller trajectory tracking device mainly includes: Bearing testing machine: used to fix bearings and provide speed and load; Scattered speckle pattern: Attached to the end face of the roller to form a random speckle pattern containing key points; High-speed camera: perpendicular to the end face of the roller, used to acquire image sequences; Computer: Used to receive image sequences acquired by a high-speed camera and execute a cylindrical roller trajectory tracking method.

[0026] It also includes a stable light source to illuminate the roller end face and prevent fluctuations in the brightness of the roller image.

[0027] The detection process of roller displacement trajectory can be divided into three core steps: image acquisition, correlation calculation, and displacement field solution.

[0028] Before the bearing rotates, i.e., before the speckle deformation of the bearing roller end face, an image is acquired as a reference image. After the bearing rotates, i.e., after the end face speckle deformation, a series of images are acquired as deformed images. The DIC algorithm divides the speckle region of the roller end face into many small sub-regions, and the core of the calculation is to find the new position of each sub-region in the reference image in the deformed image. Assume that there is a point in the reference image... The sub-region centered on the image moves and deforms in the deformed image, with the center point moving to... .

[0029] To describe whether a subregion has undergone not only translation but also deformations such as rotation and stretching, a shape function is used to establish the mapping relationship between the coordinates of the two. The most commonly used is the first-order shape function, which assumes that the deformation within the subregion is uniform. If only the rigid translation of the subregion is considered, the shape function simplifies to: (1) DIC (Discretionary Interference Function) measures the similarity between a reference subregion and a deformed candidate subregion by defining a correlation function. Image matching is achieved by finding the extreme values ​​(maximum or minimum) of the correlation coefficient using a correlation search algorithm. This paper employs the minimum distance sum of squares coefficient model. (2) In the formula: This represents the minimum squared distance and correlation coefficient, which measures the similarity between the reference subregion and the deformed subregion. , This represents the relative coordinate index of a pixel within a sub-region, and iterates through all pixels within that sub-region. Indicates the half width of the sub-region; Represents any point in the reference sub-image grayscale value; express The corresponding point in the deformed image grayscale value; , This indicates that it is used to compensate for linear changes in grayscale caused by illumination.

[0030] The above equation is a nonlinear equation. After giving initial values, the least squares method is usually used for calculation. For each frame in the image sequence, the above calculation is repeated to obtain the displacements u(t) and v(t) of one or more points on the roller end face at different times. By connecting these points with u as the abscissa and v as the ordinate, the two-dimensional displacement trajectory of that point is obtained.

[0031] Due to the high speed of bearings, speckle matching on the roller end faces may fail due to excessive image rotation angles. This paper proposes a multi-reference speckle image matching method, which dynamically updates the reference image during the matching process. This enables high-speed and high-precision detection of the roller sliding displacement trajectory. Multi-reference speckle matching is described below. Figure 1 As shown.

[0032] First, a preset image relative rotation angle threshold or bearing rotation time threshold is established. During the dynamic update of the reference image benchmark, the following checks are performed in real time: whether the relative rotation angle between the current deformed image and the current reference image is greater than the image relative rotation angle threshold; or whether the difference between the corresponding bearing rotation time of the current deformed image and the current reference image is greater than the bearing rotation time threshold. If either the image relative rotation angle threshold or the bearing rotation time threshold is satisfied, the image of the current or subsequent frame is updated to a new reference image, and matching with subsequent images continues based on the new reference image.

[0033] Specifically, assuming a static roller speckle image f0 before the bearing rotates, after time t and a rotation angle of α1, images f01, f02…f0n are obtained at intervals of Δt. These n images are matched with speckle patterns using image f0 as the reference to obtain the displacement of any point on the roller end face within time t. When the bearing rotates for t+Δt, i.e., when image f1 is relatively static, it cannot be matched properly with the static roller speckle image due to the large rotation angle. Therefore, the speckle images f11, f12…f1n within the time interval t+Δt—2t are matched with image f1 as the reference. Similarly, the images within the time interval 2t+Δt—3t are matched with image f2 as the reference, and so on until matching is complete. This multi-reference speckle matching method solves the problem that the general digital image correlation method cannot accurately match due to large image changes, and is suitable for displacement tracking and detection of rotating parts such as bearings.

[0034] Specific implementation steps: 1. Experimental preparation Digital image correlation techniques require the creation of a high-quality random speckle field on the end face of the roller under test. Due to bearing lubrication, the roller surface is covered with lubricating oil, making it difficult for the random speckles from a typical matte black and white paint spray to adhere to the roller surface. Based on the characteristic that the roller only undergoes translational motion and does not deform, appropriately sized speckle patches can be used as the detection speckle on the roller end face. The speckle patch has good adhesion, adheres to the roller end face, and rotates at high speed with the roller.

[0035] Set up the test apparatus, such as Figure 2 As shown.

[0036] A high-speed camera is placed perpendicular to the roller end face, with a uniform and stable light source illuminating the roller end face. The camera focus is adjusted to clearly display the speckle pattern on the roller end face. The camera is calibrated using a black and white grid calibration plate to obtain its internal and external parameters. The cylindrical roller bearing is fixed on the bearing testing machine, with the inner ring of the bearing fixed to the rotating shaft. A servo electrode is directly connected to provide the required rotational speed, and a loading mechanism provides the lateral load. The outer ring of the bearing is fixed by an outer ring cap.

[0037] 2. Data Acquisition and Processing With the bearing stationary, a speckle image of the bearing is acquired using a digital image correlation system as a reference image. The bearing testing machine is started and run under set conditions, while a camera records an image sequence at a high frame rate. The image sequence is processed using DIC software. In the software, one or more points of interest on the roller end face are defined, and based on a two-dimensional digital image correlation method based on multi-reference matching, the software automatically calculates the precise position of these points in each frame.

[0038] 3. Key point trajectory calculation Export the displacement-time data for the required points on the roller end face. Use data processing software to plot the displacement trajectory. By analyzing the shape of the trajectory, the motion state of the roller can be determined: under standard pure rolling conditions, the trajectory should be a smooth circle or ellipse. When slippage exists, the trajectory will show irregular jumps or sharp points.

[0039] 4. Roller slip calculation In cylindrical bearings, key points on the rollers simultaneously participate in the rotation of the rolling element about its own axis and the revolution about the bearing's centerline.

[0040] like Figure 3 As shown, the outer ring of the bearing is stationary, while the inner ring moves at an angular velocity... Considering the roller's rotation, which involves both sliding and rolling conditions, the trajectory of any point on the roller's end face depends on the roller's angular velocity of revolution. angular velocity of rotation And the coordinates of this point in the roller coordinate system. The initial coordinates of key point A in the roller coordinate system are (x, y), and the coordinates of point A1 after rotating for a certain time are (x1, y1).

[0041] Roller center revolution radius: + (3) The angular velocity of the roller's revolution is: (4) The angular velocity of the roller's rotation is: (5) in, Indicates the inner radius; Indicates the outer radius.

[0042] The global coordinate system of point A, obtained through a digital image correlation method based on multi-reference matching, allows us to obtain the coordinates of point A in the roller coordinate system using the roller radius and the bearing inner ring radius. ).

[0043] Therefore, the global coordinates (x(t), y(t)) of point A are functions of time, and the kinematic trajectory model of the roller is as follows: (6) (7) in, Indicates the radius of revolution of the roller center; Indicates the angular velocity of the roller's revolution; This indicates the angular velocity of the roller's rotation; Indicates a point in time; This represents the measured displacement sequence of key point A in the global coordinate system. This represents the coordinates of key point A in the roller coordinate system.

[0044] The above equations describe the motion path of any point on the roller end face in a plane. Due to factors such as bearing friction and lubrication, the rollers slip, and the above equations need to be adjusted for the revolution angular velocity. and rotational angular velocity .

[0045] Using the previously obtained key point displacement curves, the location where roller slippage occurs is observed, and the actual angular velocity of the roller in the slip zone is calculated. and actual rotational angular velocity ; the actual orbital angular velocity and actual rotational angular velocity By substituting the roller kinematic trajectory model into formulas (6) and (7), the roller motion trajectory under actual rolling and sliding conditions of the bearing is obtained.

[0046] For calculating the actual angular velocity of the roller. and actual rotational angular velocity It is only necessary to calculate the revolution angle φ and rotation angle within a known time period after the bearing has rotated smoothly. Then, by averaging multiple samples, the actual revolution angular velocity and the actual rotation angular velocity can be obtained.

[0047] Revolution angle φ and rotation angle The calculation method is as follows: Assuming that at time t0, the coordinates of O(xo,yo), A0(x,y), and P0(xpo,ypo) can be obtained in the global coordinate system using the digital image correlation method, and the bearing rotates to time t1, with A0 rotating to position A1, the coordinates of O(xo,yo), A1(x1,y1), and P1(xp1,yp1) can be calculated. Then: (8) (9) in, Indicates the angle of rotation; Indicates the revolution angle. and These represent key points in time. and Global coordinates at time; and These represent the roller center at time. and Global coordinates; and These represent the initial and final times of each unit time interval, respectively.

[0048] The parts not described in detail in the above embodiments are existing technologies.

[0049] It should be noted that although the present invention has been described through the above embodiments, the present invention may have many other embodiments. Without departing from the spirit and scope of the present invention, those skilled in the art can obviously make various corresponding changes and modifications to the present invention, but all such changes and modifications should fall within the scope of protection of the appended claims and their equivalents.

Claims

1. A cylindrical roller trajectory tracking method, characterized by, The method comprises the following steps: Based on multi-benchmark matching digital image correlation method, the measured displacement sequence of key point A on the end face of the roller in the global coordinate system is obtained ; According to the measured displacement sequence Plot a key point displacement curve of the key point A with respect to time; According to the shape characteristics of the key point displacement curve, the motion state of the roller is determined, and the smooth part of the key point displacement curve is divided into a rolling zone, and the part with jumping or sharp point is divided into a sliding zone; based on the measured displacement sequence corresponding to the sliding zone , calculate the actual revolution angular velocity of the roller and the actual rotation angular velocity ; the actual revolution angular velocity and the actual rotation angular velocity into the roller kinematics trajectory model, to obtain the roller motion trajectory under the actual rolling and sliding condition of the bearing.

2. The cylindrical roller track following method according to claim 1, characterized in that The digital image correlation method based on multi-reference matching, the calculation process of which comprises: The speckle area of the roller end face is divided into multiple sub-zones, and the coordinate mapping relationship between the sub-zones of the reference image and the deformed image is established through a shape function; A function is defined to measure the similarity between the reference sub-zone and the deformed candidate sub-zone, and the extreme value of the correlation coefficient is obtained through a search algorithm to realize the matching of the sub-zones.

3. The cylindrical roller track following method according to claim 2, characterized in that: In the matching process, the reference image is dynamically updated.

4. The cylindrical roller track following method according to claim 3, characterized in that First, the image relative rotation angle threshold or bearing rotation time threshold is preset, and in the process of dynamically updating the reference image: Real-time judge whether the relative rotation angle between the current deformed image and the current reference image in the image matching process is greater than the image relative rotation angle threshold; Or Real-time judge whether the difference between the corresponding bearing rotation time of the current deformed image and the current reference image in the image matching process is greater than the bearing rotation time threshold; If yes, the current or subsequent image is updated as a new reference image, and the subsequent image is matched based on the new reference image.

5. The cylindrical roller track following method according to claim 1, characterized in that, The steps of calculating the actual revolution angular velocity and the actual rotation angular velocity of the roller comprise: In the sliding zone, multiple unit time intervals are selected; from the measured displacement sequence in each unit time interval data computing the roll angle of the roller and the revolution angle ; The average of the roll angles in all unit time intervals is calculated and the average of the revolution angles to obtain the actual revolution angular velocity and the actual roll angular velocity .

6. The cylindrical roller track following method according to claim 1, characterized in that, Rolling angle of the roller and the rotation angle is calculated by the following equation: wherein, denotes a rotation angle; denotes an orbit angle, and denote global coordinates of the key point at times and respectively; and denote global coordinates of the roller center at times and respectively; and denote the initial time and the end time of each unit time interval respectively.

7. The cylindrical roller track following method according to claim 1, characterized in that, The kinematic trajectory model of the roller is: wherein, represents the rolling center revolution radius of the roller; represents the actual revolution angular velocity of the roller; represents the actual rotation angular velocity of the roller; represents the time point; represents the measured displacement sequence of the key point A in the global coordinate system, represents the coordinates of the key point A in the roller coordinate system.

8. A cylindrical roller track following device, characterized in that Comprise: Bearing tester: used for fixing the bearing and providing rotation speed and load; Speckle paste: attached to the roller end face, forming a random speckle pattern containing key point A; High-speed camera: perpendicular to the roller end face, used for collecting image sequences; Computer: used for receiving the image sequences collected by the high-speed camera, and performing the cylindrical roller trajectory tracking method according to any one of claims 1-7.

9. The cylindrical roller trajectory tracking device of claim 8, wherein: Also comprising a stable light source for illuminating the roller end face.

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