Electric flexible gripping device suitable for fruit picking robot and method of operating the same

Abstract

The application discloses a kind of electric flexible gripping devices suitable for fruit picking robot, including flexible claw, claw base, connecting arm, drive round frame and bottom round frame seat, flexible claw is evenly arranged three along the bottom seat circumference, flexible claw bottom is fixedly connected on claw base, claw base is L type board frame structure, short edge end is hinged in the outer edge of drive round frame, long edge top surface is fixedly connected flexible claw, long edge end is hinged one end of connecting arm, the other end of connecting arm is hinged in the outer edge of bottom round frame seat, drive round frame is connected with the drive mechanism for driving it moves along the bottom round frame seat circumference, bottom round frame seat is cylindrical sleeve structure, drive round frame is cylindrical ring structure, bottom round frame seat tail end is connected spiral corrugated hose.The application can effectively realize the automatic picking and import collection container of fruit, improve picking efficiency, reduce labor cost, and reduce the damage rate of fruit in picking process.The invention of the device fully considers the shape and size difference of fruit, and the flexible claw gripping process is more flexible and more accurate.

Description

Technical Field

[0001] This invention relates to the field of fruit picking robot technology, to an electric flexible gripping device suitable for fruit picking robots, and to an operating method of the electric flexible gripping device suitable for fruit picking robots. Background Technology

[0002] Fruit harvesting currently faces numerous challenges, particularly for fruits high in the tree, such as kiwis, apples, and pears, which are difficult, time-consuming, and labor-intensive to pick. To address this, fruit-picking robots have emerged, driving the development of mechanical grippers. However, the invention of these grippers still presents several problems: First, most common mechanical grippers are rigid structures with complex configurations, generally used to grasp objects with a certain degree of hardness and resistance to surface damage. However, when grasping fragile or easily deformable objects, such as fruits with easily damaged skins, these rigid mechanical grippers can easily cause damage. Second, the complex structures of the mechanical grippers in currently available fruit-picking robots require multiple servo motors to coordinate from grasping the fruit, moving it above the container, to releasing it, leading to difficult maintenance and high economic costs. Third, existing fruit-picking robotic grippers take a long time to pick a single fruit at a time, and the picking process is complex and inefficient. Fourth, the methods for collecting harvested fruit are often crude and easily damage the fruit, affecting its quality and market value. Fruit is typically grabbed by robotic arms or grippers and released directly from a height into a collection container, resulting in crushing, impact, or falling, causing damage to the peel and flesh. This problem is widespread, urgently requiring a gentler and more effective collection method. Fifth, fruit-grabbing devices have limited compatibility; common devices are only compatible with specific robotic arms, lacking versatility and hindering the modular design and universality requirements of fruit-picking robots. Because the gripping device is connected to a specific robotic arm, the overall robot design is limited, increasing customization and maintenance costs. Furthermore, it restricts the combination of robotic arms and gripping devices from different manufacturers, reducing market competitiveness.

[0003] Existing flexible grippers can overcome this defect. For example, Chinese patent application CN108811743A discloses a fruit picker based on an adaptive flexible gripper. When the handle is pressed or released, the gripper tightens and relaxes. When the flexible gripper grasps the fruit, it squeezes the fruit. The outer surface of the fruit exerts a force on the inner surface of the flexible gripper. Due to the fin effect, the flexible gripper bends inward, maximizing the fit of the inner wall of the flexible gripper against the outer surface of the fruit. The squeezing force is evenly distributed across the entire outer surface of the fruit by installing flexible fingers on both sides of the activation module. The flexible fingers open and close or grip according to the airflow of the air duct module to complete the gripping and transfer of the object. This avoids the defects of rigid robotic hands causing scratches and marks on the object surface while maintaining a stable grip on the object.

[0004] However, the above structure still has the following problems: First, because it is a hand-held handle, the gripping force is easily loosened and the flexible gripper is deformed when controlling the flexible gripper, so it cannot be used to grasp large fruits, thus the flexible gripper can only grasp small fruits; second, the fruit picking method is singular and it is difficult to cooperate with the robotic arm, so the applicability is narrow; third, there is no fixed base connecting the entire flexible gripper, but the flexible material is directly pulled by the mechanical connector to grasp the fruit, which can easily lead to uneven force or cause the flexible gripper to deform unexpectedly when grasping larger fruits. Summary of the Invention

[0005] The purpose of this invention is to provide an electric flexible gripping device suitable for fruit picking robots, aiming to solve the problems existing in the prior art, such as easy relaxation of gripping force and deformation of flexible gripper, inability to grip large-volume fruits, limited fruit picking methods, difficulty in cooperating with robotic arms, and difficulty in connection and installation.

[0006] To achieve the above objectives, the present invention provides an electric flexible gripping device suitable for fruit picking robots, comprising a flexible claw, a claw base, a connecting arm, a drive circular frame, and a bottom circular frame base. Three flexible claws are evenly arranged along the circumference of the bottom circular frame base. The cross-section of the flexible claw along its length is a right-angled triangle, with the two right-angled sides pointing downwards and outwards, respectively. The bottom of the flexible claw is fixedly connected to the claw base. The claw base is an L-shaped plate frame structure, with its short side pointing downwards and its long side horizontal. The end of the short side is hinged to the outer edge of the drive circular frame. The top surface of the long side is fixedly connected to the flexible claw. One end of the connecting arm is hinged to the end of the long side, and the other end of the connecting arm is hinged to the outer edge of the bottom circular frame base. The drive circular frame is connected to a drive mechanism that drives it to move along the circumference of the bottom circular frame base. The bottom circular frame base is a cylindrical sleeve structure, and the drive circular frame is a cylindrical ring structure. A spiral corrugated hose is connected to the tail end of the bottom circular frame base.

[0007] Furthermore, the aforementioned drive mechanism includes a drive screw, a screw nut, and a drive motor. The drive motor is fixedly connected to the outside of the drive circular frame via a motor frame, and the drive motor extends axially upward from the motor frame and is fixedly connected to the screw. The screw nut, which cooperates with the screw, is fixedly connected to the outside of the drive circular frame via a screw nut seat.

[0008] Furthermore, the aforementioned flexible claw includes a right-angle frame and multiple horizontal plates fixedly connected within the fixed frame.

[0009] Furthermore, the aforementioned claw base includes two L-shaped bent plates and a connecting plate 1 fixedly connected to the top between the two L-shaped bent plates. The top of the connecting plate 1 is provided with a U-shaped groove. After the U-shaped groove is inserted into the lower end of the flexible claw, it is locked with screws. The short sides of the two L-shaped bent plates are hinged to a connecting ear 1 provided on the drive round frame.

[0010] Furthermore, the aforementioned connecting arm includes two symmetrical L-shaped plates and a connecting plate two fixedly connected between the inner sides of the two L-shaped plates. The two L-shaped plates are respectively hinged to the horizontal end of the claw seat and the connecting ear two provided on the bottom round frame seat.

[0011] Furthermore, a guide rod is fixedly connected to the aforementioned motor frame and arranged near the bottom circular frame seat. The guide rod is slidably connected to the drive circular frame via a linear bearing.

[0012] Furthermore, the aforementioned spiral corrugated hose is provided with multiple rows of staggered elastic fan blades, with each row of elastic fan blades arranged alternately and uniformly circumferentially in the same direction.

[0013] Furthermore, the aforementioned flexible claw is made of thermoplastic polyurethane elastomer (TPU), a high-molecular-weight material. The flexible claw has a cross-sectional hypotenuse length of 90mm, a height of 81mm, and a bottom short side width of 38mm. The distance between the two hinge points on the claw base is 28mm, the distance between the two hinge points on the connecting arm is 24mm, the inner diameter of the drive round frame is 56mm, the outer diameter is 76mm, and the diameter of the three hinge points is 80mm. The inner diameter of the bottom round frame base is 76mm, the outer diameter is 96mm, and the diameter of the three hinge points is 102mm. The length of the nut is 25mm.

[0014] Furthermore, a distance sensor and a camera are arranged outside the aforementioned bottom circular frame.

[0015] The operation method of the electric flexible gripper for fruit picking robots is as follows: the camera captures images of the fruit and determines its ripeness. When the ripeness index is reached, the distance between the flexible claw and the fruit is determined by the distance sensor. Based on the distance, the flexible claw is controlled to move to the corresponding fruit, and the drive motor is controlled to close the flexible claw. After closing, when the flexible claw reaches a certain position, the flexible claw is controlled to pull the fruit, causing it to fall into the spiral corrugated hose. Under the elastic buffer of multiple rows of elastic fan blades, the fruit slowly falls into the fruit tray.

[0016] The beneficial effects of the present invention are as follows: Compared with the prior art, the present invention has the following advantages:

[0017] (1) Since the device of the present invention uses a drive mechanism to control the up and down movement of the drive frame to achieve the gripping of the flexible claw, it solves the problem of uneven force or loose gripping force, and can also grip heavier fruits; the present invention can be used with robotic arms, modules and other operating components, and has a wide range of applications; the flexible claw of the invention is equipped with a claw seat and is easy to leave sufficient adjustment thread holes for adjustment in actual application, and has strong applicability.

[0018] The use of flexible claws allows for adaptive adjustment based on the shape and size of different fruits. This invention enables the gripping device to be widely used not only for one or a few types of fruit, but also for harvesting various types of fruit, thus improving the device's versatility and practicality.

[0019] (2) The flexibility and bendability of the helical corrugated pipe allow fruits to be gently grasped and moved, avoiding damage during transport. Secondly, the helical corrugated pipe can effectively collect fruits and guide them into the collection container, making the fruit picking process more efficient and convenient. Furthermore, the helical corrugated pipe can also be used with a well-designed guiding system to ensure the fruits are smoothly guided into the collection container, reducing errors and losses. In conclusion, choosing the helical corrugated pipe as the guiding device provides a more efficient and reliable fruit collection solution for fruit picking robots.

[0020] (3) The linkage-driven drive mechanism enables the rotational motion of the stepper motor to be effectively converted into the opening and closing motion of the flexible gripper. The application of this mechanism simplifies the mechanical structure, reduces energy loss, and improves the efficiency of motion transmission;

[0021] (4) A U-shaped groove is provided on the claw seat. The round holes arranged on the side of the U-shaped groove are threaded holes, which makes it convenient to tighten the flexible claw by screwing in the screw and then locking it by abutting. The position of the flexible claw can be adjusted according to the actual application scenario, which is easy to adjust and enhances the applicability.

[0022] (5) The connecting arm structure adopts two L-shaped plates with bent inner sides, which can be put into the cavity of the connecting arm with the claw seat. The structure is more compact, which makes it easier to reduce the size of the equipment and is easier to operate. Moreover, the structure is symmetrically arranged, with good rigidity and strength.

[0023] (6) Adding guide rods and linear bearings facilitates the directional movement of the circular frame and avoids the additional torque generated by the lead screw, which leads to large rotational wear and noise.

[0024] (7) The use of multiple rows of elastic fan blades in the spiral corrugated hose can provide elastic cushioning for falling fruit and prevent excessive impact from damaging the fruit skin. Attached Figure Description

[0025] Figure 1 This is a three-dimensional structural diagram (enlarged head) of the electric flexible gripping device for a fruit picking robot provided in Embodiment 1.

[0026] Figure 2 This is a three-dimensional structural diagram of an electric flexible gripping device suitable for fruit picking robots;

[0027] Figure 3 This is a front view schematic diagram of an electric flexible gripping device suitable for fruit picking robots;

[0028] Figure 4 yes Figure 3 Schematic diagram of the cross-sectional structure of the middle AA section;

[0029] Figure 5 This is a left-side view of an electric flexible gripping device suitable for fruit-picking robots;

[0030] Figure 6 This is a top view schematic diagram of an electric flexible gripping device suitable for fruit picking robots;

[0031] Figure 7 This is a schematic diagram of the three-dimensional structure of the flexible claw;

[0032] Figure 8 This is a schematic diagram of the three-dimensional structure of the claw base;

[0033] Figure 9 This is a schematic diagram of the three-dimensional structure of the connecting arm;

[0034] Figure 10 This is a schematic diagram of the flexible fan blade installation structure;

[0035] Figure 11 This is a graph of the S-curve acceleration / deceleration algorithm.

[0036] Figure 12 This is a curve graph verifying the speed of the S-curve acceleration / deceleration algorithm;

[0037] Figure 13 This is a curve graph verifying the stability of the S-curve acceleration / deceleration algorithm;

[0038] Figure 14 These are flowcharts of the traditional YOLOv5 algorithm (a) and the improved YOLOv5 algorithm (b);

[0039] Figure 15 This is a comparison graph of the improved YOLOv5 algorithm with other algorithms. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0041] Example 1: As Figure 1-10As shown, an electric flexible gripping device suitable for fruit picking robots includes a flexible claw 1, a claw base 2, a connecting arm 3, a drive frame 4, and a bottom frame base 5. Three flexible claws 1 are evenly arranged around the bottom frame base 5. The cross-section of the flexible claw 1 along its length is a right-angled triangle, with the two right-angled sides pointing downwards and outwards, respectively. The bottom of the flexible claw 1 is fixedly connected to the claw base 2. The claw base 2 is an L-shaped plate frame structure, with its short side pointing downwards and its long side horizontal. The end of the short side is hinged to the outer edge of the drive frame 4, and the top surface of the long side is fixed. A flexible gripper 1 is connected to a connecting arm 3, with one end of the connecting arm 3 hinged to its long side. The other end of the connecting arm 3 is hinged to the outer edge of the bottom circular frame 5. A driving circular frame 4 is connected to a driving mechanism 6 that drives it to move circumferentially along the bottom circular frame 5. The bottom circular frame 5 is a cylindrical sleeve structure, and the driving circular frame 4 is a cylindrical ring structure. A spiral corrugated hose 12 is connected to the tail end of the bottom circular frame 5. An interface 16 for connecting a robotic arm is provided on one side of the bottom circular frame 5. The robotic arm, which controls multiple degrees of freedom, can achieve precise positioning and gripping of the electric flexible gripping device. The spiral corrugated hose 12 is made of PVC reinforced duct with steel wire, which allows for bending and provides stable and reliable support.

[0042] Furthermore, the aforementioned drive mechanism 6 includes a drive screw 7, a screw nut 8, and a drive motor 9. The drive motor 9 is fixedly connected to the outer side of the drive frame 4 via a motor frame 10, and the motor shaft of the drive motor 9 extends upward from the motor frame 10 and is fixedly connected to the screw screw 7. The screw nut 8, which cooperates with the screw screw 7, is fixedly connected to the outer side of the drive frame 4 via a screw nut seat 11. The drive motor 9 is a stepper motor. Stepper motors have precise position control capabilities, ensuring that the gripping device accurately grasps the fruit without damaging it. Secondly, stepper motors have high reliability and stability, can work continuously and maintain a stable gripping force, and are suitable for long-term fruit picking tasks. Compared with traditional DC motors, stepper motors have lower power consumption and do not require additional energy to maintain position, contributing to energy conservation and emission reduction. The control of stepper motors is relatively simple; precise position control can be achieved by providing pulse signals, making them easy to integrate into robot systems. In addition, stepper motors are relatively inexpensive, helping to reduce the overall system manufacturing cost. By programming the movement of the stepper motor, complex gripping actions can be achieved, adapting to fruits of different shapes and sizes. Stepper motors operate with low noise, causing no interference to the surrounding environment and meeting environmental protection requirements. In conclusion, using stepper motors to control the grasping device can improve the accuracy, efficiency, and reliability of fruit-picking robots, while reducing energy consumption and manufacturing costs, making it an ideal choice. Figure 1As shown, the length of the drive screw directly affects the opening size of the gripping device, so a relatively long length is reserved to accommodate gripping fruits of different sizes. Interface 16 is fixedly connected to the outer end of the motor frame 10. Using a stepper motor, the single stepper motor simplifies the development of the control algorithm in the control system. Compared to the complexity of coordinating multiple motors, the control logic of a single motor is more direct and efficient, reducing the consumption of computing resources and improving the system's response speed and stability. This simplified control strategy also makes the programming and debugging process of the entire system easier, lowering the technical threshold.

[0043] Furthermore, the aforementioned flexible claw 1 includes a right-angle frame 101 and multiple horizontal plates 102 fixedly connected within the fixed frame. It is highly flexible, convenient for gripping, and has good gripping stability.

[0044] Furthermore, the aforementioned claw seat 2 includes two L-shaped bent plates 201 and a connecting plate 202 fixedly connected to the top between the two L-shaped bent plates 201. The top of the connecting plate 202 is provided with a U-shaped groove 204. After the U-shaped groove 204 is inserted into the lower end of the flexible claw 1, it is locked with screws. The short sides of the two L-shaped bent plates 201 are hinged to the connecting ear 203 provided on the drive circular frame 4. This claw seat is easy to install, has high rigidity and strength, does not occupy extra space, has high space utilization, drives the flexible claw to close, and the drive is stable and reliable.

[0045] Furthermore, the aforementioned connecting arm 3 includes two symmetrical L-shaped plates 301 and a connecting plate 302 fixedly connected between the inner sides of the two L-shaped plates 301. The two L-shaped plates 301 are respectively hinged to the horizontal end of the claw seat 2 and the connecting ear 303 set on the bottom round frame seat 5. The directional support has good stability, and the connecting plate is set on the inner side of the bend. The structure is compact, and the two symmetrical L-shaped plates have high rigidity and strength.

[0046] Furthermore, a guide rod 13 is fixedly connected to the motor frame 10 and arranged near the bottom circular frame seat 5. The guide rod 13 is slidably connected to the drive circular frame 4 through a linear bearing 14. The addition of the guide rod and the linear bearing facilitates the directional movement of the drive circular frame 4 and also avoids the additional torque generated by the lead screw, which would cause it to rotate and wear excessively and generate a lot of noise.

[0047] Furthermore, the spiral corrugated hose 12 is provided with multiple rows of elastic fan blades 15 arranged in an alternating manner. Each row of elastic fan blades 15 is arranged at intervals and is evenly arranged circumferentially in the same direction. The use of multiple rows of elastic fan blades 15 in the spiral corrugated hose 12 can provide elastic cushioning for falling fruit and prevent excessive impact from damaging the fruit skin.

[0048] Furthermore, the flexible claw 1 is made of thermoplastic polyurethane elastomer (TPU), a high-molecular-weight material. The flexible claw 1 has a cross-sectional hypotenuse length of 90mm, a height of 81mm, and a bottom short side width of 38mm. The distance between the two hinge points on the claw base 2 is 28mm, the distance between the two hinge points on the connecting arm 3 is 24mm, the inner diameter of the drive round frame 4 is 56mm, the outer diameter is 76mm, and the diameter of the three hinge points is 80mm, the inner diameter of the bottom round frame base 5 is 76mm, the outer diameter is 96mm, and the diameter of the three hinge points is 102mm, and the length of the nut 8 is 25mm. With these dimensions, effective and stable clamping can be achieved.

[0049] Furthermore, a distance sensor and a camera are arranged outside the aforementioned bottom circular frame 5, which can realize fruit distance detection and fruit positioning and grasping.

[0050] The motorized flexible gripper also boasts high reliability and stability. Manufactured with high-quality materials, the gripper can operate stably for extended periods, maintaining stability even under frequent use. Furthermore, the device is typically equipped with a sensor system that can perceive the fruit's position and shape in real time, allowing for more precise control of the gripping motion and improving accuracy and efficiency. Its flexible design and versatility enable the robot to adapt to fruits of different shapes and sizes, increasing the success rate and efficiency of gripping. Simultaneously, the device's high reliability and stability ensure stable operation and extended use.

[0051] Example 2: Operation method of the electric flexible gripping device applicable to fruit picking robots. The method is as follows: the camera captures images of the fruit and determines its ripeness. When the ripeness index is reached, the distance between the flexible claw and the fruit is determined by the distance sensor. Based on the distance, the flexible claw is controlled to move to the corresponding fruit, and the drive motor is controlled to close the flexible claw. After closing, when it reaches a certain position, the flexible claw is controlled to pull the fruit, causing it to fall into the spiral corrugated hose. Under the elastic buffer of multiple rows of elastic fan blades, it slowly falls into the fruit tray. The ripeness is determined using a deep learning neural network model. The deep learning neural network model is obtained after training on a large number of similar ripe fruits, which can achieve more accurate judgment and avoid picking unripe fruits.

[0052] The specific control steps of the operation method are as follows:

[0053] 1.1 Initial State Setting: Before starting the harvesting robot, ensure all components are in their initial state. The stepper motor is stopped, the flexible claw is in the closed position, the drive frame 4 and the bottom frame base 5 are in their lowest positions, and the spiral corrugated hose is connected to the collection container and ensured to be unobstructed.

[0054] 1.2 Startup Process: When the picking robot receives the start-up command, the controller activates the stepper motor. The activation of the stepper motor will trigger a series of actions to grasp the fruit.

[0055] 1.3 Execution of the grabbing action:

[0056] Step 1: The controller sends a signal to the stepper motor to make it rotate forward. The forward rotation of the stepper motor drives the drive frame 4 to move upward through the lead screw and nut.

[0057] Step 2: The movement of the drive frame 4 is driven by the linkage mechanism to open the claw of the flexible claw, preparing it to grasp the fruit;

[0058] Step 3: Once the flexible claw is fully open, the robot moves to a position beneath the target fruit. At this point, the opening of the flexible claw should match the size of the fruit to ensure effective grasping. Due to the practicality of the invented flexible claw, it can grasp most fruits.

[0059] 1.4 Fetching and Importing:

[0060] Step 1: The robot adjusts its position so that the opening of the flexible claw aligns with the fruit. Then, the controller sends another signal to the stepper motor, causing it to reverse.

[0061] Step Two: The reverse rotation of the stepper motor drives the drive frame downwards, which in turn causes the flexible claw to close. The closing action of the flexible claw tightly grips the fruit;

[0062] Step 3: After grasping the fruit, the robot moves along a preset path, directly guiding the fruit into the collection container through a spiral corrugated hose. During this process, the spiral corrugated hose guides the fruit smoothly into the collection container, preventing damage during transfer.

[0063] 1.5 Release and Cycle:

[0064] Step 1: After the fruit is successfully imported into the collection container, the controller reactivates the stepper motor, causing it to rotate forward and drive the drive frame to move upward, thereby opening the flexible claw again.

[0065] Step 2: After the flexible claw opens, the robot moves to the next target fruit location and repeats the above grasping action to achieve continuous harvesting.

[0066] 1.6 End of Harvesting: When all target fruits have been harvested or the robot receives a stop command, the controller will stop the stepper motor and the robot will enter standby mode, waiting for the next harvesting task.

[0067] Through the above process, the electric flexible gripper can effectively realize the automatic picking and loading of fruits into collection containers, improving picking efficiency, reducing labor costs, and lowering the damage rate of fruits during the picking process. This invention fully considers the differences in fruit shape and size, ensuring flexibility and accuracy in the gripping process through the adaptive gripping of the flexible claws.

[0068] The control system employed in this invention mainly comprises a microcontroller module, a stepper motor drive module, a serial communication module, and a vision recognition module. The microcontroller module connects the stepper motor drive module and the vision recognition module. An STM32 chip is used as the microcontroller, which acquires data sent by the Jetson Nano after visual recognition via a UART module and calculates the corresponding PWM duty cycle and period. Finally, the speed and torque of the stepper motor are changed by adjusting the PWM period and duty cycle to achieve the S-shaped acceleration / deceleration control algorithm. The flexible gripper is controlled using an S-shaped acceleration / deceleration control algorithm, which not only responds quickly but also exhibits stability and adaptability in different environments, effectively controlling the motor's speed and torque.

[0069] 1. Control Flow of the Control System: By setting timers, tasks are executed periodically to ensure the stability and controllability of the system. First, data frames sent by the virtual machine JETSON after visual recognition are received. Then, an S-shaped acceleration / deceleration algorithm is used to convert the fruit coordinates (x, y, z) into clearer speed and step count data. This data is then converted into PWM data for the timer module. The motor speed and torque are changed by adjusting the PWM duty cycle and period. The number of steps completed is determined through timer interrupts. Finally, the PWM signal is sent to the stepper motor driver to drive the stepper motor, completing the work of the flexible gripper.

[0070] 2. Control Algorithm: The traditional S-curve acceleration / deceleration algorithm includes seven motion stages: acceleration stage, constant acceleration stage, deceleration stage, constant speed stage, acceleration / deceleration stage, constant deceleration stage, and deceleration / deceleration stage. Although this algorithm is characterized by smoothness and high accuracy, its parameters are complex, which greatly reduces work efficiency and places high demands on hardware.

[0071] The control algorithm in this application adopts a five-segment S-curve acceleration / deceleration algorithm, such as... Figure 11 As shown, the acceleration / deceleration phase includes: acceleration phase (T1), deceleration phase (T2), constant speed phase (T3), acceleration / deceleration phase (T4), and deceleration phase (T5). This is a simple yet real-time and high-precision acceleration / deceleration control algorithm, well-suited for resource-constrained small embedded systems. Therefore, this control employs a five-segment S-curve acceleration / deceleration algorithm, which offers better speed and stability. Figure 12Under constant load, the S-shaped acceleration / deceleration algorithm of the high-speed curve motor can quickly reach the speed setpoint and operate stably. Furthermore, it can quickly respond to and reach the new speed setpoint after modification; for example... Figure 13 The stability curve shown indicates that, under a constant load, the load torque variation is relatively stable. The torque variation is quite regular before reaching a steady state; after reaching a steady state, the torque fluctuation is small, with no obvious abrupt changes, which meets the system's operational requirements.

[0072] In addition to the image acquisition for maturity assessment mentioned above, the visual recognition module also includes visual recognition and localization:

[0073] To achieve real-time fruit identification and localization, the hardware utilizes a binocular camera, and the algorithm employs an improved YOLOv5s model. By combining the improved YOLOv5s model with binocular vision technology, the identification model achieves significant improvements in accuracy, recall, and mean precision (mAP) compared to the original YOLOv5 model.

[0074] Model improvements: such as Figure 14 In (a), PANet serves as a feature fusion module in the YOLOv5 algorithm architecture, aiming to effectively integrate features at different scales. However, research indicates that PANet has shortcomings in the fusion process, especially when dealing with long-distance dependencies, where the gradient vanishing problem is particularly prominent, leading to severe information loss between network layers.

[0075] like Figure 14 (b) First, in the neck region, the original network structure was adjusted by replacing the traditional four Concat modules with BiFPN modules. The BiFPN modules enhance feature transfer and fusion through bidirectional paths from top to bottom and bottom to top, enabling the model to utilize multi-scale information more effectively. Then, a CA (Coordinate Attention) module was introduced after the BiFPN modules and CSP1_2 and CSP1_3 layers, enabling the model to focus more on features that are crucial for fruit detection.

[0076] Improved Model Validation: To evaluate the performance of the improved target detection model, the effectiveness of the improved model is verified by comparing the performance metrics of YOLOv5 and its improved versions YOLOv5-CA, YOLOv5-BIFPN, and YOLOv5-BIFPN-CA-Loss. Figure 15The graph shows the relationship between accuracy (P), recall (R), mAP, and bounding box loss (L) of these four models after training on the same dataset and the number of training iterations. As can be seen from the graph, before reaching 60 training iterations, accuracy (P), recall (R), and mAP increase rapidly, while bounding box loss (L) decreases rapidly. After exceeding 60 training iterations, the increase in parameters gradually slows down and eventually stabilizes. Compared with YOLOv5, YOLOv5-CA, and YOLOv5-BIFPN models, YOLOv5-BIFPN-CA-Loss shows varying degrees of improvement in accuracy (P), recall (R), mean precision (mAP), and bounding box loss (L), especially when compared with the original YOLOv5s model, where the performance improvement is particularly significant.

[0077] Specifically, as shown in Table 1, the YOLOv5-BIFPN-CA-Loss model achieves a significant improvement of 6.1% in accuracy, a 5% increase in recall, and a 0.04 reduction in loss compared to the original YOLOv5 model. Simultaneously, the mean precision (mAP@[0.5:0.95]) is improved by 7.3%. These optimizations encompass the ingenious application of the attention mechanism, deep optimization of the feature pyramid network, and fine-tuning of the loss function. These elements interact to significantly improve the model's detection efficiency and accuracy when handling complex scenes.

[0078] Table 1

[0079] Models P (%) R(%) Loss <![CDATA[mAP @[0.5:0.95] (%)]]> YOLOv5 88.4% 77.2% 0.039 52.5% YOLOv5-CA 90.6% 79.6% 0.037 54.5% YOLOv5-BIFPN 91.6% 79.1% 0.036 55.9% YOLOv5-BIFPN-CA-LOSS 94.5% 83.2% 0.035 59.8%

[0080] The electric flexible gripping device for fruit picking robots provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An electrically powered flexible gripping device suitable for use in a fruit picking robot, characterised in that: The device comprises flexible claws (1), claw seats (2), connecting arms (3), a driving circular frame (4), and a bottom circular frame seat (5). Three flexible claws (1) are evenly arranged along the circumference of the bottom circular frame seat (5). The cross section of the flexible claw (1) along its length direction is a right triangle. The bottom of the flexible claw (1) is fixedly connected to the claw seat (2). The claw seat (2) is an L-shaped plate structure. The short edge end of the claw seat (2) is hingedly connected to the outer edge of the driving circular frame (4). The top surface of the long edge of the claw seat (2) is fixedly connected to the flexible claw (1). The long edge end of the claw seat (2) is hingedly connected to one end of the connecting arm (3). The other end of the connecting arm (3) is hingedly connected to the outer edge of the bottom circular frame seat (5). The driving circular frame (4) is connected with a driving mechanism (6) for driving it to move along the circumference of the bottom circular frame seat (5). The bottom circular frame seat (5) is a cylindrical sleeve structure. The driving circular frame (4) is a cylindrical ring structure. The tail end of the bottom circular frame seat (5) is connected to a spiral corrugated hose (12). A plurality of rows of elastic fan blades (15) are arranged in the spiral corrugated hose (12) in a staggered manner. Each row of elastic fan blades (15) is arranged in a staggered manner. The control system of the electric flexible grabbing device comprises a visual recognition module. The hardware part of the visual recognition module adopts a binocular camera. An improved YOLOv5s model is used in the algorithm. The improved YOLOv5s model is in the YOLOv5 algorithm structure. In the neck region, the network structure of the YOLOv5s model is adjusted. Four Concat small modules are replaced by BiFPN modules. A CA module is introduced after the BiFPN module and the CSP1_2 and CSP1_3 layers. The control of the flexible claw adopts an S-shaped acceleration and deceleration control algorithm. Specifically, first, the data frame sent after visual recognition is received. Then, the S-shaped acceleration and deceleration control algorithm is used to convert the fruit coordinates (x, y, z) into speed and step data. Then, the speed and step data are converted into PWM data of the timer module. The duty cycle and period of the PWM are adjusted to change the speed and torque of the motor. The number of steps completed is determined through the timer interrupt. Finally, the PWM signal is sent to the stepper motor driver to drive the stepper motor to run, completing the work of the flexible claw. The S-shaped acceleration and deceleration control algorithm adopts a five-section S-curve acceleration and deceleration algorithm, including: a constant acceleration stage T1, a constant deceleration stage T2, a constant speed stage T3, a constant acceleration stage T4, and a constant deceleration stage T5.

2. The electric flexible gripping device suitable for a fruit picking robot according to claim 1, characterized in that: The driving mechanism (6) comprises a driving lead screw (7), a nut (8), and a driving motor (9). The driving motor (9) is fixedly connected to one side of the driving circular frame (4) through a motor bracket (10). The motor shaft of the driving motor (9) extends out of the motor bracket (10) and is fixedly connected to the lead screw (7). The nut (8) used in cooperation with the lead screw (7) is fixedly connected to one side of the driving circular frame (4) through a nut seat (11).

3. The electric flexible gripping device suitable for fruit picking robots according to claim 1, characterized in that: The flexible claw (1) comprises a right-angle frame (101) and a plurality of horizontal plates (102) fixedly connected in the fixed frame.

4. The electric flexible gripping device suitable for a fruit picking robot according to claim 1, characterized in that, The claw base (2) comprises two L-shaped bent plates (201) and a connecting plate one (202) fixedly connected between the top of the two L-shaped bent plates (201), the connecting plate one (202) is provided with a U-shaped groove (204) at the top, the U-shaped groove (204) is clamped into the lower end of the flexible claw (1) and then locked by a screw, and the short edge ends of the two L-shaped bent plates (201) are hingedly connected to the connecting single ear one (203) arranged on the driving circular frame (4).

5. The electrically powered flexible gripping device suitable for use in a fruit picking robot according to claim 1, characterized in that, The connecting arm (3) comprises two symmetric L-shaped plates (301) and a connecting plate two (302) fixedly connected between the bent inner sides of the two L-shaped plates (301), and the two L-shaped plates (301) are respectively hingedly connected to the connecting single ear two (303) arranged on the horizontal end of the claw base (2) and the bottom circular frame base (5).

6. The electrically powered flexible gripping device suitable for use in a fruit picking robot according to claim 2, characterized in that, The motor frame (10) is fixedly connected with a guide rod (13) arranged close to the bottom circular frame base (5), and the guide rod (13) is slidably connected to the driving circular frame (4) through a linear bearing (14).

7. The electrically powered flexible gripping device suitable for use in a fruit picking robot according to claim 1, characterized in that, The material of the flexible claw (1) is thermoplastic polyurethane elastomer, the cross section of the flexible claw (1) has an inclined edge with a length of 90 mm, a height of 81 mm and a bottom short side width of 38 mm, the distance between the two hinge points on the claw base (2) is 28 mm, the distance between the two hinge points of the connecting arm (3) is 24 mm, the inner diameter of the driving circular frame (4) is 56 mm, the outer diameter is 76 mm, and the diameter of the circumscribed circle of the triangle formed by the three hinge points is 80 mm, the inner diameter of the bottom circular frame base (5) is 76 mm, the outer diameter is 96 mm, and the diameter of the circumscribed circle of the triangle formed by the three hinge points is 102 mm, and the length of the nut (8) is 25 mm.

8. The electrically powered flexible gripping device suitable for use in a fruit picking robot according to claim 1, characterized in that, A distance sensor and a camera are arranged outside the bottom circular frame base (5).

9. The method of operating an electrically flexible gripping device suitable for use in a fruit picking robot according to claim 1, characterized in that, The method is: collecting the picture of the fruit by the camera, judging the maturity, when the maturity index is reached, judging the distance between the flexible claw and the fruit according to the distance sensor, controlling the flexible claw to move to the corresponding fruit according to the distance, controlling the driving motor to act, so that the flexible claw is closed, when the flexible claw is closed to the predetermined position, controlling the flexible claw to pull the fruit, so that the fruit falls into the spiral corrugated hose, and slowly falls into the fruit tray under the elastic buffer of the multiple rows of elastic fan blades.

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