A calibration method for a vision dispensing machine

Abstract

The present invention provides a calibration method for a vision dispensing machine, belonging to the technical field of dispensing machines. It solves the technical problems such as complex operation and large calibration error of the existing calibration methods for dispensing machines. The calibration method of this vision dispensing machine includes steps such as debugging the dispensing machine, recording the mechanical coordinates of the upper left corner of the working platform, recording the mechanical coordinates of the lower right corner of the working platform, spraying dots onto the working platform along a rectangular array and recording the mechanical coordinates of the spraying dot positions, taking pictures with a camera and recording the image coordinates of each glue dot, and hand-eye calibration. The present invention eliminates the calibration target, directly dots glue dots on the working platform through a dispensing gun, and then performs calibration by taking pictures of all glue dots at one time with a camera, with a faster calibration speed; the glue dots are directly placed on the working platform, there is no height difference, the accuracy is higher, and the influence of the swing arm tilt or the occlusion of items such as cylinders and air pipes is eliminated.

Description

Technical Field

[0001] The present invention belongs to the technical field of dispensing machines, and particularly relates to a calibration method for a vision dispensing machine. Background Art

[0002] Currently, existing dispensing machines generally include a machine table. A camera is provided above the machine table. A working platform and a dispensing gun are provided on the machine table. The dispensing gun is arranged above the working platform, and an oscillating arm for controlling the movement of the dispensing gun is provided on the machine table. Since the actual captured image of the camera is spherical and has a certain curvature, if the position of the dispensing gun is directly positioned based on the image captured by the camera, there will be a certain error during actual dispensing, and some high-precision dispensing work cannot be completed. Moreover, the error is greater closer to the edge of the working platform. To solve the above problems, it is necessary to calibrate each dispensing gun of the dispensing machine when it leaves the factory, so as to correct this error of the camera, make the position captured by the camera closer to the actual position where the dispensing gun is located after correction, and improve the working accuracy of the dispensing machine.

[0003] The existing calibration method requires removing the dispensing gun on the dispensing machine, and then installing a calibration target at the original position of the dispensing gun. At this time, the distance between the calibration target and the working platform is about 3 mm. Then, move the calibration target to the upper left corner of the working platform and save the position, and move the calibration target to the lower right corner of the working platform and save the position. During the formal calibration, the calibration target will move to the right along the X-axis (left and right direction) under the drive of the oscillating arm. After moving each unit length, the camera records the position of the center of the calibration target once until it moves to the right side of the working platform. Then, move down one unit distance along the Y-axis (up and down direction) and record, and then move left along the X-axis. After moving each unit length, the camera records the position of the center of the calibration target once until it moves to the left side of the working platform. Repeat the above calibration process until the calibration target moves to the lower right corner of the working platform to complete the calibration action.

[0004] The above calibration method has several deficiencies:

[0005] 1. During the movement of the calibration target, the center of the calibration target is easily blocked by objects such as the cylinder itself, the air pipe connected to the cylinder, and the calibration target itself. The camera cannot identify the center position of the calibration target, resulting in the inability to complete the calibration or a large error after calibration.

[0006] 2. During calibration, it is necessary to first remove the dispensing gun, then install the calibration target. After calibration, it is necessary to remove the calibration target and reinstall the dispensing gun, and the above disassembly and assembly process needs to be repeated for each dispensing gun. The operation is rather cumbersome. Errors will occur during the disassembly and assembly of the calibration target and the disassembly and assembly of the dispensing gun, resulting in the center position of the calibration target not being able to accurately correspond to the dispensing position of the dispensing gun, thus causing inaccurate calibration.

[0007] 3. When the swing arm moves, it may tilt, resulting in errors.

[0008] 4. There will definitely be a certain height difference between the calibration target and the upper surface of the working platform, generally about 3 mm. This height difference needs to be manually measured, and errors will occur during the measurement process. Moreover, the existence of the height difference itself will also cause certain calibration errors during calibration, thereby reducing the accuracy of the dispensing machine.

[0009] In view of the problems existing in the above calibration method, how to provide a calibration method that is more convenient to operate and has higher calibration accuracy. Summary of the Invention

[0010] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a calibration method for the accuracy of a vision dispensing machine that is more convenient to operate and has higher marking accuracy.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] A calibration method for a vision dispensing machine, characterized in that: the calibration method includes the following steps:

[0013] S1. Debug the dispensing machine, align the center of the camera with the center of the working platform, and inject glue into the dispensing gun.

[0014] S2. Drive the dispensing gun to move to the upper left corner of the working platform, and record the mechanical coordinates as (Xma, Yma); drive the dispensing gun to move to the lower right corner of the working platform, and record the mechanical coordinates as (Xmb, Ymb). The above recording of the mechanical coordinates of the upper left and upper right corners of the working platform is used to limit the dispensing range, and the dispensing range is controlled within a rectangular box with these two mechanical coordinates as the diagonal.

[0015] S3. Drive the dispensing gun to move along a rectangular array on the working platform. When the dispensing gun moves to the intersection of the rectangular array, record the mechanical coordinates (Xm1x, Ym1y) at this intersection, and then the dispensing gun moves downward and dots a circular glue point on the working platform as a calibration mark. The above rectangular array is within a rectangular box with mechanical coordinates (Xma, Yma) and mechanical coordinates (Xmb, Ymb) as the diagonal. The specific parameters of this rectangular array can be set according to needs, and can be a 4x4 array, 5x5 array, 6x6 array, 5x6 array, etc.

[0016] S4. After each point on the rectangular array is marked with a glue point, drive all the dispensing guns to move away from above the working platform, so that the entire working platform is exposed to the field of view of the camera.

[0017] S5. The camera takes a picture of the working platform, selects one circular glue dot as a template, and generates the pixel coordinates (Xpx, Ypy) at the center of each glue dot.

[0018] S6. Calculate the number of pixels between each pixel coordinate (Xpx, Ypy), compare it with the distance between the corresponding mechanical coordinates (Xm1x, Ym1y), and calculate the size of a single pixel. Specifically, calculate how many millimeters the side length of a single pixel is, thus completing the hand-eye calibration.

[0019] S7. Wipe off all the glue dots on the working platform.

[0020] S8. Drive the dispensing gun to move along a new rectangular array on the working platform. When the dispensing gun moves to the intersection of the rectangular array, record the mechanical coordinates (Xm2x, Ym2y) at this intersection, then the dispensing gun moves down and dots a circular glue dot on the working platform as a calibration mark. The above rectangular array is within a rectangular box with the mechanical coordinates (Xma, Yma) and the mechanical coordinates (Xmb, Ymb) as the diagonals. The specific parameters of this rectangular array can be set as needed, and it can be a 4x4 array, 5x5 array, 6x6 array, 5x6 array, etc. Further, in order to further improve the calibration accuracy, the number of calibration points can be appropriately increased, such as changing the array to a 6X8, 8X10, etc. rectangular array.

[0021] S9. After each point on the rectangular array is marked with a glue dot as a calibration mark, drive all the dispensing guns to move away from above the working platform, so that the entire working platform is exposed to the field of view of the camera.

[0022] S10. The camera takes a picture of the working platform and generates the image coordinates (Xix, Yiy) at the center of each glue dot.

[0023] S11. Compare each image coordinate (Xix, Yiy) with the actual mechanical coordinates (Xm2x, Ym2y), generate an error table, and complete the correction, thus realizing the calibration.

[0024] This calibration method eliminates the calibration target. The glue dots are directly dispensed on the working platform by a glue gun, and then all the glue dots are captured by a camera at one time. First, the hand-eye calibration is completed by comparing the pixel coordinates and the actual mechanical coordinates of the glue dots. Then, all the glue dots on the working platform are wiped off, and glue is dispensed on the working platform again. All the glue dots after dispensing are captured by the camera at one time, and the calibration is achieved by comparing the image coordinates and the actual coordinates of the new glue dots. There is no need to take pictures at each calibration point, and the calibration speed is faster. The glue dots are directly placed on the working platform, and the image coordinates (Xix, Yiy) of the glue dots are consistent with the coordinates of the calibration points that actually need to be calibrated, without height difference, and the accuracy is higher. Moreover, the influence of the swing arm tilt or the occlusion of items such as cylinders and air pipes is eliminated. Further, the position of the glue dots is the glue dispensing position on the working platform when the glue gun is working normally, and the consistency is better, which is conducive to improving the calibration accuracy. At the same time, there is no need to disassemble and assemble the glue gun, and the operation is simpler.

[0025] In the calibration method of a visual glue dispenser described above, the step S10 includes steps S101 and S102:

[0026] S101. After the camera takes a picture, identify whether there is a glue dot at each intersection of the rectangular array. If there is, jump to step S102; if not, wipe off all the glue dots on the working platform and return to step S8 again;

[0027] S102. Identify all the glue dots on the working platform and determine whether there are irregular glue dots that cannot accurately determine the center. If not, jump to step S11; if there are, wipe off all the glue dots on the working platform and return to step S8 again;

[0028] The designs of the above steps S101 and S102 can avoid the influence of the situation that the glue gun does not dispense glue dots or there are bad points caused by excessive glue injection on the calibration accuracy at step S8, which is conducive to further improving the calibration accuracy.

[0029] In the calibration method of a visual glue dispenser described above, it includes step S12: Wipe off all the glue dots on the working platform;

[0030] When there are two or more glue guns in this visual glue dispenser, after the first glue gun completes step S11, jump to step S12, and each subsequent glue gun repeats steps S8, S9, S10, S11 to step S12.

[0031] When there are two or more dispensing guns, this calibration method only needs to wipe off the glue dots on the working platform, and then it can calibrate another dispensing gun. There is no need to remove the calibration target from the position of the first dispensing gun and then install it at the position of the second dispensing gun. The operation is simpler and more convenient, the calibration speed is faster, and it can also avoid the errors caused by disassembling and assembling the calibration target, which is beneficial to improving the calibration accuracy.

[0032] In the above calibration method of a vision dispensing machine, the upper surface of the working platform is horizontally arranged.

[0033] The horizontally and smoothly arranged upper surface of the working platform can make the glue dots after dispensing be on the same horizontal plane, so that there is no height difference between the glue dots, which is beneficial to further improving the calibration accuracy.

[0034] In the above calibration method of a vision dispensing machine, the step S2 includes setting the actual height H of the lower layer. This height H represents the thickness of the center of the glue dot after dispensing. The glue material and the size of the glue dot may cause the height H to change. Generally, the height H is set to 0.4 mm.

[0035] After setting the actual height H of the lower layer, the computer can eliminate the error caused by the thickness of the glue dot, which is beneficial to further improving the calibration accuracy.

[0036] Compared with the prior art, the technical effects of the present invention are as follows:

[0037] This calibration method removes the calibration target, directly dispenses glue dots on the working platform through the dispensing gun, and then takes a one-time photo of all the glue dots through the camera. First, complete the hand-eye calibration by comparing the pixel coordinates and the actual mechanical coordinates of the glue dots, then wipe off all the glue dots on the working platform, dispense glue again on the working platform, and take a one-time photo of all the glue dots after dispensing through the camera. The calibration is achieved by comparing the image coordinates and the actual coordinates of the new glue dots. There is no need to take a photo at each calibration point, and the calibration speed is faster; the glue dots are directly placed on the working platform, and the image coordinates (Xix, Yiy) of the glue dots are consistent with the coordinates of the calibration points that actually need to be calibrated, there is no height difference, the accuracy is higher, and the influence of the swing arm tilt or the occlusion of items such as cylinders and air pipes is eliminated; further, the position of the glue dot is the dispensing position of the dispensing gun on the working platform during normal operation, and the consistency is better, which is beneficial to improving the calibration accuracy; at the same time, there is no need to disassemble and assemble the dispensing gun, and the operation is simpler. Description of the Drawings

[0038] Figure 1 is a schematic structural diagram of the vision dispensing machine of the present invention.

[0039] Figure 2 is a flowchart of the present invention.

[0040] In the figure, 1 is the machine platform; 2 is the working platform; 3 is the dispensing gun; 4 is the swing arm; 5 is the camera. Specific Embodiment

[0041] The following are specific embodiments of the present invention and in combination with the accompanying drawings, the technical solutions of the present invention will be further described, but the present invention is not limited to these embodiments.

[0042] The calibration method of this vision dispensing machine includes the following steps:

[0043] S1. Adjust the dispensing machine well, align the center of the camera 5 with the center of the working platform 2, and inject glue into the dispensing gun 3.

[0044] S2. Drive the dispensing gun 3 to move to the upper left corner of the working platform 2, and record the mechanical coordinates as (Xma, Yma); drive the dispensing gun 3 to move to the lower right corner of the working platform 2, and record the mechanical coordinates as (Xmb, Ymb); the above records of the mechanical coordinates of the upper left and upper right corners of the working platform 2 are used to define the dispensing range, and the dispensing range is controlled within a rectangular box with these two mechanical coordinates as the diagonal; set the actual height H of the lower layer. This height H represents the thickness of the center of the glue dot after dispensing, and the glue material and the size of the glue dot may cause the height H to change. Generally, the height H is set to 0.4 mm; after setting the actual height H of the lower layer, the computer can eliminate the error caused by the thickness of the glue dot, which is beneficial to further improving the calibration accuracy.

[0045] S3. Drive the dispensing gun 3 to move along a rectangular array on the working platform 2. When the dispensing gun 3 moves to the intersection of the rectangular array each time, record the mechanical coordinates (Xm1x, Ym1y) at this intersection, and then the dispensing gun 3 moves down and dots a circular glue dot on the working platform 2 as a calibration mark; the above rectangular array is within a rectangular box with the mechanical coordinates (Xma, Yma) and the mechanical coordinates (Xmb, Ymb) as the diagonal, and the specific parameters of this rectangular array can be set according to needs, and can be a 4x4 array, 5x5 array, 6x6 array, 5x6 array, etc.

[0046] S4. After each point on the rectangular array is marked with a glue dot as a calibration mark, drive all the dispensing guns 3 to move away from above the working platform 2, so that the entire working platform 2 is exposed to the field of view of the camera 5.

[0047] S5. The camera 5 takes a picture of the working platform 2, selects one of the circular glue dots as a template, and generates the pixel coordinates (Xpx, Ypy) at the center of each glue dot.

[0048] S6. Calculate the number of pixels between each pixel coordinate (Xpx, Ypy), compare it with the distance between the corresponding mechanical coordinates (Xm1x, Ym1y), and calculate the size of a single pixel. Specifically, calculate how many millimeters the side length of a single pixel is, thus completing the hand-eye calibration.

[0049] S7. Wipe off all the glue dots on the working platform 2.

[0050] S8. Drive the glue gun 3 to move along the new rectangular array on the working platform 2. When the glue gun 3 moves to the intersection of the rectangular array each time, record the mechanical coordinates (Xm2x, Ym2y) at this intersection, and then the glue gun 3 moves downward and dots circular glue dots on the working platform 2 as calibration marks. The above rectangular array is within a rectangular box with the mechanical coordinates (Xma, Yma) and the mechanical coordinates (Xmb, Ymb) as the diagonals. The specific parameters of this rectangular array can be set as needed, and it can be a 4x4 array, 5x5 array, 6x6 array, 5x6 array, etc. Further, in order to further improve the calibration accuracy, the number of calibration points can be appropriately increased, such as changing the array to a 6X8, 8X10, etc. rectangular array.

[0051] S9. After each point on the rectangular array is marked with a glue dot, drive all the glue guns 3 to move away from above the working platform 2, so that the entire working platform 2 is exposed to the field of view of the camera 5.

[0052] S10. The camera 5 takes a picture of the working platform 2 and generates the image coordinates (Xix, Yiy) at the center of each glue dot.

[0053] S101. After the camera 5 takes a picture, identify whether there is a glue dot at each intersection of the rectangular array. If there is, jump to step S102; if not, wipe off all the glue dots on the working platform 2 and return to step S8 again.

[0054] S102. Identify all the glue dots on the working platform 2 and determine whether there are irregular glue dots that cannot accurately determine the center. If not, jump to step S11; if there are, wipe off all the glue dots on the working platform 2 and return to step S8 again.

[0055] The designs of the above steps S101 and S102 can avoid the impact on the calibration accuracy caused by the situation that the glue gun 3 does not dot the glue dot or there are bad points caused by excessive glue injection during step S8, which is beneficial to further improving the calibration accuracy.

[0056] S11. Compare each image coordinate (Xix, Yiy) with the actual mechanical coordinates (Xm2x, Ym2y), generate an error table, and complete the correction, thus realizing the calibration.

[0057] S12. Wipe off all the glue dots on the working platform 2;

[0058] When there are two or more dispensing guns 3 in this vision dispensing machine, after the first dispensing gun 3 finishes step S11, jump to step S12, and each subsequent dispensing gun 3 repeats steps S8, S9, S10, S11 to step S12.

[0059] When there are two or more dispensing guns 3, this calibration method only needs to wipe off the glue dots on the working platform 2, then it can calibrate another dispensing gun 3 without removing the calibration target from the position of the first dispensing gun 3 and then installing it at the position of the second dispensing gun 3. The operation is simpler and more convenient, the calibration speed is faster, and it can also avoid the errors caused by disassembling and assembling the calibration target, which is beneficial to improving the calibration accuracy.

[0060] This calibration method removes the calibration target. The dispensing gun 3 directly dots glue dots on the working platform 2, and then the camera 5 takes pictures of all the glue dots at one time. First, complete the hand-eye calibration by comparing the pixel coordinates and the actual mechanical coordinates of the glue dots, then wipe off all the glue dots on the working platform 2, dot glue on the working platform 2 again, and the camera 5 takes pictures of all the glue dots after dotting at one time. Calibration is achieved by comparing the image coordinates and the actual coordinates of the new glue dots, without taking pictures at each calibration point, so the calibration speed is faster; the glue dots are directly placed on the working platform 2, and the image coordinates (Xix, Yiy) of the glue dots are consistent with the coordinates of the calibration points that actually need to be calibrated, without height difference, and the accuracy is higher, and the influence of the swing arm 4 tilting or the occlusion of items such as cylinders and air pipes is eliminated; further, the position of the glue dots is the dispensing position of the dispensing gun 3 on the working platform 2 during normal operation, with better consistency, which is beneficial to improving the calibration accuracy; at the same time, there is no need to disassemble and assemble the dispensing gun 3, and the operation is simpler.

[0061] Further, the upper surface of the working platform 2 is horizontally arranged. The horizontally and smoothly upper surface of the working platform can make the glue dots after dispensing be on the same horizontal plane, so that there is no height difference between each glue dot, which is beneficial to further improving the calibration accuracy.

[0062] The above embodiments are only preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope defined by the claims of the present invention.

Claims

1. A calibration method for a vision dispensing machine, characterized in that: The calibration method includes the following steps: S1. Adjust the dispensing machine well, align the center of the camera (5) with the center of the working platform (2), and inject glue into the dispensing gun (3). S2. Drive the dispensing gun (3) to move to the upper left corner of the working platform (2), and record the mechanical coordinates as (Xma, Yma); drive the dispensing gun (3) to move to the lower right corner of the working platform (2), and record the mechanical coordinates as (Xmb, Ymb). S3. Drive the dispensing gun (3) to move along a rectangular array on the working platform (2). When the dispensing gun (3) moves to the intersection of the rectangular array, record the mechanical coordinates (Xm1x, Ym1y) at this intersection. Then, the dispensing gun (3) moves downward and dots a circular glue dot on the working platform (2) as a calibration mark. S4. After each point on the rectangular array is marked with a glue dot, drive all the dispensing guns (3) to move away from above the working platform (2) so that the entire working platform (2) is exposed to the field of view of the camera (5). S5. The camera (5) takes a picture of the working platform (2), selects one of the circular glue dots as a template, and generates the pixel coordinates (Xpx, Ypy) at the center of each glue dot. S6. Calculate the number of pixel points between the respective pixel coordinates (Xpx, Ypy), compare it with the distance between the corresponding mechanical coordinates (Xm1x, Ym1y), and calculate the size of a single pixel point. S7. Wipe off all the glue dots on the working platform (2). S8. Drive the dispensing gun (3) to move along a new rectangular array on the working platform (2). When the dispensing gun (3) moves to the intersection of the rectangular array, record the mechanical coordinates (Xm2x, Ym2y) at this intersection. Then, the dispensing gun (3) moves downward and dots a circular glue dot on the working platform (2) as a calibration mark. S9. After each point on the rectangular array is marked with a glue dot, drive all the dispensing guns (3) to move away from above the working platform (2) so that the entire working platform (2) is exposed to the field of view of the camera (5). S10. The camera (5) takes a picture of the working platform (2) and generates the image coordinates (Xix, Yiy) at the center of each glue dot. S11. Compare each image coordinate (Xix, Yiy) with the actual mechanical coordinates (Xm2x, Ym2y), generate an error table, and complete the correction, thereby achieving calibration.

2. The calibration method of a vision dispensing machine according to claim 1, characterized in that: The step S10 includes steps S101 and S102: S101. After the camera (5) takes a picture, identify whether there is a glue dot at each intersection of the rectangular array. If so, jump to step S102; if not, wipe off all the glue dots on the working platform (2) and return to step S8 again. S102. Identify all the glue dots on the working platform (2), and determine whether there are irregular glue dots that cannot accurately determine the center. If not, jump to step S11; if so, wipe off all the glue dots on the working platform (2) and return to step S8 again.

3. A calibration method for a vision dispensing machine according to claim 1 or 2, characterized in that: Include step S12. Wipe off all the glue dots on the working platform (2). When there are two or more dispensing guns (3) of the present vision dispensing machine, after the first dispensing gun (3) completes step S11, it jumps to step S12, and each subsequent dispensing gun (3) repeats steps S8, S9, S10, S11 to step S12.

4. A calibration method for a vision dispensing machine according to claim 1 or 2, characterized in that: The upper surface of the working platform (2) is horizontally arranged.

5. A calibration method for a vision dispensing machine according to claim 1 or 2, characterized in that: The step S2 includes setting the actual lower layer height H.

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