Sapling hoisting safety and quality monitoring method based on unmanned aerial vehicle automatic unhooker

Abstract

This invention discloses a method for monitoring the safety and quality of seedling lifting based on an automatic unhooking device for unmanned aerial vehicles (UAVs), belonging to the field of tree transplanting technology. The method includes step-by-step sensor installation and debugging, seedling diameter screening, pre-transport overweight warning, aerial risk control, and automatic unhooking monitoring. It achieves automated seedling diameter screening by deploying a ring-shaped flexible pressure sensor array on the inner side of the double hooks of the automatic unhooking device, combined with logic for judging pressure distribution uniformity and coverage. A tension sensor is connected in series between the UAV and the unhooking device to construct a full-process safety monitoring system for lifting. The UAV flight control system is linked to achieve overweight warning, wind interference return, and dual verification of unhooking effectiveness. This invention solves the problems of difficult seedling transportation in complex terrain, high lifting safety risks, and low efficiency in seedling quality inspection. It improves operational safety and efficiency, reduces manpower input, and is suitable for large-scale afforestation in ecological engineering projects such as coastlines and wetlands.

Description

Technical Field

[0001] This invention relates to the field of tree transplanting equipment technology, and more specifically, to a method for monitoring the safety and quality of seedling transport based on an automatic unhooking device from a drone. Background Technology

[0002] In ecological projects such as coastal ecological restoration and wetland vegetation reconstruction, large-scale afforestation is a core means to improve the regional ecological environment and enhance the ability to fix sand and protect beaches. However, beach areas are mostly composed of soft sandy soil, while wetlands have large areas of muddy mudflats and waterlogged areas. Such terrain has extremely low carrying capacity, making it difficult for conventional wheeled or tracked seedling transport vehicles to pass, which poses a significant bottleneck to seedling transportation. If large-scale seedling transfer and planting are carried out manually, it not only requires a large investment of manpower but also has extremely low efficiency, making it difficult to meet the time requirements of large-scale afforestation. Although utility model patent CN202121231189.7 discloses an "automatic unhooking hook for drone-borne items" and utility model patent CN202420549612.5 discloses an "automatic unhooking device," both of which can automatically unhook items carried by drones after they reach their destination. Theoretically, they can work with drones to transport saplings and overcome transportation limitations in complex terrain. However, these two devices only focus on the basic function of "lifting and unhooking." The supporting transportation methods lack a safety monitoring mechanism for the entire lifting process. They cannot perceive and control key parameters such as the drone's load status and the stability of the suspended items in real time, making it difficult to avoid safety risks caused by attitude imbalance due to overloading, excessive wind, etc. during the lifting process.

[0003] Meanwhile, the survival rate of transplanted seedlings is closely related to their specifications, especially the diameter at ground level (DBR), which needs to be controlled within a specific range. This is a core quality indicator in the seedling procurement process. However, since seedlings are mostly purchased in bulk, the sheer number makes it cumbersome, time-consuming, and inefficient to manually measure each seedling with calipers, and data errors are easily caused by human error. Furthermore, if seedlings with smaller diameters are mixed into the afforestation batch, the overall afforestation quality will be reduced. Therefore, it is necessary to develop an automated method for detecting seedling diameter to simplify the testing process, improve accuracy and efficiency, and control seedling quality from the source. Summary of the Invention

[0004] The purpose of this invention is to provide a method for monitoring the safety and quality of seedling transport based on an automatic unhooking device for unmanned aerial vehicles (UAVs), thereby solving the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: An existing automatic unhooking device includes a pair of hooks hinged together, a pair of connecting rods, an elastic pull member, and a top handle. The hooks consist of a lower arc-shaped hook and an upper hook handle. The two hooks are hinged at the connection between the arc-shaped hook and the hook handle. The two connecting rods are hinged together at one end and connected to the top handle, and the other ends are respectively hinged to the hook handle of one hook. The elastic pull member is connected between the hinge between the hooks and the hinge between the connecting rods.

[0006] A method for safety and quality control monitoring of seedling lifting based on drone-based automatic unhooking devices includes the following steps: S1. Sensor Installation and System Debugging: Symmetrically arrange the annular flexible pressure sensors on the inner clamping surfaces of the automatic release hooks, ensuring that the sensor array completely covers the entire arc-shaped hook surface, and that there are no fewer than 3 sensors on each side, forming a full-area pressure acquisition network; connect the tension sensor in series between the load attachment point on the bottom of the UAV and the hoisting rope connecting the automatic release hook; check the communication connections between each sensor and the main control chip and the UAV flight control system to ensure smooth signal transmission; S2. Precise Screening of Seedling Diameter: An automatic unhooking device with a diameter 15%-25% larger than the required trunk diameter is selected. Before transportation, a trunk with the lowest standard diameter is used for calibration. The trunk, at 2 / 3 of its height from the root, is placed into the double hook of the automatic unhooking device. The connecting rods on both sides are held and gently pressed to close the double hooks, initially securing the trunk within them. The drone is activated and applies an initial upward lifting force, which is transmitted to the double hook assembly, ensuring full contact between the annular flexible pressure sensor array and the trunk surface, generating pressure. The main control chip collects the pressure value of each pressure sensor in real time, recording the pressure distribution characteristics corresponding to the diameter's uniformity and coverage, and writes this information into the main control chip as a judgment criterion. The uniformity satisfies the following formula: Uniformity = Minimum pressure on one side / Maximum pressure on one side The coverage rate satisfies the following formula: Coverage = Number of pressure sensors / Total number of sensors The closer the uniformity is to 1 and the higher the coverage, the more uniform the contact between the trunk and the double hooks, and the better the trunk diameter matches the space inside the hooks. Before transportation, the main control chip collects data in real time on the uniformity and coverage of the saplings to be hoisted and compares them with preset qualification standards. If both parameters meet the set standards, the trunk diameter is determined to be up to standard. The main control chip immediately communicates with the UAV flight control system and sends a "quality qualified" signal to trigger subsequent transportation instructions. If the parameters do not meet the standards, the trunk diameter is determined to be too small. In this case, to clamp the small trunk, only some sensors are under pressure, while the other sensors have almost no pressure because they are not in contact with the trunk, resulting in a large pressure distribution. In this situation, the main control chip sends a "quality unqualified" signal. After receiving the signal, the UAV flight control system controls the UAV to descend until the sapling touches the ground. The automatic release device opens automatically, and the operator removes the unqualified sapling, replaces it with a qualified sapling, and then re-clamps and judges the sapling. S3. Overweight warning before drone transport: The flight control system presets a safe load threshold; while determining that the trunk diameter meets the standard, the tension sensor monitors the weight of the sapling in real time and uploads the data to the drone flight control system simultaneously; if the tension value is not greater than the safe load threshold, the flight control system controls the drone to start and transport the sapling to the designated location according to the preset route; if the tension value is greater than the overload threshold, the flight control system controls the drone to stop taking off and descend slowly until the sapling touches the ground, and the automatic unhooking device opens to release the sapling; S4. Drone Aerial Dynamic Risk Control: During drone flight, the tension sensor continuously collects lifting tension data and uploads it to the flight control system. The preset fluctuation threshold range is ±10% of the tension when the sapling just leaves the ground. When the wind is too strong, it will exert lateral tension on the sapling during lifting, causing the tension sensor to abnormally increase the value collected, exceeding the preset fluctuation threshold range. When the tension value is detected to exceed this threshold, it is determined that the current transportation environment is unsafe and not suitable for continued transportation. At this time, the flight control system automatically sends a "risk warning" signal to the ground control terminal and controls the drone to adjust its flight attitude and return to base to avoid the drone from becoming unstable and crashing due to wind. S5. Automatic Unhooking Monitoring: When the drone carrying the sapling arrives at the target afforestation location, it descends slowly until the sapling touches the ground. The lifting tension disappears instantly, and the automatic unhooking device automatically opens, enabling the sapling to unhook automatically. The main control chip monitors the pressure changes of the ring-shaped flexible pressure sensor array in real time. After unhooking, the sensor loses contact with the trunk, and the pressure value drops sharply. At the same time, the tension value detected by the tension sensor also drops sharply from the value corresponding to the weight of the sapling to close to 0. After the pressure of the pressure sensor array drops sharply and stabilizes in the low value range, and the tension sensor continues to detect that the tension value drops below the preset unhooking threshold, and no abnormal increase in tension value is detected during the subsequent take-off and return of the drone, it is determined that the unhooking was successful, indicating that the sapling has landed smoothly without being caught on branches, leaves, etc. The flight control system controls the drone to return to the starting point normally. If the pressure of the pressure sensor array does not drop significantly, or if the tension sensor detects that the tension value drops to the threshold and then increases abnormally, it is determined that the unhooking failed, an alarm is sent, and an attempt is made to unhook again or the operator is asked to troubleshoot the fault on-site. In summary, compared with the prior art, the beneficial effects of the present invention are: This invention utilizes a drone equipped with an automatic unhooking device to transport saplings. A series of tension and pressure sensors are simultaneously connected to create a comprehensive safety monitoring system covering the entire process: before transport, during flight, and after unhooking. Before transport, the tension sensor monitors the sapling weight in real time. If the weight exceeds the limit, an early warning is triggered, and the drone is forced to descend, preventing the risk of instability and crashes due to overloading. During flight, abnormal fluctuations in the tension value are monitored to accurately detect wind interference, automatically initiating a return-to-home procedure to effectively avoid flight hazards in harsh environments. After unhooking, the dual signal changes from the pressure and tension sensors verify the unhooking effect, promptly identifying and addressing unhooking failures to prevent secondary risks caused by the drone returning with debris. This system successfully overcomes the limitations of transportation in complex terrain, efficiently solving the transportation difficulties faced by conventional sapling transport vehicles in areas such as beaches and wetlands. It enables automated transport of large quantities of saplings—operators only need to load the saplings at the lifting point, and the entire subsequent process requires no manual intervention, significantly reducing manpower and material resources. Simultaneously, it significantly improves the safety factor of drone transport operations, reduces transport risks, and enhances operational safety. Furthermore, by installing pressure sensors inside the automatic unhooking device, this invention deeply integrates seedling quality inspection with the hoisting process, avoiding the problem of low survival rate caused by poor seedling quality from the source, eliminating unnecessary inspection steps, and significantly improving afforestation efficiency in complex terrain. Attached Figure Description

[0007] Figure 1 This is a structural diagram of an existing automatic unhooking device; Figure 2 A flowchart illustrating a method for monitoring the safety and quality of seedling transport using an automatic unhooking device based on a drone; Detailed Implementation

[0008] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for illustration and explanation only and are not intended to limit the present invention.

[0009] like Figure 1 As shown in the diagram, an existing automatic unhooking device includes a pair of hooks 1 hinged together, a pair of connecting rods 2, an elastic pull member 3, and a top handle 4. The hooks 1 are composed of a lower arc-shaped hook 5 and an upper hook handle 6. The two hooks 1 are hinged at the connection between the arc-shaped hook 5 and the hook handle 6. The two connecting rods 2 are hinged together at one end and connected to the top handle 4, and the other ends are respectively hinged to the hook handle 6 of the hooks 1. The elastic pull member 3 is connected between the hinge between the hooks 1 and the hinge between the connecting rods 2.

[0010] like Figure 2 As shown, the method for monitoring the safety and quality of seedling transport based on the automatic unhooking device of a drone includes the following steps: S1 sensor installation and system debugging, S2 accurate screening of seedling diameter, S3 overweight warning before drone transport, S4 drone aerial dynamic risk prevention and control, and S5 automatic unhooking monitoring. Specific Implementation

[0012] This embodiment takes the hoisting operation of 1-2 year old black pine seedlings in a coastal ecological restoration project as an example to illustrate the specific implementation process of the present invention. The equipment parameters used are as follows: the qualified standard for seedlings is that the trunk diameter at 2 / 3 of the height from the root is 40-50mm, the safe load-bearing threshold of the UAV is set to 1.6kg, the diameter of the automatic unhooking device is 60mm, and the flight control preset tension fluctuation threshold during hoisting is ±10%.

[0013] Step S1: Sensor Installation and System Debugging: Attach 10 annular flexible pressure sensors to the inner arc-shaped retaining surface of the arc hook 5 of the automatic unhooking device, 5 sensors on each side, for a total of 10 sensors on both sides, ensuring that the sensors completely cover the hook surface; connect the tension sensor in series with the anti-torsion universal joint via a quick-release buckle between the load attachment point on the bottom side of the UAV and the hoisting rope; start the main control chip and the UAV flight control system to perform a communication link test, ensuring that the signal transmission delay is no greater than 100ms; under no-load conditions, record the zero-point values ​​of the pressure sensor and the tension sensor to complete the zero-point calibration.

[0014] Step S2: Precise Screening of Seedling Diameter: First, establish a qualified benchmark. Select seedlings with a trunk diameter of approximately 40mm at 2 / 3 of the height from the root. Insert the seedlings into the double hooks of the release device and close the automatic release device. The drone is activated and applies an initial upward lifting force. This force is transmitted to the double hook assembly, ensuring full contact between the annular flexible pressure sensor array and the trunk surface, generating pressure. The main control chip collects the pressure value of each pressure sensor in real time, calculates the pressure distribution uniformity difference between the two sides of the sensors, and the overall pressure coverage rate. The uniformity satisfies the following formula: Uniformity = Minimum pressure on one side / Maximum pressure on one side The coverage rate satisfies the following formula: Coverage = Number of pressure sensors / Total number of sensors The closer the uniformity is to 1 and the higher the coverage, the more uniform the contact between the trunk and the double hooks, and the better the trunk diameter matches the space inside the hooks. The pressure values ​​at various points of the ring-shaped flexible pressure sensor array were collected. The uniformity of the sapling with a trunk diameter of about 40mm at 2 / 3 height from the root was measured to be 0.8, and the coverage rate was 90%. The criteria for judging the sapling to be qualified are: uniformity not less than 0.8 and coverage rate not less than 90%.

[0015] During the actual hoisting process, quality screening is carried out simultaneously. The operator places the black pine sapling at 2 / 3 of its height from the root (about 60cm from the root) between the double hooks, holds the connecting rod and gently presses to close the double hooks; the drone is started to fly upwards, pulling the sapling. The ring flexible pressure sensor array detects a uniformity of 0.92 on the left and 0.93 on the right, with 9 sensors showing pressure, indicating a coverage rate of 90%, which meets the benchmark requirements. The trunk diameter is judged to be up to standard, and the main control chip immediately communicates with the drone flight control system to send a "quality qualified" signal, triggering subsequent transportation instructions. If the detection data of another sapling is: uniformity of 0.7 on the left and 0.72 on the right, with 7 sensors showing pressure, indicating a coverage rate of 70%, the diameter is judged to be too small. The flight control system controls the drone to descend until the sapling touches the ground, and the unhooking device automatically opens under the action of the spring. The operator removes the sapling, replaces it with a qualified sapling, and then re-clamps and judges it.

[0016] Step S3: Overweight Warning Before Drone Transport: While determining that the trunk diameter meets the standard, the tension sensor monitors the weight of the sapling in real time and uploads the data synchronously to the drone flight control system. If the detected tension value is 1.2 kg, which is less than the drone's safe load threshold of 1.6 kg, the flight control system will control the drone to transport the sapling from the lifting point to the afforestation site along the preset route. For example, if the detected tension value of a sapling with a root ball is 2.1 kg, which is greater than the drone's safe load threshold of 1.6 kg, the flight control system will immediately trigger an alarm, control the drone to slowly descend to the ground, release the sapling using the release mechanism, and the operator will remove approximately 0.6 kg of the outer soil from the root ball. After re-locking, the detected tension value is 1.5 kg, which meets the requirements, and transport will then commence.

[0017] Step S4: Drone in-flight dynamic risk control: During the drone's flight, the tension sensor continuously collects lifting tension data and uploads it to the flight control system. When the drone is halfway through its flight, 1km from the lifting point, it encounters a gust of wind, and the tension value suddenly increases from 1.5kg to 1.7kg, an increase of 11.3%, exceeding the flight control's preset tension fluctuation threshold of ±10% during lifting. The flight control determines that the transportation environment is unsafe, immediately sends a "risk warning" signal to the ground control terminal, and controls the drone to adjust its flight attitude and return to base to avoid the drone becoming unstable and crashing due to wind.

[0018] Step S5 Automatic Unhooking Monitoring: After the drone arrives at the afforestation site, it slowly descends until the sapling touches the ground. The lifting tension disappears, and the unhooking device automatically opens. The main control chip detects that the pressure sensor array pressure drops sharply from an average of 2.3N to 0.3N, and the tension sensor value drops sharply from 1.2kg to 0.03kg. The drone hovers for 5 seconds and then takes off to return. During the return, the tension value stabilizes at 0.03-0.04kg without any abnormal increase, indicating successful unhooking. The drone returns normally to the lifting point. If the pressure sensor value remains at 1.8N after a sapling touches the ground, the unhooking is considered to have failed. If the pressure sensor array pressure drops sharply from an average of 2.3N to 0.3N after a sapling touches the ground, but the tension sensor value drops to 0.04kg and then rises back to 1.2kg, it is determined that the automatic unhooking device may be entangled by leaves or branches, causing the unhooking to fail. The flight control system controls the drone to hover and issues an alarm. The operator remotely controls the drone to fine-tune its attitude and attempts to unhook again, or the operator troubleshoots the problem on-site.

[0019] It should be understood that the above embodiments are one or more embodiments of the present invention. There are many other embodiments and variations based on the present invention. Any variations and modifications made by those skilled in the art without making pioneering innovations are within the protection scope of the present invention.

Claims

1. An existing automatic unhooking device, characterized in that, The device includes a pair of hooks hinged together, a pair of connecting rods, an elastic tension member, and a top lifting handle. The hooks consist of a lower arc-shaped hook and an upper hook handle. The two hooks are hinged at the connection between the arc-shaped hook and the hook handle. The two connecting rods are hinged together at one end and connected to the top lifting handle, and the other ends are respectively hinged to the hook handles of the hooks. The elastic tension member is connected between the hinge between the hooks and the hinge between the connecting rods. A method for monitoring the safety and quality of seedling lifting based on an automatic unhooking device for drones, characterized by the following steps: S1. Sensor Installation and System Debugging: Arrange the annular flexible pressure sensors symmetrically on the inner clamping surfaces of the automatic unhooking device's double hooks, ensuring that the sensor array completely covers the entire arc-shaped hook surface; connect the tension sensor in series between the load attachment point on the bottom side of the UAV and the hoisting rope connecting the automatic unhooking device; check the communication connections between each sensor and the main control chip and the UAV flight control system to ensure smooth signal transmission. S2. Precise Screening of Seedling Diameter: An automatic unhooking device with a diameter slightly larger than the required trunk diameter is selected. Before transportation, a trunk with the minimum standard diameter is used for calibration. The seedling trunk is placed into the double-hook clamp of the automatic unhooking device. The connecting rods on both sides are held and gently pressed to close the double hooks, initially securing the trunk within them. The drone is activated and applies an initial upward lifting force. This force is transmitted to the double-hook assembly, ensuring full contact between the annular flexible pressure sensor array and the trunk surface, generating pressure. The main control chip collects the pressure value of each pressure sensor in real time, recording the pressure distribution characteristics corresponding to the diameter's uniformity and coverage, and writes this information into the main control chip as a judgment criterion. The uniformity satisfies the following formula: Uniformity = Minimum pressure on one side / Maximum pressure on one side The coverage rate satisfies the following formula: Coverage = Number of pressure sensors / Total number of sensors The closer the uniformity is to 1 and the higher the coverage, the more uniform the contact between the trunk and the double hooks, and the better the trunk diameter matches the space inside the hooks. Before transportation, the main control chip collects data in real time on the uniformity and coverage of the saplings to be hoisted and compares them with preset qualification standards. If both parameters meet the set standards, the trunk diameter is determined to be up to standard, and the main control chip immediately communicates with the UAV flight control system to send a "quality qualified" signal, triggering subsequent transportation instructions. If the parameters do not meet the standards, the trunk diameter is determined to be too small, and the main control chip sends a "quality unqualified" signal. After receiving the signal, the UAV flight control system controls the UAV to descend until the sapling touches the ground. The automatic unhooking device automatically opens, and the operator removes the unqualified sapling, replaces it with a qualified sapling, and then re-hooks and judges the sapling. S3. Overweight warning before drone transport: The flight control system presets a safe load threshold; while determining that the trunk diameter meets the standard, the tension sensor monitors the weight of the sapling in real time and uploads the data to the drone flight control system simultaneously; if the tension value is not greater than the safe load threshold, the flight control system controls the drone to start and transport the sapling to the designated location according to the preset route; if the tension value is greater than the overload threshold, the flight control system controls the drone to stop taking off and descend slowly until the sapling touches the ground, and the automatic unhooking device opens to release the sapling; S4. Drone Aerial Dynamic Risk Control: During drone flight, the tension sensor continuously collects lifting tension data and uploads it to the flight control system. When the wind is too strong, it will exert lateral tension on the seedlings being lifted, causing the tension sensor to abnormally increase the value collected, exceeding the preset fluctuation threshold range. When the tension value is detected to exceed this threshold, it is determined that the current transportation environment is unsafe and not suitable for continued transportation. At this time, the flight control system automatically sends a "risk warning" signal to the ground control terminal and controls the drone to adjust its flight attitude and return to base to avoid the drone from becoming unstable and crashing due to wind. S5. Automatic Unhooking Monitoring: When the drone carrying the sapling arrives at the target afforestation location, it descends slowly until the sapling touches the ground. The lifting tension disappears instantly, and the automatic unhooking device automatically opens, achieving automatic unhooking of the sapling. The main control chip monitors the pressure changes of the ring-shaped flexible pressure sensor array in real time. After unhooking, the sensor loses contact with the trunk, and the pressure value drops sharply. At the same time, the tension value detected by the tension sensor also drops sharply from the value corresponding to the weight of the sapling to close to 0. After the pressure of the pressure sensor array drops sharply and stabilizes in the low value range, and the tension sensor continues to detect that the tension value drops below the preset unhooking threshold, and no abnormal increase in tension value is detected during the subsequent take-off and return of the drone, then the unhooking is determined to be successful, and the flight control system controls the drone to return to the starting point normally. If the pressure of the pressure sensor array does not drop significantly, or if the tension sensor detects that the tension value drops to the threshold and then increases abnormally, then the unhooking is determined to be unsuccessful, an alarm is sent, and an attempt is made to unhook again, or the operator is asked to troubleshoot the fault on-site.

2. The method for monitoring the safety and quality of seedling transport based on an automatic unhooking device for unmanned aerial vehicles (UAVs) according to claim 1, characterized in that, The number of annular flexible pressure sensors mentioned in step S1 shall be no less than three on each side of the arc hook and they shall be symmetrically distributed from left to right.

3. The method for monitoring the safety and quality of seedling transport based on an automatic unhooking device for unmanned aerial vehicles according to claim 1, characterized in that, The diameter of the automatic unhooking device described in step S2 is 15%-25% larger than the maximum required trunk diameter.

4. The method for monitoring the safety and quality of seedling transport based on an automatic unhooking device for unmanned aerial vehicles (UAVs) according to claim 1, characterized in that, In step S2, the trunk is placed in the automatic unhooking device at a height of 2 / 3 from the root.

5. The method for monitoring the safety and quality of seedling lifting based on an automatic unhooking device for unmanned aerial vehicles according to claim 1, characterized in that, The preset fluctuation threshold range mentioned in step S4 is ±10% of the tension when the sapling just leaves the ground.

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