Flexible variable-position three-finger picking actuator and grabbing method thereof

Abstract

The invention provides a flexible variable-position three-finger picking actuator. The flexible variable-position three-finger picking actuator comprises a grabbing driving assembly, a passive finger assembly, a variable-position driving assembly and a fixed rack assembly. The grabbing driving assembly, the driven finger assembly and the displacement driving assembly are all arranged on the fixed rack assembly. The passive finger assembly comprises a finger bottom structure and a finger mechanism which are connected with each other, the finger bottom structure is movably connected to the fixed rack assembly, and the grabbing driving assembly is connected with the finger mechanism and can drive the finger mechanism to move, so that the passive finger assembly achieves the grabbing function; the displacement driving assembly is used for driving the finger bottom structure to rotate around the fixed rack assembly and driving the finger mechanism to change the position relative to the fixed rack assembly, and the grabbing posture of the passive finger assembly is changed. The finger displacement design ensures the flexibility of the picking actuator under the condition of less degree of freedom, the adaptive flexible assembly realizes the adaptability to fruits in different growth states, and the requirement on the pose of the actuator and the cost of the actuator in the picking process are reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of agricultural picking equipment, and in particular relates to a flexible variable-position three-finger picking executor and a picking method thereof, in particular to a flexible variable-position three-finger picking executor with tactile perception. BACKGROUND

[0002] Fruit and vegetable cultivation is increasingly moving towards intensive production, and the demand for automated harvesting equipment is becoming increasingly urgent. It is necessary to replace manual labor with automated equipment to improve efficiency and control costs. For example, tomatoes have a fragile texture, and traditional harvesting relies on manual picking, which is not only inefficient and costly, but also requires heavy physical labor for pickers. Therefore, it is particularly necessary to develop automated tomato picking technology to replace manual operations.

[0003] In the field of fruit and vegetable automated picking, especially for large tomatoes and other fruits that are easily damaged, the performance of the end effector is crucial. Existing picking executors are mainly divided into rigid clamping type and air bag type: rigid clamps have precise positioning and strong load capacity, but they are easily damaged due to improper force or posture; flexible executors reduce the risk of damage through material deformation, but they generally have poor wrapping and clamping stability for larger fruits, and lack fine tactile perception. What is particularly prominent is that the finger configuration of existing executors is usually fixed, which results in poor adaptability and makes it difficult to efficiently adapt to fruits of different sizes, shapes, and growth postures on the same plant.

[0004] Patent document CN113370248A discloses a fruit and vegetable picking robot flexible end effector with force perception, which includes a flexible finger module with force perception, a screw transmission mechanism, a visual depth camera, a pressure sensor, an executor shell, a flange, and connecting parts between components. The present application uses end joint driving as the power source of the executor, eliminating the need for an additional power source and reducing overall complexity. The executor uses screw transmission combined with link transmission to open and close the flexible fingers of the robot end joint driving executor. The flexible finger module of the executor has a pressure sensor that provides contact pressure feedback to the picking robot when grabbing fruits and vegetables. By adjusting the grabbing force of the fruits and vegetables through feedback, the executor can avoid damaging the skin of the fruits and vegetables during the picking process due to excessive grabbing force. The flexible finger module and hollow structure ensure the rigidity of the fingers when grabbing fruits and vegetables, and can produce appropriate deformation to wrap the fruits and vegetables when subjected to force, thereby achieving flexible and damage-free picking of fruits and vegetables.

[0005] However, the end effector of patent document CN113370248A cannot be circumferentially displaced, and cannot be adjusted to the most suitable finger configuration according to the posture and position of the fruit, making it difficult to pick fruits of different shapes and growth postures, and limiting its scope of application. SUMMARY

[0006] In view of the defects in the prior art, the present application aims to provide a flexible variable-position three-finger picking executor and a picking method thereof.

[0007] The flexible variable-position three-finger picking executor provided by the present application comprises a gripping driving assembly 3, a passive finger assembly 4, a variable-position driving assembly 6 and a fixed rack assembly. The gripping driving assembly 3, the passive finger assembly 4 and the variable-position driving assembly 6 are all arranged on the fixed rack assembly. The passive finger assembly 4 comprises a finger base structure and a finger mechanism connected with each other, the finger base structure is movably connected to the fixed rack assembly, the gripping driving assembly 3 is connected to the finger mechanism and can drive the finger mechanism to move, so that the passive finger assembly 4 realizes the gripping function. The variable-position driving assembly 6 is used to drive the finger base structure to rotate around the fixed rack assembly, thereby driving the finger mechanism to change the position relative to the fixed rack assembly, so as to change the gripping posture of the passive finger assembly 4.

[0008] Preferably, it further comprises a rotary-torque driving assembly 2. The fixed rack assembly comprises a palm 701, a rack 702, a base 703 and an arm connecting piece 704. The rotary-torque driving assembly 2 is fixedly connected to the base 703, and the rotating output end of the rotary-torque driving assembly 2 is fixedly connected to the arm connecting piece 704. The rack 702 is fixedly connected to the top of the arm connecting piece 704 and extends in a direction away from the arm connecting piece 704, and the palm 701 is fixed at the end of the extending direction of the rack 702. The rotary-torque driving assembly 2 can drive the arm connecting piece 704 to rotate and drive the rack 702 and the palm 701 to rotate.

[0009] Preferably, the gripping driving assembly 3 comprises a first steering engine 301, a crank slider mechanism 310 and a push-pull arm 302. The first steering engine 301 is fixedly connected to the rack 702. The crank slider mechanism 310 is arranged between the first steering engine 301 and the push-pull arm 302, and the crank slider mechanism 310 can convert the rotary motion of the output shaft of the first steering engine 301 into the linear motion of the push-pull arm 302. The push-pull arm 302 is used to synchronously push the finger base structure, thereby pushing the finger mechanism hinged to the finger base structure to move, so as to realize the gripping function.

[0010] Preferably, the finger base structure comprises a first movable finger base 401, a second movable finger base 402 and a third fixed finger base 403. The finger mechanism comprises a first finger mechanism 410, a second finger mechanism 420, and a third finger mechanism 430. The first movable finger base 401 and the second movable finger base 402 are slidingly connected to the palm 701 and can slide along the circumference of the palm 701. The third fixed finger base 403 is fixedly connected to the palm 701. The first finger mechanism 410 is hingedly connected to the first movable finger base 401, the second finger mechanism 420 is hingedly connected to the second movable finger base 402, and the third finger mechanism 430 is hingedly connected to the third fixed finger base 403.

[0011] Preferably, the adaptive flexible assembly 5 is further included. The adaptive flexible assembly 5 comprises a tactile sensor 501 and an elastic buffer mechanism 510. The tactile sensor 501 is fixedly arranged on the finger mechanism of the passive finger assembly 4 and is used to collect mechanical signals. The elastic buffer mechanism 510 comprises a nested ring 511. The first finger mechanism 410, the second finger mechanism 420, and the third finger mechanism 430 are respectively rotatably connected to the top of the push-pull arm 302 through the nested ring 511 in different elastic buffer mechanisms 510, and when the second finger mechanism 420 and the third finger mechanism 430 are adjusted in position, the corresponding nested ring 511 can rotate around the push-pull arm 302.

[0012] Preferably, the elastic buffer mechanism 510 further comprises a moving slider 512, an elastic element 513, and a stopper 514. The outer side of the nested ring 511 is fixedly provided with a sliding seat, the sliding seat is provided with a clamping groove, and the end of the clamping groove is provided with the stopper 514; the moving slider 512 is slidingly connected to the clamping groove and connected to the stopper 514 through the elastic element 513. The first finger mechanism 410, the second finger mechanism 420, and the third finger mechanism 430 are fixedly connected to the stopper 514 in the corresponding elastic buffer mechanism 510. When the first finger mechanism 410, the second finger mechanism 420, and the third finger mechanism 430 contact the fruit, the moving slider 512 can be displaced against the elastic force of the elastic element 513, thereby absorbing the impact force.

[0013] Preferably, the position adjustment driving assembly 6 comprises a first gear 601, a second steering wheel 602, a second gear 603, a third steering wheel 604, a first rack 605, and a second rack 606. The first gear 601 is installed on the output shaft of the second steering wheel 602, the first rack 605 is fixedly connected to the first movable finger base 401, the first gear 601 is engaged with the first rack 605, and the first rack 605 is arc-shaped. The second steering wheel 602 can drive the first gear 601 to rotate, and the first gear 601 drives the first rack 605 and the first mobile finger base 401 to slide along the circumference of the palm 701; The second gear 603 is installed on the output shaft of the third steering wheel 604, the second rack 606 is fixedly connected with the second mobile finger base 402, the second gear 603 is engaged with the second rack 606, and the second rack 606 is arc-shaped; The third steering wheel 604 can drive the second gear 603 to rotate, and the second gear 603 drives the second rack 606 and the second mobile finger base 402 to slide along the circumference of the palm 701.

[0014] Preferably, the image acquisition assembly 1 is further included; The image acquisition assembly 1 is fastened to the base 703 and can identify the position and growth posture of the object to be grabbed, thereby providing a basis for adjusting the gripping posture of the passive finger assembly 4 by the displacement driving assembly 6; The image acquisition assembly 1 is a depth camera.

[0015] According to the present application, a picking method for a flexible variable-position three-finger picking executor is provided, which comprises the following steps: The growth posture of the tomato fruit 8 is identified by the image acquisition assembly 1; It is judged whether the tomato fruit 8 is in a standard growth posture or a complex growth posture; When the tomato fruit 8 is in a standard growth posture, a non-displacement picking operation is adopted, and when it is in a complex growth posture, a displacement picking operation is adopted.

[0016] Preferably, the non-displacement picking operation comprises: S1: The image acquisition assembly 1 identifies the position and standard growth posture of the tomato fruit, generates a picking point coordinate, and the mechanical arm drives the executor to position to the target positive direction; S2: The first steering wheel 301 of the gripping driving assembly 3 drives the crank slider mechanism 310 to convert the rotary motion into the linear displacement of the push-pull arm 302, the push-pull arm 302 synchronously pushes the first mobile finger base 401, the second mobile finger base 402 and the third fixed finger base 403, and further drives the first finger mechanism 410, the second finger mechanism 420 and the third finger mechanism 430 hinged thereon to fold and rotate; S3: When the fingers contact the fruit, the elastic buffer mechanism 510 of the self-adaptive flexible assembly 5 is compressed and deformed to absorb the impact force and adapt to the size of the fruit, and at the same time, the tactile sensor 501 monitors the gripping pressure of each finger in real time and dynamically feeds back to the control system of the first steering wheel 301; S4: The rotary driving assembly 2 drives the arm connecting piece 704 to rotate, realizes the circumferential rotation of the executor, and completes the stable picking of the tomato fruit; The variable position grabbing operation comprises: S1: The image acquisition component 1 identifies the inclination angle and leaf shielding information of the tomato fruit, and generates an asymmetric grabbing path; S2: The variable position driving component 6 independently controls the two-finger configuration according to the asymmetric grabbing path: the second steering wheel 602 drives the first gear 601 to engage with the first rack 605, drives the first rack 605 and the first movable finger bottom 401 to slide along the circumference of the palm 701, the third steering wheel 604 drives the second gear 603 to engage with the second rack 606, drives the second rack 606 and the second movable finger bottom 402 to slide along the circumference of the palm 701, and the third fixed finger bottom 403 remains in place as a support reference, so that the three-finger spatial configuration is reorganized into a flanking posture; S3: The gripping driving component 3 pushes the push-pull arm 302 to displace linearly, and drives the reorganized passive finger component 4 to close; S4: The elastic buffer mechanism 510 of the adaptive flexible component 5 independently absorbs the impact force of each finger, the tactile sensor 501 monitors the pressure in a partitioned manner and feeds back the steering wheel output, so as to ensure that the gripping force is balanced in the inclined state, and the stable grabbing of the tomato fruit is completed.

[0017] Compared with the prior art, the present application has the following beneficial effects: 1. The three-finger spatial configuration is dynamically adjusted by the variable position driving component, so that the executor can adapt to fruits of different shapes and growth postures on the same plant, and the limitation of narrow application range of the traditional fixed configuration executor is broken through.

[0018] 2. The gripping force is monitored in real time by using tactile perception, and the gripping force is accurately adjusted through a feedback mechanism, so as to effectively avoid fruit damage and slipping phenomenon in the picking process.

[0019] 3. The flexible connecting piece can absorb the grabbing impact, can adapt to the size change of the fruit, and can significantly reduce the fruit damage rate.

[0020] 4. The present application has a clever design, the finger variable position design ensures the flexibility of the picking executor under fewer degrees of freedom, the adaptive flexible component realizes the adaptability to fruits in different growth states, and the picking process can reduce the requirements for the position and posture of the executor and reduce the cost of the picking executor. BRIEF DESCRIPTION OF DRAWINGS

[0021] Other features, objects and advantages of the present application will become more apparent through reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings: Figure 1 It is a structural schematic view of the flexible variable position three-finger picking executor; Figure 2 It is a structural schematic view of the flexible variable position three-finger picking executor from another perspective; Figure 3A top view of the flexible variable-position three-finger picking executor; Figure 4 A structural schematic diagram of the variable-position device; Figure 5 A local structural schematic diagram of the adaptive flexible component; Figure 6 A structural schematic diagram of the flexible variable-position three-finger picking executor in a pre-picking gesture; Figure 7 A structural schematic diagram of the flexible variable-position three-finger picking executor in a picking gesture; Figure 8 A structural schematic diagram of the flexible variable-position three-finger picking executor in a first gesture of a finger variable-position process; Figure 9 A structural schematic diagram of the flexible variable-position three-finger picking executor in a second gesture of a finger variable-position process; Figure 10 A flowchart of a non-variable-position grasping process of the flexible variable-position three-finger picking executor; Figure 11 A flowchart of a finger variable-position process of the flexible variable-position three-finger picking executor; The figure shows: DETAILED DESCRIPTION

[0022] The present application will be described in detail below with specific embodiments. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present application. These are within the scope of the present application.

[0023] Example 1: As Figures 1 to 9 shown, the flexible variable-position three-finger picking executor provided by the present application includes an image acquisition component 1, a twist driving component 2, a grasping driving component 3, a passive finger component 4, an adaptive flexible component 5, a variable-position driving component 6, and a fixed rack component. The above components are all arranged on the fixed rack component. The grasping driving component 3 is connected with the passive finger component 4 to realize the grasping function; the variable-position driving component 6 is used to drive the passive finger component 4 to realize the position change of the passive finger component 4 relative to the fixed rack component; the image acquisition component 1 is used to identify the growth posture of tomatoes; and the adaptive flexible component 5 is used to realize the self-adaptation to the fruit size and the tactile perception.

[0024] The image acquisition component 1 is a depth camera, which is fastened to the base 703 by bolts, can identify the position and posture of tomatoes, and provides a basis for the variable-position driving component 6 to adjust the finger position.

[0025] The rotary drive assembly 2 is an electric motor, which is fastened to the base 703 by bolts, and drives the frame 702 to rotate, so as to realize the circumferential rotation of the manipulator. The motor output shaft of the rotary drive assembly 2 is fixedly connected to the arm connecting piece 704, and the motor housing of the rotary drive assembly 2 is fixedly connected to the base 703.

[0026] The gripping drive assembly 3 comprises a first steering wheel 301, a crank slider mechanism 310 and a push-pull arm 302. The first steering wheel 301 is fastened to the frame 702 by bolts, and drives the crank slider mechanism 310 to convert the rotary motion into the linear motion of the push-pull arm 302, so as to complete the gripping function in cooperation with the passive finger assembly 4.

[0027] The passive finger assembly 4 comprises a finger base structure and a finger mechanism. The finger base structure is movably connected to the fixed frame assembly, and the finger mechanism is connected to the finger base structure. The finger base structure comprises a first movable finger base 401, a second movable finger base 402 and a third fixed finger base 403. The finger mechanism comprises a first finger mechanism 410, a second finger mechanism 420 and a third finger mechanism 430. The first movable finger base 401 and the second movable finger base 402 are placed on the palm 701 and can slide along the circumference of the palm 701. The third fixed finger base 403 is fastened to the palm 701 by bolts.

[0028] In addition, the gripping drive assembly 3 is connected to the finger mechanism and can drive the finger mechanism to rotate relative to the central axis of the passive finger assembly 4 to close and open, so that the passive finger assembly 4 can grip and release the grasped object, such as the tomato fruit 8.

[0029] The first finger mechanism 410 is hinged to the third fixed finger base 403, the second finger mechanism 420 is hinged to the first movable finger base 401, and the third finger mechanism 430 is hinged to the second movable finger base 402.

[0030] The adaptive flexible assembly 5 comprises a tactile sensor 501 and an elastic buffer mechanism 510. The elastic buffer mechanism 510 comprises a nested ring 511, a movable slider 512, an elastic element 513 and a stop block 514. The tactile sensor 501 is fastened to the passive finger assembly 4, can collect mechanical signals and adjust the gripping force of the fingers, so as to avoid damage or slipping of the fruit; the elastic buffer mechanism 510 is used to buffer the grasping impact and realize the self-adaptation to the size of the fruit.

[0031] The displacement drive assembly 6 comprises a first gear 601, a second steering wheel 602, a second gear 603, a third steering wheel 604, a first rack 605 and a second rack 606. The first gear 601 is directly driven by the second steering wheel 602, is engaged with the first rack 605, and drives the first rack 605 and the first movable finger base 401 to slide along the circumference of the palm 701. The second gear 603 is driven by the third servo motor 604 and meshes with the second rack 606, causing the second rack 606 and the second movable fingertip 402 to slide circumferentially along the palm 701. The first rack 605 is arc-shaped; the second rack 606 is arc-shaped.

[0032] The fixed frame assembly includes a hand 701, a frame 702, a base 703, and an arm connector 704; the hand 701 is fixed to the frame 702, and the base 703 is connected to the arm connector 704 via a rotary drive assembly 2. The frame 702 is fixedly connected to the top of the arm connector 704 and extends in a direction away from the arm connector 704, and the hand 701 is fixed to the end of the frame 702 in the extending direction.

[0033] like Figure 4 The diagram shows the structure of the displacement device: the nested ring 511 is nested on the push-pull arm 302 and can rotate circumferentially, thereby realizing the displacement adjustment of the second finger mechanism 420 and the third finger mechanism 430. Combined with... Figure 1 , Figure 2 The first finger mechanism 410, the second finger mechanism 420, and the third finger mechanism 430 are rotatably connected to the top of the push-pull arm 302 through the nested rings 511 in different elastic buffer mechanisms 510.

[0034] like Figure 5 The diagram shows a partial structural schematic of the adaptive flexible component 5: In the elastic buffer mechanism 510, a slide block can be fixedly installed on the outer side of the nested ring 511. The slide block has a slot, and a stop block 514 is provided at the end of the slot. The movable slider 512 is slidably installed in the slot and connected to the stop block 514 through an elastic element 513. The movable slider 512 is fixedly connected to the first finger mechanism 410, the second finger mechanism 420, and the third finger mechanism 430. When the finger mechanism contacts the fruit and is impacted, or when the fruit is large, the force will push the movable slider 512 to overcome the elastic force of the elastic element 513 and displace, thereby absorbing the impact force and allowing the finger mechanism to adaptively retreat, thus achieving the wrapping of fruits of different sizes.

[0035] Example 2: This embodiment can be understood as a more specific description of Embodiment 1.

[0036] The flexible, variable-position, three-finger picking actuator provided by this invention has the following picking process: like Figure 6 and Figure 7 The diagram shows the posture of the actuator during the picking process, where the gripping drive component enables adaptive gripping of the tomato.

[0037] This invention also proposes a grasping method for this flexible, variable-position three-finger grasping actuator. The steps include: The growth posture of the tomato fruit 8 is recognized by the image acquisition assembly 1; It is judged whether the tomato fruit 8 is in a standard growth posture or a complex growth posture; When the tomato fruit 8 is in the standard growth posture, a non-variable-position grabbing operation is adopted; when in the complex growth posture, a variable-position grabbing operation is adopted.

[0038] Figure 10 The flow chart of the non-variable-position grabbing operation in the grabbing method of the flexible variable-position three-finger picking executor is shown: the image acquisition assembly 1 (a depth camera) recognizes the position and standard growth posture of the tomato fruit 8, generates a grabbing point coordinate, and the mechanical arm drives the executor to be positioned to the target positive direction; the first steering wheel 301 of the gripping driving assembly 3 drives the crank slider mechanism 310 to convert the rotary motion into the linear displacement of the push-pull arm 302; the push-pull arm 302 synchronously pushes the first mobile finger bottom 401, the second mobile finger bottom 402 and the third fixed finger bottom 403, and then drives the first finger mechanism 410, the second finger mechanism 420 and the third finger mechanism 430 hinged thereto to be closed and rotated; at the moment of contacting the fruit, the elastic buffer mechanism 510 of the self-adaptive flexible assembly 5 is compressed and deformed, absorbs the impact force and is self-adaptive to the size of the fruit; at the same time, the tactile sensor 501 monitors the gripping pressure of each finger in real time and dynamically feeds back to the control system of the first steering wheel 301: when the pressure is over the threshold, the current output is reduced to avoid damage, and when the pressure is insufficient, the clamping force is increased to prevent slipping; the rotary driving assembly 2 drives the arm connecting piece 704 to rotate, realizes the circumferential rotation of the executor, and finally completes the stable grabbing with zero damage.

[0039] Embodiment 3: This embodiment can be understood as a more specific description of embodiment 1.

[0040] The flexible variable-position three-finger picking executor provided by the application has the finger variable-position process as follows: as shown in Figure 8 and Figure 9 As shown in the posture schematic diagram of the finger variable-position process: the posture information of the tomato provided by the depth camera is fed back to the executor, and the circumferential position of the three fingers is adjusted through the variable-position driving assembly.

[0041] Figure 11The flow chart of the variable position grasping operation in the grasping method of the flexible variable position three-finger picking executor is shown: when the tomato fruits are in a complex growth posture, the executor starts the variable position grasping mode, the image acquisition component 1 identifies the inclination angle and branch and leaf shielding information of the tomato fruits 8, and generates an asymmetric grasping path; the variable position driving component 6 independently controls the two-finger configuration according to the path instructions: the second steering wheel 602 drives the first gear 601 to mesh with the first rack 605, drives the first rack 605 and the first movable finger bottom 401 to slide along the circumference of the palm 701; the third steering wheel 604 drives the second gear 603 to mesh with the second rack 606, drives the second rack 606 and the second movable finger bottom 402 to slide along the circumference of the palm 701; the third fixed finger bottom 403 remains in place as a support reference; the three-finger spatial configuration is thus dynamically reorganized into a encircling posture, which is the best picking posture adapted to the actual posture of the fruits, so that the fingers are grasped on the best picking position of the tomatoes; then, the grasping driving component 3 pushes the push-pull arm 302 to linearly displace, and drives the reorganized passive finger component 4 to close; the elastic buffer mechanism 510 of the self-adaptive flexible component 5 independently absorbs the impact force of each finger, the tactile sensor 501 monitors the pressure in different zones and feeds back to adjust the steering wheel output, ensuring that the grasping force is balanced in the inclined state, and finally realizing stable grasping of fruits in complex postures.

[0042] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0043] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other without conflict.

Claims

1. A flexible variable position three-finger picking effector, characterized in that, Comprise: A grip driving assembly (3), a passive finger assembly (4), a displacement driving assembly (6) and a fixed frame assembly; The grip driving assembly (3), the passive finger assembly (4) and the displacement driving assembly (6) are all arranged on the fixed frame assembly; The passive finger assembly (4) comprises a finger base structure and a finger mechanism, the finger base structure is movably connected to the fixed frame assembly, the finger mechanism is connected to the finger base structure, the grip driving assembly (3) is connected with the finger mechanism and can drive the finger mechanism to rotate to fold, so that the passive finger assembly (4) realizes the grip function; The displacement driving assembly (6) is used for driving the finger base structure to rotate around the fixed frame assembly, so as to drive the finger mechanism to change the position relative to the fixed frame assembly, so as to change the grip posture of the passive finger assembly (4).

2. The flexible variable stance three-finger plucking effector of claim 1, wherein, Further comprise: A rotary drive assembly (2); The fixed frame assembly comprises a palm (701), a frame (702), a base (703) and an arm connecting piece (704); The rotary drive assembly (2) is tightly connected to the base (703), and the rotary output end of the rotary drive assembly (2) is tightly connected to the arm connecting piece (704); The frame (702) is fixedly connected to the top of the arm connecting piece (704) and extends away from the arm connecting piece (704), and the palm (701) is fixed at the end of the extending direction of the frame (702); The rotary drive assembly (2) can drive the arm connecting piece (704) to rotate and drive the frame (702) and the palm (701) to rotate.

3. The flexible variable position three-finger plucking effector of claim 2, wherein, The grip driving assembly (3) comprises a first steering wheel (301), a crank slider mechanism (310) and a push-pull arm (302); The first steering wheel (301) is tightly connected to the frame (702); The crank slider mechanism (310) is arranged between the first steering wheel (301) and the push-pull arm (302), and the crank slider mechanism (310) can convert the rotary motion of the output shaft of the first steering wheel (301) into the linear motion of the push-pull arm (302); The push-pull arm (302) is used for synchronously pushing the finger base structure, so as to push the finger mechanism hinged to the finger base structure to move, thereby realizing the grip function.

4. The flexible variable stance three-finger plucking effector of claim 1, wherein, The finger base structure comprises a first movable finger base (401), a second movable finger base (402) and a third fixed finger base (403); The finger mechanism comprises a first finger mechanism (410), a second finger mechanism (420) and a third finger mechanism (430); The first movable finger base (401) and the second movable finger base (402) are both slidably connected to the palm (701) and can slide along the circumference of the palm (701); The third fixed finger base (403) is tightly connected to the palm (701); The first finger mechanism (410) is hinged to the third fixed finger base (403), the second finger mechanism (420) is hinged to the first movable finger base (401), and the third finger mechanism (430) is hinged to the second movable finger base (402).

5. The flexible variable stance three-finger plucking effector of claim 1, wherein, Further comprise: An adaptive flexible assembly (5); The adaptive flexible assembly (5) comprises a tactile sensor (501) and an elastic buffer mechanism (510); The haptic sensor (501) is fixedly arranged on the finger mechanism of the passive finger assembly (4) and is used for collecting mechanical signals; The elastic buffering mechanism (510) comprises a nested ring (511); The first finger mechanism (410), the second finger mechanism (420) and the third finger mechanism (430) are rotatably connected to the top of the push-pull arm (302) through the nested rings (511) in different elastic buffering mechanisms (510), and when the second finger mechanism (420) and the third finger mechanism (430) are adjusted, the corresponding nested rings (511) can rotate around the push-pull arm (302) in the circumferential direction.

6. The flexible variable stance three-finger plucking effector of claim 1, wherein, The elastic buffering mechanism (510) further comprises a moving slider (512), an elastic element (513) and a stopper (514); The outer side of the nested ring (511) is fixedly provided with a sliding seat, the sliding seat is provided with a clamping groove, and the end of the clamping groove is provided with the stopper (514); the moving slider (512) is slidably connected to the clamping groove and connected to the stopper (514) through the elastic element (513); The first finger mechanism (410), the second finger mechanism (420) and the third finger mechanism (430) are fixedly connected with the stoppers (514) in the corresponding elastic buffering mechanisms (510); When the first finger mechanism (410), the second finger mechanism (420) and the third finger mechanism (430) contact the fruit, the moving slider (512) can be displaced against the elastic force of the elastic element (513), so as to absorb the impact force.

7. The flexible variable stance three-finger plucking effector of claim 1, wherein, The displacement driving assembly (6) comprises a first gear (601), a second steering wheel (602), a second gear (603), a third steering wheel (604), a first rack (605) and a second rack (606); The first gear (601) is installed on the output shaft of the second steering wheel (602), the first rack (605) is fixedly connected with the first movable finger bottom (401), the first gear (601) is engaged with the first rack (605), and the first rack (605) is arc-shaped; The second steering wheel (602) can drive the first gear (601) to rotate, the first gear (601) drives the first rack (605) and the first movable finger bottom (401) to slide along the circumference of the palm (701); The second gear (603) is installed on the output shaft of the third steering wheel (604), the second rack (606) is fixedly connected with the second movable finger bottom (402), the second gear (603) is engaged with the second rack (606), and the second rack (606) is arc-shaped; The third steering wheel (604) can drive the second gear (603) to rotate, the second gear (603) drives the second rack (606) and the second movable finger bottom (402) to slide along the circumference of the palm (701).

8. The flexible variable stance three-finger plucking effector of claim 1, wherein, Further comprising: An image acquisition assembly (1); The image acquisition assembly (1) is fixedly connected to the base (703) and can identify the position and growth posture of the object to be grabbed, thereby providing a basis for the displacement driving assembly (6) to adjust the gripping posture of the passive finger assembly (4); The image acquisition assembly (1) is a depth camera.

9. A grasping method for the flexible variable position three-finger plucking effector of any one of claims 1 to 8, characterized in that, The method comprises the following steps: The growth posture of the tomato fruit (8) is recognized by the image acquisition assembly (1); It is judged whether the tomato fruit (8) is in a standard growth posture or a complex growth posture; When the tomato fruit (8) is in a standard growth posture, a non-displacement grabbing operation is adopted; when it is in a complex growth posture, a displacement grabbing operation is adopted.

10. The method of claim 9, wherein, The non-displacement grabbing operation comprises: S1: The image acquisition assembly (1) recognizes the position and standard growth posture of the tomato fruit, generates a grabbing point coordinate, and the mechanical arm drives the executor to position to the target positive direction; S2: The first steering wheel (301) of the gripping driving assembly (3) drives the crank slider mechanism (310), converts the rotary motion into the linear displacement of the push-pull arm (302), synchronously pushes the first moving finger bottom (401), the second moving finger bottom (402) and the third fixed finger bottom (403), and then drives the first finger mechanism (410), the second finger mechanism (420) and the third finger mechanism (430) hinged thereon to fold and rotate; S3: When the fingers contact the fruit, the elastic buffer mechanism (510) of the adaptive flexible assembly (5) is compressed and deformed, absorbs the impact force and adapts to the size of the fruit, and at the same time, the tactile sensor (501) monitors the gripping pressure of each finger in real time and dynamically feeds back to the control system of the first steering wheel (301); S4: The rotary driving assembly (2) drives the arm connecting piece (704) to rotate, realizes the circumferential rotation of the executor, and completes the stable grabbing of the tomato fruit; The displacement grabbing operation comprises: S1: The image acquisition assembly (1) recognizes the inclination angle and branch leaf shielding information of the tomato fruit, and generates an asymmetric grabbing path; S2: The displacement driving assembly (6) independently controls the two finger configurations according to the asymmetric grabbing path: the second steering wheel (602) drives the first gear (601) to mesh with the first rack (605), drives the first rack (605) and the first moving finger bottom (401) to slide along the palm (701) in the circumferential direction; the third steering wheel (604) drives the second gear (603) to mesh with the second rack (606), drives the second rack (606) and the second moving finger bottom (402) to slide along the palm (701) in the circumferential direction, and the third fixed finger bottom (403) remains in place as a support reference, so that the three finger space configurations are reorganized into a flanking posture; S3: The gripping driving assembly (3) drives the push-pull arm (302) to linearly displace, and drives the reorganized passive finger assembly (4) to fold; S4: The elastic buffer mechanism (510) of the adaptive flexible assembly (5) independently absorbs the impact force of each finger, the tactile sensor (501) monitors the pressure in different zones and feeds back to adjust the steering wheel output, ensures the balance of the gripping force in the inclined state, and completes the stable grabbing of the tomato fruit.

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