Method for gripping a bent pipe by means of a robot and use thereof

Abstract

The application discloses a method for grabbing a bent pipe by using a manipulator and application thereof, solves the problem of pipe blanking by manual operation in the prior art, has the beneficial effect of effectively grabbing the bent pipe, and specifically has the following technical scheme: a method for grabbing a bent pipe by using a manipulator, comprising a pipe bender and a manipulator which are connected with a control unit respectively; the pipe bender sends data of a bent pipe being processed to the control unit, and the control unit transmits the data of the bent pipe to the manipulator; the control unit converts coordinates of characteristic points of the bent pipe into coordinates of the characteristic points in a pipe bender machining coordinate system, and converts the coordinates of the characteristic points in the pipe bender machining coordinate system into coordinates of the characteristic points in a manipulator working coordinate system; the control unit determines a grabbing position of the bent pipe according to the coordinates of the characteristic points in the manipulator working coordinate system and the length of the bent pipe, selects a grabbing point at the grabbing position, and the grabbing point is a point on a line of the characteristic points.

Description

Technical Field

[0001] This invention relates to the field of rail transit, and in particular to a method for gripping curved pipes using a robotic arm and its application. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Pipes are bent into bends using existing bending equipment such as CNC bending machines. After the bending process is completed, the pipes are mainly cut manually in the existing technology. When processing large quantities of pipes of the same specification, robotic arms are also used for cutting.

[0004] In the aerospace and automotive industries, robotic arms are sometimes used for material handling in certain work scenarios. This typically involves selecting a gripping point in simulation software, which then interacts with the robotic arm software to guide the gripping process. Alternatively, a teaching method is used, where the robotic arm grips the material first, adds it to a database, and then retrieves it for subsequent processing of the same pipe. The inventors found that these two methods are primarily suitable for gripping large quantities of the same type of bent pipe. For bent pipes with a wider variety of types, simulation software or teaching methods require inputting multiple sets of data, with each type of pipe requiring a separate simulation or teaching demonstration, resulting in slow gripping speeds and limiting the method's universal applicability. Furthermore, the interaction between simulation software and the robotic arm still relies heavily on manual intervention, resulting in a high degree of human involvement.

[0005] In the rail transit industry, there are many specifications and few batches of bent pipes, which is a type of processing with many varieties and few specifications. It is difficult to use robotic arms for material cutting. The method of interaction or teaching between simulation software and robotic arms is not suitable for the rail transit industry. At present, there is no way to use robotic arms to cut bent pipes in this industry. The cutting is mainly done manually, which has the problems of high cutting intensity and low efficiency. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for gripping bent pipes using a robotic arm, enabling rapid identification and gripping of bent pipes, facilitating the implementation of automated production lines for bent pipe processing, replacing manual material handling, and improving the level of automation in bent pipe processing.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A method for gripping a bent pipe using a robotic arm includes:

[0009] The pipe bending machine and the robotic arm are respectively connected to the control unit;

[0010] The pipe bending machine sends the data of the pipe being bent to the control unit;

[0011] The control unit extracts the feature points of the bent pipe from the data of the bent pipe, converts the coordinates of the feature points of the bent pipe into the coordinates of the feature points of the bent pipe in the coordinate system of the pipe bending machine, and sends the coordinates of the feature points of the bent pipe in the coordinate system of the robot arm to the robot arm.

[0012] The control unit determines the gripping position of the bend based on the coordinates of the bend's feature points in the robot's working coordinate system and the length of the bend. It then selects a gripping point at the gripping position. The gripping point is a point on the line where the bend's feature points are located. When the bend's pipe length L is less than or equal to the set length, a single gripping point is selected. When the bend's pipe length L is greater than the set length, at least one gripping point is selected. The control unit sends the coordinate information of the gripping point to the robot, which then grips the bend.

[0013] As described above, a method for gripping a bent pipe using a robotic arm includes the following feature points: the initial processing end of the bent pipe, the confluence point of the bend, and the point where the bent pipe contacts the clamping end of the bending machine. This method simplifies the bending process and facilitates determining the gripping position and gripping point.

[0014] As described above, in a method for gripping a bent pipe using a robotic arm, the feature points of the bent pipe are located on the central axis of the bent pipe, or on the extension line of the central axis of the bent pipe.

[0015] Considering the characteristics of the bend, the confluence point at the bend refers to the confluence point of the extended lines of the center axes on both sides of the bend, which facilitates the quick confirmation of the coordinates of the confluence point.

[0016] As described above, in a method for gripping a bent pipe using a robotic arm, when the pipe length L ≤ 500 mm, the straight section of the bent pipe away from the clamping end of the pipe bending machine is used as the gripping position.

[0017] The midpoint between the initial processing end of the pipe and the confluence point of the pipe bend is used as the gripping point to avoid interference between the robot arm and the clamping end, and to ensure stable gripping of the pipe.

[0018] As described above, a method for gripping a bent pipe using a robotic arm is described, wherein the pipe length L of the bent pipe is greater than 500 mm, and the middle section of the bent pipe is used as the gripping position.

[0019] The method described above for using a robotic arm to grip a bent pipe, wherein the pipe length L > 500 mm, includes the following method for confirming the position of a single gripping point:

[0020] Take a section of pipe with a length of l 0.5 , l0.5 It is half the length of the pipe in the bend;

[0021] Starting from the initial machining end of the bend, l 0.5 The difference between the lengths of the points at the initial processing end of the bend and the confluence point of the first bend is calculated successively. When Δ > 0, for l 0.5 The difference between the length between the initial processing end of the bend and the junction point of the first bend, and the length between the junction point of the first bend and the junction point of the adjacent second bend, is calculated as Δ = L / 2 - l1 - l2. When the difference Δ ≤ 0, the point between the junction point of the first bend and the junction point of the adjacent second bend is taken as the grab point.

[0022] The method described above for using a robotic arm to grip a bent pipe, wherein the pipe length L > 500 mm, includes the following steps for confirming the positions of the two gripping points:

[0023] Take a section of pipe with a length of l 0.5 , l 0.5 It is half the length of the pipe in the bend;

[0024] Starting from the initial machining end of the bend, l 0.5 The difference between the lengths of the points at the initial processing end of the bend and the confluence point of the first bend is calculated successively. When Δ > 0, for l 0.5 The length between the initial processing end of the bend and the junction point of the first bend, and the length between the junction point of the first bend and the junction point of the adjacent second bend are further subtracted by Δ = L / 2 - l1 - l2. When the difference Δ ≤ 0, the junction points of the first and second bends are taken as two grab points.

[0025] As described above, in a method for gripping a bent pipe using a robotic arm, the pipe length L is greater than the minimum allowable pipe length L0, which is determined by the depth of the bending machine's clamping end, the mold radius, and the gripping width of the robotic arm.

[0026] As described above, in order to avoid interference between the robot arm and the pipe bending machine and ensure stable and reliable gripping of the pipe, the control unit determines the gripping posture of the robot arm on the pipe according to the bending condition and length of the pipe.

[0027] The control unit determines the movement path of the robot arm based on the gripping posture and the coordinate information of the gripping point, and the robot arm grips the curved pipe along this movement path.

[0028] In the method described above for using a robotic arm to grasp a bent pipe, the control unit determines the grasping posture of the bent pipe by including the following:

[0029] When the bend in the pipe occurs within a plane:

[0030] When the pipe length L ≤ 500mm, the pipe is gripped horizontally from the side away from the bending machine.

[0031] When the pipe length L of the bend is greater than 500mm, the bend is gripped horizontally from the side away from the bending machine or from top to bottom.

[0032] When the bend in the pipe occurs within a space:

[0033] On the side of the pipe away from the bending machine, obtain the normal direction of the gripping point, and grip the pipe along the normal direction of the gripping point.

[0034] The method described above for using a robotic arm to grasp a curved pipe includes the following coordinate transformation process for the feature points of the curved pipe:

[0035] Let coordinate system A be the coordinate system where the feature point of the pipe bend is located, coordinate system J be the coordinate system for pipe bending machining, and coordinate system W be the coordinate system for the robot's operation.

[0036] After rotating coordinate system A around the x-axis by a set angle, it coincides with coordinate system J, thus obtaining the coordinates P of the pipe bending feature point in the pipe bending machine coordinate system. J (x J ,y J ,z J )=P(x,y,z)·R J ;

[0037] After rotating and translating coordinate system J, the coordinates P of the bend feature point in the robot's working coordinate system are obtained. W (x W ,y W ,z W ) = P J (x J ,y J ,z J )·R w +L(a,b,c)=P(x,y,z)·R J ·R w +L(a,b,c).

[0038] Secondly, the present invention also provides an application of a method for gripping curved pipes using a robotic arm, which is applied to the blanking of curved pipes in the field of rail transit.

[0039] The beneficial effects of the present invention are as follows:

[0040] 1) This invention provides a method for gripping bent pipes. The pipe bending machine is connected to a robot and a control unit. The control unit can extract the feature points of the bent pipe and convert the coordinates of the feature points into the coordinates of the feature points in the working coordinate system of the robot. Based on this coordinate information and the length of the bent pipe, the control unit determines the gripping position of the bent pipe and selects the gripping point to grip the bent pipe. In this way, regardless of the length of the bent pipe, the bent pipe can be quickly identified and gripped, which is conducive to the implementation of automated production line for pipe bending, replaces manual material cutting, and improves the level of automation in pipe bending.

[0041] 2) In this invention, it is considered that the theoretical coordinate system of the pipe bending machine, the processing coordinate system of the pipe bending machine, and the working coordinate system of the robot are different in the actual production process. The control unit transforms the feature points of the pipe bending in the three coordinate systems. Before the robot grabs the pipe, the coordinate systems of the three must be unified. After unification, the control unit imports the coordinates of the feature points of the pipe bending into the coordinate system of the robot. Only in this way can the robot grab the pipe bending according to the coordinates.

[0042] 3) In this invention, the points at the initial processing end of the bend, the confluence point of the bend, and the point where the bend contacts the clamping end of the bending machine are taken as bend feature points. This is to simplify the bend, facilitate the determination of the gripping position and gripping point, and make it easier for the robot to grip. It also makes full use of the characteristics of the bend. The confluence point of the bend refers to the confluence point of the extended lines of the center axes on both sides of the bend. The coordinates of the confluence point are easy to extract, which in turn facilitates the determination of the gripping point coordinates.

[0043] 4) In this invention, when the pipe length of the bend is less than 500mm, considering that one end of the bend is clamped, the straight section of the bend away from the clamping end of the bend machine is used as the gripping position to avoid interference between the robot and the clamping end, and to ensure stable gripping of the bend.

[0044] 5) In this invention, when the pipe length L of the bend is greater than 500mm, the position of the gripping point is determined by the length of the junction point of the initial processing end of the bend and the first bend, and the length between the junction points of the two bends at the farthest distance. One gripping point or two gripping points can be selected to ensure accurate gripping of the bend.

[0045] 6) In this invention, the gripping posture of the robot arm is determined by the bending condition of the pipe, whether it is a planar bend or a spatial bend, and the length of the pipe. Then, based on the determined gripping posture and the coordinate information of the gripping point, the movement path of the robot arm can be determined, and thus the robot arm needs to grip the pipe according to this movement path. This not only ensures the stable gripping of the pipe by the robot arm, but also effectively avoids interference between the robot arm and the pipe bending machine.

[0046] 7) The method for gripping curved pipes provided by this invention transforms the coordinates of the characteristic points of the curved pipe and determines the gripping position and gripping point of the curved pipe based on the coordinates of the characteristic points of the curved pipe and the length of the curved pipe. It also determines the gripping posture of the robotic arm, which can achieve accurate and stable gripping of curved pipes. It can be applied to the field of rail transit, realize reliable gripping of curved pipes of different specifications and regardless of batch size, and eliminate the need for manual gripping, greatly improving work efficiency. Attached Figure Description

[0047] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0048] Figure 1 These are the coordinates of feature points of the bent pipe in a method for gripping a bent pipe using a robotic arm, according to one or more embodiments of the present invention.

[0049] Figure 2 This is a schematic diagram of the coordinate system of the feature points of the curved pipe in a method for grasping a curved pipe using a robotic arm according to one or more embodiments of the present invention.

[0050] Figure 3 This is a schematic diagram of the processing coordinate system of a pipe bending machine in a method for gripping a bent pipe using a robotic arm according to one or more embodiments of the present invention.

[0051] Figure 4 This is a schematic diagram of the working coordinate system of the robotic arm in a method for grasping a bent pipe according to one or more embodiments of the present invention.

[0052] Figure 5 This is a schematic diagram of the gripping point when the pipe length L ≤ 500 mm in one or more embodiments of the present invention, which is a method for gripping a bent pipe using a robotic arm.

[0053] Figure 6 This is a schematic diagram of the gripping point when the pipe length L > 500 mm in a method for gripping a bent pipe using a robotic arm according to one or more embodiments of the present invention.

[0054] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0055] Wherein: 1. pipe bend, 2. mold rotation, 3. pipe bending machine clamping end, point D is the point at the initial processing end of the pipe bend, point E is the confluence point of the first pipe bend, point G is the confluence point of the second pipe bend, point F is the point where the pipe bend contacts the clamping end of the pipe bending machine, and point p is the gripping point. Detailed Implementation

[0056] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0057] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0058] As described in the background section, existing technologies mainly rely on manual labor for bending pipe gripping. To address this technical problem, this invention proposes a method for gripping bending pipes using a robotic arm.

[0059] In a typical embodiment of the present invention, reference is made to Figure 1 As shown, a method for gripping a curved pipe using a robotic arm includes the following:

[0060] The pipe bending machine and the robotic arm are respectively connected to the control unit;

[0061] The pipe bending machine sends the data of the pipe bending 1 being processed to the control unit;

[0062] The control unit extracts the feature points of the bent pipe through the data of the bent pipe 1, converts the coordinates of the feature points of the bent pipe into the coordinates of the bent pipe feature points in the working coordinate system of the robot arm through the coordinates in the bending machine coordinate system, and sends the coordinates of the bent pipe feature points in the working coordinate system of the robot arm to the robot arm.

[0063] The control unit determines the gripping position of the bend 1 based on the coordinates of the bend feature points in the robot's working coordinate system and the length of the bend 1, and selects a gripping point at the gripping position. The gripping point is a point on the line where the bend feature points are located. When the pipe length L of the bend is less than or equal to a set length such as 500mm, a single gripping point is selected. When the pipe length L of the bend is greater than 500mm, at least one gripping point is selected. The control unit sends the coordinate information of the gripping point to the robot, and the robot grips the bend.

[0064] In this embodiment, the control unit can be a computer or a PLC controller, or it can be the controller of the pipe bending machine. Through the control unit, the conversion of the characteristic points of the pipe bending is realized, and the gripping position and gripping point of the robot are determined and sent to the robot, which then grips the pipe bending.

[0065] It should be noted that the pipe bending process includes three actions: linear feed, planar bending, and rotation around the axial direction. Simplifying pipe bending as the bending of the pipe's central axis, a pipe bend can be described as a combination of several straight line segments and circular arcs.

[0066] Figure 1 China P i (x i ,y i ,z i (i = 0, 1, 2, 3) are the coordinates of the characteristic points of the bend, Q i (x i ,y i ,z i (i = 0, 1, 2) are the coordinates of the tangent point of the bend, R is the bending radius, and O0(x0, y0, z0) is the origin of the planar bend.

[0067] Understandably, after the pipe bending process is completed, the robotic arm needs to grasp and unload the pipe, requiring the grasping position to be accurately determined. Before grasping, the coordinate system must be unified, and then the grasping position must be determined.

[0068] Because the coordinate systems of the feature points of the pipe bend, the processing coordinate system of the pipe bender, and the working coordinate system of the robot are not unified, position determination is impossible. In order to achieve the gripping of the pipe bend, the above three coordinate systems are transformed to achieve unification.

[0069] The coordinate system in which the feature point of the bend is located is referred to as coordinate system A (see...). Figure 2 As shown in the figure, the origin is o, the oy axis is horizontal to the right, the ox axis is downward, and the oz axis is determined by the right-hand rule.

[0070] The machining coordinate system of the pipe bending machine, abbreviated as coordinate system J (see Figure 3), has the origin at o, which is the position of the pipe bending chuck; the oy axis is horizontal to the left, which is the axial feed direction of the pipe bending machine; the ox axis is coplanar and perpendicular to the oy axis, which is the opposite direction of the pipe bending machine; and the oz axis is vertically downward.

[0071] The robot's coordinate system is established according to the world coordinate system, abbreviated as coordinate system W (see...). Figure 4 As shown in the figure, the origin is o, the ox axis is horizontal to the right, the oy axis is downward, and the oz axis is determined by the right-hand rule.

[0072] In this embodiment, the coordinate transformation process of the feature points of the bend includes the following:

[0073] Define the coordinates of the feature point of the bend in coordinate system A as P(x,y,z), and the corresponding coordinate point in coordinate system J as P_j. J (x J ,y J ,z J The corresponding coordinate point in coordinate system W is P. W(x W ,y W ,z W ).

[0074] Transform coordinate system A and coordinate system J:

[0075] Specifically, coordinate system A is rotated 180° around the x-axis to coincide with coordinate system J, and the rotation matrix R is set to... J , Then P J (x J ,y J ,z J )=P(x,y,z)·R J .

[0076] Regarding the transformation between coordinate systems J and W: Coordinate system J is first rotated 90° around the z-axis, then 90° around the x-axis (or first rotated 90° around the y-axis, then 90° around the z-axis, or first rotated 90° around the x-axis, then 90° around the y-axis), and the rotation matrix around the x-axis is... Rotation matrix around the y-axis Rotation matrix around z-axis Let the rotation matrix R w ,but

[0077]

[0078] It's important to understand that in practical applications, the origins of coordinate system W and coordinate system J do not coincide, requiring a translation of coordinate system J. Assuming the lengths of the origins of coordinate system J and W in the three coordinate directions are a, b, and c, and the translation coordinates are L(a,b,c), then P... W (x W ,y W ,z W ) = P J (x J ,y J ,z J )·R w +L(a,b,c)=P(x,y,z)·R J ·R w +L(a,b,c).

[0079] Therefore, using spatial coordinates, the characteristic points of the bend include the point at the initial processing end of the bend (point D), the confluence point of the bend, and the point where the bend contacts the clamping end of the bending machine (point F). The characteristic points are located on the central axis of the bend, or on its extension. The confluence point of the bend refers to the point where the extensions of the central axes on both sides of the bend meet. The coordinates of the confluence point are easy to extract, thus facilitating the determination of the gripping point coordinates. A single bend can have one or multiple confluence points.

[0080] Understandably, due to differences in outer diameter, length, and shape, different methods of gripping different pipes will be used. Let the depth of the clamping end of the pipe bending machine be l, the radius of the pipe bending machine's rotating mold 2 be R, the width of the robot arm's gripper be b, and the minimum allowable length of the pipe bend be L0 = l + 2R + b.

[0081] Regarding the selection of the grab point location:

[0082] When the pipe length L≤500mm: use a single gripping point, take the straight segment of the pipe away from the clamping end of the pipe bending machine as the gripping position, and calculate the coordinates of the last straight segment (the straight segment farthest from the clamping end of the pipe bending machine), and take the midpoint between the point at the initial processing end of the pipe bending and the confluence point of the pipe bending as the gripping point.

[0083] Specifically, such as Figure 5 As shown, point D is the point at the initial processing end of the bend. Point p, the middle point in the direction from point D to point E, is selected as the gripping point.

[0084] When the pipe length L of the bend is greater than 500mm: when using a single gripping point, first take a section of pipe length l. 0.5 , l 0.5 The length of the pipe bend is 1 / 2; starting from the initial machining end of the bend, l 0.5 The difference between the lengths of the initial processing end of the bend (point D) and the meeting point (point E) of the first bend is calculated. When the difference Δ≤0, the meeting point of the bend closest to the first point and the point (point D) of the initial processing end of the bend are taken as the gripping point.

[0085] When Δ > 0, for l 0.5 The difference Δ = L / 2 - l1 - l2 is calculated between the length between the initial processing end of the bend and the merging point of the first bend, and between the merging point of the first bend and the merging point of the adjacent second bend. The merging point of the second bend refers to the merging point (point G) closest to the merging point of the first bend. When the difference Δ ≤ 0, the point between the merging point of the first bend and the merging point of the adjacent second bend, such as point p, is taken as the grab point.

[0086] like Figure 6 As shown, assume that pipe 1 has two bends, point D is the initial processing end, the length between point D and point E is l1, calculate the difference Δ = L / 2 - l1. When Δ > 0, continue to calculate the difference Δ = L / 2 - l1 - l2, the length between point E and point G is l2; when Δ ≤ 0, take the point (point p) in the middle between point E and point G as the grab point.

[0087] In addition, it is easy to understand that during the gripping process, in order to avoid interference between the gripper and the pipe or pipe bending machine, the gripping posture of the end effector of the robot arm needs to be planned in advance based on the pipe routing and characteristics. To this end, the control unit determines the gripping posture of the robot arm on the pipe based on the bending condition of the pipe (which can be manually input by the operator) and the length of the pipe. The control unit determines the movement path of the robot arm based on the gripping posture and the coordinate information of the gripping point, and the robot arm grips the pipe along this movement path.

[0088] Specifically, determining the gripping posture for the bent pipe includes the following:

[0089] When the bend 1 is bent in a plane: when the pipe length L ≤ 500mm, the bend is gripped horizontally from the side away from the bending machine; when the pipe length L > 500mm, the bend is gripped horizontally from the side away from the bending machine or from top to bottom.

[0090] When the pipe 1 is bent in space: on the side of the pipe away from the bending machine, obtain the normal direction of the gripping point, and grip the pipe along the normal direction of the gripping point.

[0091] Furthermore, it is easy to understand that the robotic arm is an existing robotic arm with multiple degrees of freedom, capable of horizontal and vertical movement. The end of the robotic arm is a gripper connected to the robotic arm, which can rotate relative to the robotic arm, and the robotic arm can also rotate. Because the gripping point is located on the central axis of the curved pipe, the control unit sends the coordinate information of the gripping point to the robotic arm and defines the gripping posture of the gripper on the curved pipe, thereby defining the movement path of the robotic arm. The robotic arm moves according to this movement path, specifically controlling the movement of the robotic arm and gripper in the robotic arm to achieve the gripping of the curved pipe.

[0092] The method for gripping bent pipes provided in this embodiment connects the pipe bending machine, the robot arm, and the control unit. The control unit can extract the feature points of the bent pipe and convert the coordinates of the feature points into the coordinates of the feature points in the working coordinate system of the robot arm. Based on this coordinate information and the length of the bent pipe, the control unit determines the gripping position of the bent pipe and selects the gripping point to grip the bent pipe. In this way, regardless of the length of the bent pipe, the bent pipe can be quickly identified and gripped, which is conducive to the implementation of automated production lines for pipe bending, replaces manual material cutting, and improves the level of automation in pipe bending.

[0093] Example 2

[0094] The difference between this embodiment and Embodiment 1 is that:

[0095] When the pipe length L of the bend is greater than 500mm, two gripping points are used. The method for confirming the positions of the two gripping points includes the following:

[0096] Take a section of pipe with a length of l 0.5 , l 0.5 The length of the pipe bend is 1 / 2; starting from the initial machining end of the bend, l 0.5 Calculate the difference between the lengths of the points (point D) at the initial processing end of the bend and the confluence point (point E) at the first bend. When Δ > 0, for l 0.5 The length between the point at the initial processing end of the bend and the meeting point of the first bend (i.e., the meeting point E near the initial processing end of the bend), and the length between the meeting point of the first bend and the meeting point of the adjacent second bend (the length between point E and point G) are further subtracted by Δ = L / 2 - l1 - l2. When the difference Δ ≤ 0, the meeting points of the first and second bends are used as two gripping points. The coordinates of the meeting points of the first and second bends are obtained and sent to the robot, which grips the bend according to the coordinates of the two meeting points.

[0097] Accordingly, because there are two gripping points, the end effector of the robotic arm needs to have two grippers. One gripper moves toward the confluence point of the first bend in the pipe to grip one part of the bend, and the other gripper moves toward the confluence point of the second bend in the pipe to grip the other part of the bend, thereby achieving stable and reliable gripping of longer bends.

[0098] It is understood that the method of using a robotic arm to grip the bent pipe described in Embodiment 1 and Embodiment 2 can be applied to the blanking of bent pipes in the rail transit field. Regardless of whether the batch is large or small, or whether the bent pipes are of the same or different specifications, the above gripping method can achieve stable gripping of the bent pipes without much human intervention, which can improve the blanking speed of bent pipes.

[0099] Of course, if other fields also require the feeding or unloading of bent pipes, the method of using a robotic arm to grip the bent pipes described in this application can also be used.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for gripping a bent pipe using a robotic arm, characterized in that, Includes the following: The pipe bending machine and the robotic arm are respectively connected to the control unit; The pipe bending machine sends the data of the pipe being bent to the control unit; The control unit extracts the feature points of the bent pipe from the data of the bent pipe, converts the coordinates of the feature points of the bent pipe into the coordinates of the feature points of the bent pipe in the coordinate system of the pipe bending machine, and sends the coordinates of the feature points of the bent pipe in the coordinate system of the robot arm to the robot arm. The control unit determines the gripping position of the bend based on the coordinates of the bend feature points in the robot's working coordinate system and the length of the bend. It then selects a gripping point at the gripping position. The gripping point is a point on the line where the bend feature points are located. When the pipe length L of the bend is less than or equal to the set length, a single gripping point is selected. When the pipe length L of the bend is greater than the set length, at least one gripping point is selected. The control unit sends the coordinate information of the gripping point to the robot, which then grips the bend. The characteristic points of the bend include the point at the initial processing end of the bend, the confluence point at the bend, and the point where the bend contacts the clamping end of the bend machine; the confluence point at the bend refers to the confluence point of the extended lines of the center axes on both sides of the bend. The pipe length L of the bend is greater than the set length. When using a single gripping point position confirmation method, the following are included: Take a section of pipe length , It is half the length of the pipe in the bend; Starting from the initial machining end of the bend, The length between the initial processing end of the bend and the confluence point of the first bend is successively calculated. When the difference Δ > 0, the length is calculated as follows: The length between the point at the initial machining end of the bend and the point where the first bend of the pipe meets. The length between the confluence point of the first pipe bend and the confluence point of the adjacent second pipe bend. Continue to calculate the difference. When the difference Δ≤0, the point between the confluence of the first bend and the confluence of the second bend is taken as the grab point. The pipe length L of the bend is greater than the set length. When the method of confirming the position of two gripping points is used, the following content is included: Take a section of pipe length , It is half the length of the pipe in the bend; Starting from the initial machining end of the bend, The length between the initial processing end of the bend and the confluence point of the first bend is successively calculated. When the difference Δ > 0, the length is calculated as follows: The length between the point at the initial machining end of the bend and the point where the first bend of the pipe meets. The length between the confluence point of the first pipe bend and the confluence point of the adjacent second pipe bend. Continue to calculate the difference. When the difference Δ≤0, the confluence points of the first and second bends of the pipe are taken as two grab points.

2. The method for gripping a bent pipe using a robotic arm according to claim 1, characterized in that, The feature point of the bend is located on the central axis of the bend, or on the extension line of the central axis of the bend.

3. The method for gripping a bent pipe using a robotic arm according to claim 1, characterized in that, When the pipe length L of the bent pipe is less than or equal to 500mm, the straight section of the bent pipe away from the clamping end of the pipe bending machine shall be used as the gripping position. The midpoint between the initial processing end of the bend and the confluence point of the bend is used as the gripping point.

4. The method for gripping a bent pipe using a robotic arm according to claim 1, characterized in that, The pipe length L of the bend is greater than 500mm, and the middle section of the bend is used as the gripping position.

5. A method for gripping a bent pipe using a robotic arm according to claim 1, characterized in that, The pipe length L of the bend is greater than the minimum allowable pipe length L0. The minimum allowable pipe length L0 is determined by the depth of the clamping end of the pipe bending machine, the mold radius, and the clamping width of the robot arm.

6. A method for gripping a bent pipe using a robotic arm according to claim 1, characterized in that, The control unit determines the gripping posture of the robot arm on the bent pipe based on the bending condition and length of the bent pipe. The control unit determines the movement path of the robot arm based on the gripping posture and the coordinate information of the gripping point, and the robot arm grips the curved pipe along this movement path.

7. A method for gripping a bent pipe using a robotic arm according to claim 6, characterized in that, The control unit determines the gripping posture of the bent pipe by including the following: When the bend in the pipe occurs within a plane: When the pipe length L ≤ 500mm, the pipe is gripped horizontally from the side away from the bending machine. When the pipe length L of the bend is greater than 500mm, the bend is gripped horizontally from the side away from the bending machine or from top to bottom. When the bend in the pipe occurs within a space: On the side of the pipe away from the bending machine, obtain the normal direction of the gripping point, and grip the pipe along the normal direction of the gripping point.

8. A method for gripping a bent pipe using a robotic arm according to claim 1, characterized in that, The coordinate transformation process of the feature points of the bend includes the following: Let coordinate system A be the coordinate system containing the feature point of the pipe bend, and let P(x,y,z) be the coordinates of the feature point in coordinate system A. Let coordinate system J be the coordinate system for pipe bending machining, and let P be the coordinates of the feature point in coordinate system J. J (x J ,y J ,z J The robot's working coordinate system is coordinate system W, and the coordinates of the bend feature point in coordinate system W are P. W (x W ,y W ,z W ); After rotating coordinate system A around the x-axis by a set angle, it coincides with coordinate system J, thus obtaining the coordinates P of the pipe bending feature point in the pipe bending machine coordinate system. J (x J ,y J ,z J ) = P(x,y,z)·R J R J It is a rotation matrix; After rotating and translating coordinate system J, the translation coordinates are L(a,b,c), thus obtaining the coordinates P of the bend feature point in the robot's working coordinate system. W (x W ,y W ,z W )= P J (x J ,y J ,z J )·R w + L(a,b,c)= P(x,y,z)·R J ·R w + L(a,b,c), R w It is a rotation matrix.

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