Navel orange picking end effector based on one-fruit two-shearing agriculture and picking method

Abstract

The navel orange picking end effector comprises a base, the front portion of the bottom of the base is connected with a clamping assembly, the upper portion of the base is connected with a shearing box through a lifting mechanism, and a guide groove is formed in the front end of the shearing box; and upper and lower groups of blades positioned on the left and right sides in the guide groove are connected in the shearing box through pneumatic fingers. Integrated operation is achieved, the post-harvest treatment efficiency is improved, fruit stem separation and cutting are synchronously completed in one-time picking action, one fruit is cut twice, the procedure that secondary fruit stem treatment is needed after traditional picking is avoided, and the post-harvest treatment time and the labor cost are remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of agricultural harvesting robot technology, specifically relating to an end effector for harvesting navel oranges based on a two-pruning-per-fruit agronomy. This invention also relates to a harvesting method for navel oranges based on this two-pruning-per-fruit agronomy. Background Technology

[0002] Currently, navel orange harvesting in my country is mainly done manually, which suffers from low efficiency, high intensity, and safety hazards. With the development of artificial intelligence and control technology, intelligent harvesting robots are an inevitable trend in modern agriculture. The end effector, as its core actuator, determines the overall operational level of the machine.

[0003] Currently, there are three major problems with end effectors for navel orange harvesting, which seriously hinder the promotion of intelligent harvesting: First, insufficient agronomic adaptability. Existing citrus harvesting end effectors mostly use a single shearing mechanism, which cannot meet the agronomic requirements of "one fruit, two cuts." "One fruit, two cuts" requires the first cut to remove the navel orange with 2-3 leaves and stems, while simultaneously pruning the fruiting branches to prevent excessive spring shoot growth. The second cut should be made flush with the fruit stem to avoid scratching or piercing the fruit. However, existing equipment cannot simultaneously prune the fruiting branches to prevent excessive spring shoot growth, nor can it cut the fruit stem flush with the fruit stem to avoid scratching the fruit. Second, poor fruit size compatibility. It is difficult to adapt to different varieties and ripeness levels of navel oranges, easily leading to insecure clamping or damage to the peel. Third, the thin-film pressure sensor used for clamping force feedback has low mechanical strength and is difficult to maintain. Currently, most harvesting robot end effectors use thin-film pressure sensors for clamping force feedback. Although these sensors are highly accurate and have a fast response, the mechanical strength of the thin-film material is limited and maintenance is difficult, making them unsuitable for the harsh harvesting environment of orchards.

[0004] These problems directly prevent intelligent harvesting robots from replacing manual labor, exacerbating the contradiction of "labor shortage and high labor costs." Furthermore, fruit damage and inadequate implementation of agronomic practices reduce yield and quality, increasing economic losses for fruit farmers and orchard operating costs. In the high-end fresh fruit industry, such as navel oranges, traditional manual harvesting has long dominated. This relies on skilled workers to judge ripeness visually and tactilely, using fruit shears for precise manipulation to ensure minimal damage and high quality. However, this model is facing structural dilemmas and systemic risks. On the one hand, the aging and shortage of agricultural labor is irreversible, leading to a sharp increase in seasonal labor costs, becoming a core bottleneck restricting the industry's profitability. On the other hand, the physical limits of manual efficiency make it difficult for orchards to complete operations within the short optimal harvest period, easily causing overripe fruit, fruit drop, or forced early / late harvesting, directly damaging fruit quality and commercial value. In addition, high-altitude and sloping operations are intensive and dangerous, further exacerbating the labor shortage. These combined problems severely weaken the industry's sustainable competitiveness and pose a real threat to the stability of the supply chain and fruit farmers' income.

[0005] Therefore, developing a highly compatible and weather-resistant end-effector for navel orange harvesting that is suitable for "two-pronged harvesting of one fruit" will bring significant benefits in many aspects. Economically, it can substantially reduce long-term labor costs, improve harvesting efficiency, and reduce post-harvest losses. Industrially, it can promote production standardization, alleviate reliance on manual labor, and enhance the industry's ability to cope with market and natural risks. Socially, it can liberate the workforce from heavy, repetitive labor and facilitate their transition to technical positions. Moreover, this technology has broad prospects for widespread application, can be widely adapted to navel orange orchards of different sizes and varieties, accelerate the implementation of smart agriculture technology in citrus cultivation, and provide strong support for the development of modern agriculture. Summary of the Invention

[0006] The purpose of this invention is to provide a navel orange harvesting end effector based on the "one fruit, two cuts" agronomy, which solves the problem that existing single-cutting mechanisms cannot achieve "one fruit, two cuts".

[0007] Another objective of this invention is to provide a harvesting method for navel oranges based on a two-pronged harvesting technique, which can clamp the navel oranges tightly without damaging them.

[0008] The first technical solution adopted in this invention is: a navel orange harvesting end actuator based on the "one fruit, two cuts" agronomy, including a base, a clamping component connected to the bottom front of the base, and a cutting box with a guide groove at the front end connected to the top of the base through a lifting mechanism. Inside the cutting box, two sets of blades located on the left and right sides of the guide groove are connected by pneumatic fingers.

[0009] The first technical solution of the present invention is further characterized in that, The clamping assembly includes a vertical plate fixed to the front end of the base bottom. A clamping motor fixed to the bottom of the base with its output shaft facing forward is provided behind the vertical plate. A closed-loop stepper motor controller is fixed on the clamping motor. A finger support located in front of the base is hinged to each of the left and right ends of the vertical plate. A drive plate is hinged between the two finger supports through a connecting frame. A nut that runs through the front and back is fixed on the drive plate. A lead screw that runs through the rear end of the nut and is coaxially fixed to the clamping motor is connected to the internal thread of the nut. A clamping finger is hinged to the front end of each finger support.

[0010] A buffer opening is provided at one end of the finger clamping device near the finger support. The front end of the finger support passes through the buffer opening and is connected to the rear end of the finger clamping device by a tension spring. The position where the front end of the finger support passes through the buffer opening is rotatably connected to the finger clamping device by a pin.

[0011] A receiving frame located outside the lead screw is fixedly connected to the front of the drive board. An arc-shaped soft pad with an opening facing forward is fixedly connected to the front end of the receiving frame. Silicone pads are fixedly attached to the sides of the two fingers that are close to each other.

[0012] The lifting mechanism includes two nuts fixed at intervals on the base and extending vertically through each other. Each nut is threaded with a lead screw whose upper end extends into the rear end of the shear box. Both lead screws are coaxially fixed with driven gears at their upper ends. A driving gear meshes between the two driven gears. A stepper motor is coaxially fixed above the driving gear. Sliding bushings extending vertically through each other are fixed at the four corners of the shear box near the stepper motor. Each sliding bushing has a guide rod that extends downward and is fixed to the base.

[0013] The pneumatic finger includes a cylinder fixed inside the shear box. On the left and right sides in front of the cylinder, L-shaped actuating connectors are connected via longitudinal rotating shafts fixed to the shear box. The ends of the two actuating connectors that are close to each other are provided with vertically penetrating slots. A drive column is fixed on the output shaft of the cylinder, which extends longitudinally into the two slots and slides with them. A transverse slide rail fixed to the shear box is provided in front of the two actuating connectors. A through-hole is provided at the bottom of the slide rail corresponding to the position of the two actuating connectors along the length direction. Two T-shaped sliders with one end extending outwards slide in the slide rail. Each slider has an actuating groove at the end near the through-hole. The ends of the two actuating connectors that are far from each other extend into the two actuating grooves respectively.

[0014] Each slider has a tool holder frame fixed to one end of the slide rail, and a blade with its cutting edge facing the guide groove is fixed to both the upper and lower ends of the tool holder frame.

[0015] A target detector is fixed to the top of the shear box, and a rectangular fiber optic sensor is fixed to the bottom of the shear box near the guide groove.

[0016] The second technical solution adopted in this invention is: a harvesting method for navel oranges based on a two-pruning agronomy using a harvesting end effector, comprising the following steps: Step 1: The target detector detects the location of the navel orange on the tree, and the robotic arm drives the base to align the clamping component with the target navel orange for clamping. Step 2: After the positive pressure at the clamping point of the clamping component reaches the limit value, the lifting mechanism starts to drive the shear box to move closer to the base; Step 3: When the rectangular fiber optic sensor is blocked by a navel orange, the pneumatic finger starts to drive the upper and lower sets of blades to close simultaneously, cutting off the fruit branches and stems and cutting the stems flat at the fruit stalk, achieving two cuts on one fruit. After completion, the upper and lower sets of blades open. Step 4: The robotic arm moves the base to the fruit collection area, the clamping component opens and releases the fruit, and the shearing box returns to its original position away from the base.

[0017] The second technical solution of the present invention is further characterized in that, The control method for the positive pressure at the clamping point in step 2 is as follows: 1) Under the action of the clamping assembly, the navel orange remains balanced in the horizontal plane. The two clamping fingers clamp the navel orange on the left and right sides respectively, and each clamping finger forms two contact points, one at the front and one at the back. Based on this, the mechanical equation is established:

[0018] In the formula, F N1 , F N2 , F N3 , F N4 The normal force at the four contact points formed by the two gripping fingers is denoted as follows: F N1 The normal force at the contact point on the right front, F N2 The normal force at the right rear contact point, F N3 The normal force at the left front contact point, F N4 The normal force at the left rear contact point. θ 1 is F N1 The angle between the X-axis and the left-right direction; Next, establish a nonlinear relationship between the clamping force and the transverse diameter of the navel orange. When the transverse diameter of the navel orange is constant, assume that the spring is undeformed and that the hinge points of the clamping fingers and the finger support are collinear, and calculate the normal force at the contact point of the navel orange. F N1 :

[0019] In the formula, F a Let O1 be the axial thrust of the lead screw; and let O1 be the hinge point between the right end of the vertical plate and the finger support. L The vertical distance between the connecting frame and the hinge point O1 is [missing information]. L 1 、L 2 are respectively F N1 , F N2 The perpendicular distance from the hinge point O1; θ 3 is the angle between the connecting frame and the X-axis formed by the left and right directions; 2) The relationship between the clamping motor current I and the clamping motor torque T is:

[0020] In the formula, K t The torque constant; And the clamping motor torque value T and the lead screw axial thrust Fa The relation is:

[0021] In the formula, P For the lead screw, η For transmission efficiency; Then the clamping motor current I and the axial thrust of the lead screw are obtained. F a Relationship; 3) Combine the contact point normal pressure obtained in 1). F N1 The clamping motor current I and the lead screw axial thrust obtained from expression 2) F a Relational expressions, merging and replacing F a Obtain the normal pressure at the contact point F N1 The relationship between the clamping motor current I and the current I is:

[0022] Therefore, the normal pressure at the contact point F N1 The contact point pressure is positively correlated with the clamping motor current I, thus the contact point pressure can be controlled by controlling the clamping motor current I. F N1 .

[0023] The beneficial effects of this invention are as follows: Based on a two-cutting-per-fruit agronomy, this invention integrates the harvesting process of navel oranges, improving post-harvest processing efficiency. It simultaneously separates and cuts the fruit stem in a single harvesting action, achieving two-cutting for one fruit. This avoids the traditional secondary processing of the fruit stem after harvesting, significantly reducing post-harvest processing time and labor costs. Furthermore, this invention indirectly controls the clamping force by controlling the motor current in the clamping assembly, fundamentally avoiding the problems of susceptibility to mechanical impact damage, low reliability, and short lifespan associated with directly installing a thin-film pressure sensor at the clamping point. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the usage status of the navel orange harvesting end effector based on the "one fruit, two pruning" agronomy of the present invention; Figure 2 This is a schematic diagram of the structure of the navel orange harvesting end effector based on the "one fruit, two pruning" agronomy of the present invention; Figure 3 This is a schematic diagram of the clamping component in the navel orange harvesting end effector based on the "one fruit, two cuts" agronomy of the present invention. Figure 4 This is a schematic diagram of the bottom structure of the clamping component in the navel orange harvesting end effector based on the "one fruit, two cuts" agronomy of the present invention. Figure 5 This is a schematic diagram of the bottom structure of the shearing box in the navel orange harvesting end actuator based on the "one fruit, two shears" agronomy of the present invention. Figure 6 This is a schematic diagram of the lifting mechanism in the navel orange harvesting end effector based on the "one fruit, two pruning" agronomy of the present invention. Figure 7 This is a schematic diagram of the internal structure of the shearing box in the navel orange harvesting end effector based on the "one fruit, two shears" agronomy of the present invention. Figure 8 This is a schematic diagram of the blade connection in the end effector of the navel orange harvesting process based on the "one fruit, two shears" agronomy of the present invention. Figure 9 This is a schematic diagram of the cylinder connection in the end-effector of the navel orange harvesting device based on the "one fruit, two pruning" agronomy of the present invention. Figure 10 This is a schematic diagram of the full cross-sectional structure of the cylinder in the navel orange harvesting end actuator based on the "one fruit, two pruning" agronomy of the present invention. Figure 11 This is a partial cross-sectional view of the cylinder in the end-effector of the navel orange harvesting device based on the "one fruit, two pruning" agronomy of the present invention. Figure 12 This is a flowchart illustrating the harvesting method of the navel orange harvesting end effector based on the "one fruit, two pruning" agronomy of the present invention. Figure 13 This is a schematic diagram of the force analysis on the transverse diameter of navel orange in the harvesting method of the navel orange harvesting end actuator based on the one-fruit-two-cutting agronomy of the present invention; Figure 14 This is a simplified schematic diagram of the clamping component in the harvesting method of the navel orange harvesting end actuator based on the "one fruit, two pruning" agronomy of the present invention; Figure 15 This is a schematic diagram of the positive pressure at the contact points of navel oranges with different transverse diameters in the harvesting method of the navel orange harvesting end actuator based on the "one fruit, two cuts" agronomy of the present invention.

[0025] In the diagram, 1. Base, 2. Guide groove, 3. Shearing box, 4. Blade, 5. Vertical plate, 6. Clamping motor, 7. Closed-loop stepper motor controller, 8. Finger support, 9. Connecting frame, 10. Drive board, 11. Nut, 12. Lead screw, 13. Finger clamping mechanism, 14. Buffer port, 15. Tension spring, 16. Receiving frame, 17. Arc-shaped soft pad, 18. Silicone gasket, 19. Nut, 20. Lead screw, 21. Driven gear, 22. Driven gear, 23. Stepper motor 24. Sliding bushing, 25. Guide rod, 26. Cylinder, 27. Actuating connector, 28. Strip hole, 29. Drive column, 30. Slide rail, 31. Through opening, 32. Slider, 33. Actuating groove, 34. Tool holder frame, 35. Target detector, 36. Rectangular fiber optic sensor, 37. Connector, 38. Robotic arm, 39. Navel orange, 40. Slotted photoelectric sensor, 41. Sensor contact piece, 42. Slotted photoelectric sensor, 43. Sensor contact piece. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] This invention provides an end effector for harvesting navel oranges based on a two-pruning-per-fruit agronomy, such as... Figure 1 and Figure 2 As shown, the device includes a base 1 connected to a robotic arm 38 via a connector 37. A clamping assembly for holding a navel orange 39 is connected to the bottom front of the base 1. A cutting box 3 with a guide groove 2 at the front end is connected to the top of the base 1 via a lifting mechanism. A target detector 35 is fixed to the top of the cutting box 3. The target detector 35 uses a camera to capture images and software recognition to determine and locate the navel orange. Inside the cutting box 3, two sets of blades 4 located on the left and right sides of the guide groove 2 are connected via pneumatic fingers to perform cutting actions. A rectangular fiber optic sensor 36 is fixed to the bottom of the cutting box 3 near the guide groove 2 to determine whether the cutting box 3 and the blades 4 have descended to the ideal stem cutting position.

[0028] At the start of the harvesting operation, the target detector 35 identifies and locates the navel orange 39. The robotic arm 38 moves through the connector 37 to drive the end effector to the preset working position, placing the target navel orange 39 within the effective range of the clamping component. Subsequently, the clamping component clamps the target navel orange 39, and the fruit stem is simultaneously guided into the guide groove 2. Afterward, the shearing box 3 gradually approaches the base 1 under the drive of the lifting mechanism. During this process, the target navel orange 39 gradually covers the front of the rectangular fiber optic sensor 36. Once the predetermined covering area is reached, the lifting mechanism stops driving, and the pneumatic finger starts driving the upper and lower sets of blades 4 to close simultaneously, cutting off the fruit stem and cutting the stem flat with the fruit, achieving two cuts for one fruit.

[0029] Through the above-described method, the navel orange harvesting end effector of this invention, based on the "one fruit, two cuts" agronomic technique, improves post-harvest processing efficiency through integrated operation. It simultaneously completes the separation and cutting of the fruit stem in a single harvesting action, achieving "one fruit, two cuts," thus avoiding the traditional secondary processing of the fruit stem after harvesting. This significantly reduces post-harvest processing time and labor costs. It also makes harvested navel oranges easier to process and transport, providing technical support for the collaborative agronomic and agricultural machinery development of navel orange harvesting robots.

[0030] Example 1 This invention provides an end effector for harvesting navel oranges based on a two-pruning-per-fruit agronomy, such as... Figure 3 and Figure 4 As shown, the clamping assembly preferably includes a vertical plate 5 fixed to the front end of the bottom of the base 1. A clamping motor 6, fixed to the bottom of the base 1 with its output shaft facing forward, is disposed behind the vertical plate 5. A closed-loop stepper motor controller 7 is fixed on the clamping motor 6. A finger support 8 located in front of the base 1 is hinged to each of the left and right ends of the vertical plate 5. A drive plate 10 is hinged between the two finger supports 8 through a connecting frame 9. A nut 11 that runs through the front and back is fixed on the drive plate 10. A lead screw 12 that runs through the rear end of the nut 11 and is coaxially fixed to the clamping motor 6 is connected to the internal thread of the nut 11. A receiving frame 16 located outside the lead screw 12 is fixedly connected to the front of the receiving frame 16. An arc-shaped soft pad 17 with an opening facing forward is fixedly connected to the front end of the receiving frame 16. A clamping finger 13 is hinged to the front end of each finger support 8. A silicone pad 18 is fixedly attached to the side of the two clamping fingers 13 that are close to each other. A buffer opening 14 is opened at the end of the clamping finger 13 that is close to the finger support 8. The front end of the finger support 8 passes through the buffer opening 14 and is connected to the rear end of the clamping finger 13 by a tension spring 15. The position where the front end of the finger support 8 passes through the buffer opening 14 is rotatably connected to the clamping finger 13 by a pin.

[0031] Before the harvesting operation begins, based on the normal size of the target navel orange 39, the torque current of the clamping motor 6 is set by the closed-loop stepper motor controller 7. When the harvesting operation begins, the target detector 35 identifies and positions the navel orange 39. The robotic arm 38 moves through the connector 37 to drive the end effector to the preset working position, so that the target navel orange 39 is within the effective range of the clamping fingers 13 of the clamping assembly. Then the clamping motor 6 starts and drives the lead screw 12 to rotate, which drives the nut 11 and the drive plate 10 to approach the upright plate 5 through the lead screw nut pair. During this period, the connecting brackets 9 on both sides of the drive plate 10 tighten in the closing direction and tighten the two finger supports 8. After the two finger supports 8 are tightened, they drive the two clamping fingers 13 to close to clamp the target navel orange 39. During the clamping process, the output torque of the clamping motor 6 is monitored in real time. When the motor torque reaches the preset safe clamping threshold, it indicates that the navel orange has been stably clamped and the clamping force is within the damage-free range, and the clamping is considered complete. During this process, after the clamping fingers 13 clamp the target navel orange 39, the target navel orange 39 reacts and slightly spreads the two clamping fingers 13 apart, causing the rear end of the clamping fingers 13 to move slightly away from the front end of the finger support 8, thereby lengthening the tension spring 15. Then, under the action of the restoring force, the tension spring 15 drives the clamping fingers 13 to clamp the target navel orange 39, thereby improving the adaptability to navel oranges 39 of different diameters. After clamping, the front end of the receiving frame 16 and the two clamping fingers 13 form a clamping structure, and the arc-shaped soft pad 17 and the silicone pad 18 can further play a buffering role, reducing the risk of damage and increasing the friction force between the navel orange and the clamping fingers 13.

[0032] Example 2 This invention provides a navel orange harvesting end effector based on a two-pruning agronomy, which, based on Example 1, is as follows: Figure 3 As shown, a slotted photoelectric sensor 40 can also be fixed at the front end of the base 1, and a sensor contact 41 that can extend into the sensing slot of the slotted photoelectric sensor 40 can be fixed on the drive plate 10. After the clamping assembly completes one or more clamping operations and opens and releases the fruit, the clamping motor 6 continues to drive the two clamping fingers 13 to close, and at the same time the drive plate 10 moves backward. When the slotted photoelectric sensor 40 detects that the sensor contact 41 has extended in, it is recorded as the zero point position of the drive plate 10, that is, the initial closed position of the clamping assembly, so as to eliminate and correct the error accumulated by the rotation of the clamping motor 6. After the reset is completed, the clamping motor 6 drives the two clamping fingers 13 to fully open for the next clamping operation.

[0033] Example 3 This invention provides an end effector for harvesting navel oranges based on a two-pruning-per-fruit agronomy, such as... Figures 5 to 7As shown, the lifting mechanism preferably includes two nuts 19 that are fixed at intervals on the base 1 and are both vertically connected. Each of the two nuts 19 is threaded with a lead screw 20 whose upper end extends into the rear end of the shear box 3. The upper ends of the two lead screws 20 are coaxially fixed with driven gears 21. The two driven gears 21 mesh with a driving gear 22. A stepper motor 23 is coaxially fixed above the driving gear 22. Sliding bushings 24 that are vertically connected are fixed at the four corners of the shear box 3 near the stepper motor 23. Each sliding bushing 24 has a guide rod 25 that is slidably fitted inside and extends downward and is fixed to the base 1.

[0034] When the picking operation begins and the clamping assembly completes clamping, the stepper motor 23 starts and drives the drive gear 22 to rotate synchronously. When the drive gear 22 rotates, it drives the two driven gears 21 with larger diameters on both sides to rotate at different speeds. This drives the shearing box 3 to move closer to the base 1 through the lead screw nut pair composed of two lead screws 20 and two nuts 19. During the approach, the guide rod 25 on the base 1 provides guidance, so that the shearing box 3 moves down along the guide rod 25 based on the sliding bushing 24. During the descent, the target navel orange 39 gradually blocks the front of the rectangular fiber optic sensor 36. After the predetermined blocking area is reached, the stepper motor 23 stops.

[0035] Example 4 This invention provides a navel orange harvesting end effector based on a two-pruning-per-fruit agronomy, which, based on Example 3, such as... Figure 3 and Figure 5 As shown, a slotted photoelectric sensor 42 can also be fixed on the base 1, and a sensor contact 43 that can extend into the sensing slot of the slotted photoelectric sensor 42 can be fixed at the bottom of the shearing box 3. After the clamping assembly completes one or more clamping operations and opens and lowers the fruit, the stepper motor 23 continues to drive the shearing box 3 closer to the base 1. When the slotted photoelectric sensor 42 detects that the sensor contact 43 has extended in, it is recorded as the zero point position of the shearing box 3, that is, the initial position of the lifting mechanism, in order to eliminate and correct the accumulated error of the stepper motor 23 rotation. After the reset is completed, the stepper motor 23 drives the shearing box 3 to rise away from the base 1 to perform the next lowering operation.

[0036] Example 5 This invention provides an end effector for harvesting navel oranges based on a two-pruning-per-fruit agronomy, such as... Figures 8 to 11As shown, the pneumatic finger preferably includes a cylinder 26 fixed inside the shear box 3. L-shaped actuating connectors 27 are connected to the left and right sides of the cylinder 26 via longitudinal rotating shafts fixed to the shear box 3. Each actuating connector 27 has a vertically penetrating slot 28 at its closest end. A drive column 29 is fixed to the output shaft of the cylinder 26, extending longitudinally into and slidingly engaging with both slots 28. A transverse slide rail 30, fixed to the shear box 3, is provided in front of both actuating connectors 27. A through opening 31 is provided along the length direction at the bottom of the inner rail 30 corresponding to the positions of the two actuating connectors 27. Two T-shaped sliders 32 with one end extending outward are slidably fitted inside the slide rail 30. Each slider 32 has an actuating groove 33 at the end near the through opening 31. The ends of the two actuating connectors 27 that are far apart from each other extend into the two actuating grooves 33 respectively. A blade holder frame 34 is fixed at the end of each slider 32 that extends out of the slide rail 30. A blade 4 with the blade facing the guide groove 2 is fixed at both the upper and lower ends of the blade holder frame 34.

[0037] Once the harvesting operation begins and the lifting mechanism stops, the output shaft of cylinder 26 retracts and pulls back through the drive column 29 and the strip-shaped hole 28, causing one end of the two actuating connectors 27 to rotate backward. Simultaneously, the other ends of the two actuating connectors 27 move closer together, which in turn actuates the actuating groove 33 of the slider 32 through the through-hole 31, causing the two sliders 32 to move closer together along the slide rail 30. Upon closer approach, the upper two blades 4 in the two blade holder frames 34 close to cut off the fruit stem and stalk, while the lower two blades 4 close to cut the stalk flush with the fruit stem, thus completing the agronomic requirement of "two cuts per fruit" in one operation. After completion, the output shaft of cylinder 26 extends again to open and close the blades 4. Using cylinder 26 for driving, leveraging the fast response and high output force of pneumatic transmission, sufficient shearing force can be provided instantaneously to quickly cut the fruit stem, thereby improving the efficiency of a single harvesting operation.

[0038] Example 6 Harvesting method of navel oranges based on the "one fruit, two cuts" agronomy, such as... Figure 12 As shown, it includes the following steps: Step 1: The target detector 35 detects the position of the navel orange 39 on the tree, and the robotic arm 38 drives the base 1 to align the openings of the two gripping fingers 13 with the target navel orange 39 for gripping.

[0039] Step 2: After the positive pressure at the gripping point of the finger 13 reaches the preset threshold, the stepper motor 23 starts to drive the shear box 3 to move closer to the base 1; the positive pressure control method for the gripping point of the finger 13 is as follows: Under the action of the clamping mechanism, the navel orange remains balanced in the x and y planes, such as Figure 13 As shown, the clamping mechanism is symmetrical from left to right, and a mechanical equation can be established:

[0040] To establish a non-linear relationship between the clamping force and the transverse diameter of the navel orange, when the transverse diameter of the navel orange is constant, the spring 15 is set to be undeformed, and the hinge points of the clamping finger 13 and the finger support 8 are collinear, such as... Figure 14 As shown, analytical and geometric methods are used to calculate and analyze the normal force at various points on the navel orange. Taking the fixed hinge point O1 as the research object, the following are examples:

[0041] In the formula, F Ni Let N be the normal force at the i-th contact point; θ 1. θ 2 are respectively F N1 , F N2 The angle with the horizontal, (°); θ 3 is the angle between the connecting frame and the horizontal (°); L The vertical distance between the connecting frame and the fixed hinge, in mm; L 1 、L 2 are respectively F N1 , F N2 The vertical distance from the fixed hinge, in mm.

[0042] Within the normal operating range of the stepper motor (especially at low speed, in a static state, and when the current has not reached saturation), the calculation method for the clamping motor torque value T and current I is as follows:

[0043] In the formula: K t The torque constant is I The clamping current is 6 mA.

[0044] Clamping motor 6 torque value T With axial thrust F a The calculation method is as follows:

[0045] In the formula: F a The axial thrust of the lead screw 12 is N; P The lead screw has a 12-pitch lead in mm. η For transmission efficiency.

[0046] Based on the above calculation formula, the normal force at the clamping point can be derived. F N1 With clamping motor 6 current I The calculation method is as follows:

[0047] Therefore, the positive pressure at the clamping point F N1 With clamping motor current I Positive correlation, thus allowing control of the clamping motor current. I To control the positive pressure at the clamping point F N1 .

[0048] And when setting axial thrust F a The force is 60N. Calculations show the relationship between the normal pressure at each contact point and the transverse diameter of the navel orange, as follows: Figure 15 As shown, based on its changing trend, the single-point contact pressure is greatest when the navel orange's transverse diameter is 50mm or 110mm. The contact pressure of the end-effector contact point is ≤17.05N, ensuring no damage to the navel orange during clamping. With the navel orange's transverse diameter at 50mm or 110mm, and setting the clamping point positive pressure to 17.05N, the motor current is calculated. I Take the minimum value, which is the current setting value for clamping motor 6.

[0049] Theoretical calculations show that when the current is constant, as the transverse diameter of the navel orange increases, the sum of the positive pressures at the contact points gradually increases, and the difference in positive pressure is relatively small, indicating that the magnitude of the positive pressures at each clamping point of the navel orange is similar. Generally, the larger the transverse diameter and mass of the navel orange, the greater the clamping force required, which meets the requirements for navel orange clamping conditions and has engineering advantages.

[0050] Through the above methods, this invention possesses a certain degree of adaptability. The total positive pressure increases with the increase of the transverse diameter of the navel orange, thus adapting to the clamping requirements of navel oranges of different sizes. Secondly, the positive pressure at each clamping point is approximately equal in magnitude (with a small range), ensuring uniform force on the fruit and reducing the risk of damage. Finally, because the positive pressure at the clamping point is related to the input current... I Positive correlation enables precise control of the current. I This simple electrical parameter allows for direct and reliable control of the positive pressure at the clamping point, thereby enabling efficient and precise harvesting of navel oranges without damage.

[0051] Step 3: When the rectangular fiber optic sensor 36 is blocked by the navel orange 39, the cylinder 26 starts to drive the upper and lower sets of blades 4 to close simultaneously, cutting off the fruit branches and stems and cutting the stems flat at the fruit stalk, thus achieving two cuts on one fruit. After completion, the upper and lower sets of blades 4 open.

[0052] Step 4: The robotic arm 38 moves the base 1 to the fruit collection area, the two gripping fingers 13 open to release the navel orange 39, and the cutting box 3 returns to its original position away from the base 1.

[0053] Through the above methods, this invention indirectly controls the clamping force by controlling the current of the clamping motor 6, and the closed-loop stepper motor controller 7 controls the current of the clamping motor 6, realizing sensorless control of the clamping force. This fundamentally avoids the problems of easy mechanical impact damage, low reliability, and short lifespan caused by directly installing a thin-film pressure sensor at the clamping part. Furthermore, by using the mathematical relationship between the current and the positive pressure at the navel orange clamping point, combined with the extrusion mechanical characteristics of the navel orange, the range of the clamping motor current is further limited, ensuring that the navel orange harvesting end actuator of this one-fruit-two-cutting agronomy can clamp the navel orange tightly without damaging it.

Claims

1. A navel orange harvesting end effector based on a "one fruit, two pruning" agronomy, characterized in that, Includes a base (1), a clamping assembly is connected to the bottom front of the base (1), and a shearing box (3) with a guide groove (2) at the front end is connected to the base (1) via a lifting mechanism. Inside the shearing box (3), two sets of blades (4) located on the left and right sides of the guide groove (2) are connected via pneumatic fingers.

2. The navel orange harvesting end effector based on the "one fruit, two pruning" agronomy as described in claim 1, characterized in that, The clamping assembly includes a vertical plate (5) fixed to the bottom front end of the base (1). A clamping motor (6) fixed to the bottom of the base (1) with its output shaft facing forward is provided behind the vertical plate (5). A closed-loop stepper motor controller (7) is fixed on the clamping motor (6). A finger support (8) located in front of the base (1) is hinged to each of the left and right ends of the vertical plate (5). A drive plate (10) is hinged between the two finger supports (8) through a connecting frame (9). A nut (11) that runs through the front and back is fixed on the drive plate (10). A lead screw (12) that runs through the vertical plate (5) and is coaxially fixed to the clamping motor (6) is connected to the internal thread of the nut (11). A clamping finger (13) is hinged to the front end of each finger support (8).

3. The navel orange harvesting end effector based on the "one fruit, two pruning" agronomy as described in claim 2, characterized in that, The clamping finger (13) has a buffer opening (14) at one end near the finger support (8). The front end of the finger support (8) passes through the buffer opening (14) and is connected to the rear end of the clamping finger (13) by a tension spring (15). The position where the front end of the finger support (8) passes through the buffer opening (14) is rotatably connected to the clamping finger (13) by a pin.

4. The navel orange harvesting end effector based on the "one fruit, two pruning" agronomy as described in claim 2, characterized in that, The drive plate (10) is fixedly connected to a receiving frame (16) located outside the lead screw (12). The front end of the receiving frame (16) is fixedly connected to an arc-shaped soft pad (17) with the opening facing forward. The two gripping fingers (13) are fixedly attached to each other on the side that are close to each other. A silicone pad (18) is fixedly attached.

5. The navel orange harvesting end effector based on the "one fruit, two pruning" agronomy as described in claim 1, characterized in that, The lifting mechanism includes two nuts (19) fixed at intervals on the base (1) and both extending vertically. Each nut (19) is threaded with a lead screw (20) extending to the rear end of the shear box (3). Both lead screws (20) are coaxially fixed with driven gears (21) at their upper ends. A driving gear (22) meshes between the two driven gears (21). A stepper motor (23) is coaxially fixed above the driving gear (22). Sliding bushings (24) extending vertically are fixed at the four corners of the shear box (3) near the stepper motor (23). Each sliding bushing (24) has a guide rod (25) that extends downward and is fixed to the base (1) in a sliding fit.

6. The navel orange harvesting end effector based on the "one fruit, two pruning" agronomy as described in claim 1, characterized in that, The pneumatic finger includes a cylinder (26) fixed inside the shear box (3). L-shaped actuating connectors (27) are connected to the left and right sides of the cylinder (26) via longitudinal rotating shafts fixed to the shear box (3). Each actuating connector (27) has a through-hole (28) at one end. A drive column (29) is fixed to the output shaft of the cylinder (26), extending longitudinally into both slots (28) and slidingly engaging with them. The two actuating connectors (27)... A horizontal slide rail (30) fixed to the shear box (3) is provided in front. A through opening (31) is provided at the bottom of the slide rail (30) corresponding to the position of the two toggle connectors (27) along the length direction. Two T-shaped sliders (32) with one end extending outward are slidably fitted in the slide rail (30). Each slider (32) has a toggle groove (33) at the end near the through opening (31). The ends of the two toggle connectors (27) that are far apart from each other extend into the two toggle grooves (33).

7. The navel orange harvesting end effector based on the "one fruit, two pruning" agronomy as described in claim 6, characterized in that, Each slider (32) has a blade holder frame (34) fixed at one end of the slide rail (30), and a blade (4) with the blade facing the guide groove (2) is fixed at both the upper and lower ends of the blade holder frame (34).

8. The navel orange harvesting end effector based on the "one fruit, two pruning" agronomy as described in claim 2, characterized in that, The top of the shear box (3) is fixed with a target detector (35), and the bottom of the shear box (3) is fixed with a rectangular fiber optic sensor (36) near the guide groove (2).

9. The harvesting method for navel oranges based on the "one fruit, two pruning" agronomy using an end-effector, as described in claim 8, is characterized in that... Includes the following steps: Step 1: The target detector detects the location of the navel orange on the tree, and the robotic arm drives the base to align the clamping component with the target navel orange for clamping. Step 2: After the positive pressure at the clamping point of the clamping component reaches the limit value, the lifting mechanism starts to drive the shear box to move closer to the base; Step 3: When the rectangular fiber optic sensor is blocked by a navel orange, the pneumatic finger starts to drive the upper and lower sets of blades to close simultaneously, cutting off the fruit branches and stems and cutting the stems flat at the fruit stalk, achieving two cuts on one fruit. After completion, the upper and lower sets of blades open. Step 4: The robotic arm moves the base to the fruit collection area, the clamping component opens and releases the fruit, and the shearing box returns to its original position away from the base.

10. The harvesting method for navel oranges based on the "one fruit, two pruning" agronomy as described in claim 9, characterized in that, The method for controlling the positive pressure at the clamping point in step 2 is as follows: 1) Under the action of the clamping assembly, the navel orange remains balanced in the horizontal plane. The two clamping fingers clamp the navel orange on the left and right sides respectively, and each clamping finger forms two contact points, one at the front and one at the back. Based on this, the mechanical equation is established: In the formula, F N1 , F N2 , F N3 , F N4 The normal pressure at the four contact points formed by the two gripping fingers is denoted as follows: F N1 The normal force at the contact point on the right front, F N2 The normal force at the right rear contact point, F N3 The normal force at the left front contact point, F N4 The normal force at the left rear contact point. θ 1 is F N1 The angle between the X-axis and the left-right direction; Next, establish a nonlinear relationship between the clamping force and the transverse diameter of the navel orange. When the transverse diameter of the navel orange is constant, assume that the spring is undeformed and that the hinge points of the clamping fingers and the finger support are collinear, and calculate the normal force at the contact point of the navel orange. F N1 : In the formula, F a Let O1 be the axial thrust of the lead screw; and let O1 be the hinge point between the right end of the vertical plate and the finger support. L The perpendicular distance between the connecting frame and the hinge fulcrum O1 is [missing information]. L 1 、L 2 are respectively F N1 , F N2 The perpendicular distance from the hinge point O1; θ 3 is the angle between the connecting frame and the X-axis formed by the left and right directions; 2) The relationship between the clamping motor current I and the clamping motor torque T is: In the formula, K t The torque constant; And the clamping motor torque value T and the lead screw axial thrust F a The relation is: In the formula, P For the lead screw, η For transmission efficiency; Then the clamping motor current I and the axial thrust of the lead screw are obtained. F a Relationship; 3) Combine the normal pressure at the contact point obtained in 1). F N1 The clamping motor current I and the lead screw axial thrust obtained from expression 2) F a Relational expressions, merging and replacing F a Obtain the normal pressure at the contact point F N1 The relationship between the clamping motor current I and the current I is: Therefore, the normal pressure at the contact point F N1 The contact point pressure is positively correlated with the clamping motor current I, thus the contact point pressure can be controlled by controlling the clamping motor current I. F N1 .

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