Quaternion joint-based rope-driven laser welding mechanical arm and control method

Abstract

The invention belongs to the technical field of mechanical arms, and discloses a rope-driven laser welding mechanical arm based on quaternion joints and a control method thereof.The rope-driven laser welding mechanical arm comprises an executing mechanism used for conducting laser welding operation, and the executing mechanism mainly comprises a laser welding head and an executing part connecting piece; the rigidity and the load capacity of the continuum structure can be enhanced through the quaternion joints, heavy execution components such as a laser welding head can be carried, and complex welding tasks which are difficult or impossible to be completed by a traditional robot in an unstructured environment with narrow working space and numerous obstacles can be completed. Quaternion joints are introduced on the basis of a continuum structure, the rigidity and the load capacity of the mechanical arm are enhanced on the basis that the flexibility of the mechanical arm is guaranteed, and heavy execution components such as a laser head can be carried; and complex operation tasks which are difficult or impossible to be completed by a traditional robot in an unstructured environment with a narrow working space and numerous obstacles can be completed.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical arms, and in particular relates to a rope-driven laser welding mechanical arm based on quaternion joints and a control method thereof. Background Art

[0002] Laser welding robots are industrial robots that specialize in laser welding operations. They have the advantages of high efficiency, intelligence, and environmental protection. They can stabilize welding quality, improve product qualification rate, and reduce the labor intensity of workers. They are the key to supporting high-quality, efficient, and intelligent manufacturing of high-end products and major equipment in the fields of machinery, ships, aerospace, rail transit, and automobiles.

[0003] With the development of technology, welding tasks gradually involve irregularly shaped workpieces, such as curves, curved pipes, hulls, etc., and the types of welds have gradually expanded from simple straight lines and arcs to complex spatial curves such as steel pipe intersection lines and shell surface intersection lines, which puts higher requirements on the flexibility and adaptability of the robot arm. Traditional rigid laser welding robots usually use multi-axis joints and connecting rod structures to perform welding tasks, and have become the main tools for automated welding. However, rigid laser welding robots usually require the workpiece to have a fixed position and orientation on the welding table, which limits their application to irregular or large workpieces and makes it difficult to cope with more complex welding environments and welding tasks.

[0004] In recent years, continuum robots have been increasingly valued in various fields due to their good compliance, good flexibility and human-machine safety, showing good application prospects. The motion body and actuator of the continuum robot are both composed of flexible parts, without rigid joints. The bendable part is composed of multiple bending segments with flexible structures, and the shape of the continuum robot is controlled by the deformation of the bending segments. The continuum robot can also install actuators at the end like traditional articulated robots, and can complete complex operation tasks that are difficult or impossible for traditional robots to complete in unstructured environments with small working spaces and many obstacles. It can more easily adapt to different welding tasks and workpiece shapes. However, at the same time, due to the continuum configuration, the robot body stiffness and load capacity are poor. As the end load increases, the control accuracy will gradually decrease. The application of continuum robots in the field of laser welding also puts higher requirements on their anti-interference ability and load capacity. Based on this, we propose a rope-driven laser welding robot arm based on quaternion joints and its control method.

[0005] Through the above analysis, the problems and defects of the prior art are as follows:

[0006] Existing laser welding robots have low welding freedom and poor environmental adaptability, making it difficult to meet the problems of complex welding conditions and complex trajectory welding; the existing continuum configuration body stiffness and load capacity are poor, and as the end load increases, the control accuracy will gradually decrease, which does not meet the requirements of industrial production. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a rope-driven laser welding robot arm based on quaternion joints and a control method thereof.

[0008] The present invention is implemented in that a rope-driven laser welding robot arm based on quaternion joints comprises:

[0009] An actuator, used for laser welding operation, the actuator mainly comprises a laser welding head and an actuator connecting piece;

[0010] The main body of the mechanical arm is used to carry the actuator, and can realize the movement of different trajectories, drive the actuator to complete the welding operation or reach the welding operation position. The main body of the mechanical arm includes an end plate, a spacer plate, a base plate, and a number of drive ropes, tension codes, connectors, connecting shafts, and support rods; the end plate, spacer plate, and base plate are collectively referred to as end plates;

[0011] The driving mechanism is used to control the movement of the robot arm body, and the driving mechanism includes a driving mechanism connecting piece, an adapter plate, a screw transmission mechanism, a power supply, and a terminal controller.

[0012] Furthermore, the screw transmission mechanism includes a motor, a screw, a linear guide rail, a coupling, a slider, and a drive rope fixing member.

[0013] Furthermore, the end plate, spacer plate, base plate, and drive mechanism connector all have a central through hole, and six wire holes are evenly distributed at equal intervals on the edge of the disk; three lifting ears are evenly distributed on the surface of one side of the end plate and the base plate, and the lifting ears are fixedly connected to the connecting shaft; there are lifting ears on both sides of the spacer plate, which are cross-distributed.

[0014] Furthermore, the main body of the mechanical arm has two joints, which are connected end to end through a spacer disk, and are joint one and joint two in sequence from the driving mechanism to the actuator; both ends of the support rod are fixedly connected to the connecting shaft; the support rod is connected to the end plate through a connecting piece, and the three support rods and the end plate together constitute a quaternion joint; the joint one is composed of a base plate, a spacer disk, and a quaternion joint; the joint two is composed of an end plate, a spacer disk, and a quaternion joint;

[0015] The driving mechanism connecting member is fixedly connected to the base plate.

[0016] Furthermore, the driving ropes can all pass through the wire holes and penetrate the joints, and are all connected to the driving rope fixing parts in the screw transmission mechanism through the driving mechanism connecting parts and the base plate; three evenly distributed driving ropes form a group, which are respectively used to drive the bending movement of the two joints, and are respectively the first driving rope group and the second driving rope group;

[0017] The first driving rope group passes through the base plate of the joint one, and the other end is fixedly connected to the spacer plate; the second driving rope group passes through the spacer plate, the base plate, and the driving mechanism connecting member, and the other end is fixedly connected to the end plate of the joint two.

[0018] Further, the screw transmission mechanism is fixedly connected to the driving mechanism connecting member through the adapter plate;

[0019] Among them, the motor is connected to the terminal controller, and the motor is connected to the screw through a coupling, driving the slider and the drive rope fixing part to complete linear motion, and finally driving the drive rope to complete the bending motion of the joint; the drive rope fixing part is fixedly connected to the slider.

[0020] Another object of the present invention is to provide a rope-driven laser welding robot control method based on quaternion joints, comprising:

[0021] Step 1: Calculate the change in the length of the driving rope when any joint angle is reached according to the driving formula;

[0022] Step 2, input the rope length change of each joint on the terminal controller;

[0023] Step 3, the controller drives the motor and drives the driving rope to complete linear motion;

[0024] Step 4: different drive ropes coordinate with each other to make the robot reach the corresponding position;

[0025] From the spatial geometric relationship, it can be obtained that the lengths of each driving rope in the bending plane satisfy the following relationship:

[0026]

[0027] Among them, l j is the length of the jth driving rope, ψ is the bending angle of the joint, and h is the vertical distance between the two end disks of the joint. During the bending process of the joint, this distance remains unchanged;

[0028] O0 point: the center point of the base plate;

[0029] Point O′: the intersection of the extended projection lines of the base plane and the end plane in the bending plane;

[0030] O'A j ': From point O' to point A in the bending planej ′The distance between points;

[0031] O′O0: the distance from point O′ to point O0 in the bending plane;

[0032] O0A j ′: From point O0 to point A in the bending plane j ′ point distance.

[0033] The following relationships can be obtained from spatial geometric relationships:

[0034]

[0035] Wherein, D is the distance between the fixed point of the driving rope on the end plate and the center of the end plate, α is the angle between the X0 axis of the coordinate system O0 and O0A1, is the angle between the X0 axis of the coordinate system O0 and the joint bending plane, j is the jth driving rope;

[0036] Based on the joint kinematic model, the change in the length of the driving rope when any joint angle is reached is calculated as follows:

[0037]

[0038] According to the driving formula, the change in the length of the driving rope when reaching any joint angle can be calculated, and the robot arm can reach any posture by controlling the change in the driving rope.

[0039] Another object of the present invention is to provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the rope-driven laser welding robot arm control method based on quaternion joints.

[0040] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, enables the processor to perform the steps of the rope-driven laser welding robot arm control method based on quaternion joints.

[0041] Another object of the present invention is to provide an information data processing terminal, which is used to implement the rope-driven laser welding robot arm based on quaternion joints.

[0042] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0043] First, the present invention is a rope-driven laser welding robot arm based on quaternion joints and a driving control method thereof, which has the following advantages:

[0044] Quaternion joints are introduced on the basis of continuum configuration, which enhances the stiffness and load capacity of the robot arm while ensuring its flexibility. It can carry heavy actuators such as laser heads, and can complete complex operation tasks that are difficult or impossible for traditional robots to complete in unstructured environments with small working spaces and many obstacles. There are channels in the middle of the joints, so that components such as optical fibers and wires can be built into the robot arm, avoiding mechanical failures or other safety problems caused by exposed wires during actual operation. The robot arm adopts rope drive, with three drive ropes for each joint, and each drive rope is controlled by a separate motor, which has a simple structure, while improving the stability of the drive and reducing the drive error. According to the structure, a drive control method is proposed to realize the movement of the robot arm in different positions, filling the gap in this technical field.

[0045] The purpose of the present invention is to provide a rope-driven laser welding robot arm based on quaternion joints and a driving control method thereof, which can enhance the stiffness and load capacity of the continuum configuration through quaternion joints, can carry heavy actuators such as laser welding heads, and can complete complex welding tasks that are difficult or impossible for traditional robots to complete in unstructured environments with narrow working spaces and numerous obstacles.

[0046] Quaternion joints are introduced on the basis of continuum configuration, which enhances the stiffness and load capacity of the robot arm while ensuring its flexibility. It can carry heavy actuators such as laser heads, and can complete complex operation tasks that are difficult or impossible for traditional robots to complete in unstructured environments with small working spaces and many obstacles. There are channels in the middle of the joints, so that components such as optical fibers and wires can be built into the robot arm, avoiding mechanical failures or other safety problems caused by exposed wires during actual operation. The robot arm adopts rope drive, with three drive ropes for each joint, and each drive rope is controlled by a separate motor, which has a simple structure, while improving the stability of the drive and reducing the drive error. According to the structure, a drive control method is proposed to realize the movement of the robot arm in different positions, filling the gap in this technical field.

[0047] Second, in actual production, most of the welding of complex workpieces is still done by manual welding by welders. The present invention can complete the welding of some complex workpieces, replace manual operations to a certain extent, improve production efficiency and yield rate, and reduce labor costs.

[0048] The present invention can replace the six-axis rigid welding robot on the domestic automated welding production line. By utilizing its multi-degree-of-freedom characteristics, it can complete the welding of multiple load workpieces and complex trajectories. A single robot can complete welding operations at multiple workstations, greatly improving the automation level and work efficiency of the welding production line and reducing production costs.

[0049] The introduction of quaternion joints based on the continuum configuration enhances the rigidity and load capacity of the robot arm while ensuring its flexibility. It can carry heavy actuators such as laser heads and complete complex operation tasks that are difficult or impossible for traditional robots to complete in unstructured environments with small working spaces and many obstacles, thus filling the technical gap in the field of high-load continuum laser welding robot arms.

[0050] In the present invention, a channel is provided in the middle of the joint, so that components such as optical fibers and wires can be built into the robotic arm, thereby avoiding mechanical failures or other safety problems caused by exposed wires during actual operation, and providing a new technical solution; for this structure, a drive control method is proposed to realize the movement of the robotic arm in different postures, filling the gap in this control technology field. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 1 is a schematic diagram of the overall structure of a rope-driven laser welding robot arm based on quaternion joints provided in an embodiment of the present invention;

[0052] Figure 2 It is a front view of the overall structure of a rope-driven laser welding robot arm based on quaternion joints provided by an embodiment of the present invention;

[0053] Figure 3 It is a top view of the overall structure of a rope-driven laser welding robot arm based on quaternion joints provided by an embodiment of the present invention;

[0054] Figure 4 It is a side view of the overall structure of a rope-driven laser welding robot arm based on quaternion joints provided by an embodiment of the present invention;

[0055] Figure 5 It is an overall schematic diagram of an actuator of a rope-driven laser welding robot arm based on quaternion joints provided in an embodiment of the present invention;

[0056] Figure 6 1 is an overall schematic diagram of a robot arm body of a rope-driven laser welding robot arm based on quaternion joints provided in an embodiment of the present invention;

[0057] Figure 7 It is a main front view of a robot arm of a rope-driven laser welding robot arm based on quaternion joints provided by an embodiment of the present invention;

[0058] Figure 8 It is a schematic diagram of the structure of the spacer disk of the rope-driven laser welding robot arm based on the quaternion joint provided by an embodiment of the present invention;

[0059] Fig. 9 It is a schematic structural diagram of the connection part between the end plate and the support rod of the rope-driven laser welding robot arm based on the quaternion joint provided by an embodiment of the present invention;

[0060] Fig.10 is a cross-sectional view of a joint of a rope-driven laser welding robot arm based on quaternion joints provided by an embodiment of the present invention;

[0061] Fig.11 is a cross-sectional view of a joint of a rope-driven laser welding robot arm based on quaternion joints provided by an embodiment of the present invention;

[0062] Fig.12 It is an overall schematic diagram of a driving mechanism of a rope-driven laser welding robot arm based on quaternion joints provided in an embodiment of the present invention;

[0063] Fig.13 It is an overall schematic diagram of a screw transmission mechanism of a rope-driven laser welding robot arm based on quaternion joints provided in an embodiment of the present invention;

[0064] Fig.14 This is a schematic diagram of an ideal spherical rolling motion model of a rope-driven laser welding manipulator based on quaternion joints provided in an embodiment of the present invention;

[0065] Fig.15 is a bending plane projection diagram of a rope-driven laser welding robot based on quaternion joints provided by an embodiment of the present invention;

[0066] Fig.16 is a bottom plane projection diagram of a rope-driven laser welding robot arm based on quaternion joints provided by an embodiment of the present invention;

[0067] Fig.17 It is a driving control flow chart of a rope-driven laser welding robot arm based on quaternion joints provided in an embodiment of the present invention;

[0068] Fig.18 is a general deformation diagram provided by an embodiment of the present invention;

[0069] Fig.19 is an equivalent stress diagram provided by an embodiment of the present invention;

[0070] Fig. 20 is a result diagram of total deformation and equivalent stress of a single joint under different loads provided by an embodiment of the present invention;

[0071] Fig.21 is a result diagram of total deformation and equivalent stress of double joints under different loads provided by an embodiment of the present invention;

[0072] Fig. 22 is a motion experiment posture diagram provided by an embodiment of the present invention;

[0073] Fig.23 is a diagram of a method for measuring joint angles in a motion experiment provided by an embodiment of the present invention;

[0074] In the figure: 1. actuator; 2. robot arm body; 3. drive mechanism; 4. laser welding head; 5. actuator connector; 6. end plate; 7. spacer plate; 8. base plate; 9. drive rope; 10. tension code; 11. support rod; 12. connecting shaft; 13. connector; 14. lifting ear; 15. joint one; 16. joint two; 17. first drive rope group; 18. second drive rope group; 19. drive mechanism connector; 20. adapter plate; 21. screw transmission mechanism; 22. screw; 23. slider; 24. drive rope fixing part; 25. coupling; 26. motor; 27. linear guide. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0076] like Figure 1 As shown, a rope-driven laser welding robot arm based on quaternion joints provided by an embodiment of the present invention includes:

[0077] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the rope-driven laser welding robot arm based on quaternion joints of the present invention comprises three parts: an actuator 1, a robot arm body 2, and a driving mechanism 3;

[0078] like Figure 5 As shown, the actuator 1 mainly includes a laser welding head 4 and an actuator connecting part 5, which are used for laser welding operations; the actuator connecting part 5 is used to connect the actuator 1 and the robot arm body 2, and can accommodate wires to pass through; the laser welding head 4 can be any laser welding head on the market, and what is described in the present invention and shown in the figures are only examples for explaining the structural principles of the present invention.

[0079] The rope-driven laser welding robot based on quaternion joints described in the embodiment of the present invention is composed of three parts: an actuator 1, a robot body 2 and a driving mechanism 3 (such as Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown in the figure, the robot body 2 adopts a quaternion joint design, which can achieve precise posture adjustment in space; the driving mechanism 3 uses a rope drive method to efficiently drive each joint of the robot body 2; and the actuator 1 is installed at the end of the robot body 2 and is responsible for completing the laser welding operation.

[0080] The actuator 1 is mainly composed of a laser welding head 4 and an actuator connecting piece 5 (see Figure 5 ). The laser welding head 4 can be any mature product on the market, and its function is to output a stable and high-energy laser beam to achieve the welding task; the execution part connector 5 is used to firmly connect the laser welding head 4 to the robot arm body 2, and a wire channel is reserved to ensure the stability of power and signal transmission during the welding process, thereby ensuring the welding quality.

[0081] The robot body 2 is based on quaternion joint design, which overcomes the universal joint lock problem that may occur in traditional joints and realizes smooth and flexible spatial movement; the drive mechanism 3 adopts rope drive mode, and drives the joints of the robot body 2 by precisely adjusting the tension of the rope, so as to achieve precise positioning. The cooperation between the two ensures the high responsiveness and accuracy of the robot arm during movement, meeting the strict requirements of laser welding on position and posture.

[0082] During the welding process, the controller generates control instructions for each joint according to the preset welding path and process requirements, and transmits them to the FPGA through the processor. The drive mechanism 3 then adjusts the rope tension according to these instructions to achieve real-time posture adjustment of the robot body 2. At the same time, the laser welding head 4 in the actuator 1 outputs the laser beam according to the controller instructions and performs welding along the predetermined trajectory. The entire system forms a virtual-real interactive closed loop, collects sensor data feedback in real time, and dynamically updates the motor and joint status, thereby ensuring high precision and high stability of the welding process.

[0083] like Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.10 , Fig.11 As shown, the robot arm body 2 includes an end plate 6, a spacer plate 7, a base plate 8, a plurality of drive ropes 9, a tension code 10, a support rod 11, a connecting shaft 12 and a connecting piece 13; the end plate 6, the spacer plate 7 and the base plate 8 can be collectively referred to as an end plate; the robot arm body 2 is used to carry the actuator, which can realize the movement of different trajectories and drive the actuator 1 to complete the welding operation or reach the welding operation position;

[0084] Specifically, the robot body 2 has two joints, which are connected end to end through a spacer disk 7, and from the driving mechanism to the actuator, they are joint one 15 and joint two 16;

[0085] The end plate 6, the spacer plate 7, the base plate 8, and the drive mechanism connector 19 all have a central through hole, and six wire holes are evenly distributed at equal intervals on the edge of the disk; three ears 14 are evenly distributed on one side of the end plate 6 and the base plate 8, and the ears 14 are fixedly connected to the connecting shaft 12; Figure 8 As shown, the lifting ears 14 are distributed on both sides of the spacer plate 7 in a cross-distribution; both ends of the support rod 11 are fixedly connected to the connecting shaft 12; Fig. 9 As shown, the support rod 11 is connected to the end plate through a connecting piece 13, and the two connecting shafts 12 pass through the two through holes of the connecting piece 13 respectively, and the axes of the two through holes of the connecting piece 13 are perpendicular to each other; the three support rods 11, the connecting shaft 12 and the connecting piece 13 together with the two end plates constitute the quaternion joint; the joint 14 is composed of a base plate 6, a spacer plate 7, a support rod 11, a connecting shaft 12 and a connecting piece 13; the joint 2 16 is composed of a spacer plate 7, an end plate 8, a support rod 11, a connecting shaft 12 and a connecting piece 13; the quaternion joint can perform approximate spherical rolling in three-dimensional space, thereby ensuring the motion stability of the continuum configuration without a central main rod under high load, and improving the load capacity and stiffness of the continuum configuration.

[0086] like Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.10 , Fig.11 As shown, the robot body 2 is composed of an end plate 6, a spacer plate 7 and a base plate 8 (collectively referred to as an end plate), and is also equipped with a number of drive ropes 9, tension codes 10, support rods 11, connecting shafts 12 and connectors 13. The body is used to carry the actuator 1 and realize the movement of different trajectories through its own structure, thereby driving the actuator 1 to complete the welding operation or reach the specified welding position. The design of the entire system ensures that the movement stability and high-precision positioning can be maintained under high load.

[0087] The end plate 6, the spacer plate 7, the base plate 8 and the drive mechanism connector 19 are all designed with a central through hole, and six wire holes are evenly distributed at equal intervals on the edge of the disk, which is convenient for laying the drive rope 9 and achieving uniform force transmission. At the same time, three lifting ears 14 are evenly distributed on one side of the end plate 6 and the base plate 8, and are also cross-distributed on both sides of the spacer plate 7. These lifting ears 14 are rigidly connected to the connecting shaft 12 through fixed connection, providing key load-bearing nodes for subsequent joint structures.

[0088] Both ends of the support rod 11 are fixedly connected to the connecting shaft 12 and connected to the end plate through the connecting piece 13. Fig. 9 As shown, the two connecting shafts 12 pass through two mutually perpendicular through holes on the connecting member 13, respectively, to ensure that the connecting member 13 can accurately transmit motion and load under the action of the support rod 11. The three support rods 11, the connecting shafts 12, the connecting member 13 and the end plate together constitute the basic structural unit of the quaternion joint, providing the necessary rigidity and stability for the entire robotic arm.

[0089] The robot body 2 is provided with two joints, namely, joint 1 15 (composed of base plate 6, spacer plate 7, support rod 11, connecting shaft 12 and connecting member 13) and joint 2 16 (composed of spacer plate 7, end plate 8, support rod 11, connecting shaft 12 and connecting member 13). The quaternion joint can realize rolling motion of a spherical surface in three-dimensional space, ensuring high load capacity and motion stability in the continuum configuration without a central main rod. This design not only improves the load capacity and stiffness of the continuum configuration, but also meets the stringent requirements of laser welding operation for high precision and stability.

[0090] like Figure 6 As shown, the driving ropes 9 can all pass through the wire holes and penetrate the joints, and are all connected to the driving rope fixing member 24 in the screw transmission mechanism 21 through the driving mechanism connecting member 5 and the base plate 8; three evenly distributed driving ropes form a group, which are respectively used to drive the bending movement of the two joints, and are respectively a first driving rope group 17 and a second driving rope group 18;

[0091] Specifically, Fig.10 As shown, the joint 15 has six driving ropes 9 of the first driving rope group 17 and the second driving rope group 18 passing through, the wire holes of the six driving ropes 9 are evenly distributed, and the axis of the three wire holes and the axis of the central through hole of the base plate 8 form an angle of 60°; one end of the three driving ropes of the first driving rope group 17 is fixedly connected to the tension code 10 of the base plate 7, and the other end is fixedly connected to the driving rope fixing member 24 of the screw transmission mechanism 21; the first driving rope group 17 can control the joint 15 to realize two-degree-of-freedom bending motion;

[0092] like Fig.11 As shown, the joint 2 16 has three driving ropes 9 of the second driving rope group 18 passing through, the wire holes of the three driving ropes 9 are evenly distributed, and the axis of the three wire holes and the axis of the central through hole of the spacer disk 7 form an angle of 120°; three tension weights 10 are evenly distributed on the spacer disk 7, which are used to fix the driving ropes of the first driving rope group 17; the axes of the driving rope 9 of the joint 2 16 and the tension weight 10 are on the same circle and concentric with the central through hole;

[0093] The second driving rope group 18 only passes through the joint 15, and does not affect the control of the joint 15 by the first driving rope group 17, so that the motion control of the two joints can be independent of each other;

[0094] like Fig.12 , Fig.13As shown, the driving mechanism 3 includes a driving mechanism connecting member 19, an adapter plate 20, a screw transmission mechanism 21, a power supply and a terminal controller, which are used to control the movement of the robot arm body 2; the driving mechanism connecting member 19 is fixedly connected to the base plate 8; the screw transmission mechanism 21 includes a screw 22, a slider 23, a driving rope fixing member 24, a coupling 25, a motor 26, and a linear guide rail 27; the driving rope fixing member 24 is fixedly connected to the slider 23;

[0095] Specifically, Fig.12 As shown, the screw transmission mechanism 21 is fixedly connected to the drive mechanism connecting member 19 through the adapter plate 20, and is evenly spaced around the central axis of the drive mechanism connecting member 19; each joint is controlled by three of the screw transmission mechanisms, and the motor 26 is connected to the terminal controller, and the motor 26 is connected to the screw 22 through a coupling 25, which converts the rotation of the motor into linear motion, drives the slider 23 and the drive rope fixing member 24 to complete the linear motion, and finally drives the drive rope 9 to complete the bending motion of the joint.

[0096] The rope-driven laser welding robot based on quaternion joints of the present invention adopts a new type of continuum configuration robot design, and controls the retraction and extension of multiple driving ropes through a driving mechanism to realize the flexible movement of the robot. The main body of the robot is composed of an end disk, a spacer disk and a base disk. The quaternion joints are formed between the disks through support rods and connecting shafts, so that it can realize approximately spherical rolling motion in three-dimensional space. The driving mechanism is installed on the base disk of the robot, and is composed of a motor, a screw transmission mechanism, a slider, a linear guide rail and a driving rope fixing. The driving rope is connected to the screw transmission mechanism. By controlling the rotation of the motor to drive the movement of the screw, the slider moves along the linear guide rail, thereby adjusting the tension of the driving rope, and finally controlling the joint movement of the robot to achieve precise positioning of the laser welding head.

[0097] In this system, the realization of quaternion joints depends on the connection method between multiple end plates. The edges of the base plate, the spacer plate and the end plate are evenly distributed with wire holes for driving ropes to pass through and connect each joint structure. The first driving rope group and the second driving rope group are used to control the movement of joint one and joint two respectively, wherein each driving rope group contains three driving ropes, which are fixed on the base plate and the spacer plate respectively. The first driving rope group is responsible for the two-degree-of-freedom movement of joint one, while the second driving rope group only passes through joint one and does not affect its movement, thereby realizing independent control of the two joints. This design ensures that the robot arm still has a high load capacity without a central main rod, and maintains the stability of movement through precise force transmission.

[0098] The screw transmission mechanism of the drive mechanism is distributed on the drive mechanism connector at equal intervals, and each joint is independently controlled by three screw transmission mechanisms. The motor drives the screw to rotate through the coupling, so that the slider moves along the linear guide rail and drives the drive rope fixing to retract and release the drive rope, thereby changing the joint angle and achieving bending movement. Due to the high linear motion accuracy of the screw, this driving method can ensure the movement accuracy of the robot arm. In order to further optimize the force condition of the robot arm, the axis of the through hole of the drive rope and the axis of the central through hole of the end plate are arranged at a specific angle, so that the rope force distribution is more uniform, the force transmission efficiency is improved, and the overall stability of the system is enhanced.

[0099] During the operation of the robot arm, the terminal controller calculates the required joint motion trajectory according to the requirements of the welding task, and adjusts the length of the drive rope through the motor-driven lead screw to achieve the required posture. Through the coordinated control of the three drive ropes, the position of the welding head can be accurately adjusted in three-dimensional space so that it can perform welding operations according to the set trajectory. In addition, the structural design of the system enables the robot arm to adapt to different welding environments, especially for complex welding tasks that require high flexibility and high precision operations. At the same time, due to the use of rope drive, the robot arm has a lighter weight and higher energy efficiency than traditional rigid robot arms, thereby improving the overall efficiency of welding work.

[0100] According to the present invention, a driving control method of a rope-driven laser welding robot arm based on quaternion joints is proposed.

[0101] The rope-driven laser welding robot control method based on quaternion joints of the present invention relies on the joint kinematic model, and realizes precise control of the robot movement by calculating the change in the length of the driving rope. In the control process, the target posture of the robot is first determined, and a mathematical model of the joint is established based on the spatial geometric relationship. The mathematical model calculates the change in the length of the driving rope based on the joint angle of the robot, the geometric parameters of the end plate and the fixed point distribution of the driving rope. Through the motion relationship between the driving rope and the joint, the trajectory of the robot in three-dimensional space can be accurately controlled to meet the needs of welding operations.

[0102] During the control execution process, the terminal controller inputs the change in the length of the drive rope calculated by the joint kinematic model into the control system according to the setting of the target posture. After the controller receives the input parameters, the drive motor drives the screw transmission mechanism to move the slider along the linear guide rail, thereby driving the drive rope to complete the corresponding length adjustment. Since the drive rope is fixed to the end plate, when its length changes, the corresponding joint will bend around its rotation center. Different drive rope combinations work together to enable the joint to achieve high-precision adjustment along the preset direction, ensuring that the laser welding head moves along the set trajectory.

[0103] During the movement of the robot arm, the bending angle of the joint and the change in the length of the drive rope meet a specific geometric constraint relationship. Based on the spatial geometric relationship, the calculation formula for the length change of the drive rope in the joint bending plane can be derived, where the joint angle, the vertical distance between the end disks, the distance from the fixed point of the drive rope to the center of the end disk and other parameters jointly determine the stretching or contraction of the drive rope. The terminal controller calculates the actual adjustment value of each drive rope based on these parameters, and adjusts the control signal of the motor in real time to ensure that the retraction and extension of the drive rope meet the expected changes, so that the robot arm moves smoothly according to the target trajectory.

[0104] The entire control process is based on joint kinematic calculations and precise control of the drive rope, allowing the robot arm to efficiently and stably achieve complex welding motion trajectories. Due to the flexible characteristics of the rope drive method, the robot arm can maintain precise motion stability under high loads, while having good seismic resistance and energy consumption optimization capabilities. In addition, the control method can adapt to different welding conditions by adjusting the drive parameters, and can be combined with the sensor feedback mechanism to further optimize motion control and improve the accuracy and reliability of welding operations. The present invention mainly relies on the coordinated motion of the drive rope to control the bending of the robot arm. First, it is necessary to determine the change in the length of the drive rope at any joint angle of the robot arm;

[0105] like Fig.14 As shown, a single joint of the robotic arm can perform approximately spherical rolling in three-dimensional space, and an ideal spherical rolling motion model can be established;

[0106] Specifically, the center of the base circle is taken as the origin of the spatial coordinate system O0, and the spatial coordinate system O0 coordinate system is established; the center of the end circle is taken as the origin of the spatial coordinate system O e , establish the space coordinate system O e Coordinate system; the Z0 axis of the coordinate system O0 is perpendicular to the base plane, and the Y0 axis is in the bending plane of the joint; the coordinate system O e Z e Axis perpendicular to the end plane, Y e The axis is in the plane of flexion of the joint;

[0107] like Fig.15 , Fig.16 As shown, the projection views of the ideal spherical rolling motion model in the joint bending plane and the base plane are obtained;

[0108] like Fig.15 As shown, from the spatial geometric relationship, it can be obtained that the lengths of each driving rope in the bending plane satisfy the following relationship:

[0109]

[0110] Among them, l jis the length of the jth driving rope, ψ is the bending angle of the joint, and h is the vertical distance between the two end disks of the joint. During the bending process of the joint, this distance remains unchanged;

[0111] like Fig.16 As shown, the following relationship can be obtained from the spatial geometric relationship:

[0112]

[0113] Wherein, D is the distance between the fixed point of the driving rope on the end plate and the center of the end plate, α is the angle between the X0 axis of the coordinate system O0 and O0A1, is the angle between the X0 axis of the coordinate system O0 and the joint bending plane, j is the jth driving rope;

[0114] Based on the joint kinematic model, the change in the length of the driving rope when any joint angle is reached is calculated as follows:

[0115]

[0116] like Fig.17 As shown, according to the driving formula, the change in the length of the driving rope when reaching any joint angle can be calculated, and the change in the length of the rope of each joint can be input into the terminal controller; each driving rope 9 is controlled by a separate motor 26; the controller drives the motor 26 and drives the driving rope 9 to complete linear motion at the same time; different driving ropes 9 coordinate with each other to make the robot reach the corresponding posture.

[0117] The present invention proposes a control method for a rope-driven laser welding robot based on quaternion joints. First, the driving rope length change of each joint at any angle is calculated by the driving formula. The mathematical model of the quaternion joint can accurately describe any rotation and posture of the robot in three-dimensional space, so that it can adapt to complex motion trajectories. Through calculation, the driving rope length change required for each joint is obtained, providing an accurate parameter basis for subsequent control.

[0118] Through the terminal controller, the user inputs the calculated rope length changes of each joint into the control system. The terminal controller has a human-computer interaction interface that can monitor the accuracy of input parameters in real time and ensure that the target length of each drive rope matches the posture of the robot arm. This step effectively reduces the complexity of manual adjustment and improves control efficiency.

[0119] The built-in processor of the control system drives multiple motors to work synchronously according to the input rope length change data. Each drive rope is controlled by an independent motor. The precise rotation of the motor enables the drive rope to complete position adjustment in the form of linear motion, thereby ensuring the stability and response speed of the robot arm.

[0120] Each joint of the robot arm is controlled by three independent drive ropes, and the drive ropes are coordinated through control algorithms to ensure that the robot arm can accurately adjust to the target position in three-dimensional space. The multi-drive rope cooperation mechanism improves the flexibility of the robot arm, enabling it to cope with complex operation tasks in unstructured environments.

[0121] Compared with traditional robotic arms, the present invention significantly improves the rigidity and load capacity while enhancing the flexibility of the robotic arm by introducing quaternion joints. This design allows the robotic arm to carry heavier actuators such as laser heads, and can complete complex welding tasks in narrow spaces or environments with many obstacles, expanding more possibilities for robot applications.

[0122] Each quaternion joint is designed as a hollow structure, allowing components such as optical fibers and wires to be built into the robot arm. Compared with the design of exposed wires in traditional robot arms, the present invention effectively avoids mechanical failures or safety issues caused by exposed wires, thereby significantly improving the reliability and operational safety of the equipment.

[0123] The present invention adopts rope drive mode, each joint is equipped with three independent drive ropes, which are controlled by a separate motor. The drive system structure is simple and easy to maintain. Compared with complex gear or hydraulic drive, rope drive mode can effectively reduce system error and improve the stability and response speed during the drive process.

[0124] The control method of the present invention is applicable to the design of manipulators with different numbers of joints, drive ropes and motors. Users can flexibly increase or decrease the number of joints or drive rope configurations according to specific application requirements, thereby realizing the design of manipulators with different motion spaces and functions. This flexibility not only expands the scope of application of the manipulator, but also fills the gap in the current field of laser welding manipulator control technology.

[0125] Simulate the load capacity of single and double joints of the robot arm to analyze the joint load deformation under gravity field and load conditions. The gravity is set to 9806.6mm / s 2 , the end load is set to 50 / 100 / 150 / 200N. The material settings of each part of the robot arm joint are shown in the following table.

[0126] Table material settings

[0127]

[0128] Fig.18 Total deformation;

[0129] Fig.19 Equivalent stress;

[0130] Fig. 20 Result diagram of total deformation and equivalent stress of a single joint under different loads;

[0131] Fig.21 Results of total deformation and equivalent stress of double joints under different loads;

[0132] Under the combined effect of gravity and 200N load, the maximum deformation of a single joint is 0.5mm. The deformation is concentrated in the end plate and the drive rope. The maximum equivalent stress is 388.76MPa. The stress is concentrated in the support rod, shaft and drive rope.

[0133] Under the combined effect of gravity and a 200N load, the maximum deformation of the double joints is 0.98mm, and the maximum equivalent stress is 272.82MPa. The deformation is concentrated on the end plate and the drive rope, and the stress is concentrated on the support rod and the drive rope. The overall deformation of the robotic arm is small under high load, meeting actual work needs.

[0134] 1. Joint posture experimental plan

[0135] like Fig. 22 , set the three postures of the robotic arm, calculate the control parameters of the robotic arm in these three postures through the driving formula, and verify the execution accuracy of the robotic arm mechanism and the accuracy of the control formula by comparing the error between the actual angle and the theoretical angle.

[0136] Robot arm posture parameters

[0137]

[0138]

[0139] 2. Joint angle measurement methods, such as Fig.23 ;

[0140] Before measurement, each joint reference plane needs to be calibrated. The calculation formula for the robot arm joint posture motion error is:

[0141]

[0142] The angle between the reference plane and the horizontal ground is the calibration angle The angle between the reference plane and the end surface of the joint is the joint angle θ i , the theoretical angle of joint i is θ i 0

[0143] Joint reference plane calibration angle

[0144]

[0145] 3. Experimental results

[0146] The results of the drive control experiment are shown in the following table. The average error of joint 1 is 0.97%, the average error of joint 2 is 0.57%, and the average error of the robot arm as a whole is 0.42%. The execution accuracy of the robot arm mechanism meets the work requirements, verifying the correctness of the drive formula.

[0147] Drive control experimental results

[0148]

[0149]

[0150] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A rope-driven laser welding robot based on quaternion joints, characterized in that: It includes an actuator, a robot arm body and a driving mechanism; The actuator is mounted on the end plate of the robot body and is used to connect the laser welding head; The mechanical arm body is connected to the end plate and the base plate through a spacer plate, and includes a plurality of driving ropes, support rods and connecting shafts; The driving mechanism is installed on the base plate of the mechanical arm body through a driving mechanism connecting piece and is connected with the driving rope.

2. The rope-driven laser welding robot based on quaternion joints according to claim 1, characterized in that: The end plate, the spacer plate and the base plate in the main body of the mechanical arm form a quaternion joint through a support rod and a connecting shaft. The edges of the disks of the end plate, the spacer plate and the base plate are provided with wire holes at equal intervals for driving ropes to pass through.

3. The rope-driven laser welding robot based on quaternion joints according to claim 1, characterized in that: The driving mechanism is fixedly connected to the driving mechanism connecting piece through an adapter plate. The driving mechanism comprises a motor, a lead screw, a coupling, a slider, a linear guide rail and a driving rope fixing piece. The slider is assembled with the driving rope fixing piece.

4. The rope-driven laser welding robot based on quaternion joints according to claim 1, characterized in that: The driving rope passes through the joint one through the wire hole on the base plate and is fixed on the spacer plate; another set of driving ropes passes through the joint two through the wire hole on the spacer plate and is fixed on the end plate.

5. The rope-driven laser welding robot based on quaternion joints according to claim 1, characterized in that: A through hole is arranged in the center of the end plate, the spacer plate and the base plate, and the optical fiber and the wire pass through the entire robot arm body through the central through hole and avoid crossing with the driving rope.

6. The rope-driven laser welding robot based on quaternion joints according to claim 1, characterized in that: The two ends of the support rod are respectively assembled to the end plate and the spacer plate through the connecting shaft, and the three support rods are evenly distributed at equal angles to form the joints of the robot arm body.

7. The rope-driven laser welding robot based on quaternion joints according to claim 1, characterized in that: The driving mechanism is fixedly connected to the base plate, and the two ends of the driving rope are respectively fixed between the driving mechanism and the end plate. The slider is driven to move through the screw transmission mechanism, so that the driving rope completes the bending action of each joint of the robot arm.

8. A control method for a rope-driven laser welding robot arm based on quaternion joints implementing the robot arm as claimed in any one of claims 1 to 7, characterized in that: The rope-driven laser welding robot control method based on quaternion joints comprises: Step 1: Calculate the change in the length of the driving rope when any joint angle is reached according to the driving formula; Step 2, input the rope length change of each joint on the terminal controller; Step 3, the controller drives the motor and drives the driving rope to complete linear motion; Step 4: different drive ropes coordinate with each other to make the robot reach the corresponding position; From the spatial geometric relationship, it can be obtained that the lengths of each driving rope in the bending plane satisfy the following relationship: Among them, l j is the length of the jth driving rope, ψ is the bending angle of the joint, and h is the vertical distance between the two end disks of the joint. During the bending process of the joint, this distance remains unchanged; The following relationships can be obtained from spatial geometric relationships: Wherein, D is the distance between the fixed point of the driving rope on the end plate and the center of the end plate, α is the angle between the X0 axis of the coordinate system O0 and O0A1, is the angle between the X0 axis of the coordinate system O0 and the joint bending plane, j is the jth driving rope; Based on the joint kinematic model, the change in the length of the driving rope when any joint angle is reached is calculated as follows: According to the driving formula, the change in the length of the driving rope when reaching any joint angle can be calculated, and the robot arm can reach any posture by controlling the change in the driving rope.

9. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the control method of a cable-driven laser welding robot based on quaternion joints as claimed in claim 7.

10. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the rope-driven laser welding robot arm based on quaternion joints as described in any one of claims 1-6.

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