Variable stiffness active-passive floating force control device for robotic grinding and polishing

Abstract

This invention discloses a variable stiffness active-passive floating force control device for robotic grinding and polishing, comprising a fixed platform, a moving platform, a polishing head assembly, a flexible linkage mechanism, and a variable stiffness mechanism. The flexible linkage mechanism includes multiple parallel flexible branches, each branch comprising a flexible link, an intermediate connector, and a drive motor. One end of each flexible link is connected to the moving platform, and the other end is connected to the drive motor via the intermediate connector. The variable stiffness mechanism includes a variable stiffness motor, a worm gear, and a worm wheel that engages with the worm gear. The variable stiffness motor is mounted on the fixed platform, and the worm gear is located at the drive end of the variable stiffness motor. A support is rotatably mounted on the fixed platform and has a rotation axis orthogonal to a first direction. The worm wheel is mounted on the support and can rotate under the drive of the worm gear. This invention achieves a passively compliant variable stiffness function by synchronously adjusting the driving posture of the flexible linkage mechanism through the variable stiffness mechanism, offering advantages such as compact structure and high precision.

Description

Technical Field

[0001] This invention relates to the field of polishing equipment, and more specifically to a variable stiffness active-passive floating force control device for robotic grinding and polishing. Background Technology

[0002] Currently, robotic grinding and polishing equipment systems typically have a pneumatically driven, force-controlled floating end effector installed at the end. This end effector has one degree of freedom or two rotational and one translational (2R1T) degrees of freedom, possessing both active and passive compliant characteristics. Passive compliant stiffness can be adjusted by regulating air pressure. However, pneumatic drives have a slower response time than electric drives and also suffer from drawbacks such as large air source volume, significant noise pollution, and limited flexibility in application deployment.

[0003] Rigid serial-parallel hybrid robotic polishing systems also have wide applications. They can provide multi-degree-of-freedom active compliance through parallel end-effectors, and have the advantages of low inertia and fast response speed. However, active compliance control has a delay compared to passive compliance and is more prone to jamming, resulting in scratches on the surface of the polished workpiece.

[0004] In addition, installing appropriate end-effectors on the flanges of serial robots to form a robotic polishing system is also a common approach. However, serial mechanisms have large inertia and poor precision, while rigid parallel mechanisms lack passive compliance characteristics. Therefore, technical solutions that combine the two, such as parallel end-effectors based on flexible links, have received increasing attention. For example, Chen Genliang of Shanghai Jiao Tong University proposed a spatial six-degree-of-freedom flexible link parallel mechanism. In this existing technology, a two-degree-of-freedom composite drive branch is introduced, resulting in a total of three branches and six drives. By changing the initial position and attitude of the flexible link, the six-degree-of-freedom coupled motion of the end-effector platform is achieved.

[0005] However, in the aforementioned existing spatial six-degree-of-freedom flexible linkage parallel mechanism, the two-degree-of-freedom composite drive branches are connected in series, and the accumulation of drive errors leads to an increase in the error of the moving platform; the mechanism is too large, and the lateral arrangement of the drive occupies too much space, which easily causes interference; the flexible linkage parallel mechanism lacks a variable stiffness mechanism, making it unable to adapt to grinding and polishing workpieces with different stiffnesses. Therefore, a new solution is still needed. Summary of the Invention

[0006] To at least partially address the shortcomings of the prior art, the main objective of this invention is to provide a variable stiffness active-passive floating force control device for robotic grinding and polishing, which can actively adjust the passive compliance stiffness of the moving platform and has the advantages of compact structure and high precision.

[0007] To achieve the above-mentioned main objectives, the present invention provides a variable stiffness active-passive floating force control device for robotic grinding and polishing, which is installed at the end of a robot performing grinding and polishing operations. The variable stiffness active-passive floating force control device includes a fixed platform and a moving platform spaced apart in a first direction, with a polishing head assembly provided on the moving platform; it also includes a flexible linkage mechanism and a variable stiffness mechanism.

[0008] The flexible linkage mechanism includes multiple parallel flexible branches. Each flexible branch includes a flexible link, an intermediate connector, and a drive motor. One end of the flexible link is connected to the moving platform, and the drive motor is mounted on the fixed platform via a bracket. One end of the flexible link is connected to the drive motor via the intermediate connector.

[0009] The variable stiffness mechanism includes a variable stiffness motor, a worm gear, and a worm wheel that cooperates with the worm gear. The variable stiffness motor is mounted on a fixed platform, and the worm gear is mounted at the drive end of the variable stiffness motor. The bracket is rotatably mounted on the fixed platform and has a rotation axis orthogonal to the first direction. The worm wheel is mounted on the bracket and can rotate under the drive of the worm gear.

[0010] Specifically, the flexible connecting rods are deformed by the coordinated control of the drive motors in multiple flexible branches, thereby realizing the coupled motion of the moving platform in space; the support is rotated around its rotation axis by controlling the variable stiffness motor, thereby changing the attitude of the flexible branches, causing the flexible connecting rods to deform and change the passive compliance stiffness of the moving platform.

[0011] According to a specific embodiment of the present invention, a fixed platform is provided with two opposing frame plates, each frame plate having a mounting groove, and a rotating shaft is provided on each of the opposite sides of the bracket, the rotating shaft being rotatably supported within the mounting groove.

[0012] Furthermore, a slewing bearing is provided on the slewing shaft.

[0013] According to a specific embodiment of the present invention, multiple supports are distributed in a ring, and a worm is disposed in the middle of the multiple supports; wherein, the worm wheel is a sector-shaped worm wheel disposed on the relatively inner side of the support, and the multiple worm wheels are respectively connected to the same worm.

[0014] Furthermore, multiple supports are distributed in an array.

[0015] According to a specific embodiment of the present invention, there are six flexible branches to coordinate and realize the spatial six-degree-of-freedom coupled motion of the moving platform; wherein, the six flexible branches are arranged in pairs, and the two drive motors in each pair of flexible branches are mounted on the fixed platform through the same bracket.

[0016] According to a specific embodiment of the present invention, the intermediate connecting member is a nut coupling, and the end of the drive motor is provided with a lead screw. The nut coupling is mounted on the lead screw and can move under the drive of the drive motor, thereby causing the flexible connecting rod to deform.

[0017] According to one specific embodiment of the present invention, it further includes a base having an inner cavity for mounting an electronic control module, and a fixed platform is mounted on the base and located at the top of the inner cavity to close the inner cavity.

[0018] Furthermore, the base is equipped with an aviation connector for connecting to external equipment, and the electronic control module is connected to the aviation connector.

[0019] According to one specific embodiment of the present invention, the polishing head assembly includes a polishing motor and a polishing head, wherein the polishing head is connected to the drive end of the polishing motor via a coupling; wherein the polishing motor is mounted on the side of the moving platform closer to the fixed platform, and the polishing head is disposed on the other side of the moving platform away from the fixed platform.

[0020] This invention has the following beneficial effects: It provides a variable stiffness active-passive floating force control device for robotic grinding and polishing, which reconfigures the flexible linkage mechanism to effectively improve the accuracy and stiffness of the moving platform; at the same time, it optimizes the drive structure and drive method to achieve a smaller size and avoid interference with the robot and workpiece; this invention achieves the function of variable stiffness with passive compliance by synchronously adjusting the attitude of the flexible linkage mechanism through the variable stiffness mechanism.

[0021] In addition, the variable stiffness mechanism of the present invention uses a single worm to drive different worm wheels simultaneously, thereby realizing the change of the posture of multiple flexible branches, which is beneficial to the adjustment of stiffness, while improving the compactness of the structure and reducing the volume.

[0022] To more clearly illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0023] Figure 1 This is an overall structural diagram of the robot for performing grinding and polishing operations according to the present invention;

[0024] Figure 2 This is a three-dimensional view of a flexible parallel actuator device;

[0025] Figure 3 It is a 3D diagram of a variable stiffness mechanism;

[0026] Figure 4 This is a top view of a variable stiffness mechanism;

[0027] Figure 5 This is an exploded view of a variable stiffness mechanism;

[0028] Figure 6 This is an exploded view of the base section. Detailed Implementation

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0030] This invention provides a variable stiffness active-passive floating force control device 30 for robotic grinding and polishing, installed at the end effector of a robot performing grinding and polishing operations; exemplarily, such as... Figure 1 As shown, the robot performing the grinding and polishing operation also includes, for example, a workbench 10 and a robotic arm 20. The robotic arm 20 is preferably detachably mounted on the table surface of the workbench 10. The robotic arm 20 is preferably a six-axis robotic arm, and a variable stiffness active-passive floating force control device 30 is mounted at the end of the robotic arm 20.

[0031] like Figure 2 As shown, the variable stiffness active-passive floating force control device 30 of the embodiment includes a base 31, a fixed platform 32, a moving platform 33, a polishing head assembly 34, a flexible linkage mechanism 35, and a variable stiffness mechanism 36; wherein, the base 31 is used to connect to the adapter flange 21 of the robotic arm 20, the fixed platform 32 is disposed on the base 31, the moving platform 33 is connected to the fixed platform 32 through the flexible linkage mechanism 35 and is spaced apart from the fixed platform 32 in a first direction, the polishing head assembly 34 is disposed on the fixed platform 32 for performing polishing tasks, and the variable stiffness mechanism 36 is disposed on the fixed platform 32 for adjusting the stiffness of the flexible linkage mechanism 35.

[0032] For example, the base 31 is preferably a three-dimensionally printed integral structural component; such as Figure 6 As shown, the base 31 has an inner cavity 311 for mounting the electronic control module 37. The fixed platform 32 is mounted on the base 31 and located on top of the inner cavity 311 to enclose the inner cavity 311. Furthermore, the base 31 is provided with an aviation connector 312 for connecting to external equipment. The electronic control module 37 is connected to the aviation connector 312, for example, the electronic control module 37 is specifically supported in the inner cavity 311 by a plurality of brass studs 38.

[0033] Please continue reading. Figure 2-5The flexible linkage mechanism 35 includes six parallel flexible branches 35a, which work together to achieve six-degree-of-freedom coupled motion of the moving platform 33 in space. Each flexible branch 35a includes a flexible link 351, an intermediate connector 352, and a drive motor 353. One end of the flexible link 351 is connected to the moving platform 33, and the drive motor 353 is mounted on the fixed platform 32 via a bracket 354. One end of the flexible link 351 is connected to the drive motor 353 via the intermediate connector 352. The flexible link 351 is deformed by the coordinated control of the drive motors 353 in the multiple flexible branches 35a, thereby achieving coupled motion of the moving platform 33 in space.

[0034] For example, the flexible link 351 is made of spring steel with a Young's modulus of 1.93 × 10^11 Pa and a shear modulus of 7.4231 × 10^10. In the embodiment, the flexible link 351 is slender cylindrical in shape when not subjected to external force, with a cross-sectional circle radius of, for example, 0.3 mm, and a length between the proximal and distal hinge points of, for example, 100 mm.

[0035] Furthermore, the intermediate connecting member 352 is specifically a nut coupling, and the end of the drive motor 353 is provided with a lead screw. Preferably, the drive motor 353 is a lead screw type stepper motor. The nut coupling is set on the lead screw and can move under the drive of the drive motor 353, thereby causing the flexible connecting rod 351 to deform.

[0036] In this embodiment, the fixed platform 32 is provided with two opposing frame plates 321, and the frame plates 321 are provided with mounting grooves 322. The bracket 354 is provided with rotating shafts 355 on both sides, and the rotating shafts 355 are rotatably supported in the mounting grooves 322. Preferably, the rotating shafts 355 are provided with rotating bearings 356, which are located in the mounting grooves 322 to improve the smoothness of rotation.

[0037] The variable stiffness mechanism 36 includes a variable stiffness motor 361, a worm gear 362, and a worm wheel 363 cooperating with the worm gear 362. The variable stiffness motor 361 is mounted on the fixed platform 32, and the worm gear 362 is located at the drive end of the variable stiffness motor 361. The support 354 is rotatably mounted on the fixed platform 32 and has a rotation axis orthogonal to the first direction. The worm wheel 363 is mounted on the support 354 and can rotate under the drive of the worm gear 362. In the embodiment, the flexible connecting rod 351 is driven to deform by the coordinated control of the six drive motors 353 in the six flexible branches 35a, thereby realizing the coupled motion of the moving platform 33 in space. The support 354 is driven to rotate around its rotation axis 355 by the control of the variable stiffness motor 361, thereby changing the attitude of the flexible branches 35a, causing the flexible connecting rod 351 to deform and change the passive compliance stiffness of the moving platform 33.

[0038] To further simplify the structure, the six flexible branches 35a in the embodiment are arranged in pairs, and the two drive motors 353 in each pair of flexible branches 35a are mounted on the fixed platform 32 via the same bracket 354. Specifically, the three brackets 354 in the embodiment are distributed in a ring, preferably arranged in an array; the worm 362 is located in the middle of the three brackets 354, wherein the worm wheel 363 is a fan-shaped worm wheel 363 located on the inner side of the bracket 354, and multiple worm wheels 363 are respectively connected to the same worm 362.

[0039] In the embodiment, by using a single worm gear 362 to simultaneously drive different (fan-shaped) worm wheels 363, the attitude of multiple flexible branches 35a can be changed. Specifically, the support 354 and its components can move in the pitch direction relative to the first direction. This structural layout can greatly reduce the space occupied, which is conducive to miniaturization and modular design, and makes the overall size close to that of the cooperating robotic arm 20, which helps to avoid interference.

[0040] The polishing head assembly 34 can be selected as needed. For example, in the embodiment, the polishing head assembly 34 includes a polishing motor 341 and a polishing head 342. The polishing head 342 is connected to the drive end of the polishing motor 341 by a structure such as a coupling. The polishing head 342 can be referred to the relevant structure in the prior art, which will not be elaborated here. Specifically, in the embodiment, the polishing motor 341 is installed on the side of the moving platform 33 close to the fixed platform 32, and the polishing head 342 is located on the other side of the moving platform 33 away from the fixed platform 32.

[0041] Although the present invention has been described above through embodiments, it should be understood that the above embodiments are only used to exemplarily describe possible implementations of the present invention and should not be construed as limiting the scope of protection of the present invention. That is, any substitutions or changes made by those skilled in the art in accordance with the present invention should also be covered by the scope of protection of the claims of the present invention.

Claims

1. A variable stiffness active-passive floating force control device for robotic grinding and polishing, installed at the end effector of a robot performing grinding and polishing operations, the variable stiffness active-passive floating force control device comprising a fixed platform and a moving platform spaced apart in a first direction, the moving platform being provided with a polishing head assembly; characterized in that: A flexible linkage mechanism includes multiple parallel flexible branches. Each flexible branch includes a flexible link, an intermediate connector, and a drive motor. One end of each flexible link is connected to the moving platform, and the drive motor is mounted on the fixed platform via a bracket. The other end of each flexible link is connected to the drive motor via the intermediate connector. There are six flexible branches to collaboratively achieve six-degree-of-freedom coupled motion of the moving platform. The six flexible branches are arranged in pairs, and the two drive motors in each pair are mounted on the fixed platform via the same bracket. A variable stiffness mechanism includes a variable stiffness motor, a worm gear, and a worm wheel that cooperates with the worm gear. The variable stiffness motor is mounted on a fixed platform, and the worm gear is located at the drive end of the variable stiffness motor. A bracket is rotatably mounted on the fixed platform and has a rotation axis orthogonal to a first direction. The worm wheel is mounted on the bracket and can rotate under the drive of the worm gear. Multiple brackets are arranged in a ring, and the worm gear is located in the middle of the multiple brackets. The worm wheel is a sector-shaped worm wheel located on the inner side of the bracket, and multiple worm wheels are respectively connected to the same worm gear. Specifically, the flexible link is deformed by the coordinated control of the drive motors in the multiple flexible branches, thereby realizing the coupled motion of the moving platform in space; the support is rotated around its rotation axis by controlling the variable stiffness motor, thereby changing the posture of the flexible branch, causing the flexible link to deform and change the passive compliance stiffness of the moving platform.

2. The variable stiffness active-passive floating force control device for robotic grinding and polishing as described in claim 1, characterized in that: The fixed platform is provided with two opposing frame plates, each frame plate having a mounting groove. The bracket has a rotating shaft on each of its opposite sides, and the rotating shaft is rotatably supported within the mounting groove.

3. The variable stiffness active-passive floating force control device for robotic grinding and polishing as described in claim 2, characterized in that: The rotary shaft is equipped with a rotary bearing.

4. The variable stiffness active-passive floating force control device for robotic grinding and polishing as described in claim 1, characterized in that: The multiple supports are arranged in an array.

5. The variable stiffness active-passive floating force control device for robotic grinding and polishing as described in claim 1, characterized in that: The intermediate connecting component is a nut coupling, and the end of the drive motor is provided with a lead screw. The nut coupling is mounted on the lead screw and can move under the drive of the drive motor, thereby causing the flexible connecting rod to deform.

6. The variable stiffness active-passive floating force control device for robotic grinding and polishing as described in claim 1, characterized in that: It also includes a base having an inner cavity for mounting an electronic control module, and the fixed platform is mounted on the base and located on top of the inner cavity to close the inner cavity.

7. The variable stiffness active-passive floating force control device for robotic grinding and polishing as described in claim 6, characterized in that: The base is provided with an aviation connector for connecting to external equipment, and the electronic control module is connected to the aviation connector.

8. The variable stiffness active-passive floating force control device for robotic grinding and polishing as described in claim 1, characterized in that: The polishing head assembly includes a polishing motor and a polishing head, the polishing head being connected to the drive end of the polishing motor via a coupling; wherein, the polishing motor is mounted on the side of the moving platform closer to the fixed platform, and the polishing head is disposed on the other side of the moving platform away from the fixed platform.

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