Concentricity compensation method of special-shaped plug-in machine

Abstract

The invention discloses a concentricity compensation method of a special-shaped plug-in machine. The concentricity compensation method is suitable for compensating position deviation of a component installation position caused by a fact that a Z-axis connecting rod is in a slightly inclined state. The method comprises the following steps: recording gray level images of the bottom end of a Z-axis connecting rod when the Z-axis connecting rod rotates around an R axis by different angles through a camera, then obtaining central points of the gray level images at various angles, fitting the central points into an ellipse, calculating the rotation center of the R axis, and finally calculating the element center of the to-be-measured part based on the rotation angle and the difference value between the rotation center and the element center of the to-be-measured part. Therefore, the actual position of the element can be calculated so as to compensate the deviation of concentricity and realize accurate plug-in operation.

Description

Technical Field

[0001] The invention relates to the field of intelligent special-shaped plug-in machines, and in particular to a concentricity compensation method for special-shaped plug-in machines. Background Art

[0002] The plug-in machine is a mechanical device that automatically and standardly inserts some regular electronic components into the conductive through-holes of the printed circuit board. As a type of plug-in machine, the special-shaped plug-in machine can assemble some special-shaped components in an automated manner, greatly improving the assembly efficiency of special-shaped components. Among them, the special-shaped plug-in machine presses down the components through the Z-axis connecting rod, and installs the corresponding components on the PCB board in position to realize the automatic assembly of components. However, due to factors such as installation accuracy or mechanism deformation, the Z-axis connecting rod of the existing special-shaped plug-in machine will cause the Z-axis connecting rod to be not completely in a vertical state. In this case, the suction nozzle at the bottom of the Z-axis connecting rod will have a slight change in position after the Z-axis connecting rod rotates around the R-axis. At this time, when the Z-axis connecting rod rotates to insert components at different angles, the components will rotate around the R-axis rotation center, thereby generating position deviations, resulting in poor installation accuracy of the components. Therefore, how to solve the problem of component installation position deviation caused by the Z-axis connecting rod being in an incompletely vertical state has become an objective need. Summary of the invention

[0003] The invention provides a concentricity compensation method for a special-shaped plug-in machine, which is used to solve the problem that the installation position of components of the existing special-shaped plug-in machine is deviated due to the Z-axis connecting rod being in an incompletely vertical state.

[0004] To achieve the purpose of the present invention, the present invention provides a concentricity compensation method for a special-shaped plug-in machine, wherein the Z-axis connecting rod of the plug-in machine is in a slightly tilted state, and the method comprises the following steps:

[0005] a. Use a camera at a fixed position to record the grayscale image of the bottom end of the Z-axis connecting rod when the Z-axis connecting rod rotates at different angles around the R axis;

[0006] b. Processing the grayscale image, obtaining the center point of the grayscale image at each angle, and fitting the obtained center point into an ellipse;

[0007] c. Calculate the center of the ellipse and the rotation center of the R axis;

[0008] d. When inserting, the actual position of the component is calculated based on the difference between the rotation center of the R axis and the center of the component to be inserted and the rotation angle to compensate for the concentricity deviation and achieve precise insertion operation.

[0009] Furthermore, in step a, the Z-axis connecting rod rotates around the R-axis at an angle of -180 to 180 degrees, and when the Z-axis connecting rod rotates around the R-axis by 0 degrees, the position of the bottom end of the Z-axis connecting rod is the reference position.

[0010] Furthermore, in step b, the step of processing the image includes:

[0011] b11, performing Gaussian filtering on the image;

[0012] b12. Use the Canny operator to detect the edges in the grayscale image at each angle;

[0013] b13. Acquire all contours in the grayscale image according to the edge, and determine the center point coordinates of the grayscale image of the bottom end of the Z-axis connecting rod at various angles.

[0014] Further, step b12 includes:

[0015] b121, calculate the gradient magnitude and gradient direction of the image by applying the Sobel operator;

[0016] b122, scan the image, retain the local maximum point of the local gradient amplitude, and suppress the non-maximum value;

[0017] b123, set two thresholds to threshold the image that is not the maximum threshold;

[0018] b124. Further refine the image to remove irrelevant edge segments and disconnected edge segments, thereby obtaining the image edge.

[0019] Further, step b123 includes:

[0020] A high threshold and a low threshold are set respectively, wherein pixels with a gradient magnitude higher than the high threshold are marked as strong edges, and pixels with a gradient magnitude lower than the low threshold are marked as weak edges;

[0021] Starting from the strong edge pixels, the connected weak edge pixels are tracked and marked as strong edges until they can no longer be connected to new edge pixels.

[0022] Further, step b13 includes: obtaining all contours in the image according to the edge, obtaining the size and position of the circle using Houge transformation, and determining the center point coordinates of the bottom end of the Z-axis connecting rod at the current angle.

[0023] Furthermore, in step b, the step of fitting the acquired center point into an ellipse includes:

[0024] b21. Express the ellipse as a parametric equation:

[0025] (XXo ) 2 / a 2 +(YY o ) 2 / b 2 =1,

[0026] Where: (X o , Y o ) are the coordinates of the center of the ellipse, a and b are the major and minor axes of the ellipse respectively;

[0027] b22. Substitute the obtained center point coordinates into the parameter equation of step b21 to obtain the error function about the point:

[0028] [(X i -X 0 ) 2 / a 2 +(Y i -Y 0 ) 2 / a 2 -1] 2

[0029] Accumulate all functions to obtain the total error function; find the optimal (X o , Y o , a, b), minimize the total error;

[0030] b23, initialization parameters, take the average value of all points as the initial value of the ellipse center, calculate the distance from each point to the ellipse center, take the mean value of the farther points as the major axis, and the mean value of the closer points as the minor axis;

[0031] b24. Matrix calculation and optimization are performed through the Levenberg-Marquardt optimization algorithm, and the adjustment (X o ,Y o ,a,b), to minimize the total error function;

[0032] b25. When the total error function value is small enough, the elliptic equation is obtained.

[0033] Further, step d comprises:

[0034] When plug-in is performed, the difference between the rotation center of the R-axis and the center of the component to be plugged in is calculated through visual inspection. After the component is rotated, the actual position of the component to be plugged in is calculated based on the rotation angle and the corresponding difference between the rotation center and the center of the component to be plugged in, so as to compensate for the concentricity deviation and realize precise plug-in operation.

[0035] In some embodiments, in step c, when the Z axis is not parallel to the R axis, the rotation center of the R axis is linearly related to the height of the Z axis, and the rotation center of the R axis at the corresponding height is calculated based on the linear relationship between the position of the rotation center and the height of the Z axis.

[0036] Furthermore, when the Z axis is not parallel to the R axis, multiple rotation center data collection is performed at different heights of the Z axis, and the linear relationship between the X and Y coordinates of the R axis rotation center and the Z coordinate of the Z axis height is calculated, and then the rotation center of the R axis can be calculated based on the linear relationship based on the height of the Z axis.

[0037] The beneficial effects of the present invention are as follows: the present invention uses a camera to record the grayscale image of the bottom end of the Z-axis connecting rod when the Z-axis connecting rod rotates around the R-axis at different angles, then obtains the center point of the grayscale image at each angle, fits the center point into an ellipse, calculates the rotation center of the R-axis, and then based on the difference between the rotation angle and the rotation center and the component center of the test piece, the actual position of the component can be calculated to compensate for the concentricity deviation and realize precise plug-in operation.

[0038] On the other hand, when the Z-axis is not parallel to the R-axis, the rotation center of the R-axis can be calculated based on the height of the Z-axis according to the linear relationship between the Z-axis height and the R-axis rotation center. Then, based on the rotation angle and the difference between the rotation center and the component center of the test piece, the actual position of the component can be calculated, thereby achieving precise plug-in operation of components of different heights. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of the method of the present invention.

[0040] Figure 2 It is a schematic diagram of the Z-axis connecting rod rotating around the R-axis in Example 1 of the present invention.

[0041] Figure 3 It is the ellipse fitted in Example 1 of the present invention.

[0042] Figure 4 It is a schematic diagram of the side view structure of the Z-axis connecting rod of Example 2 of the present invention when rotating around the R-axis.

[0043] Figure 5 It is a schematic diagram of the front view structure of the Z-axis connecting rod of Example 2 of the present invention when rotating around the R-axis.

[0044] Figure 6 It is a schematic diagram of the rotation center position of the R axis when the Z axis is at different heights in Example 2 of the present invention. DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0046] Example 1

[0047] like Figure 1 As shown, the concentricity compensation method of the special-shaped insertion machine of this embodiment is used to compensate for the position deviation of the component installation position caused by the Z-axis connecting rod being in a slightly tilted state, wherein, Figure 2 As shown, the Z-axis connecting rod is in a slightly tilted state due to installation accuracy or being squeezed by the limit mechanism during rotation or being in a slightly bent state. When the insertion machine absorbs the components to be tested and the plug-in, its Z-axis rotates around the R-axis, and the Z-axis and the R-axis are parallel to each other. Specifically, the concentricity compensation method of the special-shaped insertion machine of this embodiment includes the following steps:

[0048] S110, recording, by means of a camera, grayscale images of the bottom end of the Z-axis connecting rod when the Z-axis connecting rod is rotated at different angles around the R-axis.

[0049] In this step, a high-precision industrial camera is used to record the grayscale image of the bottom end of the Z-axis connecting rod when it rotates around the R axis at different angles in a fixed position, which is convenient for subsequent single-channel grayscale image processing, simplifies the processing flow, reduces the amount of calculation, and greatly improves the speed and accuracy of image processing. In this embodiment, during the plug-in operation, the angle of rotation of the bottom end of the Z-axis connecting rod around the R axis is -180 to 180 degrees, and the position of the bottom end of the Z-axis connecting rod when the Z-axis connecting rod rotates 0 degrees around the R axis is used as the reference position.

[0050] S120, processing the grayscale image, obtaining the center point of the grayscale image at each angle, and fitting the obtained center point into an ellipse.

[0051] In this step, the grayscale images taken at different angles are processed to obtain a circle with a clear outline, and then the center point of the circle at each angle is obtained, and then each center point is fitted into an ellipse.

[0052] Specifically, the steps of processing the grayscale image include:

[0053] S121, performing Gaussian filtering on the image.

[0054] In this step, Gaussian filtering is performed on the image to reduce the variation of pixel values ​​in the image by weighted averaging, thereby blurring the image and reducing the impact of image noise.

[0055] S122, detecting edges in the grayscale image at each angle using the Canny operator.

[0056] This step includes:

[0057] S1221. Calculate the gradient magnitude and gradient direction of the image by applying the Sobel operator.

[0058] S1222. Scan the image, retain the local maximum point of the local gradient amplitude, and suppress non-maximum values.

[0059] In this step, the detected edge is refined by retaining the local maximum point of the local gradient amplitude and suppressing the non-maximum value, so that it matches the actual edge more accurately.

[0060] S1223. Set two thresholds and threshold the image that is not the maximum threshold.

[0061] In this step, two thresholds, i.e., a high threshold and a low threshold, are set to threshold the image after non-maximum suppression. Specifically, pixels with gradient magnitudes higher than the high threshold are marked as strong edges, and pixels with gradient magnitudes lower than the low threshold are marked as weak edges. Starting from the strong edge pixels, the connected weak edge pixels are tracked and marked as strong edges until they can no longer be connected to new edge pixels.

[0062] S1224: further refine the image to remove irrelevant edge segments and disconnected edge segments, thereby obtaining grayscale image edges at various angles.

[0063] S123, acquiring all contours in the grayscale image according to the edges, and determining the center point coordinates of the grayscale image of the bottom end of the Z-axis connecting rod at various angles.

[0064] In this step, all contours in the image are obtained based on the detected edges, and the size and position of the circle are obtained using Houge transformation. Figure 3 The circle shown in FIG. 1 and the center point coordinates of the bottom end of the Z-axis connecting rod at the current angle are determined. In this embodiment, the bottom end of the Z-axis connecting rod is at 0 degrees as an example. Figure 2 As shown in the figure, when the Z axis rotates 0 degrees around the R axis, the grayscale image of the bottom end of the Z axis connecting rod obtained by the camera is processed and obtained as follows Figure 3 The circle shown in Figure 1 is used to obtain the coordinates of the two edges of the grayscale image at 0 degrees (X1 0 , Y1 0 ) is (-0.1611, -0.091) and (X2 0 , Y2 0) is (0.0374, 0.1245), and then the coordinates of the center point of the bottom end of the Z-axis connecting rod at 0 degrees are obtained based on the two coordinates (X-0, Y-0). Then the coordinates of the center point of the bottom end of the Z-axis when the Z-axis rotates from -180 degrees to 180 degrees are obtained in the same way. In this embodiment, by recording the coordinates (X1, Y1) and (X2, Y2) of the two edges of the grayscale image at every 30 degrees from -180 degrees to 180 degrees, the recording results are shown in Table 1, and then the coordinates of the center point of the bottom end of the Z-axis at each angle are calculated based on the results in Table 1 (X1, Y1, Y2). i , Y i ).

[0065] Table 1 Coordinates of the center point at the bottom of the Z axis at different angles

[0066]

[0067] The steps of fitting the coordinates of the center point of the bottom end of the Z axis at each angle into an ellipse include:

[0068] S1241. Express the ellipse as a parametric equation:

[0069] (XX o ) 2 / a 2 +(YY o ) 2 / b 2 =1,

[0070] Where: (X o , Y o ) are the coordinates of the center of the ellipse, a and b are the major and minor axes of the ellipse respectively.

[0071] S1242, substituting the obtained center point coordinates into the parameter equation of step S1241 to obtain the error function about the point:

[0072] [(X i -X 0 ) 2 / a 2 +(Y i -Y 0 ) 2 / a 2 -1] 2

[0073] Accumulate all functions to obtain the total error function; find the optimal (X o , Y o , a, b), so that the total error is minimized.

[0074] S1243, initializing parameters, taking the average value of all points as the initial value of the ellipse center, calculating the distance from each point to the ellipse center, taking the mean value of the farther points as the major axis, and the mean value of the closer points as the minor axis.

[0075] S1244, use the Levenberg-Marquardt optimization algorithm to perform matrix calculation and optimization, and iteratively adjust (X o ,Y o ,a,b), to minimize the total error function;

[0076] S1245. When the total error function value is small enough, the ellipse equation is obtained. The ellipse obtained by fitting is as follows: Figure 3 shown.

[0077] S130, calculating the center of the ellipse and the rotation center of the R axis.

[0078] In this step, the center of the ellipse is calculated according to the ellipse equation obtained in step S1245. When the Z axis is parallel to the R axis, the center of the ellipse is the rotation center of the R axis.

[0079] S140. When inserting, the actual position of the component is calculated based on the difference between the rotation center of the R axis and the center of the component to be inserted and the rotation angle to compensate for the concentricity deviation and achieve precise insertion operation.

[0080] In this step, when plug-in is performed, the difference between the center of the component to be plugged in and the rotation center of the R axis is calculated through visual inspection. After the component is rotated, the corresponding rotation center is obtained according to the rotation angle, and then the difference between the center of the component to be plugged in and the corresponding rotation center is calculated. The actual position of the component to be plugged in can be calculated, thereby achieving precise plug-in operation.

[0081] Example 2

[0082] The concentricity compensation method of the special-shaped plug-in machine of this embodiment is suitable for compensating the position deviation of the component installation position caused by the Z-axis connecting rod being in a slightly tilted state, wherein the Z-axis connecting rod is in a slightly tilted state due to the installation accuracy or being squeezed by the limit mechanism during the rotation process or being in a slightly bent state. When the plug-in machine absorbs the components and plug-ins to be tested, its Z axis rotates around the R axis, and the Z axis is not parallel to the R axis. The concentricity compensation method of the special-shaped plug-in machine is the same as the compensation method of Example 1, except that the rotation center of the R axis in step S130 is calculated.

[0083] Specifically, Figure 4 , Figure 5 , Figure 6As shown in the figure, since the Z axis is not parallel to the R axis, when performing concentricity compensation, when the height of the material is different, the intersection point of the actual rotation center line of the R axis and the visual plane (i.e. the rotation center position) will change with the change of the height of the Z axis. Figure 6 As shown in the figure, the intersection of the R-axis rotation centerline and the focal plane is the rotation center in visual recognition. Since the R-axis is not parallel to the Z-axis, in production, when components of different heights are sucked for inspection, the Z-axis has different heights, and the R-axis also has different heights driven by the Z-axis, so the position of the rotation center on the focal plane will also be offset. In this case, using the same set of concentricity compensation data will produce errors.

[0084] Through geometric analysis, it can be known that the offset of the position of the R rotation center is linearly related to the change of the Z-axis height. The calculation of the rotation center of the Z-axis connecting rod in step S130 includes:

[0085] The R-axis rotation center is calculated based on the linear relationship between the position of the R-axis rotation center and the height of the Z-axis.

[0086] Specifically, Figure 6 As shown, multiple rotation center data collections are performed at different heights of the R axis, and the linear relationship between the X, Y coordinates of the rotation center of the R axis connecting rod and the Z coordinate of the Z axis height is calculated, so that the rotation center can be calculated according to the height of the Z axis and the linear relationship. In this embodiment, the rotation center data collection is performed twice at a height 1 of 2.5 mm and a height 2 of 25 mm on the Z axis, and the collected data is shown in Table 2. Then, the linear relationship between the X, Y coordinates of the rotation center of the Z axis connecting rod and the Z coordinate of the Z axis height is obtained based on the X, Y coordinates and Z coordinate data collected twice. When the plug-in operation is performed, the rotation center of the R axis can be calculated based on the linear relationship based on the height of the Z axis. Then, step S140 is executed, so that the corresponding rotation center is calculated using the linear difference method according to the Z axis height during detection and plug-in, and compensation calculation is performed to achieve accurate concentricity compensation suitable for components of different heights.

[0087] Table 2Z axis rotation center at different heights

[0088]

[0089] The concentricity compensation method of the special-shaped insertion machine in this embodiment uses a camera to record the grayscale image of the bottom end of the Z-axis connecting rod when the Z-axis connecting rod rotates around the R-axis at different angles, and then obtains the center point of the grayscale image at each angle, fits the center point into an ellipse, calculates the rotation center of the R-axis, and then based on the rotation angle and the difference between the rotation center and the component center of the test piece, the actual position of the component can be calculated to achieve precise insertion operation.

[0090] On the other hand, when the Z-axis is not parallel to the R-axis, the rotation center of the R-axis can be calculated based on the height of the Z-axis according to the linear relationship between the Z-axis height and the rotation center. Then, based on the rotation angle and the difference between the rotation center and the component center of the device under test, the actual position of the component can be calculated, thereby achieving precise plug-in operation of components of different heights.

[0091] Although the present invention is disclosed through the above embodiments, the protection scope of the present invention is not limited thereto. Without departing from the concept of the present invention, any deformation, replacement, etc. made to the above components shall fall within the scope of the claims of the present invention.

Claims

1. A concentricity compensation method for a special-shaped insertion machine, wherein the Z-axis connecting rod of the insertion machine is in a slightly tilted state, characterized in that: The method comprises the following steps: a. Use a camera at a fixed position to record the grayscale image of the bottom end of the Z-axis connecting rod when the Z-axis connecting rod rotates at different angles around the R axis; b. Processing the grayscale image, obtaining the center point of the grayscale image at each angle, and fitting the obtained center point into an ellipse; c. Calculate the center of the ellipse and the rotation center of the R axis; d. When inserting, the actual position of the component is calculated based on the difference between the rotation center of the R axis and the center of the component to be inserted and the rotation angle to compensate for the concentricity deviation and achieve precise insertion operation.

2. The concentricity compensation method of a special-shaped insertion machine according to claim 1, characterized in that: In step a, the Z-axis connecting rod rotates around the R-axis at an angle of -180 to 180 degrees. When the Z-axis connecting rod rotates around the R-axis by 0 degrees, the position of the bottom end of the Z-axis connecting rod is the reference position.

3. The concentricity compensation method of a special-shaped insertion machine according to claim 1, characterized in that: In step b, the step of processing the image includes: b11, performing Gaussian filtering on the image; b12. Use the Canny operator to detect the edges in the grayscale image at each angle; b13. Acquire all contours in the grayscale image according to the edge, and determine the center point coordinates of the grayscale image of the bottom end of the Z-axis connecting rod at various angles.

4. The concentricity compensation method of a special-shaped insertion machine according to claim 3, characterized in that: Step b12 includes: b121, calculate the gradient magnitude and gradient direction of the image by applying the Sobel operator; b122, scan the image, retain the local maximum point of the local gradient amplitude, and suppress the non-maximum value; b123, set two thresholds to threshold the image that is not the maximum threshold; b124. Further refine the image to remove irrelevant edge segments and disconnected edge segments, thereby obtaining the image edge.

5. The concentricity compensation method of a special-shaped insertion machine according to claim 4, characterized in that: Step b123 includes: A high threshold and a low threshold are set respectively, wherein pixels with a gradient magnitude higher than the high threshold are marked as strong edges, and pixels with a gradient magnitude lower than the low threshold are marked as weak edges; Starting from the strong edge pixels, the connected weak edge pixels are tracked and marked as strong edges until they can no longer be connected to new edge pixels.

6. The concentricity compensation method of a special-shaped insertion machine according to claim 3, characterized in that: Step b13 includes: obtaining all contours in the image according to the edge, obtaining the size and position of the circle using Houge transformation, and determining the center point coordinates of the bottom end of the Z-axis connecting rod at the current angle.

7. The concentricity compensation method of a special-shaped insertion machine according to claim 1, characterized in that: In step b, the step of fitting the acquired center point into an ellipse includes: b21. Express the ellipse as a parametric equation: (XX o ) 2 / to 2 +(YY o ) 2 / b 2 =1, Where: (X o , Y o ) are the coordinates of the center of the ellipse, a and b are the major and minor axes of the ellipse respectively; b22. Substitute the obtained center point coordinates into the parameter equation of step b21 to obtain the error function about the point: [(X i -X0) 2 / to 2 +(And i -Y0) 2 / to 2 -1] 2 Accumulate all functions to obtain the total error function; find the optimal (X o , Y o , a, b), minimize the total error; b23, initialization parameters, take the average value of all points as the initial value of the ellipse center, calculate the distance from each point to the ellipse center, take the mean value of the farther points as the major axis, and the mean value of the closer points as the minor axis; b24. Matrix calculation and optimization are performed through the Levenberg-Marquardt optimization algorithm, and the adjustment (X o ,Y o ,a,b), to minimize the total error function; b25. When the total error function value is small enough, the elliptic equation is obtained.

8. The concentricity compensation method of a special-shaped insertion machine according to claim 1, characterized in that: Step d includes: When plug-in is performed, the difference between the rotation center of the R-axis and the center of the component to be plugged in is calculated through visual inspection. After the component is rotated, the actual position of the component to be plugged in is calculated based on the rotation angle and the corresponding difference between the rotation center and the center of the component to be plugged in, so as to compensate for the concentricity deviation and realize precise plug-in operation.

9. The concentricity compensation method of a special-shaped insertion machine according to claim 1, characterized in that: In step c, when the Z axis is not parallel to the R axis, the rotation center of the R axis is linearly related to the height of the Z axis, and the rotation center of the R axis at the corresponding height is calculated based on the linear relationship between the position of the rotation center and the height of the Z axis.

10. The concentricity compensation method of a special-shaped insertion machine according to claim 9, characterized in that: When the Z axis is not parallel to the R axis, multiple rotation center data collection is performed at different heights of the Z axis, and the linear relationship between the X and Y coordinates of the R axis rotation center and the Z coordinate of the Z axis height is calculated. Then, the rotation center of the R axis can be calculated based on the linear relationship based on the height of the Z axis.

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