Variable rate fertilization control method and system based on backpack type fertilizer distributor

Abstract

The invention relates to a variable fertilization control method and system based on a backpack type fertilizer distributor, and belongs to the field of agricultural machinery control. The system is composed of a main controller, a speed measurement module, a satellite navigation module, a motor control module and an execution structure. The position information of an operator is determined through satellite navigation, a land parcel is divided into grids, the fertility of the land parcel is analyzed, a discharging model is established in combination with the fertilizer density, the walking speed and the like, intelligent variable fertilization is achieved, the fertilization precision is improved, and fertilizer waste and environmental pollution are avoided. The main controller is connected with all the modules to process data and send instructions, the 4G chip transmits operation information to the cloud platform to achieve remote supervision, and an operator can remotely manage and adjust operation according to the operation information. And the fertilizing device of the execution structure is driven by a motor to discharge. The system provides an automatic mode and a manual mode, is wide in applicability, low in cost and suitable for farmers to use, and has great significance in improving agricultural production efficiency and quality and promoting agricultural sustainable development.

Description

Technical Field

[0001] The invention relates to the field of agricultural machinery control, and in particular to a variable fertilization control method and system based on a backpack fertilizer spreader. Background Art

[0002] Fertilization has always been a very important link in the agricultural field. The correct application of fertilizers directly affects crop yields.

[0003] Since large agricultural machinery is expensive, studies have shown that backpack fertilizer spreaders are the most widely used fertilizer spreading devices. Many existing patents have made many structural improvements to backpack fertilizer spreaders, enabling them to achieve accurate and uniform material delivery, but their functions are relatively simple, mainly relying on manual operation and lacking intelligent control. Operators usually apply fertilizers based on experience, and it is difficult to accurately grasp the amount and timing of fertilizer application. This not only leads to low fertilization accuracy and uneven fertilization, which affects the growth and development of crops, but also may cause waste of fertilizers and increase agricultural production costs. At the same time, traditional backpack fertilizer spreaders cannot consider the impact of operating speed on fertilization effects. In actual operation, changes in operating speed will directly affect the amount of fertilizer spread per unit time. If the amount of fertilizer cannot be adjusted in time according to the operating speed, it may lead to excessive or insufficient fertilization, affecting the yield and quality of crops.

[0004] In summary, traditional fertilization methods and related systems can no longer meet the needs of modern agricultural production. There is an urgent need for a variable fertilization control system based on a backpack fertilizer spreader that can realize intelligent fertilization, consider the operation speed and plot differences, and have remote supervision functions. At the same time, it is low-cost and widely applicable, so as to improve the efficiency and quality of agricultural production, reduce fertilizer waste, and protect the ecological environment. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the deficiencies of the prior art, the present invention aims to provide a variable fertilization control method and system based on a backpack fertilizer spreader, which solves the problems existing in the prior art. The present invention uses a satellite navigation module to accurately determine the location information of the operator, and combines the shape, area and historical fertilization data of the plot to adaptively divide the plot into multiple grids. The soil fertility status of different grids is determined by calculating the degree of complex shape irregularity and analyzing the fertility distribution (such as using the Kriging interpolation method to construct a fertility distribution surface). On this basis, the grid size is determined according to the shape and fertility change threshold, which ensures the accurate grasp of the plot information and lays the foundation for precise fertilization. For example, setting a smaller grid in an area with complex shape and large fertility differences can more carefully identify local fertility changes; while a larger grid is used in a regular and uniform fertility area, while ensuring accuracy and optimizing the use of computing resources. The motor speed can be dynamically calculated according to the actual situation, and then the discharge speed can be accurately controlled. This allows the amount of fertilizer to be adjusted in real time according to the needs of different plots and operating conditions, avoiding uneven fertilization and waste caused by empirical fertilization, improving fertilizer utilization, and reducing the risk of environmental pollution.

[0007] (II) Technical solution

[0008] To achieve the above object, the present invention provides the following technical solution: a variable fertilization control method based on a backpack fertilizer spreader, comprising the following steps:

[0009] Adaptive grid division: obtain the coordinate information of the plot boundary through the satellite navigation module, determine the shape and area of ​​the plot, calculate the index of the irregularity of the plot shape, use the spatial interpolation algorithm to analyze the fertility distribution change of the plot, generate the fertility distribution surface, set the shape irregularity and fertility change thresholds, divide the grid according to the preset direction, and process the edge grid to make it fit the plot boundary;

[0010] Soil fertility calculation: Extract soil fertility, topography, and crop planting history multi-dimensional feature data for each grid and organize them into feature vectors; calculate the grid average fertilizer demand index through clustering algorithms and formulate fertilization strategies;

[0011] Information collection and transmission: The satellite navigation module determines the operator's time information, location information, and speed information, and inputs it to the main controller; the speed measurement module collects the current equipment's discharge speed and inputs it to the main controller;

[0012] Information processing: The main controller receives GPS data from the satellite navigation module and analyzes the information to obtain the corresponding fertilizer demand and integrate the demand with the walking speed and fertilizer density information;

[0013] Discharging speed calculation: Based on the selected fertilizer type, the software combines different fertilizer densities and the walking speed of the operator to establish a discharging model;

[0014] Motor control and discharging: The main controller sends the calculated theoretical speed to the motor control module. The PWM signal generator in the motor control module receives and responds to the command signal from the main controller and converts it into a PWM wave. The motor driver is connected to the PWM signal generator to drive the motor to rotate. The motor converts the received voltage signal into the corresponding speed to control the discharging speed.

[0015] As a preferred technical solution of the present invention, in the adaptive grid division step, using a spatial interpolation algorithm to analyze the distribution change of fertility of a plot includes:

[0016] Data preparation: Collect historical fertilization data within the plot and existing fertility detection point data;

[0017] Construct a covariance matrix: Calculate the covariance between any two data points and construct a covariance matrix;

[0018] Solving weight coefficients: Solving the weight coefficients of each known data point to the estimated fertility value of the unknown location through a system of linear equations;

[0019] Calculate the estimated fertility value: For any unknown location in the plot, multiply the fertility values ​​of the surrounding known data points by the corresponding weight coefficient and sum them up to obtain the estimated fertility value of the unknown location;

[0020] Construct a fertility distribution surface: correspond the calculated fertility estimate matrix to the coordinate system of the plot, and use geographic information system tools to map the fertility estimate of each location to the corresponding spatial position to construct a fertility distribution surface.

[0021] As a preferred technical solution of the present invention, in the soil fertility calculation step, the characteristic vector is [mean nitrogen content, standard deviation of nitrogen content, mean phosphorus content, standard deviation of phosphorus content, mean potassium content, standard deviation of potassium content, average altitude, standard deviation of altitude, average slope, standard deviation of slope, crop type code, planting frequency, average yield, standard deviation of yield].

[0022] As a preferred technical solution of the present invention, in the soil fertility measurement step, the clustering algorithm calculates the grid average fertilizer requirement index including:

[0023] Distance calculation and cluster assignment: For each grid, calculate the distance between its feature vector and each cluster center;

[0024] Cluster center update: After completing a round of grid allocation, recalculate the center of each cluster. For each cluster, average all grid feature vectors belonging to the cluster to obtain a new cluster center feature vector.

[0025] Iteration loop: Repeat the above distance calculation, cluster assignment, and cluster center update steps to form an iterative loop until the set maximum number of iterations is reached.

[0026] As a preferred technical solution of the present invention, the theoretical speed calculation formula of fertilization in the grid in the discharge speed calculation step is: V1 = (F1 / A1)*W*V / K, where V1 represents the theoretical motor speed of grid 1 (r / s), F1 represents the amount of fertilizer required for grid 1 (kg), and A1 represents the area of ​​grid 1 (m 2 ), W represents the width (m), V represents the travel speed (m / s), and K represents the coefficient relationship between the motor speed (r / s) and the discharge amount (kg / s).

[0027] A variable fertilization control system based on a backpack fertilizer spreader comprises a control system and an actuator.

[0028] As a preferred technical solution of the present invention, the control system includes:

[0029] 1. The main controller is the core control unit of the entire system, which coordinates and manages each module. It receives and processes data from the speed measurement module, satellite navigation module, and operation parameters entered by the user through buttons. It calculates based on this information, determines the amount of fertilizer required for the plot and the discharge speed, and sends instructions to the motor control module.

[0030] The main controller includes an LCD screen, buttons, a 4G chip, a main chip and a serial communication unit, among which:

[0031] a. LCD screen: used to display operation information, so that users can intuitively understand the current operating status of the system. The displayed content includes operation mode (such as automatic mode, manual mode, etc.), operation speed (including walking speed and discharge speed, etc.), operation status (operating, paused, fault, etc.) and set parameters (such as fertilizer type, fertilizer spreading amount setting, etc.), providing users with real-time feedback information so that users can understand the status of fertilizer spreading at any time and make adjustments as needed.

[0032] b. Buttons: for users to set operating parameters and realize personalized operation of the system. You can set the acceleration and deceleration of the discharge and adjust the discharge speed of the fertilizer according to actual needs. Set the fertilizer type. Different fertilizers may require different fertilizer spreading amounts and discharge speed control strategies. The system can make corresponding adjustments according to the fertilizer type. The fertilizer spreading amount setting can directly determine the amount of fertilizer to be spread each time to meet the different fertilizer needs of different plots.

[0033] c.4G chip: responsible for sending operation information to the cloud platform to achieve remote supervision and operation management. Use the MQTT protocol to send current operation information, such as operation location, operation speed, walking speed, amount of fertilizer spread, amount of fertilizer required, fertilizer type, etc. to the cloud platform. The cloud platform can store, process and display this information, making it convenient for operators to check the operation status anytime and anywhere. At the same time, the cloud platform can also use the received operation location information to calculate the operation mileage and operation area, providing operators with more comprehensive operation management functions.

[0034] d. Main chip: As the core processing unit of the main controller, it undertakes the important tasks of data reception, processing, storage and transmission. Receive data from each module, including positioning information, time information, longitude and latitude information and speed information from the satellite navigation module, as well as discharge speed information from the speed measurement module and operation parameters input by buttons. Process these data, such as solving various information in the GPS data of the satellite navigation module, and calculating the identification and discharge speed of the plot through a specific algorithm. For example, a large plot is divided into multiple small grids. The main chip determines the grid where the current position is located based on the positioning information, and obtains the amount of fertilizer required for the grid. Store important data for subsequent query and analysis. At the same time, send instructions to the motor control module based on the processing results to control the discharge speed and achieve precise fertilization.

[0035] e. Serial communication unit: plays the role of connection and communication, connecting the main controller with the satellite navigation module and the speed measurement module. Communicate with the satellite navigation module to obtain geographic coordinate information and speed information to ensure that the main controller can accurately grasp the location and operation speed of the operator. Connect with the speed measurement module to process the received speed information and send it to the LCD screen and cloud platform for display, so that users and remote monitoring platforms can understand the current discharge speed and operation progress.

[0036] 2. Speed ​​measurement module: It is mainly used to measure the discharge speed of the fertilization equipment. The Hall sensor cooperates with the magnet installed on the rotating shaft to sense the change of the magnetic field and output different level signals, so as to calculate the current fertilization speed and transmit the information to the main controller so that the main controller can adjust the fertilization operation according to the discharge speed and other factors.

[0037] 3. Satellite navigation module: Determine the location information, time information and speed information of the operator. The GPS receiver uses TTL data to calculate the specific longitude and latitude coordinates every 100 milliseconds to obtain the current location of the operator, and obtains the average speed of the operator through relevant calculations. This information is input into the main controller, which combines the location information with the pre-divided plot grid to determine the amount of fertilizer required for the plot where the operator is located, and at the same time considers factors such as the operating speed to control fertilization. The GPS antenna is used to receive GPS signals to ensure the normal operation of the satellite navigation module.

[0038] 4. Motor control module: including PWM signal generator, motor driver and motor. The motor control module controls the operation of the motor according to the instructions of the main controller. The PWM signal generator receives the command signal of the main controller and converts it into PWM wave. The motor driver drives the motor to rotate according to the PWM wave. The motor converts the received voltage signal into the corresponding speed, thereby realizing the precise control of the fertilizer discharge speed.

[0039] As a preferred technical solution of the present invention, the execution structure includes a fertilizing device, which includes a power supply bin, a power switch installed on the right side of the power supply bin, a built-in battery fixed inside the power supply bin, the built-in battery connected to the first motor through a wire, the first motor connected to the discharge channel through a rotating shaft, the discharge channel connected to the discharge bin through a discharge hose, the discharge bin includes a second motor, the second motor is connected to a turntable, a barrel is installed on the upper part of the power supply bin, and straps are symmetrically fixed on the left and right sides of the barrel. The barrel is used to load solid granular fertilizer. The built-in battery is fixed inside the power supply bin to power all components of the entire system. Under the command of the control system, the first motor drives the fertilizer in the barrel through the discharge channel. The discharge channel connects the barrel and the discharge hose to transport the fertilizer to the discharge bin. The discharge hose plays the role of connecting and transporting fertilizer. The discharge bin includes a second motor and a turntable, and the second motor drives the turntable to evenly spread the incoming fertilizer on the ground with a set width. The strap is used to facilitate the operator to carry the fertilizer spreader on his back for operation.

[0040] As a preferred technical solution of the present invention, the built-in battery is connected to the speed sensor through a wire, the speed sensor is installed on the right side of the discharge channel, and is used in conjunction with a magnet installed on the rotating shaft. The speed sensor is connected to the main chip through a sensor interface, and the main chip calculates the motor speed;

[0041] As a preferred technical solution of the present invention, the built-in battery is connected to the GPS receiver through a wire, the GPS receiver is connected to the GPS antenna through a GPS antenna interface, the GPS receiver is connected to the main chip through a sensor interface, the main chip obtains GPS data, and calculates positioning information, position information, time information, and speed information.

[0042] As a preferred technical solution of the present invention, the built-in battery is connected to the motor drive module through a wire, the motor drive module is connected to the main chip through a motor drive interface, the main chip calculates the theoretical speed through the acquired position information, speed information, and plot information, and sends it to the motor drive module, and the motor drive module executes the corresponding command.

[0043] As a preferred technical solution of the present invention, the built-in battery is connected to the main controller via a power interface to provide power to the main controller.

[0044] (III) Beneficial effects

[0045] The purpose of the present invention is to provide a variable fertilization control method and system based on a backpack fertilizer spreader, which has the following beneficial effects: in terms of fertilization accuracy, satellite navigation is used to determine the operation position, combined with the grid division of the plot and fertility analysis, and a discharging model is established based on multiple factors such as fertilizer type and walking speed. The amount of fertilizer can be accurately controlled according to the actual needs of different plots, effectively avoiding the problem of uneven fertilization caused by traditional fertilization based on experience, greatly improving the fertilizer utilization rate, reducing fertilizer waste, and reducing environmental pollution caused by fertilizer loss to soil, water and atmosphere, providing a more scientific nutrient supply for crop growth, and promoting crop yield and quality improvement. In terms of remote supervision, the 4G chip of the main controller transmits the operation information to the cloud platform, and the operator can remotely view the operation position, speed, fertilizer amount and other information in real time. The operation mileage and area calculated by the cloud platform can also be used to optimize the operation process and adjust the fertilization strategy. The management personnel can also centrally supervise multiple devices, which greatly improves the efficiency and transparency of operation management. The backpack fertilizer spreader's design and automatic and manual dual-mode operation make it widely applicable. It can be used in farmlands of different sizes and in various terrain conditions to meet the habits and scenario requirements of different operators, and effectively promote agricultural fertilization to move towards precision, intelligence, efficiency and sustainability. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of the present invention.

[0047] Figure 2 It is a schematic diagram of the front cross-sectional structure of the material barrel of the present invention.

[0048] Figure 3 It is a schematic diagram of the rear view structure of the material barrel of the present invention.

[0049] Figure 4 Schematic diagram of the main controller of the present invention.

[0050] Figure 5 It is a system schematic diagram of the present invention.

[0051] Figure 6 It is a software function flow chart of the present invention.

[0052] In the figure: 1-barrel, 2-shoulder, 3-shaft, 4-power compartment, 5-first motor, 6-speed sensor, 7-built-in battery, 8-motor drive module, 9-GPS receiver, 10-power switch, 11-discharging channel, 12-discharging hose, 13-handle, 14-discharging bin, 15-second motor, 16-turntable, 17-GPS antenna, 18-sensor interface, 19-motor drive interface, 20-power interface, 21-GPS antenna interface, 22-button, 23-main controller, 24-LCD screen. DETAILED DESCRIPTION

[0053] The following will be combined with the attached examples of the present invention Figure 1-Figure 6 A clear and complete description of the technical solutions in the embodiments of the present invention is given. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0054] The present invention provides a technical solution:

[0055] A variable fertilization control method based on a backpack fertilizer spreader comprises the following steps:

[0056] 1. Adaptive grid division:

[0057] 1. Plot data collection and preprocessing:

[0058] 1.1 Start the satellite navigation module. Its GPS receiver uses TTL data to accurately calculate the longitude and latitude coordinates of each vertex of the land boundary. It records the coordinates of multiple boundary points in a clockwise or counterclockwise direction, such as point A (longitude 110.12°, latitude 30.56°), point B (longitude 110.15°, latitude 30.53°), etc. The approximate shape of the land is determined by these coordinate points, and the area of ​​the land is calculated using geometric calculation methods.

[0059] 1.2 Historical fertilization data processing: Read the past fertilization data records of the plot from the system storage unit. These data include the amount of fertilizer applied at different times and locations in the plot, the type of fertilizer applied, and the corresponding crop yield information. Perform a comprehensive check on these data. If the amount of fertilizer applied in a data record is found to be significantly beyond the normal range (such as more than 5 times the average amount of fertilizer applied to the same type of plot) and there is no reasonable explanation, mark the data as abnormal data. For abnormal data, further verify its authenticity. If it is determined to be erroneous data, use data correction or deletion to ensure the accuracy and reliability of the data and provide an effective basis for subsequent analysis.

[0060] 2. Land shape and fertility analysis:

[0061] 2.1 Calculation of shape irregularity: Based on the obtained coordinate points of the plot boundary, the geometric algorithm of polygon analysis is used to calculate the irregularity index of the plot shape.

[0062] This includes calculating the concavity of the boundary and analyzing the changes in the angles between adjacent boundary segments. If there are many alternating acute and obtuse angles, it means that the shape of the plot is relatively complex. Combining these factors, a numerical index representing the degree of irregularity of the shape is obtained through weighted calculation. The value range is between 0 and 1, where 0 means a very regular shape (such as a rectangle) and 1 means an extremely complex shape.

[0063] 2.2 Fertilizer distribution analysis: Using historical fertilization data, a spatial interpolation algorithm (Kriging interpolation method) is used to analyze the distribution changes of fertility within the plot. The specific steps include:

[0064] 2.2.1 Data preparation: First, collect historical fertilization data within the plot and existing fertility detection point data. These data contain the location coordinates of each data point (such as longitude and latitude) and the corresponding fertility value, such as the content of nutrients such as nitrogen, phosphorus, and potassium.

[0065] 2.2.2 Determine the variogram model: According to the characteristics of the data and the actual situation of the plot, select the Gaussian model to describe the spatial correlation of the fertility data. Through the analysis and fitting of the data, determine the most suitable variogram and its parameters to accurately describe the spatial variation of the fertility data.

[0066] 2.2.3 Constructing the covariance matrix: Based on the Gaussian model and the location information of the data points, the covariance between any two data points is calculated to construct the covariance matrix. The covariance matrix reflects the degree of spatial correlation between the data points.

[0067] 2.2.4 Solve the weight coefficient: Based on the covariance matrix and the fertility values ​​of the known data points, the weight coefficient of each known data point on the fertility estimate of the unknown location is solved through a set of linear equations.

[0068] 2.2.5 Calculate the estimated fertility value: For any unknown location in the plot, multiply the fertility value of the surrounding known data points by the corresponding weight coefficient and sum them up to get the estimated fertility value of the unknown location. By performing such calculations for all unknown locations in the plot, the fertility estimate matrix of the entire plot can be obtained.

[0069] 2.2.6 Constructing a fertility distribution surface: The calculated fertility estimate matrix is ​​matched to the coordinate system of the plot, and the fertility estimate of each location is mapped to the corresponding spatial location using the Geographic Information System (GIS) tool, thereby constructing a continuous fertility distribution surface. This surface intuitively shows the distribution changes of fertility within the plot, including high and low fertility areas, gradient changes and other information, providing an important basis for subsequent grid division and fertilization strategy formulation.

[0070] For example, for a certain coordinate point (longitude 110.13°, latitude 30.54°), the fertility index values ​​of nitrogen content 15 mg / kg and phosphorus content 8 mg / kg are obtained through interpolation calculation. This allows us to intuitively understand the fertility trend in different areas of the plot and the gradient distribution of fertility.

[0071] 3. Grid size determination:

[0072] 3.1 Threshold setting: Based on a large amount of experimental data and actual experience, set the thresholds for shape irregularity and fertility change. For example, set the shape irregularity threshold to 0.5. If the calculated land shape irregularity index exceeds 0.5, the land is considered to have a complex shape. Set the fertility change threshold, such as the fertility standard deviation threshold to 10. If the standard deviation of the fertility data within the land is greater than 10, it means that the fertility change is large.

[0073] 3.2 Size determination and resource consideration: Compare the calculated land irregularity index and fertility change with the set threshold. If the land irregularity is high and the fertility change is large (both exceed the threshold), it is determined to be a complex area, and a smaller grid size is initially set, such as a square grid with a side length of 2-5 meters. On the contrary, if the land is relatively regular and the fertility is relatively uniform (both are below the threshold), a larger grid size is used, such as a square grid with a side length of 10-20 meters.

[0074] 4 grid division:

[0075] 4.1 Starting point and direction selection: Determine to start the grid division from a corner point of the plot, select the upper left corner as the starting point, and determine the division direction at the same time, such as dividing from left to right or from top to bottom.

[0076] 4.2 Conventional grid division: Based on the determined grid size, the grid is divided in sequence along the preset direction starting from the starting point. For example, if the determined grid side length is 5 meters, in the horizontal direction, a grid boundary point is determined every 5 meters from the starting point; in the vertical direction, boundary points are also determined every 5 meters, thus forming square grids. During the division process, the number of each grid and the corresponding boundary coordinate range are recorded so that each grid can be accurately identified and located later.

[0077] 4.3 Edge grid processing: For the grid at the edge of the plot, due to the irregularity of the plot boundary, the grid may exceed the plot range or the grid may not completely cover the edge of the plot. For the part that exceeds the plot range, the excess part is removed by clipping so that the grid is completely inside the plot. For example, if the upper right corner of a grid exceeds the plot boundary, the clipping line is determined according to the plot boundary curve, and the excess part is removed. For the situation that the edge of the plot cannot be completely covered, the grid shape is merged or adjusted according to the edge shape and the remaining space size. For example, multiple small edge grids can be merged into a larger grid with a shape that fits the edge better; or the boundary of an edge grid can be adjusted to coincide with the plot boundary. By changing the shape of the grid (such as changing it to a trapezoid or triangle) to better adapt to the irregularity of the plot edge, it is ensured that each plot area can be reasonably divided into the corresponding grid, and the accuracy and effectiveness of the grid division are improved.

[0078] 2. Soil fertility calculation

[0079] 1. Feature extraction and data preparation:

[0080] 1.1 Extraction of soil fertility characteristics: For each grid, obtain the content information of major nutrient elements such as nitrogen, phosphorus, and potassium from the soil fertility database or previous test data. Calculate the mean and standard deviation of these nutrient contents to reflect the average level and degree of variation of soil fertility within the grid.

[0081] 1.2 Extraction of topographic features: Use topographic survey data or satellite remote sensing data to obtain topographic information within the grid. Calculate the average altitude and standard deviation of the altitude within the grid to understand the undulation of the terrain. For example, if the average altitude in a grid is 50 meters and the standard deviation is 10 meters, it means that the terrain in the area has certain undulations. In addition, calculate the slope information of the grid, and determine the average slope and slope variation range by analyzing the ratio of the height difference and horizontal distance at different positions in the grid. For example, the average slope is 5° and the maximum slope is 10°.

[0082] 1.3 Crop planting history feature extraction: query the crop planting database, obtain the information of the types of crops planted in the grid in the past, and encode different crop types, for example, wheat is encoded as 1, corn is encoded as 2, etc. Count the frequency of planting each crop in the past, such as planting wheat 3 times and corn 2 times in the past 5 years. At the same time, obtain the crop yield data of each planting, calculate the average yield and the standard deviation of the yield, so as to evaluate the production capacity of the grid under different crop planting conditions. These data related to crop planting history together constitute another part of the feature vector.

[0083] 1.4 Feature vector arrangement: Combine the multi-dimensional feature data such as soil fertility, topography, crop planting history, etc. extracted above in a certain order to form the feature vector corresponding to each grid. The feature vector of a grid is [mean nitrogen content, standard deviation of nitrogen content, mean phosphorus content, standard deviation of phosphorus content, mean potassium content, standard deviation of potassium content, mean altitude, standard deviation of altitude, mean slope, standard deviation of slope, crop type code, planting frequency, average yield, standard deviation of yield].

[0084] 2. Clustering algorithm selection and initialization:

[0085] Clustering algorithm selection: K-Means clustering algorithm is relatively simple and efficient when processing large-scale data. This algorithm is selected to cluster the grid.

[0086] Estimation and setting of the number of clusters K: The number of clusters K is estimated based on the historical planting conditions, topography, and approximate distribution of soil fertility of the plot. For example, if the plot has been mainly planted with three different types of crops in history, and the topography and fertility have certain zoning characteristics, K can be initially set to 3-5. At the same time, some empirical rules can be referred to, such as the elbow rule. By calculating the clustering error index (such as the intra-cluster sum of squares) under different K values, a relationship curve between the K value and the error index is plotted. The K value corresponding to the elbow position of the curve is usually a more appropriate choice of cluster number. However, the final K value still needs to be adjusted and determined based on actual conditions and expert experience.

[0087] Initial cluster center selection: After determining the number of clusters K, randomly select K grids from all grids as initial cluster centers. The feature vectors of these initial cluster centers will be used as the initial representative points of each cluster, and subsequent grids will be clustered according to the distance from these centers. For example, the first randomly selected cluster center grid may have a feature vector [10mg / kg, 2mg / kg, 8mg / kg, 1mg / kg, 15mg / kg, 2mg / kg, 40m, 5m, 3°, 2°, 1, 0.6, 400kg / mu, 50kg / mu], which will represent the central characteristics of a cluster in the initial stage.

[0088] 3. Clustering iterative calculation:

[0089] 3.1 Distance calculation and cluster assignment: For each grid, calculate the distance between its feature vector and each cluster center. Use the Euclidean distance formula for calculation:

[0090]

[0091] Where X i is the feature vector of the i-th grid, C jis the eigenvector of the jth cluster center, and n is the dimension of the eigenvector. Calculate the distance between them. Assign each grid to the cluster with the closest distance. After all grids are assigned, a preliminary clustering result is formed.

[0092] 3.2 Cluster center update: After completing a round of grid allocation, recalculate the center of each cluster. For each cluster, average the feature vectors of all grids belonging to the cluster to obtain a new cluster center feature vector. For example, if there are 10 grids in a cluster, add the mean nitrogen content of these 10 grids and divide by 10 to obtain the new cluster center nitrogen content mean. Similarly, update the mean of all feature dimensions to form a new cluster center.

[0093] 3.3 Iteration loop: Repeat the above distance calculation, cluster assignment, and cluster center update steps to form an iterative loop. Each iteration will optimize the clustering results until the stop condition is met. The stop condition is to set the maximum number of iterations. When the number of iterations reaches the maximum number of iterations, the iteration process is stopped regardless of whether the cluster center has changed.

[0094] 4. Fertilization strategy formulation:

[0095] 4.1 Calculation of statistical indicators within clusters: After clustering is completed, for each cluster, calculate the average fertilizer demand, average soil fertility and other statistical indicators of its internal grids. For example, calculate the mean nitrogen content and phosphorus content of all grids in a cluster as the average soil fertility index of the cluster; based on historical fertilization data and crop yield data, analyze and calculate the average amount of fertilizer required per unit area in the cluster, such as the grams of nitrogen, phosphorus and potassium fertilizers required per square meter, etc. These data will serve as an important basis for formulating fertilization strategies.

[0096] 4.2 Determination of preliminary fertilization strategy: According to statistical indicators such as the average soil fertility and average fertilizer demand of the cluster, formulate a preliminary fertilization strategy for each cluster. If the average soil fertility of a cluster is low and the average fertilizer demand is high, then the amount of fertilizer applied can be appropriately increased during fertilization, and the fertilizer formula can be adjusted according to the main element type lacking in soil fertility, and the proportion of fertilizers of corresponding elements can be increased. For example, for clusters with low nitrogen content, increase the amount of nitrogen fertilizer applied, and reasonably match phosphorus and potassium fertilizers to determine a preliminary fertilization amount range and fertilizer formula combination.

[0097] 4.3 Fine-tuning of special grids: For individual special grids within a cluster, further analyze their special conditions and fine-tune the fertilization strategy. For example, if a grid belongs to a cluster, but its soil fertility is particularly low (such as nitrogen content is far below the average level of the cluster) or its terrain is special (such as being in a low-lying area prone to water accumulation, which may lead to fertilizer loss), then based on the initial fertilization strategy, the amount of fertilizer applied to the grid is appropriately increased or the fertilizer formula is adjusted to make it more suitable for the special conditions of the grid, so as to ensure that each grid can be fertilized accurately and reasonably, and improve the fertilization effect and crop yield.

[0098] 3. Information collection and transmission: The satellite navigation module determines the operator's time information, location information, and speed information, and inputs them into the main controller; the speed measurement module collects the current equipment's discharge speed and inputs it into the main controller;

[0099] 4. Information processing: The serial communication unit of the main controller receives the GPS data from the satellite navigation module and parses the relevant information, obtains the corresponding fertilizer demand and integrates the demand with the walking speed and fertilizer density information;

[0100] The specific steps include:

[0101] 1. GPS data reception and preliminary analysis: The serial communication unit in the main controller receives GPS data from the satellite navigation module. It performs preliminary analysis on the received GPS data and extracts the original positioning information, time information, longitude and latitude information, speed information, etc.

[0102] 2. Determine fertilizer demand: Obtain the amount of fertilizer required for the current grid based on the information in the soil fertilizer measurement.

[0103] 3. Comprehensive processing combined with other information: The fertilizer demand information of the current grid is combined with the walking speed information of the operator analyzed from the GPS data, and the fertilizer density determined according to the fertilizer type in the automatic mode.

[0104] 5. Calculation of discharging speed: Based on the selected fertilizer type, the software combines different fertilizer densities and the walking speed of the operator to establish a discharging model, including the following steps:

[0105] 1. Determine the characteristic parameters of fertilizer: According to the type of fertilizer selected by the operator, query the density and other characteristic parameters of the fertilizer pre-stored in the system. The density of different fertilizer types may vary greatly, which will directly affect the calculation of the output.

[0106] 2. Obtain walking speed information: Extract the walking speed of the operator from the information transmitted from the satellite navigation module to the main controller. The walking speed is a dynamically changing value, and the system needs to obtain it in real time to ensure the accuracy of the discharge speed.

[0107] 3. Establish a mathematical model: Consider the fertilizer characteristic parameters and travel speed comprehensively to build a discharging model. Calculate in grid units and first determine the relevant parameters of each small grid, such as grid area, required fertilizer amount, etc.

[0108] For a specific small grid, the theoretical speed calculation formula is:

[0109] V1=(F1 / A1)*W*V / K

[0110] Where V1 represents the theoretical motor speed of grid 1 (r / s), F1 represents the amount of fertilizer required for grid 1 (kg), and A1 represents the area of ​​grid 1 (m 2 ), W represents the width (m), V represents the travel speed (m / s), and K represents the coefficient relationship between the motor speed (r / s) and the discharge amount (kg / s).

[0111] 4. Calculate the discharging speed: Substitute the specific parameter values ​​into the calculation formula of the discharging model, perform mathematical operations, and obtain the theoretical motor speed. Determine the discharging speed based on the corresponding relationship between the motor speed and the discharging speed. This speed will serve as an important basis for controlling the operation of the motor to achieve precise fertilization.

[0112] 6. Motor control and discharging:

[0113] 1. The main controller sends instructions: The main controller determines the motor speed required under the current operating state based on the theoretical speed calculated in the previous steps to achieve accurate discharging.

[0114] The main controller sends instructions containing theoretical speed information to the motor control module to ensure that the motor can run at the expected speed.

[0115] 2. The role of the PWM signal generator: The PWM signal generator in the motor control module receives the command signal from the main controller. It processes the command signal and converts it into a PWM wave with a specific duty cycle. The duty cycle of the PWM wave determines the average voltage of the motor, thereby controlling the speed of the motor. By adjusting the duty cycle of the PWM wave, the motor speed can be accurately controlled to make it as close to the theoretical speed as possible.

[0116] 3. Function of the motor driver: The motor driver is connected to the PWM signal generator and receives the PWM wave signal.

[0117] The motor driver adjusts and amplifies the input power supply voltage according to the signal characteristics of the PWM wave to provide the motor with the appropriate drive voltage and current. The motor driver ensures that the motor can operate stably and reliably, and can quickly respond to the instructions of the PWM signal generator to achieve changes in the motor speed.

[0118] 4. Motor operation and discharge control: The motor is connected to the motor driver and receives the voltage signal from the motor driver. The motor converts the received voltage signal into the corresponding speed and adjusts its own rotation speed according to the command. The rotation of the motor drives the discharge device to work and control the discharge speed. For example, in a backpack fertilizer spreader, the motor may drive the fertilizer conveying device through the transmission mechanism so that the fertilizer is discharged from the discharge port at a specific speed. By accurately controlling the motor speed, the discharge speed can be accurately adjusted to ensure that the fertilizer is spread in accordance with the needs of the current operation area and improve the accuracy and efficiency of fertilization.

[0119] 7. Information transmission and remote supervision:

[0120] 1. Information collection and preparation: Each module in the main controller continuously collects key information during the operation process. This includes the operation location information obtained through the satellite navigation module, which is accurate to the specific longitude and latitude coordinates; the operation speed and walking speed obtained from the speed measurement module and the satellite navigation module; the amount of fertilizer spread according to the statistics of the motor control and discharging process; the required amount of fertilizer determined from the information processing step; and the type of fertilizer set by the operator in the system.

[0121] 2.4G chip information transmission: The 4G chip in the main controller plays a key role, using the MQTT (Message Queue Telemetry Transmission) protocol to send the collected operation information to the cloud platform. The MQTT protocol is a lightweight message transmission protocol suitable for resource-constrained devices and unstable network environments, and can ensure efficient and reliable information transmission. The operation information sent includes the operation location, operation speed, walking speed, amount of fertilizer spread, amount of fertilizer required and fertilizer type, etc. This information fully reflects the real-time status and key parameters of the operation.

[0122] 3. Receiving and processing on the cloud platform: After receiving the operation information sent by the main controller, the cloud platform stores and processes the information. First, the operation information is displayed to facilitate the operator and relevant management personnel to check the progress of the operation at any time. Then, further calculations are performed using the received operation location information. By analyzing the operation location at different time points, the operation mileage can be calculated, that is, the total distance traveled by the operator during the operation. At the same time, based on information such as the operation location and operation width, the operation area can be calculated to understand the scope of land covered by the operation.

[0123] 4. Remote supervision and decision support: Operators can access the cloud platform through the Internet to remotely supervise the operation process. No matter where they are, they can keep abreast of the status and progress of the operation. The operation information and calculation results provided by the cloud platform provide decision support for operators. For example, based on the operation area and the amount of fertilizer spread, it can be determined whether the fertilization strategy needs to be adjusted; based on the operation speed and walking speed, the operation process can be optimized to improve work efficiency. Managers can also centrally supervise the operation of multiple devices through the cloud platform to achieve reasonable allocation of resources and unified management of operations.

[0124] A variable fertilization control system based on a backpack fertilizer spreader comprises a control system and an actuator.

[0125] The control system includes:

[0126] 1. The main controller is the core control unit of the entire system, which coordinates and manages each module. It receives and processes data from the speed measurement module, satellite navigation module, and operation parameters entered by the user through buttons. It calculates based on this information, determines the amount of fertilizer required for the plot and the discharge speed, and sends instructions to the motor control module.

[0127] The main controller includes an LCD screen, buttons, a 4G chip, a main chip and a serial communication unit, among which:

[0128] a. LCD screen: used to display operation information, so that users can intuitively understand the current operating status of the system. The displayed content includes operation mode (such as automatic mode, manual mode, etc.), operation speed (including walking speed and discharge speed, etc.), operation status (operating, paused, fault, etc.) and set parameters (such as fertilizer type, fertilizer spreading amount setting, etc.), providing users with real-time feedback information so that users can understand the status of fertilizer spreading at any time and make adjustments as needed.

[0129] b. Buttons: for users to set operating parameters and realize personalized operation of the system. You can set the acceleration and deceleration of the discharge and adjust the discharge speed of the fertilizer according to actual needs. Set the fertilizer type. Different fertilizers may require different fertilizer spreading amounts and discharge speed control strategies. The system can make corresponding adjustments according to the fertilizer type. The fertilizer spreading amount setting can directly determine the amount of fertilizer to be spread each time to meet the different fertilizer needs of different plots.

[0130] c.4G chip: responsible for sending operation information to the cloud platform to achieve remote supervision and operation management. Use the MQTT protocol to send current operation information, such as operation location, operation speed, walking speed, amount of fertilizer spread, amount of fertilizer required, fertilizer type, etc. to the cloud platform. The cloud platform can store, process and display this information, making it convenient for operators to check the operation status anytime and anywhere. At the same time, the cloud platform can also use the received operation location information to calculate the operation mileage and operation area, providing operators with more comprehensive operation management functions.

[0131] d. Main chip: As the core processing unit of the main controller, it undertakes the important tasks of data reception, processing, storage and transmission. Receive data from each module, including positioning information, time information, longitude and latitude information and speed information from the satellite navigation module, as well as discharge speed information from the speed measurement module and operation parameters input by buttons. Process these data, such as solving various information in the GPS data of the satellite navigation module, and calculating the identification and discharge speed of the plot through a specific algorithm. For example, a large plot is divided into multiple small grids. The main chip determines the grid where the current position is located based on the positioning information, and obtains the amount of fertilizer required for the grid. Store important data for subsequent query and analysis. At the same time, send instructions to the motor control module based on the processing results to control the discharge speed and achieve precise fertilization.

[0132] e. Serial communication unit: plays the role of connection and communication, connecting the main controller with the satellite navigation module and the speed measurement module. Communicate with the satellite navigation module to obtain geographic coordinate information and speed information to ensure that the main controller can accurately grasp the location and operation speed of the operator. Connect with the speed measurement module to process the received speed information and send it to the LCD screen and cloud platform for display, so that users and remote monitoring platforms can understand the current discharge speed and operation progress.

[0133] 2. Speed ​​measurement module: It is mainly used to measure the discharge speed of the fertilization equipment. The Hall sensor cooperates with the magnet installed on the rotating shaft to sense the change of the magnetic field and output different level signals, so as to calculate the current fertilization speed and transmit the information to the main controller so that the main controller can adjust the fertilization operation according to the discharge speed and other factors.

[0134] 3. Satellite navigation module: Determine the location information, time information and speed information of the operator. The GPS receiver uses TTL data to calculate the specific longitude and latitude coordinates every 100 milliseconds to obtain the current location of the operator, and obtains the average speed of the operator through relevant calculations. This information is input into the main controller, which combines the location information with the pre-divided plot grid to determine the amount of fertilizer required for the plot where the operator is located, and at the same time considers factors such as the operating speed to control fertilization. The GPS antenna is used to receive GPS signals to ensure the normal operation of the satellite navigation module.

[0135] 4. Motor control module: including PWM signal generator, motor driver and motor. The motor control module controls the operation of the motor according to the instructions of the main controller. The PWM signal generator receives the command signal of the main controller and converts it into PWM wave. The motor driver drives the motor to rotate according to the PWM wave. The motor converts the received voltage signal into the corresponding speed, thereby realizing the precise control of the fertilizer discharge speed.

[0136] The execution structure includes a fertilizing device, which includes a power supply bin, a power switch installed on the right side of the power supply bin, a built-in battery fixed inside the power supply bin, the built-in battery connected to the first motor through a wire, the first motor connected to the discharge channel through a rotating shaft, the discharge channel connected to the discharge bin through a discharge hose, the discharge bin includes a second motor, the second motor is connected to a turntable, a material barrel is installed on the upper part of the power supply bin, and shoulder straps are symmetrically fixed on the left and right sides of the material barrel. The material barrel is used to load solid granular fertilizer. The built-in battery is fixed inside the power supply bin to power various components of the entire system. Under the command of the control system, the first motor drives the fertilizer in the material barrel to pass through the discharge channel. The discharge channel connects the material barrel and the discharge hose to transport the fertilizer to the discharge bin. The discharge hose plays the role of connecting and transporting the fertilizer. The discharge bin includes a second motor and a turntable, and the second motor drives the turntable to evenly spread the incoming fertilizer on the ground with a set width. The shoulder strap is used to facilitate the operator to carry the fertilizer spreader on his back for operation.

[0137] The built-in battery is connected to the speed sensor through a wire. The speed sensor is installed on the right side of the discharge channel and is used in conjunction with a magnet installed on the rotating shaft. The speed sensor is connected to the main chip through the sensor interface, and the main chip calculates the motor speed.

[0138] The built-in battery is connected to the GPS receiver through a wire, the GPS receiver is connected to the GPS antenna through a GPS antenna interface, the GPS receiver is connected to the main chip through a sensor interface, the main chip obtains GPS data, and calculates positioning information, position information, time information, and speed information.

[0139] The built-in battery is connected to the motor drive module through a wire, and the motor drive module is connected to the main chip through a motor drive interface. The main chip calculates the theoretical rotation speed through the acquired position information, speed information, and plot information, and sends it to the motor drive module, and the motor drive module executes the corresponding command.

[0140] The built-in battery is connected to the main controller through the power interface to provide power for the main controller.

[0141] The workflow of this embodiment is:

[0142] 1. Working principle of automatic mode

[0143] 1. Plot information processing: Start the satellite navigation module, accurately obtain the longitude and latitude coordinate information of the plot boundary vertices, calculate the plot shape and area, and read the historical fertilization data for abnormal data processing and sorting. Analyze the irregularity of the shape based on the plot boundary coordinates, and use the Kriging interpolation method to analyze the fertility distribution using historical fertilization data and fertility detection point data, construct a fertility distribution surface, determine the grid size based on the shape and fertility conditions, and complete the grid division, including starting point selection, conventional division and edge processing, and extract multi-dimensional feature data for each grid to form a feature vector. Select the K-Means clustering algorithm, estimate and set the number of clusters K, randomly select K grids as the initial clustering centers, and complete the relevant preparations for soil fertility measurement.

[0144] 2. Start the fertilization operation: load the material barrel with solid granular fertilizer, the operator carries the fertilizer spreader on his back with a strap, and turns on the power switch on the right. At this time, the main controller starts and the GPS module starts working. If the LCD screen on the main controller displays the current walking speed of the operator, it means that the GPS module has successfully positioned.

[0145] 3. Information collection and processing: The satellite navigation module collects the operator's time information, location information and speed information through the GPS receiver and GPS antenna, and inputs this information into the main controller. The serial communication unit in the main controller receives the GPS data from the satellite navigation module and solves the positioning information, time information, longitude and latitude information and speed information. Divide a large plot of land into multiple small grids, draw a ray from the positioning point in any direction, calculate the number of intersections between the ray and each side of the polygon, determine the current grid, and then obtain the amount of fertilizer required for the grid. At the same time, combine the fertilizer density and other information determined by the fertilizer type in the automatic mode for comprehensive arrangement.

[0146] 4. Calculation of discharge speed: According to the selected fertilizer type, the software combines different fertilizer densities and the walking speed of the operator to establish a discharge model. For example, when the operator is in the first small grid, the theoretical speed of grid 1 is calculated as follows: V1 = (F1 / A1) WV / K, where V1 represents the theoretical motor speed of grid 1, F1 represents the amount of fertilizer required for grid 1, A1 represents the area of ​​grid 1, W represents the width, V represents the walking speed, and K represents the coefficient relationship between the motor speed (r / s) and the discharge amount (kg / s).

[0147] 5. Motor control and discharging: The main controller sends the calculated theoretical speed command to the motor control module. The PWM signal generator in the motor control module receives and responds to the command signal from the main controller and converts it into a PWM wave. The motor driver is connected to the PWM signal generator to drive the motor to rotate. The motor converts the received voltage signal into the corresponding speed to control the discharging speed. Driven by the first motor, the fertilizer in the barrel passes through the discharging channel, which is connected to the feeding hose, and the fertilizer enters the discharging bin along the feeding hose. The discharging bin is equipped with a turntable, which is driven by the second motor to evenly spread the incoming fertilizer on the ground with a set width.

[0148] 6. Information transmission and remote supervision: The 4G chip in the main controller uses MQTT to send the current operation information including operation location, operation speed, walking speed, amount of fertilizer spread, amount of fertilizer required, and fertilizer type to the cloud platform. The cloud platform displays the operation information and uses the received operation location information to calculate the operation mileage and operation area, making it convenient for operators to achieve remote operation management.

[0149] 2. Working Principle of Manual Mode

[0150] 1. System startup and preparation: Same as automatic mode, turn on the power switch, start the main controller, and wait for the operator to operate.

[0151] 2. Parameter setting and operation: The operator sets the operating parameters through the buttons on the main controller, and can perform operations such as discharge acceleration and deceleration, fertilizer type setting, and fertilizer spreading amount setting. In manual mode, the system does not automatically calculate the discharge speed based on the plot information and walking speed, but is completely manually adjusted by the operator according to the actual situation.

[0152] 3. Motor control and discharging: When the operator presses the button to accelerate or decelerate the discharging, the main controller sends the corresponding command to the motor control module. The motor control module adjusts the PWM wave duty cycle output by the PWM signal generator according to the command, and then changes the voltage and current provided to the motor by the motor driver, so that the motor speed changes and the discharging speed is controlled. Driven by the motor, the fertilizer enters the discharging bin through the discharging channel and the feeding hose, and is evenly spread on the ground by the turntable.

[0153] 4. Information display and feedback: The LCD screen of the main controller displays the operation information, including the operation mode (manual mode), operation speed, operation status, set parameters, etc. The operator can understand the current working status of the fertilizer spreader based on the information on the screen so as to adjust the operation in time.

[0154] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A variable fertilization control method based on a backpack fertilizer spreader, characterized in that: The following steps are involved: Adaptive grid division: obtain the coordinate information of the plot boundary through the satellite navigation module, determine the shape and area of ​​the plot, calculate the index of the irregularity of the plot shape, use the spatial interpolation algorithm to analyze the fertility distribution change of the plot, generate the fertility distribution surface, set the shape irregularity and fertility change thresholds, divide the grid according to the preset direction, and process the edge grid to make it fit the plot boundary; Soil fertility calculation: Extract soil fertility, topography, and crop planting history multi-dimensional feature data for each grid and organize them into feature vectors; calculate the grid average fertilizer demand index through clustering algorithms and formulate fertilization strategies; Information collection and transmission: The satellite navigation module determines the operator's time information, location information, and speed information, and inputs it to the main controller; the speed measurement module collects the current equipment's discharge speed and inputs it to the main controller; Information processing: The main controller receives GPS data from the satellite navigation module and analyzes the information to obtain the corresponding fertilizer demand and integrate the demand with the walking speed and fertilizer density information; Discharging speed calculation: Based on the selected fertilizer type, the software combines different fertilizer densities and the walking speed of the operator to establish a discharging model; Motor control and discharging: The main controller sends the calculated theoretical speed to the motor control module. The PWM signal generator in the motor control module receives and responds to the command signal from the main controller and converts it into a PWM wave. The motor driver is connected to the PWM signal generator to drive the motor to rotate. The motor converts the received voltage signal into the corresponding speed to control the discharging speed.

2. The variable fertilization control method based on a backpack fertilizer spreader according to claim 1, characterized in that: In the adaptive grid division step, using a spatial interpolation algorithm to analyze the distribution change of fertility of the plot includes: Data preparation: Collect historical fertilization data within the plot and existing fertility detection point data; Construct a covariance matrix: Calculate the covariance between any two data points and construct a covariance matrix; Solving weight coefficients: Solving the weight coefficients of each known data point to the estimated fertility value of the unknown location through a set of linear equations; Calculate the estimated fertility value: For any unknown location in the plot, multiply the fertility values ​​of the surrounding known data points by the corresponding weight coefficient and sum them up to obtain the estimated fertility value of the unknown location; Construct a fertility distribution surface: correspond the calculated fertility estimate matrix to the coordinate system of the plot, and use geographic information system tools to map the fertility estimate of each location to the corresponding spatial position to construct a fertility distribution surface.

3. The variable fertilization control method based on a backpack fertilizer spreader according to claim 1, characterized in that: In the soil fertility calculation step, the characteristic vector is [mean nitrogen content, standard deviation of nitrogen content, mean phosphorus content, standard deviation of phosphorus content, mean potassium content, standard deviation of potassium content, average altitude, standard deviation of altitude, average slope, standard deviation of slope, crop type code, planting frequency, average yield, standard deviation of yield].

4. The variable fertilization control method based on a backpack fertilizer spreader according to claim 1, characterized in that: In the soil fertility calculation step, the clustering algorithm calculates the grid average fertilizer requirement index including: Distance calculation and cluster assignment: For each grid, calculate the distance between its feature vector and each cluster center; Cluster center update: After completing a round of grid allocation, recalculate the center of each cluster. For each cluster, average all grid feature vectors belonging to the cluster to obtain a new cluster center feature vector. Iteration loop: Repeat the above distance calculation, cluster assignment, and cluster center update steps to form an iterative loop until the set maximum number of iterations is reached.

5. The variable fertilization control method based on a backpack fertilizer spreader according to claim 1, characterized in that: The theoretical speed calculation formula for fertilizing in the grid in the discharge speed calculation step is: V1=(F1 / A1)*W*V / K, where V1 represents the theoretical motor speed of grid 1 (r / s), F1 represents the amount of fertilizer required for grid 1 (kg), and A1 represents the area of ​​grid 1 (m 2 ), W represents the width (m), V represents the travel speed (m / s), and K represents the coefficient relationship between the motor speed (r / s) and the discharge amount (kg / s).

6. A variable fertilization control system based on a backpack fertilizer spreader, characterized in that: It comprises a control system and an actuator connected to the control system. The control system comprises a main controller, a speed measurement module, a satellite navigation module and a motor control module connected to the main controller.

7. A variable fertilization control system based on a backpack fertilizer spreader according to claim 6, characterized in that: The main controller includes an LCD screen, buttons, a 4G chip, a main chip and a serial communication unit. The LCD screen is connected to the main chip for displaying operation information. The buttons are connected to the main chip for setting operation parameters. The 4G chip is used to send operation information to the cloud platform. The main chip is used for receiving, processing, storing, and sending data from each module, identifying plots of land, and calculating the discharge speed.

8. The variable fertilization control system based on a backpack fertilizer spreader according to claim 6, characterized in that: The satellite navigation module includes a GPS receiver and a GPS antenna. The GPS receiver is used to calculate the specific longitude and latitude coordinates every 100 milliseconds using TTL data, obtain the average speed of the operator through relevant calculations, and input the obtained fertilization forward speed signal into the main controller; the GPS antenna is used to receive GPS signals.

9. The variable fertilization control system based on a backpack fertilizer spreader according to claim 6, characterized in that: The serial communication unit is connected to the satellite navigation module to communicate to obtain geographic location coordinate information and speed information; the serial communication unit is connected to the speed sensor to process the received speed information and send it to the screen and cloud platform for display.

10. The variable fertilization control system based on a backpack fertilizer spreader according to claim 6, characterized in that: The fertilizing device comprises a barrel (1), shoulder straps (2) are symmetrically fixed on the left and right sides of the barrel (1), a power supply bin (4) is arranged at the bottom of the barrel (1), a power switch (10) is installed on the left side of the power supply bin (4), a built-in battery (7) is fixed inside the power supply bin (4), the built-in battery (7) is connected to a first motor (5) through a wire, the first motor (5) is connected to a discharge channel (11) through a rotating shaft (3), the discharge channel (11) is connected to a discharge bin (14) through a discharge hose (12), the discharge bin (14) comprises a second motor (15), and the second motor (15) is connected to a rotating disk (16); The built-in battery (7) is connected to the speed sensor (6) via a wire. The speed sensor (6) is installed on the right side of the discharge channel (11) and is used in conjunction with a magnet installed on the rotating shaft. The speed sensor (6) is connected to the main chip via a sensor interface (18).

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