Workpiece inner wall automatic measuring device and measuring method suitable for assembly line production

Abstract

The application relates to a workpiece inner wall automatic measurement device and method suitable for assembly line production, which comprises a conveying platform, a structure frame, an image acquisition device, a moving platform and a probe measurement device. The conveying platform is used for bearing and conveying the measured parts. The structure frame is connected to the conveying platform and fixed above the conveying platform. The image acquisition device is fixed to the structure frame and located above the conveying platform. The moving platform is mounted on the structure frame and located above the conveying platform, and the moving platform can move above the conveying platform along the structure frame. The probe measurement device is fixed to the moving platform and located above the conveying platform, and the probe measurement device can move above the measured parts along with the movement of the moving platform. The probe measurement device is used for acquiring image data flow of the measured parts and motion data flow of the measurement probe. The device can be connected to the assembly line production, has high measurement precision and guarantees the safety of the parts and equipment.

Description

Technical Field

[0001] This invention belongs to the field of parts measurement technology, specifically relating to an automated measurement device and method for the inner wall of a workpiece adapted to assembly line production. Background Technology

[0002] For ring-shaped workpieces, taking automobile wheel hubs as an example, after casting and machining processes, parameters such as inner diameter, outer diameter, and mechanical hole position accuracy need to be inspected. These parameters are relatively easy to measure in automated measurement; for example, high-precision area scan cameras or high-precision line scan cameras can achieve automated measurement and acquire relevant parameters of varying accuracy. However, for grooves and bosses on the inner wall of the central hole, due to their special location and limited working space, conventional inspection methods are inconvenient. For example, binocular cameras or 3D contour cameras are often too large to penetrate, and the mutual obstruction of the measured parts prevents accurate measurement. Existing scanning or measuring equipment for the inner walls of some large cavities and pipes generally has low accuracy due to pixel limitations, as its measurement data relies on image pixels. Parameter measuring rulers and other devices specifically designed for this problem require manual operation, are difficult to automate, and cannot be connected to production lines. Large, high-precision equipment such as coordinate measuring machines are often very expensive.

[0003] Currently, the measurement methods for bosses or grooves on the inner wall of annular workpieces mainly fall into two categories. The first category is an inner wall point cloud imaging system designed using binocular ranging and laser triangulation principles. The second category is a mechanical measuring device specialized for related problems.

[0004] The first category is represented by "an automated measuring device and method for the inner wall of hollow components." Its measurement principle involves a rotating measuring module scanning the inner wall of the cavity using laser triangulation. The measurement is based on image pixels, resulting in low accuracy and the inability to achieve fully automated operation or connect to a production line. While using laser triangulation to measure distance or using binocular imaging to generate point cloud data of the inner wall provides some descriptive ability for the geometric features, inner diameter parameters, and defects, its measurement capability is derived from pixels, leading to low accuracy. Furthermore, this method has better imaging effects for larger cavities or pipes, making it difficult to miniaturize and adapt to the needs of production lines.

[0005] The second category is represented by "a measuring device for accurately measuring the depth and width of deep inner hole grooves." This device is a manual measuring device similar to calipers. Before measurement, the position of the part needs to be adjusted, and the measurement and reading are done manually. The measurement accuracy is relatively high. However, this device cannot achieve automated measurement, and the contact measurement method can easily cause some damage to the workpiece surface. At the same time, this device does not meet the measurement requirements of assembly line scenarios.

[0006] Other possible methods for measuring bosses or grooves on the inner wall of annular workpieces include 3D cameras and coordinate measuring machines (CMMs). However, 3D cameras are too large and can only measure from the outside of the part's hole diameter. This causes the three-dimensional geometry of the inner wall to obscure each other, making it impossible to measure all parameters and complete automated measurement. Coordinate measuring machines are also bulky, expensive, and complex to operate, making them unsuitable for the full inspection requirements of production lines.

[0007] Therefore, existing methods for measuring bosses or grooves on the inner wall of annular workpieces have the following drawbacks: 1. They cannot be connected to production lines and achieve fully automated measurement; 2. Detection methods that use camera pixels to extract distance parameters are highly dependent on camera extrinsic parameters, which not only have strict operating conditions but also low measurement accuracy. That is, only when the height of the camera and the workpiece to be inspected is relatively constant can the position information extracted from the camera maintain a corresponding relationship with the actual size; 3. Some contact measurement technologies come into direct contact with the parts, which may scratch or damage the parts. Summary of the Invention

[0008] To address the aforementioned problems in the existing technology, this invention provides an automated measuring device and method for the inner wall of workpieces adapted to assembly line production. The technical problem to be solved by this invention is achieved through the following technical solution:

[0009] This invention provides an automated workpiece inner wall measurement device adapted for assembly line production, comprising: a conveyor platform, a structural frame, an image acquisition device, a moving platform, and an insertion measuring device, wherein...

[0010] The conveying platform is used to carry and convey the parts to be tested;

[0011] The structural frame is connected to the conveying platform and fixed above the conveying platform;

[0012] The image acquisition device is fixed on the structural frame and located above the conveying platform, and is used to detect the model of the part under test and track the position of the part under test;

[0013] The mobile platform is mounted on the structural frame and located above the conveying platform, and the mobile platform can move along the structural frame above the conveying platform;

[0014] The probe measuring device is fixed on the moving platform and located above the conveying platform. The probe measuring device can move to the top of the part to be measured as the moving platform moves. The probe measuring device is used to insert a measuring probe into the aperture of the part to be measured when it is facing the aperture of the part to be measured, so as to obtain the image data stream of the measured part of the aperture inner wall of the part to be measured and the motion data stream of the measuring probe.

[0015] In one embodiment of the present invention, the structural frame includes a portal frame; the image acquisition device includes a camera.

[0016] In one embodiment of the present invention, the moving direction of the mobile platform is perpendicular to the conveying direction of the conveying platform.

[0017] In one embodiment of the present invention, the probe-type measuring device includes a linear motion platform, a grating ruler, a measuring probe, and a connecting rod, wherein,

[0018] The grating probe of the grating ruler is connected to the slide of the linear motion platform via a connector. The grating probe is used to detect the movement of the slide in real time to obtain the motion data stream of the measuring probe.

[0019] The measuring probe is connected to the slide table via the connecting rod. The slide table is used to perform linear motion to drive the measuring probe to perform insertion measurement.

[0020] In one embodiment of the present invention, the measuring probe includes a holder and an image acquisition module, wherein,

[0021] The retainer is connected to the slide table;

[0022] The image acquisition module is fixed on the holder and is used to acquire image data streams of the inner wall of the part under test when the slide moves.

[0023] In one embodiment of the present invention, the measuring probe further includes a laser head, wherein,

[0024] The laser head is fixed on the holder, and the line of sight of the laser head is at a certain angle to the line of sight of the image acquisition module, so that the image of the part to be tested is superimposed on the laser spot.

[0025] In one embodiment of the present invention, the measuring probe further includes a micro switch disposed directly below the retainer.

[0026] Another embodiment of the present invention provides an automated measurement method for the inner wall of a workpiece adapted to assembly line production, characterized in that the measurement is performed using the measuring device described in the above embodiments, including the following steps:

[0027] The conveying platform and the moving platform are adjusted so that the probe measuring device is aligned with the aperture of the part to be measured, while the data stream of the image acquisition device is analyzed to detect the model of the part to be measured and track the position of the part to be measured.

[0028] The conveying platform and the moving platform are stopped, and the probe is inserted into the aperture of the probe measuring device to obtain the image data stream of the inner wall of the aperture of the part to be measured and the motion data stream of the probe.

[0029] Obtain the different boundaries of the measurement probe sweeping across the area to be measured from the image data stream;

[0030] The position data of the measuring probe at different boundary moments are obtained from the motion data stream, and the position data at different boundary moments are subtracted to obtain the measurement value of the part to be measured.

[0031] In one embodiment of the present invention, obtaining different boundary moments when the measuring probe sweeps across the region to be measured from the image data stream includes:

[0032] A coordinate system is established in the image of the area to be tested, and pixels with brightness higher than a preset threshold are obtained as target data to obtain the target data set:

[0033] {(x i y i )|0<i≤M}

[0034] Construct the Vandermonde matrix and generate a linear system using the target data set and the nth-order polynomial:

[0035]

[0036] Where n is the order of the polynomial fitting, m is the number of pixels in the current frame whose brightness is higher than a preset threshold, and a0, a1...a... n These are the polynomial coefficients;

[0037] Solving the linear system yields a fitted formula for the laser profile;

[0038] The horizontal position data stream of the laser spot is obtained based on the fitting formula of the laser profile:

[0039]

[0040] in, This is an estimate of the horizontal position of the laser spot at the center of the current frame. Here, H is the fitting polynomial for the laser profile, H is the height of the current frame image, and α is the α value. i The image data stream of the area to be tested. The timestamp is where i is the image frame number and M is the image frame number.

[0041] The gradient of the horizontal position data stream of the laser spot is calculated, and the times corresponding to the maximum and minimum gradient values ​​are obtained. These times are taken as the different boundary times. The gradient calculation formula is as follows:

[0042]

[0043] Where, α k Let α be the horizontal position data of the k-th laser spot. k+1 Let α be the horizontal position data of the (k-1)th laser spot. k-1 Given the horizontal position data of the (k-1)th laser spot, the maximum gradient value is grad(a). max The minimum value of the gradient is grad(α). min The maximum value corresponds to the time when The time corresponding to the minimum value is

[0044] In one embodiment of the present invention, acquiring position data of the measuring probe at different boundary moments from the motion data stream, and subtracting the position data at different boundary moments to obtain the measurement value of the part to be measured, includes:

[0045] Using the motion data stream, the position data of the measuring probe at different boundary moments are estimated using Lagrange interpolation, where the Lagrange interpolation polynomial is:

[0046]

[0047] in, Let M′ represent the data stream of the grating ruler, t be the time interval, n be the order of the Lagrange interpolation polynomial, and L be the number of data points in the grating ruler data stream. i (t) is a polynomial of degree n = M′+1:

[0048]

[0049] in, This refers to the time of the (i-1)th grating ruler data, where i = 1, 2, ..., n;

[0050] The measured value of the part to be measured is obtained by subtracting the position data at different boundary times:

[0051]

[0052] in, For different boundary moments.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1. The automated measuring device of the present invention takes into account the actual production line situation. It adopts a conveyor platform to carry and transport the parts to be measured, which not only meets the functional requirements of the device, but also takes into account the requirements of other parameter measurement processes. This allows other measurement modules to be directly added to the device to complete the measurement tasks of other parameters. It can be connected to the production line to realize the automated inspection process of the parts to be measured on the production line, thereby replacing manual measurement and improving inspection efficiency.

[0055] 2. The automated measuring device of the present invention acquires the image data stream of the part to be measured and the motion data stream of the measuring probe through the probe measuring device. By fusing the image data stream and the motion data stream, the measured value of the part to be measured can be obtained. The measurement accuracy does not depend on the camera pixels and camera extrinsic parameters. High measurement accuracy can be obtained by using a camera with ordinary resolution. This can improve the applicability of the device and reduce the cost of the device, thereby solving the problems caused by the mixed measurement of parts of different sizes.

[0056] 3. This invention uses an insertion-type measuring device to perform non-contact insertion measurement. It can insert into the small-diameter interior of the part to complete the parameter measurement. During the measurement process, it will not directly contact the part, and it can perform precise closed-loop control of the part position to ensure the safety of the part and equipment. Attached Figure Description

[0057] Figure 1 An overall structural diagram of an automated workpiece inner wall measurement device adapted for assembly line production, provided in an embodiment of the present invention;

[0058] Figure 2 This is a structural diagram of a probe-type measuring device provided in an embodiment of the present invention;

[0059] Figure 3 A structural diagram of the measuring probe provided in an embodiment of the present invention;

[0060] Figures 4a-4b This is a schematic diagram of the linear laser imaging principle of the present invention;

[0061] Figure 5 A flowchart of an automated measurement method for the inner wall of a workpiece adapted for assembly line production is provided in an embodiment of the present invention. Detailed Implementation

[0062] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0063] Example 1

[0064] Please see Figure 1 , Figure 1 The overall structural diagram of the automated workpiece inner wall measurement device adapted for assembly line production provided in this embodiment of the invention.

[0065] The measuring device includes a conveyor platform 1, a structural frame 2, an image acquisition device 3, a moving platform 4, and an insertion measuring device 5. The conveyor platform 1 carries and transports the part to be measured. The conveyor platform 1 can be a double-row narrow-strip conveyor platform or a conveying method such as a robotic arm clamping to complete the transfer and measurement of the part. The structural frame 2 is connected to the conveyor platform 1 and fixed above it. The image acquisition device 3 is fixed to the structural frame 2 and located above the conveyor platform 1, used to detect the model of the part and track its position. The moving platform 4 is mounted on the structural frame 2 and located above the conveyor platform 1, and can move along the structural frame 2 above the conveyor platform 1. The probe measuring device 5 is fixed on the moving platform 4 and located above the conveying platform 1. The probe measuring device 5 can move to the top of the part to be measured as the moving platform 4 moves. The probe measuring device 5 is used to insert a measuring probe into the aperture when it is facing the aperture of the part to be measured, so as to obtain the image data stream of the measured part of the aperture and the motion data stream of the measuring probe.

[0066] Specifically, the device consists of a conveyor platform 1 as its base, which carries the part to be measured and connects to and fixes a structural frame 2. The structural frame 2 can be a portal frame. A moving platform 4 is mounted on the top of the structural frame 2, and the moving direction of the moving platform 4 forms an angle θ with the conveying direction of the conveyor platform 1, where 0° < θ ≤ 90°. It can be understood that the moving platform 4 can be a lateral moving platform, in which case its moving direction is perpendicular to the conveying direction of the conveyor platform 1; the moving platform 4 can also move above the conveyor platform 1 at any other angle, thus achieving movement above the part to be measured. An insertion measuring device 5 is fixed to the moving platform 4 and can move laterally along with the moving platform 4. An image acquisition device 3 can be a camera. The image acquisition device 3 is fixed to the structural frame 2 via a connecting rod. The image acquisition device 3 is fixed relative to the structural frame 2. After determining the extrinsic parameter matrix of the image acquisition device 3, it is used to detect the part's model and track its position. Overall, the conveyor platform 1 transports the part to be tested to the area directly below the structural frame 2. The transverse moving platform 4 on the structural frame 2 aligns the probe measuring device 5 with the aperture of the part to be tested, thereby inserting the sensor and completing the measurement.

[0067] The automated measurement device in this embodiment takes into account the actual production line situation. It uses a conveyor platform to carry and transport the parts to be measured, which not only meets the functional requirements of the device, but also takes into account the requirements of other parameter measurement processes. For example, when using a line scan camera, back lighting is required, which allows other measurement modules to be added directly to the device to complete the measurement tasks of other parameters. It can be connected to the production line to realize the automated inspection process of the parts to be measured on the production line, thereby replacing manual measurement and improving inspection efficiency.

[0068] The automated measurement device in this embodiment acquires image data streams of the part to be measured and motion data streams of the measuring probe through an immersion measuring device. By fusing the image data streams and motion data streams, the measured value of the part to be measured can be obtained. The measurement accuracy does not depend on camera pixels and camera extrinsic parameters. High measurement accuracy can be obtained using a camera with ordinary resolution. This can improve the applicability of the device and reduce the cost of the device, thereby addressing the problems caused by mixed measurement of parts of different sizes.

[0069] This embodiment uses an insertion-type measuring device to perform non-contact insertion measurements. It can penetrate into the small-diameter interior of a part to complete parameter measurements without directly contacting the part during the measurement process. Furthermore, it performs precise closed-loop control of the part's position, ensuring the safety of both the part and the equipment.

[0070] Please see Figure 2 , Figure 2 This is a structural diagram of a probe-type measuring device provided in an embodiment of the present invention. The probe-type measuring device 5 includes a linear motion platform 51, a grating ruler 52, a measuring probe 53, and a connecting rod 54. The grating probe of the grating ruler 52 is connected to the slide of the linear motion platform 51 via a connector. The grating probe is used to detect the movement of the slide in real time to obtain the motion data stream of the measuring probe 53. The measuring probe 53 is connected to the slide via the connecting rod 54. The slide is used to perform linear motion to drive the measuring probe 53 to perform probe-type measurements.

[0071] Specifically, the probe-type measuring device is based on a linear motion platform 51. A grating probe is mounted on a grating ruler 52, and a slide is mounted on the linear motion platform 51. The grating ruler 52 is connected to the slide of the linear motion platform 51 via a connector, and the grating probe is used to detect the movement of the slide in real time. A connecting rod 54 connects the slide and the measuring probe 53, and the linear motion of the slide drives the measuring probe 53 to perform probe-type measurements.

[0072] Please see Figure 3 , Figure 3 This is a structural diagram of a measuring probe provided in an embodiment of the present invention. The measuring probe 53 includes a holder 531, an image acquisition module 532, and a laser head 533, wherein the holder 531 is connected to a slide table. The laser head 533 is fixed on the holder 531, and the line of sight of the laser head 533 is at a certain angle to the line of sight of the image acquisition module 532, so that the image of the part to be measured is superimposed on the laser spot of the laser head 533. The image acquisition module 532 is fixed on the holder 531 and is used to acquire the image data stream of the inner wall of the hole of the part to be measured when the slide table moves. At this time, the image data stream acquired by the image acquisition module 532 includes the laser spot.

[0073] Specifically, this part of the structure is based on the cage 531. The image acquisition module 532 can be a probe camera module. The laser head 533 and the image acquisition module 532 are fixed on the cage, and the line of sight of the laser head and the image acquisition module 532 are at a certain angle.

[0074] Specifically, the laser head 533 can be a linear laser head or a dot laser head.

[0075] In another embodiment, the measuring probe 53 includes a holder 531 and an image acquisition module 532, the holder 531 being connected to a slide. The image acquisition module 532 is fixed to the holder 531 and is used to acquire image data streams of the inner wall of the bore of the part under test when the slide moves. In this case, the image data stream acquired by the image acquisition module 532 does not include the laser spot.

[0076] In another embodiment, the measuring probe 53 may further include a microswitch disposed directly below the retainer. If the measuring probe 53 collides with a part during downward insertion, the microswitch will be triggered. Upon detecting the trigger signal, the system will stop operating and readjust the position of the measuring probe to align with the hole.

[0077] Installing a microswitch below the measuring probe as a protective device can further ensure the safety of parts and equipment on the basis of non-contact probe-type measurement.

[0078] The volume of the measuring probe in this embodiment can be designed in different sizes according to actual needs, so as to achieve a smaller size and thus be able to probe into the small-diameter interior of the part to complete the parameter measurement, thereby improving the applicability of the device.

[0079] Taking the measuring probe 53, which includes a retainer 531, an image acquisition module 532, and a laser head 533, as an example, the working process of this automated measuring device for the inner wall of a workpiece is as follows: When the measuring device is in operation, it is normally connected to the production line. When a part to be inspected arrives, the top image acquisition device 3 first identifies the type of part and loads the main shape parameters of that type of part. Then, after detecting the part's position through the image captured by the image acquisition device 3, it simultaneously adjusts the moving platform 4 of the conveyor platform 1 and the structural frame 2 so that the probe-type measuring device 5 is aligned with the aperture of the part to be inspected. During this process, the video stream from the top image acquisition device 3 is continuously analyzed to locate and track the part's position, thereby completing a closed-loop part position drive. Afterward, the moving platform 4 of the conveyor platform 1 and the portal frame 2 stops moving and is fixed. The probe-type measuring device 5 lowers the measuring probe and records the image from the image acquisition module 532 and the data from the grating probe. The image acquisition module 532 obtains the image data stream of the part to be inspected, and the grating probe data is the motion data stream of the measuring probe. After the probe operation is completed, the data is processed to obtain the measured value of the part to be inspected. After the probe measurement is completed, it will be retrieved, and then the conveyor platform will transfer the part to the next production line to complete one measurement cycle.

[0080] Based on the above working process, the top image acquisition device 3 is used to locate and track the position of the part and complete the closed-loop drive control of the part to align the part with the probe of the probe-type measuring device. The parameter measurement principle is as follows:

[0081] Please see Figures 4a-4b , Figures 4a-4b This is a schematic diagram of the linear laser imaging principle of the present invention, wherein 41 is a linear laser beam, 42 is the boss structure of the part to be tested, 532 is the image acquisition module, i.e., the probe camera, and 43 is the laser spot in the field of view of the camera. Figure 3 The laser head and image acquisition module are at a certain angle, where the positions of the image acquisition module and laser head relative to the workpiece are as follows: Figure 4a As shown, the laser head is located at the vertex of the triangular linear laser beam furthest from the boss structure of the part being measured. For a surface with a boss, the image captured by the image acquisition module is a superposition of the part image and the laser spot, as shown below. Figure 4b As shown.

[0082] This embodiment describes a fully automated measuring device for the inner wall bosses or grooves of ring-shaped machined parts produced on assembly lines. It requires no manual assistance, achieving complete automation and compatibility with assembly lines, thus improving inspection efficiency. The probe-type measuring device uses an image acquisition module combined with a grating ruler, avoiding errors caused by inaccurate camera extrinsic parameters and reducing the resolution requirements of the camera. Measurement accuracy is not dependent on camera pixels but rather on camera frame rate, probe speed, and grating ruler accuracy. High measurement accuracy and good robustness can be achieved using cameras with ordinary resolution, thereby reducing costs. This invention employs a probe-type measuring device for non-contact measurement, allowing it to penetrate small-diameter holes in parts to complete parameter measurements without direct contact with the part. It also provides precise closed-loop control of the part's position. The measuring probe is equipped with a protective device to ensure the safety of both the part and the equipment.

[0083] Example 2

[0084] Based on Example 1, this example provides an automated measurement method for the inner wall of a workpiece adapted to assembly line production.

[0085] For example Figure 4b The height of the protrusion can be calculated directly from the number of pixels in the captured image and combined with camera extrinsic parameters. However, this method is limited by pixel density and cannot achieve high-precision measurement. Therefore, this embodiment proposes a measurement scheme using a grating ruler in conjunction with the data stream of the image acquisition module. This scheme is not limited by the resolution of a single camera image, and its measurement accuracy depends on the camera frame rate, probe movement speed, and grating ruler accuracy, achieving higher measurement accuracy and reducing costs. This measurement method uses the measurement device of Embodiment 1 and includes the following steps:

[0086] S1. Adjust the conveyor platform 1 and the moving platform 4 so that the probe measuring device 5 is aligned with the aperture of the part to be measured, and at the same time analyze the data stream of the image acquisition device 3 to detect the model of the part to be measured and track the position of the part to be measured.

[0087] S2. Stop the movement of the conveyor platform 1 and the moving platform 4, and insert the probe of the probe-type measuring device 5 into the aperture to obtain the image data stream of the measured part on the inner wall of the aperture and the motion data stream of the measuring probe. Specifically, the image data stream of the measured part can be obtained through the image acquisition module 532, and the motion data stream of the measuring probe can be obtained through the grating ruler.

[0088] S3. Obtain the different boundary times when the measuring probe sweeps across the part to be measured from the image data stream.

[0089] S4. Obtain the position data of the measuring probe at different boundary times from the motion data stream, and subtract the position data at different boundary times to obtain the measurement value of the part to be measured.

[0090] Please see Figure 5 , Figure 5 This invention provides a flowchart of an automated measurement method for the inner wall of a workpiece adapted for assembly line production. Specifically, measurement begins when the part to be measured is aligned with the probe-type device. The measuring probe, driven by the linear motion platform of the probe-type measuring device, penetrates into the aperture to perform the measurement. The image data stream of the measured area acquired by the image acquisition module, the motion data stream of the measuring probe acquired by the grating ruler, and the corresponding timestamps are recorded. The processing of the image data stream can be performed simultaneously with the acquisition or after the acquisition is completed. The processing of the image data stream yields the times when the measuring probe sweeps across different boundaries of the measured area. This data is then combined with the motion data stream of the grating ruler for data fusion to obtain the measured parameters.

[0091] When the image data stream does not include the laser spot, existing image processing methods are used to obtain the different boundary moments when the measuring probe sweeps across the part to be measured from the image data stream.

[0092] Compared to existing methods, this method directly obtains the different boundary moments when the measuring probe sweeps across the part to be measured from the image data stream, and then fuses the different boundary moments with the motion data stream to obtain the parameters to be measured. This method avoids the errors caused by inaccurate camera extrinsic parameters, reduces the resolution requirements of the camera, and reduces costs.

[0093] When the image data stream includes a laser spot, the processing of the image data stream aims to estimate the horizontal position of the laser spot at the center of the current frame, thereby estimating the different boundary moments when the measuring probe sweeps across the area to be measured.

[0094] Specifically, when the image data stream includes a laser spot, obtaining the different boundary moments when the measuring probe sweeps across the area to be measured from the image data stream includes the following steps:

[0095] S31. Establish a coordinate system in the image of the part to be tested and obtain the pixels with brightness higher than the preset threshold as target data to obtain the target data set.

[0096] Specifically, a coordinate system is established with the top-left corner of the image as the origin, the positive x-axis pointing downwards from the origin, and the positive y-axis pointing to the right from the origin. First, the coordinates of pixels in the image with brightness higher than a threshold A are taken as the target data. Then, a polynomial fitting is performed on the target data; here, an nth-order fitting is used as an example to illustrate the calculation principle. Let the target data volume be M, and its set be:

[0097] {(x i y i)|0<i≤M}

[0098] Where i is the image frame number, M is the image frame number, and x i y i The target coordinates are given.

[0099] S32. Construct the Vandermonde matrix and generate a linear system using the target data set and the nth-order polynomial.

[0100] Specifically, let the nth-order polynomial be:

[0101]

[0102] Substituting the nth-order polynomial into the target data set, construct an n+1-column and m=M-row Vandermonde matrix and generate a linear system:

[0103]

[0104] Where n is the order of the polynomial fitting, m is the number of pixels in the current frame whose brightness is higher than a preset threshold, and a0, a1...a... n These are the polynomial coefficients;

[0105] S33. Solve the linear problem expressed by the linear system to obtain the fitting formula for the laser profile.

[0106] S34. Obtain the horizontal position data stream of the laser spot based on the fitting formula of the laser profile.

[0107] Specifically, assuming the image width is W and the height is H, the estimated horizontal position of the laser spot at the center of the current frame is:

[0108] Let the horizontal position data stream of the laser spot be:

[0109]

[0110] in, Here, H is the fitting polynomial for the laser profile, H is the height of the current frame image, and α is the α value. i The image data stream of the area to be tested. The timestamp is where i is the image frame number and M is the image frame number.

[0111] S35. Calculate the gradient of the horizontal position data stream of the laser spot, and find the time corresponding to the maximum value and the time corresponding to the minimum value of the gradient, and take the time corresponding to the maximum value and the time corresponding to the minimum value as the different boundary times.

[0112] Specifically, the grating ruler data is in the form of a grating ruler value β. i and its corresponding time value The data stream from the grating ruler acquired by the measuring probe is as follows:

[0113]

[0114] Because the image acquisition module and the grating ruler have different sampling frequencies and are not synchronized, their sampling point counts and timestamps do not completely correspond. Therefore, the gradient of the horizontal position data stream of the laser spot is first calculated, and the times corresponding to the maximum and minimum gradient values ​​are obtained. The times corresponding to the maximum and minimum values ​​are then used as the times when the probe sweeps across the boundary of the protrusion or groove.

[0115] Calculate using the following formula gradient:

[0116]

[0117] Where, α k Let α be the horizontal position data of the k-th laser spot. k+1 Let α be the horizontal position data of the (k-1)th laser spot. k-1 Given the horizontal position data of the (k-1)th laser spot, the maximum gradient value is grad(α). max The minimum value of the gradient is grad(α). min The maximum value corresponds to the time when The time corresponding to the minimum value is

[0118] Furthermore, after acquiring the measurement probe's position at different boundary moments across the measured area from the image data stream, the motion data stream acquired by the grating ruler is fused to estimate the parameters of the measured position of the part's boss or groove. Therefore, acquiring the position data of the measurement probe at different boundary moments from the motion data stream and subtracting the position data at different boundary moments to obtain the measured value of the measured area includes the following steps:

[0119] S41. Using the motion data stream, estimate the position data of the measuring probe at different boundary times using the Lagrange interpolation method.

[0120] Specifically, the grating probe recorded in the grating ruler data stream maintains a basically uniform motion. To improve estimation accuracy, Lagrange interpolation is used to estimate the grating probe's motion using the grating ruler data stream. and The probe position at time [time]. Let the Lagrange interpolation polynomial be:

[0121]

[0122] in, Let M′ represent the data stream of the grating ruler, t be the time interval, n be the order of the Lagrange interpolation polynomial, and L be the number of data points in the grating ruler data stream.i (t) is a polynomial of degree n = M′+1:

[0123]

[0124] in, The time of the (i-1)th grating ruler data, i = 1, 2, ..., n.

[0125] S42. Subtract the position data at different boundary moments to obtain the measured value of the part to be measured, that is, the measured value of the part to be measured, such as the boss or groove of the part:

[0126]

[0127] in, For different boundary moments.

[0128] The fusion processing method proposed in this embodiment, which integrates image data streams and motion data streams acquired by a grating ruler, estimates the coordinates of the laser spot at the current center position by processing single-frame data in the image data stream. Then, it estimates the boundary time corresponding to the boss or groove on the part by calculating the gradient of the horizontal position data stream of the laser spot. Finally, it uses interpolation to extract the position information of the boss or groove at the corresponding boundary time from the motion data stream of the grating ruler, thus obtaining the measured value of the part to be measured. This method avoids errors and accuracy problems caused by camera extrinsic errors and insufficient pixel density, reduces the resolution requirements of the camera, and significantly improves measurement accuracy.

[0129] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A measurement method for an automated measuring device for the inner wall of a workpiece adapted to assembly line production, characterized in that, The measuring device includes: a conveyor platform (1), a structural frame (2), an image acquisition device (3), a moving platform (4), and an immersion measuring device (5), wherein, The conveying platform (1) is used to carry and convey the parts to be tested; The structural frame (2) is connected to the conveying platform (1) and fixed above the conveying platform (1); The image acquisition device (3) is fixed on the structural frame (2) and located above the conveying platform (1), and is used to detect the model of the part to be tested and track the position of the part to be tested; The mobile platform (4) is mounted on the structural frame (2) and located above the conveying platform (1). The mobile platform (4) can move along the structural frame (2) above the conveying platform (1). The probe measuring device (5) is fixed on the moving platform (4) and located above the conveying platform (1). The probe measuring device (5) can move to the top of the part to be measured as the moving platform (4) moves. The probe measuring device (5) is used to insert a measuring probe into the aperture when it is facing the aperture of the part to be measured, so as to obtain the image data stream of the inner wall of the aperture of the part to be measured and the motion data stream of the measuring probe. The measurement method includes the following steps: Adjust the conveying platform (1) and the moving platform (4) so ​​that the probe measuring device (5) is aligned with the aperture of the part to be measured, and at the same time analyze the data stream of the image acquisition device (3) to detect the model of the part to be measured and track the position of the part to be measured; Stop the movement of the conveying platform (1) and the moving platform (4), and insert the probe of the probe into the aperture to obtain the image data stream of the inner wall of the aperture of the part to be measured and the motion data stream of the probe. Obtain the different boundary moments when the measurement probe sweeps across the area to be measured from the image data stream; including: A coordinate system is established in the image of the area to be tested, and pixels with brightness higher than a preset threshold are obtained as target data to obtain the target data set: Construct the Vandermonde matrix and generate a linear system using the target data set and the nth-order polynomial: in, n Let be the order of the polynomial fitting. m This represents the number of pixels in the current frame whose brightness exceeds a preset threshold. , … These are the polynomial coefficients; Solving the linear system yields a fitted formula for the laser profile; The horizontal position data stream of the laser spot is obtained based on the fitting formula of the laser profile: in, This is an estimate of the horizontal position of the laser spot at the center of the current frame. The fitting polynomial for the laser profile is given. H The height of the current frame image. The image data stream of the area to be tested. timestamp, Which frame of the image? The number of image frames; The gradient of the horizontal position data stream of the laser spot is calculated, and the times corresponding to the maximum and minimum gradient values ​​are obtained. These times are taken as the different boundary times. The gradient calculation formula is as follows: in, For the first k Horizontal position data of each laser spot For the first k- Horizontal position data of one laser spot For the first k- The maximum gradient value of the horizontal position data of a laser spot is The minimum value of the gradient is The maximum value corresponds to the time when The minimum value corresponds to the time when ; The position data of the measuring probe at different boundary moments are obtained from the motion data stream, and the measurement value of the part to be measured is obtained by subtracting the position data at different boundary moments. This includes: Using the motion data stream, the position data of the measuring probe at different boundary moments are estimated using Lagrange interpolation, where the Lagrange interpolation polynomial is: in, Represents the data stream of the grating ruler. The number of data in the grating ruler data stream. For time, Let the order of the Lagrange interpolation polynomial be . for Polynomial of degree: in, For the first i -1 grating ruler data point i= 1,2,..., n ; The measured value of the part to be measured is obtained by subtracting the position data at different boundary times: in, , For different boundary moments.

2. The measurement method of the automated workpiece inner wall measurement device adapted for assembly line production as described in claim 1, characterized in that, The structural frame (2) includes a portal frame; the image acquisition device (3) includes a camera.

3. The measurement method of the automated workpiece inner wall measurement device adapted for assembly line production as described in claim 1, characterized in that, The moving direction of the mobile platform (4) is perpendicular to the conveying direction of the conveying platform (1).

4. The measurement method of the automated workpiece inner wall measurement device adapted for assembly line production according to claim 1, characterized in that, The probe-type measuring device (5) includes a linear motion platform (51), a grating ruler (52), a measuring probe (53), and a connecting rod (54), wherein, The grating probe of the grating ruler (52) is connected to the slide of the linear motion platform (51) through a connector. The grating probe is used to detect the movement of the slide in real time to obtain the motion data stream of the measuring probe (53). The measuring probe (53) is connected to the slide table via the connecting rod (54), and the slide table is used to perform linear motion to drive the measuring probe (53) to perform insertion measurement.

5. The measurement method of the automated workpiece inner wall measurement device adapted for assembly line production according to claim 4, characterized in that, The measuring probe (53) includes a holder (531) and an image acquisition module (532), wherein, The retainer (531) is connected to the slide table; The image acquisition module (532) is fixed on the holder (531) and is used to acquire the image data stream of the inner wall of the part under test when the slide moves.

6. The measurement method of the automated workpiece inner wall measurement device adapted for assembly line production according to claim 5, characterized in that, The measuring probe (53) also includes a laser head (533), wherein, The laser head (533) is fixed on the holder (531), and the line of sight of the laser head (533) is at a certain angle to the line of sight of the image acquisition module (532) so that the image of the part to be tested is superimposed on the light spot of the laser head (533).

7. The measurement method of the automated workpiece inner wall measurement device adapted for assembly line production as described in claim 5, characterized in that, The measuring probe (53) also includes a micro switch, which is located directly below the holder (531).

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