Robot Welding Trajectory Planning Method for LNG Membrane Tank Corrugated Plate Lap Joint

Abstract

The present invention discloses a robot welding trajectory planning method for lap joints of corrugated plates in LNG membrane tanks, comprising: dividing the geometric contour line of the corrugated portion of the joint into segments C2 to C6 according to the curvature change of the corrugated portion of the joint, and smoothly connecting them in sequence; using the endpoints and midpoints of each segment as feature points O3 to O13 for the joint corrugated trajectory planning, and using feature point O8 as the origin of the trajectory planning user coordinate system to determine the x, y, and z axis directions; obtaining the position coordinates of each feature point through the radius of each segment and the coordinates of feature point O8; and calculating the rotation angle W, rotation angle P, and rotation angle R at any feature point, thereby obtaining the posture coordinates of each feature point. The present invention solves the problem of difficulty in solving the problem when using the robot kinematics inverse solution in the traditional trajectory planning method, the lack of a unified and programmed solution method, and the problem of multiple solutions.

Description

Technical Field

[0001] The present invention relates to the technical field of welding robots, and in particular to a robot welding trajectory planning method for lap joints of corrugated plates in LNG membrane tanks. Background Art

[0002] The global development of liquefied natural gas (LNG) carriers is relatively short, spanning only about 40 years. However, due to technological monopolies in other countries, my country faces difficulties in manufacturing LNG carriers, resulting in slow industry development and enormous potential for growth. The main barrier wall of the MARK III LNG membrane tank is constructed from 304L stainless steel corrugated plates. The quality of its welding determines the integrity of the MARK III membrane tank enclosure system and is crucial to the successful construction of LNG carriers. Due to its complex shape, the complex shapes at the bottom corners of the corrugated plates still require manual welding. This results in inconsistent weld quality in the spatial positions of the corrugated plates, low production efficiency, and high demands on manual skills.

[0003] A search of existing technical literature and patents revealed that there is currently no research on robot welding trajectory planning methods for lap joints of corrugated plates in LNG membrane tanks. A Chinese invention patent application with patent number 202111012727.8 proposes a method for continuous welding of the transition area between corrugated plates and angle steel in a fuel tank. The patent details the process parameters for welding with inert gas shielding in all directions on the corrugated plates, achieving continuous welding of corrugated angle plates in the lap transition area between thin and thick plates, ensuring weld quality in the transition area of the corrugated angle plates, improving the joint appearance and flaw detection pass rate in this area, improving the construction environment, shortening the construction period, and reducing production costs. However, no feasible trajectory planning method has been proposed for the welding trajectory design of the corrugated portion.

[0004] Therefore, those skilled in the art are committed to developing a robot welding trajectory planning method for lap joints of corrugated plates of LNG membrane tanks. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to provide a robot welding trajectory planning method for lap joints of corrugated plates of LNG membrane tanks.

[0006] To achieve the above objectives, the present invention provides a robot welding trajectory planning method for a lap joint of a corrugated plate in an LNG membrane tank. The lap welded joint of the corrugated plate includes a straight portion and a corrugated portion. The straight portion includes a first section C1 and a tail section C7. The method comprises the following steps:

[0007] Step 1: Divide the geometric contour line of the corrugated portion of the joint into a starting arc C2, an upslope arc C3, a top arc C4, a downslope arc C5, and an ending arc C6 according to the curvature change of the corrugated portion of the corrugated plate. The starting arc C2, the upslope arc C3, the top arc C4, the downslope arc C5, and the ending arc C6 are smoothly connected in sequence. The radius of the starting arc C2 is r1, the radius of the upslope arc C3 is r2, the radius of the top arc C4 is r3, the radius of the downslope arc C5 is r4, and the radius of the ending arc C6 is r5.

[0008] Step 2: The two endpoints O3 and O5 and the midpoint O4 of the starting arc C2, the two endpoints O5 and O7 and the midpoint O6 of the uphill arc C3, the two endpoints O7 and O9 and the midpoint O8 of the top arc C4, the two endpoints O9 and O10 of the downhill arc C5, 11 and the midpoint O 10 , the two endpoints O of the end segment arc C6 11 and O 13 and the midpoint O 12 , as the feature points of trajectory planning for the corrugated part of the LNG membrane tank corrugated plate lap joint robot welding, namely O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13 ;

[0009] Step 3: Take the feature point O8 as the origin of the robot welding trajectory for the corrugated part of the LNG membrane tank corrugated plate lap joint. The coordinates are (0,0,0). The x, y, and z axis directions of the user coordinate system are determined as follows: the upward direction perpendicular to the straight part is the positive direction of the z axis, and the vertical direction along the feature point O8 is the positive direction of the z axis. 13 The direction to O3 is the positive direction of the y-axis. According to the directions of the y-axis and the z-axis, the positive direction of the x-axis can be obtained by the right-hand rule.

[0010] Step 4: Obtain the characteristic points O3, O4, O5, O6, O7, O9, O10, O11, O12, O13, O14, O15, O16, O17, O18, O19, O20, O21, O22, O23, O24, O25, O26, O27, O28, O29, O30, O31, O32, O33, O34, O35, O36, O37, O38, O39, O40, O41, O42, O43, O44, O45, O46, O47, O48, O49, O50, O51, O52, O53, O54, O55, O6, O7, O8, O9, O10, O11, O12, O13, O14, O15, O16, O17, 10 , O 11 , O 12 , O 13 The coordinates (X j ,Y j ,Z j ), where j = 3, 4, 5, 6, 7, 9, 10, 11, 12, 13;

[0011] Step 5: On the geometric contour line of the corrugated part of the corrugated plate lap joint, the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13 The angles between the normal and the z-axis are W3, W4, W5, W6, W7, W8, W9, W 10 、W 11 、W 12 、W 13 When welding the lap joint of the corrugated plate of the LNG membrane tank, the lap upper plate and the lap bottom plate of the corrugated plate are overlapped in sequence, and the center line of the welding gun axis installed on the robot manipulator is kept perpendicular to the geometric contour line of the corrugated part of the joint and deflected toward the lap bottom plate by an angle β. The robot manipulator holds the welding gun and moves along the geometric contour line of the corrugated part of the joint at the characteristic points O3, O4, O5, O6, O7, O8, O9, O10, O11, O12, O13, O14, O15, O16, O17, O18, O19, O20, O21, O22, O23, O24, O25, O26, O27, O28, O29, O30, O31, O32, O33, O34, O35, O36, O37, O38, O39, O40, O41, O42, O43, O44, O45, O46, O47, O48, O49, O50, O51, O52, O53, O6 10 , O 11 , O 12 , O 13 The rotation angles W are W3, W4, W5, W6, W7, W8, W9, W 10 、W 11 、W 12 、W 13 ;

[0012] Step 6: Calculate at any feature point O j The rotation angle P at any feature point O j The rotation angle R at .

[0013] Furthermore, the corrugated plate has a thickness of 1 to 2 mm, and the overlap amount of the overlap welding is 10 to 20 mm.

[0014] Furthermore, in step 1, the radius r1 of the starting arc C2 is equal to the radius r5 of the ending arc C6, and the radius r2 of the uphill arc C3 is equal to the radius r4 of the downhill arc C5.

[0015] Furthermore, the specific steps of step 4 are:

[0016] According to the radius r1 of the starting segment arc C2, the radius r2 of the upslope segment arc C3, the radius r3 of the top segment arc C4, the radius r4 of the downslope segment arc C5, and the radius r5 of the ending segment arc C6, a coordinate system is established in the 3D CAD software, with the feature point O8 as the coordinate origin, the x, y, and z axis directions are consistent with the x, y, and z axis directions of the robot welding trajectory planning user coordinate system, and the geometric contour line of the corrugated part of the LNG membrane tank corrugated plate is drawn. The feature points O3, O4, O5, O6, O7, O9, O10, O11, O12, O13, O14, O15, O16, O17, O18, O19, O20, O21, O22, O23, O24, O25, O26, O27, O28, O29, O30, O31, O32, O33, O34, O35, O36, O37, O38, O39, O40, O41, O42, O43, O44, O45, O46, O47, O48, O49, O50, O51, O52, O53, O54, O55 10 , O 11 , O 12 , O 13 The position coordinates (X j ,Y j ,Z j );

[0017] The specific steps of the method for obtaining the rotation angle W in step 5 are: automatically reading the feature points O3, O4, O5, O6, O7, O9, O10 and O11 in the 3D CAD software. 10 , O 11 , O 12 , O 13 The rotation angles W3, W4, W5, W6, W7, W8, W9, W 10 、W 11 、W 12 、W 13 .

[0018] Furthermore, the deflection angle β in step 5 ranges from -8° to -12°, wherein a negative value indicates deflection toward the overlapping base plate.

[0019] Furthermore, step 4 also includes adding the following corrections to the y-axis and z-axis respectively when calculating the position coordinates of the welding gun at each feature point:

[0020] y-axis:

[0021] z-axis: +d×cosW j ,

[0022] Where d represents the distance between the welding gun and the workpiece.

[0023] Furthermore, the specific steps of step 6 are:

[0024] During the robot welding process of the lap joint of the corrugated plate of the LNG membrane tank, the robot's manipulator holding the welding gun moves along the geometric contour line of the corrugated part of the joint at the characteristic point O. j The rotation angle P at jis the angle between the projection of the center line of the welding gun axis on the XOZ plane and the positive direction of the Z axis when the welding gun moves to the corresponding feature point. At this time, the positive direction of the Y axis leaves the paper, the welding gun is in the counterclockwise direction of the positive direction of the Z axis, and is negative in the clockwise direction of the positive direction of the Z axis. The trajectory of the robot's manipulator holding the welding gun and moving along the geometric contour line of the corrugated part of the joint is at the feature point O. j The rotation angle R j It is the angle between the projection of the welding gun axis centerline on the XOY plane and the negative direction of the Y axis when the welding gun moves to the corresponding characteristic point. At this time, the positive direction of the Z axis leaves the paper. The counterclockwise direction of the welding gun in the negative direction of the Y axis is positive, and the clockwise direction in the negative direction of the Y axis is negative.

[0025] Define the end of the welding gun as the origin of the welding gun Cartesian coordinate system. The coordinate axis direction of the welding gun Cartesian coordinate system is consistent with the coordinate axis direction of the user coordinate system. At the same time, define the unit vector of the welding gun axis centerline pointing to the origin of the welding gun Cartesian coordinate system, then:

[0026] At any feature point O j When the single controlled welding gun rotates around the Y axis, the rotation angle P is recorded as P j1 , and its calculation steps are:

[0027] a=cosβ×sinW j ,

[0028]

[0029]

[0030] At any feature point O j When the single controlled welding gun rotates around the Z axis, the rotation angle R is recorded as R j1 , and its calculation steps are:

[0031] a=cosβ×sinW j ,

[0032]

[0033]

[0034] Among them, a and b are auxiliary variables in the solution process; h p It represents the cone height obtained by rotating the unit vector around the X-axis. R' represents the angle between the projection of the center line of the welding gun axis on the XOY plane and the negative direction of the X-axis.

[0035] Furthermore, the specific steps of step 6 also include:

[0036] In the process of robot welding trajectory of LNG membrane tank corrugated plate lap joint, the parameters of rotation angle P and rotation angle R are controlled in a coordinated manner to make the welding gun held by the robot manipulator move along the geometric contour line of the corrugated part of the joint at the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13 The welding gun rotates around the Y and Z axes simultaneously to ensure that the center line of the welding gun axis is perpendicular to the geometric contour line of the corrugated part of the joint, and the welding gun posture is deflected at an angle of β toward the overlapped bottom plate; the parameters of the coordinated control of the rotation angle P and the rotation angle R are the parameters of the single control rotation angle P. j1 and single control rotation angle R j1 Multiply each by its own correction parameter cos 2 (W j ) and sin 2 (W j ),Right now:

[0037] At any feature point O j The parameter P of the rotation angle P at j The calculation formula is:

[0038]

[0039] At any feature point O j The calculation formula of the parameter Rj of the rotation angle R at is:

[0040]

[0041] Furthermore, the step 6 further includes:

[0042] The robot's manipulator holds the welding gun and moves along the geometric contour line of the corrugated part of the joint, at the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13 The coordinates of the robot working point (X j ,Y j ,Z j ,W j ,P j ,R j ) stipulates that the welding gun moves along the geometric contour line of the corrugated part of the joint to the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13The welding gun posture is set at the right position to complete the trajectory planning of the corrugated part of the robot welding of the LNG membrane tank corrugated plate lap joint; through the robot's arc motion instructions, during the robot's automatic welding process of the LNG membrane tank corrugated plate lap joint, the welding gun clamped by the robot's manipulator moves along the planned trajectory of the corrugated part of the joint in a specified posture.

[0043] Furthermore, when the welding gun held by the robot's manipulator moves along the trajectory of the planned corrugated part of the joint in a prescribed posture, the robot's joint angular velocity is ensured not to exceed the limit range of the robot, thereby ensuring that the center line of the welding gun axis installed on the robot's manipulator is always perpendicular to the geometric contour line of the joint.

[0044] The most prominent advantages of this invention are that, on the one hand, it overcomes the difficulties encountered by traditional trajectory planning methods using inverse kinematics, the lack of a unified, programmable solution, and the multi-solution problem. On the other hand, by determining the welding gun posture at three characteristic points of a circular arc, when using circular arc instructions to execute trajectory movement with a six-axis robot, the welding gun can maintain real-time perpendicularity to the corrugated sheet simply by ensuring that the joint angular velocity does not exceed the robot's limit. This lays the foundation for achieving robotic automated welding of corrugated sheet metal in spatial position.

[0045] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the surveying and modeling of a corrugated plate and a coordinate system according to a preferred embodiment of the present invention;

[0047] Figure 2 Schematic diagram of the arc shape of the corrugated portion of the corrugated plate of a preferred embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the corrugated portion welding gun posture and corrugated segmentation of a preferred embodiment of the present invention;

[0049] Figure 4 2. It is a schematic diagram of the welding gun side deflection angle of a preferred embodiment of the present invention;

[0050] Figure 5 1 is a schematic diagram of calculating the rotation angle P parameter at a characteristic point of a corrugated portion according to a preferred embodiment of the present invention;

[0051] Figure 6 It is a schematic diagram of calculating the rotation angle R parameter at the characteristic points of the corrugated part of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0052] The following describes preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0053] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0054] Example

[0055] This embodiment provides a robot welding trajectory planning method for lap joints of corrugated plates in LNG membrane tanks. In this embodiment, the corrugated plates are 1.2 mm thick and the overlap of the lap weld is 10 to 20 mm. The specific steps are as follows:

[0056] S1. Scan the corrugated plate using a 3D scanner (e.g., Artec Space Spider 3D scanner), and measure and correct the scanned corrugated plate model using 3D computer-aided design (CAD) software (e.g., Solidworks software) to obtain a 3D model of the corrugated plate, such as Figure 1 shown.

[0057] S2, such as Figure 2 、 Figure 3 As shown, the trajectory planning includes the trajectory of the straight part of the joint and the trajectory of the corrugated part of the joint, wherein the straight part of the joint is composed of two straight part trajectories, namely the first section (C1) and the last section (C7). According to the curvature change of the corrugated part of the joint of the corrugated plate, the geometric contour line of the corrugated part of the joint is composed of five arcs, namely the starting arc (C2), the upslope arc (C3), the top arc (C4), the downslope arc (C5), and the ending arc (C6), which are smoothly connected in sequence. The radius of the starting arc (C2) is r1, the radius of the upslope arc (C3) is r2, the radius of the top arc (C4) is r3, the radius of the downslope arc (C5) is r4, and the radius of the ending arc (C6) is r5. As shown Figure 2 As shown, r1 and r5 are equal, which is 9.06mm; r2 and r4 are equal, which is 78.67mm; and r3 is 11.91mm.

[0058] S3, such as Figure 3As shown, the two endpoints O3 and O5 and the midpoint O4 of the starting segment arc (C2), the two endpoints O5 and O7 and the midpoint O6 of the upslope segment arc (C3), the two endpoints O7 and O9 and the midpoint O8 of the top segment arc (C4), the two endpoints O9 and O10 of the downslope segment arc (C5), 11 and the midpoint O 10 , the two endpoints O of the ending arc (C6) 11 and O 13 and the midpoint O 12 , as the 11 feature points for trajectory planning of the corrugated part of the robot welding of the LNG membrane tank corrugated plate lap joint, namely O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13 .

[0059] S4, such as Figure 1 、 Figure 3 As shown in the figure, the feature point O8 is used as the origin of the trajectory planning of the corrugated part of the joint of the robot welding of the LNG membrane tank corrugated plate lap joint. The coordinates are (0,0,0). The x, y, and z axis directions of the user coordinate system are determined as follows: the direction perpendicular to the straight part is the positive direction of the z axis, and the direction along the feature point O8 is the positive direction of the z axis. 13 The direction to O3 is the positive direction of the y-axis. According to the directions of the y-axis and the z-axis, the positive direction of the x-axis is obtained by the right-hand rule.

[0060] S5, such as Figure 2 、 Figure 3 、 Figure 4 As shown, the characteristic points O3, O4, O5, O6, O7, O9, O10, O11, O12, O13, O14, O15, O16, O17, O18, O19, O20, O21, O22, O23, O24, O25, O26, O27, O28, O29, O30, O31, O32, O33, O34, O35, O36, O37, O38, O39, O40, O41, O42, O43, O44, O45, O46, O47, O48, O49, O50, O51, O52, O53, O54, O55, O6, O7, O8, O9, O10, O11, O12, O13, O14, O15, O16, O17, O18 10 , O 11 , O 12 , O 13 The coordinates (X j ,Y j ,Z j ), where j = 3, 4, 5, 6, 7, 9, 10, 11, 12, 13.

[0061] S6, such as Figure 3 、 Figure 5 、 Figure 6 As shown, on the geometric contour line of the corrugated part of the corrugated plate lap joint, the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12, O 13 The angles between the normal and the z-axis are W3, W4, W5, W6, W7, W8, W9, W 10 、W 11 、W 12 、W 13 During the robot welding process of the lap joint of the LNG membrane tank corrugated plate, the two corrugated plates (lap upper plate and lap bottom plate) are overlapped together in sequence, such as Figure 4 As shown in the figure, the center line of the welding gun axis mounted on the robot manipulator is kept perpendicular to the geometric contour line of the corrugated part of the joint and deflected backward (towards the base plate) by an angle β, with a value range of β from -8° to -12° (negative value indicates deflection toward the base plate). The parameters of the rotation angle W of the robot manipulator holding the welding gun along the geometric contour line of the joint corrugated part at these 11 feature points are W3, W4, W5, W6, W7, W8, W9, W10, W11, W12, W13, W14, W15, W16, W17, W18, W19, W20, W21, W22, W23, W24, W25, W26, W27, W28, W29, W30, W31, W32, W33, W34, W35, W36, W37, W38, W39, W40, W41, W42, W43, W44, W55, W6 10 、W 11 、W 12 、W 13 ;

[0062] During welding, the distance between the welding gun and the workpiece is set to 1 to 5 mm, for example 2 mm. Therefore, when calculating the spatial coordinates of the welding gun at each feature point, the following corrections should be added to the y-axis and z-axis respectively:

[0063] y-axis:

[0064] z-axis: +2×cosW j ;

[0065] At any feature point (O j ) is the parameter of the rotation angle P at j ) is calculated as:

[0066]

[0067] At any feature point (O j ) is the parameter of the rotation angle R at j ) is calculated as:

[0068]

[0069] Where, j = 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13;

[0070] Taking O7 as an example, the coordinates and rotation angle W of O7 are obtained from the model in SolidWorks software. The coordinates of its user coordinate system (X7, Y7, Z7) are (0, -9.646, -1.878) after corrections to the y-axis and z-axis. β is -10° (negative values indicate deflection toward the base plate), and the angle W7 between the normal of O7 and the positive z-axis is 43.86°. Then, we have:

[0071] W7=43.86,

[0072]

[0073]

[0074] Therefore, when the center line of the welding gun axis installed on the robot manipulator is kept perpendicular to the geometric contour line of the joint at the feature point O7 and the deflection angle toward the overlapping base plate is 10° (β is -10°), the robot position that needs to be input is: (0, -9.646, -1.878, 43.86, -7.144, -6.855).

[0075] S7, calculate all the characteristic points O3, O4, O5, O6, O7, O8, O9, O10, O20, O30, O40, O50, O60, O70, O80, O90, O100, O110, O120, O130, O140, O150, O160, O170, O180, O190, O210, O220, O2 10 , O 11 , O 12 , O 13 The six-axis parameters are used to run the trajectory of the entire corrugated part through the arc instructions of a six-axis robot (such as a Fanuc robot).

[0076] like Figure 2 、 Figure 3 As shown, the characteristic points O3, O4, O5, O6, O7, O9, O 10 , O 11 , O 12 , O 13 The coordinates of the user coordinate system (X j ,Y j ,Z j ) are obtained as follows:

[0077] According to the radius r1 of the starting arc (C2), the radius r2 of the upslope arc (C3), the radius r3 of the top arc (C4), the radius r4 of the downslope arc (C5), and the radius r5 of the ending arc (C6), the geometric contour line of the corrugated part of the LNG membrane tank corrugated plate is drawn in the Solidworks software. The feature point O8 is used as the origin of the user coordinate system for the trajectory planning of the corrugated part of the robot welding of the lap joint of the LNG membrane tank corrugated plate. The upward direction perpendicular to the straight part is the positive direction of the z axis. Along the feature point O 13The direction to O3 is the positive direction of the y-axis. According to the directions of the y-axis and the z-axis, the positive direction of the x-axis is obtained by the right-hand rule. The feature points O3, O4, O5, O6, O7, O9, O 10 , O 11 , O 12 , O 13 The coordinates of the user coordinate system are obtained, and according to the different distances d between the welding gun and the workpiece, the y-axis and z-axis parameters are corrected as described in S6, and finally the characteristic points O3, O4, O5, O6, O7, O9, O 10 , O 11 , O 12 , O 13 The coordinates of the user coordinate system at (X j ,Y j ,Z j ).

[0078] like Figure 3 、 Figure 5 、 Figure 6 As shown in the figure, during the robot welding process of the lap joint of the corrugated plate of the LNG membrane tank, the robot's manipulator holding the welding gun moves along the geometric contour line of the corrugated part of the joint at the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13 The rotation angle P at (respectively P3, P4, P5, P6, P7, P8, P9, P 10 、P 11 、P 12 、P 13 ) is the angle between the projection of the center line of the welding gun axis on the XOZ plane and the positive direction of the Z axis when the welding gun moves to the corresponding characteristic point. At this time, the positive direction of the Y axis leaves the paper. The value of the welding gun in the counterclockwise direction of the positive direction of the Z axis is positive, and the value of the welding gun in the clockwise direction of the positive direction of the Z axis is negative, such as Figure 5 As shown in the side view, the robot's manipulator holds the welding gun and moves along the geometric contour line of the corrugated part of the joint at the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13 The rotation angle R at (R3, R4, R5, R6, R7, R8, R9, R 10 、R 11 、R 12 、R 13) is the angle between the projection of the welding gun axis centerline on the XOY plane and the negative direction of the Y axis when the welding gun moves to the corresponding characteristic point. At this time, the positive direction of the Z axis leaves the paper. The counterclockwise direction of the welding gun in the negative direction of the Y axis is positive, and the clockwise direction in the negative direction of the Y axis is negative. Figure 6 As shown in the top view;

[0079] Define the end of the welding gun as the origin of the welding gun Cartesian coordinate system. The coordinate axis direction of the welding gun Cartesian coordinate system is consistent with the coordinate axis direction of the user coordinate system of the corrugated plate robot welding trajectory planning. At the same time, define the unit vector of the welding gun axis center line pointing to the origin of the welding gun Cartesian coordinate system. When the welding gun axis center line deflects by 10° (β is -10°) toward the lap bottom plate, the cone height (h) obtained by rotating the unit vector around the X axis is p ) is sin10°, the radius of the cone base (r p ) is cos10°, then:

[0080] like Figure 5 As shown, at any feature point (O j ), the rotation angle of the single controlled welding gun when it rotates around the Y axis is recorded as P j1 , and its calculation steps are:

[0081] a=cosβ×sinW j ,

[0082]

[0083]

[0084] like Figure 6 As shown, at any feature point (O j ), the rotation angle of the single controlled welding gun when it rotates around the Z axis is recorded as R j1 , and its calculation steps are:

[0085] a=cosβ×sinW j ,

[0086]

[0087]

[0088] In the process of LNG membrane tank corrugated plate welding trajectory planning, the parameters of the rotation angle P and the rotation angle R are collaboratively controlled to make the welding gun held by the robot manipulator move along the geometric contour line of the corrugated part of the joint at the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13The welding gun rotates around the Y and Z axes simultaneously to achieve a welding gun posture in which the center line of the welding gun axis is perpendicular to the geometric contour line of the corrugated part of the joint and the welding gun is deflected by an angle β toward the overlapped base plate. The parameters of the coordinated control of the rotation angle P and the rotation angle R are the parameters of the P in the single control rotation angle P mode. j1 and R in single control rotation angle R mode j1 Multiply each by its own correction parameter cos 2 (W j ) and sin 2 (W j ),Right now:

[0089] At any feature point (O j ) is the parameter P of the rotation angle P at j The calculation formula is:

[0090]

[0091] At any feature point (O j ) is the parameter R of the rotation angle R at j The calculation formula is:

[0092]

[0093] The robot's manipulator holds the welding gun and moves along the geometric contour line of the corrugated part of the joint, at the characteristic points O3, O4, O5, O6, O7, O8, O9, O 10 , O 11 , O 12 , O 13 The robot's position coordinates (X j ,Y j ,Z j ,W j ,P j ,R j ) specifies the welding gun posture for movement along the geometric contour of the joint corrugated portion to the 11 characteristic points, thus completing the trajectory planning for the corrugated portion of the joint for robotic welding of LNG membrane tank corrugated plate lap joints. By using the robot's circular motion instructions, the welding gun held by the robot's manipulator can be moved along the planned trajectory of the joint corrugated portion in the specified posture during the robotic automatic welding process of the LNG membrane tank corrugated plate lap joints;

[0094] When the welding gun held by the robot's manipulator moves along the trajectory of the planned corrugated part of the joint in a prescribed posture, it is necessary to ensure that the angular velocity of the robot's joints does not exceed the limit range of the robot, so as to ensure that the center line of the welding gun axis installed on the robot's manipulator is always perpendicular to the geometric contour line of the joint.

[0095] The above describes in detail the preferred embodiments of the present invention. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible by one of ordinary skill in the art without inventive effort. Therefore, any technical solution that can be derived by one of ordinary skill in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A robot welding trajectory planning method for LNG membrane tank corrugated plate lap joints, wherein the corrugated plate lap joints comprise a straight portion and a corrugated portion, wherein the straight portion comprises a first section C1 and a tail section C7, characterized in that: The method comprises the following steps: Step 1: Divide the geometric contour line of the corrugated portion of the corrugated plate lap joint into a starting arc C2, an upslope arc C3, a top arc C4, a downslope arc C5, and an ending arc C6 according to the curvature change of the corrugated portion of the corrugated plate lap joint. The starting arc C2, the upslope arc C3, the top arc C4, the downslope arc C5, and the ending arc C6 are smoothly connected in sequence. The radius of the starting arc C2 is r1, the radius of the upslope arc C3 is r2, the radius of the top arc C4 is r3, the radius of the downslope arc C5 is r4, and the radius of the ending arc C6 is r5. Step 2: The two endpoints O3 and O5 and the midpoint O4 of the starting arc C2, the two endpoints O5 and O7 and the midpoint O6 of the uphill arc C3, the two endpoints O7 and O9 and the midpoint O8 of the top arc C4, the two endpoints O9 and O10 of the downhill arc C5, 11 and the midpoint O 10 , the two endpoints O of the end segment arc C6 11 and O 13 and the midpoint O 12 , as the characteristic points for robot welding trajectory planning of the corrugated part of the LNG membrane tank corrugated plate lap joint, namely O3 to O 13 ; Step 3: Take the feature point O8 as the origin of the user coordinate system for robot welding trajectory planning of the corrugated part of the LNG membrane tank corrugated plate lap joint. The coordinates are (0,0,0). The x, y, and z axis directions of the user coordinate system are determined as follows: the upward direction perpendicular to the straight part of the joint is the positive direction of the z axis, and the vertical direction along the feature point O8 is the positive direction of the z axis. 13 The direction to O3 is the positive direction of the y-axis. According to the directions of the y-axis and the z-axis, the positive direction of the x-axis can be obtained by the right-hand rule. Step 4: Obtain feature points O3 to O7, O9 to O10 through the radii r1, r2, r3, r4, r5 of the starting arc C2, the uphill arc C3, the top arc C4, the downhill arc C5, and the ending arc C6 and the coordinates of the feature point O8. 13 The coordinates (X j ,Y j ,Z j ), where j = 3, 4, 5, 6, 7, 9, 10, 11, 12, 13; Step 5: On the geometric contour line of the corrugated part of the corrugated plate lap joint, feature points O3 to O 13 The angles between the normal line at and the z-axis are W3 to W 13 When the robot welds the lap joint of the corrugated plate of the LNG membrane tank, the lap upper plate and the lap bottom plate of the corrugated plate are overlapped together in sequence, and the center line of the welding gun axis installed on the robot manipulator is kept perpendicular to the geometric contour line of the corrugated part of the joint, and deflected toward the lap bottom plate by an angle β. The value range of the deflection angle β is -8° to -12°, where a negative value indicates deflection toward the lap bottom plate. The trajectory of the robot manipulator holding the welding gun moving along the geometric contour line of the corrugated part of the joint is between the feature points O3 and O4. 13 The rotation angle W is W3 to W 13 ; Step 6: Calculate at any feature point O j The rotation angle P at any feature point O j The rotation angle R at During the robot welding process of the lap joint of the corrugated plate of the LNG membrane tank, the robot's manipulator holding the welding gun moves along the geometric contour line of the corrugated part of the joint at the characteristic point O. j The rotation angle P at j is the angle between the projection of the center line of the welding gun axis on the XOZ plane and the positive direction of the Z axis when the welding gun moves to the corresponding feature point. At this time, the positive direction of the Y axis leaves the paper, the welding gun is in the counterclockwise direction of the positive direction of the Z axis, and is negative in the clockwise direction of the positive direction of the Z axis. The trajectory of the robot's manipulator holding the welding gun and moving along the geometric contour line of the corrugated part of the joint is at the feature point O. j The rotation angle R j It is the angle between the projection of the welding gun axis centerline on the XOY plane and the negative direction of the Y axis when the welding gun moves to the corresponding characteristic point. At this time, the positive direction of the Z axis leaves the paper. The counterclockwise direction of the welding gun in the negative direction of the Y axis is positive, and the clockwise direction in the negative direction of the Y axis is negative. Define the end of the welding gun as the origin of the welding gun Cartesian coordinate system. The coordinate axis direction of the welding gun Cartesian coordinate system is consistent with the coordinate axis direction of the user coordinate system. At the same time, define the unit vector of the welding gun axis centerline pointing to the origin of the welding gun Cartesian coordinate system, then: At any feature point O j When the single controlled welding gun rotates around the Y axis, the rotation angle P is recorded as P j1 , and its calculation steps are: a=cosβ×sinW j , At any feature point O j When the single controlled welding gun rotates around the Z axis, the rotation angle R is recorded as R j1 , and its calculation steps are: a=cosβ×sinW j , Among them, a and b are auxiliary variables in the solution process; h p It represents the cone height obtained by rotating the unit vector around the X axis. R' represents the angle between the projection of the center line of the welding gun axis on the XOY plane and the negative direction of the X axis. In the robot welding process of the lap joint of the corrugated plate of the LNG membrane tank, the parameters of the rotation angle P and the rotation angle R are controlled in a coordinated manner so that the welding gun held by the robot manipulator can move along the geometric contour line of the corrugated part of the joint from the characteristic point O3 to O 13 The welding gun rotates around the Y and Z axes simultaneously to ensure that the center line of the welding gun axis is perpendicular to the geometric contour line of the corrugated part of the joint, and the welding gun posture is deflected at an angle of β toward the overlapped bottom plate; the parameters of the coordinated control of the rotation angle P and the rotation angle R are the parameters of the single control rotation angle P. j1 and single control rotation angle R j1 Multiply each by its own correction parameter cos 2 (W j ) and sin 2 (W j ),Right now: At any feature point O j The parameter P of the rotation angle P at j The calculation formula is: At any feature point O j The parameter R of the rotation angle R at j The calculation formula is:

2. The robot welding trajectory planning method for lap joints of LNG membrane tank corrugated plates according to claim 1 is characterized in that: The corrugated plate has a thickness of 1 to 2 mm, and the overlap of the overlap welding is 10 to 20 mm.

3. The robot welding trajectory planning method for LNG membrane tank corrugated plate lap joints according to claim 1 is characterized in that: In step 1, the radius r1 of the starting arc C2 is equal to the radius r5 of the ending arc C6, and the radius r2 of the uphill arc C3 is equal to the radius r4 of the downhill arc C5.

4. The robot welding trajectory planning method for lap joints of LNG membrane tank corrugated plates according to claim 1 is characterized in that: The specific steps of step 4 are: According to the radius r1 of the starting segment arc C2, the radius r2 of the upslope segment arc C3, the radius r3 of the top segment arc C4, the radius r4 of the downslope segment arc C5, and the radius r5 of the ending segment arc C6, a coordinate system is established in the 3D CAD software. With the feature point O8 as the coordinate origin, the x, y, and z axis directions are consistent with the x, y, and z axis directions of the robot welding trajectory planning user coordinate system, and the geometric contour line of the joint corrugated part of the LNG membrane tank corrugated plate is drawn. The feature points O3 to O7, O9 to O10 are automatically read in the 3D CAD software. 13 The position coordinates (X j ,Y j ,Z j ); The specific steps of the method for obtaining the rotation angle W in step 5 are: automatically reading the feature points O3 to O4 in the 3D CAD software 13 The rotation angle W3 to W 13 .

5. The robot welding trajectory planning method for lap joints of LNG membrane tank corrugated plates according to claim 1 is characterized in that: The step 4 also includes adding the following corrections to the y-axis and z-axis respectively when calculating the position coordinates of the welding gun at each feature point: y-axis: z-axis: +d×cosW j , Where d represents the distance between the welding gun and the workpiece.

6. The robot welding trajectory planning method for lap joints of LNG membrane tank corrugated plates according to claim 1, characterized in that: The step 6 further comprises: The robot's manipulator holds the welding gun and moves along the geometric contour line of the corrugated part of the joint, at the characteristic point O3 to O 13 The coordinates of the robot working point (X j ,Y j ,Z j ,W j ,P j ,R j ) stipulates that the welding gun moves along the geometric contour line of the corrugated part of the joint to the characteristic points O3 to O 13 The welding gun posture is set at the right position to complete the trajectory planning of the corrugated part of the robot welding of the LNG membrane tank corrugated plate lap joint; through the robot's arc motion instructions, during the robot's automatic welding process of the LNG membrane tank corrugated plate lap joint, the welding gun clamped by the robot's manipulator moves along the planned trajectory of the corrugated part of the joint in a specified posture.

7. The robot welding trajectory planning method for lap joints of LNG membrane tank corrugated plates according to claim 6 is characterized in that: When the welding gun held by the robot's manipulator moves along the planned trajectory of the joint corrugated part in a prescribed posture, the robot's joint angular velocity is ensured not to exceed the limit range of the robot, thereby ensuring that the center line of the welding gun axis installed on the robot's manipulator is always perpendicular to the geometric contour line of the joint corrugated part.

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