CN112605499A

CN112605499A - Visual sensing device for tracking narrow-gap welding seam of thick plate and using method

Info

Publication number: CN112605499A
Application number: CN202011505648.6A
Authority: CN
Inventors: 王克鸿; 钱凌雨
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2020-12-18
Filing date: 2020-12-18
Publication date: 2021-04-06
Anticipated expiration: 2040-12-18
Also published as: CN112605499B

Abstract

The invention discloses a visual sensing device for tracking a narrow gap welding seam of a thick plate and a using method. The device comprises a sensor shell, a CMOS high-speed camera is arranged in the rectangular shell, and the front of the camera is connected with an improved telecentric lens; the left side and the right side in the rectangle are provided with two line lasers by using clamps, and the two line lasers are positioned at the top end of the sensor; the laser passes through the circuit and links to each other with the circuit board, and the scintillation of line laser ware triggers the realization through PLC, has respectively installed the speculum under the laser ware, and the speculum passes through sensor shell surface angle scale freedom angle of adjustment, is fixed with the prism simultaneously in sensor inside. The invention is convenient for groove observation and later image contrast calculation, and the sensor can effectively and precisely track the narrow gap groove weld of the large and thick plate with the thickness of more than 40 mm.

Description

Visual sensing device for tracking narrow-gap welding seam of thick plate and using method

Technical Field

The invention belongs to the field of weld joint tracking optical sensors, and particularly relates to a visual sensing device for tracking a narrow gap weld joint of a thick plate and a using method thereof.

Background

The principle of the optical sensor for tracking the welding seam at present is mainly based on the optical distance measuring principle, and the main components of the optical sensor generally comprise a CCD or CMOS photosensitive device, a chip set circuit, an optical lens, an optical path structure, a linear, multi-linear or anisotropic semiconductor laser, image acquisition processing software and a control circuit. The working principle of the sensor is that the linear semiconductor laser emits laser in the present situation, the linear laser is projected to the surface of an object to be detected, and the laser generates diffuse reflection on the surface of the object to be irradiated; the CCD or CMOS photosensitive device is arranged at a certain proper position above the detected object projected with the linear laser at a certain angle, so that the photosensitive device can capture light and the detected object. An optical lens element including a lens, an optical filter, a dimmer and the like is reasonably arranged in front of the photosensitive device in a certain light path design and used for focusing, filtering, size adjustment and the like of a captured image, the diffuse reflection of the linear laser on the surface of the detected object is captured by the photosensitive device through the optical lens in an image mode, and the image is the surface contour of the detected object. When the linear laser passes by the surface of the detected object, the surface contour of the detected object changes along with the linear laser due to thermal deformation, mechanical deviation and the like in the welding process, and contour parameters and deviation information of the welding seam can be obtained through image acquisition and algorithm processing.

At present, a welding seam tracking optical sensor is usually placed at a position with a height of about 40mm-100mm above a detected welding seam, the depth of a groove of the welding seam is required to be not more than 40mm, and if the welding seam is too deep, the bottom of the groove of the welding seam cannot be tracked because the reflection of projected linear laser at the bottom of the groove exceeds the acquisition range of a photosensitive device. At present, when narrow gap welding of thick plates and ultra-thick plates is carried out, a manual observation and manual adjustment mode and an electric arc tracking and automatic adjustment mode are generally adopted, and the two welding seam tracking and adjusting methods have problems in actual construction, such as incapability of guaranteeing higher tracking precision and reliability. At present, for narrow gap welding seam tracking in the three-dimensional direction, because detected objects are not on the same plane, an optical magnifier is generally used for adjusting the magnification, but the problem of inconsistent magnification effect on the same image due to the change of object distance exists. Therefore, an effective high-precision tracking method and equipment for the narrow-gap groove weld of the large thick plate of more than 40mm are lacked at present.

Disclosure of Invention

The invention aims to provide a narrow gap welding seam tracking laser sensor capable of performing deviation rectification control on a narrow gap groove welding seam of a large thick plate with the thickness of more than 40 mm.

The technical solution for realizing the purpose of the invention is as follows: a visual sensing device for thick plate narrow gap welding seam tracking comprises a CMOS high-speed camera, a telecentric lens, a linear laser, a reflector, a prism, a sensor shell and a PLC (programmable logic controller);

a CMOS high-speed camera is arranged at the top of one side in the sensor shell, and a telecentric lens is arranged right below the CMOS high-speed camera; the sensor comprises a sensor shell, a PLC controller and two linear lasers, wherein the two linear lasers are arranged in parallel at the top of the other side in the sensor shell, a reflective mirror is arranged under each linear laser, a triangular prism is arranged under each reflective mirror, and the PLC controller is connected with the linear lasers and used for alternately exciting the linear lasers at high frequency.

Furthermore, the sensor shell is integrally rectangular, and the wall thickness of the sensor shell is 0.8-1.2 CM.

Furthermore, a light barrier is arranged at the left lower side of the sensor shell close to one end of the narrow-gap welding gun.

Furthermore, a circular camera shooting window is arranged at the bottom of the lower portion of the sensor shell, the camera shooting window is matched with the position of the telecentric lens, and the diameter of the camera shooting window is equal to that of the telecentric lens.

Furthermore, the length of the telecentric lens is longer than that of the CMOS high-speed camera, and the diameter of the telecentric lens is smaller than that of the CMOS high-speed camera.

Furthermore, the angle of the reflector is continuously adjustable, and the light path is adjustable by adjusting the angle of the reflector.

Furthermore, an angle scale disc matched with the reflector is arranged on the outer side of the sensor shell, and the angle scale disc can display the angle of the reflector.

Further, the PLC controller is connected with the linear laser through a trigger circuit.

The use method of the device comprises the following steps:

step (1): linear lasers on two sides in the sensor shell are triggered through a trigger circuit of the PLC, and the linear lasers on the two sides flicker alternately at high frequency;

step (2): the alternately-flashing line laser is optically reflected by a reflector right below the line laser, the angle dial is adjusted to enable the double-line laser to irradiate a triangular prism inside the sensor at a certain incident angle, the reflected line laser is refracted on the triangular prism, firstly, an image obtained by the CMOS high-speed camera is observed on a PC (personal computer), and the light refraction angle is ensured to be within the visible range of the CMOS high-speed camera and the image is visible; then further adjusting the angle of a reflector of the angle dial to enable the double-beam laser to accurately irradiate the two side walls of the groove respectively, and forming an image of the shape of the bottom of the single groove side wall plus the half groove on the PC;

and (3): transmitting the image into a CMOS high-speed camera photosensitive unit through a telecentric lens; the image is preprocessed and post-processed, and the processing result is uploaded to the control unit through a line in a digital signal mode for subsequent processing.

Further, the step (1) is specifically as follows: adjusting the frequency of PLC trigger and the frequency of CMOS high-speed camera trigger signals, wherein the CMOS high-speed camera trigger signals are formed from a digital port, the signals start to be kept at a high level, meanwhile, the time duration of a shutter is opened for t1, and the time duration of t2 is kept by automatic reverse rotation of a software program when exposure is finished; in the initial state, the shutter of the CMOS high-speed camera 1 is not opened, and the time duration of t2 is maintained; the PLC circuit is initially in an enabled state, and the trigger frequency of the PLC circuit ensures that line laser flicker is alternated every time length of t2+ t ', wherein t' is alternation time delay which is far shorter than the blanking time of two frames of images.

Compared with the prior art, the invention has the remarkable advantages that:

(1) the improved telecentric lens is different from the lens used in the traditional method, the aperture of the lens is narrow, and only highly collimated light rays are allowed to enter, so that most of noise light is eliminated, and meanwhile, the design of the arc baffle plate further reduces the interference of arc noise and the like; the lens distortion rate is extremely low, and the requirement of high-precision tracking of narrow-gap groove weld joints is met; the improved telecentric lens has an optical amplification function, the image amplification rate of the telecentric lens is not light with the distance or position of an object in a view field, the low distortion and high definition image acquisition of the profiles of the two side walls and the bottom of the narrow gap groove weld of the thick plate can be realized, and the problem of less effective information of the original narrow gap weld tracking image of the thick plate is solved to a certain extent; the improved telecentric lens window design can ensure that the telecentric lens window is rigidly and vertically fixed, thereby ensuring the image acquisition stability in the welding process;

(2) two line lasers are fixed at the top of the inner side wall of the sensor, so that the distance between the line lasers and a welding line is maximized, overheating damage is avoided, and the service life of the lasers is prolonged; the dual lasers are vertically fixed and are respectively provided with a reflector under the dual lasers, so that the line laser is irradiated in an inclined way, the volume of the whole sensor is reduced on one hand, and the structure is optimized; on the other hand, the laser incidence range is expanded, the incidence angle is continuously adjustable at 0-90 degrees through the angle scale disc, the angle scale disc is arranged on the surface of the sensor shell, the angle adjustment can be carried out externally, the problem that the laser is difficult to adjust after the angle is changed in the traditional design is solved, and the laser has simplicity and accuracy; the prism fixed in the sensor plays a role in light path refraction, so that the double-beam laser can accurately irradiate the inner side wall of the narrow and deep groove;

(3) triggering the laser to flicker through a PLC triggering device, wherein the flicker is carried out at high frequency, and the frequency can be freely regulated and controlled by software; the groove side wall double images simultaneously acquired by the method can effectively utilize the characteristics of CPU multi-core of a PC and GPU CUDA programming, provide conditions for a multithread image processing mode, have higher processing efficiency, and can meet the requirement of welding tracking instantaneity of the narrow-gap groove weld.

Drawings

Fig. 1 is a three-dimensional schematic view of a sensor device of the present invention.

Fig. 2 is a front view of the sensor device of the present invention.

Description of reference numerals:

the sensor comprises a 1-CMOS high-speed camera, a 2-telecentric lens, a 3-linear laser, a 4-reflector, a 5-angle scale, a 6-prism, a 7-light barrier and an 8-sensor shell.

Detailed Description

The present invention is described in further detail below with reference to the attached drawing figures.

As shown in fig. 1-2, the narrow gap weld tracking laser sensor of the present invention comprises: the device comprises a rectangular sensor shell 8, a fixing device, a linear laser 3, a reflector 4, a prism 6, an angle dial 5, a circular shooting window, an improved telecentric lens 2, a CMOS high-speed camera 1, a PLC trigger device and a communication line joint;

the cross section of the rectangular sensor shell is rectangular, and the CMOS sensor, the improved telecentric lens, the PLC trigger device and other components are all tightly fixed in the rectangular sensor; the linear laser is fixed on two sides of the inner side wall of the rectangular sensor and is aligned with the top of the shell, a reflector is respectively arranged right below the linear laser, and the angle of the reflector can be continuously adjusted within the range of 0-90 degrees by an angle scale; the angle engraving plate consists of two clamping pieces and two engraving plates, wherein one end of each clamping piece is punched and fixed with the sensor shell, the other end of each clamping piece is fixedly bonded with the reflector, and the clamping pieces are connected and fixed in a bolt manner; the two engraving plates are provided with 'bullet-shaped' buckles at equal angular intervals, and the fixed incident angle is formed by shifting or moving the reflector back and forth and fixing the reflector on a certain buckle; a hollow window is arranged on the sensor shell at the position of the angle scale, and angle adjustment can be directly operated outside the sensor.

The irradiated line laser is reflected by a reflector and enters a prism to be refracted, and accurately enters the inner side wall of the groove, and the whole irradiation range of the light is within the capture range of a CMOS high-speed camera; the improved telecentric lens is connected with the CMOS high-speed camera and is vertically and rigidly fixed through a circular shooting window. Line laser irradiated by a linear laser triggered by a PLC high frequency is projected on outline images of the bottom and the side wall of a narrow-gap groove weld joint, passes through a circular camera shooting window, is subjected to optical amplification by a preposed improved telecentric lens and certain noise light filtration, and enters a CMOS sensor unit; at the moment, the collected clear optically amplified double-side outline images are subjected to image multithreading efficient preprocessing and post-processing, so that various parameters of the side wall and the bottom of the groove can be obtained in real time, and the narrow-gap groove welding seam can be tracked by matching with a welding gun.

The thickness of the thick plate part below the rectangular sensor shell 8 is more than or equal to 20mm, wherein, the two side walls inside the sensor are fixed with linear lasers 3, the height of the linear lasers 3 is equal to the top, the linear laser irradiated by the linear lasers 3 firstly passes through a reflector 4, the angle of the reflector 4 is directly adjusted outside the sensor through an angle dial, the linear laser is reflected to the upper surface of a prism 6 in the sensor at a certain incident angle, the prism 6 has a light path refraction function, two laser beams are accurately irradiated to the two side walls of a narrow and deep groove, and the formed linear laser band with a welding line penetrates through the round window below the rectangular sensor shell 8 to enter the sensor shell.

The linear laser 3 is triggered by a PLC trigger circuit, and the linear laser 3 on the two side walls in the sensor flickers and irradiates at high frequency.

The groove side wall and the bottom linear laser band are almost simultaneously acquired and captured by a CMOS high-speed camera 1, and comprise images of the groove left side wall, the groove bottom, the groove right side wall and the groove bottom, and an improved telecentric lens 2 is adopted before; the improved telecentric lens 2 only allows the collimated light to enter because of small aperture, and filters most of noise light by itself, and can reduce the difficulty of post image processing and make the image clearer by matching with the action of the light barrier 7.

The improved telecentric lens 2 is different from the common lens used by most of the existing welding seam tracking, and the image distortion rate is extremely low, so that the high-precision tracking requirement of a narrow gap is very consistent; the improved telecentric lens 2 has an optical amplification function, and the amplification effect and the position of an object in a view field are not light. For the narrow gap groove of the thick plate, especially the thick plate with the thickness of more than 40mm, the problems of precision loss caused by different amplification effects, less effective image information caused by narrow and deep bottom and double side walls and the like are effectively avoided.

When the narrow gap welding seam bottom and the double-side-wall outline image formed by the linear laser band are projected onto the CMOS high-speed camera 1 through the improved telecentric lens 2, the internal sensing circuit of the CMOS high-speed camera 1 performs primary processing on the image, and transmits the processing result to the image acquisition control unit through a line in a digital signal mode for subsequent processing.

The working process of the patent sensor of the invention is as follows:

linear lasers 3 on two sides in the rectangular sensor shell 8 are triggered through a PLC trigger circuit, and the linear lasers 3 on the two sides flicker alternately at high frequency; adjusting the frequency of PLC trigger and the frequency of CMOS high-speed camera 1 trigger signals, wherein the CMOS high-speed camera 1 trigger signals are formed from a digital port, the signals start to be kept at a high level, meanwhile, a shutter is opened for t1 time duration, and the signals are automatically reversed through a software program to keep t2 time duration when exposure is finished; in the initial state, the shutter of the CMOS high-speed camera 1 is not opened, and the time duration of t2 is maintained; the PLC circuit is initially in an enabled state, and the trigger frequency of the PLC circuit ensures that line laser flicker is alternated every time length of t2+ t ', wherein t' is alternation time delay which is far shorter than the blanking time of two frames of images.

The alternately-flashing line laser is optically reflected by a reflector 4 right below the line laser, an angle dial 5 is adjusted to enable the double-line laser to irradiate a triangular prism inside the sensor at a certain incident angle, and the reflected line laser is refracted on the triangular prism. Firstly, observing an image acquired by the CMOS high-speed camera 1 on a PC (personal computer), and ensuring that the light refraction angle is within the visible range of the CMOS high-speed camera 1 and the image is visible; and then further adjusting the angle of a reflector of the angle dial to enable the double-beam laser to accurately irradiate the two side walls of the groove respectively, and forming an image of the shape of the bottom of the single groove side wall plus the half groove on the PC, thereby indicating that the adjustment is successful. Through the noise light removing effect and the optical amplification effect brought by the small aperture of the improved telecentric lens 2, the image can be transmitted into the photosensitive unit of the CMOS high-speed camera 1 finally; the image is preprocessed and post-processed, and the processing result is uploaded to the control unit through a line in a digital signal mode for subsequent processing.

When narrow gap groove weld joint tracking is carried out, a narrow gap welding gun is arranged behind a narrow gap welding joint tracking laser sensor 8, the height distance between the bottom of the sensor 8 and the bevel face is kept to be 30-35 mm, and parameters of the bottom of the groove and the two side walls, such as transverse offset, height offset and the like, obtained by the narrow gap welding joint tracking laser sensor can be used for adjusting the position of the welding gun to finish the welding joint tracking process.

According to the technical scheme provided by the invention, the narrow gap welding seam tracking laser sensor provided by the embodiment of the invention only allows high-precision collimated light to enter due to the improved telecentric lens, so that the interference of arc light and the like in the welding process is effectively filtered, and the high depth of field can still have excellent definition when an object with thickness is observed; for three-dimensional direction weld joint tracking, the image magnification can not change along with the change of the object distance within a certain object distance range; the sensor is internally provided with a bilateral line laser, a PLC circuit is utilized to trigger high frequency, laser reflection is realized through a reflector, the reflection angle is continuously adjustable, and finally, through the refraction effect of an internal prism, double-beam laser irradiates on the two side walls of a groove, the narrow and deep groove is subjected to more comprehensive and clear reflection and contrast of the left side wall and the right side wall, and the high-precision tracking can be carried out on the side wall profile of the narrow gap groove weld of a large thick plate above 40mm, especially on the side wall of the narrow gap groove weld.

Claims

1. A visual sensing device for tracking a thick plate narrow gap welding seam is characterized by comprising a CMOS high-speed camera (1), a telecentric lens (2), a linear laser (3), a reflector (4), a prism (6), a sensor shell (8) and a PLC (programmable logic controller);

the top of one side in the sensor shell (8) is provided with a CMOS high-speed camera (1), and a telecentric lens (2) is arranged right below the CMOS high-speed camera (1); the sensor is characterized in that two linear lasers (3) arranged in parallel are arranged at the top of the other side in the sensor shell (8), a reflective mirror (4) is arranged under each linear laser (3), a triangular prism (6) is arranged under each reflective mirror (4), and the PLC is connected with the linear lasers (3) and used for alternately exciting the linear lasers (3) at high frequency.

2. The device according to claim 1, characterized in that the sensor housing (8) is rectangular overall, the sensor housing wall thickness being 0.8-1.2 CM.

3. The device according to claim 2, characterized in that the sensor housing near one end of the narrow gap welding gun is provided with a light barrier (7) on the left lower side.

4. A device according to claim 3, characterized in that the sensor housing (8) is provided with a circular camera window at the lower bottom, which camera window matches the position of the telecentric lens (2) and has a diameter equal to the diameter of the telecentric lens (2).

5. The apparatus of claim 4, wherein the telecentric lens has a length greater than that of the CMOS high speed camera and a diameter less than that of the CMOS high speed camera.

6. A device according to claim 5, characterized in that the angle of the mirror (4) is continuously adjustable, and that the adjustment of the light path is achieved by adjusting the angle of the mirror.

7. The device according to claim 6, characterized in that the outside of the sensor housing (8) is provided with an angle scale (5) which cooperates with the mirror (4), and the angle scale (5) is capable of displaying the angle of the mirror.

8. The arrangement according to claim 7, characterized in that the PLC controller is connected to the linear laser (3) via a triggering circuit.

9. A method of using the apparatus of claim 8, comprising the steps of:

step (1): the linear lasers (3) on the two sides in the sensor shell (8) are triggered through a trigger circuit of the PLC, and the linear lasers (3) on the two sides flicker alternately at high frequency;

step (2): the line laser which alternately flickers is optically reflected by a reflector (4) right below the line laser, an angle dial (5) is adjusted to enable the double-line laser to irradiate a triangular prism (6) in the sensor at a certain incident angle, the reflected line laser is refracted on the triangular prism, firstly, an image obtained by the CMOS high-speed camera (1) is observed on a PC (personal computer), and the light refraction angle is ensured to be within the visual range of the CMOS high-speed camera (1) and the image is visible; then further adjusting the angle of a reflector of the angle dial to enable the double-beam laser to accurately irradiate the two side walls of the groove respectively, and forming an image of the shape of the bottom of the single groove side wall plus the half groove on the PC;

10. The method according to claim 9, characterized in that step (1) is in particular: adjusting the frequency of PLC trigger and the frequency of a CMOS high-speed camera (1) trigger signal, wherein the CMOS high-speed camera (1) trigger signal is formed from a digital port, the signal is kept at a high level for t1 duration while a shutter is opened, and the signal is automatically reversed by a software program for t2 duration when exposure is finished; in the initial state, the shutter of the CMOS high-speed camera 1 is not opened, and the time duration of t2 is maintained; the PLC circuit is initially in an enabled state, and the trigger frequency of the PLC circuit ensures that line laser flicker is alternated every time length of t2+ t ', wherein t' is alternation time delay which is far shorter than the blanking time of two frames of images.