CN113601158B - Bolt feeding pre-tightening system based on visual positioning and control method - Google Patents
Bolt feeding pre-tightening system based on visual positioning and control method Download PDFInfo
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- CN113601158B CN113601158B CN202110968814.4A CN202110968814A CN113601158B CN 113601158 B CN113601158 B CN 113601158B CN 202110968814 A CN202110968814 A CN 202110968814A CN 113601158 B CN113601158 B CN 113601158B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P19/00—Machines for simply fitting together or separating metal parts or objects, or metal and non-metal parts, whether or not involving some deformation; Tools or devices therefor so far as not provided for in other classes
- B23P19/04—Machines for simply fitting together or separating metal parts or objects, or metal and non-metal parts, whether or not involving some deformation; Tools or devices therefor so far as not provided for in other classes for assembling or disassembling parts
- B23P19/06—Screw or nut setting or loosening machines
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P19/00—Machines for simply fitting together or separating metal parts or objects, or metal and non-metal parts, whether or not involving some deformation; Tools or devices therefor so far as not provided for in other classes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P19/00—Machines for simply fitting together or separating metal parts or objects, or metal and non-metal parts, whether or not involving some deformation; Tools or devices therefor so far as not provided for in other classes
- B23P19/001—Article feeders for assembling machines
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
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Abstract
The invention discloses a bolt feeding pre-tightening system and a control method based on visual positioning, wherein the system comprises an upper computer control system, a robot and a tool clamp, wherein the robot is in communication connection with the upper computer control system, the tool clamp is arranged on the robot, a bolt grabbing and placing and pre-tightening assembly, a pneumatic control unit for driving the bolt grabbing and placing and pre-tightening assembly to act, and a visual assembly for photographing and positioning a bolt hole of a main bearing cover of an engine and guiding the robot to drive the bolt grabbing and placing and pre-tightening assembly to grab and pre-tighten the bolt are arranged on the tool clamp. Compared with the prior art, the invention improves the working quality, improves the feeding and pre-tightening efficiency of the bolts of the main bearing cap of the engine and reduces the production cost.
Description
Technical Field
The invention relates to the technical field of tightening control of assembly bolts of engines of automobiles and engineering vehicles, in particular to a feeding pre-tightening system and a control method of an engine main bearing cap bolt robot based on visual positioning.
Background
The connecting structure of main bearing caps and the like of the in-line four-cylinder four-stroke gasoline engine is a key component of the engine and mainly comprises an engine cylinder body, a bearing cap and a main bearing cap bolt. The main bearing cap of the engine is used for fixing the sliding bearing on the cylinder body, and the sliding bearing is used for supporting the crankshaft, so that the normal operation and power output of the crankshaft are ensured. The bolts of the main bearing cover provide enough stable pretightening force to tightly press the main bearing cover, so that the sliding bearing is fastened reliably.
The main bearing cap bolt is used as an important component of the connecting structure, and mainly fixes the main bearing cap and the crankshaft on the cylinder body, and the bolt is subjected to complex alternating load while the pretightening force is applied to the bolt. Because the working environment of the bolt is severe, if the pretightening force is too large, the bolt can be broken and fail; if the bolt pretightening force is too small, the main bearing cap is not clamped, and the main bearing cap and the bolt are damaged under alternating load; and thus cause the engine to malfunction and even threaten the life safety of the driver. Thus, the reliable connection of the main bearing cap bolts is ensured directly in relation to the reliability and stability of the engine.
At present, a plurality of multi-shaft automatic tightening devices and various efficient assembly methods are adopted on the automobile production lines at home and abroad to finish the assembly work of the bolt group connection of the main bearing cap of the engine, and the torque and the pretightening force are accurately controlled in the assembly connection. However, a special bolt feeding station is arranged before the screwing station, and the pre-connection bolts are placed into the bolt holes of the main bearing cover of the engine in a manual grabbing mode, so that preparation is made for automatic screwing and assembling of the bolts at the subsequent stations.
In the manual feeding mode of the bolt group, the problems of low working efficiency, slow beat and low automation degree exist.
Disclosure of Invention
The invention mainly aims to provide a bolt feeding pre-tightening system and a control method based on visual positioning, which aim to improve the working quality, improve the bolt feeding and pre-tightening efficiency of a main bearing cap of an engine and reduce the production cost.
In order to achieve the above purpose, the invention provides a bolt feeding pre-tightening system based on visual positioning, which comprises an upper computer control system, a robot and a fixture, wherein the robot is in communication connection with the upper computer control system, the fixture is arranged on the robot, a bolt grabbing and placing and pre-tightening assembly, a pneumatic control unit for driving the bolt grabbing and placing and pre-tightening assembly to act, and a visual assembly for photographing and positioning a bolt hole of a main bearing cover of an engine and guiding the robot to drive the bolt grabbing and placing and pre-tightening assembly to grab and pre-tighten the bolt are arranged on the fixture.
The fixture comprises a fixture assembly mounting plate and a fixture connecting plate which is perpendicular to the fixture assembly mounting plate, wherein a flange mounting structure which is connected with the robot is arranged at the center of the fixture connecting plate, and the bolt grabbing and placing and pre-tightening assembly and the vision assembly are mounted on the fixture assembly mounting plate.
The invention further adopts the technical scheme that the visual assembly comprises a camera, a telecentric lens and a coaxial light source which are sequentially arranged on the fixture assembly mounting plate from top to bottom.
The technical scheme of the invention is that the bolt grabbing and placing and pre-tightening assembly comprises a pre-tightening motor mounting plate, a linear guide rail, a sliding block, a stepping motor, a synchronous transmission belt and a bolt sleeve module, wherein the linear guide rail is mounted on the back surface of the pre-tightening motor mounting plate and is in sliding connection with the clamp assembly mounting plate through the sliding block, the stepping motor is mounted on the front surface of the pre-tightening motor mounting plate through a stepping motor flange mounting plate, and the stepping motor is connected with the bolt sleeve module through the synchronous transmission belt and is used for driving the bolt sleeve module to rotate and carrying out bolt pre-tightening operation.
According to the technical scheme, the bolt sleeve module is arranged on the pre-tightening motor mounting plate through two mounting seats and comprises a cylindrical sleeve, a tightening head, a synchronous pulley and a compression spring, wherein the cylindrical sleeve is sleeved outside the tightening head and the compression spring through a pin, the cylindrical sleeve can move up and down relative to the tightening head, the lower end of the compression spring is abutted against the pin, and the synchronous pulley is connected with the synchronous transmission belt.
The screw bolt feeding pre-tightening system further comprises an auxiliary motion module, wherein the auxiliary motion module comprises a fixed traction block, a floating joint, a cylinder, a magnetic switch and a throttle valve, the fixed traction block is arranged on the pre-tightening motor mounting plate below the stepping motor flange mounting plate, the floating joint is arranged between the cylinder and the fixed traction block, and the magnetic switch and the throttle valve are arranged at the bottom of the cylinder.
The pneumatic control unit comprises a vacuum generator and a gas filter which are arranged on the fixture assembly mounting plate, and the cylinder, the throttle valve, the floating joint, the fixed traction block and the magnetic switch are matched with the vacuum generator and the gas filter to form a pneumatic control mechanism.
According to the technical scheme, the pneumatic control mechanism further comprises an air compressor connected with the tool clamp.
The bolt feeding pre-tightening system based on visual positioning has the beneficial effects that: according to the technical scheme, the robot comprises an upper computer control system, a robot and a tool clamp, wherein the robot is in communication connection with the upper computer control system, the tool clamp is arranged on the robot, a bolt grabbing and placing and pre-tightening assembly, a pneumatic control unit for driving the bolt grabbing and placing and pre-tightening assembly to act, and a vision assembly for photographing and positioning a bolt hole of a main bearing cap of an engine and guiding the robot to drive the bolt grabbing and placing and pre-tightening assembly to grab and place and pre-tighten the bolt are arranged on the tool clamp, so that the working quality is improved, the bolt feeding and pre-tightening efficiency of the main bearing cap of the engine is improved, and the production cost is reduced.
In order to achieve the above purpose, the invention also provides a control method of a screw feeding pre-tightening system based on visual positioning, which is characterized in that the method is applied to the screw feeding pre-tightening system based on visual positioning, and the method comprises the following steps:
The upper computer control system acquires a bolt hole picture shot by the vision component;
processing the bolt hole picture to obtain a coordinate value of the bolt hole center point, and sending the coordinate value of the bolt hole center point to a robot;
and controlling the robot to grasp the bolt, and placing the bolt into the bolt hole for pre-tightening according to the coordinate value of the center point of the bolt hole.
The method comprises the steps of calibrating a visual component, calibrating a robot and a hand and eye of the visual component, matching templates of the shapes of the bolt holes, modeling a coordinate system of a module by taking the templates as the center, and performing secondary confirmation of the center position of the bolt hole by using a rounding tool.
The control method of the bolt feeding pre-tightening system based on visual positioning has the beneficial effects that: the invention adopts the technical scheme that: the upper computer control system acquires a bolt hole picture shot by the vision component; processing the bolt hole picture to obtain an accurate coordinate value of the bolt hole center point, and sending the coordinate value of the bolt hole center point to a robot; the robot is controlled to grasp the bolt, the bolt is placed into the bolt hole for pre-tightening according to the coordinate value of the center point of the bolt hole, the working quality is improved, the feeding and pre-tightening efficiency of the bolt of the main bearing cap of the engine is improved, and the production cost is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic view of the overall composition of a preferred embodiment of the visual positioning based bolt loading pre-tightening system of the present invention;
FIG. 2 is a schematic view of a first construction of a tool clamp of a preferred embodiment of a visual positioning based bolt loading pre-tightening system of the present invention;
FIG. 3 is a second schematic view of the tooling fixture of the preferred embodiment of the visual positioning based bolt feeding pre-tightening system of the present invention;
FIG. 4 is a schematic view of a third construction of a tool clamp of a preferred embodiment of the visual positioning based bolt feeding pre-tightening system of the present invention;
FIG. 5 is a schematic view of a first partial construction of the bolt pick-and-place and pretension assembly of the present invention;
FIG. 6 is an exploded view of the bolt sleeve module of the present invention;
FIG. 7 is a schematic view of a second partial construction of the bolt pick-and-place and pretension assembly of the present invention;
FIG. 8 is a partial schematic view of the auxiliary motion module of the present invention;
FIG. 9 is a system control flow diagram of the method for controlling a bolt feeding pre-tightening system based on visual positioning of the present invention;
FIG. 10 is a communication flow chart of a host computer and a robot of the control method of the bolt feeding pre-tightening system based on visual positioning;
FIG. 11 is an image processing flow chart of a control method of a bolt feeding pre-tightening system based on visual positioning;
FIG. 12 is a telecentric imaging model diagram;
FIG. 13 is a diagram of a robot hand-eye relationship;
fig. 14 is a threaded hole template matching diagram.
Reference numerals illustrate:
a robot 1; a network switch 2; a robot control cabinet 3; a robot demonstrator 4; an upper image processing computer 5; the automobile engine is to be assembled and screwed to the object 6; a material rack 7; a bolt 8; a tool clamp 9; a clamp assembly mounting plate 10; a jig connecting plate 11; a flange mounting structure 12; a camera 13; telecentric lens 14; a coaxial light source 15; pre-tightening the motor mounting plate 16; a linear guide rail 17; a slider 18; a stepping motor 19; a timing belt 20; a stepper motor flange mounting plate 21; a fixed traction block 22; a synchronous pulley 23; a mounting base 24; a cylindrical sleeve 25; tightening the cape head 26; a hold-down spring 27; a pin 28; a floating joint 29; a cylinder 30; a magnetic switch 31; a throttle valve 32; a vacuum generator 33; a gas filter 34; and an air compressor 35.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and rear … …) are included in the embodiments of the present invention, the directional indications are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.
In addition, if there is a description of "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" as it appears throughout includes three parallel schemes, for example "A and/or B", including the A scheme, or the B scheme, or the scheme where A and B are satisfied simultaneously. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
Considering the problems of low working efficiency, slow beat and low automation degree in a manual feeding mode of a bolt group in the prior art, the invention provides a bolt feeding pre-tightening system based on visual positioning. According to the invention, the vision assembly is utilized to provide the accurate position of the bolt hole of the main bearing cap of the engine for the robot, so that the robot is guided to realize the rapid automatic feeding of bolts of the bolt group, thereby improving the production efficiency and reducing the production cost; meanwhile, the suction nozzle in the cylindrical sleeve is used for grabbing and placing the bolt, so that the phenomenon that the bolt falls off or tilts in the process of grabbing and placing the bolt into the bolt hole is avoided, and the position accuracy before assembly is ensured; in addition, the stepping motor and the driving device are used for pre-tightening the placed bolts, so that the quick cap recognition and synchronous tightening of the shaft-pair bolts in the follow-up formal tightening procedure are facilitated.
Specifically, as shown in fig. 1 to 8, a preferred embodiment of the screw feeding pre-tightening system based on visual positioning of the present invention mainly includes a robot 1, a network switch 2, a robot control cabinet 3, a robot demonstrator 4, an upper image processing computer 5, an object 6 to be assembled and screwed by an automobile engine, a material rack 7 for placing screws 8 to be fed, a certain number of screws 8 to be fed and a fixture 9 mounted on a flange at the end of the robot 1. Wherein, the network switch 2, the robot control cabinet 3, the robot demonstrator 4 and the upper image processing computer 5 are mutually connected to form an upper computer control system.
The robot 1 is in communication connection with an upper computer control system, the fixture 9 is arranged on the robot 1, and the fixture 9 is provided with a bolt grabbing and placing and pre-tightening assembly, a pneumatic control unit for driving the bolt grabbing and placing and pre-tightening assembly to act, and a visual assembly for photographing and positioning a bolt hole of a main bearing cap of an engine and guiding the robot 1 to drive the bolt grabbing and placing and pre-tightening assembly to grab and place and pre-tightening the bolt 8.
The carrying capacity of the robot 1 should be greater than the load that the tool holder 9 mounted on the end flange of the robot 1 generates in three directions of the tool coordinates. Meanwhile, for the main bearing cap bolt group included in the to-be-assembled tightening object 6 of the automobile engine, for the in-line four-cylinder four-stroke gasoline engine selected in the embodiment, five bearing caps are required to be connected, ten main bearing cap bolts 8 are required to be picked up from the material frame 7 according to an assembly process specification and inserted into connecting through holes of the main bearing caps, pre-tightening operation is carried out on the lower half bolt hole part, assembly of a subsequent automatic tightening machine according to a set assembly method is ensured, and a crankshaft runs safely and reliably in the working process.
When in work, the upper computer control system establishes successful communication with the robot 1 and the vision component respectively; then, taking the geometric installation position of the screwing object 6 to be assembled of the automobile engine as rough positioning guide, moving the robot 1 to the upper side of the main bearing cover with the vision component to photograph the bolt hole, transmitting the photographed image and the current position of the robot 1 to the upper image processing computer 5, calling the image processing program by the upper image processing computer 5 to process the transmitted image and output the coordinate value of the center point of the bolt hole, reading the coordinate value of the center point of the bolt hole by the upper image processing computer 5, calculating and outputting the coordinate value of the center point of the bolt hole under the coordinate system of the robot tool to the robot 1, moving the robot 1 to the material frame 7 to grasp the bolt 8 after receiving the center coordinate value of the bolt hole, finally placing the bolt 8 into the corresponding bolt hole, controlling the stepping motor 19 to pretightening the bolt 8, and returning to the origin to wait for the beginning of the next task after ten bolts 8 are sequentially processed.
As shown in fig. 2 to 4, in the present embodiment, the tool fixture 9 includes a fixture assembly mounting plate 10, and a fixture connecting plate 11 perpendicular to the fixture assembly mounting plate 10, a flange mounting structure 12 connected to the robot 1 is disposed at a central position of the fixture connecting plate 11, and the bolt grabbing and pre-tightening assembly and the vision assembly are all mounted on the fixture assembly mounting plate 10.
In this embodiment, the fixture 9 is based on two fixture assembly mounting plates 10 and a fixture connecting plate 11 that are perpendicular to each other, and a flange mounting structure 12 for docking a sixth shaft flange of the robot is designed at the center position of the fixture connecting plate 11, so that the fixture 9 and the sixth shaft flange of the robot are conveniently mounted and connected by eight hexagon screws of M4; further, the installation of each component can be performed on the fixture component installation plate 10, including a visual component, a bolt grabbing and placing and pre-tightening component, an auxiliary movement module and the like, so that the positioning, grabbing and placing and pre-tightening work of the bolts 8 is realized.
Further, as shown in fig. 3, in the present embodiment, the vision assembly includes a camera 13, a telecentric lens 14, and a coaxial light source 15, which are disposed in this order from top to bottom.
In this embodiment, the camera 13, the telecentric lens 14 and the coaxial light source 15 are located at the left side of the fixture assembly mounting board 10, and the telecentric lens 14 is fixedly connected with the C interface of the camera 13 through screwing.
Further, as shown in fig. 5 to 7, the bolt grabbing and releasing and pre-tightening assembly comprises a pre-tightening motor mounting plate 16, a linear guide rail 17, a sliding block 18, a stepping motor 19, a synchronous transmission belt 20 and a bolt sleeve module, wherein the linear guide rail 17 is mounted on the back surface of the pre-tightening motor mounting plate 16 and is in sliding connection with the clamp assembly mounting plate 10 through the sliding block 18, the stepping motor 19 is mounted on the front surface of the pre-tightening motor mounting plate 16 through a stepping motor flange mounting plate 21, and the stepping motor 19 is connected with the bolt sleeve module through the synchronous transmission belt 20 and is used for driving the bolt sleeve module to rotate and performing pre-tightening operation of the bolt 8.
In this embodiment, the fixed traction block 22 is installed below the right stepping motor 19 of the bolt grabbing and releasing and pre-tightening assembly, so that the whole bolt grabbing and releasing and pre-tightening assembly moves in the Z-axis direction. The stepper motor 19 is mounted on the right side of the pre-tightening motor mounting plate 16 through a stepper motor flange mounting plate 21 and is connected with a synchronous pulley 23 of the left bolt sleeve module through a synchronous transmission belt 20 to provide a power source for pre-tightening of the bolts 8.
Further, in this embodiment, the bolt sleeve module is mounted on the left side of the pre-tightening motor mounting plate 16 through two mounting seats 24, and the bolt sleeve module includes a cylindrical sleeve 25, a tightening head 26, a synchronous pulley 23 and a compression spring 27, wherein the cylindrical sleeve 25 is sleeved outside the tightening head 26 and the compression spring 27 through a pin 28, the cylindrical sleeve 25 can move up and down relative to the tightening head 26, the lower end of the compression spring 27 abuts against the pin 28, and the synchronous pulley 23 is connected with the synchronous transmission belt 20.
Wherein, whole bolt sleeve module is in the cavity state, the flow of gas of being convenient for. The pneumatic control unit can enable partial vacuum to be formed in the cylindrical sleeve 25, suction force to the head of the bolt 8 is achieved, vacuum negative pressure is generated by the cylindrical sleeve 25 when the bolt 8 is grabbed, the bolt 8 is sucked, grabbed and put, and rotary pre-tightening action is achieved by matching with the stepping motor 19. In addition, the function of uniformly stressing the bolts and nuts is realized, so that the inclination of the bolts 8 caused by uneven stress in the grabbing and placing process is primarily avoided; the tightening head 26 is used for pre-tightening the bolts 8, and the power source is from the rotation of the synchronous transmission belt 20; when the tightening head 26 performs a pre-tightening rotation movement on the bolt 8, the compression spring 27 is used to ensure that the cylindrical sleeve 25 can be properly fed in the positive Z-axis direction and to maintain a certain axial pressure on the bolt 8.
Further, as shown in fig. 8, the bolt feeding pre-tightening system further includes an auxiliary motion module, the auxiliary motion module includes a fixed traction block 22, a floating joint 29, a cylinder 30, a magnetic switch 31, and a throttle valve 32, wherein the fixed traction block 22 is mounted on the pre-tightening motor mounting plate 16 below the stepper motor flange mounting plate 21, the floating joint 29 is mounted between the cylinder 30 and the fixed traction block 22, and the magnetic switch 31 and the throttle valve 32 are mounted at the bottom of the cylinder 30.
The pneumatic control unit includes a vacuum generator 33 and a gas filter 34 mounted on the jig assembly mounting plate 10, and causes negative pressure to be generated in the cylindrical sleeve 25 when the bolts 8 are gripped, thereby achieving gripping of the bolts 8.
As an embodiment, the pneumatic control unit further comprises an air compressor 35 connected to the tool fixture.
The cylinder 30, throttle valve 32, floating joint 29, fixed traction block 22, magnetic switch 31 cooperate with vacuum generator 33, gas filter 34, air compressor 35 to construct a pneumatic control mechanism.
The bolt feeding pre-tightening system based on visual positioning has the beneficial effects that: according to the technical scheme, the robot comprises an upper computer control system, a robot and a tool clamp, wherein the robot is in communication connection with the upper computer control system, the tool clamp is arranged on the robot, a bolt grabbing and placing and pre-tightening assembly, a pneumatic control unit for driving the bolt grabbing and placing and pre-tightening assembly to act, and a visual assembly for photographing and positioning a bolt hole of a main bearing cover of an engine and guiding the robot to drive the bolt grabbing and placing and pre-tightening assembly to grab and pre-tightening the bolt are arranged on the tool clamp, so that the working quality is improved, the feeding and pre-tightening efficiency of the main bearing cover of the engine is improved, and the production cost is reduced.
In order to achieve the above objective, the present invention further provides a method for controlling a screw feeding pre-tightening system based on visual positioning, and the method for controlling a screw feeding pre-tightening system based on visual positioning is applied to the screw feeding pre-tightening system based on visual positioning according to the above embodiment, and a preferred embodiment of the method for controlling a screw feeding pre-tightening system based on visual positioning includes the following steps:
the upper computer control system acquires a bolt hole picture shot by the vision component;
processing the bolt hole picture to obtain a coordinate value of a bolt hole center point, and sending the coordinate value of the bolt hole center point to the robot;
and controlling the robot to grasp the bolt, and putting the bolt into the bolt hole for pre-tightening according to the coordinate value of the center point of the bolt hole.
The method comprises the steps of processing the bolt hole pictures, namely calibrating a visual component, calibrating a robot and a hand and eye of the visual component, matching templates of the bolt hole shapes, modeling a module coordinate system by taking the templates as the center, and performing secondary confirmation of the center position of the bolt hole by using a circle finding tool.
Specifically, please refer to the system control flowchart shown in fig. 9.
In the initialization stage of the system workflow, an image processing computer serving as an upper computer control system respectively establishes successful communication with a robot and a camera; then, taking the geometric installation position of the object to be assembled and screwed up of the automobile engine as rough positioning guide, moving the robot to the upper side of the engine main bearing cover with a camera to photograph the bolt hole, transmitting the photographed picture and the current position of the robot to an upper computer control system, then calling an image processing program by the upper computer control system to process the transmitted image and output the coordinate value of the center point of the bolt hole, reading the coordinate value of the center point of the bolt hole by the upper computer control system, calculating and outputting the coordinate value of the center point of the bolt hole under the coordinate system of a robot tool to the robot, moving the robot to a material frame to grasp the bolt after receiving the center coordinate value of the bolt hole, finally placing the bolt into a corresponding bolt hole, controlling a stepping motor to pretightening the bolt, and returning to an origin to wait for the beginning of the next task after ten bolts are processed in sequence.
Referring to fig. 10, the system communication mode between the camera and the upper control system uses the Vision Gige protocol in ethernet communication to perform communication; the communication mode between the robot and the upper control system adopts Socket in TCP/IP protocol to establish communication, wherein the robot is used as a client, and the upper control system is used as a server. The communication flow between the robot and the upper control system is that the upper control system firstly creates a Socket, binds an IP address and a monitoring port, and after a monitoring queue is created, a server waits for the connection of a client in a blocking state until the client is connected, so that data can be received and transmitted; and then the robot serving as the client creates a Socket, establishes connection with a server in the upper computer control system, and can perform information interaction after the connection is successful.
Referring to fig. 11 and 12, the image processing flow includes calibration of the camera, hand-eye calibration between the robot and the camera, template matching of the bolt hole shape, establishment of a template coordinate system with the template center, and secondary confirmation of the bolt hole center position by using a circle finding tool. The whole visual processing process is that an upper image processing computer receives the image information of a camera through a network switch, and a control system of an upper computer in the upper image processing computer is used for calling a Visionpro visual processing program to finish. The calibration of the camera is mainly used for acquiring a matrix conversion relation from a world coordinate system to a camera coordinate system; the hand-eye calibration is used for acquiring a matrix conversion relation from a camera coordinate system to a robot tool coordinate system; the template matching is used for primarily positioning the bolt holes; establishing a template coordinate system by using the center of the template to preliminarily position the center position of the bolt hole; and further confirming the positions of the bolt holes according to the change of the gray level of the image by utilizing the characteristic that the spectra reflected by the bolt holes and the surrounding metal are inconsistent under the template coordinate system by using the circle finding tool.
The camera calibration, hand-eye calibration and template matching are described below.
1. Camera calibration
Because the clearance between the threaded hole on the main bearing cover of the automobile engine and the fastening bolt is only 0.2mm, the high positioning precision requirement is provided for the vision measuring system. The accuracy of the vision measurement system is affected by its resolution, its internal and external parameters, distortion parameters, and the like. In order to avoid the inherent characteristics of a camera lens and the purpose that the perspective distortion generated by installation factors influences the final measurement result of a vision measurement system, so that a bolt can be accurately placed in a threaded hole in a posture perpendicular to the end face of the threaded hole, the invention adopts an industrial camera with the resolution of 1230 ten thousand pixels to carry out camera calibration on a high-precision ceramic checkerboard calibration plate with the specification of 1 x 1mm and the appearance of 50 x 50mm as a target in the experimental preparation stage. Because the telecentric lens imaging model is a parallel imaging, most of the calibration methods of the pinhole model are not suitable for the calibration of the telecentric imaging model, the invention adopts the following methods to calibrate the telecentric imaging model:
as shown in FIG. 12, an imaging model of a telecentric lens employed in the present invention is shown in which 0 w (X w ,Y w ,Z w ) The world coordinate system is used as a unified coordinate system to describe the relative positions of all objects in space, and the camera coordinate system is O c (X c ,Y c ,Z c ) The optical axis of the camera is typically chosen to be directly the Z of the camera coordinate system c ，P 1 The (x, y) points are points in the world coordinate system where the P (Xw, yw, zw) points are imaged on the imaging plane image coordinate system.
Because telecentric lens imaging is in a parallel projection relationship, the image coordinate system can lose information on the Z axis in the imaging process, so telecentric lens imaging can be practically understood as that the obtained two-dimensional coordinate information is projected on the imaging surface of a camera through a certain magnification. Assuming that the lens magnification is m, the relationship between the camera coordinates and the image coordinates is that the external parameters of the telecentric lens lack information of parameter variation on the Z axis
Since the external parameters of the camera include the rotation matrix R and the translation vector T, which are parameters describing the positional conversion relationship between the world coordinate system and the image coordinate system, the telecentric lens model also conforms to the rule, so that the initial conversion relationship between the world coordinate and the image coordinate of the telecentric lens can be established, and the telecentric lens imaging model is shown in formula 2:
where (u, v, 1) is the pixel coordinates, (X) w ,Y w ,Z w ) Is the world coordinate, α and β are the axial magnification coefficients of the pixel coordinates, γ is the warping factor of the lens, and these parameters are the elements that constitute the internal parameter matrix a of the camera; r is (r) ij 、t ij Elements of rotation matrix and translation vector, K s Representing the external parameter matrix of the camera, P is a point on the world coordinate system.
Since telecentric lens also has some radial, tangential and Bao Lengjing distortions, and tangential and Bao Lengjing distortions are much smaller than radial distortions, radial distortions are dominant in telecentric lens distortions as a whole, and tangential and Bao Lengjing distortions are ignored here, then their radial distortion equations are:
wherein the radial distance
(x i ,y i ) Is ideal undistorted image coordinates, k 1 、k 2 … is the radial distortion coefficient.
In order to improve the calibration precision of all the internal parameters and the external parameters of the camera, nonlinear optimization processing is carried out on the obtained initial values of the parameters, and the optimization equation is as follows:
wherein x is * Is the minimum distance between the mark point on the target and the predicted pixel coordinate, n is the number of images, m is the mark point in the images, and p ij Is the pixel coordinate of the jth marking point in the extracted ith image,
is the corresponding predicted pixel coordinates, +.>
Is the camera external parameter matrix of the ith image, P j Is the j-th mark point of the target in the world coordinate system. This nonlinear optimization equation can be solved by the Levenberg-Marquardt algorithm.
In order to better reflect the accuracy of camera calibration, the accuracy of calibration is reflected here by the Root Mean Square Error (RMSE), the equation of which is as follows:
Where N is the number of marker points that can be identified by the camera, observed is the marker point on the target, and predicted is the corresponding predicted pixel point.
In order to solve the key parameters, the invention adopts the Perspolect AndRadiiaWarp algorithm in Vision Pro vision software to successively carry out projection and perspective distortion correction on the vision system, and the calibration steps are as follows:
step 1: the vision measurement system and the target are measured from two mutually perpendicular angles sequentially through the laser level meter, and meanwhile, the gesture of the vision measurement system is properly adjusted according to the measurement result of the laser level meter, so that the camera can be calibrated in a gesture of the vertical target in the process of calibrating the camera, and projection distortion caused by inclination is reduced;
step 2: adjusting the photographing height of the vision measurement system to a proper position according to the effective working distance of the telecentric lens, and simultaneously adjusting the photographing angle to enable the points on the target to enter into the field of view of the camera as much as possible;
step 3: inputting the information of the ceramic checkerboard calibration plate into Vision Pro vision software, triggering a camera to shoot at the same time, and calibrating the camera by adopting a Perspotive AndRadiaWarp algorithm;
step 4: the Perspotive AndRadiiaWarp algorithm further calibrates and corrects the internal and external parameters, distortion parameters and the like of the camera, so that the calibration precision of the camera is improved, the mapping relation between the image coordinates and the world coordinates is obtained, and the calibration result is fed back after calculation by using the formula 1.5;
Step 5: in order to ensure the accuracy of the calibration result and the visual observation of the calibration error, four angles and the center position of a Calipero measuring tool in a calibration image are adopted to respectively measure the sizes of grids at all positions after the calibration of the camera is finished;
step 6: comparing the grid size measured at each position in the step 5 with the ceramic calibration plate with the grid size of 1 x 1mm adopted by the invention, if the error value is larger, indicating that the calibration result error is larger, and carrying out calibration again; if the error is small or even negligible, the calibration result of this time can be used directly. The invention selects the result with the minimum calibration error as the calibration of the camera through the process of calibrating the camera for many times, and the calibration flow is finished.
2. Hand-eye calibration
In the robot vision positioning system, besides the parameters such as internal and external parameters and distortion of a camera, the relative pose relationship of the robot and the camera is required to be known, and the method for acquiring the pose relationship is to perform hand-eye calibration of the robot and the camera. For the Eye-in-hand system (namely, the form that the eyes are on hands and the camera is arranged at the tail end of the robot), the pose transformation relation of the camera coordinate system relative to the tail end coordinate system of the robot is obtained.
The relationship among the robot base coordinate W, the robot end coordinate system E, the camera coordinate system C, and the target coordinate system G is shown in FIG. 13, wherein T w Representing the conversion relation between the robot base coordinate system and the robot terminal coordinate system, T x Representing the conversion relation between the robot terminal coordinate system and the camera coordinate system, T c Representing the conversion relation between the camera coordinate system and the target coordinate system, T g The transformation relation T of the target coordinate system and the robot base coordinate system is shown below w The values of the joint variables are read by a robot controller and obtained through positive kinematic solution, T c The external parameters obtained from camera calibration are available, so the following equations are given according to the above-described conversion relationship:
T g ＝T w *T x *T c (6)
since the target is stationary and the camera is mounted on the workpiece at the end of the robot, T x 、T g Unchanged, T is set when the robot is in any position w ＝T 1 ,T c ＝T c1 The method comprises the steps of carrying out a first treatment on the surface of the Then changing the position and the posture of the tail end of the robot, setting T at the moment w ＝T 2 ,T c ＝T c2 Then there is
T 1 *T x *T c1 ＝T 2 *T x *T c2 (7)
Simple transformations were performed on equation 7, with:
(1/T 2 )*T1*Tx＝Tx*T c2 *(1/T c1 ) (8)
let a= (1/T 2 )*T 1 、B＝T c2 *(1/T c1 ) The hand and eye are closedThe basic relation of the system is
AT x ＝BT x (9)
The hand-eye calibration is to establish a calibration relation by obtaining A, B value through experiments, and calculate the conversion relation T between the robot terminal coordinate system and the camera coordinate system x Since the values of the camera coordinate system are not easy to directly obtain and the robot is directly applied to the end mounting tool, the pixel coordinate system and the robot tool coordinate system are used for indirectly replacing the camera coordinate system and the robot end coordinate system for hand-eye calibration.
The method for solving the conversion relation between the robot terminal coordinate system and the camera coordinate system at present comprises a two-step method of Tsai, a matrix direct product method, a nine-point calibration method and the like, and the method adopts the nine-point calibration method to calibrate the eyes and hands, and the calibration principle and the process are as follows:
the nine-point calibration method establishes a conversion relation between a robot tool coordinate system and a camera coordinate system by affine transformation, and the values of the camera coordinate system are not easy to directly obtain, so that the values of pixels in the pixel coordinate system are indirectly adopted to replace the values. Affine transformations are generally transformed in translation, rotation and scaling, with the transformation equations:
(u 0 ,v 0 1) is the pixel coordinates, S x And T x ' represents scaling and translation in the x-axis direction, respectively, S y And T y ' represents scaling and translation in the y-axis direction, respectively; θ represents the corresponding rotation angle, x 0 And y 0 Representing two-dimensional coordinates on a robot tool coordinate system, and then the corresponding hand-eye calibration conversion matrix H is as follows:
the conversion of equation 10 includes:
from equation 12, it can be known that at least 3 sets of values including pixel coordinates and robot tool coordinates are needed to calculate 5 unknowns, and we use 9 sets of values including pixel coordinates and robot tool coordinates to calculate an optimal solution, and use 9 sets of data to perform nonlinear optimization by referring to a least square method, where the nonlinear optimization equation is:
Wherein Q is x 、Q y Representing pixel coordinates, P x 、P y Representing the coordinates of the robot tool, H is a hand-eye calibration conversion matrix, i represents the number of the data set,
representing the optimal solution of the nonlinear optimization equation.
The hand-eye calibration experiment steps are as follows:
step 1: installing a calibration needle on a bolt sleeve on a workpiece unit at the tail end of the robot, and establishing a tool coordinate system for a calibration seat according to a six-point method (XZ), wherein the conversion relation between the tail end of the robot and the calibration needle on the sleeve is determined;
step 2: a nine-grid calibration plate with a solid circle pattern is placed under the visual field of the camera, and the camera is triggered to shoot the calibration plate;
step 3: the circle finding tool of Vision Pro visual software is utilized to sequentially find out the pixel coordinate values of the center points of the nine solid circles, and the uncorrected X, Y columns of the CogCalibNPointToNPointTool tool of the Vision Pro visual software are filled in;
step 4: the camera is static, the robot performs hand-eye calibration in a moving mode, the robot is controlled to sequentially align the center point positions of solid circles on the calibration plate with calibration needles on the sleeve, and tool coordinate system values at the nine solid circle positions are sequentially filled into an original corrected X, Y column of the CogCalibNPointToNPointTool tool of Vision Pro vision software;
Step 5: the degrees of freedom that need to be calculated in the CogCalibNPointToNPointTool tool selection are "scaling, aspect ratio, rotation, tilting, and translation", and click calculation correction to obtain a transformation matrix of the tool coordinate system and the pixel coordinate system.
Step 6: after the hand-eye calibration is completed, drawing 3 regular solid circles on different positions of the nine-grid calibration plate, and returning the camera to the original hand-eye calibration photographing position for photographing again;
step 7: and (3) acquiring the position of the center point of the solid circle in the step (6) by using a circle finding tool, simultaneously controlling the robot to carry out calibration aiming at the position of the center point of the solid circle in the step (6), and comparing the result obtained by the circle finding tool with the coordinate of the robot tool coordinate system at the position of the center point of the solid circle so as to confirm whether the whole calibration process meets the precision requirement or not, and if the precision requirement is not met, carrying out calibration again.
3. Template matching
In order to quickly and accurately find out a specific shape of interest in an image, a template matching method is adopted to quickly identify a threaded hole, a template matching process can be understood as selecting a specific region of interest as a template to slide from left to right and from top to bottom on the image to be detected, the template moves from left to right and from top to bottom by taking an upper left corner pixel point of the template as a unit each time from the upper left corner of a source image, and each time a pixel point is reached, an image with the same size as the template is cut from the source image by taking the pixel point as an upper left corner vertex, and the template is subjected to pixel comparison operation, and the matching degree is judged according to an operation result, wherein the square difference matching method is adopted in the invention, as shown in formula 14:
Wherein R (x, y) is a storage matrix of comparison operation results, T (x ', y') is a template image matrix, and I (x, y) is a source image matrix. The idea of template matching is to use the sum of squares of the differences of the template image pixels minus the covered source image pixels as the value of the point of the corresponding matrix, if the value is closer to 0, the higher the matching degree is. The result of template matching of threaded holes in the present invention is shown in fig. 14.
The control method of the bolt feeding pre-tightening system based on visual positioning has the beneficial effects that: the invention adopts the technical scheme that: the upper computer control system acquires a bolt hole picture shot by the vision component; processing the bolt hole picture to obtain an accurate coordinate value of a bolt hole center point, and transmitting the coordinate value of the bolt hole center point to the robot; the robot is controlled to grasp and put the bolt, the bolt is put into the bolt hole for pre-tightening according to the coordinate value of the center point of the bolt hole, the working quality is improved, the feeding and pre-tightening efficiency of the bolt of the main bearing cap of the engine is improved, and the production cost is reduced.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the specification and drawings of the present invention or direct/indirect application in other related technical fields are included in the scope of the present invention.
Claims (3)
1. The screw bolt feeding pre-tightening system based on visual positioning is characterized by comprising an upper computer control system, a robot and a tool clamp, wherein the robot is in communication connection with the upper computer control system, the tool clamp is arranged on the robot, a screw bolt grabbing and placing and pre-tightening assembly, a pneumatic control unit for driving the screw bolt grabbing and placing and pre-tightening assembly to act, and a visual assembly for photographing and positioning a screw bolt hole of a main bearing cap of an engine and guiding the robot to drive the screw bolt grabbing and placing and pre-tightening assembly to grab and place and pre-tighten the screw bolt are arranged on the tool clamp;
the fixture comprises a fixture assembly mounting plate and a fixture connecting plate which is perpendicular to the fixture assembly mounting plate, a flange mounting structure which is connected with the robot is arranged at the center position of the fixture connecting plate, and the bolt grabbing and placing and pre-tightening assembly and the vision assembly are both mounted on the fixture assembly mounting plate;
the screw bolt grabbing and placing and pre-tightening assembly comprises a pre-tightening motor mounting plate, a linear guide rail, a sliding block, a stepping motor, a synchronous transmission belt and a screw bolt sleeve module, wherein the linear guide rail is mounted on the back surface of the pre-tightening motor mounting plate and is in sliding connection with the clamp assembly mounting plate through the sliding block, the stepping motor is mounted on the front surface of the pre-tightening motor mounting plate through a stepping motor flange mounting plate, and the stepping motor is connected with the screw bolt sleeve module through the synchronous transmission belt and is used for driving the screw bolt sleeve module to rotate and performing screw bolt pre-tightening operation;
The bolt sleeve module is arranged on the pre-tightening motor mounting plate through two mounting seats and comprises a cylindrical sleeve, a tightening head, a synchronous pulley and a compression spring, wherein the cylindrical sleeve is sleeved outside the tightening head and the compression spring through pins, and the compression spring is sleeved at the opposite end of the tightening head; the cylindrical sleeve can move up and down relative to the tightening head, the lower end of the compression spring is abutted against the pin, and the synchronous pulley is connected with the opposite end of the tightening head; the synchronous belt wheel is connected with the synchronous transmission belt; the cylindrical sleeve is internally provided with partial vacuum to realize suction to the head of the bolt, and vacuum negative pressure is generated by the cylindrical sleeve when the bolt is grabbed so as to realize the suction, grabbing and placing of the bolt, and a stepping motor is matched to realize rotary pre-tightening action; the tightening head is used for pre-tightening the bolts, and the power source is from the rotation of the synchronous transmission belt; when the tightening head performs pre-tightening rotation motion on the bolt, the compression spring is used for ensuring proper feeding motion of the cylindrical sleeve along the positive direction of the Z axis and maintaining certain axial pressure on the bolt;
The visual assembly comprises a camera, a telecentric lens and a coaxial light source which are sequentially arranged on the fixture assembly mounting plate from top to bottom;
the bolt feeding pre-tightening system further comprises an auxiliary movement module, wherein the auxiliary movement module comprises a fixed traction block, a floating joint, an air cylinder, a magnetic switch and a throttle valve, the fixed traction block is arranged on the pre-tightening motor mounting plate below the stepping motor flange mounting plate, the floating joint is arranged between the air cylinder and the fixed traction block, and the magnetic switch and the throttle valve are arranged at the bottom of the air cylinder;
the pneumatic control unit comprises a vacuum generator and a gas filter which are arranged on the fixture assembly mounting plate, and the cylinder, the throttle valve, the floating joint, the fixed traction block and the magnetic switch are matched with the vacuum generator and the gas filter to form a pneumatic control mechanism.
2. The vision positioning-based bolt feeding pre-tightening system according to claim 1, wherein the pneumatic control mechanism further comprises an air compressor connected with the tool clamp.
3. A method for controlling a screw-feeding pre-tightening system based on visual positioning, wherein the method is applied to the screw-feeding pre-tightening system based on visual positioning according to any one of claims 1 to 2, and the method comprises the following steps:
The upper computer control system acquires a bolt hole picture shot by the vision component;
processing the bolt hole picture to obtain a coordinate value of the bolt hole center point, and sending the coordinate value of the bolt hole center point to a robot;
the robot is controlled to grasp the bolt, and the bolt is placed into the bolt hole for pre-tightening according to the coordinate value of the center point of the bolt hole;
the step of processing the bolt hole picture comprises the steps of calibrating a visual component, calibrating a robot and a hand and eye of the visual component, matching templates of the shape of the bolt hole, modeling a coordinate system of a module by taking the templates as the center, and performing secondary confirmation of the center position of the bolt hole by using a circle finding tool;
the calibration of the vision component specifically comprises the following steps:
step 1: the vision measurement system and the target are measured from two mutually perpendicular angles sequentially through the laser level meter, and simultaneously, the posture of the vision measurement system is adjusted according to the measurement result of the laser level meter, so that the camera is calibrated in the posture of the vertical target in the process of calibrating the camera, and projection distortion caused by inclination is reduced;
step 2: adjusting the photographing height of the vision measurement system to a proper position according to the effective working distance of the telecentric lens, and simultaneously adjusting the photographing angle to enable the points on the target to enter into the field of view of the camera as much as possible; the target is a checkerboard calibration plate;
Step 3: inputting the information of the checkerboard calibration plate into Vision Pro vision software, triggering a camera to shoot at the same time, and calibrating the camera by adopting a Perspotive AndRadiaWarp algorithm;
step 4: the Perspotive AndRadiiaWarp algorithm further calibrates and corrects the internal and external parameters and distortion parameters of the camera, is convenient for improving the calibration precision of the camera, obtains the mapping relation between the image coordinates and the world coordinates, and feeds back the calibration result after calibrating the telecentric lens imaging model;
calibrating a telecentric lens imaging model, specifically comprising:
assuming that the lens magnification is m here, since the external parameters of the telecentric lens lack information of parameter variation on the Z axis, the relationship between the camera coordinates and the image coordinates is:
wherein the camera coordinate system is (X c ，Y c ，Z c ) Selecting the optical axis of the camera as Z of the camera coordinate system c The (X, y) point is the (X) point in the world coordinate system w ,Y w ,Z w ) A point imaged on an imaging plane image coordinate system;
establishing an initial conversion relation between world coordinates and image coordinates of a telecentric lens, wherein an imaging model of the telecentric lens is shown in formula 2:
where (u, v, 1) is the pixel coordinates, (X) w ，Y w ，Z w ) Is the world coordinate, α and β are the axial magnification coefficients of the pixel coordinates, γ is the warping factor of the lens, and these parameters are the elements that constitute the internal parameter matrix a of the camera; r is (r) ij 、t ij Elements of rotation matrix and translation vector, K s Representing an extrinsic parameter matrix of the camera, P being a point on the world coordinate system;
the radial distortion equation of the telecentric lens is
Wherein the radial distance
Is ideal undistorted image coordinates, k 1 、k 2 … is the radial distortion coefficient;
in order to improve the calibration precision of all the internal parameters and the external parameters of the camera, nonlinear optimization processing is carried out on the obtained initial values of the parameters, and the optimization equation is as follows:
wherein x is the minimum distance between the mark point on the target and the predicted pixel coordinate, n is the number of images, m is the mark point in the image, and p ij Is the pixel coordinate of the jth marking point in the extracted ith image,
is the corresponding predicted pixel coordinates, +.>
Is the camera external parameter matrix of the ith image, P j Is the jth mark point of the target in the world coordinate system;
the accuracy of the calibration is reflected in Root Mean Square Error (RMSE), the equation is as follows:
wherein N is the number of marking points which can be identified by the camera, observed is the marking point on the target, and predicted is the corresponding predicted pixel point;
step 5: measuring the sizes of grids at all positions respectively at four corners and the center position in a calibration image by adopting a Calipero measuring tool after the camera calibration is finished;
Step 6: comparing the grid size measured at each position in the step 5 with the checkerboard calibration plate, and if the error value is larger than a preset value, indicating that the error of the calibration result is larger, and carrying out calibration again; if the error is smaller than the preset value, reserving the calibration result of the time; through the process of calibrating the camera for a plurality of times, selecting the result with the minimum calibration error as the calibration of the camera, and ending the calibration process;
the hand-eye calibration experiment steps are as follows:
step 1): installing a calibration needle on a bolt sleeve on a workpiece unit at the tail end of the robot, and establishing a tool coordinate system for a calibration seat according to a six-point method (XZ), wherein the conversion relation between the tail end of the robot and the calibration needle on the sleeve is determined;
step 2): a nine-grid calibration plate with a solid circle pattern is placed under the visual field of the camera, and the camera is triggered to shoot the calibration plate;
step 3): the circle finding tool of Vision Pro visual software is utilized to sequentially find out the pixel coordinate values of the center points of the nine solid circles, and the uncorrected X, Y columns of the CogCalibNPointToNPointTool tool of the Vision Pro visual software are filled in;
step 4): the camera is static, the robot performs hand-eye calibration in a moving mode, the robot is controlled to sequentially align the center point positions of solid circles on the calibration plate with calibration needles on the sleeve, and tool coordinate system values at the nine solid circle positions are sequentially filled into an original corrected X, Y column of the CogCalibNPointToNPointTool tool of Vision Pro vision software;
Step 5): the degrees of freedom required to be calculated are selected as "scaling, aspect ratio, rotation, tilting and translation" in the CogCalibNPointToNPointTool tool, and the calculation correction is clicked to obtain a transformation matrix of the tool coordinate system and the pixel coordinate system;
step 6): after the hand-eye calibration is completed, drawing 3 regular solid circles on different positions of the nine-grid calibration plate, and returning the camera to the original hand-eye calibration photographing position for photographing again;
step 7): the center point position of the solid circle in the step 6) is obtained by using a circle finding tool, the robot is controlled to carry the calibration aiming at the center point position of the solid circle in the step 6), the result obtained by the circle finding tool is compared with the coordinate of the robot tool coordinate system at the center point position of the solid circle, so that whether the whole calibration process meets the precision requirement or not is confirmed, and if the precision requirement is not met, the calibration is needed again.
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114917975B (en) * | 2022-05-17 | 2023-06-27 | 中国科学院沈阳自动化研究所 | Robot tail end pipetting device and robot pipetting control method |
| CN115106767A (en) * | 2022-08-01 | 2022-09-27 | 中国船舶集团有限公司第七一六研究所 | Screw fool-proof screwing system based on ultrasonic positioning |
| CN115319446A (en) * | 2022-08-15 | 2022-11-11 | 中交第一航务工程局有限公司 | Large-scale wind-powered electricity generation blade assembly fastening robot system |
| CN115431031A (en) * | 2022-09-30 | 2022-12-06 | 三一重能股份有限公司 | Stud installation system and method |
| CN115647797B (en) * | 2022-10-27 | 2024-05-14 | 一汽解放汽车有限公司 | Dismounting system for engine connecting disc |
| CN116079393A (en) * | 2023-04-10 | 2023-05-09 | 潍柴动力股份有限公司 | Bolt feeding device and bolt assembly system |
| CN117564682B (en) * | 2023-12-26 | 2024-04-26 | 北汽利戴工业技术服务(北京)有限公司 | Automatic bolt tightening system |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB639640A (en) * | 1947-04-04 | 1950-07-05 | Judson L Thomson Mfg Company | Improvements in screw driving machines |
| JPH04348828A (en) * | 1991-05-27 | 1992-12-03 | Sony Corp | Screw fastening device |
| DE202015105516U1 (en) * | 2015-10-19 | 2015-11-09 | Mijy-Land Industrial Co., Ltd. | Magnetic shuttle grappling claw for automatic screwdrivers |
| CN208483492U (en) * | 2018-07-03 | 2019-02-12 | 邯郸市美坚利五金制造有限公司 | A kind of automatically stubborn bolt mechanism |
| CN209407870U (en) * | 2018-12-28 | 2019-09-20 | 新松机器人联合研究院(湘潭)有限公司 | A kind of dual robot bolt automatic tightening system being arranged symmetrically |
| WO2020121396A1 (en) * | 2018-12-11 | 2020-06-18 | 株式会社Ｆｕｊｉ | Robot calibration system and robot calibration method |
| DE102019111049A1 (en) * | 2019-04-29 | 2020-10-29 | Weber Schraubautomaten Gmbh | System and method for the automated screwing of screw elements |
| CN112846731A (en) * | 2020-12-28 | 2021-05-28 | 上海微电机研究所(中国电子科技集团公司第二十一研究所) | Screw locking machine capable of automatically adsorbing screw combination |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09174351A (en) * | 1995-12-26 | 1997-07-08 | Nitto Seiko Co Ltd | Automatic bolt fastener |
| JP5515874B2 (en) * | 2010-03-05 | 2014-06-11 | 富士通株式会社 | Screw tightening driver, screw tightening apparatus and method |
| CN102975010B (en) * | 2011-09-06 | 2016-02-03 | 珠海格力电器股份有限公司 | A kind of pre-tappet head of plastic nut and automatic plastic nut Auto-lock Machine |
| CN107598550B (en) * | 2017-10-23 | 2024-02-09 | 朗快智能科技（杭州）有限公司 | Screw tightening device |
| CN108312144B (en) * | 2017-12-25 | 2020-10-20 | 北京航天测控技术有限公司 | Robot automatic locking control system and method based on machine vision |
| CN108296754B (en) * | 2018-01-24 | 2019-06-25 | 杭州师范大学钱江学院 | Closely locking nut Intelligent Installation system and its installation method based on machine vision |
| CN207983230U (en) * | 2018-02-08 | 2018-10-19 | 佛吉亚（中国）投资有限公司 | A kind of shared sleeve of screw bolt and nut |
| CN212947595U (en) * | 2020-08-07 | 2021-04-13 | 上汽通用五菱汽车股份有限公司 | Automatic screwing device for engine cylinder cover plug |
| CN112156992A (en) * | 2020-09-02 | 2021-01-01 | 天津博诺智创机器人技术有限公司 | Machine vision teaching innovation platform |
| CN113084808B (en) * | 2021-04-02 | 2023-09-22 | 上海智能制造功能平台有限公司 | Monocular vision-based 2D plane grabbing method for mobile mechanical arm |
-
2021
- 2021-08-23 CN CN202110968814.4A patent/CN113601158B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB639640A (en) * | 1947-04-04 | 1950-07-05 | Judson L Thomson Mfg Company | Improvements in screw driving machines |
| JPH04348828A (en) * | 1991-05-27 | 1992-12-03 | Sony Corp | Screw fastening device |
| DE202015105516U1 (en) * | 2015-10-19 | 2015-11-09 | Mijy-Land Industrial Co., Ltd. | Magnetic shuttle grappling claw for automatic screwdrivers |
| CN208483492U (en) * | 2018-07-03 | 2019-02-12 | 邯郸市美坚利五金制造有限公司 | A kind of automatically stubborn bolt mechanism |
| WO2020121396A1 (en) * | 2018-12-11 | 2020-06-18 | 株式会社Ｆｕｊｉ | Robot calibration system and robot calibration method |
| CN209407870U (en) * | 2018-12-28 | 2019-09-20 | 新松机器人联合研究院(湘潭)有限公司 | A kind of dual robot bolt automatic tightening system being arranged symmetrically |
| DE102019111049A1 (en) * | 2019-04-29 | 2020-10-29 | Weber Schraubautomaten Gmbh | System and method for the automated screwing of screw elements |
| CN112846731A (en) * | 2020-12-28 | 2021-05-28 | 上海微电机研究所(中国电子科技集团公司第二十一研究所) | Screw locking machine capable of automatically adsorbing screw combination |
Non-Patent Citations (2)
| Title |
|---|
| 半自动组合型螺丝刀结构的设计与研究;山红伟;郭伟;;科技视界(第05期);全文 * |
| 基于机器视觉的机车齿轮毂全自动双轴拧紧机的设计和应用;杨润刚;刘兵;邓连生;;起重运输机械(第06期);全文 * |
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