Flexible four-jaw underactuated end-effector for harvesting dragon fruit

Abstract

The utility model discloses a kind of flexible pitaya picking four-jaw underactuated end effector, including four groups of gripper group and central screw nut mechanism, for the accurate self-adaptive gripping of fruit.The core is in by swing arm, middle connecting rod, side connecting rod and fixture connecting rod constitute parallelogram connecting rod mechanism, the mechanism ensures that four groups of gripper have very high synchronism and movement consistency in opening and clamping process, to form stable and uniform holding force field when gripping, effectively avoid fruit lateral tilting or local stress concentration, significantly reduce mechanical damage risk.Gripping stability is further enhanced by the profiling tooth structure in the inside of fixture, and finally realize efficient and lossless picking action.

Description

Technical Field

[0001] This utility model relates to the field of harvesting end effector technology, specifically a flexible four-claw underdriven end effector for harvesting dragon fruit. Background Technology

[0002] Dragon fruit, with its unique taste, rich nutritional value, and vibrant appearance, has seen its cultivation area and market demand grow year by year globally, especially in Asia. Currently, dragon fruit harvesting is still mainly done manually. While manual harvesting allows for precise handling of the fruit, it also presents challenges such as high labor intensity, low harvesting efficiency, high labor costs, and susceptibility to adverse weather conditions. Furthermore, the relatively fragile peel of dragon fruit is highly susceptible to mechanical damage during harvesting and transportation, resulting in damaged fruit appearance and reduced marketability and economic value.

[0003] With the development of agricultural automation and robotics, the research and development of efficient and low-damage automated dragon fruit harvesting equipment has become a research hotspot and an important development trend in the field of agricultural engineering. Automated harvesting robots typically consist of a vision recognition system, an end effector, a motion control system, and a mobile platform. Among these, the end effector is the key component that comes into direct contact with the fruit, and its design directly affects the harvesting efficiency, success rate, and degree of damage to the fruit. Utility Model Content

[0004] Therefore, in order to solve the above problems, the purpose of this utility model is to provide a flexible four-claw underactuated end effector for picking dragon fruit, including a base, on which a columnar claw disk is installed. Four gripper groups are connected at equal intervals on the side end face of the claw disk. A screw and nut mechanism is provided in the middle of the claw disk. The screw and nut mechanism includes a screw and a movable nut disk. The gripper group includes a clamp and a linkage group. The linkage group includes a control end, a follower end and a clamp end. The clamp end is rotatably connected to the clamp, the control end is rotatably connected to the movable nut disk, and the follower end is rotatably connected to the claw disk. A dragon fruit gripping area is formed between the four clamps. When the screw rotates to control the movable nut disk to move away from / close to the claw disk along the screw direction, the dragon fruit gripping area expands / shrinks.

[0005] Preferably, the linkage assembly includes a swing arm, a central link, a side link, and a clamping connecting rod. One end of the swing arm is a follower end rotatably connected to the claw plate. One end of the central link is a control end rotatably connected to the movable nut plate, and the other end is rotatably connected to the side link. The middle end of the central link is rotatably connected to the middle end of the swing arm. One end of the clamping connecting rod is rotatably connected to the side link, and the other end is a clamping end rotatably connected to the clamp. The middle end of the clamping connecting rod is rotatably connected to the end of the swing arm away from the claw plate.

[0006] Preferably, the linkage assembly includes an auxiliary linkage, one end of which is rotatably connected to the clamp and the other end of which is rotatably connected to the swing arm.

[0007] Preferably, the side of the clamp facing the dragon fruit holding area has serrated teeth.

[0008] Preferably, a contact switch is provided at one end of the swing arm rotatably connected to the clamp connecting rod. When the swing arm and the clamp connecting rod form a set angle, the contact switch is triggered by compression.

[0009] The beneficial effects of this utility model are:

[0010] The dragon fruit harvesting end effector of this invention achieves precise and adaptive fruit grasping through an innovative design of four sets of grippers and a central lead screw and nut mechanism. Its core lies in a parallelogram linkage mechanism composed of a swing arm, a central connecting rod, side connecting rods, and a clamp connecting rod. This mechanism ensures extremely high synchronicity and motion consistency of the four grippers during opening and clamping, thereby forming a stable and uniform holding force field during grasping. This effectively avoids fruit tilting or localized stress concentration, significantly reducing the risk of mechanical damage. The contoured tooth structure on the inner side of the clamps further enhances grasping stability, ultimately achieving efficient and damage-free harvesting. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of this utility model;

[0013] Figure 2 This is a schematic diagram of the planar structure of the present invention;

[0014] The following are the reference numerals: 1. Base; 2. Claw plate; 3. Gripper assembly; 31. Fixture; 32. Linkage assembly; 321. Swing arm; 322. Central link; 323. Side link; 324. Fixture connecting rod; 325. Auxiliary link; 4. Movable nut plate.

[0015] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0017] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application 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 application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0019] Example 1:

[0020] Figure 1 and Figure 2 This invention discloses a flexible four-claw underactuated end effector for harvesting dragon fruit, comprising a base 1, on which a columnar claw disk 2 is mounted. Four gripper assemblies 3 are evenly spaced on the side end face of the claw disk 2. A screw and nut mechanism is located in the middle of the claw disk 2, comprising a screw, a screw motor for driving the screw rotation, and a movable nut disk 4. Each gripper assembly 3 includes a clamp 31 and a connecting rod assembly 32. The connecting rod assembly 32 includes a swing arm 321, a central connecting rod 322, a side connecting rod 323, and a clamp connecting rod 324. One end of the swing arm 321 is a follower end rotatably connected to the claw disk 2. One end of 2 is the control end, which is rotatably connected to the movable nut plate 4, and the other end is rotatably connected to the side connecting rod 323. The middle end of the middle connecting rod 322 is rotatably connected to the middle end of the swing arm 321. One end of the clamp connecting rod 324 is rotatably connected to the side connecting rod 323, and the other end is the clamp 31 end, which is rotatably connected to the clamp 31. The middle end of the clamp connecting rod 324 is rotatably connected to the end of the swing arm 321 away from the claw plate 2. A dragon fruit clamping area is formed between the four clamps 31. When the screw rotates to control the movable nut plate 4 to move away from / close to the claw plate 2 along the screw direction, the connecting rod group 32 moves, and the dragon fruit clamping area expands / shrinks.

[0021] The linkage assembly 32 also includes an auxiliary linkage 325. One end of the auxiliary linkage 325 is rotatably connected to the clamp 31, and the other end is rotatably connected to the swing arm 321. The auxiliary linkage 325 is used to straighten the clamp 31 and prevent the clamp 31 from rotating freely, which would cause the clamping end face of the clamp 31 to not properly contact the dragon fruit, thus causing the dragon fruit to be crushed.

[0022] The clamp 31 has a contoured tooth on the side facing the dragon fruit holding area. The contoured tooth is made to fit the shape of the dragon fruit and takes into account the movement trajectory of the clamp 31 controlled by the linkage 32 in this embodiment. Specifically, the tooth length of the contoured clamp 31 gradually decreases from the outer edge to the inner edge, thereby forming a recess in the middle of the contoured clamp 31. This makes the dragon fruit evenly stressed and less prone to damage when multiple contoured clamps 31 hold the dragon fruit.

[0023] A contact switch is provided at one end of the swing arm 321 that is rotatably connected to the clamp connecting rod 324. When the swing arm 321 and the clamp connecting rod 324 form a specific angle, the contact switch is triggered by compression. Here, we will describe in detail the dragon fruit picking device related to the present invention. A complete dragon fruit picking device requires a mechanical arm for twisting. The end effector installed at the end of the mechanical arm is the present invention. It also needs to be configured with a related control system and a vision recognition system. The vision recognition system needs to include a depth camera. The contact switch in the present invention is electrically connected to the control system. When the contact switch is compressed, it feeds back information to the control system. After receiving the information, the control system confirms that the clamp 31 is in the open state. At this time, the mechanical arm needs to control the present invention to move to the dragon fruit to prepare to grab the dragon fruit.

[0024] Working principle:

[0025] Once the depth camera detects information about the dragon fruit, it will be transmitted to the robotic arm control system, which will then control the robotic arm to precisely move the end effector above the target dragon fruit or to the optimal picking position. The gripper 31 opens, and when the end effector is positioned above the dragon fruit and ready to pick it, the control system first sends a command to the lead screw motor hidden inside the claw disc 2, causing it to start rotating and driving the movable nut disc 4 to move outwards.

[0026] The outward movement of the lead screw nut drives the central connecting rod 322 to push the swing arm 321 and the side connecting rod 323 outward. During this opening process, the clamp connecting rod 324 retracts as the swing arm 321 swings. The clamp connecting rod 324 and the auxiliary connecting rod 325 together ensure that the clamp 31 keeps opening outward along the trajectory of the claw disk 2 axis.

[0027] When the clamp 31 is fully opened to the preset position, the clamp connecting rod 324 will touch the contact switch. After the contact switch is triggered, it immediately sends a position signal to the control system, and the lead screw motor stops rotating. The opening action of the end effector is completed, ready to receive the dragon fruit. The dragon fruit enters the closing action with the clamp 31. With the end effector fully open, the target dragon fruit is guided into the open clamp 31 by the precise movement of the robotic arm.

[0028] When the dragon fruit enters the open end effector, the control system commands the lead screw motor to rotate in the opposite direction, driving the lead screw to rotate and causing the movable nut disc 4 to retract inward, closing the clamp 31. The inward movement of the movable nut disc 4 pulls the central connecting rod 322 connected to it inward. The inward pull of the central connecting rod 322 causes the swing arm 321 and the side connecting rod 323 to close inward, thereby causing the contour clamp 31 to gradually encircle the dragon fruit.

[0029] Similarly, during the closing process, the auxiliary connecting rod 325 and the clamp connecting rod 324 work together continuously to ensure that the clamp 31 maintains a parallel movement trajectory to the claw plate 2 throughout the entire closing process, achieving stable, uniform, and non-biased clamping of the dragon fruit. When the movable nut plate 4 retracts to the preset limit stroke position, the lead screw motor immediately stops rotating. At this point, the dragon fruit is stably and without damage. After the gripping is completed, the robotic arm will execute the preset picking action, twisting to separate the dragon fruit from the plant.

[0030] The above description is only an optional embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the inventive concept of the present utility model using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A flexible four-claw underactuated end effector for picking dragon fruit, characterized in that, Includes a base (1), on which a columnar claw plate (2) is mounted. Four gripper groups (3) are connected at equal intervals on the side end face of the claw plate (2). A screw and nut mechanism is provided in the middle of the claw plate (2). The screw and nut mechanism includes a screw and a movable nut plate (4). The gripper group (3) includes a clamp (31) and a connecting rod group (32). The connecting rod group (32) includes a control end, a follower end and a clamp (31) end. The clamp (31) end is rotatably connected to the clamp (31), the control end is rotatably connected to the movable nut plate (4), and the follower end is rotatably connected to the claw plate (2). A dragon fruit gripping area is formed between the four clamps (31). When the screw rotates to control the movable nut plate (4) to move away from / close to the claw plate (2) along the screw direction, the dragon fruit gripping area expands / shrinks.

2. The flexible dragon fruit picking four-claw underactuated end effector according to claim 1, characterized in that, The linkage assembly (32) includes a swing arm (321), a middle link (322), a side link (323), and a clamp connecting rod (324). One end of the swing arm (321) is a follower end rotatably connected to the claw plate (2). One end of the middle link (322) is a control end rotatably connected to the movable nut plate (4), and the other end is rotatably connected to the side link (323). The middle end of the middle link (322) is rotatably connected to the middle end of the swing arm (321). One end of the clamp connecting rod (324) is rotatably connected to the side link (323), and the other end is the clamp (31) end rotatably connected to the clamp (31). The middle end of the clamp connecting rod (324) is rotatably connected to the end of the swing arm (321) away from the claw plate (2).

3. The flexible dragon fruit picking four-claw underactuated end effector according to claim 1, characterized in that, The linkage assembly (32) includes an auxiliary link (325), one end of which is rotatably connected to the clamp (31), and the other end is rotatably connected to the swing arm (321).

4. The flexible dragon fruit picking four-claw underactuated end effector according to claim 1, characterized in that, The clamp (31) has serrated teeth on the side facing the dragon fruit holding area.

5. The flexible dragon fruit picking four-claw underactuated end effector according to claim 1, characterized in that, A contact switch is provided at one end of the swing arm (321) which is rotatably connected to the clamp connecting rod (324). When the swing arm (321) and the clamp connecting rod (324) form a set angle, the contact switch is triggered by compression.

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