Under-actuated rigid-flexible coupling apple picking end effector

Abstract

The invention discloses an under-actuated rigid-flexible coupling apple picking end effector, and belongs to the technical field of agricultural automation. The under-actuated rigid-flexible coupling apple picking end effector comprises a clamping mechanism, the clamping mechanism comprises three fingers which are evenly distributed at 120 degrees, a finger fixing base and a flexible suction cup, and each finger comprises a bottom knuckle, a middle knuckle and a tail knuckle which are sequentially hinged; the surface of the bottom knuckle, the surface of the middle knuckle and the surface of the tail knuckle are covered with first flexible silica gel, second flexible silica gel and third flexible silica gel respectively. The pressure sensors and the infrared sensor are electrically connected with the controller, the infrared sensor is arranged in the center of the bottom of the flexible suction cup, the controller controls the transmission mechanism to start and stop through feedback signals of the pressure sensors, when the pressure sensors located on the tail knuckle reach a preset threshold value, the corresponding transmission mechanism stops, and self-adaptive envelope grabbing is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agricultural automation, in particular to an underactuated rigid-flexible coupling apple picking end effector. BACKGROUND

[0002] In the existing application of apple picking robot, fruit damage has been one of the key factors restricting the development of picking robot, and the end effector directly contacting with apples is particularly important.

[0003] The current apple picking end effector can be mainly divided into air suction type and finger clamping type. The air suction type end effector creates a negative pressure environment by suction cup and air pump to suck the fruit, and then completes the fruit stem separation through the way of blade cutting or direct pulling off. However, due to the involvement of pneumatic components, there is inherent instability, which may cause the fruit to fall off during picking or the suction ability to be not strong enough to realize the twisting of apples and other operations. The finger clamping type end effector simulates the way of human hand picking fruit to carry out picking operation. Similar to the structure of fingers, when the fruit is grabbed, the fruit and the fruit stem are separated by twisting or pulling off. However, when the finger clamps grab the fruit, the adaptability to different sizes of fruit is poor. SUMMARY

[0004] The purpose of the present application is to overcome the problems in the prior art, and provide an underactuated rigid-flexible coupling apple picking end effector.

[0005] The application provides an underactuated rigid-flexible coupling apple picking end effector, a clamping mechanism, which comprises three fingers uniformly distributed at 120 degrees, a fixed seat and a flexible suction cup, each finger comprises a bottom phalanx, a middle phalanx and a terminal phalanx which are sequentially hinged, the fingers are installed on the periphery of the flexible suction cup through the fixed seat, the bottom of the flexible suction cup is connected with a mechanical arm, an infrared sensor is arranged at the center of the bottom of the flexible suction cup, and a pressure sensor is embedded on the surface of the bottom phalanx, the middle phalanx and the terminal phalanx respectively; a transmission mechanism is arranged in one-to-one correspondence with the fingers, and comprises a worm gear transmission assembly and a connecting rod mechanism, the worm gear transmission assembly comprises a motor, a worm gear and a worm, the worm gear is a special-shaped worm gear which is connected with the fixed seat through a rotating bearing, the motor is connected with the worm, the worm is engaged with the special-shaped worm gear, and the bottom phalanx is fixedly connected with the special-shaped worm gear; the connecting rod mechanism comprises a first connecting rod connecting the terminal phalanx with the middle phalanx, a triangular connecting rod connecting the middle phalanx with the bottom phalanx, a second connecting rod connecting the bottom phalanx with the special-shaped worm gear and a plurality of torsional springs; the torsional springs are arranged in three groups and are arranged at the hinge joints of the terminal phalanx and the middle phalanx, the hinge joints of the middle phalanx and the bottom phalanx and the connecting position of the bottom phalanx and the special-shaped worm gear respectively, and the transmission mechanism is used for controlling the bottom phalanx, the middle phalanx and the terminal phalanx to change angles in sequence; a control assembly is electrically connected with the pressure sensors, the infrared sensor and the worm gear transmission assembly, and is used for receiving detection signals of the pressure sensors and the infrared sensor; when the infrared sensor detects that the distance between the bottom of a fruit to be picked and the flexible suction cup is less than a threshold value, the control assembly controls the worm gear transmission assembly to start, so that each finger sequentially approaches the fruit from the bottom phalanx to the terminal phalanx, and when the pressure sensor on the terminal phalanx reaches a preset threshold value, the corresponding transmission mechanism stops, and adaptive enveloping grabbing is realized.

[0006] Preferably, the worm gear transmission assembly further comprises a motor and a worm; the bottom phalanx is fixedly connected with the special-shaped worm gear, the motor is connected with the worm, and the worm is engaged with the special-shaped worm gear.

[0007] Preferably, the surfaces of the bottom phalanx, the middle phalanx and the terminal phalanx are respectively covered with first flexible silica gel, second flexible silica gel and third flexible silica gel.

[0008] Preferably, the pressure sensors comprise first, second and third pressure sensors which are respectively embedded on the first, second and third flexible silica gel, and the motor stops when the third sensor reaches a preset threshold value.

[0009] Preferably, the flexible suction cup is made of silicone rubber material, and an annular corrugated structure is arranged at the edge of the flexible suction cup, so that elastic deformation can be generated in the axial direction.

[0010] Preferably, the safety protection system is further provided, which immediately cuts off the power supply of the motor when any of the following conditions is detected: any one of the first pressure sensor, the second pressure sensor and the third pressure sensor exceeds a safety threshold value; the motor current exceeds a rated value; the infrared sensor detects an abnormal distance change; the safety protection system further comprises a manual emergency stop switch and an overload protection device.

[0011] Preferably, the first fixed plate and the second fixed plate are horizontally arranged, a plurality of the fixed seats are fixedly installed on the first fixed plate, the motor is arranged between the first fixed plate and the second fixed plate and is limited by the fixing screws, a connecting column is fixedly connected to the bottom of the flexible suction cup and penetrates through the first fixed plate and the second fixed plate.

[0012] Preferably, the top of the worm is rotatably connected to the fixed seat through a bearing, the special-shaped worm wheel, the bottom knuckle and the fixed seat are all fixed through screws and nuts, forming a stable transmission structure.

[0013] Compared with the prior art, the beneficial effects of the present application are: the underactuated rigid-flexible coupling apple picking end effector of the present application adopts the combination design of three fingers uniformly distributed at 120° and a flexible suction cup, solving the poor adaptability of the prior art to apples of different sizes. The spatially symmetrical layout enables the effector to automatically adapt to apples with a diameter of 60mm-100mm, forming stable mechanical support through three-point contact, avoiding the problems of picking failure or fruit damage caused by size mismatch of traditional finger clamping type effectors. In the actual picking process, the three-finger uniform distribution structure can automatically adjust the envelope angle, ensuring the adaptability to apples of different sizes;

[0014] The combination of the flexible silicone layer covering the surface of each knuckle of the rigid-flexible coupling structure and the pressure sensor embedded in the surface of each flexible silicone layer is significantly better than the existing rigid effectors. The first flexible silicone, the second flexible silicone and the third flexible silicone cover the bottom knuckle, the middle knuckle and the end knuckle respectively, forming a multi-layer buffer protection and effectively reducing the contact stress. Experimental data shows that compared with the traditional rigid effector, the design can reduce the contact pressure on the surface of the apple by more than 60%, greatly reducing the fruit damage rate in the picking process;

[0015] The intelligent picking is realized by the cooperative control of the pressure sensors and the infrared sensor. The infrared sensor is arranged at the bottom center of the flexible suction cup, can accurately detect the distance of the target fruit, and automatically triggers the action of clamping the fruit when reaching the appropriate position; the pressure sensors are respectively embedded in the flexible silica gel surfaces, and the contact force is monitored in real time, when the bottom knuckle of the finger contacts the surface of the fruit, the bottom knuckle stops moving, and the middle knuckle continues to rotate under the driving of the motor; when the middle knuckle flexible silica gel contacts the fruit, the middle knuckle stops, and the last knuckle continues to rotate until the fruit is completely enveloped. This closed-loop control system ensures that the grasping force is accurately controllable, and the damage to the fruit caused by excessive pressure is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the present application.

[0017] Figure 2 It is a schematic diagram of the overall explosion structure of the present application.

[0018] Figure 3 It is a schematic diagram of the transmission structure of the present application.

[0019] Figure 4 It is a state diagram of the present application for grasping fruit.

[0020] The reference signs are explained as follows: 1, last knuckle; 2, middle knuckle; 3, first connecting rod; 4, triangular connecting rod; 5, bottom knuckle; 6, second connecting rod; 7, first fixed plate; 8, second fixed plate; 9, torsion spring; 10, screw; 11, third flexible silica gel; 12, second flexible silica gel; 13, first flexible silica gel; 14, first pressure sensor; 15, second pressure sensor; 16, third pressure sensor; 17, nut; 18, flexible suction cup; 19, infrared sensor; 20, fixed seat; 21, special-shaped worm gear; 22, rotating bearing; 23, worm; 24, fixing screw; 25, motor; 26, apple; 27, connecting column. DETAILED DESCRIPTION

[0021] The technical solutions of the embodiments of the present application will be described below in combination with the drawings of the embodiments of the present application. Figures 1-4 In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application, unless otherwise defined, the technical terms or scientific terms used herein should be the usual meanings understood by those skilled in the art in the field of the present application.

[0022] The terms "first," "second," and similar words used in the patent application specification and claims of this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "inner," "outer," "upper," "lower," "far," "near," "front," and "rear" are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. The drawings in this invention are not strictly drawn to scale; the specific dimensions and quantity of each structure can be determined according to actual needs. The drawings described in this invention are merely structural schematic diagrams.

[0023] This invention provides an underactuated rigid-flexible coupled apple-picking end effector, such as... Figures 1-4 As shown, the device includes a clamping mechanism comprising three fingers evenly distributed at 120° angles, a fixed base 20, and a flexible suction cup 18. Each finger includes a bottom phalanx 5, a middle phalanx 2, and a distal phalanx 1, which are hinged sequentially. The fingers are mounted on the periphery of the flexible suction cup 18 via the fixed base 20. The bottom of the flexible suction cup 18 is connected to the robotic arm, and an infrared sensor 19 is located at the center of the bottom of the flexible suction cup 18. Pressure sensors are embedded on the surfaces of the bottom phalanx 5, middle phalanx 2, and distal phalanx 1, respectively. A transmission mechanism is also included, with three sets corresponding to each finger. This includes a worm gear transmission assembly and a linkage mechanism. The worm gear transmission assembly includes a motor 25, a worm gear, and a worm 23. The worm gear is a non-circular worm gear 21 connected to the fixed base 20 via a rotary bearing 22. The motor 25 is connected to the worm 23, and the worm 23 meshes with the non-circular worm gear 21. The bottom phalanx 5 is fixedly connected to the non-circular worm gear 21. The linkage mechanism includes a first link 3 connecting the distal phalanx 1 and the middle phalanx 2, and a link connecting the middle phalanx 2 and the bottom phalanx 5. The system includes a triangular connecting rod 4, a second connecting rod 6 connecting the bottom finger joint 5 and the irregular worm gear 21, and several torsion springs 9. Three sets of torsion springs 9 are respectively located at the hinge points of the distal phalanx 1 and middle phalanx 2, the middle phalanx 2 and the distal phalanx 5, and the connection point of the distal phalanx 5 and the irregular worm gear 21. The transmission mechanism controls the sequential angle changes of the distal phalanx 5, middle phalanx 2, and distal phalanx 1. The control component, including pressure sensors, infrared sensors 19, and the worm gear transmission assembly, is electrically connected to the control component. The control component receives detection signals from the pressure sensors and infrared sensors 19. When the infrared sensor 19 detects that the distance between the bottom of the fruit to be picked and the flexible suction cup 18 is less than a threshold, the control component controls the worm gear transmission assembly to start, causing each finger to approach the fruit sequentially from the distal phalanx 5 to the distal phalanx 1. When the pressure sensor on the distal phalanx 1 reaches a preset threshold, the corresponding transmission mechanism stops, achieving adaptive envelope grasping.

[0024] In this embodiment, the actuator adopts a combination design of three fingers evenly distributed at 120° and a flexible suction cup 18, solving the poor adaptability of the prior art to apples 26 of different sizes. The spatially symmetric layout enables the actuator to automatically adapt to apples 26 with diameters ranging from 65 mm to 100 mm, forming stable mechanical support through three-point contact and avoiding the problems of picking failure or fruit damage caused by size mismatch in traditional finger clamp actuators. In the actual picking process, this three-finger evenly distributed structure can automatically adjust the envelope angle to ensure adaptability to apples 26 of different sizes;

[0025] The combination of the flexible silicone layer covering the surface of the rigid-flexible coupling structure and the embedded pressure sensors is significantly superior to existing rigid actuators. The first flexible silicone 13, the second flexible silicone 12, and the third flexible silicone 11 cover the bottom knuckle 5, the middle knuckle 2, and the end knuckle 1, respectively, forming a multi-layer buffer protection, effectively reducing contact stress, and greatly reducing the fruit damage rate during picking;

[0026] The cooperative control of the pressure sensors and the infrared sensor 19 realizes intelligent picking. The infrared sensor 19 is arranged at the bottom center of the flexible suction cup 18 and can accurately detect the distance of the target fruit, automatically triggering the picking action when reaching the appropriate position. The pressure sensors are embedded on the surfaces of the first flexible silicone 13, the second flexible silicone 12, and the third flexible silicone 11, respectively, to monitor the contact force in real time. In particular, when the pressure sensor on the end knuckle 1 reaches the preset threshold, the corresponding transmission mechanism is automatically stopped, realizing self-adaptive envelope grabbing. This closed-loop control system ensures that the grabbing force is accurately controllable, avoiding fruit damage caused by excessive pressure, where the threshold is usually set as the maximum safe pressure that does not damage the fruit.

[0027] Preferably, as shown in Figures 2-3 The bottom knuckle 5 is fixedly connected with the special-shaped worm gear 21, the motor 25 is connected with the worm 23, and the worm 23 is engaged with the special-shaped worm gear 21.

[0028] In this embodiment, the engagement transmission of the worm 23 and the special-shaped worm gear 21 has a high reduction ratio and transmission precision, enabling accurate control of the finger joints; the self-locking property of the worm and worm gear 23 mechanism prevents finger retraction caused by external forces during picking, ensuring grabbing stability; the motor 25 is arranged on the first fixed plate 7, with the output end directly connected to the worm 23, the entire transmission mechanism layout is compact, effectively reducing the volume and weight of the actuator, facilitating installation at the end of the mechanical arm; the configuration of the torsional spring 9 enhances the adaptive ability, the bottom knuckle 5, the middle knuckle 2, and the end knuckle 1 are connected through a linkage mechanism and provided with a torsional spring 9, enabling each knuckle to automatically adjust the angle according to the shape of the fruit, achieving better envelope effect.

[0029] Preferably, as shown inFigure 1 As shown, the connecting rod mechanism includes a first connecting rod 3 connecting the last phalange 1 and the middle phalange 2, a triangular connecting rod 4 connecting the middle phalange 2 and the bottom phalange 5, and a second connecting rod 6 connecting the bottom phalange 5 and the special-shaped worm gear 21; the torsion spring 9 is provided with three groups, which are respectively arranged at the hinged joints of the last phalange 1 and the middle phalange 2, the middle phalange 2 and the bottom phalange 5, and the bottom phalange 5 and the special-shaped worm gear 21.

[0030] In this embodiment, the first connecting rod 3 connects the last phalange 1 and the middle phalange 2, the triangular connecting rod 4 connects the middle phalange 2 and the bottom phalange 5, and the second connecting rod 6 connects the bottom phalange 5 and the special-shaped worm gear 21. This multi-connecting rod combination can convert the rotary motion of the motor 25 into the coordinated bending motion of each phalange, simulating the human hand grasping action; the torsion spring 9 optimizes the force transmission. The three groups of torsion springs 9 are respectively arranged at the connecting positions of the last phalange 1 and the middle phalange 2, the middle phalange 2 and the bottom phalange 5, and the bottom phalange 5 and the special-shaped worm gear 21, forming a multi-stage buffer system. This design not only ensures the uniform distribution of grasping force, but also automatically adjusts the angle of each phalange when encountering irregular fruit shapes, improving adaptability.

[0031] Preferably, as shown in the figure, Figures 1-2 As shown, the pressure sensors include a first pressure sensor 14, a second pressure sensor 15, and a third pressure sensor 16, which are respectively embedded in the first flexible silica gel 13, the second flexible silica gel 12, and the third flexible silica gel 11. When the third sensor reaches a preset threshold, the corresponding motor 25 stops.

[0032] In this embodiment, the first pressure sensor 14, the second pressure sensor 15, and the third pressure sensor 16 are respectively embedded in the first flexible silica gel 13, the second flexible silica gel 12, and the third flexible silica gel 11, forming a three-stage pressure monitoring system. This hierarchical monitoring can accurately grasp the contact state of each phalange and the fruit, avoiding excessive local pressure; the intelligent stop mechanism protects the fruit: when the third sensor reaches a preset threshold, the corresponding motor 25 stops, which ensures accurate control of the grasping force; independent control of the grasping force of each finger: the pressure sensors of each finger work independently, and when the pressure of the last phalange 1 of a certain finger reaches the threshold, only the motor 25 of that finger stops, without affecting the continued enveloping of other fingers. This design ensures the complete grasping of asymmetric fruits.

[0033] Preferably, as shown in the figure, Figure 1 As shown, the flexible suction cup 18 is made of silicone rubber material, and the edge is provided with an annular corrugated structure, which can produce elastic deformation along the axial direction.

[0034] In this embodiment, the material selection optimizes the adsorption performance: the flexible suction cup 18 is made of silicone rubber material, which has good elasticity and wear resistance, and can provide reliable adsorption force without damaging the surface of the fruit.

[0035] Preferably, as shown in Figure 1 The safety protection system also includes a manual emergency stop switch and an overload protection device.

[0036] In this embodiment, the first pressure sensor 14, the second pressure sensor 15, and the third pressure sensor 16, the motor current of the motor 25, and the distance change of the infrared sensor 19 are monitored in real time. If any parameter is abnormal, the power supply of the motor 25 is immediately cut off, forming a comprehensive protection. When the motor current exceeds the rated value, the power supply is automatically cut off, avoiding damage to the motor 25 due to overload, and significantly prolonging the service life of the actuator.

[0037] Preferably, as shown in Figures 1-3 The first fixed plate 7 and the second fixed plate 8 are horizontally arranged, and a plurality of fixed seats 20 are fixedly installed on the first fixed plate 7. The motor 25 is arranged between the first fixed plate 7 and the second fixed plate 8 and is limited by the fixed screws 24. The connecting column 27 penetrates the first fixed plate 7 and the second fixed plate 8 and is fixedly connected to the bottom of the flexible suction cup 18.

[0038] In this embodiment, the motor 25 is arranged between the first fixed plate 7 and the second fixed plate 8 and is limited by the fixed screws 24. This double-plate clamping structure effectively suppresses the vibration of the motor 25 during operation, improving the transmission stability. The connecting column 27 penetrates the first fixed plate 7 and the second fixed plate 8 and is fixedly connected to the bottom of the flexible suction cup 18, forming a stable space frame structure, so that the actuator is not easily deformed when bearing the picking reaction force, ensuring the reliability of long-term use.

[0039] Preferably, as shown in Figures 1-3 The top of the worm 23 is rotatably connected to the fixed seat 20 through a bearing, and the special-shaped worm wheel 21 and the bottom phalange 5 are both fixed to the fixed seat 20 through the screws 10 and the nuts 17, forming a stable transmission structure.

[0040] In this embodiment, the top of the worm 23 is rotatably connected to the fixed seat 20 through a bearing, greatly reducing the frictional resistance in the transmission process, improving the transmission efficiency, and reducing the wear of the parts and prolonging the service life. The special-shaped worm wheel 21 and the bottom phalange 5 are both fixed to the fixed seat 20 through the screws 10 and the nuts 17, forming a standardized modular structure, which is convenient for disassembly, maintenance, and part replacement, and reduces the use and maintenance cost.

[0041] The use method of the underactuated rigid-flexible coupling apple 26 picking end effector of the present application is as follows: When the end effector is moved to the vicinity of the target apple 26 by the robot arm, the infrared sensor 19 starts to detect the distance to the fruit. When the infrared sensor 19 detects that the distance between the end effector and the apple 26 reaches the preset working range, the picking action is ready to be performed.

[0042] The controller issues an instruction, and the three motors 25 are started simultaneously to drive the special-shaped worm gear 21 to rotate through the worm 23, thereby driving the three fingers to move towards the fruit. Since the torsional spring 9 is arranged between the joints, the bottom joint 5 starts to rotate first, and the middle joint 2 and the end joint 1 maintain the relative position due to the spring effect.

[0043] When the bottom joint flexible silica gel 13 of a finger contacts the surface of the fruit, the bottom joint 5 stops moving, and the middle joint 2 continues to rotate under the driving of the motor 25; when the middle joint flexible silica gel 12 contacts the fruit, the middle joint 2 stops, and the end joint 1 continues to rotate until it completely envelopes the fruit. In this process, the pressure sensors on the surfaces of the flexible silica gels monitor the contact pressure in real time.

[0044] When the end joint pressure sensor 14 of a finger reaches the preset threshold value, the controller stops the motor 25 corresponding to the finger. The three fingers are independently judged, and when all the end joint pressure sensors 14 reach the threshold value, the adaptive enveloping and grabbing are completed.

[0045] After the grabbing is completed, the robot arm performs the fruit separation action according to the program setting, and the apple 26 can be separated from the fruit branch through rotation, stretching or combined motion. The flexible suction cup 18 provides auxiliary fixation in the whole process to prevent the fruit from slipping off.

[0046] After the picking is completed, the motor 25 is reversed, and the joints are gradually restored to the initial position under the assistance of the torsional spring 9, thereby releasing the fruit into the collecting device and preparing for the next picking operation.

[0047] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. An underactuated rigid-flexible coupled apple-picking end effector, characterized in that, include The clamping mechanism includes three fingers evenly distributed at 120°, a fixed base (20), and a flexible suction cup (18). Each finger includes a bottom phalanx (5), a middle phalanx (2), and a distal phalanx (1) that are hinged in sequence. The fingers are mounted on the periphery of the flexible suction cup (18) through the fixed base (20). The bottom of the flexible suction cup (18) is connected to the robotic arm. An infrared sensor (19) is provided in the center of the bottom of the flexible suction cup (18). Pressure sensors are embedded on the surfaces of the bottom phalanx (5), the middle phalanx (2), and the distal phalanx (1), respectively. The transmission mechanism is provided in three sets corresponding to each finger, including a worm gear transmission assembly and a linkage mechanism. The worm gear transmission assembly includes a motor (25), a worm gear, and a worm (23). The worm gear is a non-circular worm gear (21) connected to the fixed seat (20) through a rotary bearing (22). The motor (25) is connected to the worm (23), and the worm (23) meshes with the non-circular worm gear (21). The bottom phalanx (5) is fixedly connected to the non-circular worm gear (21). The linkage mechanism includes a first link (3) connecting the distal phalanx (1) and the middle phalanx (2), and a connecting link (3). The triangular connecting rod (4) between the middle finger joint (2) and the bottom finger joint (5), the second connecting rod (6) connecting the bottom finger joint (5) and the worm gear (21), and several torsion springs (9); the torsion springs (9) are provided in three sets, respectively located at the hinge of the end finger joint (1) and the middle finger joint (2), the hinge of the middle finger joint (2) and the bottom finger joint (5), and the connection of the bottom finger joint (5) and the worm gear (21). The transmission mechanism is used to control the bottom finger joint (5), the middle finger joint (2) and the end finger joint (1) to change angles in sequence; The control component, including each pressure sensor, the infrared sensor (19), and the worm gear transmission assembly, is electrically connected to the control component. The control component is used to receive the detection signals from each pressure sensor and the infrared sensor (19). When the infrared sensor (19) detects that the distance between the bottom of the fruit to be picked and the flexible suction cup (18) is less than a threshold, the control component controls the worm gear transmission assembly to start, so that each finger approaches the fruit sequentially from the bottom phalanx (5) to the end phalanx (1). When the pressure sensor located on the end phalanx (1) reaches the preset threshold, the corresponding transmission mechanism stops, thereby realizing adaptive envelope grasping.

2. The underactuated rigid-flexible coupled apple picking end effector as described in claim 1, characterized in that, The surfaces of the bottom phalanx (5), the middle phalanx (2) and the distal phalanx (1) are respectively covered with a first flexible silicone (13), a second flexible silicone (12) and a third flexible silicone (11).

3. The underactuated rigid-flexible coupled apple picking end effector as described in claim 2, characterized in that, Each of the pressure sensors includes a first pressure sensor (14), a second pressure sensor (15), and a third pressure sensor (16), which are respectively embedded on the first flexible silicone (13), the second flexible silicone (12), and the third flexible silicone (11). When the third sensor reaches a preset threshold, the motor (25) stops.

4. The underactuated rigid-flexible coupled apple picking end effector as described in claim 1, characterized in that, The flexible suction cup (18) is made of silicone rubber material and has an annular corrugated structure on its edge, which can generate elastic deformation along the axial direction.

5. The underactuated rigid-flexible coupled apple picking end effector as described in claim 1, characterized in that, It also includes a safety protection system that immediately cuts off the power to the motor (25) when any of the following conditions are detected: If any one of the values ​​of the first pressure sensor (14), the second pressure sensor (15), and the third pressure sensor (16) exceeds the safety threshold; The motor (25) is operating at a current exceeding its rated value; The infrared sensor (19) detected an abnormal distance change; The safety protection system also includes a manual emergency stop switch and an overload protection device.

6. The underactuated rigid-flexible coupled apple picking end effector as described in claim 2, characterized in that, It also includes a first fixing plate (7) and a second fixing plate (8) set horizontally, a plurality of fixing seats (20) are fixedly installed on the first fixing plate (7), the motor (25) is set between the first fixing plate (7) and the second fixing plate (8) and is limited by fixing screws (24), and also includes a connecting column (27), the connecting column (27) passes through the first fixing plate (7) and the second fixing plate (8) and is fixedly connected to the bottom of the flexible suction cup (18).

7. The underactuated rigid-flexible coupled apple picking end effector as described in claim 2, characterized in that, The top of the worm (23) is rotatably connected to the fixed seat (20) via a bearing. The irregular worm wheel (21), the bottom finger joint (5), and the fixed seat (20) are all fixed by screws (10) and nuts (17) to form a stable transmission structure.

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