CN206263418U - A kind of real-time seam tracking system of six degree of freedom welding robot line laser - Google Patents

Abstract

The utility model discloses a line laser real-time seam tracking system for a six-degree-of-freedom welding robot, which includes a six-degree-of-freedom mechanical arm, a welding torch, a line laser vision sensor, a workbench, an automatic welding machine, a wire feeding mechanism, and an embedded industrial controller , control cabinet, the workpiece is placed on the workbench, the line laser vision sensor is installed on the welding torch through the installation base, the welding torch is placed at the end of the mechanical arm, the welding wire is stored in the container, and sent to the welding torch through the wire feeding device through the conduit. The wire device is fixed on the U-axis of the six-degree-of-freedom robot arm, and the container is fixed on the S-axis of the six-degree-of-freedom robot arm; the embedded industrial controller is connected with the automatic welding machine, line laser vision sensor, six-degree-of-freedom robot arm, and control cabinet signal connection. The utility model solves the problem that the distance between the laser stripe and the welding molten pool is too large in the current welding seam tracking system, and has the advantages of complete automation, high welding precision, good real-time performance, strong anti-interference ability, etc. The system structure is simple and easy to maintain.

Description

A six-degree-of-freedom welding robot line laser real-time seam tracking system

technical field

The utility model relates to a robot line laser real-time seam tracking system, in particular to a six-degree-of-freedom welding robot line laser real-time seam tracking system.

Background technique

Due to the problems of harsh working environment, high labor intensity, and low efficiency in welding operations, welding robots have been gradually applied in many fields such as automobile production, construction machinery, shipbuilding, and container production. Welding robots usually use the teaching and reproduction working mode .In order to ensure that this working mode can be implemented in a specific welding environment, the positioning of the welding workpiece needs to be completed by manual spot welding in the previous process, which will cause positioning errors and make the actual trajectory deviate from the teaching trajectory, resulting in the acquisition of teaching programming. The welding trajectory of the robot deviates from the trajectory at the time of reproduction.

With the development of machine vision technology, welding robots widely use visual inspection technology to correct and reproduce the trajectory to realize weld seam tracking. The welding seam tracking system usually installs the vision system at the end of the manipulator. When the robot is working, the vision system and the welding torch work synchronously to detect the thermal deformation of the workpiece caused by high temperature during the welding process in real time, and adjust the position between the welding torch and the weld seam.

The main technical index of the weld seam real-time tracking system is the distance d between the laser stripe 8 and the weld pool 5, as shown in Figure 4. The smaller d is, the higher the tracking accuracy is. Generally, it is expected that d<30mm, but this will cause strong arcs and spatters in the image information detected by the vision system, resulting in reduced measurement accuracy and a large amount of erroneous data. When the welding current exceeds 300A, This phenomenon is more obvious. In order to reduce the interference of arc spatter, the d of most welding seam tracking systems is about 70mm, which greatly reduces the real-time tracking and welding accuracy. Therefore, how to identify the weld seam from the image with strong noise interference and obtain its position quickly and accurately is an important issue in real-time weld seam tracking.

Utility model content

The purpose of this utility model is to overcome the deficiencies of the prior art, to provide a six-degree-of-freedom welding robot line laser real-time weld seam tracking system and method, aiming to solve the problems of visual image processing and laser stripes and welding pool in the current automatic welding technology. The problem of too much distance

The above-mentioned purpose is achieved through the following technical solutions:

A six-degree-of-freedom welding robot line laser real-time seam tracking system, including a six-degree-of-freedom mechanical arm, a welding torch, a line laser vision sensor, a workbench, an automatic welding machine, a wire feeding mechanism, an embedded industrial controller, a control cabinet, and a workpiece Placed on the workbench, the position and inclination angle of the workpiece can be adjusted manually. The line laser vision sensor is installed on the welding torch through the mounting base, and the welding torch is placed at the end of the mechanical arm. The line laser vision sensor and welding torch pass through the six-degree-of-freedom mechanical arm. Movement changes its position in space. The welding wire is stored in the container, and sent to the welding torch through the catheter through the wire feeding device. The wire feeding device is fixed on the U axis of the six-degree-of-freedom robot arm, and the container is fixed on the S of the six-degree-of-freedom robot arm. shaft; the control cabinet is respectively connected with the automatic welding machine, the six-degree-of-freedom mechanical arm, and the embedded industrial controller signal, and the embedded industrial controller is also connected with the line laser vision sensor signal, for obtaining according to the line laser vision sensor Image recognition to track the object and accurately determine its position, and transmit the obtained position deviation to the six-degree-of-freedom robotic arm to track and correct the trajectory of the welding torch in real time to achieve accurate online automatic welding.

Further, the line laser vision sensor includes a laser sensor body, a camera, a line laser generator, and a laser generator base. The camera is vertically fixed in the laser sensor body, and the line laser generator passes through the laser generator base. It is fixed in the laser sensor body and the axis forms a certain angle with the axis of the camera.

Further, the angle between the axis of the line laser generator and the axis of the camera is 20°.

Further, the camera adopts a CMOS camera, and the CMOS camera collects characteristic fringe images carrying weld seam information at high speed and transmits them to the embedded industrial controller in real time.

Further, the wire feeding mechanism is YWC-WFRPM42RD.

Further, the embedded industrial controller is Advantech IPC-510, and the control cabinet is JZRCR-YTB21-F380.

Further, the automatic welding machine is MOTOWELD-RD350.

Further, the six-degree-of-freedom mechanical arm is composed of six axes, the S-axis is connected to the robot platform, the T-axis is equipped with a welding torch, and a servo motor is installed between the axes to allow mutual rotation.

Compared with the prior art, the utility model has the following advantages:

(1) The feature points of the weld seam are detected by the line laser vision sensor with high precision. The embedded industrial controller processes the welding seam image, controls the wire feeding and welding device and the servo drive, and the system structure is simple and easy to maintain;

(2) The coordinate value of the center point of the weld can be extracted in an environment containing a large amount of arc light and spatter, with high precision and strong anti-interference ability, and the distance between the laser stripe and the welding pool is reduced to within 30mm, which enhances weld seam tracking real-time.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of a six-degree-of-freedom welding robot line laser real-time seam tracking system according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of the degree of freedom of the mechanical arm in the real-time weld seam tracking system of the six-degree-of-freedom welding robot line laser in the embodiment of the present invention;

Fig. 3 is a schematic diagram of installation of a six-degree-of-freedom mechanical arm, a welding torch, and a line laser vision sensor according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of the distance between the laser stripe and the weld pool in the weld seam tracking system according to the embodiment of the present invention.

Fig. 5 is an overall working flow chart of the real-time welding seam tracking method of the six-degree-of-freedom welding robot line laser according to the embodiment of the present invention.

Fig. 6 is a flow chart of the feature point detection algorithm in the real-time seam tracking method of the six-degree-of-freedom welding robot line laser according to the embodiment of the present invention.

As shown in the figure: 1-six degrees of freedom mechanical arm; 2-welding torch; 3-line laser vision sensor; 4-mounting base; 5-welding pool; 6-camera; 7-line laser generator; 8-laser stripe ; 9-workpiece; 10-embedded industrial controller; 11-control cabinet; 12-automatic welding machine; 13-workbench; 14-Beckhoff module.

detailed description

The purpose of the utility model is further described in detail through specific examples below, and the examples cannot be repeated here one by one, but the implementation of the utility model is not therefore limited to the following examples.

Example

As shown in Figures 1 to 3, a six-degree-of-freedom welding robot line laser real-time seam tracking system includes a six-degree-of-freedom mechanical arm 1, a welding torch 2, a line laser vision sensor 3, a workbench 13, an automatic welding machine 12, Wire feeding mechanism, embedded industrial controller 10, Beckhoff module 14, control cabinet 11, the workpiece 9 is placed on the workbench, the position and inclination angle of the workpiece 9 can be adjusted manually, and the line laser vision sensor 3 passes through the installation base 4 Installed on the welding torch 2, the welding torch 2 is placed at the end of the mechanical arm. The line laser vision sensor 3 and the welding torch change their positions in space through the movement of the six-degree-of-freedom mechanical arm 1. The welding wire is stored in the container and passed through the catheter. The device is sent to the welding gun 2, the wire feeding device is fixed on the U-axis of the six-degree-of-freedom mechanical arm 1, and the container is fixed on the S-axis of the six-degree-of-freedom mechanical arm 1; Robotic arm 1, embedded industrial controller 10 signal connection, wherein control cabinet 11 and embedded industrial controller 10 are connected through Beckhoff module 14; Said embedded industrial controller 10 is also connected with line laser vision sensor 3 through Ethernet The signal connection is used to identify and track the object and accurately determine its position according to the image acquired by the line laser vision sensor, and transmit the obtained position deviation to the six-degree-of-freedom mechanical arm to track and correct the trajectory of the welding torch in real time to achieve accurate online automatic welding .

The line laser vision sensor 2 includes a laser sensor body, a camera 6, a line laser generator 7, and a laser generator base, and the camera is vertically fixed in the laser sensor body, and the line laser generator 7 passes through the laser generator. The base is fixed in the laser sensor body and the axis forms a certain angle with the axis of the camera 6 .

The angle between the axis of the line laser generator 7 and the axis of the camera is 20°.

The camera 6 adopts a CMOS camera, and the CMOS camera collects characteristic fringe images carrying weld seam information at high speed and transmits them to the embedded industrial controller 10 in real time.

The wire feeding mechanism is YWC-WFRPM42RD.

The embedded industrial controller 10 is Advantech IPC-510, and the control cabinet 11 is JZRCR-YTB21-F380.

The automatic welding machine 12 is MOTOWELD-RD350.

The six-degree-of-freedom mechanical arm 1 is composed of six axes, the S-axis is connected with the robot frame, the T-axis is equipped with a welding torch, and a servo motor is installed between the axes to allow mutual rotation.

As shown in Figure 5, the tracking method of the six-degree-of-freedom welding robot line laser real-time seam tracking system provided by this embodiment includes steps:

(1) During welding, the image collected by the camera 6 in the line laser vision sensor 3 is first subjected to image preprocessing;

(2) Using a feature point extraction algorithm based on weighted cosine similarity (WLCS), obtain the pixel coordinate value of the weld center feature point in the preprocessed current frame image;

(3) After the coordinate values are converted into three-dimensional coordinate values in the camera coordinate system, the deviation values (Δx, Δy, Δz) between the values and the initial values are sent to the six-degree-of-freedom robot in real time through the Beckhoff module 14, thereby Drive the welding torch to complete the automatic welding process.

Specifically, before step (1), steps are also included:

According to the image collected by the camera in the line laser vision sensor, the initial weld feature points and adjacent areas before welding are obtained.

Specifically, the step of obtaining the initial weld feature points and adjacent areas before welding according to the image collected by the camera in the line laser vision sensor specifically includes:

(1) Adjust the position of the mechanical arm of the six-degree-of-freedom welding robot so that the end of the welding torch (that is, the end of the welding wire) is located directly above the weld seam of the workpiece to be welded, and the line laser vision sensor fixed on the welding torch is in the best working position, That is to say, a clear image can be captured during the welding process without interference between the line laser vision sensor and the workpiece to be welded;

(2) The camera in the line laser vision sensor collects images and sends them to the embedded industrial controller. The embedded industrial controller initializes by calling the library function of the Halcon software to obtain the initial weld feature points and adjacent areas;

(3) The embedded industrial controller converts the pixel coordinate values of the initial feature points before welding into three-dimensional coordinate values based on the camera coordinate system.

Specifically, as shown in Figure 6, described step (1) specifically includes:

(11) The camera of the laser vision sensor continuously collects each frame of image during welding, and sends it to the embedded industrial controller for processing and calculation;

(12) The embedded industrial controller performs preprocessing on the obtained image to reduce spatter and arc noise in the welding image, so that the purity of the image becomes higher. The preprocessing includes threshold processing, binarization and three Image multiplication processing.

Specifically, the step (2) specifically includes:

(21) Initialize the tracker, the embedded industrial controller initializes by calling the library function of the Halcon software, and obtains the initial weld seam feature points and adjacent areas;

(22) Use the motion model p(x _t |x _t-1 ) to collect a large number of target candidate states in the image, x _t represents the state variable of the target object, and the subscript t is the current image frame number;

(23) Use the measurement model p(y _t |x _t ) to evaluate the candidate state variables, and find the observation vector with the highest similarity with the candidate state variables, y _t is the observation vector corresponding to x _t , and the observation model here uses weighted cosine similarity (WLCS) measurement;

(4) By applying the particle filter method under the Fourier framework, the best candidate state position is calculated as the actual position coordinates of the weld feature points in the image. The calculation method is:

p(x _t |y _1:t-1 )＝∫p(x _t |x _t-1 )p(x _t-1 |y _1:t-1 )dx _t-1

p(x _t |y _1:t )＝p(y _t |x _t )p(x _t |y _1:t-1 )/p(y _t |x _t )p(x _t |y _{1:t- 1} )

In the formula, y _1:t represents all observation vectors from time 1 to time t, and the first formula is a prediction formula, which predicts the state variable x at time t through the observation vector y _1:t-1 from time 1 to time t-1 _t ; the second formula is an update formula, and the observation vector y _t at time t is added to the first formula to correct the state variable x _t .

Specifically, the Weighted Cosine Similarity (WLCS) measurement method of the step (23) is specifically:

(231) Calculate the cosine similarity:

In the formula, y is the observation vector, t is the target module, the subscript j is the jth sub-region vector, and w is the weight of the corresponding sub-region vector;

(232) Enter the online update after calculating the cosine similarity, including the update of the weight and the target module; the module update formula is:

where ε is a preset threshold, and η is the update rate;

(233) After completing the update of the target module t, collect the positive and negative samples of the image module, and update the weights by solving the following optimization problem:

in Ω ⁺ and Ω ^- represent positive and negative samples of weld feature points respectively, and w' is equal to the weight value at the previous moment, that is, w'=w _t-1 .

Specifically, the step (3) specifically includes:

(31) Convert the pixel coordinate value of the weld center feature point in the obtained image into the three-dimensional coordinate value under the camera coordinate system and compare it with the three-dimensional coordinate value of the current welding torch position to obtain the deviation value (Δx, Δy, Δz);

(32) The embedded industrial controller sends the deviation value (Δx, Δy, Δz) to the servo driver in real time through the Beckhoff module 14, and the servo driver drives the servo motor and drives the six-degree-of-freedom mechanical arm to move, so that the end of the welding torch The welding wire moves along the midpoint of the weld seam of the workpiece to complete the real-time seam tracking process of the six-degree-of-freedom robot.

The optional parts of the parts described in this embodiment are as follows, but the selection is not limited to this: Embedded industrial controller: Advantech IPC-510, other embedded industrial controllers of the same type can be used; workpiece: angle steel, optional Other regular shaped workpieces of the same type.

The above-mentioned embodiments of the present utility model are only examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the utility model shall be included in the protection scope of the claims of the utility model.

Claims (8)

1. A line laser real-time seam tracking system for a six-degree-of-freedom welding robot, characterized in that it includes a six-degree-of-freedom mechanical arm, a welding torch, a line laser vision sensor, a workbench, an automatic welding machine, a wire feeding mechanism, and an embedded industrial control The workpiece is placed on the workbench, and the position and inclination angle of the workpiece can be adjusted manually. The line laser vision sensor is installed on the welding torch through the installation base, and the welding torch is placed at the end of the mechanical arm. The line laser vision sensor and welding torch pass through The movement of the six-degree-of-freedom mechanical arm changes its position in space. The welding wire is stored in the container, passed through the catheter, and sent to the welding torch through the wire feeding device. The S axis of the mechanical arm of the degree of freedom; the control cabinet is respectively connected with the automatic welding machine, the six-degree-of-freedom mechanical arm, and the embedded industrial controller signal, and the embedded industrial controller is also connected with the line laser vision sensor signal for According to the image acquired by the line laser vision sensor, the tracking object is recognized and its position is accurately determined, and the obtained position deviation is transmitted to the six-degree-of-freedom mechanical arm, which tracks and corrects the trajectory of the welding torch in real time to achieve accurate online automatic welding. 2. The line laser real-time seam tracking system of a six-degree-of-freedom welding robot according to claim 1, wherein the line laser visual sensor includes a laser sensor body, a camera, a line laser generator, and a laser generator base, and The above camera is vertically fixed in the laser sensor body, the line laser generator is fixed in the laser sensor body through the base of the laser generator and the axis forms a certain angle with the axis of the camera. 3. The line laser real-time seam tracking system of a six-degree-of-freedom welding robot according to claim 2, wherein the angle between the axis of the line laser generator and the axis of the camera is 20 ^° . 4. The six-degree-of-freedom welding robot line laser real-time weld seam tracking system according to claim 2, characterized in that: the camera adopts a CMOS camera, and the CMOS camera collects the characteristic fringe image carrying weld seam information at a high speed and Real-time transmission to embedded industrial controllers. 5. The six-degree-of-freedom welding robot line laser real-time seam tracking system according to claim 1, characterized in that: the wire feeding mechanism is YWC-WFRPM42RD. 6. The six-degree-of-freedom welding robot line laser real-time seam tracking system according to claim 1, characterized in that: the embedded industrial controller is Advantech IPC-510, and the control cabinet is JZRCR-YTB21-F380. 7. The six-degree-of-freedom welding robot line laser real-time seam tracking system according to claim 1, characterized in that: the automatic welding machine is MOTOWELD-RD350. 8. The six-degree-of-freedom welding robot line laser real-time weld seam tracking system according to claim 1, characterized in that: the six-degree-of-freedom mechanical arm is composed of six axes, the S axis is connected to the robot stand, and the T axis is additionally installed Welding torch, with servo motors installed between the shafts, allowing mutual rotation.