Stiffness flexible coupling agricultural picking robot arm joint

Abstract

A rigid-flexible coupling agricultural picking mechanical arm joint comprises a rigid-flexible coupling feeding joint, a flexible bending joint and a rigid wrist joint which are sequentially fixedly connected, and the rigid wrist joint is fixedly connected with an external rigid mechanical arm through a flange. The rigid-flexible coupling feeding joint comprises a telescopic end cover, a feeding fixed support, a bellows and a threaded column, the telescopic end cover is connected with the external rigid mechanical arm, one end of the bellows is connected with the telescopic end cover, the other end of the bellows is fixedly connected with one end of the threaded column, the other end of the threaded column is slidably arranged in the feeding fixed support, and the bellows is driven to realize telescopic movement through air pressure. The present application can realize high-precision positioning, flexible and efficient obstacle avoidance, end large-angle overturning and small-distance feeding and other functions, and after being combined with the rigid mechanical arm, the present application can realize efficient and lossless fruit picking operation process in a narrow and dense branch and leaf environment.

Description

Technical Field

[0001] This invention relates to a technology in the field of agricultural machinery, specifically a rigid-flexible coupled joint for an agricultural harvesting robot arm. Background Technology

[0002] The harvesting robotic arm needs to perform efficient and damage-free harvesting according to instructions. Traditional agricultural harvesting robotic arms usually adopt rigid industrial arm structures, which have problems such as large size and limited obstacle avoidance ability. When harvesting fruits in narrow and dense foliage environments, they have difficulties in obstacle avoidance and low harvesting efficiency. Summary of the Invention

[0003] This invention addresses the shortcomings of existing rigid robotic arms for agricultural harvesting, such as limited bending angle and obstacle avoidance capabilities, low precision in bending angle control, weak anti-collision capabilities, and poor environmental adaptability. It proposes a rigid-flexible coupled joint for agricultural harvesting robotic arms, which can perform functions such as high-precision positioning, flexible and efficient obstacle avoidance, large-angle end-effector rotation, and short-distance feeding. When combined with a rigid robotic arm, it can achieve efficient and damage-free fruit harvesting operations in narrow and dense foliage environments.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a rigid-flexible coupling agricultural harvesting robot arm joint, comprising: a rigid-flexible coupling feed joint, a flexible bending joint, and a rigid wrist joint that are fixedly connected in sequence, wherein the rigid wrist joint is fixedly connected to an external rigid robot arm via a flange.

[0006] The rigid-flexible coupling feed joint includes: a telescopic end cap, a feed fixing bracket, a bellows, and a threaded column. The telescopic end cap is connected to an external rigid robotic arm. One end of the bellows is connected to the telescopic end cap, and the other end is fixedly connected to one end of the threaded column. The other end of the threaded column is slidably disposed in the feed fixing bracket. The bellows is extended and retracted by air pressure.

[0007] The motor bracket includes three connected motor sub-brackets.

[0008] The rigid wrist joint includes: a flip motor support mechanism and a rotary motor support mechanism that are arranged opposite to each other and mesh with each other through a gear set, wherein: the flip motor support mechanism includes: an upper motor support and a horizontally arranged flip servo; the rotary motor support mechanism includes: a lower motor support and a vertically arranged rotary servo.

[0009] The gear set includes: a pair of upper cylindrical gears mounted on the upper motor bracket, a pair of lower cylindrical gears meshing with them and mounted on the lower motor bracket, a cylindrical gear connected to the rotary servo, and a lower flange mounted under the lower motor bracket. Any one of the upper cylindrical gears is connected to the output shaft of the tilting servo, and the cylindrical gear meshes with the lower flange. Technical effect

[0010] This invention utilizes a continuous structure of flexible bending joints, combining joints capable of large-angle rotation to achieve short-distance feeding. Compared to existing technologies, this invention achieves high-precision smooth bending within a -30 to 30° conical spherical region, making the rigid-flexible coupled agricultural robotic arm joint lighter, while maintaining sufficient flexibility and passive safety, enabling rapid obstacle avoidance and efficient harvesting in complex environments. Attached Figure Description

[0011] Figure 1 This is a perspective view of the present invention;

[0012] Figure 2 This is a front view of the structure of the present invention;

[0013] Figure 3 This is a three-dimensional view of the rigid-flexible coupling feed joint of the present invention;

[0014] Figure 4 This is a perspective view of the flexible bending joint of the present invention;

[0015] Figure 5 This is an exploded view of the rigid wrist joint of the present invention;

[0016] In the diagram: 1. Telescopic end cap; 2. Feed fixing bracket; 3. Bellows; 4. Six threaded posts; 5. Three limit bolts; 6. Flexible structure; 7. Pneumatic connector; 8. Ventilation hose; 9. Motor bracket; 10. Upper motor bracket; 11. Upper cylindrical gear; 12. Lower cylindrical gear; 13. Servo housing; 14. Tilting servo; 15. Lower motor bracket; 16. Rotating servo; 17. Cylindrical gear; 18. Lower flange; 19. Thin-walled bearing; 20. Gear bearing; 20. Detailed Implementation

[0017] like Figure 1 and Figure 2 As shown, this embodiment relates to a rigid-flexible coupling agricultural harvesting robot joint, which includes: a rigid-flexible coupling feed joint, a flexible bending joint, and a rigid wrist joint that are fixedly connected in sequence, wherein: the rigid wrist joint is fixedly connected to the external rigid robot arm through a flange.

[0018] like Figures 1-3As shown, the rigid-flexible coupling feed joint includes: a telescopic end cap 1, a feed fixing bracket 2, a bellows 3, and a threaded post 4 (4', 4”). The telescopic end cap 1 is connected to an external rigid robotic arm. One end of the bellows 3 is connected to the telescopic end cap 1, and the other end is fixedly connected to one end of the threaded post 4 (4', 4”). The other end of the threaded post 4 (4', 4”) is slidably disposed in the feed fixing bracket 2. The bellows 3 is telescopically driven by air pressure.

[0019] like Figure 1 , Figure 2 and Figure 4 As shown, the flexible bending joint achieves bending in all directions from 0 to 30° by driving the pull rope with three servo motors. The flexible bending joint includes a motor bracket 9 and a flexible structure 6 disposed thereon, wherein the flexible structure 6 is provided with a ventilation hose 8 with a pneumatic connector 7.

[0020] The flexible structure 6 is manufactured using flexible materials such as silicone through 3D printing. It has stronger tensile strength and torsional stiffness than conventional flexible structures and higher angular positioning accuracy within a small angle range. This significantly improves the obstacle avoidance and collision protection performance of the joint compared to ordinary rigid joints. The flexible structure 6 is connected to the motor bracket 9 and the rigid-flexible coupling feed joint by screws.

[0021] The motor bracket 9 includes three connected motor sub-brackets.

[0022] like Figure 1 , Figure 2 and Figure 5 As shown, the rigid wrist joint includes: a flip motor support mechanism and a rotary motor support mechanism that are arranged opposite to each other and mesh with each other through a gear set, wherein: the flip motor support mechanism includes: an upper motor support 10 and a horizontally arranged flip servo motor 14; the rotary motor support mechanism includes: a lower motor support 15 and a vertically arranged rotary servo motor 16.

[0023] The gear set includes: a pair of upper cylindrical gears 11 (11') mounted on the upper motor bracket 10, a pair of lower cylindrical gears 12 (12') meshing with them and mounted on the lower motor bracket 15, a cylindrical gear 17 connected to the rotary servo motor 16, and a lower flange 18 mounted under the lower motor bracket 15. Each upper cylindrical gear is connected to the output shaft of the tilting servo motor 14, and the cylindrical gear 17 meshes with the lower flange 18. The rotary servo motor 16 drives the cylindrical gear 17 to rotate, and through gear meshing, the lower flange 18 and the upper mechanism connected to it rotate a full circle. The tilting servo motor 14 drives the lower cylindrical gear 12' to rotate, and through the gear meshing of the upper cylindrical gears 11 and 11' with the lower cylindrical gears 12 and 12' respectively, the upper motor bracket 10 and its fixed connection part can achieve a large angle tilt of -15° to 160°. The joint features an asymmetrical flip design, with a range of motion tailored to the orientation of obstacles such as leaves in a dwarf, densely planted standard apple orchard. This allows the connected flexible bending joint to more easily avoid obstacles and provides a strong load-bearing capacity, enabling it to support the weight of the flexible bending joint and the feed joint without wobbling.

[0024] Through simulation experiments in the Pybullet environment, using SAC and PPO reinforcement learning algorithms to train the robotic arm joints, the experimental data obtained are: a harvesting success rate of >94% and a harvesting efficiency of approximately 9 seconds per fruit. This invention achieves controllable stiffness through a flexible omnidirectional bending joint, enabling high-precision smooth bending within a -30° to 30° conical spherical region. Compared to traditional rigid bending joints, it has advantages such as lighter weight, smaller size, higher flexibility, and stronger passive safety. Secondly, its rigid wrist can compensate for the limited range of motion of the flexible body, achieving a 150° omnidirectional large-angle rotation after being combined with the flexible joint, meeting the need for obstacle avoidance in confined spaces. Furthermore, its rigid-flexible coupled feed joint can achieve a small-distance feed of 0-5cm. After determining the grasping posture, it can quickly approach the target fruit even in confined spaces, whereas traditional agricultural robotic arms require more complex joint movements and may collide due to space limitations. Meanwhile, it employs a pneumatically driven bellows for telescopic extension and retraction, resulting in a fast response speed. Furthermore, it utilizes six metal optical axes for limiting movement, enhancing the bending stiffness of the joint. Compared to traditional agricultural robotic arms, this joint is lighter while achieving the same functionality. Moreover, the joint type and range of motion of the three-joint series are optimized for the harvesting method: after locating near the target fruit, it uses a combination of rigid wrist and flexible joints to flip and avoid obstacles in front of the fruit, and then uses the feed joint to advance a short distance to approach the target fruit. In summary, this invention provides a rigid-flexible coupling agricultural harvesting robotic arm joint suitable for apple harvesting. It possesses high-precision positioning, large-angle flipping, and short-distance feed capabilities, while also boasting advantages such as small size, high flexibility, and strong passive safety. It can be used in the structure of rigid robotic arms, giving agricultural harvesting robotic arms greater mobility, obstacle avoidance capabilities, and collision protection, enabling efficient and dexterous harvesting operations in confined and complex environments.

[0025] In summary, compared with the prior art, the present invention significantly improves the obstacle avoidance capability of the robotic arm joints through the design of flexible bending joints, thereby improving the overall harvesting success rate and harvesting efficiency of the robotic arm.

[0026] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A rigid-flexible coupling joint for an agricultural harvesting robotic arm, characterized in that, include: The rigid-flexible coupling feed joint, the flexible bending joint, and the rigid wrist joint are fixedly connected in sequence, wherein the rigid wrist joint is fixedly connected to the external rigid robotic arm through a flange. The rigid-flexible coupling feed joint includes: a telescopic end cap, a feed fixing bracket, a bellows, and a threaded column, wherein: the telescopic end cap is connected to an external rigid robotic arm, one end of the bellows is connected to the telescopic end cap, and the other end is fixedly connected to one end of the threaded column, and the other end of the threaded column is slidably disposed in the feed fixing bracket, and the bellows is extended and retracted by air pressure. The rigid wrist joint includes: a flip motor support mechanism and a rotary motor support mechanism that are arranged opposite to each other and mesh with each other through a gear set, wherein: the flip motor support mechanism includes: an upper motor support and a horizontally arranged flip servo; the rotary motor support mechanism includes: a lower motor support and a vertically arranged rotary servo. The flexible bending joint is driven by three servo motors to achieve bending of 0~30° in all directions. The flexible bending joint includes a motor bracket and a flexible structure mounted thereon, wherein the flexible structure is equipped with a ventilation hose with a pneumatic connector.

2. The rigid-flexible coupling joint of the agricultural harvesting robotic arm according to claim 1, characterized in that, The gear set includes: a pair of upper cylindrical gears mounted on the upper motor bracket, a pair of lower cylindrical gears meshing with them and mounted on the lower motor bracket, a cylindrical gear connected to the rotary servo, and a lower flange mounted under the lower motor bracket. Any one of the upper cylindrical gears is connected to the output shaft of the tilting servo, and the cylindrical gear meshes with the lower flange.

3. The rigid-flexible coupling joint of the agricultural harvesting robotic arm according to claim 2, characterized in that, The rotary servo drives the cylindrical gear to rotate, and through gear meshing, the lower flange and the upper mechanism connected to it rotate a full circle. The flip servo drives the lower cylindrical gear to rotate, and through the meshing of the two upper cylindrical gears with the corresponding lower cylindrical gears, the upper motor bracket and its fixed connection part can achieve a large-angle flip of -15° to 160°. The joint adopts an asymmetrical flip design, and the range of motion is adapted to the orientation characteristics of obstacles such as leaves in the dwarf dense planting standard apple orchard.

4. The rigid-flexible coupling joint of the agricultural harvesting robotic arm according to claim 1, characterized in that, The flexible structure is manufactured using flexible materials such as silicone through 3D printing.

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