A soft robot for picking fruit

Abstract

The application discloses a kind of soft robots for picking fruit, including soft manipulator, soft robotic arm, controller, first wire driving device, second wire driving device, mobile base, vision sensor, fiber grating sensor mounted on soft manipulator, first wire driving device is transmission connection with soft manipulator by several first control ropes, and second wire driving device is transmission connection with soft robotic arm by several second control ropes.By adopting the composite structure of soft manipulator and soft robotic arm, cooperate with wire driving device to independently control gripping and bending expansion, and integrate vision sensor and fiber grating sensor to realize target identification and force feedback, the compliant lossless gripping of small berry and spatial multi-degree-of-freedom attitude adjustment are realized.

Description

Technical Field

[0001] This invention relates to a soft robot for harvesting fruit, belonging to the technical field of agricultural assisted harvesting devices. The classification number for this invention is B25J9. Background Technology

[0002] With the acceleration of agricultural modernization, the large-scale cultivation of small berries such as cherry tomatoes and strawberries has created an urgent need for automated harvesting. Due to the thin and fragile skin, slender stems, and diverse growth postures of these fruits, the end effector for harvesting needs to possess both compliant gripping capabilities and multi-degree-of-freedom spatial adaptability. Currently, the end effectors of small fruit harvesting robots are mainly divided into two categories: rigid claws and flexible claws.

[0003] Chinese patent CN109773823A discloses an apple-picking robotic hand. It employs two-jointed fingers, which are fixed to a palm plate by helical springs. Each finger consists of a proximal phalanx, a distal phalanx, a drive link, and a driven link. A tendon cord on the drive link passes through the palm plate and is vertically fixed to a lifting disc. The other end of the lifting disc is connected to a drive motor via the tendon cord. A single motor simultaneously drives all three fingers to complete the enveloping grasp of the apple. This design achieves the grasping action through tendon cord transmission and helical spring reset, resulting in a relatively simple structure and low cost. However, the fingers of this robotic arm are an underactuated structure combining rigid linkages and springs, resulting in high overall rigidity. Although the inner side is covered with soft silicone pads, it is still prone to causing local stress concentration when grasping fruits with tender skins, such as cherry tomatoes, leading to fruit damage. Its finger joints are rigid hinges with limited degrees of freedom, making it unsuitable for small fruits with diverse growth postures and changing spatial positions, and difficult to achieve adaptive envelope grasping. In addition, the device is only designed for apple picking and does not involve compliant motion control of the robotic arm, lacking the ability to adjust postures with multiple degrees of freedom in complex plant environments.

[0004] Chinese patent CN203896769U discloses an adaptive flexible fruit and vegetable harvesting end effector. It employs four fingers, each consisting of three rigid knuckles and a finger-root slider connected by screws. The fingers are connected to fixed and movable pulleys via tendon ropes. A single motor drives a ball screw to move the movable pulley frame, synchronously pulling the four fingers to achieve an enveloping grasp. Tension springs then reset the fingers. This design achieves automatic balancing of the grasping force of the four fingers through the movable pulley mechanism, resulting in a compact structure and low cost. However, the fingers of this end effector still have a rigid linkage hinge structure, lacking flexible cushioning on the knuckle surface. This poses a risk of localized stress concentration and skin damage when grasping thin-skinned fruits such as cherry tomatoes. Furthermore, the finger reset relies on multiple tension springs, which are prone to fatigue and relaxation after prolonged use, affecting grasping accuracy and response speed. Additionally, this device only focuses on the end effector itself and does not address the flexible motion control of the robotic arm, making it unable to achieve flexible spatial obstacle avoidance and precise positioning in harvesting environments with dense vegetation and diverse fruit postures. Summary of the Invention

[0005] Purpose of the invention: To address the shortcomings of existing technologies, this invention provides a soft robot for picking fruit, which uses a soft manipulator and a soft robotic arm driven by a string to achieve smooth and non-destructive grasping and multi-degree-of-freedom posture adjustment.

[0006] Technical solution: A soft robot for fruit picking, comprising a soft manipulator, a soft manipulator arm, a controller, a first-wire drive unit, a second-wire drive unit, a mobile base, a vision sensor, and a fiber optic grating sensor mounted on the soft manipulator. One end of the soft robotic arm is mounted on a mobile base, and the other end is connected to the soft robotic hand via a connecting component. The first wire drive device and the second wire drive device are mounted on the mobile base. The first line drive device is connected to the soft robotic arm via a plurality of first control ropes, and the second line drive device is connected to the soft robotic arm via a plurality of second control ropes. The visual sensor is mounted on the connection assembly and is used to identify and locate the target fruit; The controller is connected to the first line drive device, the second line drive device, the vision sensor, and the fiber optic grating sensor, respectively.

[0007] This invention employs a composite structure of a soft robotic hand and a soft robotic arm, with a first and a second line drive device independently controlling the gripping of the robotic hand and the bending and extension of the robotic arm. It also integrates a vision sensor and a fiber optic grating sensor to achieve target recognition and gripping force feedback, enabling compliant and non-destructive gripping of small berries and spatial multi-degree-of-freedom posture adjustment. This solves the problems of existing rigid robotic hands that easily damage fruits and have limited degrees of freedom, as well as pneumatic flexible arms that are prone to air leakage, aging, and large size outdoors.

[0008] In a preferred embodiment, in order to achieve effective separation and guidance of the control ropes and avoid different control ropes from tangling or rubbing against each other during transmission, the connecting assembly includes a flange and a connecting plate, wherein the flange is provided with a first central hole and circumferentially distributed first mounting holes. The upper end face of the connecting plate is connected to the bottom end of the soft robotic arm, and the lower end face of the connecting plate is connected to the flange. A second center hole coaxial with the first center hole is opened on the connecting plate, and the lower end face of the flange is connected to the end of the soft robotic arm. One end of the first control rope is connected to the first wire drive device, and the other end passes through the inside of the soft robotic arm, the first central hole, and the second central hole and is connected to the soft robotic hand. One end of the second control rope is connected to the second wire drive device, and the other end passes through the inside of the soft robotic arm and the first mounting hole and is connected to the bottom of the connecting plate.

[0009] By setting coaxial first and second center holes as channels for the first control rope, and setting circumferentially distributed first mounting holes as fixing and turning points for the second control rope, spatial separation and orderly routing of the two types of control ropes at the connection between the robot and the robotic arm are achieved, ensuring the smoothness and reliability of the transmission process.

[0010] In a preferred embodiment, in order to achieve adaptive grasping of fruits of different sizes and shorten the grasping response time, the soft robotic hand includes at least four soft fingers. Each soft finger has a first channel and a second channel arranged longitudinally inside. The first channel and the second channel are distributed sequentially from the inside to the outside along the diameter direction. Each first control rope passes through the first center hole and the second center hole and enters the first channel and the second channel of each soft finger, until it connects with the inside of the tip of the soft finger.

[0011] By sequentially opening a first channel and a second channel along the diameter direction inside each soft finger, the bending and opening of the finger can be controlled respectively. When the inner cord is relaxed, the outer cord is tightened. This not only allows the outer cord to actively prompt the finger to return to its initial state, but also allows for flexible adjustment of the gripping range, enabling fast and stable gripping of fruits of different sizes.

[0012] In a preferred embodiment, to enable independent guidance and separation of the two first control ropes within the same soft finger, the lower end face of the connecting plate is provided with a number of branching grooves corresponding to the soft finger, and a first boss coaxially connected to the second central hole is installed thereon. The first boss is installed in the first central hole. The connecting plate is provided with a first transition hole and a second transition hole corresponding to the first channel and second channel of each soft finger, respectively. One end of each branching groove is connected to the second central hole, and the other end is connected to the first transition hole and the second transition hole in sequence. Each first control rope enters the second central hole through the inside of the first boss, enters the corresponding branching groove from the second central hole, and is branched by the branching groove before entering the corresponding first channel and second channel.

[0013] By setting a branch groove and a first boss on the lower end face of the connecting plate, the first control rope enters different channels of the finger after passing through the first boss, the second center hole, the branch groove and the transition hole in sequence. This ensures that each control rope has an independent routing path, avoids interference and friction between ropes, and improves the accuracy and stability of gripping control.

[0014] In a preferred embodiment, to prevent interference or entanglement between two control cords in the same soft finger within the dividing groove, the height of the dividing groove between the first transition hole and the second transition hole is lower than the height of the dividing groove between the first transition hole and the second center hole.

[0015] By setting the height of the dividing groove between the first transition hole and the second transition hole to be lower than the height of the dividing groove between the first transition hole and the second center hole, a stepped dividing structure is formed, which makes the two control ropes spatially staggered, effectively avoiding friction and mutual interference between the rope tendons and ensuring the independence of finger bending and opening movements.

[0016] In a preferred embodiment, to facilitate the flexible fingers to bend inward and stably grasp the fruit when the outer cord is taut, each flexible finger has several grooves along its longitudinal direction, with the openings of the grooves facing outwards from the flexible fingers.

[0017] By creating outward-facing grooves along the outer side of the fingers to form a rectangular tooth structure, the stiffness and resistance of the fingers when bending are reduced, allowing the fingers to produce directional and uniform bending deformation under the traction of the control rope, thus improving the smoothness and stability of the grasping action.

[0018] In a preferred embodiment, in order to achieve multi-degree-of-freedom spatial posture adjustment of the soft robotic arm and improve the flexibility of the arm, the soft robotic arm includes at least three flexible body sections, adjacent flexible body sections are connected by flexible joints, the end of the flexible body section near the soft robotic arm is connected to the lower end face of the flange, and the end of the flexible body section near the movable base is connected to the movable base.

[0019] By employing a modular configuration consisting of at least three flexible sections connected in series with flexible joints, the robotic arm possesses continuous bending and extension capabilities, enabling it to flexibly approach target fruits in different positions and orientations, thus overcoming the shortcomings of rigid robotic arms, such as limited degrees of freedom and insufficient workspace.

[0020] In a preferred embodiment, to ensure the durability of the robotic arm during outdoor operations and to prevent the ropes from cutting and damaging the soft material, the flexible body includes a main spring and at least four auxiliary springs distributed along the circumference. The main spring is located at the central axis of the flexible joint. The two ends of the main spring and auxiliary springs of the flexible body in the middle of the soft robotic arm are respectively connected to the flexible joint. One end of each of the main spring and auxiliary springs of the flexible body closer to the soft robotic arm is connected to the flexible joint, and the other end is connected to the lower end face of the flange. One end of each of the main spring and auxiliary springs of the flexible body closer to the moving base is connected to the flexible joint, and the other end is connected to the moving base.

[0021] By employing a structure where the main spring provides axial support and restoring force, and the secondary spring serves as both a drive rope channel and a bending guide, the lateral compressive force generated by the second control rope during tensioning acts directly on the metal spring body rather than the silicone material. This fundamentally solves the problem of tearing failure caused by the rope cutting into the silicone matrix in traditional wire-driven flexible arms, significantly extending the service life of the arm joints.

[0022] In a preferred embodiment, in order to achieve a reliable connection between the spring and the silicone joint and facilitate modular assembly, the flexible joint is provided with a third central hole and a guide hole through it along the axial direction. The third central hole is coaxial with the first central hole, and the guide holes are distributed circumferentially. A second boss and a third boss are extended and installed on the outer sides of both ends of the third central hole and the guide hole. The third central hole communicates with the second boss, and the guide hole communicates with the third boss. The end of the main spring is sleeved on the second boss, and the end of the auxiliary spring is sleeved on the third boss. Each first control rope passes through the main spring of each flexible body, the third center hole of each flexible joint, the first center hole of the flange, the first boss of the connecting plate, the second center hole, the branch groove, the first transition hole, and the second transition hole from the first line drive device on the moving base, and then enters the corresponding first channel and second channel to connect with the inside of the tip of the soft finger. Each second control rope passes through the second line drive device on the moving base, through the sub-spring of each flexible body, through the guide hole of each flexible joint, and connects to the bottom of the connecting disc.

[0023] By setting flexible joints with a second and a third boss, the ends of the main spring and the auxiliary spring are respectively fitted into the bosses to form an interference fit. This ensures no relative slippage without the need for additional fasteners such as bolts or clamps, improving the reliability and coaxiality of the connection between dissimilar materials and facilitating modular manufacturing and subsequent maintenance.

[0024] In a preferred embodiment, in order to achieve continuous and adjustable precise control of the gripping range and bending angle of the robotic arm, the first line drive device and the second line drive device each include a winding wheel and a drive motor connected to the winding wheel, the first control rope is connected to the winding wheel of the first line drive device, and the second control rope is connected to the winding wheel of the second line drive device.

[0025] By employing a drive motor in conjunction with a winding wheel, the winding wheel tightens or releases the control rope when the motor rotates in both directions. Combined with the controller's coordinated control of the speed, angle, and direction of each motor, stepless adjustment of finger opening and closing, arm bending, and extension and retraction can be achieved, avoiding the problems of air leakage and the need to carry an air source in pneumatic systems.

[0026] Beneficial Effects: This invention employs a composite structure of a soft robotic hand and a soft robotic arm, combined with a wire-driven device for independent control of grasping, bending, and extension. It integrates vision sensors and fiber optic grating sensors for target recognition and force feedback, achieving smooth, non-destructive grasping of small berries and multi-degree-of-freedom spatial posture adjustment. The coaxial central hole and circumferentially distributed mounting holes in the connecting assembly spatially separate the two types of control ropes, ensuring smooth and reliable transmission. The soft finger has first and second longitudinal channels along its diameter, controlling bending and opening respectively. The outer rope actively promotes rapid finger recovery, improving grasping response speed and size adaptability. The lower end face of the connecting plate features a branching groove and a stepped height design, allowing the control rope to enter the finger via an independent path, effectively avoiding rope tendon interference and friction. Longitudinal grooves with outward openings on the outer side of the finger form a rectangular tooth structure, reducing bending stiffness and ensuring uniform directional deformation. The soft robotic arm uses at least three flexible sections connected by flexible joints, possessing continuous bending and extension capabilities, overcoming the limitations of rigid arms in terms of restricted degrees of freedom and insufficient workspace. The flexible body uses a main spring to provide axial support and restoring force, while the secondary spring also serves as a cable channel and bending guide. This allows the cable compression force to act directly on the spring body rather than the silicone, fundamentally solving the tearing failure problem caused by the cable cutting through the silicone and extending the life of the arm. The flexible joint uses a boss to ensure an interference fit at the spring end, eliminating the need for additional fasteners and facilitating modular manufacturing and maintenance. A drive motor, in conjunction with a winding wheel and a controller, enables stepless and precise adjustment of finger opening and closing, arm bending, and extension / retraction, avoiding the drawbacks of pneumatic systems such as air leakage and the need for a portable air source. This invention meets the dual requirements of end effector compliance and robotic arm flexibility for automated small-scale berry harvesting. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is an overall structural diagram of the present invention; Figure 2 For the explosion of the present invention Figure 1 ; Figure 3 For the explosion of the present invention Figure 2 ; Figure 4 This is a structural diagram of the connecting disk of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0031] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] like Figures 1-4As shown, a soft robot for picking fruit includes a soft manipulator 1, a soft manipulator arm 2, a controller, a first wire drive device, a second wire drive device, a mobile base 3, a vision sensor 4, and a fiber optic grating sensor mounted on the soft manipulator 1. One end of the soft robotic arm 2 is mounted on the mobile base 3, and the other end is connected to the soft robotic hand 1 through the connecting component 5. The first wire drive device and the second wire drive device are mounted on the mobile base 3. The first line drive device is connected to the soft robotic arm 1 via a plurality of first control ropes 6, and the second line drive device is connected to the soft robotic arm 2 via a plurality of second control ropes 7. The visual sensor 4 is mounted on the connection assembly 5 and is used to identify and locate the target fruit; The controller is connected to the first line drive device, the second line drive device, the vision sensor 4, and the fiber optic grating sensor, respectively.

[0033] By employing a composite structure of a soft robotic hand 1 and a soft robotic arm 2, and with the independent control of the gripping of the robotic hand and the bending and extension of the robotic arm by a first-line drive device and a second-line drive device respectively, and integrating a vision sensor 4 and a fiber optic grating sensor to achieve target recognition and gripping force feedback, this system achieves compliant and non-destructive gripping of small berries and multi-degree-of-freedom spatial posture adjustment. This solves the problems of existing rigid robotic hands that easily damage fruits and have limited degrees of freedom, as well as the problems of pneumatic flexible arms that are prone to air leakage, aging, and large size outdoors. The fiber optic grating sensor is configured as a fiber optic grating sensor network and installed on the surface of the soft robotic hand 1 that contacts the fruit.

[0034] In order to effectively separate and guide the control ropes and avoid different control ropes from getting tangled or rubbing against each other during transmission, the connecting assembly 5 includes a flange 51 and a connecting plate 52. The flange 51 is provided with a first central hole 511 and circumferentially distributed first mounting holes 512. The upper end face of the connecting plate 52 is connected to the bottom end of the soft robotic arm 1, and the lower end face of the connecting plate 52 is connected to the flange 51. The connecting plate 52 has a second center hole 521 coaxial with the first center hole 511. The lower end face of the flange 51 is connected to the end of the soft robotic arm 2. One end of the first control rope 6 is connected to the first wire drive device, and the other end passes through the interior of the soft robotic arm 2, the first central hole 511, the second central hole 521 and then connects to the soft robotic hand 1. One end of the second control rope 7 is connected to the second wire drive device, and the other end passes through the interior of the soft robotic arm 2, the first mounting hole 512 and then connects to the bottom end of the connecting plate 52.

[0035] By setting coaxial first center hole 511 and second center hole 521 as channels for the first control rope 6, and setting circumferentially distributed first mounting holes 512 as fixing and turning points for the second control rope 7, spatial separation and orderly routing of the two types of control ropes at the connection between the robot and the robotic arm are achieved, ensuring the smoothness and reliability of the transmission process. Since silicone material is susceptible to wire cuts, the flange 51 and connecting plate 52 are made of 3D-printed resin material.

[0036] In order to achieve adaptive grasping of fruits of different sizes and shorten the grasping response time, the soft robotic arm 1 includes at least four soft fingers 11. Each soft finger 11 has a first channel 111 and a second channel 112 arranged longitudinally inside. The first channel 111 and the second channel 112 are distributed from the inside to the outside along the diameter direction. Each first control rope 6 passes through the first central hole 511 and the second central hole 521 and enters the first channel 111 and the second channel 112 of each soft finger 11 until it connects with the inside of the tip of the soft finger 11.

[0037] By sequentially creating a first channel 111 and a second channel 112 along the diameter direction inside each soft finger 11, the bending and opening of the finger are controlled respectively. When the inner cord relaxes, the outer cord tightens, which not only actively prompts the finger to return to its initial state but also flexibly adjusts the grasping range, enabling rapid and stable grasping of fruits of different sizes. A resin mounting block is fixedly installed at the top of the soft finger 11. This mounting block has two threaded through holes coaxial with the first channel 111 and the second channel 112, respectively. The first control cord 6 in the first channel 111 and the second channel 112 is wound around two screws, which are installed into the corresponding through holes to fix the first control cord 6.

[0038] To enable independent guidance and separation of the two first control ropes 6 in the same soft finger 11, the lower end face of the connecting plate 52 is provided with a number of branching grooves 522 corresponding to the soft finger 11, and a first boss 523 coaxially connected to the second central hole 521 is installed. The first boss 523 is installed in the first central hole 511. The connecting plate 52 is provided with a first transition hole 524 and a second transition hole 525 corresponding to the first channel 111 and the second channel 112 of each soft finger 11, respectively. One end of each branching groove 522 is connected to the second central hole 521, and the other end is connected to the first transition hole 524 and the second transition hole 525 in sequence. Each first control rope 6 enters the second central hole 521 through the inside of the first boss 523, enters the corresponding branching groove 522 from the second central hole 521, and enters the corresponding first channel 111 and second channel 112 after being branched by the branching groove 522.

[0039] By setting a branch groove 522 and a first boss 523 on the lower end face of the connecting plate 52, the first control rope 6 enters different channels of the finger after passing through the first boss 523, the second center hole 521, the branch groove 522, and the transition hole in sequence. This ensures that each control rope has an independent routing path, avoids interference and friction between ropes, and improves the accuracy and stability of gripping control. A partition 5211 is set in the middle of the second center hole 521, and a vision sensor 4 is installed on the partition 5211.

[0040] To prevent the two control ropes in the same soft finger 11 from interfering or tangling in the dividing groove 522, the height of the dividing groove 522 between the first transition hole 524 and the second transition hole 525 is lower than the height of the dividing groove 522 between the first transition hole 524 and the second center hole 521.

[0041] By setting the height of the branch groove 522 between the first transition hole 524 and the second transition hole 525 to be lower than the height of the branch groove 522 between the first transition hole 524 and the second center hole 521, a stepped branch structure is formed, which makes the two control ropes spatially staggered, effectively avoiding friction and mutual interference between the rope tendons, and ensuring the independence of finger bending and opening movements.

[0042] In order to facilitate the soft fingers 11 to bend inward and grasp the fruit stably when the outer rope is taut, each soft finger 11 has several grooves 113 along the longitudinal direction, and the openings of the grooves 113 face outward of the soft fingers 11.

[0043] By creating an outward-facing groove 113 along the longitudinal direction on the outer side of the finger, a rectangular tooth structure is formed, which reduces the stiffness and resistance when the finger bends, allowing the finger to produce directional and uniform bending deformation under the traction of the control rope, thereby improving the smoothness and stability of the grasping action.

[0044] In order to achieve multi-degree-of-freedom spatial posture adjustment of the soft robotic arm 2 and improve the flexibility of the arm, the soft robotic arm 2 includes at least three flexible bodies 21. Adjacent flexible bodies 21 are connected by flexible joints 22. The end of the flexible body 21 near the soft robotic hand 1 is connected to the lower end face of the flange 51, and the end of the flexible body 21 near the movable base 3 is connected to the movable base 3.

[0045] By employing a modular configuration consisting of at least three flexible sections 21 connected in series via flexible joints 22, the robotic arm possesses continuous bending and extension capabilities, enabling it to flexibly approach target fruits in different positions and orientations, overcoming the limitations of rigid robotic arms such as restricted degrees of freedom and insufficient workspace. Both the flexible sections 21 and the flexible joints 22 are made of silicone.

[0046] To ensure the durability of the robotic arm during outdoor operations and to prevent the ropes from cutting and damaging the soft material, the flexible body 21 includes a main spring 211 and at least four auxiliary springs 212 distributed along the circumference. The main spring 211 is located at the central axis of the flexible joint 22. The two ends of the main spring 211 and auxiliary springs 212 of the flexible body 21 in the middle of the soft robotic arm 2 are respectively connected to the flexible joint 22. One end of the main spring 211 and auxiliary spring 212 of the flexible body 21 near the soft robotic hand 1 is connected to the flexible joint 22, and the other end is connected to the lower end face of the flange 51. One end of the main spring 211 and auxiliary spring 212 of the flexible body 21 near the movable base 3 is connected to the flexible joint 22, and the other end is connected to the movable base 3.

[0047] By employing a structure where the main spring 211 provides axial support and restoring force, and the secondary spring 212 serves as both a drive rope channel and a bending guide, the lateral compressive force generated by the second control rope 7 when tensioned acts directly on the metal spring body rather than the silicone material. This fundamentally solves the problem of tearing failure caused by the rope cutting into the silicone matrix in traditional wire-driven soft arms, and significantly extends the service life of the arm joint.

[0048] To achieve a reliable connection between the spring and the silicone joint and facilitate modular assembly, the flexible joint 22 is provided with a third central hole 2211 and a guide hole 2212 through it along the axial direction. The third central hole 2211 is coaxial with the first central hole 511. The guide holes 2212 are distributed circumferentially. A second boss 2213 and a third boss 2214 are extended and installed on the outer sides of both ends of the third central hole 2211 and the guide hole 2212. The third central hole 2211 communicates with the second boss 2213, and the guide hole 2212 communicates with the third boss 2214. The end of the main spring 211 is sleeved on the second boss 2213, and the end of the secondary spring 212 is sleeved on the third boss 2214. Each first control rope 6 passes through the main spring 211 of each flexible body 21, the third center hole 2211 of each flexible joint 22, the first center hole 511 of the flange 51, the first boss 523 of the connecting plate 52, the second center hole 521, the branch groove 522, the first transition hole 524, and the second transition hole 525 from the first line drive device on the movable base 3, and then enters the corresponding first channel 111 and second channel 112 respectively, and connects with the inside of the tip of the soft finger 11. Each second control rope 7 passes through the second line drive device on the movable base 3, through the interior of the sub-spring 212 of each flexible body 21, and the guide hole 2212 of each flexible joint 22, and then connects to the bottom of the connecting plate 52.

[0049] By setting a flexible joint 22 with a second boss 2213 and a third boss 2214, the ends of the main spring 211 and the auxiliary spring 212 are respectively fitted into the bosses to form an interference fit. This eliminates the need for bolts, clamps, or other additional fasteners, ensuring no relative slippage and improving the reliability and coaxiality of the connection between dissimilar materials. It also facilitates modular manufacturing and subsequent maintenance. The flange 51 also has a boss communicating with the first center hole 511 for mounting the main spring 211, and the bottom surface of the flange 51 also has a boss circumferentially arranged for mounting the auxiliary spring 212.

[0050] In order to achieve continuous and precise control over the gripping range and bending angle of the robotic arm, the first line drive device and the second line drive device each include a winding wheel and a drive motor connected to the winding wheel. The first control rope 6 is connected to the winding wheel of the first line drive device, and the second control rope 7 is connected to the winding wheel of the second line drive device.

[0051] By employing a drive motor in conjunction with a winding wheel, the winding wheel tightens or releases the control rope when the motor rotates in both directions. Combined with the controller's coordinated control of the speed, angle, and direction of each motor, stepless adjustment of finger opening and closing, arm bending, and extension and retraction can be achieved, avoiding the problems of air leakage and the need to carry an air source in pneumatic systems.

[0052] By coordinating the tension and relaxation of each control rope, the extension, retraction, and multi-directional bending of the soft robotic arm 2 can be achieved, enabling multi-degree-of-freedom posture adjustment in space and flexibly approaching the cherry tomato fruits at different positions and orientations on the plant. Specifically: When all the second control ropes 7 are relaxed, the main spring 211 and auxiliary spring 212 within the flexible body 21 naturally extend from their initial compressed state, pushing the arm to lengthen and rise; when all the second control ropes 7 are tightened simultaneously, each spring is uniformly compressed, and the arm shortens and lowers as a whole; when one side of the second control rope 7 is tightened while the opposite side is relaxed, the spring on the tightened side is compressed and shortened, while the spring on the opposite side is relatively extended, causing the flexible joint 22 to bend towards the tightened side. By adjusting the tension of each second control rope 7, the size and direction of the bending angle can be continuously changed.

[0053] The soft robotic arm 2 adopts a line-driven method, eliminating the need for any pneumatic components or air source. This avoids common problems in outdoor pneumatic systems, such as pipe leakage, seal aging, and inconvenient air source transport. The composite structure formed by the main spring 211 and the auxiliary spring 212 utilizes the elastic restoring force of the springs to achieve elongation and bending. Complex multi-degree-of-freedom deformations can be completed by differentially controlling the second control rope 7. The structure is simple, reliable, and flexible, making it particularly suitable for long-term outdoor agricultural harvesting operations. Furthermore, the middle section of the arm is designed as a spring skeleton, with a measurable correspondence between the spring's deformation, compression, and bending angle. This provides a practical reference value for the middle section length change for subsequent kinematic modeling based on the assumption of constant curvature in segments, facilitating closed-loop verification of the theoretical model and measured data, and improving motion control accuracy.

[0054] The drive execution unit is integrated into the mobile base and mainly consists of a drive motor and its corresponding winding reel assembly. Each second control rope 7, used to control the bending and extension of the soft robotic arm 2, has its end wound and fixed to an independent winding reel, driven by the drive motor to rotate. Four first control ropes 6, used to control the opening and bending of the soft robotic arm 2, each have their ends fixed to an independent winding reel, also driven by the drive motor to rotate. When the drive motor rotates forward, the winding reel tightens the first control rope 6, pulling the corresponding soft finger inward to bend / open or causing the soft robotic arm 2 to bend in a specified direction. When the drive motor rotates in reverse, the winding reel releases the first control rope 6, and the soft finger recovers elastically or the soft robotic arm 2 returns to its initial state due to the spring's restoring force. Through the coordinated operation of the speed, angle, and direction of each drive motor, the opening and closing amplitude of the hand, the bending angle of the arm, and the extension and retraction length can be continuously and precisely controlled.

[0055] The main control unit is mounted on the circuit board of the mobile base and includes a microcontroller, a motor drive module, a power management module, and a communication module. The microcontroller receives instructions from the human-machine interface unit, calculates and generates target speed and angle signals for each drive motor, and controls the drive motor's movement through the motor drive module. Simultaneously, the microcontroller can collect feedback signals from the drive motor encoder, limit switches, or torque sensors to achieve tension monitoring and closed-loop position control of the first control rope 6 and the second control rope 7, preventing damage due to excessive tension or malfunction due to excessive slack.

[0056] The human-machine interface unit includes a host computer and a remote control terminal. The host computer can be a laptop or tablet, integrating vision sensors, fiber optic grating sensors for data acquisition and control, and drive motor parameter control. It has a visual interface for displaying robot status, setting harvesting parameters, and planning the work path. The remote control terminal can be a wireless handle or remote controller, directly translating the operator's harvesting intentions into commands for hand opening and closing, arm extension and bending, and base movement, which are then sent to the main control unit for execution via a wireless communication module. By switching between host computer autonomous control and remote manual control modes, both automated batch harvesting and precise manual intervention for fruits at specific locations can be achieved. The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A soft robot for picking fruit, characterized in that: Includes a soft robotic hand (1), a soft robotic arm (2), a controller, a first-line drive unit, a second-line drive unit, a moving base (3), a vision sensor (4), and a fiber optic grating sensor mounted on the soft robotic hand (1). One end of the soft robotic arm (2) is mounted on the mobile base (3), and the other end is connected to the soft robotic hand (1) through the connecting component (5). The first line drive device and the second line drive device are mounted on the mobile base (3). The first line drive device is connected to the soft manipulator (1) via a plurality of first control ropes (6), and the second line drive device is connected to the soft manipulator (2) via a plurality of second control ropes (7). The visual sensor (4) is mounted on the connection assembly (5) for identifying and locating the target fruit; The controller is connected to the first line drive device, the second line drive device, the vision sensor (4), and the fiber optic grating sensor respectively.

2. The soft robot for picking fruit according to claim 1, characterized in that: The connecting assembly (5) includes a flange (51) and a connecting plate (52). The flange (51) has a first central hole (511) and a first mounting hole (512) distributed around its circumference. The upper end face of the connecting plate (52) is connected to the bottom end of the soft robot (1), the lower end face of the connecting plate (52) is connected to the flange (51), the connecting plate (52) is provided with a second center hole (521) coaxial with the first center hole (511), and the lower end face of the flange (51) is connected to the end of the soft robot (2). One end of the first control rope (6) is connected to the first wire drive device, and the other end passes through the inside of the soft robotic arm (2), the first central hole (511), the second central hole (521) and then connects to the soft robotic hand (1). One end of the second control rope (7) is connected to the second wire drive device, and the other end passes through the inside of the soft robotic arm (2), the first mounting hole (512) and then connects to the bottom end of the connecting plate (52).

3. The soft robot for picking fruit according to claim 2, characterized in that: The soft robotic hand (1) includes at least four soft fingers (11). Each soft finger (11) has a first channel (111) and a second channel (112) arranged longitudinally inside. The first channel (111) and the second channel (112) are distributed from the inside to the outside along the diameter direction. Each first control rope (6) passes through the first central hole (511) and the second central hole (521) and enters the first channel (111) and the second channel (112) of each soft finger (11) until it connects with the inside of the tip of the soft finger (11).

4. The soft robot for picking fruit according to claim 3, characterized in that: The lower end face of the connecting plate (52) is provided with a number of branch grooves (522) corresponding to the soft fingers (11), and a first boss (523) coaxially connected to the second central hole (521) is installed. The first boss (523) is installed in the first central hole (511). The connecting plate (52) is provided with a first transition hole (524) and a second transition hole (525) corresponding to the first channel (111) and the second channel (112) of each soft finger (11). One end of each branch groove (522) is connected to the second central hole (521), and the other end is connected to the first transition hole (524) and the second transition hole (525) in sequence. Each first control rope (6) enters the second central hole (521) through the inside of the first boss (523), enters the corresponding branch groove (522) from the second central hole (521), and enters the corresponding first channel (111) and second channel (112) after being split by the branch groove (522).

5. The soft robot for picking fruit according to claim 4, characterized in that: The height of the dividing groove (522) between the first transition hole (524) and the second transition hole (525) is lower than the height of the dividing groove (522) between the first transition hole (524) and the second center hole (521).

6. The soft robot for picking fruit according to claim 3, characterized in that: Each soft finger (11) has several grooves (113) along its longitudinal direction, and the openings of the grooves (113) face outward from the soft finger (11).

7. The soft robot for picking fruit according to claim 4, characterized in that: The soft robotic arm (2) includes at least three flexible bodies (21), adjacent flexible bodies (21) are connected by flexible joints (22), the end of the flexible body (21) near the soft robotic hand (1) is connected to the lower end face of the flange (51), and the end of the flexible body (21) near the movable base (3) is connected to the movable base (3).

8. The soft robot for picking fruit according to claim 7, characterized in that: The flexible body (21) includes a main spring (211) and at least four auxiliary springs (212) distributed along the circumference. The main spring (211) is located at the central axis of the flexible joint (22). The two ends of the main spring (211) and auxiliary springs (212) of the flexible body (21) in the middle of the soft robotic arm (2) are respectively connected to the flexible joint (22). The main spring (211) and auxiliary springs (212) of the flexible body (21) near the soft robotic hand (1) are each connected to the flexible joint (22) at one end and connected to the lower end face of the flange (51) at the other end. The main spring (211) and auxiliary springs (212) of the flexible body (21) near the moving base (3) are each connected to the flexible joint (22) at one end and connected to the moving base (3) at the other end.

9. The soft robot for picking fruit according to claim 8, characterized in that: The flexible joint (22) is provided with a third central hole (2211) and a guide hole (2212) through it along the axial direction. The third central hole (2211) is coaxial with the first central hole (511). The guide hole (2212) is distributed along the circumference. The outer sides of both ends of the third central hole (2211) and the guide hole (2212) are provided with a second boss (2213) and a third boss (2214). The third central hole (2211) is connected to the second boss (2213), and the guide hole (2212) is connected to the third boss (2214). The end of the main spring (211) is sleeved on the second boss (2213), and the end of the secondary spring (212) is sleeved on the third boss (2214). Each first control rope (6) passes through the main spring (211) of each flexible body (21), the third center hole (2211) of each flexible joint (22), the first center hole (511) of the flange (51), the first boss (523) of the connecting plate (52), the second center hole (521), the branch groove (522), the first transition hole (524), and the second transition hole (525) of each flexible body (21) from the first line drive device on the moving base (3), and then enters the corresponding first channel (111) and second channel (112) respectively, and connects with the inside of the tip of the soft finger (11); Each second control rope (7) passes through the second line drive device on the moving base (3), through the interior of the sub-spring (212) of each flexible body (21), through the guide hole (2212) of each flexible joint (22), and then connects to the bottom of the connecting plate (52).

10. The soft robot for picking fruit according to claim 1, characterized in that: The first line drive device and the second line drive device each include a winding wheel and a drive motor connected to the winding wheel. The first control rope (6) is connected to the winding wheel of the first line drive device, and the second control rope (7) is connected to the winding wheel of the second line drive device.

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