Multi-degree-of-freedom mechanical arm assembled through frame butt joint

Abstract

The application provides a multi-freedom mechanical arm for frame butt joint assembly, and belongs to the field of mechanical hands, comprising a fixed bearing platform, a multi-joint mechanical arm main body, a butt joint tool and a multi-dimensional compliant butt joint unit arranged in series between the two. The unit comprises an upper connecting disc fixedly connected with the distal end of the mechanical arm, a lower floating disc fixedly connected with the butt joint tool, an elastic compliance assembly arranged between the two discs, and a locking assembly. The elastic compliance assembly provides axial and radial elastic support, so that the lower floating disc can passively comply with movement to compensate for butt joint errors; the locking assembly locks the two discs when the axial compression displacement exceeds the threshold value, switching to rigid connection. Through the rigid and flexible dual-mode switching mechanism, the application takes into account the compliant guidance and error compensation at the initial stage of assembly, as well as the rigid stability of subsequent assembly, significantly improving the precision and reliability of the automatic butt joint of the frame.

Description

Technical Field

[0001] This invention relates to the field of robotic arms, and more specifically, to a multi-degree-of-freedom robotic arm for chassis docking and assembly. Background Technology

[0002] In modern manufacturing, the chassis serves as the core framework for products such as electric vehicles and automobiles, and its welding and assembly is a crucial step in the production process. With the development of industrial automation technology, the automated docking and assembly of chassis using multi-degree-of-freedom robotic arms has become a mainstream trend. However, in actual production, due to limitations in the absolute positioning accuracy of the robotic arm itself, as well as the unavoidable manufacturing tolerances generated during the stamping and forming processes of the chassis workpiece, it is often difficult to achieve perfect theoretical alignment between the end effector of the robotic arm and the chassis interface.

[0003] Existing docking and assembly equipment mostly employs a rigid connection method, where the docking fixture is directly and rigidly fixed to the end of the robotic arm. This rigid structure lacks the necessary adaptive adjustment capability when faced with the aforementioned positional and posture errors. When the robotic arm forcibly pushes the chassis into the docking position, it is highly susceptible to rigid collisions at the workpiece contact surfaces due to alignment deviations, leading to problems such as jamming, workpiece surface scratches, or even equipment overload damage. Although some existing technologies have introduced vision guidance systems to correct the robotic arm trajectory, vision systems cannot completely eliminate the small cumulative errors during dynamic assembly and cannot solve the force control and buffering problem at the moment of contact. Therefore, developing a chassis docking and assembly robotic arm that can have compliant floating capability to compensate for errors in the early stages of assembly, while maintaining high rigidity to ensure assembly stability after assembly, has become an urgent technical challenge to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-degree-of-freedom robotic arm for vehicle frame docking and assembly, which aims to solve the problems mentioned in the background art.

[0005] This invention is implemented as follows: a multi-degree-of-freedom robotic arm for vehicle frame docking and assembly includes a fixed platform, a multi-joint robotic arm body mounted on the fixed platform, and a docking fixture mounted on the distal end of the multi-joint robotic arm body, and further includes: A multi-dimensional compliant docking unit is connected in series between the far end of the multi-joint robotic arm body and the docking fixture; The multidimensional compliant docking unit includes: The upper connecting plate is fixedly connected to the far end of the multi-joint robotic arm body; The lower floating plate is fixedly connected to the docking fixture. An elastic compliant assembly, disposed between the upper connecting plate and the lower floating plate, provides axial elastic support and radial elastic shear support, enabling the lower floating plate to passively compliantly align with the upper connecting plate in an unlocked state, allowing for axial and radial translational movements. A locking assembly is installed between the upper connecting plate and the lower floating plate; When the lower floating plate is subjected to the reaction force of the frame component in the assembly direction and generates an axial compression displacement exceeding a preset threshold relative to the upper connecting plate, the locking assembly mechanically locks the lower floating plate and the upper connecting plate in the axial and radial degrees of freedom, so that the two switch from a relatively floating compliant state to a rigid connection state.

[0006] Optionally, the resilient compliant component includes: The guide rod, the upper end of which is fixedly connected to the upper connecting plate; A positioning cylinder is slidably sleeved on the outside of the guide rod, and a radial elastic bushing is provided between the positioning cylinder and the lower floating plate to provide radial elastic shear support; and An axial elastic element is sleeved on the guide rod and abuts against the upper connecting plate and the positioning cylinder or the lower floating plate to provide axial elastic support.

[0007] Optionally, the outer side of the lower floating disk is provided with a movable through hole, the positioning cylinder is provided inside the movable through hole, the radial elastic bushing is sleeved and fixed on the upper part of the positioning cylinder, and the outer wall of the radial elastic bushing is engaged and connected with the fitting groove opened in the lower floating disk. The lower end of the guide rod passes through the positioning cylinder and is threadedly connected to an adjusting nut. An anti-detachment disc is provided on the upper side of the adjusting nut, and the outer diameter of the anti-detachment disc is larger than the lower diameter of the movable through hole.

[0008] Optionally, the locking component includes: The central cylinder is fixed to the lower side of the upper connecting plate; A central column is fixed to the upper side of the lower floating disk, and the diameter of the central column is smaller than the inner diameter of the lower end of the central cylinder; An adapter plate is slidably disposed on the inner side of the central cylinder and slidably connected to the central column; The brake pin is slidably mounted on the outside of the adapter plate along the axial direction; A radial fixing pin is slidably installed on the inner side of the adapter plate to abut against the central cylinder to restrict the radial movement of the adapter plate; An axial fixing pin, slidably mounted on the inner side of the adapter plate, is used to abut against the central post to restrict the axial movement of the adapter plate; and A brake telescopic cylinder, fixed to the upper connecting plate, has its output end used to push the brake pin to slide, thereby driving the radial fixing pin and the axial fixing pin to extend simultaneously.

[0009] Optionally, a reset elastic element is installed between the brake pin and the adapter plate; when there is no external force, the reset elastic element is used to drive the brake pin to reset, so as to release the locking state of the radial fixing pin and the axial fixing pin. The lower end of the brake pin is provided with two opposing tapered inclined surfaces. The upper end of the radial fixing pin is engaged with one of the tapered inclined surfaces, and the outer end of the axial fixing pin is engaged with the other tapered inclined surface.

[0010] Optionally, the docking fixture includes: The support frame is fixed to the lower floating plate; A load-bearing support tube is rotatably installed on the lower part of the support frame, and a U-shaped frame is fixed at one end of the load-bearing support tube; A telescopic clamping cylinder is fixed in the middle of the U-shaped frame, and a trapezoidal block is fixed at its output end; Two clamping frames are slidably mounted on the U-shaped frame and are located on both sides of the trapezoidal block, respectively, for moving closer or further apart under the drive of the clamping telescopic cylinder to clamp or release the frame components.

[0011] Optionally, the trapezoidal block has an isosceles trapezoidal shape, and anti-detachment posts are fixedly fitted on the two sides of the trapezoidal block, and the two clamping frames are slidably engaged with the corresponding anti-detachment posts; A connecting arm is fixed between the ends of the two branches of the U-shaped frame, and both clamping frames are slidably connected to the connecting arm. The end of the clamping frame is threaded with multiple adjusting bolts, and the end of each adjusting bolt is rotatably connected to a clamping plate, on which an elastic pad is fixed.

[0012] Optionally, the docking fixture further includes: The worm gear is mounted and fixed on the bearing support tube; The worm gear meshes with the worm wheel; and The motor is fixed on the support frame, and its output end is connected to the worm gear transmission to drive the load-bearing support tube and the U-shaped frame to rotate around its own axis.

[0013] Optionally, the main body of the multi-joint robotic arm is a six-degree-of-freedom serial joint type industrial robotic arm, and its distal wrist is directly and rigidly connected to the upper connecting plate of the multi-dimensional compliant docking unit through a flange. A laser sensor is installed on the upper connecting plate to measure the axial distance between the upper connecting plate and the lower floating plate in real time, so as to monitor whether the axial compression displacement exceeds the preset threshold.

[0014] Another object of the present invention is a frame docking and assembly method, applied to the aforementioned multi-degree-of-freedom robotic arm, comprising the following steps: S1. The multi-joint robotic arm moves the multi-dimensional compliant docking unit and docking fixture to the location of the frame component. At this time, the lower floating plate of the multi-dimensional compliant docking unit is in an unlocked compliant state. S2. The frame component is clamped using the docking fixture, and the frame component is moved closer to the frame body by the multi-joint robotic arm. S3. During the contact process between the frame sub-component and the frame body, the axial elastic support and radial elastic shear support provided by the elastic compliant component are used to make the lower floating plate perform passive compliant motion of axial translation and / or radial translation relative to the upper connecting plate to compensate for position and attitude errors. S4. When the axial compression displacement of the lower floating disk relative to the upper connecting disk exceeds a preset threshold, the locking component is activated to mechanically lock the lower floating disk and the upper connecting disk in axial and radial degrees of freedom, so that the two switch from a relatively floating compliant state to a rigid connection state. S5. In the rigid connection state, the subsequent assembly operation is performed by the multi-joint robotic arm body.

[0015] The multi-degree-of-freedom robotic arm for vehicle frame docking and assembly provided by this invention has the following beneficial effects: By connecting a multi-dimensional compliant docking unit in series between the end effector of the robotic arm and the docking fixture, the end effector is given passive floating capability in the axial and radial directions by the elastic compliant component. This effectively compensates for the absolute positioning error of the robotic arm and the manufacturing tolerance of the chassis workpiece, avoiding jamming or damage caused by rigid contact. At the same time, with the locking component, the floating state can be automatically switched to the rigid locking state when the docking reaction force reaches the preset threshold. This ensures both compliant guidance and accurate alignment in the early stage of assembly, and ensures the overall rigidity and stability of the connection structure in subsequent assembly operations, significantly improving the accuracy and reliability of automated chassis docking assembly.

[0016] In summary, this invention, through a rigid-flexible dual-mode switching mechanism, balances compliant guidance and error compensation in the initial stage of assembly with rigid stability in subsequent assembly, significantly improving the accuracy and reliability of automated chassis docking.

[0017] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0019] Figure 1 A three-dimensional structural schematic diagram of a multi-degree-of-freedom robotic arm for chassis docking and assembly provided in an embodiment of the present invention; Figure 2 A three-dimensional structural diagram of the multi-dimensional compliant docking unit and docking tooling in the multi-degree-of-freedom robotic arm for chassis docking assembly provided in an embodiment of the present invention; Figure 3 for Figure 2 Another perspective structural diagram; Figure 4 An isometric view of the multidimensional compliant docking unit in the multi-degree-of-freedom robotic arm for chassis docking assembly provided in an embodiment of the present invention; Figure 5 for Figure 4 A magnified structural diagram of part A in the middle; Figure 6 for Figure 4 A magnified structural diagram of part B.

[0020] In the diagram: 1-Fixed support platform, 2-Multi-joint robotic arm body, 3-Multi-dimensional compliant docking unit, 4-Docking fixture, 31-Upper connecting plate, 32-Central cylinder, 33-Guide rod, 34-Axial elastic element, 35-Lower floating plate, 36-Anti-detachment plate, 37-Adjusting nut, 38-Central column, 39-Brake telescopic cylinder, 310-Groove, 311-Modible through hole, 312-First side groove, 313-Second side groove, 314-Radial elastic bushing, 315-Positioning cylinder, 316-Matching groove. 317-Ring plate, 318-First ball bearing, 319-Brake pin, 320-Adapter plate, 321-Radial fixing pin, 322-Axial fixing pin, 323-Reset elastic element, 41-Support frame, 42-Support block, 43-Worm gear, 44-Motor, 45-Worm wheel, 46-Clamping telescopic cylinder, 47-Bearing support tube, 48-U-shaped frame, 49-Trapezoidal block, 410-Anti-detachment column, 411-Clamping frame, 412-Connecting arm, 413-Elastic pad, 414-Clamping plate, 415-Adjusting bolt. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments and their specific features are only for explaining the present invention and should not be considered as an undue limitation on the scope of protection of the present invention.

[0022] like Figures 1 to 6The image shows a multi-degree-of-freedom robotic arm for vehicle frame docking assembly, provided in a basic embodiment of the present invention. The robotic arm includes a fixed platform 1, a multi-joint robotic arm body 2 mounted on the fixed platform 1, and a docking fixture 4 mounted at the distal end of the multi-joint robotic arm body 2. Its core inventive point lies in the inclusion of a multi-dimensional compliant docking unit 3, which is connected in series between the distal end of the multi-joint robotic arm body 2 and the docking fixture 4.

[0023] In this embodiment, the multidimensional compliant docking unit 3 specifically includes an upper connecting plate 31, a lower floating plate 35, at least three sets of elastic compliant components, and a locking component. The upper connecting plate 31 is fixedly connected to the distal end of the multi-joint robotic arm body 2; the lower floating plate 35 is fixedly connected to the docking fixture 4; the at least three sets of elastic compliant components are evenly arranged circumferentially on the outer side between the upper connecting plate 31 and the lower floating plate 35 to provide axial elastic support and radial elastic shear support perpendicular to the axial direction. The locking component is installed in the middle between the upper connecting plate 31 and the lower floating plate 35.

[0024] As can be seen from the above structure, in the initial stage of frame docking and assembly, the lower floating plate 35 is in an unlocked state. At this time, due to the presence of the elastic compliant component, the lower floating plate 35 can passively compliantly move relative to the upper connecting plate 31 through axial and radial translation. This compliant floating capability effectively absorbs the absolute positioning error of the robotic arm and the manufacturing tolerance of the frame workpiece, avoiding jamming or damage caused by rigid contact. When the docking reaction force reaches a preset threshold, the locking component mechanically locks the lower floating plate 35 and the upper connecting plate 31 in axial and radial degrees of freedom, switching them to a rigid connection state. In other words, this solution achieves dual-mode switching between "compliant guiding alignment" and "rigid locking fixation" through a set of mechanical structures, taking into account both the error tolerance in the initial stage of assembly and the connection rigidity of subsequent assembly.

[0025] To further improve the clamping adaptability and directional adjustment flexibility for different frame specifications, such as Figures 1 to 3 As shown, in a preferred embodiment, the docking fixture 4 includes a support frame 41, a load-bearing support tube 47, a clamping frame 411, a connecting arm 412, a worm gear 45, a worm 43, and a motor 44.

[0026] Specifically, the support frame 41 is fixedly mounted on the lower floating plate 35; the bearing support tube 47 is rotatably mounted on the lower part of the support frame 41. A U-shaped frame 48 is fixed to one end of the bearing support tube 47, a clamping telescopic cylinder 46 is fixed to the middle of the U-shaped frame 48, a trapezoidal block 49 is fixed to the output end of the clamping telescopic cylinder 46, and anti-detachment columns 410 are respectively fixed to the two sides of the trapezoidal block 49. Clamping frames 411 are slidably mounted on the two anti-detachment columns 410, and multiple adjusting bolts 415 are threaded to the ends of the clamping frames 411. Clamping plates 414 are rotatably connected to the ends of the adjusting bolts 415, and elastic pads 413 are fixed to the clamping plates 414. The connecting arm 412 is fixed between the ends of the two branches of the U-shaped frame 48, and both clamping frames 411 are slidably connected to the connecting arm 412.

[0027] As a more specific structural form, the trapezoidal block 49 has an isosceles trapezoidal shape; the clamping frame 411 adopts an L-shaped structure, one branch of the clamping frame 411 is slidably connected to the connecting arm 412, and the other branch end of the clamping frame 411 is slidably connected to the anti-detachment column 410.

[0028] Based on the above structure, when the clamping telescopic cylinder 46 extends or retracts, the trapezoidal block 49 moves accordingly. Guided by the anti-detachment column 410 and the connecting arm 412, it drives the two L-shaped clamping frames 411 to move closer or further apart, achieving rapid clamping and release of frame components of different widths. Simultaneously, the adjusting bolt 415 can pre-adjust the extension position of the clamping plate 414 to meet the support requirements of workpieces with specific shapes.

[0029] Based on this, the worm gear 45 is fixedly mounted on the bearing support tube 47; the worm 43 is meshed with the worm gear 45, and support blocks 42 are rotatably mounted on both ends of the worm gear 45. The support blocks 42 are fixedly connected to the support frame 41, and a motor 44, which is driven by the worm gear 43, is also fixed on the support frame 41. When it is necessary to adjust the assembly direction of the frame sub-component, the motor 44 is started to drive the worm gear 43 to rotate, which drives the worm gear 45 and the bearing support tube 47 to rotate as a whole, thereby driving the U-shaped frame 48 and its clamping components to rotate to the target angle. Since the worm gear 43 and the worm gear 45 have reverse self-locking characteristics, this structure can maintain a stable posture lock after adjustment, improving the reliability of direction adjustment.

[0030] To specifically implement the above-mentioned anisotropic compliant floating function, such as Figure 1 , Figure 4 and Figure 5 As shown, in a preferred embodiment, each set of the elastic compliant components includes a movable through hole 311, a positioning cylinder 315, a guide rod 33, and an axial elastic element 34.

[0031] The movable through hole 311 is formed on the outer side of the lower floating plate 35. The positioning cylinder 315 is located inside the movable through hole 311, and a radial elastic bushing 314 is fixedly fitted on the upper part of the positioning cylinder 315. The outer wall of the radial elastic bushing 314 is connected to the fitting groove 316 in the lower floating plate 35. The lower floating plate 35 also has a side groove for axially limiting the positioning cylinder 315. The guide rod 33 is slidably disposed inside the positioning cylinder 315. The upper end of the guide rod 33 is fixedly connected to the upper connecting plate 31, and the lower end of the guide rod 33 is threadedly connected to an adjusting nut 37. The axial elastic element 34 is sleeved on the guide rod 33 between the positioning cylinder 315 and the upper connecting plate 31.

[0032] To enable reliable radial compliant movement of the above structure, optionally, the diameter of the upper end of the movable through hole 311 is larger than the diameter of its lower end, and the diameter of the lower end of the movable through hole 311 is larger than the diameter of the guide rod 33, allowing the guide rod 33 to generate radial movement space within the hole. Simultaneously, an anti-detachment disc 36 is integrally formed on the upper side of the adjusting nut 37, with an outer diameter larger than the lower diameter of the movable through hole 311, to prevent the lower floating disc 35 from detaching from the guide rod 33 under extreme displacement. Furthermore, several second ball bearings (not shown) are installed on the anti-detachment disc 36, and a third ball bearing (not shown) that abuts against the axial elastic element 34 can also be installed at the lower end of the positioning cylinder 315. These ball bearings can convert sliding friction into rolling friction, significantly reducing the resistance during radial movement of the lower floating disc 35 and ensuring the sensitivity of the compliant movement.

[0033] Regarding the axial limiting structure of the positioning cylinder 315, specifically, the positioning cylinder 315 includes an upper limiting ring, a middle limiting ring, and a lower limiting ring, and the radial elastic bushing 314 is installed between the upper limiting ring and the middle limiting ring. The side groove includes a first side groove 312 and a second side groove 313. The middle limiting ring is slidably connected to the second side groove 313, and the lower limiting ring is slidably connected to the first side groove 312. This multi-level limiting structure ensures that the positioning cylinder 315 can move synchronously with the lower floating plate 35 in the radial direction, while also limiting its axial movement, thus ensuring the stability of the elastic support.

[0034] For example, the axial elastic element 34 can be a disc spring assembly or a coil spring. To better accommodate the main radial errors of the frame during docking, as a preferred anisotropic design, the radial elastic bushing 314 is a rubber-metal composite bushing with a radial stiffness less than 1 / 10 of its axial stiffness. The compression of the axial elastic element 34 can be pre-adjusted by rotating the adjusting nut 37, thereby flexibly setting the axial compression displacement threshold required to trigger locking.

[0035] To ensure the speed and reliability of the locking action, such as Figure 1 , Figure 4 and Figure 6 As shown, in a preferred embodiment, the locking assembly includes a central cylinder 32, a central column 38, a ring plate 317, an adapter plate 320, a brake pin 319, a radial fixing pin 321, and an axial fixing pin 322.

[0036] The central cylinder 32 is fixed to the lower center of the upper connecting plate 31; the central column 38 is fixed to the upper center of the lower floating plate 35, and the diameter of the central column 38 is smaller than the lower inner diameter of the central cylinder 32 to accommodate radial movement of the central column 38 relative to the central cylinder 32. The annular plate 317 is slidably disposed inside the central cylinder 32, and multiple brake telescopic cylinders 39 are circumferentially distributed and fixed on the upper side of the annular plate 317. The cylinder bodies of the brake telescopic cylinders 39 are fixedly connected to the upper connecting plate 31. The adapter plate 320 is located below the annular plate 317 and is slidably connected to the central column 38. The lower end of the central cylinder 32 is also slidably connected to the adapter plate 320.

[0037] The brake pin 319 is axially slidably mounted on the outer side of the adapter plate 320. A first ball bearing 318, which abuts against the ring plate 317, is mounted on the upper end of the brake pin 319. A reset elastic element 323 is installed between the outer edge of the brake pin 319 and the adapter plate 320. Radial fixing pins 321 and axial fixing pins 322, which cooperate with the brake pin 319, are slidably mounted on the inner side of the adapter plate 320. The radial fixing pin 321 abuts against the lower end of the central cylinder 32 to radially fix the adapter plate 320, while the axial fixing pin 322 abuts against the side wall of the central column 38 to axially fix the adapter plate 320.

[0038] Regarding the locking and unlocking triggering mechanism, specifically, when no external force is applied, under the elastic force of the reset elastic element 323, the brake pin 319 moves upward and magnetically pulls the radial fixing pin 321 to separate from the lower end of the central cylinder 32, and the axial fixing pin 322 to separate from the side wall of the central column 38. At this time, the adapter plate 320 can float freely radially, and the locking assembly is in the unlocked state. When the brake telescopic cylinder 39 extends and presses the brake pin 319 through the ring plate 317, the brake pin 319 overcomes the elastic force of the reset elastic element 323 and moves downward. The brake pin 319 simultaneously pushes the radial fixing pin 321 and the axial fixing pin 322 to move, so that the radial fixing pin 321 abuts against the lower end of the central cylinder 32 to radially fix the adapter plate 320, and the axial fixing pin 322 abuts against the side wall of the central column 38 to axially fix the adapter plate 320, and the locking assembly enters the locked state.

[0039] To make the above transmission smoother, the lower end of the brake pin 319 is provided with two opposing conical inclined surfaces. The upper end of the radial fixing pin 321 is engaged with one conical inclined surface, and the outer end of the axial fixing pin 322 is engaged with the other conical inclined surface, thereby realizing that one brake pin 319 can drive the action of two directional fixing pins at the same time.

[0040] In this embodiment, the reset elastic element 323 is preferably a helical compression spring, whose elastic force is sufficient to ensure reliable reset of each fixing pin when no external force is applied. The ring plate 317 adopts a ring-shaped structure, and its inner diameter is the same as the lower end inner diameter of the central cylinder 32, so as to ensure that it slides smoothly under the guidance of the inner wall of the central cylinder 32.

[0041] In practical use, the multi-degree-of-freedom robotic arm for chassis docking and assembly of the present invention operates according to the following typical process: First, the system starts up, and the multi-joint robotic arm body 2 moves along a preset trajectory, driving the multi-dimensional compliant docking unit 3 and docking fixture 4 to the workstation where the frame component to be assembled is located. During this process, the lower floating plate 35 of the multi-dimensional compliant docking unit 3 is in an unlocked compliant state.

[0042] Subsequently, the docking fixture 4 performs the clamping action. The clamping telescopic cylinder 46 drives the trapezoidal block 49 to move, and with the guiding action of the anti-detachment column 410 and the connecting arm 412, the two L-shaped clamping frames 411 move closer together synchronously, and the frame component is firmly clamped by the clamping plate 414 and the elastic pad 413. If it is necessary to adjust the orientation of the workpiece, the motor 44 drives the worm gear 43 to rotate and engage the worm wheel 45. Utilizing the reverse self-locking function of the worm gear, the load-bearing support tube 47 and the U-shaped frame 48 are rotated as a whole, adjusting the frame component to the target assembly angle.

[0043] Next, the multi-joint robotic arm 2 continues to move the frame sub-component closer to the frame body and attempt docking. In the initial contact phase, due to the passive floating capability provided by the axial elastic element 34 and the radial elastic bushing 314, the lower floating disk 35 can make slight axial and radial compliant movements relative to the upper connecting disk 31, automatically compensating for position and attitude deviations, achieving smooth introduction, and avoiding jamming or surface damage caused by hard collisions.

[0044] As the docking process progresses, the contact force between the frame sub-component and the frame body gradually increases. When the docking reaction force causes the axial compressive displacement of the lower floating disc 35 relative to the upper connecting disc 31 to exceed a preset threshold, the brake telescopic cylinder 39 immediately extends and pushes the ring plate 317 down to press down the brake pin 319. The brake pin 319 overcomes the elastic force of the reset elastic element 323 and moves downward. Its lower end's tapered slope simultaneously pushes the radial fixing pin 321 and the axial fixing pin 322 outward, respectively abutting against the lower end of the center cylinder 32 and the side wall of the center column 38. This action completely mechanically locks the lower floating disc 35 and the upper connecting disc 31 in both axial and radial degrees of freedom.

[0045] Finally, in the rigid locked state, the multi-joint robotic arm body 2 can be subjected to subsequent assembly operations such as fastening or welding. At this time, the entire connecting chain has extremely high overall rigidity, ensuring that the assembly accuracy is not affected by the floating unit.

[0046] In practical production applications, this system can flexibly adapt to various working modes. For example, in the coarse positioning stage, the axial compression displacement threshold can be set to a larger value and the locking can be delayed to make full use of the floating capability to absorb errors; in the fine positioning or heavy-load pressing stage, the threshold can be set to a smaller value and the locking can be performed in advance to ensure the stable transmission of pressing force.

[0047] It should be clarified that the specific shapes, quantities, and connection methods of the components shown in the specification and drawings of this invention are merely illustrative examples. For instance, the term "electrical connection" mentioned above should be interpreted broadly, encompassing both direct connections via wires and indirect connections via intermediate coupling devices. The multi-joint robotic arm body 2 is not limited to the six-degree-of-freedom serial joint industrial robotic arm shown in the drawings; it can also be a seven-degree-of-freedom redundant robotic arm or a SCARA robot, as long as the multi-dimensional compliant docking unit 3 can be installed at its distal end.

[0048] To facilitate monitoring of axial compression displacement, a laser sensor (not shown) can also be installed on the upper connecting disk 31. This sensor emits a beam of light through a specific reference surface of the lower floating disk 35 to measure the absolute distance change between the two in real time, providing a locking trigger signal to the controller. However, this is not the only way to implement the invention; equivalent alternatives can be used, such as a magnetostrictive displacement sensor or a Hall effect sensor.

[0049] It is worth noting that when the brake telescopic cylinder 39 or the sensor malfunctions unexpectedly, the system can be designed as a fail-safe mode, that is, the reset elastic element 323 keeps the locking component in the unlocked state when the power is off or the pressure is lost, to prevent accidental locking and damage to the equipment.

[0050] In summary, the various embodiments of the present invention and their optional features (such as the specific clamping structure of the docking fixture 4, the anisotropic stiffness parameters of the elastic compliant component, the magnetic resetting method of the locking component, etc.) can be arbitrarily combined without contradicting each other. For example, a preferred docking fixture with worm gear adjustment function can be combined with a basic elastic compliant component, or an elastic compliant component with a ball bearing friction-reducing structure can be used in conjunction with a locking component. Any equivalent substitutions, structural modifications, or material substitutions made to the above embodiments within the core concept and spirit of the present invention should be included within the scope of protection claimed in this application.

Claims

1. A multi-degree-of-freedom robotic arm for vehicle frame docking assembly, comprising a fixed platform (1), a multi-joint robotic arm body (2) mounted on the fixed platform (1), and a docking fixture (4) mounted at the distal end of the multi-joint robotic arm body (2), characterized in that, Also includes: A multi-dimensional compliant docking unit (3) is connected in series between the far end of the multi-joint robotic arm body (2) and the docking fixture (4); The multidimensional compliant docking unit (3) includes: The upper connecting plate (31) is fixedly connected to the far end of the multi-joint robotic arm body (2); The lower floating disk (35) is fixedly connected to the docking fixture (4); An elastic compliant assembly, disposed between the upper connecting plate (31) and the lower floating plate (35), provides axial elastic support and radial elastic shear support, enabling the lower floating plate (35) to passively compliantly align with the upper connecting plate (31) in an unlocked state, allowing for axial and radial translational movements. A locking assembly is installed between the upper connecting plate (31) and the lower floating plate (35); When the lower floating plate (35) is subjected to the docking reaction force of the frame component in the assembly direction and generates an axial compression displacement exceeding a preset threshold relative to the upper connecting plate (31), the locking assembly mechanically locks the lower floating plate (35) and the upper connecting plate (31) in axial and radial degrees of freedom, so that the two switch from a relatively floating compliant state to a rigid connection state.

2. The multi-degree-of-freedom robotic arm for chassis docking and assembly according to claim 1, characterized in that, The resilient compliant component includes: The guide rod (33) is fixedly connected at its upper end to the upper connecting plate (31); A positioning cylinder (315) is slidably sleeved on the outside of the guide rod (33), and a radial elastic bushing (314) is provided between the positioning cylinder (315) and the lower floating plate (35) to provide the radial elastic shear support; and An axial elastic element (34) is sleeved on the guide rod (33) and abuts against the upper connecting plate (31) and the positioning cylinder (315) or the lower floating plate (35) to provide the axial elastic support.

3. The multi-degree-of-freedom robotic arm for chassis docking and assembly according to claim 2, characterized in that, The lower floating disk (35) has a through hole (311) on its outer side, and the positioning cylinder (315) is located inside the through hole (311). The radial elastic bushing (314) is sleeved and fixed on the upper part of the positioning cylinder (315), and the outer wall of the radial elastic bushing (314) is connected to the fitting groove (316) opened in the lower floating plate (35). The lower end of the guide rod (33) passes through the positioning cylinder (315) and is threadedly connected to an adjusting nut (37). An anti-detachment disc (36) is provided on the upper side of the adjusting nut (37). The outer diameter of the anti-detachment disc (36) is larger than the lower diameter of the movable through hole (311).

4. The multi-degree-of-freedom robotic arm for chassis docking and assembly according to claim 1, characterized in that, The locking component includes: The central cylinder (32) is fixed to the lower side of the upper connecting plate (31); The central column (38) is fixed to the upper side of the lower floating disk (35), and the diameter of the central column (38) is smaller than the lower inner diameter of the central cylinder (32); The adapter plate (320) is slidably disposed on the inner side of the central cylinder (32) and slidably connected to the central column (38); Brake pin (319) is slidably mounted on the outside of adapter plate (320) along the axial direction; A radial fixing pin (321) is slidably installed on the inner side of the adapter plate (320) to abut against the central cylinder (32) to restrict the radial movement of the adapter plate (320); An axial fixing pin (322) is slidably mounted on the inner side of the adapter plate (320) to abut against the central post (38) to restrict the axial movement of the adapter plate (320); and A brake telescopic cylinder (39) is fixed to the upper connecting plate (31), and its output end is used to push the brake pin (319) to slide so as to drive the radial fixing pin (321) and the axial fixing pin (322) to extend simultaneously.

5. The multi-degree-of-freedom robotic arm for chassis docking and assembly according to claim 4, characterized in that, A reset elastic element (323) is installed between the brake pin (319) and the adapter plate (320). When there is no external force, the reset elastic element (323) is used to drive the brake pin (319) to reset, so as to release the locking state of the radial fixing pin (321) and the axial fixing pin (322); The lower end of the brake pin (319) is provided with two opposing conical inclined surfaces. The upper end of the radial fixing pin (321) is engaged with one of the conical inclined surfaces, and the outer end of the axial fixing pin (322) is engaged with the other conical inclined surface.

6. The multi-degree-of-freedom robotic arm for chassis docking and assembly according to claim 1, characterized in that, The docking fixture (4) includes: The support frame (41) is fixed to the lower floating plate (35); The load-bearing support tube (47) is rotatably installed on the lower part of the support frame (41), and a U-shaped frame (48) is fixed at one end of the load-bearing support tube (47). A clamping telescopic cylinder (46) is fixed in the middle of the U-shaped frame (48), and a trapezoidal block (49) is fixed at its output end. Two clamping frames (411) are slidably mounted on the U-shaped frame (48) and are located on both sides of the trapezoidal block (49), respectively, for moving closer or further apart from each other under the drive of the clamping telescopic cylinder (46) to clamp or release the frame sub-component.

7. The multi-degree-of-freedom robotic arm for chassis docking and assembly according to claim 6, characterized in that, The trapezoidal block (49) has an isosceles trapezoidal structure. Anti-detachment columns (410) are fixed on the two sides of the trapezoidal block (49). The two clamping frames (411) are slidably engaged with the corresponding anti-detachment columns (410). A connecting arm (412) is fixed between the ends of the two branches of the U-shaped frame (48), and both clamps (411) are slidably connected to the connecting arm (412); The end of the clamping frame (411) is threaded with a plurality of adjusting bolts (415), and the end of the adjusting bolts (415) is rotatably connected with a clamping plate (414), and an elastic pad (413) is fixed on the clamping plate (414).

8. The multi-degree-of-freedom robotic arm for chassis docking and assembly according to claim 6, characterized in that, The docking fixture (4) also includes: The worm gear (45) is installed and fixed on the bearing support tube (47); The worm (43) meshes with the worm wheel (45); and The motor (44) is fixed on the support frame (41), and its output end is connected to the worm gear (43) for driving the bearing support tube (47) and the U-shaped frame (48) to rotate around their own axis.

9. The multi-degree-of-freedom robotic arm for chassis docking and assembly according to claim 1, characterized in that, The main body (2) of the multi-joint robotic arm is a six-degree-of-freedom serial joint type industrial robotic arm, and its distal wrist is directly rigidly connected to the upper connecting plate (31) of the multi-dimensional compliant docking unit (3) through a flange. A laser sensor is installed on the upper connecting plate (31) to measure the axial distance between the upper connecting plate (31) and the lower floating plate (35) in real time, so as to monitor whether the axial compression displacement exceeds the preset threshold.

10. A method for assembling a vehicle frame, applied to a multi-degree-of-freedom robotic arm for assembling a vehicle frame as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. The multi-joint robotic arm body (2) drives the multi-dimensional compliant docking unit (3) and docking fixture (4) to the location of the frame component. At this time, the lower floating plate (35) of the multi-dimensional compliant docking unit (3) is in an unlocked compliant state. S2. The frame component is clamped by the docking fixture (4), and the frame component is moved closer to the frame body by the multi-joint robotic arm body (2); S3. During the contact process between the frame sub-component and the frame body, the axial elastic support and radial elastic shear support provided by the elastic compliant component are used to make the lower floating disk (35) perform passive compliant motion relative to the upper connecting disk (31) by axial translation and / or radial translation, so as to compensate for position and attitude errors. S4. When the axial compression displacement of the lower floating disk (35) relative to the upper connecting disk (31) exceeds the preset threshold, the locking component is activated to mechanically lock the lower floating disk (35) and the upper connecting disk (31) in the axial and radial degrees of freedom, so that the two are switched from the compliant state of relative floating to the rigid connection state. S5. In the rigid connection state, the subsequent assembly operation is performed by the multi-joint robotic arm body (2).

Images