Plug seedling taking end effector based on machine vision

Abstract

The invention relates to the technical field of agricultural machinery, and discloses a plug seedling taking end effector based on machine vision, which sequentially comprises a mounting seat, a first fixed support leg, a first mounting rack, a second mounting rack, a third mounting rack, a second fixed support leg and a fourth mounting rack from top to bottom, a self-adaptive clamping assembly, a visual positioning assembly and an automatic balancing assembly are arranged among the mounting base, the first fixing supporting leg, the first mounting frame, the second mounting frame, the third mounting frame, the second fixing supporting leg and the fourth mounting frame. The self-adaptive clamping assembly is arranged, a specific pressure sensor detects the contact pressure between a clamping arm and a seedling in real time, a clamping threshold value is preset according to crop varieties and fed back to an integrated control module to adjust an electric telescopic rod and drive an adjusting arm to stretch out and draw back in a fixed sliding sleeve, and then the opening and closing angle and the clamping force of the clamping arm are adjusted; the supporting spring provides flexible buffering, and impact of rigid clamping on the seedlings is avoided.

Description

Technical Field

[0001] This invention relates to the field of agricultural machinery technology, specifically to a machine vision-based end effector for retrieving seedlings from seed trays. Background Technology

[0002] In modern large-scale, automated agricultural production systems, plug seedling cultivation has become a core seedling method for vegetables, flowers, and cash crops due to its advantages of short cultivation cycles, uniform seedling growth, and high space utilization. The removal of seedlings from plug trays is a crucial step connecting the seedling cultivation and transplanting stages; its precision, efficiency, and seedling damage rate directly determine the subsequent transplant survival rate and overall planting benefits. Currently, plug seedling removal operations still face several technical bottlenecks in the industry: Most mechanical seedling-picking end effectors on the market use a fixed-size rigid clamping structure, which can only be adapted to plug seedlings of a single variety and a single growth stage. When dealing with plug seedlings of different varieties or different growth cycles, problems such as "damaging thick seedlings" or "failing to grasp thin seedlings" easily occur, resulting in extremely poor versatility. Secondly, existing actuators with visual assistance mostly use ordinary RGB cameras, which are easily affected by the fluctuation of light in the seedling shed, resulting in blurred recognition of the seedling hole outline and large positioning deviations. At the same time, dust, water mist, and seedling leaf secretions in the seedling environment can easily adhere to the lens surface. If not cleaned in time, it will further aggravate the positioning error and cause incorrect picking. Finally, in actual operation, the seedling rack surface may be slightly deformed due to long-term use, or the posture of the agricultural robotic arm may fluctuate due to mechanical vibration during operation. Existing actuators cannot sense and adjust their own horizontal posture in real time, causing the seedling picking claw to fail to be perpendicularly aligned with the seedling hole, which in turn causes damage to the root system when the seedling picking claw is inserted into the seedling hole, or the seedling tilts and falls off after picking. Summary of the Invention

[0003] The purpose of this invention is to provide a machine vision-based end effector for retrieving seedlings from plug trays, in order to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A machine vision-based end effector for retrieving seedlings from a seedling tray includes, from top to bottom, a mounting base, a first fixed leg, a first mounting frame, a second mounting frame, a third mounting frame, a second fixed leg, and a fourth mounting frame. An adaptive clamping component, a visual positioning component, and an automatic balancing component are respectively provided between the mounting base, the first fixed leg, the first mounting frame, the second mounting frame, the third mounting frame, the second fixed leg, and the fourth mounting frame. The adaptive clamping assembly is installed between the third mounting frame and the fourth mounting frame. The adaptive clamping assembly includes a cylinder, a connecting rod, an actuating gripper module and a fixed arm. The cylinder pushes and pulls the connecting rod to make the actuating gripper module rotate inside the fixed arm, thereby opening and closing one end of the actuating gripper module to clamp the seedlings in the plug tray. The visual positioning component is installed on the fourth mounting bracket. The visual positioning component includes an infrared acquisition camera and a fill light. The fill light and the infrared acquisition camera work together to detect the image in real time. The automatic balancing assembly is installed between the first mounting bracket and the second mounting bracket. The automatic balancing assembly includes several ball head fixing seats, several movable ball heads, several first connecting rods, several drive motors, second connecting rods, and an integrated control module. The first connecting rods and second connecting rods are driven by multiple drive motors and leveled with the cooperation of the movable ball heads and ball head fixing seats, so that the adaptive clamping assembly is perpendicular to the acupoint and downward.

[0005] Optionally, the cylinder is fixedly installed between the second mounting bracket and the third mounting bracket, the linkage is movably installed between the cylinder and the actuating gripper module, the actuating gripper module is movably installed on the inner side of one end of the fixed arm, and one end of the fixed arm is circumferentially connected to the fourth mounting bracket.

[0006] Optionally, the gripper module includes a fixed sliding sleeve, an adjusting arm, a clamping arm, an electric telescopic rod, a pressure sensor, and a support spring. The middle part of the fixed sliding sleeve is rotatably connected to the inner side of one end of the fixed arm. The adjusting arm is slidably connected to the inner side of the fixed sliding sleeve. One end of the clamping arm is rotatably connected to one end of the adjusting arm. The electric telescopic rod is fixedly installed on the outer wall of the fixed sliding sleeve 204. The pressure sensor is fixedly installed on one end of the clamping arm. The support spring is fixedly installed on the detection end of the pressure sensor and the side surface of one end of the adjusting arm.

[0007] Optionally, the visual positioning component further includes a cleaning nozzle, a connector, and a photoresistor. The cleaning nozzle is fixedly installed at the edge of the fourth mounting bracket, the connector is fixedly installed at the top of the third mounting bracket, and the photoresistor is fixedly installed in the middle of the fourth mounting bracket.

[0008] Optionally, several infrared acquisition cameras and supplementary lights are fixedly installed at the bottom of the fourth mounting frame, and the infrared acquisition cameras and supplementary lights are evenly distributed around the fourth mounting frame. The infrared acquisition cameras and supplementary lights are electrically connected to the integrated control module.

[0009] Optionally, one end of the cleaning nozzle passes through the interior of the second fixed leg and is connected to one end of the connector. The output ends of several cleaning nozzles are respectively directed towards the infrared acquisition camera and the supplementary light. The photoresistor is electrically connected to the integrated control module by wires.

[0010] Optionally, several of the ball head fixing seats are fixedly installed at the bottom of the second mounting frame, and the ball head fixing seats are arranged in a circular array at the bottom of the second mounting frame.

[0011] Optionally, the movable ball head is movably installed inside the ball head fixing seat, one end of the first connecting rod is fixedly connected to the bottom of the movable ball head, the drive motor is fixedly installed on the top of the first mounting bracket, one end of the second connecting rod is fixedly installed on one end of the drive motor shaft, and the other end of the second connecting rod is rotatably connected to one end of the first connecting rod.

[0012] Optionally, several of the drive motors are electrically connected to the integrated control module via wires.

[0013] Optionally, the first fixed support leg is fixedly installed at the bottom of the mounting base, the first mounting bracket is fixedly installed at the bottom of the first fixed support leg, the second mounting bracket is fixedly installed at the top of the cylinder, the third mounting bracket is located inside the first mounting bracket, the second fixed support leg is fixedly installed at the bottom of the third mounting bracket, and the fourth mounting bracket (107) is fixedly installed at the bottom of the second fixed support leg.

[0014] The present invention has at least the following beneficial effects: (1) This solution sets up an adaptive clamping component. The specific pressure sensor detects the contact pressure between the clamping arm and the seedling in real time. The clamping threshold is preset according to the crop variety and fed back to the integrated control module to adjust the electric telescopic rod, drive the adjusting arm to extend and retract within the fixed sliding sleeve, and thus adjust the opening and closing angle of the clamping arm and the clamping force; the support spring provides flexible buffering to avoid the impact of rigid clamping on the seedling. (2) This solution sets up a visual positioning component. Specifically, the infrared camera can penetrate light dust and water mist to clearly capture the outline features of the seedling hole and seedlings, avoiding the defects of ordinary RGB cameras affected by light. The photoresistor senses the ambient light intensity in real time and feeds it back to the integrated control module to dynamically adjust the supplementary light brightness to ensure the stability of image acquisition. (3) This solution sets up a visual positioning component. Specifically, the cleaning nozzle can be connected to high-pressure air or clean water through the connector to clean the lens and the light-filling surface regularly to prevent contaminants from adhering. No manual intervention is required for cleaning, ensuring the durability and accuracy of the equipment operation. (4) This solution incorporates an automatic balancing component. Specifically, when the actuator tilts due to unevenness of the working surface or mechanical vibration, the integrated control module senses the tilt angle through its internally integrated sensors, drives the corresponding drive motor, and drives the first link through the second link. Combined with the rotation of the movable ball head within the ball head fixing seat, the horizontal posture of the second to fourth mounting frames is quickly adjusted. Even on a working surface with a flatness deviation of ±3°, it can still ensure that the seedling picking claw is vertically aligned with the seedling hole, with no new deviation in the seedling picking position, effectively avoiding seedling damage and missed picking caused by posture tilt. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a partial structural diagram of the present invention; Figure 3 This is a schematic diagram of the bottom side structure of the present invention; Figure 4 This is a schematic diagram of the gripper module structure of the present invention; Figure 5 For the present invention Figure 4 A magnified view of a section at point A in the middle; Figure 6 This is a schematic diagram of the automatic balancing component structure of the present invention; Figure 7 This is a schematic diagram of the visual positioning component structure of the present invention; Figure 8 For the present invention Figure 6 A magnified view of a section at point B in the middle; Figure 9 This is a structural assembly diagram of the fourth mounting bracket of the present invention.

[0016] The attached diagram lists the components represented by each number as follows: 101. Mounting base; 102. First fixed leg; 103. First mounting bracket; 104. Second mounting bracket; 105. Third mounting bracket; 106. Second fixed leg; 107. Fourth mounting bracket; 200. Cylinder; 201. Linkage rod; 202. Actuating gripper module; 203. Fixed arm; 204. Fixed sliding sleeve; 205. Adjusting arm; 206. Grip arm; 207. Electric telescopic rod; 208. Pressure sensor; 209. Support spring; 301. Infrared acquisition camera; 302. Fill light; 303. Cleaning nozzle; 304. Connector; 305. Photoresistor; 401. Ball head fixing seat; 402. Movable ball head; 403. First connecting rod; 404. Drive motor; 405. Second connecting rod; 406. Integrated control module. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figures 1-9 This invention provides a machine vision-based end effector for retrieving seedlings from a seedling tray. From top to bottom, it includes a mounting base 101, a first fixed leg 102, a first mounting frame 103, a second mounting frame 104, a third mounting frame 105, a second fixed leg 106, and a fourth mounting frame 107. An adaptive clamping component, a visual positioning component, and an automatic balancing component are respectively provided between the mounting base 101, the first fixed leg 102, the first mounting frame 103, the second mounting frame 104, the third mounting frame 105, the second fixed leg 106, and the fourth mounting frame 107. The first fixed leg 102 is fixedly installed at the bottom of the mounting base 101, the first mounting frame 103 is fixedly installed at the bottom of the first fixed leg 102, the second mounting frame 104 is fixedly installed at the top of the cylinder 200, the third mounting frame 105 is located inside the first mounting frame 103, the second fixed leg 106 is fixedly installed at the bottom of the third mounting frame 105, and the fourth mounting frame (107) is fixedly installed at the bottom of the second fixed leg 106. The adaptive clamping assembly is installed between the third mounting bracket 105 and the fourth mounting bracket 107. The adaptive clamping assembly includes a cylinder 200, a connecting rod 201, an actuating gripper module 202, and a fixed arm 203. The cylinder 200 pushes and pulls the connecting rod 201 to make the actuating gripper module 202 rotate inside the fixed arm 203, thereby causing one end of the actuating gripper module 202 to open and close, clamping the seedlings in the plug tray.

[0019] In some embodiments, see Figure 2 , Figure 4 , Figure 5 The cylinder 200 is fixedly installed between the second mounting bracket 104 and the third mounting bracket 105. The linkage rod 201 is movably installed between the cylinder 200 and the actuating gripper module 202. The actuating gripper module 202 is movably installed on the inner side of one end of the fixed arm 203. One end of the fixed arm 203 is circumferentially connected to the fourth mounting bracket 107. The actuating gripper module 202 includes a fixed sliding sleeve 204, an adjusting arm 205, a gripping arm 206, an electric telescopic rod 207, a pressure sensor 208, and a support spring 209. The middle part of the fixed sliding sleeve 204 is rotatably connected to the inner side of one end of the fixed arm 203. The adjusting arm 205 is slidably connected to the inner side of the fixed sliding sleeve 204. One end of the gripping arm 206 is rotatably connected to one end of the adjusting arm 205. The electric telescopic rod 207 is fixedly installed on the outer wall of the fixed sliding sleeve 204. The pressure sensor 208 is fixedly installed on one end of the gripping arm 206. The support spring 209 is fixedly installed on the detection end of the pressure sensor 208 and the side surface of one end of the adjusting arm 205.

[0020] The cylinder 200 provides clamping power, converting linear motion into rotational motion of the gripper module 202 via the push-pull linkage 201, thus opening and closing the gripper arm 206. A small pneumatic cylinder 200 (such as SMCCDJ2B16-30-B) can be used. A magnetic switch (such as SMCD-M9B) is provided to detect the piston rod position of the cylinder 200 and provide feedback to the integrated control module 406. The linkage 201 connects the cylinder 200 and the gripper module 202, transmitting the power from the cylinder 200 and converting linear motion into rotational motion of the gripper module 202. The electric telescopic rod 20... 7. As the power source for precise adjustment of the opening angle and clamping force of the clamping arm 206, a miniature DC electric telescopic rod 207 (model: TJC-C1-50) is selected. It can achieve fine adjustment at the 0.1mm level through PWM pulse signal to meet the clamping needs of seedlings of different thicknesses (seedling diameter 2-10mm). The head of the telescopic rod is connected to the adjusting arm 205 through a fisheye bearing, which allows the adjusting arm 205 to produce a slight angular deviation during movement, avoiding stress concentration. It can be easily installed on the outer wall of the fixed sliding sleeve. The pressure sensor 208 monitors the contact pressure between the clamping arm 206 and the seedling in real time, providing feedback signals for the closed-loop control of the clamping force. A miniature thin-film pressure sensor 208 (model: FSS1500N) is selected to quickly capture pressure changes. It is embedded in the groove of the clamping surface of the clamping arm 206, without protruding from the clamping surface to avoid affecting the clamping fit. It adopts a four-wire output (power, ground, signal +, signal -), connected to the integrated control module 406 via a shielded cable. This ensures stable signal even in the complex electromagnetic environment of the seedling shed (such as interference from motors and solenoid valves). The support spring 209 acts as a flexible buffer element to absorb the rigid impact during the adjustment process of the electric telescopic rod 207, preventing... When the pressure sensor 208 and the seedling are subjected to excessive instantaneous pressure, one end of the spring is fixed to the protrusion of the adjusting arm 205 by welding, and the other end contacts the detection end of the pressure sensor 208 (without fixing, it can extend and retract freely). When the clamping arm 206 contacts the seedling, the spring first deforms, converting the instantaneous impact force into a gradual elastic force, so that the pressure value detected by the pressure sensor 208 rises steadily, providing sufficient adjustment time for the control module and preventing "over-clamping and damage to the seedling"; at the same time, the spring's rebound force can assist the clamping arm 206 in resetting, ensuring the accuracy of the initial position for the next clamping. It should be noted that before operation, the operator can preset the clamping pressure threshold on the touch interface of the integrated control module 406 according to the variety of plug seedlings (such as tomato seedlings, lettuce seedlings, and pepper seedlings). The threshold range covers the pressure tolerance of most common plug seedlings. During operation, regardless of the thickness or height of the seedlings, the pressure sensor 208 can capture the contact pressure between the clamping arm 206 and the seedling in real time and transmit the data to the control module. The control module calculates the adjustment amount of the electric telescopic rod 207 through a PID algorithm: if the pressure is less than the threshold, the telescopic rod is driven to extend, pushing the adjusting arm 205 to extend along the fixed slide 204, increasing the opening angle of the clamping arm 206, and increasing the clamping force; if the pressure is greater than the threshold, the telescopic rod is driven to shorten, pulling the adjusting arm 205 back, reducing the clamping force; the response time of the entire adjustment process is ≤1 second. With a frame rate of 00ms, the system can achieve "clamping and adaptation" without the need for manual replacement of the grippers or adjustment of the mechanical structure. The synergistic effect of the support spring 209 and the pressure sensor 208 constructs a "dual protection" mechanism: on the one hand, the flexible buffer of the spring changes the clamping force from "instantaneous impact" to "smooth application", avoiding the rigid adjustment of the electric telescopic rod 207 from causing indentations or breakage of the seedling stem; on the other hand, the real-time feedback of the pressure sensor 208 can strictly limit the clamping force to not exceed the preset threshold. Combined with the silicone pad and arc design of the clamping arm 206, the local pressure is further reduced; in addition, the four sets of symmetrically arranged fixed arms 203 and grippers ensure that the seedling is subjected to uniform force around its perimeter. During the clamping process, the tilt angle of the seedling is ≤1°, which is far lower than the 5° tilt limit of traditional two-point clamping, effectively preventing leaf abrasion or root loosening caused by tilting of the seedling. The visual positioning component is installed on the fourth mounting bracket 107. The visual positioning component includes an infrared acquisition camera 301 and a supplementary light 302. The supplementary light 302 and the infrared acquisition camera 301 work together to detect the image in real time. In some embodiments, see Figure 7 , Figure 9 The visual positioning component also includes a cleaning nozzle 303, a connector 304, and a photoresistor 305. The cleaning nozzle 303 is fixedly installed at the edge of the fourth mounting bracket 107, the connector 304 is fixedly installed at the top of the third mounting bracket 105, and the photoresistor 305 is fixedly installed in the middle of the fourth mounting bracket 107. Several infrared acquisition cameras 301 and supplementary lights 302 are fixedly installed at the bottom of the fourth mounting bracket 107 and are evenly distributed around the fourth mounting bracket 107. The infrared acquisition cameras 301 and supplementary lights 302 are electrically connected to the integrated control module 406. One end of the cleaning nozzle 303 passes through the interior of the second fixed support leg 106 and is connected to one end of the connector 304. The output ends of the cleaning nozzles 303 are respectively facing the infrared acquisition cameras 301 and supplementary lights 302. The photoresistor 305 is electrically connected to the integrated control module 406 by wires.

[0021] Among them, the infrared acquisition camera 301, as the core sensing element for visual positioning, needs to be able to penetrate dust, water mist and seedling leaf secretions in the seedling shed, and clearly capture the outline features of the seedling hole and the seedling. The supplementary light 302 provides a stable infrared light source for the infrared acquisition camera 301 to offset the impact of ambient light fluctuations on image quality. LED infrared supplementary light 302 (model: IR-850-3W) is selected, with an emission wavelength of 850nm (matching the infrared response wavelength of the camera to avoid low supplementary lighting efficiency caused by spectral mismatch), rated power of 3W, and brightness adjustable via PWM signal (adjustment range 10%-100%) to meet the supplementary lighting needs under different lighting environments. Cleaning nozzle 303 is used to periodically clean the lens of infrared acquisition camera 301 and the lamp cover surface of supplementary light 302 to remove attached dust, water mist and seedling leaf secretions (such as aphid honeydew, leaf sap), to avoid contaminants affecting image acquisition and supplementary lighting effects. Photoresistor 305 detects the ambient light intensity in the seedling shed in real time and provides feedback signals for brightness adjustment of supplementary light 302 to ensure the brightness stability of image acquisition. It should be noted that the infrared acquisition camera 301 and the supplementary light 302 have wavelength matching (both 850nm), enabling the supplementary light source to be efficiently received by the camera. Visible light in the environment (such as sunlight and indoor lighting) has minimal interference with the infrared camera (the response rate of visible light on the infrared sensor is ≤5%). Simultaneously, the photoresistor 305 detects the ambient light intensity in real time and converts the resistance signal into a digital signal via the AD acquisition module, transmitting it to the integrated control module 406. The control module automatically adjusts the brightness of the supplementary light 302 according to the light intensity: when the ambient light intensity is <50 lux (such as in the early morning, evening, or cloudy days), the brightness of the supplementary light 302 is adjusted to 80%-100%, ensuring that the infrared light intensity on the surface of the seedling tray is ≥200 lux, and the outline of the seedling hole is clear; when the ambient light intensity is >500 lux (such as direct sunlight at noon), the brightness is adjusted to 80%-100%, ensuring that the infrared light intensity on the surface of the seedling tray is ≥200 lux, and the outline of the seedling hole is clear; when the ambient light intensity is >500 lux (such as direct sunlight at noon), the brightness is adjusted to 80%-100%, ensuring that the brightness is ≥200 lux, and the brightness is ≥5 ... The brightness of the supplementary light 302 is adjusted to 10%-30% to avoid overexposure (grayscale saturation) and inability to distinguish the boundaries of the seedling holes. Through this dynamic adjustment mechanism, the grayscale value of the image captured by the camera can be kept stable at 120-180 (8-bit grayscale image, range 0-255) regardless of changes in ambient light. The recognition accuracy of the seedling hole outline is always above 98%, which is much higher than that of traditional RGB cameras (recognition accuracy is about 80%-85%, which fluctuates greatly due to the influence of light). The cooperation between the cleaning nozzle 303 and the connector 304 realizes "automatic cleaning without human intervention". The control module can preset the cleaning cycle (such as every 100 seedlings or every 30 minutes) or automatically trigger cleaning according to the image clarity (when the outline recognition accuracy of 5 consecutive frames is <95%, it is judged as lens contamination and cleaning is automatically started). The automatic balancing assembly is installed between the first mounting bracket 103 and the second mounting bracket 104. The automatic balancing assembly includes several ball head fixing seats 401, several movable ball heads 402, several first connecting rods 403, several drive motors 404, second connecting rods 405, and an integrated control module 406. The multiple drive motors 404 drive the first connecting rods 403 and the second connecting rods 405 to achieve leveling with the cooperation of the movable ball heads 402 and the ball head fixing seats 401, so that the adaptive clamping assembly is perpendicular to the acupoint and downwards. In some embodiments, see Figure 6 , Figure 8 Several ball joint fixing seats 401 are fixedly installed at the bottom of the second mounting bracket 104, and the ball joint fixing seats 401 are arranged in a circular array at the bottom of the second mounting bracket 104. The movable ball joint 402 is movably installed inside the ball joint fixing seat 401. One end of the first connecting rod 403 is fixedly connected to the bottom of the movable ball joint 402. The drive motor 404 is fixedly installed at the top of the first mounting bracket 103. One end of the second connecting rod 405 is fixedly installed at one end of the shaft of the drive motor 404, and the other end of the second connecting rod 405 is rotatably connected to one end of the first connecting rod 403. Several drive motors 404 are all electrically connected to the integrated control module 406 by wires.

[0022] The integrated control module 406 integrates attitude detection, signal processing, and power drive functions, serving as the core for achieving automatic balancing and coordinated operation of various components. The core processor is an STM32F103C8T6 microcontroller, boasting strong computing power and capable of simultaneously processing multiple sensor signals and control commands. The module integrates an MPU6050 six-axis sensor (including a 3-axis accelerometer and a 3-axis gyroscope) to detect the tilt angle and angular velocity of the actuator. Data fusion via Kalman filtering achieves a tilt angle detection accuracy of ±0.05°. It also integrates a 12-bit resolution AD acquisition module with a 1MHz sampling rate to acquire signals from the pressure sensor 208 and photoresistor 305. The PWM output module has eight independent PWM channels to control the drive motor 404, the electric telescopic rod 207, and the supplementary lighting 302. The serial communication module has two UART interfaces with a maximum baud rate of 115200bps for communication with the infrared camera 301 and external agricultural robotic arms. The module's 12V power supply is converted to 5V and 3.3V via a DC-DC module. Power is supplied to each component. The module is installed in the inner groove of the first mounting bracket by M3 screws, which protects the module from external impact and does not occupy external space. The integrated control module 406 has a built-in MPU6050 six-axis sensor to detect the tilt angle and angular velocity of the actuator in real time. By fusing the data through Kalman filtering algorithm, the tilt angle detection accuracy can reach ±0.05°, which can quickly capture the attitude deviation caused by uneven working surface or mechanical vibration. When the sensor detects the tilt of the actuator, the integrated control module calculates the number of rotation steps of the three sets of drive motors 404 through inverse kinematics algorithm. The drive motor drives the second link 405 to rotate, which in turn pulls the first link 403. Combined with the free rotation of the movable ball head 402 in the ball head fixed seat 401, the overall attitude of the second mounting bracket 104 to the fourth mounting bracket 107 is adjusted. Finally, the core of the adaptive clamping component, the execution gripper module, is kept vertically downward relative to the cavity plate to complete the leveling. It should be noted that the three sets of ball head fixing seats 401 and movable ball head 402 are arranged symmetrically at 120° to form a triangular support structure. Compared with the traditional two-point support or four-point support, the triangular structure has unique geometric stability, which can avoid posture swaying caused by "over-constraint" or "under-constraint" during the adjustment process. Posture tilting is one of the main reasons for root damage to the seedling claw and seedling detachment. When the seedling claw is not perpendicular to the seedling hole, the angle deviation of the seedling claw inserted into the seedling hole will scratch the seedling root system. At the same time, the seedling is prone to tilting and falling off due to uneven force after clamping. This automatic balancing component can ensure the perpendicularity between the seedling claw and the seedling hole. With a straightness deviation of ≤0.5°, the seedling picker can be inserted along the central axis of the seedling hole, avoiding root damage. Experimental comparison shows that with a flatness deviation of ±3° on the working surface, the root damage rate during seedling picking is about 15% and the seedling drop rate is about 8% when the actuator without the automatic balancing component is installed. However, after installing this component, the root damage rate drops to below 3% and the drop rate drops to below 1%. In addition, during the process of the robotic arm transporting seedlings, even if the robotic arm vibrates slightly, the balancing component can still adjust the posture in real time to ensure that the seedling always remains vertical, avoiding damage to the leaves and other parts due to tilting.

[0023] The working process and principle of this invention: Before operation, the actuator is fixed to the end flange of the external agricultural machinery arm through the mounting base 101, and the pipeline connection of the compressed air pipe of the cylinder 200, the high-pressure air pipe of the cleaning nozzle 303, and the 12V power supply of the integrated control module 406 is completed. At the start of the operation, the external robotic arm moves the actuator to directly above the target seedling tray according to the preset path. After receiving the "positioning ready" signal from the robotic arm, the integrated control module 406 controls four sets of infrared acquisition cameras 301 to acquire five frames of images at 30fps. After median filtering to remove noise, binarization to distinguish the seedling hole from the background, Canny edge detection to extract the contour, and establishing a coordinate system to calculate the center coordinates of the seedling hole, if the coordinate deviation of five consecutive frames is > ±0.3mm, the cleaning nozzle 303 is activated to spray air for 2 seconds and then re-acquire images until the positioning is accurate. On the other hand, the MPU6050 detects the tilt angle of the actuator every 10ms. If it is > ±0.1°, the control module calculates the number of rotation steps of the three sets of drive motors 404 through the inverse kinematics algorithm. The drive motors 404 drive the second link 405 and the first link 403, and adjust the second mounting bracket 104 to the horizontal position in combination with the cooperation of the movable ball head 402 and the ball head fixing seat 401. The adjustment response time is ≤500ms. After achieving posture balance, the robotic arm lowers the actuator to a distance of 20-30mm from the seedling tray. The control module extends the piston rod of the cylinder 200 (thrust force 125N), which, through the linkage rod 201, pushes the actuator gripper module 202 to rotate around the bearing of the fixed arm 203, causing the four sets of gripping arms 206 to pre-open to 30°. At the same time, the electric telescopic rod 207 is adjusted to an initial length of 20mm. The robotic arm continues to descend, allowing the gripping arms 206 to fit against the seedling stem. The pressure sensor 208 transmits the detected contact pressure to the control module via the AD acquisition module. If the pressure is less than a preset threshold, the electric telescopic rod 207 is driven to extend, increasing the clamping force; if it is greater, it is shortened, decreasing the clamping force. The support spring 209 provides flexible buffering to avoid sudden pressure changes, and the pressure deviation of the four sets of gripping arms 206 is controlled within ±0.5N. After the pressure stabilizes at the threshold for 3 seconds, the control module sends a clamping ready signal to the robotic arm. The robotic arm rises at a uniform speed of 50mm / s to pull the seedling. If a sudden drop in pressure is detected, the ascent stops.After seedling removal, the robotic arm with actuators transports the seedlings to the target transplanting location (speed 0.3-0.5 m / s). During transport, the MPU6050 continuously monitors the posture, and if vibration or airflow causes tilting, the automatic balancing component compensates and adjusts in real time. Upon reaching the target location, the control module controls the piston rod of cylinder 200 to retract (pull force 95N), which, through the linkage rod 201, pulls the actuator gripper module 202 to rotate in the opposite direction, causing the gripper arm 206 to open to 60° and release the seedling. If continuous operation is required, the robotic arm with actuators returns to the top of the seedling tray and repeats the process. If the clamping pressure exceeds the threshold by 1.5 times, positioning fails for 10 consecutive frames, or the balance adjustment still exceeds the tolerance after 10 attempts, the control module immediately takes emergency measures (forced pressure adjustment, shutdown alarm). At the same time, it automatically records the operation time, number of seedlings taken, transplanting success rate, number of failures, and average clamping pressure and positioning deviation. The data can be exported or wirelessly transmitted to the cloud to provide a basis for subsequent optimization and maintenance.

[0024] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A machine vision-based end effector for retrieving seedlings from plug trays, characterized in that, From top to bottom, the system includes a mounting base (101), a first fixed leg (102), a first mounting bracket (103), a second mounting bracket (104), a third mounting bracket (105), a second fixed leg (106), and a fourth mounting bracket (107). An adaptive clamping assembly, a visual positioning assembly, and an automatic balancing assembly are respectively provided between the mounting base (101), the first fixed leg (102), the first mounting bracket (103), the second mounting bracket (104), the third mounting bracket (105), the second fixed leg (106), and the fourth mounting bracket (107). The adaptive clamping assembly is installed between the third mounting bracket (105) and the fourth mounting bracket (107). The adaptive clamping assembly includes a cylinder (200), a connecting rod (201), an actuating gripper module (202), and a fixed arm (203). The cylinder (200) pushes and pulls the connecting rod (201) to make the actuating gripper module (202) rotate inside the fixed arm (203), thereby causing one end of the actuating gripper module (202) to open and close to clamp the seedlings in the plug tray. The visual positioning component is installed on the fourth mounting bracket (107). The visual positioning component includes an infrared acquisition camera (301) and a fill light (302). The fill light (302) and the infrared acquisition camera (301) work together to detect the image in real time. The automatic balancing assembly is installed between the first mounting bracket (103) and the second mounting bracket (104). The automatic balancing assembly includes several ball head fixing seats (401), several movable ball heads (402), several first connecting rods (403), several drive motors (404), second connecting rods (405), and an integrated control module (406). The first connecting rods (403) and second connecting rods (405) are driven by the multiple drive motors (404) and leveled with the cooperation of the movable ball heads (402) and the ball head fixing seats (401), so that the adaptive clamping assembly is perpendicular to the acupoint and downward.

2. The end effector for retrieving seedlings from plug trays based on machine vision according to claim 1, characterized in that: The cylinder (200) is fixedly installed between the second mounting bracket (104) and the third mounting bracket (105). The linkage rod (201) is movably installed between the cylinder (200) and the actuating gripper module (202). The actuating gripper module (202) is movably installed on the inner side of one end of the fixed arm (203). One end of the fixed arm (203) is circumferentially connected to the fourth mounting bracket (107).

3. The end effector for retrieving seedlings from plug trays based on machine vision according to claim 1, characterized in that: The gripper module (202) includes a fixed sliding sleeve (204), an adjusting arm (205), a clamping arm (206), an electric telescopic rod (207), a pressure sensor (208), and a support spring (209). The middle part of the fixed sliding sleeve (204) is rotatably connected to the inner side of one end of the fixed arm (203). The adjusting arm (205) is slidably connected to the inner side of the fixed sliding sleeve (204). One end of the clamping arm (206) is rotatably connected to one end of the adjusting arm (205). The electric telescopic rod (207) is fixedly installed on the outer wall of the fixed sliding sleeve (204). The pressure sensor (208) is fixedly installed on one end of the clamping arm (206). The support spring (209) is fixedly installed on the detection end of the pressure sensor (208) and the side surface of one end of the adjusting arm (205).

4. The end effector for retrieving seedlings from plug trays based on machine vision according to claim 1, characterized in that: The visual positioning component also includes a cleaning nozzle (303), a connector (304), and a photoresistor (305). The cleaning nozzle (303) is fixedly installed at the edge of the fourth mounting bracket (107), the connector (304) is fixedly installed at the top of the third mounting bracket (105), and the photoresistor (305) is fixedly installed in the middle of the fourth mounting bracket (107).

5. The end effector for retrieving seedlings from plug trays based on machine vision according to claim 1, characterized in that: Several infrared acquisition cameras (301) and fill lights (302) are fixedly installed at the bottom of the fourth mounting bracket (107). Several infrared acquisition cameras (301) and fill lights (302) are evenly distributed on the fourth mounting bracket (107). The infrared acquisition cameras (301) and fill lights (302) are electrically connected to the integrated control module (406).

6. The end effector for retrieving seedlings from plug trays based on machine vision according to claim 4, characterized in that: One end of the cleaning nozzle (303) passes through the interior of the second fixed support leg (106) and is connected to one end of the connector (304). The output ends of several cleaning nozzles (303) are respectively facing the infrared acquisition camera (301) and the supplementary light (302). The photoresistor (305) is electrically connected to the integrated control module (406) by wires.

7. The end effector for retrieving seedlings from plug trays based on machine vision according to claim 1, characterized in that: Several ball head fixing seats (401) are fixedly installed at the bottom of the second mounting frame (104), and the ball head fixing seats (401) are arranged in a ring array at the bottom of the second mounting frame (104).

8. The end effector for retrieving seedlings from plug trays based on machine vision according to claim 1, characterized in that: The movable ball head (402) is movably installed inside the ball head fixing seat (401). One end of the first connecting rod (403) is fixedly connected to the bottom of the movable ball head (402). The drive motor (404) is fixedly installed on the top of the first mounting bracket (103). One end of the second connecting rod (405) is fixedly installed on one end of the shaft of the drive motor (404). The other end of the second connecting rod (405) is rotatably connected to one end of the first connecting rod (403).

9. The end effector for retrieving seedlings from plug trays based on machine vision according to claim 1, characterized in that: Several of the drive motors (404) are electrically connected to the integrated control module (406) via wires.

10. The end effector for retrieving seedlings from a plug tray based on machine vision according to claim 1, characterized in that: The first fixed support leg (102) is fixedly installed at the bottom of the mounting base (101), the first mounting bracket (103) is fixedly installed at the bottom of the first fixed support leg (102), the second mounting bracket (104) is fixedly installed at the top of the cylinder (200), the third mounting bracket (105) is located inside the first mounting bracket (103), the second fixed support leg (106) is fixedly installed at the bottom of the third mounting bracket (105), and the fourth mounting bracket (107) is fixedly installed at the bottom of the second fixed support leg (106).

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