A control method and device of a license plate spray plotter

Abstract

The application relates to a control method and device of a license plate spraying machine, and relates to the technical field of spraying equipment.The method comprises the following steps: in response to a preset trigger signal, arranging and feeding a license plate in a preset arrangement station to a preset conveying mechanism by a preset arrangement and feeding method; when the license plate is conveyed on the conveying mechanism, positively and reversely adjusting the license plate by a preset positive and reverse adjusting method, knocking the license plate by a preset knocking force, and collecting knocking sound information; comparing the knocking sound information with a preset reference spectrum to determine a surface type, wherein the surface type comprises a film type and a non-film type; based on the film type, removing the film on the license plate surface by a preset film removing method, and collecting a top view image of the license plate; based on the non-film type, collecting the top view image of the license plate; obtaining a spraying area from the top view image of the license plate according to a preset number feature, and spraying the spraying area. The application has the effects of ensuring accurate spraying position and avoiding waste of spraying ink.

Description

Technical Field

[0001] This invention relates to the field of spraying equipment technology, and in particular to a control method and device for a license plate inkjet printer. Background Technology

[0002] Motor vehicle license plates are plates that are hung at the front and rear of a vehicle. They serve as the vehicle's identification. During the production process, ink is used to color the numbers on the surface of the vehicle. The purpose of this is to enhance the recognizability of the numbers through color contrast, so as to meet the needs of daily traffic verification and supervision.

[0003] Currently, the industry mainly relies on two types of mainstream equipment for coloring license plate numbers. One is the heat transfer machine, which transfers pre-printed patterns by heating. It has a high ink utilization rate and is suitable for scenarios with high precision requirements. The other is the roller coating machine, which coats ink by rolling rollers. It is relatively easy to operate, suitable for mass production, and can cover most conventional license plate processing needs. The two types of equipment each have their own suitable scenarios and work together to support the operation of the license plate coloring process.

[0004] However, in actual use, roller coating machines require the roller to pick up ink and then roll it onto the license plate surface, which can easily lead to ink waste. For example, ink may drip from the edge of the roller that exceeds the size of the license plate, resulting in some ink becoming waste without being used for coloring. Summary of the Invention

[0005] To improve the accuracy of spraying position and reduce ink waste, this invention provides a control method for a license plate inkjet printer.

[0006] Firstly, the present invention provides a control method for a license plate inkjet printer, which adopts the following technical solution: A control method for a license plate inkjet printer includes: Step 1: In response to a preset trigger signal, the license plates in the preset sorting station are sorted and fed to the preset conveyor mechanism using a preset sorting and feeding method. Step 2: When the license plate is being transported on the conveyor, the license plate is adjusted to the front and back using a preset forward and reverse adjustment method, and the license plate is struck with a preset striking force, and the striking sound information is collected. Step 3: Compare the tapping sound information with the preset reference spectrum to determine the surface type. The surface type includes coated type and uncoated type. Step 40: Based on the type of film, remove the film from the license plate surface using a preset film removal method, and capture a top-view image of the license plate; Step 41: Based on the non-film type, acquire a top-view image of the license plate; Step 5: Based on the preset number characteristics, obtain the spraying area from the top view image of the license plate, and spray the area.

[0007] By adopting the above technical solution, the material is automatically sorted and fed through a preset sorting and feeding method. The knocking sound information is compared with the reference spectrum, and the data difference is used to accurately distinguish between film-coated and non-film-coated types, providing a basis for subsequent processing. The number feature data in the license plate top view image accurately locates the spraying area, ensuring accurate spraying position and avoiding waste of spraying ink.

[0008] Optional material handling and loading methods include: Step 10: Obtain the license plate stack height in the sorting station, and filter out the maximum stack height from the license plate stack heights; Step 11: Set the leveling height according to the preset license plate height; Step 120: When the maximum stacking height is greater than the flattening height, control the preset pushing structure to push the license plate away at the flattening height, and repeat step 10. Step 121: When the maximum stacking height is not greater than the flattening height, collect an image of the license plate arrangement above the arrangement station; Step 13: Identify the complete license plate outline features from the license plate arrangement image, and determine the license plate placement status based on the complete license plate outline features and the preset reference direction; Step 14: Determine the license plate clamping point and adjust the angle according to the license plate placement; Step 15: Clamp the license plate according to the clamping point, and rotate the license plate according to the adjustment angle to adjust the license plate to the standard placement position. After the adjustment is completed, transfer the license plate to the waiting area.

[0009] By adopting the above technical solution, the vertical height data is used to determine the stacking status of license plates. When the stacking height is greater than twice the height of the license plate, the plate is pushed and adjusted to avoid difficulties in sorting and recognition. The license plate outline data in the sorting image determines the clamping point and adjustment angle, so that the license plates are neatly stacked, providing standardized workpieces for subsequent processes and ensuring smooth flow.

[0010] Optional, positive and negative adjustment methods include: Step 20: Clean the top and bottom surfaces of the license plate with air according to the preset cleaning path, and obtain continuous air reaction force information during the cleaning of the top surface of the license plate; Step 21: Generate a reaction force information curve based on the continuous blowing reaction force information, and analyze the average value of the curve; Step 220: When the average value of the curve is greater than the preset reference force value, control the conveying mechanism to continue conveying the license plate and enter the pre-film removal preparation state; Step 221: When the average value of the curve is less than the reference force value, control the license plate to flip.

[0011] By adopting the above technical solution, a reaction force information curve is generated based on the continuous air blowing reaction force information, and the magnitude of the curve average value and the reference force value are analyzed to determine the orientation of the license plate. If there is an error, the plate is flipped and adjusted to avoid incorrect spraying orientation.

[0012] Optional membrane removal methods include: Step 400: Acquire an image of the bottom of the license plate below the license plate, and identify whether there are preset membrane edge features from the bottom image of the license plate; Step 4010: When there are no film edge features, use a preset heating method to heat and remove the film from the top surface of the license plate; Step 4011: When film edge features exist, blow air from the bottom of the license plate at a preset preheating temperature, collect the license plate film removal image above the license plate, and identify whether the preset bubble features exist from the license plate film removal image. Step 40120: When there are no bubble features, use the preset scraping method to scrape and remove the film from the edge of the license plate; Step 40121: When air bubble features are present, use the preset water injection method to inject water to remove the film from the air bubble features on the top surface of the license plate.

[0013] By adopting the above technical solution, the use of heating method is determined based on the edge feature data of the film in the bottom image of the license plate; the bubble feature data in the film removal image distinguishes between scraping method and water injection method. Different methods are adapted to different protective film states to ensure thorough film removal without damaging the license plate.

[0014] Optionally, the heating method includes: Step 4020: Heat the top surface of the license plate with air at a preset heating temperature and capture an image of the protective film shrinking above the license plate; Step 4021: Obtain the shrinkage profile from the protective film shrinkage image based on the preset shrinkage features; Step 4022: Identify the apex position of the shrinkage profile and use one of the apex positions of the profile as the film removal clamping point according to the preset reference point. Step 4023: Connect the apex positions of the diagonal contours to obtain the film removal path; Step 4024: The protective film is clamped based on the film removal clamping point and the film removal path is controlled to move the protective film away from the license plate surface, thereby removing the film.

[0015] By adopting the above technical solution, the protective film is heated to a preset heating temperature to cause it to shrink. The shrinkage location is located from the shrinkage feature data in the protective film shrinkage image, and then the film removal clamping point is determined. The film shrinkage characteristics are used to remove the film efficiently, thereby improving the peeling success rate.

[0016] Optional, scraping methods include: Step 4030: Obtain the edge contour of the license plate based on the removed image of the license plate; Step 4031: Determine the movement path and blowing direction based on the edge contour of the license plate; Step 4032: Scratch the license plate based on the movement path, and move the air synchronously based on the movement path and the air blowing direction to form a preset curled edge feature; Step 4033: Identify the raised edge features from the license plate decoction image, determine the location of the raised edge features, and define it as the raised edge position; Step 4034: Determine the film removal path based on the location of the curled edge and the license plate film removal image; Step 4035: Control the preset adhesive roller to stick the protective film at the curled edge position, roll it according to the film removal path to adhere it to the license plate surface, and blow air synchronously with a preset blowing force to remove the protective film.

[0017] By adopting the above technical solution, the protective film covering the license plate surface is scratched by scraping the edge of the license plate, thus forming a raised edge. The protective film is then clamped and removed from the raised edge, improving the success rate of film removal.

[0018] Optionally, the water injection method includes: Step 4040: Analyze the bubble features from the license plate delamination image to determine the bubble location; Step 4041: Measure the distance based on the preset center position and bubble position, filter out the bubble position closest to the center position and define it as the insertion position; Step 4042: Based on the insertion position, control the preset injection device to inject water into the bubble feature to separate the protective film from the license plate surface, control the expansion part preset at the end of the injection device to expand in the bubble feature, and simultaneously take away the protective film when the injection device is retracted, and blow air to dry the license plate surface.

[0019] By adopting the above technical solution, the bubble position is located from the bubble feature data in the license plate removal image, and the bubble position closest to the center position is selected to determine the insertion position. Water is injected based on this, and the water penetration causes the protective film to separate from the license plate. The protective film is then removed by the expansion part on the injection device, which specifically treats the protective film with bubbles, improves the film removal efficiency and avoids damage to the license plate.

[0020] Secondly, this application provides a license plate inkjet printer device, which adopts the following technical solution: A license plate inkjet printer device, controlled by any of the above-mentioned license plate inkjet printer control methods, includes an inkjet printing mechanism for spraying ink to color the license plate, and further includes: A conveying mechanism is located below the inkjet printing mechanism and is used to transport license plates sequentially. The feeding mechanism is located at the feeding end of the conveying mechanism and is used to push the license plate for feeding. The feeding mechanism includes: A loading rack is used to hold license plates while waiting for loading. A push plate is slidably disposed along the loading rack and is used to move the license plate onto the conveying mechanism; A push cylinder is used to drive the push plate to move toward the conveying mechanism. Its output end is fixedly connected to one end of the push plate.

[0021] By adopting the above technical solution, the loading rack can centrally store license plates to be processed. Under the drive of the push cylinder, the push plate can stably move the license plate from the loading rack to the conveying mechanism, realizing automated loading. At the same time, the conveying mechanism is located below the inkjet printing mechanism, which can accurately and continuously transport the loaded license plates to the inkjet printing station, providing a stable guarantee for the efficient connection of the subsequent inkjet printing process.

[0022] Optionally, the feeding mechanism further includes: A baffle is fixedly installed on the feeding rack and has a gap between it and the feeding rack on the side facing the conveying mechanism. The baffle is used to limit the number of license plates that can be fed at one time. The limiting block is fixedly installed on the feeding rack and slidably connected to the push plate, and is used to limit the sliding direction of the push plate.

[0023] By adopting the above technical solution, the gap between the baffle and the feeding rack allows only a single license plate to pass through, which structurally eliminates the situation of multiple license plates being stacked for feeding, ensuring a smooth feeding process. The limiting block slides in close contact with the push plate, which can strictly limit the sliding direction of the push plate, prevent the push plate from deviating during the pushing process, and ensure that the license plate is accurately pushed to the designated position of the conveying mechanism, thereby improving the reliability of the overall feeding process.

[0024] Optionally, a tilting mechanism is also provided below the conveying mechanism. The flipping mechanism includes: A flipping frame, located below the conveying mechanism, is used to rotate to flip the license plate. A support frame is rotatably connected to the tilting frame and is used for the tilting frame to be rotatably mounted. The motor is fixedly mounted on the support frame and its output end is fixedly connected to one side of the tilting frame, and is used to drive the tilting frame to rotate. A lifting cylinder, located below the support frame and with its output end fixedly connected to the support frame, is used to drive the support frame to move up and down to selectively flip the license plate; The mounting bracket is fixedly connected to the lifting cylinder and slidably connected to the support frame, and is used to install the lifting cylinder and limit the lifting path of the support frame.

[0025] By adopting the above technical solution, the motor can drive the flipping frame to rotate stably around the support frame, realizing the 180° flipping of the license plate, effectively correcting the problem of incorrect license plate placement direction, avoiding the increase in scrap rate caused by incorrect inkjet orientation, and the lifting cylinder can drive the support frame to rise and fall, selectively lifting the license plate for flipping according to the position of the license plate on the conveying mechanism, without interfering with the normal transportation of the conveying mechanism.

[0026] In summary, the present invention has at least one of the following beneficial technical effects: 1. Automatically sort and feed materials using a preset sorting and feeding method. The knocking sound information is compared with the reference spectrum. The data difference is used to accurately distinguish between film-coated and non-film-coated types, providing a basis for subsequent processing. The number feature data in the license plate top view image accurately locates the spraying area, ensuring accurate spraying position and avoiding waste of spraying ink. 2. Generate a reaction force information curve based on continuous air blowing reaction force information, and analyze the magnitude of the curve average value and the reference force value to determine the orientation of the license plate. If there is an error, flip it to adjust it to avoid incorrect spraying orientation. 3. Determine whether to use the heating method based on the edge feature data of the film in the bottom image of the license plate; distinguish between the scraping method and the water injection method based on the bubble feature data in the film removal image. Different methods are adapted to different protective film conditions to ensure thorough film removal without damaging the license plate. Attached Figure Description

[0027] Figure 1 This is a structural schematic diagram of a license plate inkjet printer device according to this application; Figure 2 This is a schematic diagram of the feeding mechanism of this application; Figure 3 This is a schematic diagram of the flipping mechanism of this application; Figure 4 This is a flowchart of a control method for a license plate inkjet printer according to this application; Figure 5 This is a flowchart of the positive and negative adjustment method of this application; Figure 6 This is a flowchart of the film removal method of this application.

[0028] The parts referred to by the numbers in the above attached diagrams are as follows: 1. Printing mechanism; 2. Conveying mechanism; 3. Feeding mechanism; 31. Feeding rack; 32. Push plate; 33. Push cylinder; 34. Baffle; 35. Limit block; 4. Tilting mechanism; 41. Tilting frame; 42. Support frame; 43. Motor; 44. Lifting cylinder; 45. Mounting frame. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0030] This invention discloses a license plate inkjet printer device.

[0031] Reference Figure 1 A license plate inkjet printer includes an inkjet printing mechanism 1, a conveying mechanism 2, a feeding mechanism 3, and a flipping mechanism 4.

[0032] The printing unit 1 uses a UV curing inkjet printer, which is existing technology and will not be described in detail here.

[0033] The conveying mechanism 2 uses a double-row conveyor belt, with a middle spacing that allows the turning mechanism 4 to pass through. This is existing technology and will not be described in detail here.

[0034] In use, the feeding mechanism 3 pushes license plates one by one onto the surface of the conveying mechanism 2 for transport. If an error is detected in the front or back of the license plate, the flipping mechanism 4 is controlled to flip the license plate. After the flipping is completed, the license plate continues to be transported until it moves to the bottom of the inkjet printing mechanism 1. At this point, the inkjet printing mechanism 1 prints ink on the number position on the license plate, realizing automated coloring of the license plate, ensuring a stable and reliable printing process, and reducing ink waste.

[0035] Reference Figure 2 The feeding mechanism 3 includes a feeding frame 31, a push plate 32, a pushing cylinder 33, two baffles 34, and two limiting blocks 35. The feeding frame 31 is located at the feeding end of the conveying mechanism 2, and its upper surface is on the same horizontal plane as the conveying surface of the conveying mechanism 2. The push plate 32 is located on the feeding frame 31 and is slidably connected to the feeding frame 31. One end of the push plate 32 is fixedly connected to the output end of the pushing cylinder 33. The pushing cylinder 33 is fixedly installed on the feeding frame 31, and the pushing direction of the pushing cylinder 33 is towards the conveying mechanism 2. The two baffles 34 are symmetrically arranged and fixedly installed on the feeding frame 31. The gap between the two baffles 34 is a clearance groove 36 for the robot arm to pass through when placing license plates. The gap between the baffles 34 and the feeding frame 31 is a passage groove 37 for the license plate at the bottom of the feeding frame 31 to pass through. Two limiting blocks 35 are symmetrically arranged and fixedly installed on the feeding rack 31. The limiting blocks 35 are L-shaped and slide in contact with the push plate 32 to limit the sliding direction of the push plate 32.

[0036] In use, license plates are neatly stacked on the loading rack 31 between the baffles 34. The control of the push cylinder 33 drives the push plate 32 to move along the limit block 35 and the loading rack 31, so as to push the bottom license plate through the through groove 37 and move it to the conveying mechanism 2 for transportation. When the push plate 32 retracts, the license plate above falls to the bottom for cyclic loading, realizing the accurate pushing of the license plate to the conveying mechanism 2 and ensuring stable and continuous loading.

[0037] Reference Figure 3 The tilting mechanism 4 includes a tilting frame 41, a support frame 42, a motor 43, a lifting cylinder 44, and a mounting frame 45. The tilting frame 41 includes a rotating shaft and multiple tilting plates evenly arranged circumferentially on the outer side of the rotating shaft. The rotating shaft is rotatably mounted on the support frame 42, and the motor 43 is fixedly mounted on one side of the support frame 42. The output end of the motor 43 is connected to one end of the rotating shaft via a synchronous belt. The support frame 42 is slidably mounted on the mounting frame 45, and the lifting cylinder 44 is fixedly mounted on the mounting frame 45. The output end of the lifting cylinder 44 is fixedly connected to the bottom of the support frame 42.

[0038] In use, when the license plate moves along the conveyor mechanism 2 to the flipping frame 41, the motor 43 drives the rotating shaft to rotate via the synchronous belt, which in turn drives the flipping plate to rotate. The flipping plate then flips the license plate. After flipping, the license plate continues to move along the conveyor mechanism 2. The lifting cylinder 44 retracts, causing the support frame 42 to slide down along the mounting frame 45, thus avoiding moving license plates on the conveyor mechanism 2. The rotation of the flipping plate flips the license plate, preventing the inkjet printing mechanism 1 from mistakenly printing ink on the bottom surface of the license plate, improving the product qualification rate, and reducing ink waste.

[0039] Based on the same inventive concept, embodiments of the present invention provide a control method for a license plate inkjet printer.

[0040] Reference Figure 4 A control method for a license plate inkjet printer includes the following steps: Step 1: In response to a preset trigger signal, the license plates in the preset sorting station are sorted and fed to the preset conveying mechanism (2) using a preset sorting and feeding method.

[0041] After receiving the trigger information, the control system sorts the license plate and controls the robotic arm to place the license plate on the loading rack 31, and pushes it onto the double-row conveyor belt through the push plate 32 to complete the loading.

[0042] A trigger signal is an instruction signal that starts the control process of a license plate inkjet printer, such as a manual operation button or a sensor detecting a license plate to be processed.

[0043] The sorting station refers to a specific work area used to organize and position license plates.

[0044] The sorting and loading method refers to the standardized operating logic for adjusting disordered license plates into an ordered state. This is pre-set by staff in the control system. The specific method will be explained in detail in subsequent steps and will not be elaborated here.

[0045] Step 2: When the license plate is conveyed on the conveying mechanism 2, the license plate is adjusted to the front and back using a preset forward and reverse adjustment method, and the license plate is struck with a preset striking force, and the striking sound information is collected.

[0046] When the license plate is conveyed on the conveyor mechanism 2, the front and back orientation of the license plate is detected and the license plate is adjusted to the correct placement direction. Then, the hammer is controlled to strike the surface of the license plate.

[0047] A striking hammer is a device that uses pneumatic power to drive an impact head made of nylon or rubber to strike a license plate.

[0048] The forward and reverse adjustment method refers to the standardized operating logic for judging and adjusting the forward and reverse status of license plates. It is preset in the control system by the staff. The specific method will be explained in detail in the following steps and will not be repeated here.

[0049] The striking force refers to the magnitude of the force exerted by the hammer on the surface of the license plate, which is set by the staff based on experimental data and the hardware performance of the hammer.

[0050] The tapping sound information refers to the sound information generated when the license plate surface is tapped. It includes the acoustic characteristics that reflect the material of the license plate surface and is collected by a sound sensor that is pre-installed next to the tapping hammer.

[0051] Step 3: Compare the tapping sound information with the preset reference spectrum to determine the surface type. The surface type includes coated type and uncoated type.

[0052] The reference spectrum refers to the spectral data that distinguishes between license plates with and without film. It is generated by collecting sound signals through a large number of sample experiments and using Fourier transform, and is pre-stored in the control system by the staff.

[0053] The terms "with film type" and "without film type" refer to two states on the surface of a license plate, representing license plates with a transparent protective film and those without.

[0054] License plates with a protective film on their surface produce a different sound when struck compared to those without a film. Therefore, the sound of striking these two types of license plates can be used as a distinguishing feature to determine their surface type.

[0055] Step 40: Based on the type of film, remove the film from the license plate surface using a preset film removal method, and capture a top-view image of the license plate.

[0056] The film removal method refers to a series of standardized operating logics and specific means adopted when processing license plates with film on them in order to remove the protective film on the surface of the license plate. These methods are pre-set in the control system by the staff. The specific methods will be explained in detail in the following steps and will not be repeated here.

[0057] A license plate top-view image refers to image data taken from above the license plate. It can clearly reflect the information on the surface of the license plate. It is obtained by taking pictures with an industrial camera installed above the license plate and then performing noise reduction and enhancement processing.

[0058] When printing on license plates with protective film, the protective film on the surface of the license plate must be removed first before a top-down image of the license plate can be captured, in order to avoid printing directly on the surface of the protective film.

[0059] Step 41: Based on the non-film type, acquire a top-view image of the license plate.

[0060] Compared to license plates with film in step 40, license plates without film do not require film removal and can be directly captured as a top-view image in preparation for printing. The top-view image of the license plate has already been described in step 40 and will not be repeated here.

[0061] Step 5: Based on the preset number characteristics, obtain the spraying area from the top view image of the license plate, and spray the area.

[0062] Number features refer to the standardized features of license plate numbers, which are used to locate the area to be sprayed from the image. The image recognition parameters are preset based on the national standard for license plates and stored in the control system.

[0063] The spraying area refers to the specific area on the license plate surface that needs to be sprayed. Specifically, it is the area on the license plate used to print numbers, letters, and other markings. Its range must match the standard number layout of the license plate. The outline position of the number features is identified from the top view image of the license plate using the Canny operator algorithm. That is, the position of the number on the license plate is defined as the spraying area.

[0064] The material handling and loading method includes the following steps: Step 10: Obtain the license plate stack height in the sorting station, and filter out the maximum stack height from the license plate stack heights.

[0065] The license plate stacking height refers to the overall actual height of all stacked license plates in the sorting station, reflecting the stacking status of the license plates. The surface height of the sorting station is 0, obtained directly by a laser rangefinder pre-installed above the station.

[0066] When a laser rangefinder measures the height of license plate stacks, it will take measurements in multiple areas of the sorting station. Therefore, the height of license plate stacks is a data set with multiple data points.

[0067] The maximum stacking height refers to the license plate stacking height with the largest value among the measured stacking heights of multiple license plates. It is determined by the system through comparison and filtering of all the obtained license plate stacking heights.

[0068] Step 11: Set the leveling height according to the preset license plate height.

[0069] License plate height refers to the thickness of a single license plate, which can be preset according to the license plate specifications and stored in the system.

[0070] The pushing height refers to the vertical distance between the preset pushing structure and the surface of the sorting station when pushing the license plate. This height is preset by the operator and stored in the control system, and is a multiple of the license plate height. In this embodiment, the pushing height is set to twice the license plate height. This multiple is set by technicians based on the actual production process and will not be elaborated upon here.

[0071] Step 120: When the maximum stacking height is greater than the flattening height, control the preset pushing structure to push the license plate away at the flattening height, and repeat step 10.

[0072] When the maximum stacking height is greater than the flattening height, it means that the license plate stacking height exceeds the flattening height. In this case, the excessively high stacking of the license plate may cause the license plate to tilt or other disordered stacking, making it difficult to identify or clamp in subsequent steps.

[0073] The pushing structure is a horizontally set pushing plate on the sorting station. The vertical distance between the pushing structure and the surface of the sorting station can be adjusted according to the pushing height, and it can also be moved horizontally to push the license plate.

[0074] The pushing structure can push license plates above the pushing height to flatten them, leaving only those below the pushing height. These remaining license plates are then processed first in subsequent steps.

[0075] After the structure is pushed flat, other license plates may be covered again. Therefore, after each flattening, step 10 is repeated to re-collect the license plate stacking height to ensure that the license plate stacking height does not exceed the flattening height.

[0076] Step 121: When the maximum stacking height is not greater than the flattening height, collect an image of the license plate arrangement above the arrangement station.

[0077] When the maximum stacking height is no greater than the flattening height, it means that the license plate stacking height does not exceed the flattening height. In this embodiment, the flattening height is twice the height of the license plate, meaning that there is no situation where more than two license plates are stacked consecutively.

[0078] License plate sorting images refer to image data taken from above the sorting station, used to identify the position and stacking status of license plates. These images are obtained by taking pictures with an industrial camera preset above the sorting station and then undergoing noise reduction and enhancement processing.

[0079] When there are only a few license plates stacked at the sorting station, that is, only one or two license plates stacked, the arrangement of the license plates is ideal, and image recognition can be performed directly to determine the position of the license plates.

[0080] Step 13: Identify the complete license plate outline features from the license plate arrangement image, and determine the license plate placement status based on the complete license plate outline features and the preset reference direction.

[0081] The complete license plate outline feature refers to the shape outline formed by the complete outer boundary of the license plate in the license plate image. It is usually represented as a rectangle that conforms to the standard size of the license plate. The Canny operator algorithm is used to extract the pixels with abrupt changes in gray value. Then, the minimum bounding rectangle algorithm is used to process and filter the outline that conforms to the preset license plate size ratio. This is the complete license plate outline feature, and the corresponding license plate is located at the top without obstruction.

[0082] The reference direction refers to the standard orientation of the license plate, which is used as a reference to adjust the angle of the license plate. It is preset by the staff and entered into the system.

[0083] The license plate placement status refers to the specific placement of the license plate in the sorting station. It is determined based on the complete license plate outline features identified from the license plate sorting image. It usually includes information such as the tilt angle and orientation of the license plate. It is obtained by comparing and calculating the angle information of the complete license plate outline features with the preset reference direction.

[0084] Step 14: Determine the license plate clamping point and adjust the angle according to the license plate placement.

[0085] The license plate gripping point refers to the position where the license plate is gripped by a robotic arm. It is identified from the image of the license plate outline. In this embodiment, the center point of the shorter side of the license plate outline is taken as the license plate gripping point.

[0086] The adjustment angle refers to the angle value required to adjust the license plate from a tilted or deflected state to a reference direction. First, determine the current placement direction of the license plate based on its outline, and then calculate the angle difference between the current direction and the reference direction. The resulting difference is the adjustment angle.

[0087] Step 15: Clamp the license plate according to the clamping point, and rotate the license plate according to the adjustment angle to adjust the license plate to the standard placement position. After the adjustment is completed, transfer the license plate to the waiting area.

[0088] The robotic arm is controlled to grip the license plate at the gripping point, then rotates it according to the adjusted angle, and finally places the license plate in the loading area to wait for loading.

[0089] The waiting area refers to the temporary storage location of the sorted license plates when they are waiting for the subsequent loading steps. It is pre-set and entered into the system by the staff. In this embodiment, the waiting area is the area above the loading rack 31.

[0090] Reference Figure 5 The positive and negative adjustment method includes the following steps: Step 20: Clean the top and bottom surfaces of the license plate with air according to the preset cleaning path, and obtain continuous air reaction force information during the cleaning of the top surface of the license plate.

[0091] Because the shape of the license plate number is raised on one side and recessed on the other, the distance at which the airflow blown out by the high-pressure nozzle contacts the shape of the number varies, and the magnitude of the blowing reaction force information obtained is also different.

[0092] Air cleaning refers to the cleaning action performed by controlling a high-pressure air nozzle to spray air along the top and bottom surfaces of the license plate.

[0093] The cleaning path refers to the movement trajectory of the high-pressure air nozzle during cleaning. Its core is to ensure that the airflow can fully cover the license plate. Based on the standard size and shape of the license plate, and combined with the coverage range of the high-pressure air nozzle, a systematic movement trajectory is planned. In this embodiment, it can be set to an S-shape, and the staff stores the coordinate parameters corresponding to the trajectory in the system.

[0094] The airflow reaction force information refers to the reaction force generated by the airflow acting on the top surface of the license plate, which is acquired by a pressure sensor installed on the high-pressure nozzle. This airflow reaction force information is a continuously changing value, not a discrete point.

[0095] In this embodiment, during the air blowing cleaning process, the air blowing reaction force information is collected simultaneously.

[0096] Step 21: Generate a reaction force information curve based on the continuous blowing reaction force information, and analyze the average value of the curve.

[0097] The reaction force information curve refers to the curve formed by arranging the continuously collected air blowing reaction force information in chronological order or cleaning path order. It can reflect the changing trend of reaction force during the air blowing process. The continuously acquired reaction force information is integrated as the horizontal and vertical axes of the two-dimensional coordinate system according to the collection order to form the corresponding reaction force information curve.

[0098] The curve average value refers to the average value obtained after statistical calculation of all valid data covered by the reaction force information curve. It is the core basis for judging the positive and negative status of the license plate and is directly obtained by the system from the analysis of the reaction force information curve.

[0099] Step 220: When the average value of the curve is greater than the preset reference force value, control the conveying mechanism 2 to continue conveying the license plate and enter the pre-film removal preparation state.

[0100] The reference force value refers to the reaction force experienced by the high-pressure nozzle when blowing air onto a non-convex / concave area of ​​the license plate surface under normal conditions. It is determined by staff through experimental testing and data analysis and then entered into the system.

[0101] The fact that the average value of the curve is greater than the preset reference force value means that the air reaction force detected by the high-pressure nozzle when it passes through a certain position during the air blowing cleaning process is greater than the reference force value. This indicates that the convex side of the license plate is facing up when it is being conveyed on the conveying mechanism and is in the correct loading and placement state. At this time, the license plate can continue to be conveyed by the conveying mechanism 2 without the need to flip the license plate.

[0102] Step 221: When the average value of the curve is less than the reference force value, control the license plate to flip.

[0103] If the average value of the curve is less than the reference force value, it means that the air reaction force detected by the high-pressure nozzle when it passes through a certain position during the air blowing cleaning process is less than the reference force value. This indicates that the license plate is in an incorrect loading and placement state when it is being transported on the conveying mechanism with the concave side facing up. At this time, the flipping mechanism 4 is controlled to flip the license plate to adjust it to the correct loading and placement state.

[0104] Reference Figure 6 The membrane removal method includes the following steps: Step 400: Acquire the bottom image of the license plate below the license plate, and identify whether there are preset membrane edge features from the bottom image of the license plate.

[0105] The license plate bottom image refers to image data taken from below the license plate, used to determine the coverage status of protection. It is obtained by taking pictures with an industrial camera preset below the license plate.

[0106] The edge features of the protective membrane refer to the image features of the edge of the protective membrane. They are obtained by training with sample images, pre-setting the pixel grayscale range and shape features of the edge of the membrane, and then using the Canny operator algorithm to identify them from the bottom image of the license plate.

[0107] The difference between a license plate with and without edge features lies in whether the protective film on the top of the license plate extends to cover the bottom. By detecting these edge features, the coverage method of the protective film can be determined. Step 4010: When there are no film edge features, use the preset heating method to heat and remove the film from the top surface of the license plate.

[0108] The absence of a pre-defined edge feature indicates that the protective film does not cover the bottom surface of the license plate, but only exists on the surface of the license plate that needs to be printed. In this case, the system removes the film by heating the top surface of the license plate. The heating method will not be described in detail here, but will be explained in detail in subsequent embodiments.

[0109] Step 4011: When film edge features exist, blow air from the bottom of the license plate at a preset preheating temperature, acquire a license plate film removal image above the license plate, and identify whether preset bubble features exist from the license plate film removal image.

[0110] Control the high-pressure air nozzle to blow air upwards from the bottom of the license plate for heating.

[0111] The presence of preset edge features indicates that the protective film covers both the edges and bottom of the license plate.

[0112] The preheating temperature refers to the temperature of the gas when the high-pressure nozzle blows air at the bottom of the license plate. It is used to heat the license plate so that the residual air in the protective film expands and forms bubbles. The specific value is calculated by the staff based on the material, thickness and characteristics of the protective film and the license plate substrate and then pre-entered into the system.

[0113] License plate film removal images refer to image data taken from above the license plate, used to analyze whether there are air bubbles on the surface of the protective film. These images are obtained by taking pictures with an industrial camera preset above the license plate.

[0114] Bubble features refer to the image characteristics of bubbles formed by residual air between the protective film and the license plate. They generally present a circular or elliptical outline. The Canny operator algorithm is used to identify the bubbles by preset recognition parameters based on their visual characteristics and inputting them into the system.

[0115] In this embodiment, by blowing hot air at the bottom of the license plate, the purpose is to control the presence of air bubbles in the protective film of the license plate as much as possible, so as to facilitate subsequent processing of the protective film.

[0116] Step 40120: When there are no bubble features, use the preset scraping method to scrape and remove the film from the edge of the license plate.

[0117] The absence of bubble features means that no valid, usable bubbles can be identified on the license plate surface.

[0118] The scratching method refers to controlling the scratching block to slide and scratch along the edge of the license plate surface to break through the protective film and then remove it. The specific method will be explained in detail in the following steps, and will not be repeated here.

[0119] Step 40121: When air bubble features are present, use the preset water injection method to inject water to remove the film from the air bubble features on the top surface of the license plate.

[0120] The presence of bubbles indicates that there are clear bubbles on the surface of the license plate.

[0121] The water injection method involves injecting water into air bubbles to separate the protective film from the license plate surface, which is then removed. This method is safer and more effective than the scratching method, ensuring that the license plate is not damaged. The specific method will be explained in detail in the following steps, and will not be repeated here.

[0122] The heating method includes the following steps: Step 4020: Heat the top surface of the license plate with air at a preset heating temperature and capture an image of the protective film shrinking above the license plate.

[0123] Heating temperature refers to the temperature at which the high-pressure air nozzle heats the top surface of the license plate, causing the protective film on the top surface of the license plate to shrink due to heat, making it easier to remove later. It is a fixed temperature value determined based on the material properties of the protective film, the heat resistance limit of the license plate substrate, and a large number of experimental tests, and is pre-stored in the system by the staff.

[0124] Protective film shrinkage images refer to image data captured after heating the top surface of the license plate. These images are used to observe the shrinkage state of the film and are obtained by an industrial camera positioned above the license plate.

[0125] Step 4021: Obtain the shrinkage profile from the protective film shrinkage image based on the preset shrinkage features.

[0126] Shrinkage features refer to the curling and wrinkling of the edges of the protective film after it shrinks due to heat. It generally presents a wavy or lotus leaf shape. The Canny operator algorithm is used to identify the gray value abrupt change lines at the edges of the shrinkage image, and then the results are obtained through contour filtering.

[0127] The shrinkage contour refers to the contour line formed by the shrinkage features in the shrinkage image of the protective film, that is, the edge contour of the shrunken protective film. It is obtained by identifying the position of the shrinkage features in the shrinkage image of the protective film using the Canny operator algorithm.

[0128] Step 4022: Identify the apex position of the shrinkage profile and use one of the apex positions of the profile as the film removal clamping point according to the preset reference point.

[0129] The vertex position of the contour refers to the vertex in the shrinking contour that has a significant change in direction. It usually corresponds to the geometric vertex of the shrinking protective film. It is obtained by calculating the corner response function of each pixel in the shrinking image of the protective film using the Harris corner detection algorithm and verifying the direction.

[0130] The film removal clamping point refers to the position where the robot grips the top corner of the shrunken protective film. In this embodiment, the distance between the top corner of the contour and the reference point preset by the worker can be measured, and the closest top corner of the contour can be set as the film removal clamping point.

[0131] Step 4023: Connect the apex positions of the diagonal contours to obtain the film removal path.

[0132] The film removal path refers to the path the robot moves after clamping the top corner of the protective film. It is used to remove the protective film from the license plate surface and can be obtained by connecting the film removal clamping point to the top corner of the profile that is furthest away from it.

[0133] Step 4024: The protective film is clamped based on the film removal clamping point and the film removal path is controlled to move the protective film away from the license plate surface, thereby removing the film.

[0134] The robotic arm is controlled to grip the film removal point and then move along the film removal path, thereby causing the protective film to detach from the license plate surface and complete the removal.

[0135] The scraping method includes the following steps: Step 4030: Obtain the edge contour of the license plate based on the removed image of the license plate.

[0136] The license plate edge contour refers to the outer edge contour of the license plate, which can be extracted from the license plate image after the film is removed using the Canny operator algorithm.

[0137] Step 4031: Determine the movement path and blowing direction based on the edge contour of the license plate.

[0138] The movement path refers to the standardized movement trajectory of the squeegee when it acts on the protective film. The trajectory can be directly set according to the ring-shaped rectangle formed by the edge position to generate the coordinate path, i.e., the movement path.

[0139] The blowing direction refers to the direction in which the airflow from the high-pressure nozzle points, forming a certain angle with the license plate surface. This is used to blow off the protective film on the license plate surface. It can be set to an angle of 30° to 45° with the moving direction of the scraper block, and it always points towards the center of the license plate.

[0140] A scraper is a specialized tool that uses a pneumatically driven rubber scraper to precisely peel off the protective film from a license plate.

[0141] Step 4032: Scratch the license plate based on the movement path, and move the air synchronously based on the movement path and the air blowing direction to form a preset raised edge feature.

[0142] The edge lifting feature refers to the visual features such as shadows and angle shifts that appear in the image when the edge of the protective film separates and lifts up from the license plate. It is identified and obtained in the image by combining Hough line detection with the Canny operator algorithm.

[0143] Control the scraping block to move along the moving path to adhere to the edge of the license plate in order to cut the protective film. At the same time, control the high-pressure air nozzle to move along the air blowing direction to follow the scraping block and blow air to blow up the protective film.

[0144] Step 4033: Identify the raised edge features from the license plate decoction image, determine the location of the raised edge features, and define it as the raised edge position.

[0145] The curled edge position refers to the specific coordinate position of the curled edge of the protective film in the image, which is obtained by extracting the coordinate value of the corresponding position of the curled edge feature in the image.

[0146] The presence of a pre-defined curled edge indicates that the protective film has been scratched and can be removed.

[0147] Step 4034: Determine the film removal path based on the location of the raised edge and the license plate film removal image.

[0148] The film removal path refers to the standardized movement trajectory for performing the film removal operation, which is used to accurately remove the protective film. Starting from the raised edge position, the trajectory extending towards the center of the license plate in the film removal image is the film removal path.

[0149] Step 4035: Control the preset adhesive roller to stick the protective film at the curled edge position, roll it according to the film removal path to adhere it to the license plate surface, and blow air synchronously with a preset blowing force to remove the protective film.

[0150] Adhesive rollers are rollers with an adhesive surface that can rotate. They can be used to adhere protective film to the surface of license plates.

[0151] The blowing force refers to the force of the airflow ejected by the high-pressure air nozzle as it moves with the viscous roller. It is used to ensure that the viscous roller can lift the protective film. It is a fixed force value determined based on the material properties of the protective film and a large number of experimental tests, and is pre-stored in the system by the staff.

[0152] In this embodiment, the adhesive roller is first controlled to stick the curled edge of the protective film, and then the adhesive roller is controlled to roll along the film removal path. During the rolling process, the high-pressure air nozzle is simultaneously controlled to blow air at the critical position where the protective film and the license plate are stuck together to further separate the two. At this time, the protective film can be removed by the adhesive roller.

[0153] The water injection method includes the following steps: Step 4040: Analyze the bubble features from the license plate decoction image to determine the bubble location.

[0154] The bubble position refers to the specific coordinates of the bubble formed by residual air between the protective film and the license plate on the top surface of the license plate. It is obtained by identifying the position coordinates of the bubble feature in the license plate film removal image.

[0155] Step 4041: Measure the distance based on the preset center position and bubble position, filter out the bubble position closest to the center position and define it as the insertion position.

[0156] The center position refers to the geometric center coordinates of the license plate in the image. It is calculated by finding the intersection of the diagonals of the license plate outline in the image after the film is removed.

[0157] The insertion position refers to the specific coordinates of the water injection point in the bubble of the protective film, that is, the center coordinates of the bubble closest to the center of the license plate.

[0158] After determining the positions of all bubbles, the distance of each bubble position to the center position is compared and analyzed, and the insertion positions are selected from these. Water is then injected from the insertion positions, allowing the water to fill the gap between the license plate and the protective film more effectively.

[0159] Step 4042: Based on the insertion position, control the preset injection device to inject water into the bubble feature to separate the protective film from the license plate surface, control the expansion part preset at the end of the injection device to expand in the bubble feature, and simultaneously take away the protective film when the injection device is retracted, and blow air to dry the license plate surface.

[0160] An injection device refers to a robotic arm equipped with a terminal injection needle, the end of which has an expandable extension.

[0161] The robotic arm is controlled to insert the water injection needle at the insertion position and start injecting water. The water flow enters the air bubble and gradually separates the protective film from the license plate. Then, the expansion part is controlled to unfold. When the robotic arm drives the water injection needle away, the expansion part drives the protective film to detach synchronously. Finally, air is sprayed onto the surface of the license plate through a high-pressure nozzle for drying.

[0162] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A control method for a license plate inkjet printer, characterized in that, include: Step 1: In response to the preset trigger signal, the license plates in the preset sorting station are sorted and fed to the preset conveying mechanism (2) using the preset sorting and feeding method. Step 2: When the license plate is conveyed on the conveying mechanism (2), the license plate is adjusted to the front and back using a preset forward and reverse adjustment method, the license plate is struck with a preset striking force, and the striking sound information is collected. Step 3: Compare the tapping sound information with the preset reference spectrum to determine the surface type. The surface type includes coated type and uncoated type. Step 4: Based on the type of film, remove the film from the license plate surface using a preset film removal method, and capture a top-view image of the license plate. Based on the non-film type, capture the top view image of the license plate; Step 5: Based on the preset number characteristics, obtain the spraying area from the top view image of the license plate, and spray the area. The sorting and feeding method includes: Step 10: Obtain the license plate stack height in the sorting station, and filter out the maximum stack height from the license plate stack heights; Step 11: Set the leveling height according to the preset license plate height; Step 12: When the maximum stacking height exceeds the flattening height, control the preset pushing structure to push the license plate away at the flattening height, and repeat step 10. When the maximum stacking height is not greater than the flattening height, collect images of license plate sorting above the sorting station; Step 13: Identify the complete license plate outline features from the license plate arrangement image, and determine the license plate placement status based on the complete license plate outline features and the preset reference direction; Step 14: Determine the license plate clamping point and adjust the angle according to the license plate placement; Step 15: Clamp the license plate according to the clamping point, and rotate the license plate according to the adjustment angle to adjust the license plate to the standard placement position. After the adjustment is completed, transfer the license plate to the waiting area. Positive and negative adjustment methods include: Step 20: Clean the top and bottom surfaces of the license plate with air according to the preset cleaning path, and obtain continuous air reaction force information during the cleaning of the top surface of the license plate; Step 21: Generate a reaction force information curve based on the continuous blowing reaction force information, and analyze the average value of the curve; Step 22: When the average value of the curve is greater than the preset reference force value, control the conveying mechanism (2) to continue conveying the license plate and enter the pre-film removal preparation state. When the average value of the curve is less than the reference force value, the license plate is flipped. Membrane removal methods include: Step 400: Acquire an image of the bottom of the license plate below the license plate, and identify whether there are preset membrane edge features from the bottom image of the license plate; Step 401: When there are no film edge features, use a preset heating method to heat and remove the film from the top surface of the license plate. When film edge features are present, air is blown from the bottom of the license plate at a preset preheating temperature. An image of the license plate above the film removal is acquired, and the presence of preset bubble features is identified from the film removal image. When no air bubble features are present, the preset scraping method is used to scrape and remove the film from the edge of the license plate. When air bubbles are present, the preset water injection method is used to remove the film from the air bubbles on the top surface of the license plate.

2. The control method for a license plate inkjet printer according to claim 1, characterized in that, The heating method includes: Step 4020: Heat the top surface of the license plate with air at a preset heating temperature and capture an image of the protective film shrinking above the license plate; Step 4021: Obtain the shrinkage profile from the protective film shrinkage image based on the preset shrinkage features; Step 4022: Identify the apex position of the shrinkage profile and use one of the apex positions of the profile as the film removal clamping point according to the preset reference point. Step 4023: Connect the apex positions of the diagonal contours to obtain the film removal path; Step 4024: The protective film is clamped based on the film removal clamping point and the film removal path is controlled to move the protective film away from the license plate surface, thereby removing the film.

3. The control method for a license plate inkjet printer according to claim 1, characterized in that, The scraping method includes: Step 4030: Obtain the edge contour of the license plate based on the removed image of the license plate; Step 4031: Determine the movement path and blowing direction based on the edge contour of the license plate; Step 4032: Scratch the license plate based on the movement path, and move the air synchronously based on the movement path and the air blowing direction to form a preset curled edge feature; Step 4033: Identify the raised edge features from the license plate decoction image, determine the location of the raised edge features, and define it as the raised edge position; Step 4034: Determine the film removal path based on the location of the curled edge and the license plate film removal image; Step 4035: Control the preset adhesive roller to stick the protective film at the curled edge position, roll it according to the film removal path to adhere it to the license plate surface, and blow air synchronously with a preset blowing force to remove the protective film.

4. The control method for a license plate inkjet printer according to claim 1, characterized in that, The water injection method includes: Step 4040: Analyze the bubble features from the license plate delamination image to determine the bubble location; Step 4041: Measure the distance based on the preset center position and bubble position, filter out the bubble position closest to the center position and define it as the insertion position; Step 4042: Based on the insertion position, control the preset injection device to inject water into the bubble feature to separate the protective film from the license plate surface, control the expansion part preset at the end of the injection device to expand in the bubble feature, and simultaneously take away the protective film when the injection device is retracted, and blow air to dry the license plate surface.

5. A license plate inkjet printer device, controlled by a control method for a license plate inkjet printer as described in any one of claims 1 to 4, comprising an inkjet printing mechanism (1) for spraying ink to color the license plate, characterized in that, Also includes: The conveying mechanism (2) is located below the inkjet printing mechanism (1) and is used to transport license plates sequentially. The feeding mechanism (3) is located at the feeding end of the conveying mechanism (2) and is used to push the license plate for feeding; The feeding mechanism (3) includes: The loading rack (31) is used to place license plates in preparation for loading. The push plate (32) is slidably arranged along the loading rack (31) and is used to move the license plate onto the conveying mechanism (2); A push cylinder (33) is fixedly connected to one end of the push plate (32) to drive the push plate (32) to move toward the conveying mechanism (2); A flipping mechanism (4) is also provided below the conveying mechanism (2); The flipping mechanism (4) includes: A flipping frame (41) is located below the conveying mechanism (2) and is used to rotate to flip the license plate. The support frame (42) is rotatably connected to the flipping frame (41) and is used for the flipping frame (41) to be rotatably installed; The motor (43) is fixedly mounted on the support frame (42) and its output end is fixedly connected to one side of the flipping frame (41) for driving the flipping frame (41) to rotate; A lifting cylinder (44) is located below the support frame (42) and its output end is fixedly connected to the support frame (42). It is used to drive the support frame (42) to move up and down to selectively flip the license plate. The mounting bracket (45) is fixedly connected to the lifting cylinder (44) and is slidably connected to the support frame (42) for installation of the lifting cylinder (44) and for limiting the lifting path of the support frame (42).

6. The license plate inkjet printer device according to claim 5, characterized in that, The feeding mechanism (3) also includes: A baffle (34) is fixedly installed on the loading rack (31) and has a gap between it and the loading rack (31) on the side facing the conveying mechanism (2). The baffle (34) is used to limit the number of license plates loaded at one time. The limiting block (35) is fixedly installed on the feeding rack (31) and slidably connected to the push plate (32), and is used to limit the sliding direction of the push plate (32).

Images