Fruit picking robot

Abstract

The present application belongs to the field of agricultural machinery, and relates to a fruit picking manipulator, which comprises a driving base, a differential transmission mechanism, a gripper and a shearing mechanism. A motor is arranged on the driving base, and the motor drives the differential transmission mechanism to control the gripper and the shearing mechanism to clamp and shear a target fruit. The gripper comprises a lead screw assembly, a movable tray and under-actuated fingers. The shearing mechanism comprises a cam link assembly and scissors. The motor drives the differential transmission mechanism to drive the lead screw assembly to open and close the under-actuated fingers and move the movable tray to form a closed gripping structure with the under-actuated fingers in the closed state, so as to clamp and limit the movement of the target fruit. Meanwhile, the motor also drives the differential transmission mechanism to drive the cam link assembly to open and close the scissors, so as to cut off the fruit stem after the target fruit is clamped stably, and the picking is completed. The manipulator can realize efficient and non-destructive picking of fruits.

Description

Technical Field

[0001] This invention belongs to the field of agricultural machinery and relates to a fruit-harvesting robot. Background Technology

[0002] Fruits change shape and firmness as they ripen, and they are inherently diverse and fragile. To handle these fragile and irregular agricultural products in agricultural applications, robotic arms need to be flexible and adaptable, which places higher demands on the adaptability of robot end effectors.

[0003] In current fruit and vegetable harvesting processes, the most common end effectors are flexible separation and rigid separation. Flexible separation mainly separates the fruit stem from the fruit through methods such as twisting, folding, and pulling, including vacuum suction, clamping, and suction-clamping types. This method has a simple structure but requires the fruit itself to have good impact resistance, and the end effector to have a large clamping force, and may cause surface damage. Rigid separation uses a device to cut the fruit stem, such as cold cutting and hot cutting. This method has a complex structure and may leave fruit stem residue, but it provides better protection for the fruit. Furthermore, the factors affecting the harvesting process are complex and variable. For example, weather can cause significant changes in temperature and humidity. In indoor environments, high crop planting density results in less space between crops, requiring the end effector to have a certain degree of stability.

[0004] Existing end effectors employ various adaptive gripping strategies to achieve non-destructive handling of fruits and vegetables, such as air suction cup grippers, contact grippers, and underactuated grippers. Air suction cup grippers require an external air source, resulting in higher costs. Contact grippers offer greater adaptability, but their structure becomes more complex depending on the shape of the object being gripped. Soft contact grippers can utilize flexible and soft tissue materials, achieving high adaptability through soft gripping and fuzzy controllability. Underactuated mechanisms offer advantages in gripping irregular products, reducing the number of hard contact points, and lowering the pressure required for gripping, but their trajectory control is unstable. Summary of the Invention

[0005] To address the aforementioned technical problems regarding harvesting stability and adaptability in existing technologies, this invention proposes a fruit-harvesting robot, the specific technical solution of which is as follows:

[0006] A fruit-harvesting robot includes: a drive base, a differential transmission mechanism, a gripper, and a shearing mechanism. The drive base is equipped with a motor, which drives the differential transmission mechanism to control the gripper and shearing mechanism to grip and shear the target fruit. Specifically, the gripper includes a lead screw assembly, a movable tray, and underactuated fingers. The shearing mechanism includes a cam linkage assembly and scissors. The motor drives the differential transmission mechanism to control the lead screw assembly to open and close the underactuated fingers, and moves the movable tray to cooperate with the closed underactuated fingers to form a closed gripping structure, thus gripping and restricting the movement of the target fruit. Simultaneously, the motor also drives the differential transmission mechanism to control the cam linkage assembly to open and close the scissors, cutting the fruit stem after the target fruit is stably gripped, completing the harvest.

[0007] Furthermore, the lead screw assembly includes: a lead screw with a slider, the two ends of which are rotatably connected to the corresponding underactuated fingers via connecting rods. The slider moves parallel in the vertical direction as the lead screw rotates, thereby driving the underactuated fingers connected to it to perform opening and closing movements; the movable tray is connected to the slider via a compression spring.

[0008] Furthermore, the underactuated finger includes: a palm plate, on which a proximal phalanx and a distal phalanx are sequentially mounted via a connecting plate. The distal phalanx is connected to the proximal phalanx via a rotating joint formed by a shaft hole, and a torsion spring is provided at the connection point to allow the distal phalanx to automatically reset after gripping.

[0009] Furthermore, the distal and proximal phalanges are made of a flexible material called soft rubber, and their cross-sections are curved.

[0010] Furthermore, the gripper also includes a feedback limiting mechanism, which is configured on the underactuated finger side. The feedback limiting mechanism includes a linkage assembly and a stepped limiting block. The limiting block is located on the inner edge of the palm plate. The linkage assembly connects the distal phalanx to the limiting block. As the underactuated finger continues to close, the distal phalanx flips outward and drives the linkage assembly to push the limiting block towards the center of the palm plate. When the limiting block contacts the slider, it physically limits the slider, causing the underactuated finger to stop closing.

[0011] Furthermore, the shearing mechanism also includes: a scissor frame, a cam-link assembly mounted on the scissor frame, the cam-link assembly including a drive cam and a link sliding module; the link sliding module including a long link, a guide rail, a slide block, and a short link, the slide block being movably mounted on the guide rail; one end of the long link is fixedly connected to the edge of the drive cam, and the other end is connected to the slide block; one end of the short link is connected to the slide block, and the other end is connected to the handle of the scissors, and the opening and closing of the scissors is controlled by the drive cam after rotation via the link sliding module.

[0012] Furthermore, the differential transmission mechanism includes: a differential, an input bevel gear, an output bevel gear, an intermediate bevel gear, a one-way clutch, and a resistance adjuster; the differential includes: a planetary gear carrier, a housing gear mounted outside the planetary gear carrier, and a planetary bevel gear and a half-shaft gear set mounted inside the planetary gear carrier and meshing with each other, the planetary bevel gear being fixedly connected to the inner side of the housing gear via a planetary gear shaft; one end of the input bevel gear is driven and connected by a motor, and the other end is meshed with the housing gear; the half-shaft gear set includes an upper half-shaft gear and a lower half-shaft gear, a camshaft is fixedly connected in the middle of the upper half-shaft gear, the upper end of the camshaft is connected to the hub of the drive cam via a one-way clutch, the intermediate bevel gear is set at the axle end of the lower half-shaft gear and rotates with the shaft and meshes with one end of the output bevel gear, the resistance adjuster is sleeved on the outside of the axle of the intermediate bevel gear to adjust the rotational resistance of the intermediate bevel gear, and the other end of the output bevel gear is connected to the lower end of the lead screw.

[0013] Furthermore, the one-way clutch includes a ratchet, a pawl, a first spring, and a bracket. The bracket is provided with a limiting part and a rotating pin. The bracket has a locking hole in the middle for engaging with the camshaft. After the pawl is fixedly connected to the rotating pin, it elastically abuts against the first spring and the limiting part, so that the head of the pawl is movably engaged with the inner ring of the ratchet.

[0014] Furthermore, the resistance adjuster includes: two semicircular rings, each with a friction plate on its inner side; one end of the two semicircular rings is connected by a pin, and the other end is connected by a bolt and a nut; a second spring is sleeved on the bolt between the nut and the other end of the semicircular ring; the axle of the intermediate bevel gear is located inside the friction plate; the preload of the second spring is changed by adjusting the nut to change the resistance of the friction plate on the intermediate bevel gear.

[0015] The beneficial effects of this invention include:

[0016] The finger movement is driven by a screw drive to maintain stable fruit grip. Flexible, underactuated grippers and auxiliary clamping mechanisms are designed to improve the gripper's adaptability to small fruits. The clamping mechanism is designed as a closed grip to enhance gripping stability. A rotary shearing scissor configuration is selected, and a linkage mechanism is designed to drive the scissors, enabling the end effector to separate the fruit branch from the fruit. A gear-type differential transmission mechanism is used, and a harvesting control strategy is implemented. A one-way clutch simplifies motion transmission switching control, and a resistance regulator adjusts the gripping force of the clamping mechanism on the fruit. In summary, this achieves efficient and damage-free fruit harvesting. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of a fruit-picking robot according to an embodiment of the present invention;

[0018] Figure 2 yes Figure 1 Top view;

[0019] Figure 3 yes Figure 1 Side view;

[0020] Figure 4 This is a schematic diagram of the structure of the clamp according to an embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of the closed gripping structure formed by the movable tray and the underactuated fingers in an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of the finger joints of an embodiment of the present invention being configured as arc-shaped in cross-section;

[0023] Figure 7 This is a schematic diagram of the main structure of the shearing mechanism according to an embodiment of the present invention;

[0024] Figure 8 This is a schematic diagram of the gear-type differential transmission mechanism according to an embodiment of the present invention;

[0025] Figure 9 This is a schematic diagram of the differential structure according to an embodiment of the present invention;

[0026] Figure 10 This is a flowchart illustrating the specific transmission control process of the differential transmission mechanism according to an embodiment of the present invention.

[0027] Figure 11 This is a schematic diagram of the feedback limiting mechanism according to an embodiment of the present invention;

[0028] Figure 12 This is a schematic diagram of the feedback limiting mechanism performing movement limiting according to an embodiment of the present invention;

[0029] Figure 13 This is a schematic diagram of the structure of a one-way clutch according to an embodiment of the present invention;

[0030] Figure 14 This is a schematic diagram of the resistance regulator according to an embodiment of the present invention;

[0031] Figure 15 This is a schematic diagram of the operation process of the robotic arm according to an embodiment of the present invention;

[0032] Figure 16 This is a schematic diagram of the operation flow of the main components of the robotic arm in an embodiment of the present invention;

[0033] In the diagram, 1 is the motor, 2 is the differential transmission mechanism, 3 is the clamp, and 4 is the shearing mechanism; 21 is the differential, 22 is the one-way clutch, and 23 is the resistance adjuster; 201 is the input bevel gear, 202 is the output bevel gear, and 203 is the intermediate bevel gear; 211 is the housing gear, 212 is the planetary bevel gear, 213 is the upper half-shaft gear, and 214 is the lower half-shaft gear; 221 is the ratchet, 222 is the pawl, 223 is the first spring, and 224 is the bracket; 231 is the semi-circular ring. 232 is a friction plate, 233 is a bolt, 234 is a nut, and 235 is a second spring; 301 is a movable tray, 302 is a lead screw, 303 is a slider, 304 is a connecting rod, 305 is a compression spring, 306 is a palm plate, 307 is a proximal knuckle, 308 is a distal knuckle, 309 is a limit block, and 310 is a connecting plate; 401 is a scissor, 402 is a scissor holder, 403 is a drive cam, 404 is a long connecting rod, 405 is a guide rail, 406 is a slide, and 407 is a short connecting rod. Detailed Implementation

[0034] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] like Figures 1-3 As shown, this embodiment discloses a fruit-harvesting robot, for example, capable of harvesting kumquats. The robot includes: a drive base, a differential transmission mechanism 2, a gripper 3, and a shearing mechanism 4. A motor 1 is mounted on the drive base, which drives the differential transmission mechanism 2 to move. The differential transmission mechanism 2, based on the law of least resistance, drives the gripper 3 and the shearing mechanism 4 to stably grip and protect the kumquat fruit and to cut the fruit stem, respectively.

[0036] The gripper 3 is a soft-contact type, combined with a flexible underactuated gripper with an underactuated structure. An underactuated structure refers to a mechanism that can still function normally by relying on its own dynamic constraints even when the number of actuators is less than the number of degrees of freedom of the mechanism itself. The mechanical characteristics of underactuation have excellent shape adaptability, and it can passively adapt to the shape of the object. Therefore, it can improve the adaptability to fruit, maintain a constant clamping force during the gripping process, and prevent the fruit from falling and being damaged due to changes in clamping force.

[0037] Specifically, such as Figure 4As shown, the gripper 3 includes: a lead screw assembly, a movable tray 301, and underactuated fingers. The lead screw assembly includes a lead screw 302 and a slider 303 slidably mounted on the lead screw 302. The two ends of the slider 303 are rotatably connected to the corresponding underactuated fingers via connecting rods 304. The slider 303 moves vertically parallel to the lead screw 302 as the lead screw 302 rotates, thereby driving the connected underactuated fingers to perform opening and closing movements. The movable tray 301 is located on the upper side of the lead screw 302 and is connected to the slider 303 via a compression spring 305. The movable tray 301 is inside the underactuated fingers and cooperates with the underactuated fingers to form a closed gripping structure to assist in gripping and restricting fruit movement. Figure 5 As shown, under the action of the compression spring 305, the position of the movable tray 301 can be adaptively adjusted according to the size of the fruit, thereby improving overall adaptability. The gripper 3 adopts a screw drive, which utilizes its advantages of high transmission accuracy and low likelihood of spontaneous movement, ensuring that the gripper of this invention maintains a constant clamping force. The closed gripping structure on the robotic arm can protect the fruit within the space while maintaining a certain degree of gripping stability.

[0038] The underactuated fingers include: a palm plate 306, on which a proximal phalanx 307 and a distal phalanx 308 are sequentially connected via a connecting plate 310. The distal phalanx 308 is connected to the proximal phalanx 307 via a rotating joint formed by a shaft hole. During grasping, as the fingers gradually close, the distal phalanx 308 adaptively rotates a certain angle to change the envelope space of the two fingers. A torsion spring is also provided so that the distal phalanx 308 can automatically return to its original position after grasping. The distal phalanx 308 and proximal phalanx 307 are made of flexible soft rubber material. Through displacement and deformation adjustment, they adapt to irregularly shaped fruits, improving the adaptability of the gripper 3, and also providing cushioning during grasping to increase the protection of the fruit. Additionally, as... Figure 6 As shown, the knuckles of the two fingers are set in an arc shape in cross-section to restrict the vertical direction of the gripping space, and the distal and proximal knuckles and the movable tray 301 form a restriction in the horizontal plane, forming a displacement restriction of three degrees of freedom to prevent the fruit from falling due to insufficient gripping force caused by external interference.

[0039] Compared to the gripping harvesting mechanism, the shearing mechanism 4 is more versatile, especially suitable for fruits with strong adhesion between the fruit and the stem. It also avoids excessive harvesting pressure between the end effector (the robotic arm) and the fruit, reducing fruit damage. There are three main shear configurations for shearing-type fruit branch separation: grinding, rotary shearing, and linear shearing. The grinding type is complex and lacks flexibility; the linear shearing type requires high installation precision; and the rotary shearing type is simple to install and requires less workspace. Therefore, the shearing mechanism 4 of this invention adopts a rotary shearing structure. Figure 7As shown, the shearing mechanism 4 includes: scissors 401, scissor holder 402, and a cam-link assembly mounted on the scissor holder 402. The cam-link assembly includes a drive cam 403 and a link sliding module. The link sliding module includes a long link 404, a guide rail 405, a slide block 406, and a short link 407. The slide block 406 is movably mounted on the guide rail 405. One end of the long link 404 is fixedly connected to the edge of the drive cam 403, and the other end is connected to the slide block 406. One end of the short link 407 is connected to the slide block 406, and the other end is connected to the handle of the scissors 401. The shearing mechanism 4, by utilizing the cooperation of the drive cam 403 and the link sliding assembly, can convert unidirectional circular motion into shearing motion. Furthermore, the blade movement range of this mechanism is relatively small, which can reduce damage caused by collisions to the scissors 401.

[0040] Differential transmission mechanisms 2 include various forms such as levers, pulleys, gears, Whiffletree differentials, and fluid differentials. Lever-type differential transmission mechanisms are simple in structure but require high torque and speed. Pulley-type differential mechanisms use multiple moving pulleys to convert a single input into multiple outputs; their disadvantage is the need to maintain cable tension, as a loose cable can cause it to slip off the pulleys. Gear-type mechanisms have high transmission efficiency and simple design, effectively transmitting force and torque, but they occupy a large space. Whiffletree differentials are similar to pulley-type mechanisms, both being cable-driven. Fluid differentials can use fluids such as air, water, or oil to transmit force from one input to multiple outputs through a T-tube; their disadvantage is the difficulty in repairing after fluid leakage.

[0041] In summary, this invention employs a gear-type differential transmission mechanism, such as... Figure 8 As shown, the mechanism includes: a housing, and a differential 21, an input bevel gear 201, an output bevel gear 202, an intermediate bevel gear 203, a one-way clutch 22, and a resistance adjuster 23, all installed within the housing. A slot is formed at the connection between the housing and the scissor block 402 to constrain the hinge point between the long connecting rod 404 and the short connecting rod 407 to slide linearly.

[0042] like Figure 9 As shown, the differential 21 includes: a planetary gear carrier (differential housing), a housing gear 211 mounted outside the planetary gear carrier, and a planetary bevel gear 212 and a half-shaft gear set mounted inside the planetary gear carrier and meshing with each other. The planetary bevel gear 212 is fixedly connected to the inner side of the housing gear 211 via a planetary gear shaft. The differential transmission mechanism 2 is a single-input, dual-output system. This invention designs two transmission routes during movement, such as... Figure 10As shown, motion is transmitted from the input bevel gear 201 to the housing gear 211, and then to the half-shaft gear set via the planetary bevel gear 212. The half-shaft gear set includes an upper half-shaft gear 213 and a lower half-shaft gear 214. A camshaft 408 is fixedly connected to the middle of the upper half-shaft gear 213, and the upper end of the camshaft 408 is connected to the hub of the drive cam 403. At this time, the differential 21 outputs motion differentially to two transmission routes: the first transmission route is that the upper half-shaft gear 213 rotates, driving the camshaft 408 to output through the one-way clutch 22 to the drive cam 403 of the shearing mechanism 4. Finally, the drive cam 403 drives the shears 401 to work through the connecting rod sliding module; the second transmission route is that the lower half-shaft gear 214 outputs to the intermediate bevel gear 203, and then through the resistance adjuster 23 and the output bevel gear 202, finally transmitting to the clamp 3. The intermediate bevel gear 203 and the output bevel gear 202 are meshed together. The resistance of the two transmission paths is compared in torque in the differential 21, and the motion is preferentially transmitted to the path with less resistance.

[0043] The gripper 3, as an underactuated mechanism, follows the law of least resistance in its movement. That is, when the number of driving elements is less than the number of degrees of freedom, movement is preferentially along the direction of least resistance. During stem shearing, the driving force is transmitted to the shearing mechanism. According to the law of least resistance, the resistance of the second transmission path should be greater than that of the first. If the shearing force is too large, the movement switches transmission paths under the action of the differential 3. To ensure the end effector operates according to the aforementioned picking sequence, the resistance of the second transmission path should be increased. This results in the fingers continuously closing, increasing the gripping force, and causing fruit damage. To address the problem of fruit damage caused by gripping, this invention includes a feedback limiting mechanism on the underactuated finger side, as described above. Figure 4 and Figure 11 The feedback limiting mechanism includes a linkage assembly and a limiting block 309. The limiting block 309 is located on the inner edge of the palm rest 306. The linkage assembly connects the distal phalanx 308 to the limiting block 309. During the continuous closing of the underdriven finger, the distal phalanx 308 flips outward under the clamping force, driving the linkage assembly to push the limiting block 309 towards the center of the palm rest 306. The radial movement distance of the limiting block 309 can be adjusted according to the rotation angle of the distal phalanx 308. The limiting block 309 is stepped, increasing the radial movement distance and increasing the height of the contact portion between the limiting block 309 and the lead screw slider 303. Figure 12As shown, the faster the limit block 309 contacts the lead screw slider 303, the faster it will contact the lead screw slider 303. When the limit block 309 contacts the lead screw slider 303, it forms a physical limit with the lead screw slider, making it difficult for the fingers to continue to close, thus preventing excessive gripping and excessive clamping force, and protecting the fruit. The linkage assembly mainly consists of a small connecting rod 311, a short straight push rod 312, a long straight push rod 313, a feedback long connecting rod 314, and a feedback short connecting rod 315 connected in sequence. Among them, the pin connecting the short straight push rod 312 and the long straight push rod 313 is connected to the limit block 309.

[0044] The harvesting robot of the present invention needs to go through three steps in the process of completing the work: grasping, cutting and placing. These three steps correspond to the three actions of gripper 3 and cutting mechanism 4: gripping, cutting and releasing. Therefore, differential transmission mechanism 2 needs to output three different movements, and must satisfy the sequence of gripping first, then cutting and finally releasing.

[0045] The differential transmission mechanism 2, with its dual output shafts (camshaft 408 and lead screw 302), connects both the shearing mechanism 4 and the gripper 3. Each output shaft has two rotational directions (clockwise and counterclockwise), corresponding to four different motions. To simplify the overall control of the end effector, a one-way clutch 22 is designed to isolate the motion in one direction of rotation of one output shaft, restricting rotation to only one direction. The gripper 3 is designed with a lead screw drive, using the forward and reverse rotation of the lead screw to achieve the opening and closing action of the fingers. Therefore, the one-way clutch 22 can be placed in the transmission path of the shearing mechanism 4, allowing the shearing action to be completed when the input shaft of the shearing mechanism 4 rotates forward, and restricted when rotating in the reverse direction, thus switching the motion to the gripper 3.

[0046] like Figure 13 As shown, the present invention designs a ratchet mechanism as a one-way clutch 22, mainly including a ratchet 221, a pawl 222, a first spring 223, and a bracket 224. When the ratchet 221 and pawl 222 are engaged, the resistance is relatively easy to overcome by friction and spring force, causing the ratchet 221 and pawl 222 to rotate together and automatically reset under the action of spring force. When rotating in the opposite direction, the geometry of the pawl 222 and the inner ring of the ratchet 221 do not match, resulting in greater resistance and preventing the ratchet mechanism from rotating in that direction.

[0047] To meet the varying gripping force requirements of the gripper 3 for harvesting different fruit varieties, the resistance adjustment mechanism 23 is used to adjust the gripping force. The total resistance of the gripper's transmission path should be the sum of the resistance set by the resistance adjuster 23, the gripping force, and the resistance of the gripper 3 itself. With the shear resistance and the gripper 3's own resistance remaining constant, adjusting the resistance of the gripper 3's path can change the gripping force of the gripper 3, thus controlling the magnitude of the gripping force. Figure 14As shown, the resistance adjuster 23 in this embodiment includes: a friction plate 232, a semi-circular ring 231, a second spring 235, a bolt 233, and a nut 234. During the picking process, the nut 234 can be adjusted to change the preload of the second spring 235, thereby changing the resistance of the mechanism to the intermediate bevel gear 203, and thus adjusting the clamping force of the fingers of the gripper 3.

[0048] The drive base is also equipped with a connecting flange, which is used to fix the motor 1 and connect it to external devices. This invention adopts a single-motor drive mode, which has fewer electronic components compared to multi-motor systems, resulting in a more compact structure, improved overall system reliability, and a simpler control algorithm, leading to more stable control.

[0049] like Figure 15 and Figure 16 As shown, during the harvesting process, the scissors 401 first clamp the fruit stem to fix the fruit in place, preventing the fruit from shifting due to collisions during the closing of the fingers, which would lead to failure in grasping. Then, the fruit is grasped by the closed structure of the fingers, and finally the scissors 401 cuts off the fruit stem to complete the separation of the fruit.

[0050] When the robotic arm is in operation, motor 1 drives the input bevel gear 201 to rotate, and the power is transmitted to the drive cam 403 and the output bevel gear 202 via the differential 21. The rotation of the drive cam 403 drives the connecting rod sliding module to close the shears 401. When the shears 401 touch the kumquat stem, the rotational resistance of the drive cam 403 increases. The differential 21 then transmits the power to the gripper 3. The lower end of the lead screw 302 in the gripper 3 is fixedly connected to the output bevel gear 202 and rotates with it, thereby moving the lead screw slider 303 to close the underdriven fingers and clamp the kumquat fruit. When the lead screw slider 303 is physically limited by the limit block 309, the movement resistance increases. Under the action of the differential 21, the power is transmitted to the drive cam 403, which drives the connecting rod sliding module to close the shears 401, thus cutting the stem and completing the harvest. This robotic arm utilizes the differential transmission mechanism 2 to drive the gripper 3 and the shearing mechanism 4 with a single motor, improving harvesting efficiency.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the implementation process of the present invention has been described in detail above, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fruit picking robot hand comprising: The application discloses a fruit picking device, which comprises a driving base, a differential transmission mechanism (2), a gripper (3) and a shearing mechanism (4), wherein the driving base is provided with a motor (1), the motor (1) drives the differential transmission mechanism (2) to control the gripper (3) and the shearing mechanism (4) to clamp and shear target fruits, characterized in that the gripper (3) comprises a lead screw assembly, a movable tray (301) and underdrive fingers, the shearing mechanism (4) comprises a cam link assembly and scissors (401), the motor (1) drives the differential transmission mechanism (2) to drive the lead screw assembly to open and close the underdrive fingers and move the movable tray (301) to form a closed gripping structure together with the underdrive fingers in the closed state, so as to clamp and limit the movement of the target fruits, and meanwhile, the motor (1) drives the differential transmission mechanism (2) to drive the cam link assembly to open and close the scissors (401), so as to cut off the fruit stem after the target fruits are clamped stably, and the picking is completed. The underdrive fingers comprise a palm disc (306), a proximal phalange (307) and a distal phalange (308) are sequentially installed on the palm disc (306) through a connecting plate (310), the distal phalange (308) is connected with the proximal phalange (307) through a rotation pair formed by shaft holes, and a torsional spring is arranged at the connection position, so that the distal phalange (308) is automatically reset after the gripping is completed. The gripper (3) further comprises a feedback limiting mechanism, the feedback limiting mechanism is arranged on the side of the underdrive fingers, and the feedback limiting mechanism comprises a link assembly and a stepped limiting block (309), the limiting block (309) is located at the inner side edge of the palm disc (306), the link assembly connects the distal phalange (308) with the limiting block (309), in the process of continuously closing the underdrive fingers, the distal phalange (308) is turned outward, and the link assembly is driven to push the limiting block (309) to move to the center of the palm disc (306), when the limiting block (309) contacts with a sliding block (303), the limiting block (303) is physically limited with the sliding block (303), so that the underdrive fingers stop continuously closing. The differential mechanism (2) comprises a differential (21), an input bevel gear (201), an output bevel gear (202), an intermediate bevel gear (203), a one-way clutch (22) and a resistance adjuster (23); the differential (21) comprises a planetary carrier, a housing gear (211) mounted outside the planetary carrier, and a planetary bevel gear (212) and a half shaft gear set mounted inside the planetary carrier and rotating with each other, the planetary bevel gear (212) being fixedly connected to the inside of the housing gear (211) through a planetary gear shaft; the input bevel gear (201) is drivenly connected to the motor (1) at one end and is meshingly connected to the housing gear (211) at the other end; the half shaft gear set comprises an upper half shaft gear (213) and a lower half shaft gear (214), the upper half shaft gear (213) being fixedly connected with a cam shaft (408) at the middle, the upper end of the cam shaft (408) being connected to the hub of a driving cam (403) through the one-way clutch (22), the intermediate bevel gear (203) being arranged at the wheel shaft end of the lower half shaft gear (214) to rotate with the shaft and to be meshingly connected to one end of the output bevel gear (202), the resistance adjuster (23) being sleeved outside the wheel shaft of the intermediate bevel gear (203) to adjust the rotational resistance of the intermediate bevel gear (203), and the other end of the output bevel gear (202) being connected to the lower end of a lead screw (302).

2. The fruit picking robot hand of claim 1, wherein The lead screw assembly comprises a lead screw (302), the lead screw (302) being provided with a sliding block (303), the sliding block (303) being rotatably connected to the corresponding side of an underactuated finger through connecting rods (304) at both ends, the sliding block (303) moving in parallel in the vertical direction with the rotation of the lead screw (302) to drive the underactuated finger connected thereto to move open and close, and the movable tray (301) being connected to the sliding block (303) through a compression spring (305).

3. The fruit picking robot hand of claim 1, wherein The distal phalange (308) and the proximal phalange (307) are made of soft rubber and have an arc shape in cross section.

4. The fruit picking robot hand of claim 1, wherein The shearing mechanism further comprises a shears frame (402), a cam link assembly being mounted on the shears frame (402), the cam link assembly comprising a driving cam (403) and a link sliding module; the link sliding module comprises a long connecting rod (404), a guide rail (405), a sliding seat (406), and a short connecting rod (407), the sliding seat (406) being movably mounted on the guide rail (405); the long connecting rod (404) is fixedly connected at one end to the edge of the driving cam (403) and is connected at the other end to the sliding seat (406); the short connecting rod (407) is connected at one end to the sliding seat (406) and is connected at the other end to the handle of a pair of scissors (401), and the driving cam (403) is driven to rotate to control the opening and closing of the pair of scissors (401) through the link sliding module.

5. The fruit picking robot hand of claim 1, wherein The one-way clutch (22) comprises a ratchet wheel (221), a pawl (222), a first spring (223) and a bracket (224), the bracket (224) is provided with a limiting portion and a rotating pin, a clamping hole embedded with the camshaft (408) is arranged in the middle of the bracket (224), the pawl (222) is fixedly connected with the rotating pin and elastically abuts against the limiting portion through the first spring (223) so that the head of the pawl (222) is movably engaged with the inner ring of the ratchet wheel (221).

6. The fruit picking robot hand of claim 1, wherein The resistance adjuster (23) comprises two half rings (231), one friction plate (232) is arranged on the inner side of each half ring (231), one end of each half ring (231) is connected through a pin, the other end is connected through a bolt (233) and a nut (234), a second spring (235) is arranged on the outer sleeve of the bolt (233) between the nut (234) and the other end of the half ring (231), the shaft of the intermediate bevel gear (203) is arranged on the inner side of the friction plate (232), the pre-tightening force of the second spring (235) is changed by adjusting the nut (234) so as to change the resistance of the friction plate (232) to the intermediate bevel gear (203).

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