An underactuated kiwifruit picking manipulator based on origami buckling structure

Abstract

This invention discloses an underactuated kiwifruit harvesting robotic arm based on an origami buckling structure, belonging to the field of agricultural machinery and equipment technology. It includes a base drive module, a telescopic arm module, a sequential bistable buckling end effector, a wire transmission system, and a vision recognition system. The telescopic arm adopts a 4D-printed origami structure, compressing under the tension of the wire and automatically rebounding after the wire relaxes due to elastic potential energy. The elastic sheet of the gripper in the sequential bistable buckling end effector closes due to the reaction force from fruit contact, triggering a wrist joint twist by causing a jump in the elastic sheet of the wrist, thus separating the fruit stem. When the telescopic arm begins to compress, the elastic sheet is forcibly pulled back, and the gripper opens to release the fruit. The underactuated kiwifruit harvesting robotic arm based on an origami buckling structure provided by this invention has advantages such as lightweight end effector, low cost, and low damage rate, and is suitable for harvesting fruits requiring twisting.

Description

Technical Field

[0001] This invention relates to the field of agricultural machinery and equipment technology, and in particular to an underactuated kiwifruit harvesting robotic arm based on an origami buckling structure. Background Technology

[0002] Kiwifruit, a widely cultivated cash crop, is still primarily harvested manually. While manual harvesting allows for precise operations, it is constrained by labor shortages and suffers from significant drawbacks such as high labor intensity, low efficiency, and high costs. With the deepening development of agricultural mechanization and intelligentization, mechanized harvesting equipment has become a core research direction for addressing these challenges.

[0003] Currently, robotic harvesting equipment based on visual recognition and robotic arms is the mainstream research direction in the field of automated harvesting. However, existing harvesting robotic arms and their end effectors are usually designed independently and operate in a decoupled manner. Each joint needs to be driven and controlled independently, which not only leads to complex system control logic but also has key performance defects: the centralized arrangement of multi-degree-of-freedom drive devices of the end effector significantly increases the overall weight of the end effector, directly increasing the load on the front joints of the robotic arm, thereby reducing the system's dynamic response speed and positioning accuracy, while also significantly increasing energy consumption and equipment manufacturing costs.

[0004] Further analysis of the actual operational requirements of kiwifruit harvesting reveals that the harvesting process does not require all actions to be decoupled. Instead, it follows a clear "sequential logic"—first, a visual recognition system and a mobile platform are needed to achieve precise positioning and posture adjustment of the fruit by the end effector. Then, the robotic arm and end effector perform subsequent actions such as grasping and separating (e.g., twisting off the fruit stem). These actions have a sequential order and can be triggered sequentially. Based on this operational characteristic, the existing design approach of multi-drive decoupled control for robotic arms and end effectors is essentially a redundant configuration of drive resources, directly leading to problems such as large end-effector weight and complex control. Summary of the Invention

[0005] The purpose of this invention is to provide an underactuated kiwifruit harvesting robotic arm based on an origami buckling structure, which solves the problems of large weight and complex structure of the end effector of existing harvesting equipment.

[0006] To achieve the above objectives, the present invention provides an underactuated kiwifruit harvesting robotic arm based on an origami buckling structure, comprising a base drive module, a telescopic arm module, a sequential bistable buckling end effector, a wire transmission system, and a vision recognition system; the base drive module is fixed to the mobile platform and serves as the power output starting point, and is connected to the telescopic arm module through the wire transmission system; the telescopic arm module is equipped with a sequential bistable buckling end effector at its top; the vision recognition system is independently installed on the mobile platform and is linked to the controller of the base drive module through signal transmission;

[0007] The base drive module consists of a drive motor, a wire drum, and a base support, providing power for the robotic arm's compression. The base support is fixed to the moving platform, and the drive motor is fixed to a preset motor mounting position on the base support. The motor shaft of the drive motor is connected to the wire drum, and the rotation of the drive motor synchronously drives the wire drum to rotate, realizing the winding and unwinding of the wire. The drive motor can be a stepper motor, servo motor, or DC motor; the appropriate motor type should be selected according to the harvesting accuracy requirements.

[0008] The mobile platform has a Cartesian frame; the Cartesian frame's bearing surface has reserved mounting positions for robotic arms, and the base drive module of each robotic arm is fixed to the platform's preset mounting holes by bolts;

[0009] The sequential bistable flexion terminal actuator is composed of a wrist joint bistable flexion module and a flexible gripper bistable flexion module connected together; the lower end of the wrist joint bistable flexion module is connected to the telescopic arm module, and the upper end is connected to the flexible gripper bistable flexion module;

[0010] The wrist bistable flexion module consists of a support and a wrist elastic plate, which are placed symmetrically at the top of the robotic arm module.

[0011] The flexible gripper bistable flexion module consists of a flexible finger body and a gripper elastic sheet; the bottom of the flexible finger body is fixed to the outer periphery of the gripper elastic sheet; the flexible finger body consists of a flexible skeleton and a soft finger pad, with the soft finger pad covering the outside of the flexible skeleton.

[0012] When the elastic plate at the center of the gripper contacts the fruit, the fruit's reaction force triggers the elastic plate to jump, causing the gripper to close. Simultaneously, this causes the elastic plate at the wrist to jump, generating a torsional motion around a direction perpendicular to the robotic arm's axis. This rotation of the entire gripper achieves torsional separation of the fruit stem. The flexible finger body consists of a flexible skeleton and soft finger pads. The flexible skeleton provides support, while the soft finger pads, in contact with the fruit, provide cushioning and protection. The flexible skeleton can be printed using thermoplastic polyurethane or silicone material, with embedded flexible springs providing rebound force. The soft finger pads are made of low-hardness silicone material, and the surface can have friction textures or micro-suction cup structures to enhance the gripping effect. The front end of the flexible finger body is rounded to reduce the impact of surrounding leaves on the harvesting process, achieving more precise fruit picking.

[0013] The wire transmission system includes a main wire and a return cable. The main wire is fixed to the outside of the hollow axial channel, with one end fixed to the wire drum and the other end connected to the top of the telescopic arm module. One end of the return cable is connected to the wrist elastic plate, and the other end is connected to the main wire. The wire can be made of high-strength steel wire rope, carbon fiber rope, or Kevlar fiber rope to ensure transmission reliability.

[0014] The main steel wire and reset cable constitute the robotic arm's reset mechanism: Before the robotic arm descends, as the main steel wire begins to tighten, the reset cable mechanically pulls the wrist and gripper elastic plates back to their initial trigger state sequentially or simultaneously, causing the wrist joint to return to center and the gripper to open. The reset mechanism is isolated from the picking trigger mechanism, ensuring that changes in the tension of the steel wire during picking will not accidentally trigger the reset action.

[0015] Preferably, the telescopic arm module is integrally formed from multiple layers of origami units using 4D printing technology, employing a composite compression-twist origami structure. Compression and rebound are achieved through structural elasticity. The hard and soft phase material areas of each origami unit alternately combine to form a continuous hollow axial channel running through the entire telescopic arm. The hard phase material areas form crease reinforcement ribs, providing structural strength, while the soft phase material areas form deformable panels, providing flexible deformation capabilities. The hard phase material can be thermoplastic materials such as polylactic acid and polycarbonate, while the soft phase material can be elastic materials such as thermoplastic polyurethane and silicone. The telescopic arm module possesses structural elasticity; when compressed under the tension of the steel wire, it rebounds to its original shape after the wire relaxes, relying on its own elastic potential energy. Integral forming using 4D printing technology reduces assembly steps and the number of parts, lowering manufacturing costs.

[0016] Preferably, the visual recognition system includes a depth camera, an image processing module, and a positioning algorithm module. The depth camera is fixed to the top of the telescopic arm module, while the image processing module and positioning algorithm module are integrated into the control system of the mobile platform and connected to the depth camera for signal interaction. The depth camera can be a binocular camera, a structured light camera, etc., and is mounted at a suitable position on the mobile platform via an adjustable angle base for identifying and locating target fruits. The visual recognition scheme of the system includes color segmentation, mask generation, target extraction, and spatial localization. Color segmentation involves acquiring images of ripe fruits under different lighting conditions and performing color analysis to obtain the optimal threshold range. Target color region detection is achieved by limiting the threshold range. Mask generation involves traversing each pixel in the image and checking whether each pixel meets the set color threshold conditions to form a fruit mask image. Target extraction first performs morphological operations: opening operations remove noise, and closing operations fill holes. Suitable recognition objects are selected by adjusting the minimum area and minimum aspect ratio thresholds. Spatial localization calculates the fruit's position in three-dimensional space using parallax and camera parameters. Multi-frame fusion improves robustness and enhances the accuracy of fruit spatial positioning.

[0017] Therefore, the present invention employs the above-mentioned underactuated kiwifruit harvesting robotic arm based on origami buckling structure, which has the following beneficial effects:

[0018] (1) Through structural innovation, this invention adopts a 4D-printed origami structure and a sequential buckling mechanism to achieve sequential movements of extension, contraction, and torsion. Only a single drive source is needed to complete the lifting and lowering of the robotic arm and the end-effector gripping and torsion movements. Compared with the traditional multi-motor solution, this invention significantly reduces the number of drive sources, thereby reducing the end-effector weight, structural complexity, control difficulty, and system cost.

[0019] (2) The end effector of the present invention adopts a lightweight design. Both the bistable buckling elastic sheet and the flexible gripper are made of lightweight materials, which greatly reduces the overall weight, effectively reduces the load on the end of the robotic arm, and improves the dynamic performance and positioning accuracy of the system. The flexible gripper uses low-hardness silicone fingertips with friction texture or micro-suction cup structure on the surface. The front end of the finger body adopts an arc-shaped design, which can minimize damage to the fruit skin while ensuring stable gripping and reduce the impact of surrounding leaves on harvesting.

[0020] (3) The bistable buckling mechanism of the present invention is driven entirely by the mechanical force generated by fruit contact, realizing true passive adaptive picking without the need for complex feedback systems such as force sensors and position sensors, reducing the failure rate and improving reliability and adaptability;

[0021] (4) This invention achieves efficient harvesting through the guidance of a visual recognition system and the precise control of a sequential bistable buckling mechanism. The single harvesting cycle time is short, the harvesting speed is fast, and the harvesting success rate is high.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 This is an overall structural diagram of an underactuated kiwifruit harvesting robotic arm based on origami buckling structure according to the present invention;

[0024] Figure 2 This is a schematic diagram of steady state A of the sequential bistable buckling end effector of the present invention;

[0025] Figure 3 This is a schematic diagram of steady state B of the sequential bistable buckling end effector of the present invention;

[0026] Figure 4 This is a schematic diagram of the telescopic arm of the present invention in its extended state;

[0027] Figure 5 This is a schematic diagram of the telescopic arm in the compressed state of the present invention;

[0028] Figure 6 This is a flowchart of the working cycle of the present invention.

[0029] Figure Labels

[0030] 1. Base drive module; 1.1 Drive motor; 1.2 Wire reel; 1.3 Base support; 2. Telescopic arm module; 2.1 Folding unit; 2.2 Hollow axial channel; 2.3 Hard phase material area; 2.4 Soft phase material area; 3. Sequential bistable flexion end effector; 3.1 Wrist joint bistable flexion module; 3.1.1 Support component; 3.1.2 Wrist elastic sheet; 3.2 Flexible gripper bistable flexion module; 3.2.1 Flexible finger body; 3.2.2 Flexible skeleton; 3.2.3 Soft fingertip; 3.2.4 Grip elastic sheet; 4. Wire transmission system; 4.1 Main wire; 4.2 Reset cable; 5. Visual recognition system. Detailed Implementation

[0031] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0032] like Figure 1 As shown, the overall structure of an underactuated kiwifruit harvesting robotic arm based on origami buckling structure includes a base drive module 1, a telescopic arm module 2, a sequential bistable buckling end effector 3, a wire transmission system 4, and a vision recognition system 5. The base drive module 1 is fixed to the mobile platform and serves as the power output starting point. It is connected to the telescopic arm module 2 through the wire transmission system 4. The telescopic arm module 2 is equipped with the sequential bistable buckling end effector 3 at its top. The vision recognition system 5 is independently installed on the mobile platform and is linked to the controller of the base drive module 1 through signal transmission.

[0033] The base drive module 1 includes a drive motor 1.1, a wire drum 1.2, and a base support 1.3. The base support 1.3 is fixed on the moving platform, the drive motor 1.1 is fixed in the preset motor mounting position of the base support 1.3, the motor shaft of the drive motor 1.1 is connected to the wire drum 1.2, and the rotation of the drive motor 1.1 synchronously drives the wire drum 1.2 to rotate.

[0034] like Figure 5As shown, the telescopic arm module 2 is integrally formed from multiple layers of origami units 2.1 using 4D printing technology. It employs a composite compression-twist origami structure, relying on structural elasticity to achieve compression and rebound. The hard phase material area 2.3 and soft phase material area 2.4 of each origami unit alternately combine to form a continuous hollow axial channel 2.2 that runs through the entire telescopic arm. The hard phase material area 2.3 forms crease reinforcement ribs to provide structural strength, while the soft phase material area 2.4 forms deformable panels to provide flexible deformation capabilities. The hard phase material can be thermoplastic materials such as polylactic acid and polycarbonate, while the soft phase material can be elastic materials such as thermoplastic polyurethane and silicone. The telescopic arm module 2 possesses structural elasticity; when compressed under the tension of the steel wire, it rebounds and returns to its original shape after the steel wire relaxes, relying on its own elastic potential energy. Integral forming using 4D printing technology reduces assembly steps and the number of parts, lowering manufacturing costs.

[0035] like Figure 2 As shown, the sequential bistable flexion terminal actuator 3 includes a wrist joint bistable flexion module 3.1 and a flexible bistable flexion gripper module 3.2; the lower end of the wrist joint bistable flexion module 3.1 is connected to the telescopic arm module 2, and the upper end is connected to the flexible gripper bistable flexion module 3.1.

[0036] The wrist joint bistable flexion module 3.1 includes a support 3.1.1 and a wrist elastic sheet 3.1.2; the two are placed symmetrically along the long side of the base support.

[0037] The flexible gripper bistable flexion module 3.2 is composed of a flexible finger body 3.2.1 and a gripper elastic sheet 3.2.4; the bottom of the flexible finger body 3.2.1 is fixed to the outer periphery of the gripper elastic sheet 3.2.4; the flexible finger body 3.2.1 is composed of a flexible skeleton 3.2.2 and a soft finger pad 3.2.3, with the soft finger pad 3.2.3 covering the outside of the flexible skeleton 3.2.2.

[0038] The wire transmission system 4 includes a main wire 4.1 and a return cable 4.2; as... Figure 4 As shown, the main steel wire 4.1 is fixed to the outside of the hollow axial channel 2.2, with one end fixed to the steel wire drum 1.2 and the other end connected to the top of the telescopic arm module 2; the reset cable 4.2 is connected at one end to the wrist elastic plate 3.1.2 and at the other end to the support member 3.1.1. The steel wire can be made of high-strength steel wire rope, carbon fiber rope or Kevlar fiber rope to ensure transmission reliability.

[0039] The visual recognition system 5 includes a depth camera, an image processing module, and a positioning algorithm module. The depth camera is fixed to the top of the telescopic arm module 2. The image processing module and the positioning algorithm module are integrated into the control system of the mobile platform and connected to the depth camera for signal interaction. The depth camera can be a binocular camera, a structured light camera, etc., and is installed at a suitable position on the mobile platform via an adjustable angle base for identifying and locating target fruits. The visual recognition scheme includes color segmentation, mask generation, target extraction, and spatial positioning. Color segmentation obtains the optimal threshold range by acquiring images of ripe fruits under different lighting conditions and performing color analysis. The target color region is detected by limiting the threshold range. Mask generation forms a fruit mask image by traversing each pixel in the image and checking whether each pixel meets the set color threshold conditions. Target extraction first performs morphological operations: opening operations remove noise, and closing operations fill holes. The appropriate recognition object is selected by adjusting the minimum area and minimum aspect ratio thresholds. Spatial positioning calculates the position of the fruit in three-dimensional space using parallax and camera parameters. Multi-frame fusion is used to improve robustness and increase the accuracy of the fruit's spatial position.

[0040] When this device is operating in the orchard, the visual recognition system 5 identifies mature fruits on the trees, and through subsequent analysis, obtains the spatial coordinates of the fruits. The drive motor 1.1 winds up the steel wire, and the telescopic arm module 2, through the steel wire transmission system 4, resets the sequential bistable buckling end actuator 3 to a ready state with the gripper open and the wrist joint aligned, and then lowers it. Subsequently, the drive motor 1.1 stops or reverses, the steel wire loosens, and the telescopic arm rises to the fruit position due to elastic rebound. The elastic plate 3.2.4 at the center of the gripper contacts the fruit, and the fruit's reaction force triggers a jump in the elastic plate 3.2.4, such as... Figure 3 As shown, the gripper closes and grasps the fruit, while simultaneously causing the elastic plate 3.1.2 of the wrist to jump, generating a torsional motion around a direction perpendicular to the axis of the robotic arm, causing the gripper to rotate as a whole, thus achieving the torsional separation of the fruit stalk.

[0041] like Figure 6 As shown, the harvesting process for kiwifruit includes the following steps:

[0042] Step 1: Integrate and deploy the kiwifruit harvesting robotic arm, which utilizes a folding mechanism to achieve single-motor driven multi-degree-of-freedom sequential motion, with the mobile platform. The deployment method is as follows: The mobile platform has a Cartesian frame, providing movement in two directions. The frame's bearing surface has pre-reserved mounting positions for the robotic arms. The base drive module 1 of each robotic arm is fixed to the platform's pre-set mounting holes with bolts, ensuring a secure connection. Initially, the robotic arm can be in any position. Furthermore, the mobile platform, equipped with a Cartesian frame, can adapt to the complex terrain of the orchard, ensuring the stability of the device's movement.

[0043] Step 2: After system startup, the controller first starts the drive motor 1.1, which drives the wire reel 1.2 to rotate and wind up the main wire 4.1. The main wire 4.1 is pulled to the top of the telescopic arm through the hollow axial channel 2.2 of the telescopic arm. Under the tension of the wire, the telescopic arm module 2 overcomes its own structural elasticity and generates axial compression, causing the entire robotic arm to descend to its lowest position within the working range. Before the telescopic arm descends, the reset mechanism forcibly pulls the wrist elastic plate 3.1.2 and the gripper elastic plate 3.2.4 to return to their initial untriggered state sequentially or simultaneously. The wrist elastic plate 3.1.2 rebounds, returning the wrist joint to a position parallel to the robotic arm axis, and the gripper elastic plate 3.2.4 rebounds, opening the flexible gripper. At this point, the robotic arm enters the ready state, located in the lowest position, with the gripper open and the wrist joint centered, ready to begin harvesting operations.

[0044] Step 3: After the mobile platform reaches the fruit tree work area, it pauses, and the visual recognition system 5 starts working. The depth camera is installed in a suitable position with its lens facing the fruit tree canopy. The camera identifies ripe fruit through the image recognition system, calculates the fruit's three-dimensional coordinates, and transmits the coordinate data to the controller. Furthermore, the image processing module can run a deep learning-based recognition algorithm to improve recognition accuracy, enabling it to identify fruits of different ripeness levels and degrees of occlusion. If a fruit meeting the picking conditions is identified, the controller compares the fruit coordinates with the robotic arm's working range; if within the range, a picking command is triggered.

[0045] Step 4: After the picking command is triggered, the controller calculates the required lifting distance based on the fruit's three-dimensional coordinates and the current state of the robotic arm. Subsequently, the drive motor 1.1 stops or reverses its rotation, the wire reel 1.2 releases the main wire 4.1, and the wire tension disappears. After the telescopic arm module 2 loses external compressive force, it automatically rebounds using the elastic potential energy stored in the folding unit 2.1 during compression. The folding unit 2.1 returns from the compressed state to the extended state, and the robotic arm rises as a whole towards the target fruit located at a high position. The robotic arm continues to rise until the gripper approaches the target fruit.

[0046] Step 5: When the elastic sheet 3.2.4 of the claw contacts the fruit surface, the fruit generates a reaction force on the claw, initiating a sequential triggering action. The key innovation of this embodiment is that the closing of the claw and the twisting of the wrist are naturally and sequentially triggered through a bistable buckling mechanism, without the need for other transmission mechanisms. When the contact force gradually increases to the energy barrier threshold of the elastic sheet 3.2.4, the elastic sheet 3.2.4 undergoes a jump, rapidly transitioning from one stable state to another. The jump of the elastic sheet 3.2.4 causes several flexible fingers 3.2.1 of the flexible claw 3.2 to move towards the center, realizing the claw closing action. The flexible fingers 3.2.1 wrap around and grasp the fruit, while simultaneously causing the elastic sheet 3.1.2 of the wrist to jump, rapidly transitioning from an initial stable state to another stable state. The jump of the elastic thin plate 3.1.2 on the wrist causes the wrist joint to generate a torsional motion about a direction perpendicular to the axis of the robotic arm. This torsional motion, combined with the gripping force of the gripper, applies a torsional torque to the fruit stem, thereby separating the fruit stem. The entire sequence triggering process is a purely mechanical passive triggering mechanism, driven entirely by the reaction force generated by the contact of the fruit, realizing an automatic and reliable "grasp first, then twist" action sequence.

[0047] Step Six: After the second-level trigger is completed, the fruit is stably held by the claw, and the fruit stalk separates under the torsional torque of the wrist joint. At this point, the fruit has been successfully picked and is stably held.

[0048] Step 7: After successful fruit separation, the controller restarts the drive motor 1.1, causing the wire drum 1.2 to rotate and wind up the main wire 4.1. Under the tension of the main wire 4.1, the telescopic arm module 2 overcomes its own elasticity and generates axial compression, causing the entire robotic arm to descend. Before the telescopic arm descends, the reset cable 4.2 tightens as the main wire 4.1 tightens, forcibly pulling the wrist elastic plate 3.1.2 and the gripper elastic plate 3.2.4 back to their initial state. The wrist elastic plate 3.1.2 returns the wrist joint to its normal position, and the gripper elastic plate 3.2.4 opens the gripper. As the gripper opens, the fruit is released under gravity and falls into the fruit collection device below. The internal slope of the fruit collection device is an arc-shaped slope, allowing the fruit to slide smoothly down the arc-shaped slope to the bottom of the fruit collection device, improving the space utilization of the fruit collection device.

[0049] Step 8: After the fruit is released and collected, the robotic arm returns to the ready state, positioned in a low position with its gripper open and wrist joint centered, ready for the next harvest. The controller sends a signal to the mobile platform, which continues moving according to the harvesting strategy. If there are still other ripe fruits on the same tree, the platform can travel only a certain distance before pausing again and repeating steps 3 to 7 to achieve continuous harvesting of multiple fruits from the same tree. If the current tree has been harvested, the platform continues to the next tree, repeating the entire harvesting process to achieve cyclical operation.

[0050] It should be noted that this embodiment is only illustrative of kiwifruit harvesting. In other possible implementations, developers can make adjustments based on the characteristics of different fruits. For example, for grapes, the flexible gripper can be replaced with a small-sized multi-finger structure, and the energy barrier of the gripper's elastic sheet 3.2.4 can be adjusted to reduce the clamping force and avoid damaging the fruit. For cherries, the total length of the telescopic arm can be shortened or the number of folding unit layers 2.1 can be reduced to improve positioning accuracy. For tomatoes, the soft fingertips 3.2.3 can be made of a lower-hardness silicone material to increase the contact area with the fruit, disperse pressure, and avoid squeezing the fruit. This embodiment does not constitute a limitation.

[0051] Therefore, this invention employs an underactuated kiwifruit harvesting robotic arm based on a paper-folding buckling structure. By combining a 4D-printed paper-folding structure with a bistable buckling mechanism, it innovatively utilizes a passive triggering mechanism to achieve "single-drive, passive triggering, and sequential action" for fruit harvesting. The closing of the gripper is triggered by the fruit contact reaction force, causing the elastic sheet of the gripper to jump. The twisting of the wrist is achieved by simultaneously triggering the elastic sheet of the wrist. The entire process is naturally and sequentially triggered by the bistable buckling mechanism, without the need for other transmission mechanisms. This invention effectively solves the problems of heavy, complex, difficult-to-control, high-energy-consumption, and high-cost end effectors in traditional harvesting equipment. This device features a lightweight end effector, simplified structure, easy control, low energy consumption, low cost, high reliability, low fruit damage rate, and high harvesting success rate. It can significantly improve orchard harvesting efficiency, reduce labor costs, and has good application prospects and promotional value.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A subactuated kiwifruit harvesting robotic arm based on origami buckling structure, characterized in that, It includes a base drive module, a telescopic arm module, a sequential bistable buckling end effector, a wire drive system, and a vision recognition system. The base drive module is fixed to the mobile platform and connected to the telescopic arm module through the wire drive system. The telescopic arm module is equipped with a sequential bistable buckling end effector at its top. The vision recognition system is independently installed on the mobile platform and is linked to the controller of the base drive module through signal transmission. The base drive module consists of a drive motor, a wire drum, and a base support. The base support is fixed on the moving platform, the drive motor is fixed in the preset motor mounting position on the base support, the motor shaft of the drive motor is connected to the wire drum, and the rotation of the drive motor synchronously drives the wire drum to rotate. The mobile platform has a Cartesian frame; the Cartesian frame's bearing surface has reserved mounting positions for robotic arms, and the base drive module of each robotic arm is fixed to the platform's preset mounting holes by bolts; The sequential bistable flexion terminal actuator is composed of a wrist joint bistable flexion module and a flexible gripper bistable flexion module connected together; the lower end of the wrist joint bistable flexion module is connected to the telescopic arm module, and the upper end is connected to the flexible gripper bistable flexion module; The wrist joint bistable flexion module consists of a support and a wrist elastic sheet, which are placed symmetrically at the top of the telescopic arm module. The flexible gripper bistable flexion module consists of a flexible finger body and a gripper elastic sheet; the bottom of the flexible finger body is fixed to the outer periphery of the gripper elastic sheet; the flexible finger body consists of a flexible skeleton and a soft finger pad, with the soft finger pad covering the outer side of the flexible skeleton. The wire drive system includes a main wire and a reset cable; the main wire is fixed to the outside of the hollow axial channel, one end is fixed to the wire drum, and the other end is connected to the top of the telescopic arm module; one end of the reset cable is connected to the wrist elastic plate, and the other end is connected to the main wire. During the harvesting process, the elastic plate in the center of the hand gripper contacts the fruit. The reaction force of the fruit triggers the elastic plate of the hand gripper to jump, and the hand gripper closes to grasp the fruit. At the same time, it drives the elastic plate of the wrist to jump, generating a torsional motion around a direction perpendicular to the axis of the robotic arm. This causes the entire hand gripper to rotate, achieving the torsional separation of the fruit stalk.

2. The underactuated kiwifruit harvesting robotic arm based on origami buckling structure according to claim 1, characterized in that, The telescopic arm module is integrally formed by multi-layer origami units using 4D printing technology; the hard phase material area and soft phase material area of ​​each origami unit are alternately compounded to form a continuous hollow axial channel.

3. The underactuated kiwifruit harvesting robotic arm based on origami buckling structure according to claim 1, characterized in that, The visual recognition system includes a depth camera, an image processing module, and a positioning algorithm module. The depth camera is fixed to the top of the telescopic arm module, and the image processing module and positioning algorithm module are integrated into the control system of the mobile platform and connected to the depth camera for signal interaction.

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