A machining trajectory control method for a pipe bending robot

Abstract

The present invention discloses a processing trajectory control method of a pipe bending robot, and relates to the technical field of pipe processing trajectory. By establishing a trajectory model for robot processing pipes and detection protection of interference zones, the processing of both ends of pipes can be quickly realized, which meets the current needs of high-speed, fully automatic, and diversified pipe processing. The following steps are followed: establish a user coordinate system; establish a pipe spatial coordinate model; input the three-dimensional coordinate point data of the pipe as raw data into the pipe bending parameter model and the robot motion model, establish a robot pipe bending processing path, generate a robot pipe bending processing trajectory program; execute the robot pipe bending processing trajectory program; and turn on the interference protection detection function. It can effectively solve the interference protection problem between the processed end of the pipe and the pipe bending workbench.

Description

Technical Field

[0001] The invention relates to the technical field of pipe processing trajectories, and in particular to a processing trajectory control method of a pipe bending robot. Background Art

[0002] Pipe bending is the process of processing the rough pipe into a certain bending radius, a certain bending angle and a certain shape. It is mainly divided into plane bending parts and space bending parts. The formed parts have been widely used in various industrial fields.

[0003] The known pipe processing workstations mainly use industrial robots and servo pipe bending equipment to process pipe forming. The core of the processing flow is completed by the servo pipe bending equipment. The robot-assisted pipe bending equipment is responsible for loading and unloading operations. The moving axis of the pipe bending equipment controls the feeding distance, the rotating axis controls the rotation angle of the pipe, the bending axis controls the forming angle of the pipe, and the clamping axis and the guide axis are responsible for clamping or loosening the pipe. The core processing data of this process is mainly based on the given digital model and the three-dimensional coordinate point XYZ of the pipe. The original data is input in the user interface, and the processing data is calculated by the programmable logic controller.

[0004] The existing servo pipe bending equipment is more suitable for processing one end of the pipe fittings. It is difficult to quickly realize the processing of both ends of the pipe fittings. Among them, the robot is only responsible for the simple operation of loading and unloading the workpiece. It is difficult to adapt to the current high-speed, fully automatic, and diversified pipe processing needs, and it is difficult to meet the requirements of intelligent manufacturing transformation and upgrading. Another disadvantage is that the movement space of the pipe bending equipment is relatively limited, the multi-axis movement is relatively simple, and the degree of freedom is small, which cannot be compared with the robot's multi-degree-of-freedom and flexible movement processing trajectory; in addition, for complex pipe bending processing technology, it is also easy to interfere between the processed end of the pipe fitting and the pipe bending workbench.

[0005] In this regard, relevant technical solutions for using a pipe bending robot to perform pipe bending and forming are proposed in the prior art, such as the Chinese invention patent with application number "202010560608" and titled "A robot pipe bending processing method and pipe bending processing device" and the Chinese invention patent application with application number "202110427742" and titled "A pipe bending robot trajectory control and forming processing method". The two respectively describe the method of improving deformation in the pipe processing process and the rebound control process in the pipe processing process, and both are related to the elastic deformation of materials; however, the control of the processing trajectory of the pipe bending robot, especially the position and posture required for the robot to process the pipe, has always been difficult to grasp; therefore, how to control the processing trajectory of the pipe bending robot and effectively avoid interference between the processed end of the pipe and the pipe bending workbench has become a technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0006] In view of the above problems, the present invention proposes a processing trajectory control method for a pipe bending robot. By establishing a trajectory model for the robot to process pipe fittings and detection and protection of the interference zone, the processing of both ends of the pipe fittings can be quickly realized, which meets the current needs of high-speed, fully automatic and diversified pipe fitting processing, and can fully meet the precision requirements of pipe fitting processing, and effectively avoids the interference problem between the processed end of the pipe fitting and the pipe bending workbench; in addition, a mode is realized in which a robot replaces the existing supporting robot of the pipe bending equipment, so that the robot can completely independently bear the requirements of the entire pipe bending process.

[0007] The technical solution of the present invention is: carry out according to the following steps:

[0008] Step 1: Establish the user coordinate system;

[0009] The origin of the user coordinate system is located at the exact center of the calibration plate fixed on the pipe bending workbench. The Z-axis of the user coordinate system is vertically upward, and the Y-axis of the user coordinate system is toward the inside of the pipe fitting. The X-axis of the user coordinate system is based on the right-hand rule and is perpendicular to the Y-axis and Z-axis.

[0010] The calibration plate is a calibration tool for the user coordinate system, which is fixedly connected to the rotating axis of the bent pipe before the pipe fitting is processed and is removed during the pipe fitting processing.

[0011] Step 2: Establish the spatial coordinate model of the pipe fitting;

[0012] When establishing the spatial coordinate model of the pipe fitting in step 2, the pipe fitting is regarded as a central symmetric body, and the points on the cross section are symmetric about the center. Its spatial shape can be represented by the center line, the outer diameter of the pipe, and the inner diameter of the pipe. The spatial shape of the pipe fitting to be processed can be described by absolute coordinates and incremental coordinates.

[0013] Step 3: Input the three-dimensional coordinate point data of the pipe fitting as the original data into the pipe bending parameter model and the robot motion model, establish the robot pipe bending processing path, and generate the robot pipe bending processing trajectory program;

[0014] In step 3, the robot motion model includes:

[0015] The feeding distance of the robot end effector, that is, the motion position of the robot end effector in the Cartesian coordinate system;

[0016] The rotation angle of the robot's end effector, that is, the movement angle of the rotation axis on the robot's end gripper;

[0017] The mold-changing motion of the robot end effector, i.e., the motion position of the robot end effector in the Cartesian coordinate system;

[0018] The bending angle of the robot's external axis, that is, the movement angle of the robot's external bending axis;

[0019] The adjustment value of the robot end effector in the Cartesian coordinate system is expressed by the arc length calculated according to the bending angle and bending radius of each bend;

[0020] The absolute position of the robot's external axis linear motion, that is, the movement distance of the robot's clamping axis and guide axis;

[0021] The expression of the bending pipe parameter model is as follows:

[0022] The robot bending angle:

[0023] DOB i-1 =cos -1 ((P i-2 P i-1 .P i-1 P i ) / (|P i-2 P i-1 ||P i-1 P i |)) (1)

[0024] Where: P i-2 P i-1 Indicates P i-2 and P i-1 The vector, P i-1 P i Indicates P i-1 and P i The vector, P i-2 , P i-1 , P i Represents a given three-dimensional coordinate point, DOB i-1 represents the bending angle of the i-1th bend.

[0025] The robot feeding movement distance:

[0026] First feeding distance:

[0027] DBB1=|P0P1|-R*tan(DOB1 / 2) (2)

[0028] Wherein: P0P1 represents the vector of P0 and P1, P0 and P1 represent given three-dimensional coordinate points, R represents the bending radius, DOB1 represents the bending angle of the first bend, and DBB1 represents the first feeding distance.

[0029] Final feeding distance:

[0030] DBB i =|P i-1 P i |-R*tan(DOB i / twenty three)

[0031] Where: P i-1 P i Indicates P i-1 and P i The vector, P i-1 , P i Represents a given three-dimensional coordinate point, R represents the bending radius, DOB i Indicates the bending angle of the last bend, DBB i Indicates the final feed distance.

[0032] Intermediate feeding distance:

[0033] DBB i-1 =|P i-2 P i-1 |-R*[tan(DOB i-2 / 2)-tan(DOB i-1 / twenty four)

[0034] Where: P i-2 P i-1 Indicates P i-2 and P i-1 The vector, P i-2 , P i-1 Represents a given three-dimensional coordinate point, R represents the bending radius, DOB i-2 represents the bending angle of the i-2nd bend, DBB i-1 Indicates the feeding distance of a certain section in the middle.

[0035] The robot's spatial rotation angle:

[0036] POB i-2 =cos -1 ((PV i-2 PV i-1 ) / (|PV i-2 ||PV i-1 |)) (5)

[0037] Where: PV i-2 Indicates point P i-3 , P i-2 , P i-1 Determine the plane P i-3 P i-2 P i-1 Normal vector of i-1 Indicates point P i-2 , P i-1 , P i Determine the plane P i-2 P i-1 P i The normal vector, POB i-2 Represents the spatial rotation angle.

[0038] The adjustment value of the robot end effector in the Y-axis direction in the Cartesian coordinate system:

[0039]

[0040] Where: L i-1 Indicates the adjustment value in the Y-axis direction, DOB i-1 Indicates the bending angle, R i-1 Indicates the bending radius.

[0041] Step 3 specifically includes:

[0042] Step 3.1: Enter the number of processing sections or bends of the pipe;

[0043] Step 3.2: Input the centerline intersection coordinates XYZ (including the first and last points) and the pipe bending radius;

[0044] Step 3.3: Generate the feeding distance, spatial turning angle, bending angle, total length of the tube and bending arc length based on the above parameter model expressions;

[0045] Step 3.4: Combined with the user coordinate system, calculate and obtain the absolute position and posture of the robot end effector and the movement angles of the rotation axis and bending axis.

[0046] Step 4: Execute the robot pipe bending processing trajectory program;

[0047] Step 5: Enable the interference protection detection function.

[0048] In step 5, when the robot end effector is adjusted in the Y-axis direction in the Cartesian coordinate system according to the adjustment value in the Y-axis direction, it is necessary to pre-calculate the position after the movement, and then determine whether the position after the Y-axis movement will trigger a bending die collision, that is, determine whether the robot end effector will pass through the position of the bending forming axis and collide with it. If so, an alarm is issued, otherwise continue to determine; determine whether a guide die collision will be triggered, that is, determine whether the robot end effector will pass through the position of the guide die axis and collide with it, otherwise the robot end effector is controlled to move according to the adjustment value in the Y-axis direction, and if so, continue to determine; determine whether the guide die position is at zero position, if so, the robot end effector is controlled to move according to the adjustment value in the Y-axis direction, otherwise, after moving the guide die axis to zero position, the robot end effector is controlled to move according to the adjustment value in the Y-axis direction. As long as the guide die position is at zero position, no guide die collision will occur.

[0049] In the previous process, when moving the die guide axis to the zero position, interference also needs to be avoided. Before the die guide axis moves, position detection must be performed first, and then it is determined whether the Y-axis position of the robot is within the die guide interference area. If not, the die guide axis can move. If so, first clamp the workpiece through the clamping axis, release the material clamp, and then control the robot end effector to move along the Y-axis to exit the die guide interference area, and then move the die guide axis.

[0050] Similarly, follow the steps below to avoid interference during mold change: first perform position detection, then determine whether the robot's Y-axis position is within the mold guide interference area. If not, perform mold change. If yes, first clamp the workpiece through the mold clamping axis, release the material clamp, and then control the robot's end effector to move along the Y-axis to exit the mold guide interference area. After that, clamp the material rack, release the mold clamping axis and mold guide axis, and then perform mold change.

[0051] The focus of the present invention is the position and posture that the robot needs to execute when processing pipe fittings. This position and posture are the key objects described in the model processing method of this case. The focus is on the robot's actual processing trajectory parameter solution process and the interference protection process of the working space between the robot and the pipe bending workbench. Through the model calculation method, it is converted to a position and posture that the robot can recognize, and finally the process of the robot and the pipe bending workbench cooperating to process pipe fittings is realized.

[0052] On one hand, the present invention can accurately describe the position and posture of the pipe processing trajectory in the robot workspace by realizing the calculation of the pipe processing trajectory model in the robot controller, and can fully meet the precision requirements of pipe processing. On the other hand, by accurately calculating the position relationship between the pipe and the pipe bending workbench and the position where they interfere in the robot controller, the robot automatically adjusts the posture of the pipe clamping and the position of the robot's external axis, and can perform real-time detection of possible collision positions, prompting a collision alarm, which can effectively solve the interference protection problem between the processed end of the pipe and the pipe bending workbench. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a flow chart of robot tube processing;

[0054] Figure 2 Interference protection flow chart of the collision detection of the guide die and bending die

[0055] Figure 3 It is the interference protection flow chart of the guide mold axis motion detection;

[0056] Figure 4 It is the interference protection flow chart of mold change action detection;

[0057] Figure 5 It is a schematic diagram of the establishment of the spatial coordinate model of the pipe fitting;

[0058] Figure 6 It is a flow chart for solving the robot processing trajectory based on the pipe space coordinate model.

[0059] Figure 7 It is a schematic diagram of the structure of the pipe bending robot;

[0060] In the figure: P0, P1, P2, P3 represent the three-dimensional coordinate points XYZ given in the pipe drawing; DBB1, DBB2, DBB3 represent the robot's first-stage feeding movement distance, the middle-stage feeding movement distance, and the final-stage feeding movement distance respectively; DOB1 and DOB2 represent the robot's bending angle; POB represents the robot's rotation angle; R represents the bending radius of the pipe; d represents the distance from the centerline intersection to the centerline, the bending radius, and the arc tangent point;

[0061] Figure 7 Among them, 1 is the mold guide axis, 2 is the mold clamping axis, 3 is the bending forming axis, 4 is the mold layer, 5 is the robot body, 6 is the material clamp, 7 is the rotation axis, 8 is the Cartesian coordinate system, and 9 is the processed pipe fitting. DETAILED DESCRIPTION

[0062] In order to clearly illustrate the technical features of this patent, this patent is elaborated in detail below through a specific implementation method and in combination with its accompanying drawings.

[0063] like Figure 7 As shown, the pipe bending robot in this case includes a robot body 5, an end effector connected to the robot body 5, and a material clamp 6 connected to the end effector, wherein the end effector has a rotating shaft 7, and the processing pipe 9 is clamped by the material clamp 6;

[0064] A pipe bending workbench is also provided beside the robot body 5 , on which there are a guide die axis 1 , a clamping die axis 2 , a bending and forming axis 3 , and a die layer 4 is also provided.

[0065] The pipe design drawings contain the pipe coordinate data XYZ expressed in absolute coordinates in the Cartesian coordinate system. This coordinate point cannot be directly used as the movement point of the robot end effector. It is necessary to build a model based on plane vector theory to generate incremental pipe data YBC, and then combine it with the springback correction data of pipe processing (compensation data is pre-input by humans based on engineering experience). Through the user coordinate system in space or the base coordinate system of the robot, the absolute coordinate data of the robot end effector movement and the absolute movement angle of the robot's external axis are converted to represent the robot's bending processing trajectory.

[0066] like Figures 1 to 6 As shown, a method for constructing a processing trajectory model of a pipe bending robot and interference protection is well described. The specific implementation steps are as follows:

[0067] Step 1: Establish a user coordinate system. The origin of the user coordinate system is located at the exact center of the calibration plate fixed on the pipe bending workbench. The Z-axis direction of the user coordinate system is vertically upward, and the Y-axis direction of the user coordinate system is toward the inner side of the pipe fitting. The X-axis of the user coordinate system is based on the right-hand rule and is perpendicular to the Y-axis and the Z-axis.

[0068] The calibration plate is a calibration tool for the user coordinate system, which is generally fixed on the rotation axis of the bent pipe. This process only needs to be completed before the pipe is processed.

[0069] Step 2: Establish a spatial coordinate model for the pipe fitting, and treat the pipe fitting as a central symmetric body. The points on the cross section are symmetric about the center. Its spatial shape can be represented by the center line, the outer diameter of the pipe, and the inner diameter of the pipe. The spatial shape of the pipe fitting to be processed can be described by absolute coordinates and incremental coordinates.

[0070] Since the pipe is composed of a series of straight segments and arcs, the center line of each straight segment of the curved pipe is regarded as a series of space vectors. The coordinates of the intersection of the center lines of each straight segment are calculated, that is, the coordinate values ​​of the connection points on the design drawing; then the basic concepts and operation rules of vectors are used to accurately calculate the theoretical incremental pipe shape data, and then combined with the user coordinate system established in step 1, the calculation is converted into the absolute position and posture of the robot end effector movement and the movement angle of the robot's external axis.

[0071] The incremental cast data YBC is expressed as follows:

[0072] Y represents: the feed distance DBB (Distance Between Bend) between two bends, which can be expressed as the distance between the end point and the tangent point of the straight line and the arc or the distance between the straight line and the tangent point of two arcs; for the robot, it is the straight line feed length Y before each bend;

[0073] B stands for: Space angle POB (Plane Of Bend), which is the angle between the plane where the first bend is located and the plane where the second bend is located. For the robot, it is the rotation angle B of the clamp holding the pipe.

[0074] C stands for: Degree Of Bend (DOB), which is the angle between the center line of the first straight line and the center line of the second straight line; for the robot, it is the rotation angle C of the bending arm.

[0075] Step 3: Input the three-dimensional coordinate point data of the pipe fitting as the original data into the pipe bending parameter model and the robot motion model, establish the robot pipe bending processing path, and generate the robot pipe bending processing trajectory program;

[0076] The robot motion model includes:

[0077] The feeding distance of the robot end effector, that is, the motion position of the robot end effector in the Cartesian coordinate system;

[0078] The rotation angle of the robot's end effector, that is, the movement angle of the rotation axis on the robot's end gripper;

[0079] The mold-changing motion of the robot end effector, i.e., the motion position of the robot end effector in the Cartesian coordinate system;

[0080] The bending angle of the robot's external axis, that is, the movement angle of the robot's external bending axis;

[0081] The adjustment value of the robot end effector in the Cartesian coordinate system is expressed by the arc length calculated according to the bending angle and bending radius of each bend;

[0082] The absolute position of the robot's external axis linear motion, that is, the movement distance of the robot's clamping axis and guide axis;

[0083] The expression of the bending pipe parameter model is as follows:

[0084] The robot bending angle:

[0085] DOB i-1 =cos -1 ((P i-2 P i-1 .P i-1 P i ) / (|P i-2 P i-1 ||P i-1 P i |)) (1)

[0086] Where: P i-2 P i-1 Indicates P i-2 and P i-1 The vector, P i-1 P i Indicates P i-1 and P i The vector, P i-2 , P i-1 , P i Represents a given three-dimensional coordinate point, DOB i-1 represents the bending angle of the i-1th bend.

[0087] The robot feeding movement distance:

[0088] First feeding distance:

[0089] DBB1=|P0P1|-R*tan(DOB1 / 2) (2)

[0090] Wherein: P0P1 represents the vector of P0 and P1, P0 and P1 represent given three-dimensional coordinate points, R represents the bending radius, DOB1 represents the bending angle of the first bend, and DBB1 represents the first feeding distance.

[0091] Final feeding distance:

[0092] DBB i =|P i-1 P i |-R*tan(DOB i / twenty three)

[0093] Where: P i-1 P i Indicates P i-1 and P i The vector, P i-1 , P i Represents a given three-dimensional coordinate point, R represents the bending radius, DOB i Indicates the bending angle of the last bend, DBB i Indicates the final feed distance.

[0094] Intermediate feeding distance:

[0095] DBB i-1 =|P i-2 P i-1 |-R*[tan(DOB i-2 / 2)-tan(DOB i-1 / twenty four)

[0096] Where: P i-2 P i-1 Indicates P i-2 and P i-1 The vector, P i-2 , P i-1 Represents a given three-dimensional coordinate point, R represents the bending radius, DOB i-2 represents the bending angle of the i-2nd bend, DBB i-1 Indicates the feeding distance of a certain section in the middle.

[0097] The robot's spatial rotation angle:

[0098] POB i-2 =cos -1 ((PV i-2 PV i-1 ) / (|PV i-2 ||PV i-1 |)) (5)

[0099] Where: PV i-2 Indicates point Pi-3 , P i-2 , P i-1 Determine the plane P i-3 P i-2 P i-1 Normal vector of i-1 Indicates point P i-2 , P i-1 , P i Determine the plane P i-2 P i-1 P i The normal vector, POB i-2 Represents the spatial rotation angle.

[0100] The adjustment value of the robot end effector in the Y-axis direction in the Cartesian coordinate system:

[0101]

[0102] Where: L i-1 Indicates the adjustment value in the Y-axis direction, DOB i-1 Indicates the bending angle, R i-1 Indicates the bending radius.

[0103] Step 3 is as follows Figure 6 As shown;

[0104] Step 3.1: Enter the number of processing sections or bends of the pipe;

[0105] Step 3.2: Input the centerline intersection coordinates XYZ (including the first and last points) and the pipe bending radius;

[0106] Step 3.3: Generate the feeding distance, spatial turning angle, bending angle, total length of the tube and bending arc length based on the above parameter model expressions;

[0107] Step 3.4: Calculate the absolute position of the robot end effector and the movement angles of the rotation axis 7 and the bending axis 3 in combination with the user coordinate system.

[0108] Step 4: Execute the robot pipe bending processing trajectory program;

[0109] Step 5: Turn on the interference protection detection function. When the robot is holding the pipe and before the robot end performs movement, calculate and determine the position of the robot end after the movement or the positional relationship between the current position of the robot end and the pipe bending workbench, adjust the position of the robot holding the pipe and the robot's external axes, that is, the positions of the guide mold axis 1, the clamping mold axis 2, and the bending forming axis 3, to avoid interference between the movement of the robot end and the movement of the robot's external axes on the pipe bending workbench.

[0110] Specifically:

[0111] like Figure 2 As shown, when the robot end effector is adjusted in the Y-axis direction in the Cartesian coordinate system according to the adjustment value in the Y-axis direction, it is necessary to pre-calculate the position after the movement, and then determine whether the position after the Y-axis movement will trigger a bending die collision, that is, determine whether the robot end effector will pass through the position of the bending forming axis 3 and collide with it. If so, an alarm is issued, otherwise, the judgment is continued; determine whether a guide die collision will be triggered, that is, determine whether the robot end effector will pass through the position of the guide die axis 1 and collide with it, otherwise, the robot end effector is controlled to move according to the adjustment value in the Y-axis direction, and if so, the judgment is continued; determine whether the guide die position is at zero position, if so, the robot end effector is controlled to move according to the adjustment value in the Y-axis direction, otherwise, after moving the guide die axis to zero position, the robot end effector is controlled to move according to the adjustment value in the Y-axis direction. As long as the guide die position is at zero position, no guide die collision will occur.

[0112] like Figure 3 As shown, in the previous process, when moving the guide die axis to the zero position, interference also needs to be avoided. Before the guide die axis moves, position detection is required first, and then it is determined whether the Y-axis position of the robot is in the guide die interference area. If not, the guide die axis can move. If so, first clamp the workpiece through the clamping die axis, and release the material clamp, and then control the robot end effector to move along the Y-axis to exit the guide die interference area (the moving distance is 50mm higher than the guide die collision setting value), and then move the guide die axis.

[0113] In the above, the user needs to first manually set the collision protection data according to the working space between the robot and the pipe bending workbench, that is, the guide mold collision setting value.

[0114] Similarly, if Figure 4 As shown, follow the steps below to avoid interference during mold change: first perform position detection, then determine whether the robot's Y-axis position is within the mold guide interference area. If not, perform mold change. If so, first clamp the workpiece through the clamping axis, and release the material clamp, then control the robot's end effector to move along the Y-axis to exit the mold guide interference area (the moving distance is 50mm higher than the mold guide collision setting value), then clamp the material rack, release the clamping axis and mold guide axis, and then perform mold change.

[0115] When the present invention performs pipe bending work, Figure 1As shown, the robot moves to the grabbing position of the workpiece to pick up the material, and then feeds the material, presses Y feed, B corner, and C backbend, and judges that the feeding action is completed (the control method is added to the software program. During the execution process, if the feeding is completed, the corresponding instructions in the software will be executed normally. If not, the software will alarm and prompt for abnormality), the external axis starts the bending action, and adjusts the robot end effector in the Y-axis direction according to the above-mentioned Y-axis adjustment value. After the bending is completed (similarly, if the bending is completed, the corresponding instructions in the software will be executed normally. If not, the software will alarm and prompt for abnormality), enter the next bending cycle until the pipe processing is completed.

[0116] There are many specific implementation ways of the present invention. The above is only the preferred implementation mode of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principle of the present invention. These improvements should also be regarded as the protection scope of the present invention.

Claims

1. A processing trajectory control method for a pipe bending robot, characterized in that: Follow these steps: Step 1: Establish the user coordinate system; Step 2: Establish the spatial coordinate model of the pipe fitting; Step 3: Input the three-dimensional coordinate point data of the pipe fitting as the original data into the pipe bending parameter model and the robot motion model, establish the robot pipe bending processing path, and generate the robot pipe bending processing trajectory program; Step 4: Execute the robot pipe bending processing trajectory program; Step 5: Turn on the interference protection detection function. When the robot is holding the pipe and before the robot end performs movement, calculate and determine the position of the robot end after the movement or the position relationship between the current position of the robot end and the pipe bending workbench, adjust the position of the robot holding the pipe and the position of the robot's external axis to avoid interference between the movement of the robot end and the movement of the robot's external axis on the pipe bending workbench; In step 5, when the robot end effector is adjusted in the Y-axis direction of the Cartesian coordinate system according to the adjustment value in the Y-axis direction, it is necessary to pre-calculate the position after the movement, and then determine whether the position after the Y-axis movement will trigger a bending die collision, that is, determine whether the robot end effector will pass through the position of the bending forming axis and collide with it. If so, an alarm is issued, otherwise, continue to determine; determine whether a guide die collision will be triggered, that is, determine whether the robot end effector will pass through the position of the guide die axis and collide with it, otherwise the robot end effector is controlled to move according to the adjustment value in the Y-axis direction, and if so, continue to determine; determine whether the guide die position is at zero position, if so, the robot end effector is controlled to move according to the adjustment value in the Y-axis direction, otherwise, after moving the guide die axis to zero position, the robot end effector is controlled to move according to the adjustment value in the Y-axis direction. As long as the guide die position is at zero position, no guide die collision will occur; When moving the die guide axis to zero position, interference also needs to be avoided. Before the die guide axis moves, position detection is required first, and then it is determined whether the Y-axis position of the robot is within the die guide interference area. If not, the die guide axis can move. If it is, the workpiece is clamped by the clamping axis first, and the material clamp is released. Then the robot end effector is controlled to move along the Y-axis to exit the die guide interference area, and then the die guide axis is moved. Follow the steps below to avoid interference during mold change. First, perform position detection, and then determine whether the robot's Y-axis position is within the mold guide interference area. If not, perform mold change. If so, first clamp the workpiece through the clamping axis and release the material clamp, then control the robot's end effector to move along the Y-axis to exit the mold guide interference area. After that, clamp the material rack, release the clamping axis and mold guide axis, and then perform mold change.

2. The processing trajectory control method of a pipe bending robot according to claim 1, characterized in that: The origin of the user coordinate system is located at the exact center of the calibration plate fixed on the pipe bending workbench. The Z-axis of the user coordinate system is vertically upward, and the Y-axis of the user coordinate system is toward the inside of the pipe fitting. The X-axis of the user coordinate system is based on the right-hand rule and is perpendicular to the Y-axis and Z-axis. The calibration plate is a calibration tool for the user coordinate system, which is fixedly connected to the rotating axis of the bent pipe before the pipe fitting is processed and is removed during the pipe fitting processing.

3. The processing trajectory control method of a pipe bending robot according to claim 1, characterized in that: When establishing the spatial coordinate model of the pipe fitting in step 2, the pipe fitting is regarded as a central symmetric body, and the points on the cross section are symmetric about the center. Its spatial shape can be represented by the center line, the outer diameter of the pipe, and the inner diameter of the pipe. The spatial shape of the pipe fitting to be processed can be described by absolute coordinates and incremental coordinates.

4. The processing trajectory control method of a pipe bending robot according to claim 1, characterized in that: The robot motion model in step 3 includes: The feeding distance of the robot end effector, that is, the motion position of the robot end effector in the Cartesian coordinate system; The rotation angle of the robot's end effector, that is, the movement angle of the rotation axis on the robot's end gripper; The mold-changing motion of the robot end effector, i.e., the motion position of the robot end effector in the Cartesian coordinate system; The bending angle of the robot's external axis, that is, the movement angle of the robot's external bending axis; The adjustment value of the robot end effector in the Cartesian coordinate system is expressed by the arc length calculated according to the bending angle and bending radius of each bend; The absolute position of the linear motion of the robot's external axis, that is, the movement distance of the robot's clamping axis and guide axis.

5. The processing trajectory control method of a pipe bending robot according to claim 1, characterized in that: The expression of the bending pipe parameter model in step 3 is as follows: The robot bending angle: DOB i-1 =basket -1 ((P i-2 P i-1 .P i-1 P i ) / (|P i-2 P i-1 ||P i-1 P i |)) (1) Where: P i-2 P i-1 Indicates P i-2 and P i-1 The vector, P i-1 P i Indicates P i-1 and P i The vector, P i-2 , P i-1 , P i Represents a given three-dimensional coordinate point, DOB i-1 represents the bending angle of the i-1th bend; The robot feeding movement distance: First feeding distance: DBB1=|P0P1|-R*tan(DOB1 / 2) (2) Where: P0P1 represents the vector of P0 and P1, P0 and P1 represent given three-dimensional coordinate points, R represents the bending radius, DOB1 represents the bending angle of the first bend, and DBB1 represents the first feeding distance; Final feeding distance: DBB i =|P i-1 P i |-R*tan(DOB i / 2) (3) Where: P i-1 P i Indicates P i-1 and P i The vector, P i-1 , P i Represents a given three-dimensional coordinate point, R represents the bending radius, DOB i Indicates the bending angle of the last bend, DBB i Indicates the final feeding distance; Intermediate feeding distance: DBB i-1 =|P i-2 P i-1 |-R*[tan(DOB i-2 / 2)-tan(DOB i-1 / 2)] (4) Where: P i-2 P i-1 Indicates P i-2 and P i-1 The vector, P i-2 , P i-1 Represents a given three-dimensional coordinate point, R represents the bending radius, DOB i-2 represents the bending angle of the i-2nd bend, OBB i-1 Indicates the feeding distance of a certain section in the middle; The robot's spatial rotation angle: POB i-2 =cos -1 ((PV i-2 PV i-1 ) / (|PV i-2 ||PV i-1 |)) (5) Where: PV i-2 Indicates point P i-3 , P i-2 , P i-1 Determine the plane P i-3 P i-2 P i-1 Normal vector of i-1 Indicates point P i-2 , P i-1 , P i Determine the plane P i-2 P i-1 P i The normal vector, POB i-2 Indicates the spatial rotation angle; The adjustment value of the robot end effector in the Y-axis direction in the Cartesian coordinate system: Where: L i-1 Indicates the adjustment value in the Y-axis direction, DOB i-1 Indicates the bending angle, R i-1 Indicates the bending radius.

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