Welding robot and control method thereof

Abstract

The invention relates to the technical field of welding robots, in particular to a welding robot and a control method thereof. The welding robot comprises a moving assembly and a welding assembly. The welding assembly comprises a rack, a crank, a rotating rod, a connecting rod and a welding gun. The rack is rotationally installed at the free end of the telescopic frame. One end of the crank is hinged to a first hinge shaft on the rack, and a first rotating shaft is arranged at the other end of the crank; one end of the rotating rod is hinged to a second hinge shaft on the rack, and a second rotating shaft is arranged at the other end of the rotating rod; the other end of the connecting rod is hinged with the second rotating shaft; the welding gun is mounted in the middle of the connecting rod; the distance from the first hinge shaft to the first rotating shaft is equal to the distance from the second hinge shaft to the second rotating shaft, and the crank and the rotating rod are opposite in rotating direction. Through the constraint effect of the rack, the crank, the rotating rod and the connecting rod, the welding gun can swing in an 8-shaped track, and the welding technique of a welder is simulated by combining the movement of the welding gun in the length direction of a joint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding robots, in particular to a welding robot and a control method thereof. BACKGROUND

[0002] With the wide application of large metal structural parts in the fields of ships, engineering machinery, steel structures and pressure vessels, the size of workpieces is increasing, especially in the welding connection of flat plate workpieces, there are a large number of long straight or slowly changing curved welding seams, and these welding seams usually have large seam depth and groove angle, which puts higher requirements on welding quality and consistency.

[0003] At present, manual welding is generally used for the welding connection of such thick plate workpieces, which relies on the rich experience of welders to control the welding gun posture and swing trajectory (such as "floating handle", "folding handle", "shaking handle" and other methods) to realize the regulation of the molten pool, so as to ensure the weld forming quality. However, manual welding has the problems of high labor intensity, welding quality depending on the experience of welders, poor consistency of each workpiece weld quality, etc., which is difficult to meet the needs of large-scale production.

[0004] In order to improve the level of welding automation, various welding robots or automatic welding equipment are proposed in the prior art. Among them, the multi-joint welding robot (such as the mobile intelligent welding robot and welding method disclosed in Chinese patent document CN202310496433.X) realizes the motion control of the welding gun in space through a multi-degree-of-freedom mechanical arm, which can accurately reach the welding seam position and realize the welding operation along the preset path. However, its structure is complex, the cost is high, and it depends on the control system and trajectory planning, which is easily limited by the working radius, singular configuration and installation position in the large-size workpiece or workshop operating environment, and it is difficult to realize the welding method in manual welding, so the weld quality is difficult to guarantee.

[0005] In addition, although the track type or gantry type welding equipment can cover a larger welding area, its welding gun motion form is usually linear or simple swing, and fixed parameters are usually used in the welding process, which is difficult to adapt to the welding requirements of the change of the filling layer width during the layer-by-layer filling in the thick plate welding process, resulting in problems such as incomplete fusion, uneven filling or poor weld forming in thick workpiece filling welding.

[0006] Therefore, there is an urgent need for a welding robot with simplified structure and large coverage range, which is used for layer-by-layer welding filling of the welding seam with large depth and groove angle, and can change the molten pool coverage width accordingly to form a high-quality weld. SUMMARY

[0007] The application aims to provide a welding robot and a control method thereof, which is used for replacing manual work to perform high repetitive welding operation in thick plate welding scene, and is convenient for batch welding production of workpieces. The welding robot has simple structure and low difficulty in welding operation, and can perform layer-by-layer welding filling based on a welding strategy formulated according to the characteristics of a seam to be welded, and change the width of a molten pool correspondingly to form a high-quality weld.

[0008] The first aspect of the application provides a welding robot, which comprises a moving assembly and a welding assembly; the moving assembly comprises a sliding rail, a cross frame and an extension frame; the sliding rail is fixedly arranged along a first direction; the cross frame is arranged along a second direction and is in sliding connection with the sliding rail, and the relative sliding direction of the two is parallel to the first direction; the extension frame is vertically arranged and has a fixed end in sliding connection with the cross frame, and the relative sliding direction of the two is parallel to the second direction; the welding assembly comprises a frame, a crank, a rotating rod, a connecting rod and a welding torch; the frame is rotatably installed on a free end of the extension frame; one end of the crank is hingedly connected to a first hinge shaft on the frame, and a first rotating shaft is arranged on the other end of the crank; one end of the rotating rod is hingedly connected to a second hinge shaft on the frame, and a second rotating shaft is arranged on the other end of the rotating rod; one end of the connecting rod is hingedly connected to the first rotating shaft, and the other end is hingedly connected to the second rotating shaft; the welding torch is installed in the middle of the connecting rod; the distance from the first hinge shaft to the first rotating shaft is equal to the distance from the second hinge shaft to the second rotating shaft, and the rotating directions of the crank and the rotating rod are opposite, so that when the crank continuously rotates, the tungsten tip of the welding torch moves in an 8-shaped trajectory; the axis of rotation of the frame relative to the free end is defined as a baseline, the baseline is vertical, and when the welding torch is located at the midpoint of the connecting rod, the intersection point of the 8-shaped trajectory is located on the baseline.

[0009] Therefore, the welding assembly can be freely moved along the first direction, the second direction and the height direction by the moving assembly, and the three-direction movement is independently controlled, so that the control process is simplified and automation is facilitated; the welding torch can swing in an 8-shaped trajectory by the constraint action of the four-bar mechanism composed of the frame, the crank, the rotating rod and the connecting rod, and then combined with the movement of the welding torch along the length direction of the seam, the welding method of a welder can be simulated to form a weld covering the width direction of the seam, and the connection quality of the weld is high.

[0010] However, for thick plate welding connection of a deep seam, a groove is usually opened, so that the seam has a cross-sectional shape with a narrow bottom and a wide upper part, and the single swing amplitude of the welding torch is difficult to adapt to the seam width at different welding depth positions.

[0011] Further, the first rotating shaft is slidingly connected with the crank, and the relative sliding direction is parallel to the length direction of the crank. A first telescopic unit is installed on the crank, and the first telescopic unit is used to push the first rotating shaft to slide. The second rotating shaft is slidingly connected with the rotating lever, and the relative sliding direction is parallel to the length direction of the rotating lever. A second telescopic unit is installed on the rotating lever, and the second telescopic unit is used to push the second rotating shaft to slide.

[0012] Therefore, by sliding the first rotating shaft along the length direction of the crank and sliding the second rotating shaft along the length direction of the rotating lever, the constraint length of the crank and the constraint length of the connecting rod (i.e. the effective length actually playing a constraint role in the four-bar mechanism) in the four-bar mechanism can be changed, and the length size of the 8-shaped trajectory of the welding gun swinging can be changed. Therefore, the 8-shaped trajectory of the welding gun swinging can be adapted to different widths of the joint, so that the situation of the joint being too wide or too narrow in the welding operation can be avoided.

[0013] However, for the joint to be welded which is curved or bent (with an angle), the amount of molten metal required on the outside and the inside of the joint is obviously different in the angle section. Therefore, the welding robot is obviously not suitable for welding the angle section.

[0014] Further, the welding gun is slidingly connected with the connecting rod, and the relative sliding direction is parallel to the length direction of the connecting rod. A third telescopic unit is installed on the connecting rod, and the third telescopic unit is used to push the welding gun to slide. The distance between the axis of the welding gun and the midpoint of the connecting rod is less than half of the distance between the first hinged shaft and the first rotating shaft.

[0015] Further, the welding gun is obliquely arranged, and the axis of the welding gun forms an angle of 10° to 20° with the baseline.

[0016] Further, a counterweight is installed on the rotating lever, and the center of gravity of the counterweight has an eccentricity with the second hinged shaft.

[0017] Further, a first motor is fixedly installed on the slide rail, a first screw rod is rotatably installed on the slide rail, the cross frame is threadedly connected with the first screw rod, and the first motor is used to drive the first screw rod to rotate. A second motor is fixedly installed on the cross frame, a second screw rod is rotatably installed on the cross frame, the fixed end is threadedly connected with the second screw rod, and the second motor is used to drive the second screw rod to rotate. A third motor is fixedly installed on the fixed end, a third screw rod is rotatably installed on the fixed end, the free end is threadedly connected with the third screw rod, and the third motor is used to drive the third screw rod to rotate.

[0018] Further, a first driving motor is fixedly installed on the free end, and the first driving motor is used to drive the frame to rotate.

[0019] The second aspect of the present application provides a control method for controlling the welding robot to weld two workpieces to be welded, the control method comprising: S1, acquiring joint information of the two workpieces to be welded, the joint information comprising a joint trajectory; S2, controlling the mobile assembly to drive the welding assembly to move, so that the tungsten tip is located at a preset depth position of the joint, and a projection of the base line in the vertical direction is located on the joint trajectory; S3, controlling the mobile assembly to drive the welding assembly to move, so that the projection of the base line in the vertical direction moves along the joint trajectory and the welding gun performs welding.

[0020] Further, the control of the mobile assembly to drive the welding assembly to move comprises: controlling the cross frame to slide in a first direction and controlling the telescopic frame to slide in a second direction, so that the free end translates in the horizontal direction; controlling the telescopic frame to extend or retract in the vertical direction, so that the free end translates in the vertical direction.

[0021] Further, the S3 comprises: in the case of welding the bottom of the joint, locking the crank when controlling the welding gun to perform welding; in the case of welding the upper part of the joint, controlling the crank to continuously rotate when controlling the welding gun to perform welding, so that the welding gun swings in the joint width direction while moving in the joint length direction.

[0022] Further, the joint information further comprises a joint depth, a groove angle and a root gap; in the case of welding the upper part of the joint, according to the joint depth, the groove angle, the root gap and the depth of the welding position, controlling the first rotating shaft to slide in the length direction of the crank and controlling the second rotating shaft to slide in the length direction of the rotating lever, so that the amplitude of the swing of the welding gun in the joint width direction is adapted to the joint width of the welding position.

[0023] Further, for a V-shaped groove, after controlling the first rotating shaft to slide in the length direction of the crank, the distance from the first hinged shaft to the first rotating shaft, and after controlling the second rotating shaft to slide in the length direction of the rotating lever, the distance from the second hinged shaft to the second rotating shaft are obtained according to the following manner: wherein, L 1 represents the distance from the first hinged shaft to the first rotating shaft after controlling the first rotating shaft to slide in the length direction of the crank, L 2indicates the distance from the second articulated shaft to the second rotating shaft after the second rotating shaft is controlled to slide along the length direction of the rotating rod, H indicates the joint depth, h indicates the depth of the welding position, θ indicates the bevel angle, d indicates the root gap.

[0024] Further, the S3 comprises: S31, pre-welding, a plurality of pre-welding points are determined along the joint length direction, the moving assembly is controlled to move the welding assembly to each pre-welding point and perform spot welding; the spot welding sequence is: from the middle to both ends of the joint length direction, each pre-welding point is alternately performed; S32, sectional welding, any two adjacent pre-welding points are identified as a to-be-welded section, the moving assembly is controlled to move the welding assembly from the middle to both ends of the joint length direction, each to-be-welded section is alternately performed.

[0025] Further, in the case of welding connection on the upper part of the joint, for the corner section of the joint, when the welding gun is controlled to perform welding, the rack is controlled to rotate around the base line, so that the plane where the first articulated shaft and the second articulated shaft are located coincides with the normal line of the corner section joint trajectory.

[0026] Further, in the case of welding connection on the upper part of the joint, for the corner section of the joint, when the welding gun is controlled to perform welding, the welding gun is controlled to slide along the length direction of the connecting rod towards the outside of the corner by a preset distance, and the projection of the base line in the vertical direction is controlled to slide along the normal line of the corner section joint trajectory towards the inside of the corner by a preset distance.

[0027] Compared with the prior art, the present application has the following advantages and beneficial effects: 1、The welding robot and the control method thereof provided by the embodiment of the present application, by driving the crank to continuously rotate while the welding assembly moves along the joint trajectory, the welding gun installed in the middle of the connecting rod is forced to continuously move along an 8-shaped trajectory under the constraint of the four-bar mechanism composed of the rack, the crank, the rotating rod and the connecting rod; and the rack is adjusted to rotate around the base line until the plane where the first articulated shaft and the second articulated shaft are located is perpendicular to the joint, so that the 8-shaped trajectory "crosses" the joint, and then while the welding gun moves along the length direction of the joint, the welding gun also swings along the normal line of the joint, so that the welding pool spreads in the width direction of the joint, which is beneficial to increase the coverage width of the weld, strengthen the fusion connection between the weld and the bevel surface, and improve the connection quality and appearance quality of the weld; 2. The welding robot and the control method thereof provided by the embodiment of the present application can adjust the constraint length of the crank and the constraint length of the rotating rod in the four-bar mechanism by slidingly connecting the first rotating shaft with the crank and slidingly connecting the second rotating shaft with the rotating rod, and further, the welding robot provided by the embodiment of the present application can change the length of the 8-shaped trajectory by changing the constraint length of the crank and the constraint length of the rotating rod in the four-bar mechanism, so that the width of the welding pool spreading in the width direction of the seam can be changed when the welding torch also swings along the normal of the seam, and the width of the welding pool spreading in the width direction of the seam can be adapted to the width of the seam when the welding torch swings along the normal of the seam, thereby avoiding incomplete welding or overflow in the width direction of the seam. 3. The welding robot and the control method thereof provided by the embodiment of the present application can adjust the distance from the welding torch to the first rotating shaft and the second rotating shaft by slidingly connecting the welding torch with the connecting rod, and further, the shape of the 8-shaped trajectory can be changed by changing the distance from the welding torch to the first rotating shaft and the second rotating shaft, so that one end of the 8-shaped trajectory is larger and the other end is smaller, and further, when facing a curved seam trajectory, the large end of the 8-shaped trajectory can be located outside the corner and the small end can be located inside the corner by sliding the welding torch along the length direction of the connecting rod in the corner section, thereby ensuring that the inside and outside of the corner section are well filled by the welding pool. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present application and constitute a part of the application, illustrate embodiments of the present application and do not limit the present application. In the drawings: Figure 1 It is a perspective structural schematic view of the welding robot drawn according to the embodiment of the present application; Figure 2 It is a perspective structural schematic view of the welding assembly drawn according to the embodiment of the present application; Figure 1 It is a partial enlarged view of the A area drawn according to the embodiment of the present application; Figure 3 It is a perspective structural schematic view of the welding assembly drawn according to the embodiment of the present application; Figure 4 It is one of the mechanism motion sketches of the welding assembly drawn according to the embodiment of the present application; Figure 5 It is the second of the mechanism motion sketches of the welding assembly drawn according to the embodiment of the present application; Figure 6 It is the third of the mechanism motion sketches of the welding assembly drawn according to the embodiment of the present application; Figure 7 It is a comparison schematic view of the mechanism motion sketches of the welding assembly drawn according to the embodiment of the present application, in which the length of the crank is changed; Figure 8 It is a comparison schematic view of the mechanism motion sketches of the welding assembly drawn according to the embodiment of the present application, in which the position of the welding torch is changed.

[0029] Markings in the drawings and corresponding component names: 11 - slide rail; 111 - first motor; 112 - first screw rod; 12 - cross frame; 121 - second motor; 122 - second screw rod; 13 - telescopic frame; 131 - fixed end; 132 - free end; 133 - third motor; 134 - third screw rod; 135 - first driving motor; 21 - frame; 211 - first hinged shaft; 212 - second hinged shaft; 213 - second driving motor; 22 - crank; 221 - first rotating shaft; 222 - first telescopic unit; 23 - rotating rod; 231 - second rotating shaft; 232 - second telescopic unit; 24 - connecting rod; 241 - third telescopic unit; 25 - welding gun. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present application clearer, further detailed description will be given below in combination with examples and drawings. The illustrative embodiments of the present application and their descriptions are only used to explain the present application and do not limit the present application. It should be noted that the present application has been in the actual research and development stage.

[0031] Welding connection is an important connection method for fixed connection of mechanical components. In order to improve the processing efficiency, welding robot equipment has been introduced in large quantities in the production process to replace simple and repetitive work content. However, for deep welding seams, welding robots are difficult to replicate the operation method of welders to fill the seams. Even if the welding robot is used for multi-pass welding along the length direction of the seam, the welding quality of the seam is still low (mainly the combination between the passes is not tight enough). Therefore, such welding seams still mainly rely on manual welding by welders.

[0032] Therefore, the present application provides a welding robot and a control method thereof, which is used for replacing welders to perform high repetitive welding operation in the thick plate welding scene, and is convenient for batch welding production of such workpieces. The welding robot can imitate the welding method of welders to push the molten pool horizontally (i.e., pushing the molten pool in the normal direction of the seam at the welding position) when welding a wide seam, so that the molten pool covers the entire seam during single-layer welding, forming an integrated welding layer, and thus the welding quality approaches manual welding by welders.

[0033] Example 1 As shown in Figures 1 to 3 the present embodiment provides a welding robot, which comprises a moving assembly and a welding assembly; The moving assembly comprises a slide rail 11, a cross frame 12 and a telescopic frame 13. The slide rail 11 is fixedly arranged along a first direction; the cross frame 12 is arranged along a second direction and is in sliding connection with the slide rail 11, and the relative sliding direction of the two is parallel to the first direction; the telescopic frame 13 is vertically arranged and a fixed end 131 thereof is in sliding connection with the cross frame 12, and the relative sliding direction of the two is parallel to the second direction; The welding assembly comprises a frame 21, a crank 22, a rotating rod 23, a connecting rod 24 and a welding torch 25; The frame 21 is rotatably mounted on a free end 132 of the telescopic frame 13; one end of the crank 22 is hingedly connected to a first hinge shaft 211 on the frame 21, and a first rotating shaft 221 is arranged on the other end of the crank 22; one end of the rotating rod 23 is hingedly connected to a second hinge shaft 212 on the frame 21, and a second rotating shaft 231 is arranged on the other end of the rotating rod 23; one end of the connecting rod 24 is hingedly connected to the first rotating shaft 221, and the other end thereof is hingedly connected to the second rotating shaft 231; the welding torch 25 is mounted on the middle part of the connecting rod 24; The distance from the first hinge shaft 211 to the first rotating shaft 221 is equal to the distance from the second hinge shaft 212 to the second rotating shaft 231, and the rotating directions of the crank 22 and the rotating rod 23 are opposite, so that when the crank 22 continuously rotates, the tungsten electrode tip of the welding torch 25 moves along an 8-shaped trajectory; The axis of rotation of the frame 21 relative to the free end 132 is defined as a baseline, the baseline is vertical, and when the welding torch 25 is located at the midpoint of the connecting rod 24, the intersection point of the 8-shaped trajectory is located on the baseline.

[0034] Accordingly, after the welding assembly is driven by the moving assembly to reach the specified position, the welding assembly is driven by the moving assembly to move along the seam trajectory of the two workpieces to be welded, so that the seam can be welded; in particular, while the welding assembly moves along the seam trajectory, the crank 22 is continuously rotated (in this embodiment, a second driving motor 213 is mounted on the frame 21, and the second driving motor 213 is used to drive the crank 22 to continuously rotate), so that under the constraint of the four-bar mechanism composed of the frame 21, the crank 22, the rotating rod 23 and the connecting rod 24, the welding torch 25 mounted on the middle part of the connecting rod 24 continuously moves along an 8-shaped trajectory (see Figure 4 、 Figure 5 ); obviously, at this time, the frame 21 is rotated around the baseline to a plane in which the first hinge shaft 211 and the second hinge shaft 212 are located is perpendicular to the seam, so that the 8-shaped trajectory "crosses" the seam, and accordingly, while the welding torch 25 moves along the length direction of the seam, the welding torch 25 also swings along the normal line of the seam, so that the welding pool can spread in the width direction of the seam, which is beneficial to increase the coverage width of the weld, strengthen the fusion connection between the weld and the bevel surface, improve the connection quality and appearance quality of the weld, and is particularly suitable for the welding connection of wide seams.

[0035] Obviously, the welding robot provided in this embodiment is particularly suitable for continuous welding operations, and correspondingly, it is particularly suitable for welding operations based on argon arc welding.

[0036] Specifically, such as Figure 1 As shown, a first motor 111 is fixedly installed on the slide rail 11, and a first screw 112 is rotatably installed on the slide rail 11. The cross frame 12 is threadedly connected to the first screw 112, and the first motor 111 is used to drive the first screw 112 to rotate. A second motor 121 is fixedly installed on the span frame 12, and a second screw 122 is rotatably installed on the span frame 12. The fixed end 131 is threadedly connected to the second screw 122, and the second motor 121 is used to drive the second screw 122 to rotate. A third motor 133 is fixedly installed on the fixed end 131, and a third screw 134 is rotatably installed on the fixed end 131. The free end 132 is threadedly connected to the third screw 134, and the third motor 133 is used to drive the third screw 134 to rotate.

[0037] Accordingly, the welding robot provided in this embodiment utilizes screw transmission, enabling the first motor 111 to achieve the sliding motion of the span 12 along a first direction, the second motor 121 to achieve the sliding motion of the telescopic frame 13 along a second direction, and the third motor 133 to achieve the telescopic movement of the telescopic frame 13. It can reliably position and suppress vibration based on the self-locking characteristics of the threaded connection, and ensures high precision in the sliding motion of the span 12 and the telescopic frame 13, as well as the telescopic movement of the telescopic frame 13. For the welding scenario of this application, the high-precision telescopic movement and reliable self-locking positioning of the telescopic frame 13 enable the welding assembly to reliably reach and maintain a preset height position; the high-precision sliding of the span 12 and the telescopic frame 13 ensures that the welding assembly moves along a preset trajectory.

[0038] Preferably, such as Figure 3 As shown, the welding torch 25 is inclined, and the axis of the welding torch 25 forms an angle of 10° to 20° with the baseline.

[0039] Accordingly, the tilted welding torch 25 can reduce molten pool overflow or spatter; help push the molten pool metal to the weld edge and enhance weld toe filling; and effectively guide the shielding gas to the molten pool surface, etc.

[0040] Preferably, a counterweight is fixedly installed on the rotating rod 23, and the center of gravity of the counterweight is eccentric to the second hinge shaft 212.

[0041] Accordingly, in the process of continuous rotation of the crank 22, the moment of inertia of the rotating rod 23 can be increased by setting the counterweight (not shown in the figure), thereby ensuring that it passes through the dead point position (i.e. the position where the crank 22 and the rotating rod 23 are collinear) smoothly and still rotates in the opposite direction of the crank 22 after passing through the dead point. It should be understood that when the crank 22 is controlled to stop, it should be avoided to stop at the position where the rotating rod 23 is at the dead point, and if it is stopped at the dead point, the rotating rod 23 should be manually adjusted to pass through the dead point before starting the crank 22 to continue rotating.

[0042] Preferably, as shown in Figure 2 、 Figure 3 , a first driving motor 135 is fixedly installed on the free end 132, and the first driving motor 135 is used to drive the frame 21 to rotate; the first driving motor 135 is a servo motor or a stepping motor.

[0043] Accordingly, the first driving motor 135 can reliably determine the angle of driving the frame 21 to rotate relative to the free end 132, and for the case where the crank 22 does not rotate, it can ensure that the direction in which the welding gun 25 blows the molten pool coincides with the advancing direction of the welding gun 25; for the case where the crank 22 rotates, it can ensure that the length direction of the 8-shaped trajectory of the welding gun 25 when it swings at any position in the length direction of the joint coincides with the normal direction of the joint at that position. Figure 4

[0044] Embodiment 2: As shown in Figure 2 、 Figure 3 , this embodiment is based on embodiment 1, and the difference is that in this embodiment: the first rotating shaft 221 is slidingly connected with the crank 22, and the relative sliding direction of the two is parallel to the length direction of the crank 22, a first telescopic unit 222 is installed on the crank 22, and the first telescopic unit 222 is used to push the first rotating shaft 221 to slide; the second rotating shaft 231 is slidingly connected with the rotating rod 23, and the relative sliding direction of the two is parallel to the length direction of the rotating rod 23, a second telescopic unit 232 is installed on the rotating rod 23, and the second telescopic unit 232 is used to push the second rotating shaft 231 to slide.

[0045] ​It should be understood that the first telescopic unit 222 and the second telescopic unit 232 can be mature products from the existing technology. For example, in this embodiment, a screw drive is used. Taking the crank 22 as an example, an adjusting screw is rotatably installed on the crank 22, and a thread is made on the first rotating shaft 221 so that the first rotating shaft 221 and the adjusting screw are threadedly connected. Then, by rotating the adjusting screw, the first rotating shaft 221 can be pushed to slide along the length direction of the crank 22. Obviously, linear motors and other electrical control devices can also be used, which will not be elaborated here.

[0046] Accordingly, the welding robot provided in this embodiment, by slidingly connecting the first rotating shaft 221 to the crank 22 and the second rotating shaft 231 to the rotating rod 23, enables the adjustment of the constraint length of the crank 22 (i.e., the distance from the first rotating shaft 221 to the first hinge shaft 211) and the constraint length of the rotating rod 23 (i.e., the distance from the second rotating shaft 231 to the second hinge shaft 212) in the four-bar linkage; furthermore, the welding robot provided in this embodiment can change the length of the figure-eight trajectory (i.e., the distance of the figure-eight trajectory in the four-bar linkage) by changing the constraint lengths of the crank 22 and the rotating rod 23 in the four-bar linkage. Figure 4 The dimensions of the line connecting the first hinge axis 211 and the second hinge axis 212 can correspondingly change the width of the figure-eight trajectory covering the joint. Accordingly, when the welding torch 25 oscillates along the normal to the joint, the width of the weld pool spreading in the width direction of the joint can be changed. Obviously, the width is smaller for the lower part of the joint and larger for the upper part. In this embodiment, by changing the length of the figure-eight trajectory, the width of the weld pool spreading in the width direction of the joint can be adapted to the width of the joint when the welding torch 25 oscillates along the normal to the joint, thereby avoiding incomplete welding or overflow in the width direction of the joint.

[0047] In response, Figure 7 A comparative schematic diagram of the motion of the welding assembly mechanism when the length of crank 22 changes is drawn, where figure a (corresponding to) Figure 5 ) and map b (corresponding to Figure 4 The difference between the links in the diagram is that the length of crank 22 in diagram a is greater than the length of crank 22 in diagram b, and the length of rotating rod 23 in diagram a is greater than the length of rotating rod 23 in diagram b (that is, corresponding to the aforementioned sliding of the first rotating shaft 221 and the corresponding sliding of the second rotating shaft 231, which increases the constraint length of crank 22 and the constraint length of rotating rod 23). Correspondingly, the length of the figure-eight trajectory formed by the movement of the midpoint of connecting rod 24 in diagram a is greater than the length of the figure-eight trajectory formed by the movement of the midpoint of connecting rod 24 in diagram b.

[0048] Example 3: like Figure 2 , Figure 3 As shown, this embodiment is based on embodiment 1, the difference being that in this embodiment: The welding gun 25 is slidingly connected with the connecting rod 24, and the direction of relative sliding of the two is parallel to the length direction of the connecting rod 24. A third telescopic unit 241 is installed on the connecting rod 24, and the third telescopic unit 241 is used to push the welding gun 25 to slide. The distance between the axis of the welding gun 25 and the midpoint of the connecting rod 24 is less than half of the distance between the first hinge shaft 211 and the first rotating shaft 221.

[0049] It should be understood that the third telescopic unit 241 can be a mature product in the prior art. In this embodiment, in combination with the fact that the welding gun 25 may need to be adjusted to slide along the connecting rod 24 during welding, a linear motor is used as the third telescopic mechanism, and the linear motor is used to push the welding gun 25 to slide along the length direction of the connecting rod 24.

[0050] Accordingly, the welding robot provided in this embodiment can adjust the distance between the welding gun 25 and the first rotating shaft 221 and the second rotating shaft 231 by slidingly connecting the welding gun 25 with the connecting rod 24. Furthermore, the welding robot provided in this embodiment can change the shape of the 8-shaped trajectory (see Figure 6 by changing the distance between the welding gun 25 and the first rotating shaft 221 and the second rotating shaft 231, and changing the sizes of the arc-shaped trajectories at both ends of the length direction of the 8-shaped trajectory, so that one end is larger and the other end is smaller. Accordingly, when facing a curved joint trajectory, the welding robot provided in this embodiment can change the shape of the 8-shaped trajectory by sliding the welding gun 25 along the length direction of the connecting rod 24, so that the large end of the 8-shaped trajectory is located outside the corner, and the small end is located inside the corner, thereby ensuring that the inside and outside of the corner section are both well filled with the molten pool.

[0051] For this purpose, Figure 8 a comparison schematic diagram of the mechanism movement of the welding assembly when the welding gun 25 deviates from the midpoint of the connecting rod 24 after moving along the length direction of the connecting rod 24 is drawn, wherein the length of each rod in the b drawing (corresponding to Figure 4 ) is equal to the length of each rod in the c drawing (corresponding to Figure 6 ). The difference is that in the b drawing, the welding gun 25 is located at the midpoint of the connecting rod 24, and in the c drawing, the welding gun 25 slides towards the second rotating shaft 231 and deviates from the midpoint. Correspondingly, the sizes of the arc-shaped trajectories at both ends of the length direction of the 8-shaped trajectory presented by the movement of the welding gun 25 in the b drawing are equal, while the sizes of the arc-shaped trajectories at both ends of the length direction of the 8-shaped trajectory presented by the movement of the welding gun 25 in the c drawing are unequal, and the right end is larger than the left end. The lengths of the 8-shaped trajectories presented by the movement of the welding gun 25 are equal.

[0052] Embodiment 4: The control method provided in this embodiment is used to control the welding robot to perform welding connection on two workpieces to be connected, and the control method comprises: S1, acquiring seam information of two workpieces to be welded, the seam information comprising a seam trajectory; S2, controlling the movement assembly to move the welding assembly so that the tungsten tip is located at a preset depth position of the seam, and a projection of the base line in the vertical direction is located on the seam trajectory; S3, controlling the movement assembly to move the welding assembly so that the projection of the base line in the vertical direction moves along the seam trajectory and controlling the welding gun 25 to perform welding.

[0053] Accordingly, the control method provided by the embodiment can control the welding robot to continuously perform welding operation along the length direction of the seam, and complete the welding connection work of the two workpieces to be welded.

[0054] Specifically, the control of the movement assembly to move the welding assembly comprises: controlling the cross frame 12 to slide in a first direction and controlling the telescopic frame 13 to slide in a second direction, so that the free end 132 translates in a horizontal direction; controlling the telescopic frame 13 to extend or retract in a vertical direction, so that the free end 132 translates in a vertical direction.

[0055] By controlling the cross frame 12 to slide in the first direction and controlling the telescopic frame 13 to slide in the second direction, the movement trajectory of the projection of the base line in the vertical direction can be controlled, and the movement of the welding assembly along the seam trajectory is realized.

[0056] Preferably, the S3 comprises: in the case of welding connection at the bottom of the seam, locking the crank 22 when controlling the welding gun 25 to perform welding; in the case of welding connection at the upper part of the seam, controlling the crank 22 to continuously rotate when controlling the welding gun 25 to perform welding, so that the welding gun 25 swings in the width direction of the seam while moving in the length direction of the seam.

[0057] Accordingly, the control method provided in the embodiment is adapted to the actual situation that the bottom of the joint is narrow by locking the crank 22 when welding the joint bottom, and the joint is welded by advancing along the joint; for the upper part of the joint, the tungsten tip is made to swing in an 8-shaped trajectory along the width direction of the joint while moving along the joint trajectory by controlling the crank 22 to continuously rotate, thereby covering the joint in the width direction under the actual situation that the upper part of the joint is wide, so that the welding connection of the large deep joint can be completed in the form of multi-layer welding, and the welding strategy of multi-layer multi-pass welding (the “layer” of the multi-layer multi-pass welding is formed by splicing a plurality of welding passes in the width direction, and the interface defects are prone to occur between the plurality of welding passes in the welding layer) is avoided, and the integrity of the welding layer is good.

[0058] It should be understood that when the crank 22 is locked, the tungsten tip of the welding gun 25 should be located on the baseline, so that the tungsten tip moves along the joint trajectory when the projection of the control baseline in the vertical direction moves along the joint trajectory, thereby performing the welding by advancing along the joint. In fact, the tungsten tip of the welding gun 25 can also deviate from the baseline, but at this time, a correction amount needs to be introduced when the projection of the control baseline in the vertical direction moves along the joint trajectory, to compensate for the deviation between the tungsten tip and the baseline, so that the tungsten tip always moves along the joint trajectory, thereby avoiding the welding deviation, which makes the sliding of the welding control cross frame 12 in the first direction and the sliding of the telescopic frame 13 in the second direction more troublesome.

[0059] Preferably, the S3 further comprises: S31, pre-welding, determining a plurality of pre-welding points along the length direction of the joint (for example, the pre-welding points are sequentially numbered as P1, P2, P3, P4 and P5 along the length direction of the joint), and controlling the moving assembly to move the welding assembly to each pre-welding point and perform spot welding; The spot welding is sequentially performed from the middle to both ends of the joint length direction by alternately welding each pre-welding point (correspondingly, the spot welding sequence is P3-P2-P4-P1-P5); S32, sectional welding, regarding the section between any two adjacent pre-welding points as a to-be-welded section (correspondingly, the to-be-welded sections are sequentially numbered as S 12 , S 23 , S 34 , S 45 along the length direction of the joint), and controlling the moving assembly to move the welding assembly from the middle to both ends of the joint length direction by alternately welding each to-be-welded section (correspondingly, the welding sequence of each to-be-welded section is S 23 -S 34 -S 12 -S 45 ).

[0060] Accordingly, for the welding work of long seams, the positioning work in the early stage can be realized through pre-connection, and the release of welding stress can be guided through segmented welding, thereby avoiding the deformation of the workpiece caused by stress concentration under long seam continuous welding.

[0061] Embodiment 5: This embodiment is based on Embodiment 4, and the difference is that in this embodiment: The joint information further includes a joint depth, a groove angle, and a root gap; In the case of welding connection to the upper part of the joint, according to the joint depth, the groove angle, the root gap, and the depth of the welding position, the first rotating shaft 221 is controlled to slide along the length direction of the crank 22 and the second rotating shaft 231 is controlled to slide along the length direction of the rotating rod 23, so that the amplitude of the welding gun 25 swinging along the joint width direction is adapted to the joint width of the welding position.

[0062] Accordingly, the control method provided in this embodiment knows the joint width of the welding position through the joint information, and then controls the first rotating shaft 221 to slide along the length direction of the crank 22 and controls the second rotating shaft 231 to slide along the length direction of the rotating rod 23, so as to change the crank 22 constraint length and the rotating rod 23 constraint length in the four-bar mechanism composed of the rack 21, the crank 22, the rotating rod 23, and the connecting rod 24 (it should be noted that the two are always equal), and then make the length of the 8-shaped trajectory formed by the tungsten tip swinging under the new four-bar mechanism constraint adapt to the joint width of the welding position, thereby avoiding the situation that the welding layer formed in the welding at different welding depths is not full or overflowed in the width direction.

[0063] Specifically, for a V-shaped groove, after controlling the first rotating shaft 221 to slide along the length direction of the crank 22, the distance from the first hinged shaft 211 to the first rotating shaft 221, and after controlling the second rotating shaft 231 to slide along the length direction of the rotating rod 23, the distance from the second hinged shaft 212 to the second rotating shaft 231 is obtained according to the following manner: , wherein, L 1 represents the distance from the first hinged shaft to the first rotating shaft after controlling the first rotating shaft to slide along the length direction of the crank, L 2 represents the distance from the second hinged shaft to the second rotating shaft after controlling the second rotating shaft to slide along the length direction of the rotating rod, H represents the joint depth, h represents the depth of the welding position, θ represents the groove angle, d represents the root gap.

[0064] Accordingly, the control method provided by the embodiment can obtain the required crank 22 constraint length and the swing rod 23 constraint length based on the depth of the welding position, the joint depth, the groove angle and the root gap, and then control the first rotating shaft 221 and the second rotating shaft 231 to slide according to the crank 22 constraint length and the swing rod 23 constraint length, so as to accurately control the sliding distance of the first rotating shaft 221 and the second rotating shaft 231 and greatly reduce the adjustment work in the process of controlling the first rotating shaft 221 and the second rotating shaft 231 to slide to the appropriate position.

[0065] Embodiment 6: The embodiment is based on Embodiment 4, and the difference is that, in the embodiment: In the case of welding connection on the upper part of the joint, for the corner section of the joint, the machine frame 21 is controlled to rotate around the base line when the welding gun 25 is controlled to perform welding, so that the plane where the first and second articulated shafts 211 and 212 are located coincides with the normal line of the corner section joint track (for example, if the current welding position is a point P on the corner section joint track, the plane where the first and second articulated shafts 211 and 212 are located should coincide with the normal line of the position where the point P is located on the joint track at this time).

[0066] Accordingly, the control method provided by the embodiment can change the length direction of the 8-shaped track when the welding gun 25 swings by controlling the machine frame 21 to rotate around the base line at the corner section of the joint, so that the length direction of the 8-shaped track always coincides with the normal direction of the joint track at the welding position, which is beneficial to the coverage of the welding corner section in the width direction of the joint.

[0067] Specifically, in the case of welding connection on the upper part of the joint, for the corner section of the joint, when the welding gun 25 is controlled to perform welding, the welding gun 25 is controlled to slide a preset distance along the length direction of the connecting rod 24 towards the outside of the corner, and the projection of the base line in the vertical direction is controlled to slide a preset distance along the normal line of the corner section joint track towards the inside of the corner.

[0068] Obviously, during the welding process, the first and second articulated shafts 211 and 212 are respectively located on both sides of the joint track, and controlling the welding gun 25 to slide a preset distance along the length direction of the connecting rod 24 towards the outside of the corner is actually controlling the welding gun 25 to slide along the length direction of the connecting rod 24, and the sliding direction is towards the articulated shaft outside the corner section joint track (if the first articulated shaft 211 is located outside the joint track, the welding gun 25 slides towards the first rotating shaft 221, and if the second articulated shaft 212 is located outside the joint track, the welding gun 25 slides towards the second rotating shaft 231).

[0069] Accordingly, the control method provided in the embodiment changes the shape of the 8-shaped trajectory of the swing of the welding torch 25 by controlling the welding torch 25 to slide along the length direction of the connecting rod 24 at the corner section of the joint, so that the larger end of the 8-shaped trajectory is located outside the corner section and the smaller end is located inside the corner section, thereby pushing the molten pool to be distributed more outside the corner section and less inside the corner section, so as to adapt to the difference in the amount of molten metal required outside and inside the corner section, and avoid the situation that the corner section outside is not full and / or the corner section inside is overflowed. In addition, the control method also controls the projection of the baseline in the vertical direction to slide along the normal of the joint trajectory at the corner section to the inside of the corner, so as to correct the offset of the 8-shaped trajectory of the swing of the welding torch 25 caused by the sliding of the welding torch 25, and ensure that the position covered by the swing of the welding torch 25 in the width direction of the joint is adapted to the position of the joint.

[0070] In the present application, the term "joint trajectory" refers to the center line of the joint.

[0071] In the present application, the term "rotary mounting" and "hinged" means that only relative rotation can occur between the two, such as the rotary arrangement of the hole and the shaft rod, which can be achieved by setting a shaft shoulder on the shaft and a limiting groove in the hole to limit the relative movement in the axial direction; the term "sliding connection" means that only relative sliding can occur between the two, such as dovetail groove, T-shaped groove and the like.

[0072] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A welding robot, characterized by: The welding robot comprises a moving assembly and a welding assembly; The moving assembly comprises a slide rail (11), a cross frame (12) and an extension frame (13); The slide rail (11) is fixedly arranged along a first direction; the cross frame (12) is arranged along a second direction and is in sliding connection with the slide rail (11), and the relative sliding direction of the two is parallel to the first direction; the extension frame (13) is vertically arranged, and a fixed end (131) thereof is in sliding connection with the cross frame (12), and the relative sliding direction of the two is parallel to the second direction; The welding assembly comprises a frame (21), a crank (22), a rotating rod (23), a connecting rod (24) and a welding torch (25); The frame (21) is rotatably arranged on a free end (132) of the extension frame (13); one end of the crank (22) is hingedly connected to a first hinge shaft (211) on the frame (21), and a first rotating shaft (221) is arranged on the other end of the crank (22); one end of the rotating rod (23) is hingedly connected to a second hinge shaft (212) on the frame (21), and a second rotating shaft (231) is arranged on the other end of the rotating rod (23); one end of the connecting rod (24) is hingedly connected to the first rotating shaft (221), and the other end thereof is hingedly connected to the second rotating shaft (231); and the welding torch (25) is arranged on the middle part of the connecting rod (24); The distance from the first hinge shaft (211) to the first rotating shaft (221) is equal to the distance from the second hinge shaft (212) to the second rotating shaft (231), and the rotating directions of the crank (22) and the rotating rod (23) are opposite, so that when the crank (22) continuously rotates, the tungsten tip of the welding torch (25) moves along an 8-shaped trajectory; The axis of rotation of the frame (21) relative to the free end (132) is defined as a baseline, the baseline is vertical, and when the welding torch (25) is located at the midpoint of the connecting rod (24), the intersection point of the 8-shaped trajectory is located on the baseline.

2. The welding robot according to claim 1, wherein: The first rotating shaft (221) is in sliding connection with the crank (22), and the relative sliding direction of the two is parallel to the length direction of the crank (22); a first extension unit (222) is arranged on the crank (22), and the first extension unit (222) is used for pushing the first rotating shaft (221) to slide; The second rotating shaft (231) is in sliding connection with the rotating rod (23), and the relative sliding direction of the two is parallel to the length direction of the rotating rod (23); a second extension unit (232) is arranged on the rotating rod (23), and the second extension unit (232) is used for pushing the second rotating shaft (231) to slide.

3. The welding robot according to claim 1, wherein: The welding torch (25) is in sliding connection with the connecting rod (24), and the relative sliding direction of the two is parallel to the length direction of the connecting rod (24); a third extension unit (241) is arranged on the connecting rod (24), and the third extension unit (241) is used for pushing the welding torch (25) to slide. The distance between the axis of the welding gun (25) and the midpoint of the connecting rod (24) is less than half the distance between the first hinge shaft (211) and the first rotating shaft (221).

4. The welding robot according to claim 1, characterized in that: The welding gun (25) is obliquely arranged, and the axis of the welding gun (25) forms an angle of 10-20° with the base line.

5. The welding robot according to claim 1, characterized in that: A counterweight is arranged on the rotating rod (23), and the center of gravity of the counterweight is eccentric to the second hinge shaft (212).

6. The welding robot according to claim 1, characterized in that: A first motor (111) is fixedly arranged on the slide rail (11), a first screw rod (112) is rotatably arranged on the slide rail (11), the cross frame (12) is threadedly connected with the first screw rod (112), and the first motor (111) is configured to drive the first screw rod (112) to rotate; A second motor (121) is fixedly arranged on the cross frame (12), a second screw rod (122) is rotatably arranged on the cross frame (12), the fixed end (131) is threadedly connected with the second screw rod (122), and the second motor (121) is configured to drive the second screw rod (122) to rotate; A third motor (133) is fixedly arranged on the fixed end (131), a third screw rod (134) is rotatably arranged on the fixed end (131), the free end (132) is threadedly connected with the third screw rod (134), and the third motor (133) is configured to drive the third screw rod (134) to rotate.

7. The welding robot according to claim 1, characterized in that: A first driving motor (135) is fixedly arranged on the free end (132), and the first driving motor (135) is configured to drive the frame (21) to rotate; and the first driving motor (135) is a servo motor or a stepping motor.

8. A control method for controlling a welding robot as claimed in any one of the claims 1 to 7 to make a welded joint of two workpieces to be welded, characterized in that, Comprising: S1, acquiring joint information of two workpieces to be welded, the joint information comprising a joint track; S2, controlling the mobile assembly to drive the welding assembly to move, so that the tungsten tip is located at a preset depth position of the joint, and the projection of the base line in the vertical direction is located on the joint track; S3, controlling the mobile assembly to drive the welding assembly to move, so that the projection of the base line in the vertical direction moves along the joint track, and the welding gun (25) performs welding.

9. The control method according to claim 8, characterized in that: The control of the mobile assembly to drive the welding assembly to move comprises: controlling the cross frame (12) to slide in a first direction and controlling the telescopic frame (13) to slide in a second direction, so that the free end (132) translates in a horizontal direction; controlling the telescopic frame (13) to extend or retract in a vertical direction, so that the free end (132) translates in the vertical direction.

10. The control method according to claim 8, characterized in that: The S3 comprises: In the case of welding the bottom of the butt joint, the crank (22) is locked when the welding gun (25) is controlled to perform welding; In the case of welding the upper part of the butt joint, the crank (22) is controlled to continuously rotate when the welding gun (25) is controlled to perform welding, so that the welding gun (25) swings in the width direction of the joint while moving in the length direction of the joint.

11. The control method according to claim 10, wherein: the joint information further comprises a joint depth, a groove angle, and a root gap; in the case of welding the upper part of the butt joint, the first rotating shaft (221) is controlled to slide in the length direction of the crank (22) and the second rotating shaft (231) is controlled to slide in the length direction of the rotating rod (23) according to the joint depth, the groove angle, the root gap, and the depth of the welding position, so that the amplitude of the swinging of the welding gun (25) in the width direction of the joint is adapted to the joint width of the welding position.

12. The control method according to claim 11, wherein: for a V-shaped groove, the distance between the first hinged shaft (211) and the first rotating shaft (221) after the first rotating shaft (221) is controlled to slide in the length direction of the crank (22), and the distance between the second hinged shaft (212) and the second rotating shaft (231) after the second rotating shaft (231) is controlled to slide in the length direction of the rotating rod (23) are obtained according to the following manner: ， wherein, L 1 represents the distance of the first articulation axis to the first rotation axis after controlling the first rotation axis to slide along the length direction of the crank, L 2 represents the distance of the second articulation axis to the second rotation axis after controlling the second rotation axis to slide along the length direction of the rotation lever, H represents the depth of the joint, h represents the depth of the welding position, θ represents the angle of the bevel, d represents the root gap.

13. The control method according to claim 8, wherein: the S3 comprises: S31, pre-welding, a plurality of pre-welding points are determined in the length direction of the joint, and the moving assembly is controlled to move the welding assembly to each pre-welding point and perform spot welding; the sequence of the spot welding is: from the middle to both ends of the joint length direction, each pre-welding point is alternately performed; S32, sectional welding, any two adjacent pre-welding points are identified as a to-be-welded section, and the moving assembly is controlled to move the welding assembly from the middle to both ends of the joint length direction to alternately perform each to-be-welded section.

14. The control method according to claim 10, wherein: in the case of welding the upper part of the butt joint, for the corner section of the joint, the rack (21) is controlled to rotate around the base line when the welding gun (25) is controlled to perform welding, so that the plane where the first hinged shaft (211) and the second hinged shaft (212) are located coincides with the normal line of the joint trajectory of the corner section.

15. The control method according to claim 14, wherein: in the case of welding the upper part of the butt joint, for the corner section of the joint, the welding gun (25) is controlled to slide a preset distance in the length direction of the connecting rod (24) towards the outside of the corner, and the projection of the base line in the vertical direction is controlled to slide a preset distance in the normal line of the joint trajectory of the corner section towards the inside of the corner when the welding gun (25) is controlled to perform welding.

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