Electrical field parameter regulation method and system for spray booth

Abstract

The present application relates to the technical field of electrostatic spraying electric field parameter regulation, in particular to an electric field parameter regulation method and system for a spraying bin, comprising collecting feedback current and high-voltage output voltage of an auxiliary electrode high-voltage power supply loop; acquiring temperature and humidity data; continuously collecting images of a region between the auxiliary electrode and the spraying bin wall and performing image enhancement processing to obtain a powder accumulation layer enhancement image sequence, and performing segmentation, edge contour extraction and curve fitting to obtain powder accumulation layer accumulation front profile and gap distribution, and combining high-voltage output voltage to calculate local electric field intensity distribution; correcting equivalent line conductivity parameters according to temperature and humidity data, and calculating a conduction current component with the local electric field intensity distribution; subtracting the conduction current component from the feedback current to obtain a corrected corona current component, and regulating the high-voltage output voltage accordingly. The present application effectively identifies corona current from feedback current, and improves the accuracy of dynamic feedback regulation of spraying bin electric field parameters.

Description

Technical Field

[0001] This invention relates to the field of electric field parameter control technology in electrostatic spraying, specifically to a method and system for controlling electric field parameters in a spraying chamber. Background Technology

[0002] The semi-enclosed spray booth is not completely isolated from the external environment, and the temperature and humidity inside the booth are prone to fluctuations due to external environmental factors and spray airflow during operation. To ensure that the paint particles are fully charged and adhere evenly to the surface of the object being coated, an auxiliary electrode is installed inside the spray booth. A high-voltage voltage is applied to it through a high-voltage power supply circuit, forming a corona discharge electric field between the auxiliary electrode and the booth wall. The high-voltage output voltage is dynamically adjusted based on the feedback current of the high-voltage power supply circuit to balance discharge stability and spray quality.

[0003] However, during the spraying process, some paint particles inevitably fail to deposit onto the substrate, instead adhering and accumulating in the area between the auxiliary electrode and the spray bin wall, forming a powder layer. As a powder material, the conductivity of this powder layer changes with the ambient temperature and humidity. Under the influence of an electric field, the powder layer generates a current along its path to the spray bin wall, and this current coexists with the corona current of the auxiliary electrode in the same power supply circuit, together forming the detected feedback current. This makes it difficult for the feedback current to accurately reflect the corona discharge state of the auxiliary electrode, leading to deviations in the dynamic feedback control of the electric field parameters. Summary of the Invention

[0004] (1) Technical problems to be solved The purpose of this invention is to provide a method and system for controlling electric field parameters in a spraying chamber, in order to solve the problem that in a semi-enclosed spraying chamber, during spraying operations, a powder accumulation layer forms between the auxiliary electrode and the chamber wall, and the conductivity changes caused by temperature and humidity fluctuations within the chamber cause the current flowing through the powder accumulation layer and the corona current to be in the same power supply circuit, resulting in the feedback current being difficult to accurately reflect the discharge state and causing deviations in the dynamic control of electric field parameters.

[0005] (2) Technical solution To achieve the above objectives, in one aspect, the present invention provides a method for controlling the electric field parameters of a spray coating chamber, the method comprising: The feedback current of the high-voltage power supply circuit of the auxiliary electrode is collected, and the high-voltage output voltage of the high-voltage power supply circuit is obtained; the temperature and humidity data in the spraying chamber are acquired; continuous image acquisition and image enhancement processing are performed on the area between the auxiliary electrode and the wall of the spraying chamber to obtain the powder layer enhancement image sequence.

[0006] The enhanced image sequence of the powder accumulation layer is segmented frame by frame to obtain the powder accumulation layer region; the edge contour facing the spraying hopper wall in the powder accumulation layer region is extracted; multiple discrete points are selected along the edge contour to obtain the discrete point set of the edge contour; curve fitting is performed on the discrete point set of the edge contour to obtain the powder accumulation front contour; the gap value between each point on the powder accumulation front contour and the spraying hopper wall is calculated to obtain the gap distribution; based on the gap distribution and the high voltage output voltage, the local electric field intensity distribution between the powder accumulation front and the spraying hopper wall is calculated.

[0007] The preset equivalent linear conductivity reference parameters of the powder accumulation layer are corrected based on temperature and humidity data to obtain the corrected equivalent linear conductivity parameters. Based on the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, the current density distribution on the conduction path from the powder accumulation front to the spraying chamber wall is calculated, and the current is integrated along the arc length direction of the powder accumulation front profile to obtain the conduction current component.

[0008] The corrected corona current component is obtained by calculating the difference between the feedback current and the conduction current component; when the corrected corona current component exceeds the preset corona current range, the high voltage output voltage is adjusted.

[0009] Furthermore, the method for continuously acquiring images of the area between the auxiliary electrode and the spraying chamber wall and performing image enhancement processing to obtain an enhanced image sequence of the powder accumulation layer includes: Based on the distribution of grayscale differences between adjacent image frames in an image frame sequence obtained from continuous image acquisition, a set of dynamic interference pixels is identified.

[0010] The grayscale values ​​of pixels in the dynamic interference pixel set are replaced with the grayscale values ​​of the corresponding pixels in the adjacent previous image frame to obtain the background reference image.

[0011] Based on the gray-level gradient distribution within the neighborhood of pixels in the background reference image, a set of pixels with halo interference is identified; inverse distance weighted interpolation is performed on the set of pixels with halo interference to obtain a halo-suppressed image.

[0012] Calculate the maximum and minimum gray values ​​within the neighborhood of each pixel in the halo-suppressed image to obtain the local gray range; perform linear stretching based on the local gray range to obtain the powder layer enhancement image, thus forming a powder layer enhancement image sequence.

[0013] Furthermore, the method for identifying a set of dynamic interference pixels based on the grayscale difference distribution of adjacent image frames in an image frame sequence obtained from continuous image acquisition includes: Calculate the grayscale difference between the corresponding pixels of the current image frame and the adjacent previous image frame to obtain an inter-frame difference map; statistically analyze the distribution of grayscale differences in the inter-frame difference map to obtain a difference grayscale histogram; calculate the inter-class variance of each grayscale level in the difference grayscale histogram, and determine the grayscale level corresponding to the maximum value as the dynamic judgment threshold.

[0014] Pixels whose grayscale difference in the inter-frame difference image exceeds the dynamic judgment threshold are marked as dynamic interference pixels, thus obtaining a set of dynamic interference pixels.

[0015] Furthermore, the method of replacing the grayscale values ​​of pixels in the dynamic interference pixel set with the grayscale values ​​of corresponding pixels in the adjacent previous image frame to obtain the background reference image includes: Set the background grayscale value of each pixel to the grayscale value of the corresponding pixel in the first frame image, and set the background drift rate of each pixel to zero.

[0016] For pixels in the current image frame that do not belong to the set of dynamic interference pixels, calculate the difference between the gray value of the pixel in the current image frame and the corresponding background gray value; based on the difference between the gray value of the pixel in the current image frame and the corresponding background gray value, update the corresponding background drift rate using a cumulative averaging method to obtain the updated background drift rate; update the corresponding background gray value based on the updated background drift rate to obtain the updated background gray value.

[0017] For a pixel in the current image frame that belongs to the set of dynamic interference pixels, calculate the sum of the corresponding background gray value and the corresponding background drift rate as the replacement value; replace the gray value of the pixel in the current image frame with the replacement value to obtain the background reference image.

[0018] Further, the method for updating the corresponding background drift rate by using a cumulative averaging method based on the difference between the grayscale value of a pixel in the current image frame and the corresponding background grayscale value, to obtain the updated background drift rate, includes: Calculate the ratio of the number of pixels in the set of dynamic interference pixels in the current image frame to the total number of pixels in the current image frame to obtain the proportion of dynamic interference points; determine the proportion of dynamic interference points as the update weight; calculate the difference between the gray value of a pixel in the current image frame and the corresponding gray value of the background, and the deviation of the background drift rate to obtain the rate deviation; sum the product of the update weight and the rate deviation with the background drift rate to determine the updated background drift rate.

[0019] Furthermore, the method for identifying the set of halo-interference pixels based on the gray-level gradient distribution within the neighborhood of pixels in the background reference image includes: Based on the relative positional calibration relationship between the auxiliary electrode and the spraying chamber wall, the imaging position of the auxiliary electrode is determined in the background reference image; the gray-level gradient values ​​in the neighborhood of the pixel in the background reference image are calculated to obtain the gradient distribution map; based on the radial distance between the pixel and the imaging position, the mean value of the gray-level gradient values ​​in the gradient distribution map is calculated piecewise to obtain the radial gradient distribution curve.

[0020] Calculate the mean difference between adjacent segments on the radial gradient distribution curve to obtain the radial gradient rate of change distribution; determine the radial distance corresponding to the segment with the largest difference in the radial gradient rate of change distribution as the halo influence radius; mark the pixels in the background reference image whose radial distance from the imaging position is less than the halo influence radius as halo interference pixels to obtain the halo interference pixel set.

[0021] Furthermore, the method for obtaining the profile of the powder accumulation front by curve fitting the discrete point set of the edge contour includes: Randomly select a subset of points with the same number of points from the discrete point set of the edge contour; perform curve fitting on each subset of points to obtain the corresponding candidate fitting curves; calculate the deviation of each point in the discrete point set of the edge contour to each candidate fitting curve to obtain the deviation distribution corresponding to each candidate fitting curve.

[0022] Calculate the median of the deviation for each deviation distribution, and calculate the median of the absolute value of the difference between each deviation and the corresponding median of the deviation in each deviation distribution. Then, determine the sum of the median of the deviation and the median of the absolute deviation for each deviation distribution as the inlier threshold for the deviation distribution.

[0023] Points whose deviations are less than the corresponding inlier determination threshold in each deviation distribution are identified as the corresponding inlier set.

[0024] The set of interior points with the largest number of points is selected for curve fitting to obtain the profile of the front edge of the powder accumulation layer.

[0025] Furthermore, the method for calculating the local electric field intensity distribution between the powder accumulation front and the spraying bin wall based on the gap distribution and the high-voltage output voltage includes: Calculate the mean value of the gap at each point in the gap distribution to obtain the average gap value. ; Calculate the first The difference between the gap value at each point and the gap value between two adjacent points yields the gap gradient value. According to the first Point gap value , gap gradient value With average gap value Calculate local morphological coefficients .

[0026] Based on local morphological coefficients With the preset field strength concentration factor Calculate the first Local electric field intensity at each point Based on the local electric field intensity at each point, the local electric field intensity distribution between the front edge of the powder accumulation layer and the wall of the spraying bin is formed.

[0027] Further, the method for calculating the current density distribution along the conduction path from the powder accumulation front to the spraying hopper wall based on the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, and integrating along the arc length direction of the powder accumulation front profile to obtain the conduction current component includes: The local electric field intensity distribution is related to the contour of the front edge of the powder accumulation layer. Multiplying the local electric field intensity value at the i-th point by the corrected equivalent linear conductance parameter yields the i-th point. The current density value per unit arc length on the conduction path at each point ; Calculate the first [missing information] on the profile of the front edge of the powder accumulation layer The arc length between each point and its two adjacent points is used to obtain the arc length interval. Based on current density value Interval with arc length The conduction current components were calculated. .

[0028] Based on the same inventive concept, in another aspect, the present invention also provides an electric field parameter control system for a spray coating chamber, the system comprising: The data acquisition module is used to acquire the feedback current of the high-voltage power supply circuit of the auxiliary electrode, obtain the high-voltage output voltage of the high-voltage power supply circuit; acquire the temperature and humidity data in the spraying chamber; and continuously acquire and enhance images of the area between the auxiliary electrode and the wall of the spraying chamber to obtain an enhanced image sequence of the powder accumulation layer.

[0029] The electric field calculation module is used to perform frame-by-frame image segmentation on the enhanced image sequence of the powder accumulation layer to obtain the powder accumulation layer region; extract the edge contour of the powder accumulation layer region facing the spraying hopper wall; select multiple discrete points along the edge contour to obtain the discrete point set of the edge contour; perform curve fitting on the discrete point set of the edge contour to obtain the powder accumulation front contour; calculate the gap value between each point on the powder accumulation front contour and the spraying hopper wall to obtain the gap distribution; and calculate the local electric field intensity distribution between the powder accumulation front and the spraying hopper wall based on the gap distribution and the high voltage output voltage.

[0030] The conduction current calculation module is used to correct the preset equivalent linear conductivity reference parameters of the powder accumulation layer based on temperature and humidity data to obtain the corrected equivalent linear conductivity parameters; based on the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, the current density distribution on the conduction path from the powder accumulation front to the spraying bin wall is calculated, and the current density is integrated along the arc length direction of the powder accumulation front profile to obtain the conduction current component.

[0031] The voltage regulation module is used to calculate the difference between the feedback current and the conduction current components to obtain the corrected corona current component; when the corrected corona current component exceeds the preset corona current range, the high voltage output voltage is regulated.

[0032] (3) Beneficial effects Compared with the prior art, the beneficial effects of the present invention are: 1. The contour and gap distribution of the powder accumulation front are obtained by image acquisition. The local electric field intensity distribution and conduction current components are calculated by combining the high voltage output voltage and the corrected equivalent linear conductivity parameters. The corrected corona current component is separated from the feedback current to regulate the high voltage output voltage, effectively identify the corona current, and improve the accuracy of electric field parameter regulation.

[0033] 2. A background reference image is obtained by removing the set of dynamic interference pixels through inter-frame difference map. A halo-suppressed image is obtained by suppressing the set of halo interference pixels according to the gray-level gradient distribution. The enhanced image sequence of the powder layer is obtained by linear stretching of the local gray-level range, which improves the extraction accuracy of the contour of the powder layer accumulation front and makes the gap distribution and electric field parameter calculation more reliable. Attached Figure Description

[0034] Figure 1 This is a flowchart of the electric field parameter control method for a spraying chamber according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the module composition of the electric field parameter control system for the spraying chamber in Embodiment 2 of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Before giving examples, it is necessary to describe the application scenarios of the present invention. The present invention is applicable to electrostatic spraying scenarios in semi-enclosed spraying chambers. The workpiece is sent into the spraying chamber for electrostatic spraying. An auxiliary electrode is pre-deployed in the chamber to charge the paint particles. During the operation of the auxiliary electrode, a powder layer gradually accumulates on its surface.

[0037] Example 1: As Figure 1 As shown, this embodiment provides a method for controlling the electric field parameters of a spray coating chamber, the method comprising: S1. Collect the feedback current of the high-voltage power supply circuit of the auxiliary electrode and obtain the high-voltage output voltage of the high-voltage power supply circuit; acquire the temperature and humidity data in the spraying chamber; continuously acquire images of the area between the auxiliary electrode and the wall of the spraying chamber and perform image enhancement processing to obtain the powder accumulation layer enhanced image sequence.

[0038] The method for continuously acquiring and enhancing images of the area between the auxiliary electrode and the spraying chamber wall to obtain an enhanced image sequence of the powder accumulation layer includes: Based on the distribution of grayscale differences between adjacent image frames in an image frame sequence obtained from continuous image acquisition, a set of dynamic interference pixels is identified.

[0039] The method for identifying a set of dynamic interference pixels based on the distribution of grayscale differences between adjacent image frames in an image frame sequence obtained from continuous image acquisition includes: Calculate the grayscale difference between the corresponding pixels of the current image frame and the adjacent previous image frame to obtain an inter-frame difference map; statistically analyze the distribution of grayscale differences in the inter-frame difference map to obtain a difference grayscale histogram; calculate the inter-class variance of each grayscale level in the difference grayscale histogram, and determine the grayscale level corresponding to the maximum value as the dynamic judgment threshold.

[0040] Pixels whose grayscale difference in the inter-frame difference image exceeds the dynamic judgment threshold are marked as dynamic interference pixels, thus obtaining a set of dynamic interference pixels.

[0041] For example, the feedback current is acquired by a current sensor installed in the high-voltage power supply circuit of the auxiliary electrode. The current sensor has a range of 0 to 500 μA and a sampling frequency of 1 kHz. The acquired feedback current is 385 μA. The high-voltage output voltage is acquired by a voltage sensor installed at the output end of the high-voltage power supply circuit. The voltage sensor has a range of 0 to 80 kV and a sampling frequency synchronized with the current sensor. The acquired high-voltage output voltage is 45 kV. The temperature and humidity data inside the spray booth are acquired by a temperature and humidity sensor installed inside the spray booth. The temperature and humidity sensor acquires data once every 30 seconds. The acquired temperature and humidity data inside the spray booth are 28°C and 65% relative humidity.

[0042] The image acquisition device for continuously acquiring images of the area between the auxiliary electrode and the spraying hopper wall is an industrial camera with a resolution of 1280 pixels × 720 pixels and a frame rate of 25 fps. The image acquisition device is fixedly installed facing the area between the auxiliary electrode and the spraying hopper wall, and outputs grayscale images with a grayscale range of 0 to 255 frame by frame, forming an image frame sequence; each image frame in the image frame sequence is numbered according to the acquisition time sequence as frame 1, frame 2, and so on. Frame, the current image frame is the [frame number missing]. Frame, the adjacent previous image frame is the 1st frame. The acquisition time interval between adjacent image frames is 40ms. The change in the thickness of the powder layer within the 40ms time interval is less than the change in grayscale generated by the paint particles disturbed by airflow and the corona discharge halo within the 40ms time interval. The high amplitude part of the grayscale difference between adjacent image frames corresponds to the paint particles disturbed by airflow and the corona discharge halo.

[0043] No. The coordinates in the frame image are The pixel grayscale value , No. The coordinates in the frame image are The pixel grayscale value The coordinates in the inter-frame difference map are pixel grayscale difference .

[0044] The total number of pixels in the inter-frame difference image is 1280 × 720 = 921600. (Grayscale levels) The value range is an integer from 0 to 255. Represents the grayscale difference in the inter-frame difference image. equal to grayscale The number of pixels, the difference grayscale histogram is composed of grayscale levels and the corresponding number of pixels constitute.

[0045] The dividing points of the difference grayscale histogram are: , The value range is an integer from 0 to 254, and the gray level in the difference gray-scale histogram is 0 to 254. The corresponding pixels are classified into the first category, grayscale. Pixels corresponding to values ​​up to 255 are classified as the second category. The proportion of pixels in the first category to the total number of pixels in the inter-frame difference map (921,600) is [percentage missing]. The proportion of the second type of pixels to the total number of 921,600 pixels in the inter-frame difference map is: , and satisfy The mean value of the grayscale difference of pixels in the first category is The mean value of the grayscale difference of pixels in the second category is grayscale Corresponding inter-class variance .

[0046] Iterate through integers from 0 to 254 and calculate the corresponding inter-class variance. inter-class variance The gray level corresponding to the maximum value is determined as the dynamic judgment threshold. In the difference gray-level histogram, pixels with gray levels 0 to 18 represent pixels with small gray-level changes in adjacent image frames within the area containing the spray hopper wall and powder accumulation layer. Pixels with gray levels 19 to 255 represent pixels with large gray-level changes in adjacent image frames within the area containing paint particles affected by airflow disturbance and corona discharge halo. The inter-class variance... In grayscale The maximum value is obtained when the gray level is equal to 18, and the gray level of 18 is determined as the dynamic judgment threshold.

[0047] The grayscale difference in the inter-frame difference image Pixels exceeding the dynamic judgment threshold are marked as dynamic interference pixels, resulting in a set of dynamic interference pixels. The set of dynamic interference pixels contains 9216 pixels, which is 1% of the total number of pixels in the inter-frame difference map of 921600.

[0048] The grayscale values ​​of pixels in the dynamic interference pixel set are replaced with the grayscale values ​​of the corresponding pixels in the adjacent previous image frame to obtain the background reference image.

[0049] The method for replacing the gray values ​​of pixels in the dynamic interference pixel set with the gray values ​​of corresponding pixels in the adjacent previous image frame to obtain a background reference image includes: Set the background grayscale value of each pixel to the grayscale value of the corresponding pixel in the first frame image, and set the background drift rate of each pixel to zero.

[0050] For pixels in the current image frame that do not belong to the set of dynamic interference pixels, calculate the difference between the gray value of the pixel in the current image frame and the corresponding gray value of the background; based on the difference between the gray value of the pixel in the current image frame and the corresponding gray value of the background, update the corresponding background drift rate by averaging to obtain the updated background drift rate.

[0051] The method for updating the background drift rate by using a cumulative averaging method based on the difference between the grayscale value of a pixel in the current image frame and the corresponding background grayscale value, to obtain the updated background drift rate, includes: Calculate the ratio of the number of pixels in the set of dynamic interference pixels in the current image frame to the total number of pixels in the current image frame to obtain the proportion of dynamic interference points; determine the proportion of dynamic interference points as the update weight; calculate the difference between the gray value of a pixel in the current image frame and the corresponding gray value of the background, and the deviation of the background drift rate to obtain the rate deviation; sum the product of the update weight and the rate deviation with the background drift rate to determine the updated background drift rate.

[0052] The corresponding background grayscale value is updated based on the updated background drift rate to obtain the updated background grayscale value.

[0053] For a pixel in the current image frame that belongs to the set of dynamic interference pixels, calculate the sum of the corresponding background gray value and the corresponding background drift rate as the replacement value; replace the gray value of the pixel in the current image frame with the replacement value to obtain the background reference image.

[0054] For example, the initial value of the background grayscale is the grayscale value of the corresponding pixel in the first frame image, where the first frame image is the first frame in the image frame sequence, and the initial value of the background drift rate is zero; the coordinates are... The grayscale value of the pixel in the first frame image is The corresponding background grayscale value is The corresponding background drift rate is ,Right now .

[0055] The ratio of the number of pixels in the set of dynamic interference pixels in the current image frame to the total number of pixels in the current image frame (921,600) is calculated to obtain the proportion of dynamic interference points. The proportion of dynamic interference points This is determined to be a weight update. The current image frame is the [frame number missing]. Frame, number The set of dynamic interference pixels corresponding to the frame contains 9216 pixels, and the proportion of dynamic interference pixels is as follows: The value is 9216 / 921600 = 0.01.

[0056] For a pixel in the current image frame that does not belong to the set of dynamic interference pixels, the coordinates are... The pixel in the first The grayscale value in the frame image The corresponding background grayscale value is the first Background grayscale value corresponding to the frame The corresponding background drift rate is the first Background drift rate corresponding to the frame rate deviation .

[0057] Updated background drift rate .

[0058] Percentage of dynamic interference points The larger the value, the better the coordinates. The greater the adjustment range of the background drift rate corresponding to the pixel, the faster the background grayscale value can follow the overall grayscale shift caused by the environment during the period of intensified airflow disturbance of coating particles and corona discharge halo; the proportion of dynamic interference points The smaller the value, the better. The smaller the adjustment range of the background drift rate corresponding to the pixel, the better the suppression of the influence of random noise on the background drift rate.

[0059] Updated background grayscale values .

[0060] Coordinates are The pixels are updated frame by frame from the first image to update the background grayscale value and background drift rate. Background grayscale value corresponding to the frame It is 92nd, the number Background drift rate corresponding to the frame The value is 0.3, and the coordinates are... The pixel does not belong to the set of dynamic interference pixels corresponding to the current image frame. The coordinates in the frame image are pixel grayscale value The rate deviation is 93. Updated background drift rate Updated background grayscale values .

[0061] For pixels in the current image frame that belong to the set of dynamically disturbed pixels, the sum of the corresponding background grayscale value and the corresponding background drift rate is used as the replacement value. .

[0062] Replace the grayscale value of each pixel in the current image frame with the replacement value. This yields the background reference image. The coordinates are... When a pixel belongs to the set of dynamic interference pixels corresponding to the current image frame, the first... Background grayscale value corresponding to the frame With the Background grayscale value corresponding to the frame Same, the first Background drift rate corresponding to the frame With the Background drift rate corresponding to the frame Same, used for the first In frame image processing, it is used as the corresponding background grayscale value and the corresponding background drift rate.

[0063] Coordinates are The pixels are updated frame by frame from the first image to update the background grayscale value and background drift rate. Background grayscale value corresponding to the frame For 150, the number Background drift rate corresponding to the frame The value is 0.5, and the coordinates are... The pixel belongs to the set of dynamic interference pixels corresponding to the current image frame, and the replacement value is... The coordinates in the background reference image are The pixel grayscale value is 150.5.

[0064] Identify the set of pixels that cause halo interference based on the gray-level gradient distribution within the neighborhood of pixels in the background reference image.

[0065] The method for identifying a set of halo-interference pixels based on the gray-level gradient distribution within the neighborhood of pixels in a background reference image includes: Based on the relative positional calibration relationship between the auxiliary electrode and the spraying chamber wall, the imaging position of the auxiliary electrode is determined in the background reference image; the gray-level gradient values ​​in the neighborhood of the pixel in the background reference image are calculated to obtain the gradient distribution map; based on the radial distance between the pixel and the imaging position, the mean value of the gray-level gradient values ​​in the gradient distribution map is calculated piecewise to obtain the radial gradient distribution curve.

[0066] Calculate the mean difference between adjacent segments on the radial gradient distribution curve to obtain the radial gradient rate of change distribution; determine the radial distance corresponding to the segment with the largest difference in the radial gradient rate of change distribution as the halo influence radius; mark the pixels in the background reference image whose radial distance from the imaging position is less than the halo influence radius as halo interference pixels to obtain the halo interference pixel set.

[0067] The halo-interference pixel set is subjected to inverse distance weighted interpolation to obtain a halo-suppressed image.

[0068] Calculate the maximum and minimum gray values ​​within the neighborhood of each pixel in the halo-suppressed image to obtain the local gray range; perform linear stretching based on the local gray range to obtain the powder layer enhancement image, thus forming a powder layer enhancement image sequence.

[0069] For example, after the image acquisition device is fixedly installed, a static background image without airflow disturbance from paint particles is pre-acquired. The edge contour of the auxiliary electrode in the static background image is identified, and the geometric center coordinates of the area enclosed by the edge contour are determined as the imaging position of the auxiliary electrode in the background reference image, which is determined by the relative position calibration relationship between the auxiliary electrode and the spraying chamber wall. The imaging position coordinates are... .

[0070] The coordinates in the background reference image are The grayscale value of the pixel is denoted as The neighborhood of a pixel is defined by coordinates. A window centered at a point with sides of 3 pixels, where 3 pixels on each side represents the coordinates needed to calculate the grayscale gradient. The minimum neighborhood range of horizontally and vertically adjacent pixels. Horizontal gradient. With longitudinal gradient satisfy: .

[0071] coordinate Corresponding grayscale gradient value The grayscale gradient values ​​corresponding to each pixel in the background reference image. This forms a gradient distribution map. (Coordinates) With imaging position radial distance between .

[0072] The radial distance is divided into segments of 10 pixels each, the first segment... The radial distance range corresponding to the segment is: The segment range covers the pixel with the largest radial distance from the imaging position in the background reference image. The segment width is 10 pixels, which is greater than the side length of the neighborhood for calculating the grayscale gradient by 3 pixels, to avoid overlapping neighborhood ranges of adjacent segments that would cause the mean to be counted repeatedly. Mean gray-level gradient corresponding to each segment For the radial distance in the gradient distribution map falling into the first... The arithmetic mean of the grayscale gradient values ​​corresponding to the pixels within the segmented range, and the mean grayscale gradient value corresponding to each segment. By segment number The arrangement forms a radial gradient distribution curve. The mean gray-level gradient values ​​corresponding to the 1st to 10th segments are 46, 44, 41, 37, 33, 15, 13, 12, 11, and 11, respectively.

[0073] No. Segmentation and the first The difference in mean between segments satisfy: .

[0074] The absolute value of the mean difference is used to avoid the mean difference becoming negative due to the gray-level gradient mean decreasing with increasing radial distance, which could affect the determination of the maximum value. The mean difference for each segment is... By segment number The arrangement forms a radial gradient rate of change distribution. The difference in mean between the 5th and 6th segments. The value is the maximum value in the radial gradient change rate distribution. The radial distance between the 5th and 6th segments is 50 pixels, which is defined as the halo influence radius. The grayscale changes of pixels within the halo influence radius are dominated by the corona discharge halo, while the grayscale changes of pixels outside the halo influence radius are dominated by the background texture of the area where the spray tank wall and the powder accumulation layer are located.

[0075] The background reference image is located at the imaging position. radial distance between Pixels smaller than 50 pixels are marked as halo interference pixels, resulting in a halo interference pixel set. The number of pixels in the halo interference pixel set is approximately the number of pixels in a circular area with a radius of 50 pixels. indivual.

[0076] The interpolation neighborhood of a pixel in the halo interference pixel set is a circular area with a radius of 25 pixels centered at the pixel's coordinates. 25 pixels is half the halo's influence radius of 50 pixels. If the number of non-halo interference pixels within the interpolation neighborhood is less than two, the interpolation neighborhood radius is increased in steps of 5 pixels until the number of non-halo interference pixels within the interpolation neighborhood reaches two. The distance between a non-halo interference pixel and a halo interference pixel is denoted as... The grayscale value corresponding to the non-halo interference pixel is denoted as Weight satisfy: .

[0077] Normalized weights satisfy: for The ratio of the sum of the weights of all non-halo interference pixels within the interpolation neighborhood.

[0078] Interpolation results satisfy: .

[0079] coordinate Halo interference pixels and imaging position The radial distance between them is 45 pixels, which is less than the halo's radius of influence of 50 pixels; the interpolation neighborhood contains two non-halo interference pixels, with coordinates... The radial distance between the non-halo interference pixel and the imaging position is 63 pixels, and the coordinates are... The distance between halo interference pixels 18 pixels, grayscale value 90; coordinates The radial distance between the non-halo interference pixel and the imaging position is approximately 50.5 pixels, and the coordinates are... The distance between halo interference pixels 23 pixels, grayscale value The weight is 88. Weight Normalized weights Normalized weights Interpolation results .

[0080] Replace the grayscale values ​​of pixels in the halo interference pixel set with the interpolated results. The halo-suppressed image is obtained, and the coordinates in the halo-suppressed image are... The pixel grayscale value is 89.24; the grayscale values ​​of pixels in the halo suppression image that do not belong to the set of pixels affected by halo interference are kept at the grayscale values ​​of the corresponding pixels in the background reference image. constant.

[0081] The coordinates in the halo suppression image are The grayscale value of the pixel is denoted as The neighborhood of a pixel is defined by coordinates. A window centered at a point with sides of 15 pixels is used. 15 pixels is five times the side length of the 3-pixel neighborhood used for grayscale gradient calculation, and is smaller than the window range corresponding to a halo influence radius of 50 pixels. This avoids local grayscale calculations crossing the regions of pixels affected by halo interference and those not affected by halo interference. The grayscale maximum within the neighborhood is denoted as... The minimum gray value is denoted as Gray-scale maximum value and the minimum gray value It constitutes a local grayscale range.

[0082] Coordinates in enhanced image of powder layer pixel grayscale value Gray-scale maximum value and the minimum gray value When they are equal, the coordinates in the enhanced image of the powder layer are... pixel grayscale value Preserve the grayscale value of the corresponding pixel in the halo-suppressed image. Keep it unchanged to avoid division by zero. Coordinates The maximum gray level in the neighborhood of a pixel The minimum grayscale value is 180. The coordinates in the halo suppression image are 60. pixel grayscale value The coordinates in the enhanced image of the pollen layer are 130. pixel grayscale value .

[0083] No. Once the bead-enhanced image corresponding to a frame is determined, it is appended to the bead-enhanced image sequence according to the acquisition time sequence of the image frame sequence, forming the first bead-enhanced image in the bead-enhanced image sequence. The length of the powder layer enhanced image sequence increases with the number of consecutive image acquisition frames.

[0084] S2. Perform frame-by-frame image segmentation on the enhanced image sequence of the powder accumulation layer to obtain the powder accumulation layer region; extract the edge contour of the powder accumulation layer region facing the spraying hopper wall; select multiple discrete points along the edge contour to obtain the discrete point set of the edge contour; perform curve fitting on the discrete point set of the edge contour to obtain the contour of the powder accumulation front.

[0085] The method for obtaining the contour of the powder accumulation front by curve fitting the discrete point set of the edge contour includes: Randomly select a subset of points with the same number of points from the discrete point set of the edge contour; perform curve fitting on each subset of points to obtain the corresponding candidate fitting curves; calculate the deviation of each point in the discrete point set of the edge contour to each candidate fitting curve to obtain the deviation distribution corresponding to each candidate fitting curve.

[0086] Calculate the median of the deviation for each deviation distribution, and calculate the median of the absolute value of the difference between each deviation and the corresponding median of the deviation in each deviation distribution. Then, determine the sum of the median of the deviation and the median of the absolute deviation for each deviation distribution as the inlier threshold for the deviation distribution.

[0087] Points with deviations less than the corresponding inner point judgment threshold in each deviation distribution are identified as the corresponding inner point set. The inner point set with the largest number of points is selected for curve fitting to obtain the contour of the powder accumulation front. The gap values ​​between each point on the powder accumulation front contour and the spraying bin wall are calculated to obtain the gap distribution.

[0088] For example, a powder layer enhances the image. Medium grayscale value equals grayscale level The number of pixels is denoted as , The value range is an integer from 0 to 255; expressed in grayscale. As the dividing point, The value range is an integer from 0 to 254, and the gray level is 0 to 254. The corresponding pixels are classified into the first category, grayscale. Pixels corresponding to values ​​up to 255 are classified into the second category. The number of pixels in the first category accounts for the majority of the toner-enhanced image. The proportion of the total number of pixels is 921,600. The second category is , The average grayscale value of the pixels in the first category is The average grayscale value of the pixels in the second category is grayscale Corresponding inter-class variance Iterate through integers from 0 to 254 and calculate the corresponding inter-class variance. ,Will The gray level corresponding to the maximum value is determined as the segmentation threshold. The diffuse reflectance of the powder accumulation layer material to incident light is higher than that of the substrate on the spray bin wall, resulting in a higher gray level after image enhancement. (The image enhancement process for the powder accumulation layer is described here.) Pixels with gray values ​​from 0 to 150 represent low-grayscale areas where adjacent pixels on the spraying bin wall have concentrated gray values, while pixels with gray values ​​from 151 to 255 represent high-grayscale areas where adjacent pixels on the powder accumulation layer have concentrated gray values. (Inter-class variance...) In grayscale The maximum value is obtained when the gray level is equal to 150. Therefore, 150 gray level is determined as the segmentation threshold, and the powder layer enhances the image. Pixels with a grayscale value greater than 150 are identified as the powder accumulation layer region.

[0089] The imaging position of the spraying chamber wall in the image is determined by the relative positional calibration relationship between the auxiliary electrode and the spraying chamber wall in the image coordinate system. A vertical reference line equal to 1200 was used for calibration. The calibration process involved pre-setting calibration points with known actual spacing within the image acquisition device's shooting range to establish a conversion relationship between pixel coordinates and actual physical distance, resulting in an actual physical distance of 0.2mm for each pixel. Within the toner accumulation layer area, the coordinates... In the same pixel The pixel with the largest coordinate is determined as the edge contour point corresponding to coordinate y, and the edge contour point faces... One side of the enlarged spray booth wall; the row coordinates of the powder accumulation layer area. The range is 100 to 700, representing the row coordinates of the pollen layer area covered. Every 5 pixels within the range, a row is selected to obtain a discrete point set of the edge contour. The number of points contained in the discrete point set of the edge contour is... The set of discrete points on the edge contour. The coordinates of the points are as follows .

[0090] The number of points randomly selected from the discrete point set of the edge contour is... A collection of ideas, The value is 3, a quadratic curve It contains 3 undetermined coefficients, and 3 points uniquely determine 1 quadratic curve; the proportion of outliers caused by segmentation errors or interference from adjacent structures in the discrete point set of the edge contour is less than 10%, and the proportion of interior points is estimated. Take 0.9 as the confidence level. Take 0.99, the number of times the point subset is drawn. .

[0091] Substitution , , Calculated The number of times the subset of points is sampled, K, is set to 50, covering the minimum number calculated, and for cases where the actual proportion of inliers is lower than the estimated value. There is room for maneuver in the situation.

[0092] Curve fitting is performed on each subset of points to obtain candidate fitting curves. , u=1,2,…,50. The discrete point set of the edge contour... Points to candidate fitted curve deviation .

[0093] Candidate Fitting Curve The corresponding deviation distribution is from to The median of the deviation distribution is denoted as . Candidate fitting curve corresponding median absolute deviation satisfy: .

[0094] Candidate Fitting Curve Corresponding interior point determination threshold satisfy: .deviation Less than the interior point determination threshold The points were determined as candidate fitted curves. The corresponding set of interior points, the number of points contained in the set of interior points is denoted as . The coefficients of candidate fitted curve 1 It is 0.00013. It is -0.058. The median deviation is 855. 3.8 pixels, median absolute deviation The threshold for determining the inner point is 1.6 pixels. The number of points contained in the inner point set is 3.8 + 1.6 = 5.4 pixels. The number is 112. This refers to the number of points contained in the set of interior points corresponding to candidate fitted curve 27. The set of 116 inliers is greater than the number of inliers corresponding to the other 49 candidate fitting curves. Therefore, the set of inliers corresponding to candidate fitting curve 27 is selected for curve fitting to obtain the contour of the pollen accumulation front. The coefficient of the pollen accumulation front contour is... It is 0.0001. It is -0.05. It is 850.

[0095] The gap value of the i-th point corresponding to the discrete point set of the edge contour on the front profile of the powder accumulation layer. .

[0096] On the leading edge of the powder accumulation layer The point equal to 400 corresponds to Coordinates are gap value for mm; The point equal to 700 corresponds to Coordinates are gap value for mm. Gap values ​​corresponding to 121 points in the discrete point set of the edge contour. to It forms a gap distribution.

[0097] Based on the gap distribution and the high voltage output voltage, the local electric field intensity distribution between the front edge of the powder accumulation layer and the wall of the spraying bin is calculated.

[0098] The method for calculating the local electric field intensity distribution between the powder accumulation front and the spraying bin wall based on the gap distribution and the high-voltage output voltage includes: Calculate the mean value of the gap at each point in the gap distribution to obtain the average gap value. ; Calculate the first The difference between the gap value at each point and the gap value between two adjacent points yields the gap gradient value. According to the first Point gap value , gap gradient value With average gap value Calculate local morphological coefficients .

[0099] Based on local morphological coefficients With the preset field strength concentration factor Calculate the first Local electric field intensity at each point Based on the local electric field intensity at each point, the local electric field intensity distribution between the front edge of the powder accumulation layer and the wall of the spraying bin is formed.

[0100] For example, the first [unclear] on the contour of the leading edge of the powder accumulation layer The gap value di corresponding to each point, where i is an integer from 1 to 121, corresponds one-to-one with the 121 gap values ​​in the preceding gap distribution; the arithmetic mean of the 121 gap values ​​is the average gap value. .

[0101] The gap values ​​corresponding to 121 points on the front profile of the powder accumulation layer are given by the equation (Unit: mm) The ordinate of the corresponding point on the contour of the front edge of the pollen accumulation layer (range 100 to 700) is used to determine the gap value. The sum of the 121 gap values ​​is 8492.99, and the average gap value is... The calculated value is 70.19 mm.

[0102] No. The gap gradient value is formed by the difference between the gap value of each point and the gap value of two adjacent points. ,for Points that are neither equal to 1 nor equal to 121 satisfy: .

[0103] equation for A quadratic function with an interval of 5 between adjacent points' ordinates. The difference between the sum of the gap values ​​of two adjacent points and twice the gap value of the current point is always 0. mm, based on this gap gradient value exist The value is always 0.0005 mm at points that are neither equal to 1 nor equal to 121. For For a point equal to 1, only the second point exists among its two adjacent points. A third point is used to construct a one-sided second-order difference. To maintain consistency with the normalization method of the gradient values ​​between internal points, the gradient values ​​between the points satisfy... ;for For a point equal to 121, only the 120th point exists among its two adjacent points. Using the 119th point as an auxiliary point to construct a one-sided second-order difference, the gap gradient value satisfies... The first point gap value The gap value at the second point is 70.8mm. The gap value at the third point is 70.8295mm. The gap gradient value is 70.858mm. The gap value at the 121st point is 0.0005mm. The gap value at the 120th point is 67.2mm. The gap value is 67.2895mm, the 119th point. The gap gradient value is 67.378 mm. The corrected boundary point gap gradient value is 0.0005mm. |、| All are 0.0005mm, which is equal to the gradient value of the internal point gap.

[0104] Based on local morphological coefficients The local morphological coefficients corresponding to the first point are obtained. Approximately equal to 1.0087; the local morphological coefficient corresponding to the 121st point. Approximately 0.9574. At this time | |and| Both are 0.001mm, they are equal, and no longer... Less than The main reasons; Less than Both of them deviate slightly from 1, mainly due to , Self-relative average gap value The deviation decision, It is 70.8mm greater than , It is 67.2mm less than The corresponding powder accumulation front shows an overall gradual trend along the length of the auxiliary electrode, rather than a local bulge anomaly at point 121.

[0105] It should be noted that local morphological coefficients In the calculation formula, the gap gradient value The calculation uses absolute values. Regardless of whether the point is closer to the bin wall (local bulge) or farther away from the bin wall (local depression) than the two adjacent points, the local electric field intensity is corrected and amplified in the same direction. This is to avoid underestimating the conduction current component at the depression area due to uneven particle accumulation and complex local conductive channels. It ensures that the corrected corona current component is not too high due to the underestimation of the conduction current component, thereby avoiding the high voltage output voltage being mistakenly increased.

[0106] Preset field strength concentration factor The selection was based on the creation of multiple sets of gap distributions with corresponding local morphological coefficients. Different reference powder layer front simulation components were used. Under the same high-voltage output voltage as the reference corona current, each reference component was placed between the auxiliary electrode and the spray chamber wall, and the corresponding stable corona current value was measured. The difference between the stable corona current value of each reference component and the reference corona current was determined as the corona current increment of that reference component. The corona current increment was then fitted with the corresponding local morphology coefficient. The statistical relationship between the proportions deviating from 1 is used to determine the preset field strength concentration factor. In this embodiment Take 1.5. (The last part is incomplete and likely refers to a number or digit.) Local electric field intensity at each point .

[0107] The local electric field intensity corresponding to the first point The electric field strength is approximately 0.6274 kV / mm, which is about 1.3% lower than the electric field strength calculated based on a uniform distribution of gap values ​​(45 / 70.8≈0.6356 kV / mm). The local electric field strength at point 121 is... The value is approximately 0.7148 kV / mm, which is about 6.8% higher than the electric field strength calculated based on a uniform distribution of the gap value (45 / 67.2≈0.6696 kV / mm). The magnitude of the increase / decrease corresponds to the local shape coefficient. , After negative The corrected result after exponentiation.

[0108] Local electric field intensities corresponding to 121 points on the contour of the front edge of the powder accumulation layer to This constitutes the local electric field intensity distribution between the front edge of the powder accumulation layer and the wall of the spraying bin.

[0109] S3. Correct the preset equivalent linear conductivity reference parameters of the powder accumulation layer according to the temperature and humidity data to obtain the corrected equivalent linear conductivity parameters; calculate the current density distribution on the conduction path from the powder accumulation front to the spraying bin wall according to the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, and integrate along the arc length direction of the powder accumulation front profile to obtain the conduction current component.

[0110] The method for calculating the current density distribution along the conduction path from the powder accumulation front to the spraying hopper wall based on the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, and then integrating along the arc length direction of the powder accumulation front profile to obtain the conduction current components includes: The local electric field intensity distribution is related to the contour of the front edge of the powder accumulation layer. Multiplying the local electric field intensity value at the i-th point by the corrected equivalent linear conductance parameter yields the i-th point. The current density value per unit arc length on the conduction path at each point ; Calculate the first [missing information] on the profile of the front edge of the powder accumulation layer The arc length between each point and its two adjacent points is used to obtain the arc length interval. Based on current density value Interval with arc length The conduction current components were calculated. .

[0111] For example, the powder accumulation layer is formed by the continuous adhesion and accumulation of paint particles. In the gap area between the leading edge of the powder accumulation layer and the wall of the spray booth, there are also paint particles in a deposited or suspended state and conductive channels formed by their adsorbed moisture. The conductivity characteristics are similar to those of the offline powder accumulation layer material sample. The preset equivalent linear conductivity reference parameters for the powder accumulation layer are... , for reference temperature 25℃, reference relative humidity Under the condition of 50%, an offline powder accumulation layer material sample is held in a parallel electrode test fixture with an electrode spacing that matches the gap between the front edge of the powder accumulation layer and the wall of the spraying chamber. The value is set after measuring the equivalent conductivity value per unit arc length of the fixture using a conductivity meter. Values S, the equivalent linear conductivity already implies the equivalent thickness factor of the toner layer along the image depth direction, so its dimension is S.

[0112] Temperature correction factor Humidity correction factor In this embodiment, the equivalent linear conductivity of the dust accumulation layer is measured under multiple sets of different temperatures and relative humidity conditions, and the measured data are fitted to pre-determine the conductivity. Take 0.03 / ℃, Use 0.02 / %RH. Correct the equivalent linear conductance parameter. Equivalent linear conductivity reference parameters of the powder accumulation layer Temperature correction factor Humidity correction factor satisfy: .

[0113] The powder accumulation layer is formed by the deposition of paint particles. The moisture content adsorbed on the particle surface increases with increasing temperature and relative humidity. The conductive channels between particles increase with increasing adsorbed moisture content. The increase in the conductivity of the powder accumulation layer with increasing temperature and relative humidity is directly proportional to the increase in temperature and relative humidity themselves. The corrected equivalent linear conductivity parameter is then determined. It exhibits an exponential relationship with the temperature correction term and the relative humidity correction term.

[0114] The temperature and humidity data inside the spray booth were: temperature 28℃, relative humidity 65%. The relative humidity is 28. The value is 65, and the corrected equivalent linear conductance parameter is calculated. Approximately S.

[0115] The 121 points on the contour of the powder accumulation front are numbered sequentially during the calculation of the local electric field intensity distribution. Numbering, the current density distribution is calculated using serial numbers. Number, Serial Number With serial number One-to-one correspondence, , and the first on the contour of the front edge of the powder accumulation layer The local electric field intensity value corresponding to each point is denoted as . . No. The current density value per unit arc length on the conduction path at each point .

[0116] The local electric field intensity corresponding to the first point The current density is 0.6274 kV / mm, which translates to 627.4 V / mm. for A / mm, converted to 0.1853μA / mm; the local electric field intensity corresponding to the 121st point. The current density is 0.7148 kV / mm, which translates to 714.8 V / mm. for A / mm, which translates to 0.2112μA / mm.

[0117] The first contour of the front edge of the powder accumulation layer The point and the first The arc length between the points is denoted as . , No. The coordinates of the points are , No. The coordinates of the points are arc length .

[0118] The quadratic coefficient of the front profile of the powder accumulation layer The value is 0.0001, much less than 1, indicating that the curvature of the contour along the front edge of the pollen layer between adjacent points is extremely small, and the arc length is very short. Adopting the first The point and the first The straight-line distance between the points is approximately equal.

[0119] No. The arc length interval between each point and its two adjacent points ,for Points that are neither equal to 1 nor equal to 121 satisfy: .

[0120] for For points equal to 1, there exists only one second point among two adjacent points, with an arc length interval of 1. The arc length between the first point and the second point. ;for For a point equal to 121, only the 120th point exists among its two adjacent points, with an arc length interval of [missing information]. The arc length between the 120th and 121st points. .

[0121] The coordinates of the first point are The coordinates of the second point are The arc length was calculated. Approximately mm, arc length interval It is 1.0004mm; the coordinates of the 120th point are The coordinates of the 121st point are The arc length was calculated. Approximately mm, arc length interval The arc length intervals corresponding to 121 points on the contour of the leading edge of the powder accumulation layer are 1.0040 mm. to The value ranges from 1.0004 mm to 1.0040 mm.

[0122] Current density value Interval with arc length The product is μA, current density value Interval with arc length The product is μA. The conduction current component was obtained by calculating point-by-point at 121 points on the contour of the front edge of the powder accumulation layer. The value is 22.97 μA.

[0123] S4. Calculate the difference between the feedback current and the conduction current components to obtain the corrected corona current component; when the corrected corona current component exceeds the preset corona current range, adjust the high voltage output voltage.

[0124] For example, feedback current The conduction current component is 385 μA. The corrected corona current component is 22.97 μA. μA.

[0125] Upper limit of preset corona current range and lower limit Based on the reference corona current Corona current fluctuation coefficient Confirmed, satisfied: .

[0126] Reference corona current The stable value of the corona current, measured under a 45kV high-voltage output voltage, is taken as 345μA, in the initial state before the auxiliary electrode surface has a powder layer attached; the corona current fluctuation coefficient is... The value is determined based on the statistical analysis of the normal fluctuation amplitude of the corona current caused by the airflow disturbance in the spray booth and the output ripple of the high-voltage power supply circuit, and is taken as 0.03. for μA, for μA.

[0127] Corrected corona current components It is 362.03 μA, which is greater than The current value is 355.35μA, exceeding the preset corona current range, so the high-voltage output voltage is adjusted. The corrected corona current component... Exceeding deviation satisfy: μA. The adjustment value of the high-voltage output voltage. satisfy: Voltage regulation coefficient The high-voltage output voltage was adjusted in a stepwise manner before the dust accumulation layer was formed, and the corresponding corona current change was recorded synchronously. The ratio between the high-voltage output voltage change and the corona current change was fitted and determined to be 0.05 kV / μA. for kV, the high-voltage output voltage after regulation satisfy: kV. Corrected corona current component. Less than When, deviation for The adjusted high voltage output voltage Corrected corona current component Between and During this period, the high-voltage output voltage remains constant at 45kV without any adjustment.

[0128] The output voltage range of the high-voltage power supply circuit is 0 to 80kV, consistent with the range of the voltage sensor; the adjusted high-voltage output voltage When the output voltage exceeds the range of the high-voltage power supply circuit, 0kV or 80kV is used as the adjusted high-voltage output voltage; in this embodiment... The voltage is 44.67kV, which is within the output voltage range of the high-voltage power supply circuit. The adjusted high-voltage output voltage... Used for calculating the feedback current, conduction current component, and corrected corona current component in the next cycle, until the corrected corona current component falls back to... and between.

[0129] Example 2: Based on the same inventive concept, such as Figure 2 As shown, this embodiment also provides an electric field parameter control system for a spray coating chamber, the system comprising: The data acquisition module is used to acquire the feedback current of the high-voltage power supply circuit of the auxiliary electrode, obtain the high-voltage output voltage of the high-voltage power supply circuit; acquire the temperature and humidity data in the spraying chamber; and continuously acquire and enhance images of the area between the auxiliary electrode and the wall of the spraying chamber to obtain an enhanced image sequence of the powder accumulation layer.

[0130] The electric field calculation module is used to perform frame-by-frame image segmentation on the enhanced image sequence of the powder accumulation layer to obtain the powder accumulation layer region; extract the edge contour of the powder accumulation layer region facing the spraying hopper wall; select multiple discrete points along the edge contour to obtain the discrete point set of the edge contour; perform curve fitting on the discrete point set of the edge contour to obtain the powder accumulation front contour; calculate the gap value between each point on the powder accumulation front contour and the spraying hopper wall to obtain the gap distribution; and calculate the local electric field intensity distribution between the powder accumulation front and the spraying hopper wall based on the gap distribution and the high voltage output voltage.

[0131] The conduction current calculation module is used to correct the preset equivalent linear conductivity reference parameters of the powder accumulation layer based on temperature and humidity data to obtain the corrected equivalent linear conductivity parameters; based on the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, the current density distribution on the conduction path from the powder accumulation front to the spraying bin wall is calculated, and the current density is integrated along the arc length direction of the powder accumulation front profile to obtain the conduction current component.

[0132] The voltage regulation module is used to calculate the difference between the feedback current and the conduction current components to obtain the corrected corona current component; when the corrected corona current component exceeds the preset corona current range, the high voltage output voltage is regulated.

[0133] It should be noted that the specific methods by which each module performs operations in the system described in the above embodiments have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0134] Finally, it should be noted that although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling electric field parameters in a spray coating chamber, characterized in that, The method includes: The feedback current of the high-voltage power supply circuit of the auxiliary electrode is collected, and the high-voltage output voltage of the high-voltage power supply circuit is obtained; the temperature and humidity data in the spraying chamber are acquired; continuous image acquisition and image enhancement processing are performed on the area between the auxiliary electrode and the wall of the spraying chamber to obtain the powder accumulation layer enhanced image sequence. The enhanced image sequence of the powder accumulation layer is segmented frame by frame to obtain the powder accumulation layer region; the edge contour facing the spraying hopper wall in the powder accumulation layer region is extracted; multiple discrete points are selected along the edge contour to obtain the discrete point set of the edge contour; curve fitting is performed on the discrete point set of the edge contour to obtain the powder accumulation front contour; the gap value between each point on the powder accumulation front contour and the spraying hopper wall is calculated to obtain the gap distribution; based on the gap distribution and the high voltage output voltage, the local electric field intensity distribution between the powder accumulation front and the spraying hopper wall is calculated. The preset equivalent linear conductivity reference parameters of the powder accumulation layer are corrected based on temperature and humidity data to obtain the corrected equivalent linear conductivity parameters. Based on the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, the current density distribution on the conduction path from the powder accumulation front to the spraying hopper wall is calculated, and the current density is integrated along the arc length direction of the powder accumulation front profile to obtain the conduction current component. The corrected corona current component is obtained by calculating the difference between the feedback current and the conduction current component; when the corrected corona current component exceeds the preset corona current range, the high voltage output voltage is adjusted.

2. The method for controlling electric field parameters in a spray coating chamber according to claim 1, characterized in that, The method for continuously acquiring and enhancing images of the area between the auxiliary electrode and the spraying chamber wall to obtain an enhanced image sequence of the powder accumulation layer includes: Based on the distribution of grayscale differences between adjacent image frames in the image frame sequence obtained from continuous image acquisition, identify the set of dynamic interference pixels; The grayscale values ​​of pixels in the dynamic interference pixel set are replaced with the grayscale values ​​of corresponding pixels in the adjacent previous image frame to obtain the background reference image. Based on the gray-level gradient distribution within the neighborhood of pixels in the background reference image, a set of pixels with halo interference is identified; inverse distance weighted interpolation is performed on the set of pixels with halo interference to obtain a halo-suppressed image. Calculate the maximum and minimum gray values ​​within the neighborhood of each pixel in the halo-suppressed image to obtain the local gray range; perform linear stretching based on the local gray range to obtain the powder layer enhancement image, thus forming a powder layer enhancement image sequence.

3. The method for controlling electric field parameters in a spray coating chamber according to claim 2, characterized in that, The method for identifying a set of dynamically interfering pixels based on the distribution of grayscale differences between adjacent image frames in an image frame sequence obtained from continuous image acquisition includes: Calculate the grayscale difference between the corresponding pixels of the current image frame and the adjacent previous image frame to obtain an inter-frame difference map; statistically analyze the distribution of grayscale differences in the inter-frame difference map to obtain a difference grayscale histogram; calculate the inter-class variance of each grayscale level in the difference grayscale histogram, and determine the grayscale level corresponding to the maximum value as the dynamic judgment threshold. Pixels whose grayscale difference in the inter-frame difference image exceeds the dynamic judgment threshold are marked as dynamic interference pixels, thus obtaining a set of dynamic interference pixels.

4. The method for controlling electric field parameters in a spray coating chamber according to claim 2, characterized in that, The method for replacing the gray values ​​of pixels in the dynamic interference pixel set with the gray values ​​of corresponding pixels in the adjacent previous image frame to obtain a background reference image includes: Set the background grayscale value of each pixel to the grayscale value of the corresponding pixel in the first frame image, and set the background drift rate of each pixel to zero; For pixels in the current image frame that do not belong to the set of dynamic interference pixels, calculate the difference between the gray value of the pixel in the current image frame and the corresponding background gray value; based on the difference between the gray value of the pixel in the current image frame and the corresponding background gray value, update the corresponding background drift rate using a cumulative averaging method to obtain the updated background drift rate; update the corresponding background gray value based on the updated background drift rate to obtain the updated background gray value. For a pixel in the current image frame that belongs to the set of dynamic interference pixels, calculate the sum of the corresponding background gray value and the corresponding background drift rate as the replacement value; replace the gray value of the pixel in the current image frame with the replacement value to obtain the background reference image.

5. The method for controlling electric field parameters in a spray coating chamber according to claim 4, characterized in that, The method for updating the background drift rate by using a cumulative averaging method based on the difference between the grayscale value of a pixel in the current image frame and the corresponding background grayscale value, to obtain the updated background drift rate, includes: Calculate the ratio of the number of pixels in the set of dynamic interference pixels in the current image frame to the total number of pixels in the current image frame to obtain the proportion of dynamic interference points; determine the proportion of dynamic interference points as the update weight; calculate the difference between the gray value of a pixel in the current image frame and the corresponding gray value of the background, and the deviation of the background drift rate to obtain the rate deviation; sum the product of the update weight and the rate deviation with the background drift rate to determine the updated background drift rate.

6. The method for controlling electric field parameters in a spray coating chamber according to claim 2, characterized in that, The method for identifying a set of halo-interference pixels based on the gray-level gradient distribution within the neighborhood of pixels in a background reference image includes: Based on the relative positional calibration relationship between the auxiliary electrode and the spraying chamber wall, the imaging position of the auxiliary electrode is determined in the background reference image; the gray-level gradient values ​​in the neighborhood of the pixel in the background reference image are calculated to obtain the gradient distribution map; based on the radial distance between the pixel and the imaging position, the mean value of the gray-level gradient values ​​in the gradient distribution map is calculated piecewise to obtain the radial gradient distribution curve. Calculate the mean difference between adjacent segments on the radial gradient distribution curve to obtain the radial gradient rate of change distribution; determine the radial distance corresponding to the segment with the largest difference in the radial gradient rate of change distribution as the halo influence radius; mark the pixels in the background reference image whose radial distance from the imaging position is less than the halo influence radius as halo interference pixels to obtain the halo interference pixel set.

7. The method for controlling electric field parameters in a spray coating chamber according to claim 1, characterized in that, The method for obtaining the contour of the powder accumulation front by curve fitting the discrete point set of the edge contour includes: Randomly select a subset of points with the same number of points from the discrete point set of the edge contour; perform curve fitting on each subset of points to obtain the corresponding candidate fitting curves; calculate the deviation of each point in the discrete point set of the edge contour to each candidate fitting curve to obtain the deviation distribution corresponding to each candidate fitting curve. Calculate the median of the deviation for each deviation distribution, and calculate the median of the absolute value of the difference between each deviation and the corresponding median of the deviation in each deviation distribution. Then, determine the sum of the median of the deviation and the median of the absolute deviation for each deviation distribution as the inlier threshold for the deviation distribution. Points in each deviation distribution whose deviation is less than the corresponding inlier determination threshold are identified as the corresponding inlier set. The set of interior points with the largest number of points is selected for curve fitting to obtain the profile of the front edge of the powder accumulation layer.

8. The method for controlling electric field parameters in a spray coating chamber according to claim 1, characterized in that, The method for calculating the local electric field intensity distribution between the powder accumulation front and the spraying bin wall based on the gap distribution and the high-voltage output voltage includes: Calculate the mean value of the gap at each point in the gap distribution to obtain the average gap value. ; Calculate the first The difference between the gap value at each point and the gap value between two adjacent points yields the gap gradient value. According to the first Point gap value , gap gradient value With average gap value Calculate local morphological coefficients ; Based on local morphological coefficients With the preset field strength concentration factor Calculate the first Local electric field intensity at each point Based on the local electric field intensity at each point, the local electric field intensity distribution between the front edge of the powder accumulation layer and the wall of the spraying bin is formed.

9. The method for controlling electric field parameters in a spray coating chamber according to claim 1, characterized in that, The method for calculating the current density distribution along the conduction path from the powder accumulation front to the spraying hopper wall based on the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, and then integrating along the arc length direction of the powder accumulation front profile to obtain the conduction current components includes: The local electric field intensity distribution is related to the contour of the front edge of the powder accumulation layer. Multiplying the local electric field intensity value at the i-th point by the corrected equivalent linear conductance parameter yields the i-th point. The current density value per unit arc length on the conduction path at each point ; Calculate the first [missing information] on the profile of the front edge of the powder accumulation layer The arc length between each point and its two adjacent points is used to obtain the arc length interval. Based on current density value Interval with arc length The conduction current components were calculated. .

10. An electric field parameter control system for a spray coating chamber, used to perform the method according to any one of claims 1 to 9, characterized in that, The system includes: The data acquisition module is used to acquire the feedback current of the high-voltage power supply circuit of the auxiliary electrode, obtain the high-voltage output voltage of the high-voltage power supply circuit; acquire the temperature and humidity data in the spraying chamber; and continuously acquire images of the area between the auxiliary electrode and the wall of the spraying chamber and perform image enhancement processing to obtain an enhanced image sequence of the powder accumulation layer. The electric field calculation module is used to perform frame-by-frame image segmentation on the enhanced image sequence of the powder accumulation layer to obtain the powder accumulation layer region; extract the edge contour of the powder accumulation layer region facing the spraying hopper wall; select multiple discrete points along the edge contour to obtain the edge contour discrete point set; perform curve fitting on the edge contour discrete point set to obtain the powder accumulation layer front contour; calculate the gap value between each point on the powder accumulation layer front contour and the spraying hopper wall to obtain the gap distribution; and calculate the local electric field intensity distribution between the powder accumulation layer front and the spraying hopper wall based on the gap distribution and the high voltage output voltage. The conduction current calculation module is used to correct the preset equivalent linear conductivity reference parameters of the powder accumulation layer based on temperature and humidity data to obtain the corrected equivalent linear conductivity parameters; based on the local electric field intensity distribution and the corrected equivalent linear conductivity parameters, the current density distribution on the conduction path from the powder accumulation front to the spraying bin wall is calculated, and the current density is integrated along the arc length direction of the powder accumulation front profile to obtain the conduction current components. The voltage regulation module is used to calculate the difference between the feedback current and the conduction current components to obtain the corrected corona current component; when the corrected corona current component exceeds the preset corona current range, the high voltage output voltage is regulated.

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