Pressure calibration type water and fertilizer precise fertilizer applicator and control method

Abstract

The invention discloses a pressure calibration type water and fertilizer precise fertilizer applicator and a control method thereof, and relates to the technical field of agricultural irrigation and fertilization. The invention aims to solve the problems of low metering precision, large working condition deviation, lack of dissolution early warning and the like of the existing fertilization equipment. The fertilizer applicator comprises one or more uniform-section vertical fertilizer application barrels, a bottom pressure sensor, a single-path common temperature sensor, a human-computer interaction interface and a control unit, the fertilizing barrel limits a side wall vertical structure, and the pressure sensor is additionally provided with an isolation diaphragm for preventing crystallization. The control unit abandons the dependence of traditional flow metering and booster pump calibration, collects reference pressure and total fertilizer amount to establish a mapping relation, and calculates the residual fertilizer amount in real time based on a core formula M residual = M total amount * P (t) / P reference. And the man-machine interaction interface supports independent check of multiple barrels, differential proportioning and automatic accounting of the average fertilizing amount per mu. The control method comprises the whole process of barrel check, dissolution early warning, water injection calibration, precise fertilization and shutdown filing. The device is accurate in metering without attenuation, is not interfered by pump body working conditions and a flow meter, is simple in structure and low in cost, and meets the precise fertilization requirement of modern agriculture.

Description

Technical Field

[0001] This invention relates to the field of agricultural irrigation and fertilization technology, specifically to a pressure-calibrated precision water and fertilizer applicator and its control method. It is suitable for single or multi-bucket precision water and fertilizer supply operations in various agricultural planting scenarios such as open fields, greenhouses, and orchards. It can achieve precise fertilization of multiple buckets and multiple types of fertilizers, and can work in conjunction with other agricultural Internet of Things devices to build a smart agricultural irrigation and fertilization system. Background Technology

[0002] Agricultural irrigation and fertilization are crucial aspects of modern agricultural production, and their accuracy directly impacts crop growth quality and water and fertilizer resource utilization. Currently, most commercially available water and fertilizer applicators control fertilization by combining flow metering or booster pump-calibrated flow rates with application time. To control costs, they heavily utilize inexpensive mechanical flow meters and rely on booster pump calibration parameters to calculate fertilizer application rates. However, this approach suffers from the following insurmountable technical drawbacks in practical applications:

[0003] Existing fertilization equipment mostly uses mechanical impeller flow meters as the core metering element, relying on the rotation of the impeller under the action of fluid flow to measure the amount of fertilizer applied. However, in actual agricultural applications, this type of flow meter suffers from serious accuracy degradation, specifically manifested in the following ways:

[0004] Mechanical wear and increased resistance: The bearings of the impeller flowmeter lack effective maintenance during operation, which easily leads to dry friction and a continuous increase in rotational resistance. At the same time, the salt and acid-base components in the fertilizer solution will accelerate the deterioration of the lubricating grease and the corrosion of the bearings, further deteriorating the mechanical transmission performance.

[0005] Crystallization and abrasion effect: During the flow of fertilizer solution, crystalline particles easily precipitate out. These tiny particles enter the bearing gaps, creating an abrasive effect that accelerates the wear of the bearing components, causing a shift in the linear relationship between impeller speed and actual flow rate. The combined effect of these factors leads to a significant increase in metering errors in conventional fertilizer application equipment after 3-6 months of use.

[0006] Some existing fertilization equipment relies on the rated parameters of booster pumps for open-loop control, that is, the correspondence between fertilization time and flow rate is set according to the ideal rated flow rate of the booster pump. However, there are significant differences between the actual field conditions and the factory-calibrated conditions, resulting in serious measurement inaccuracies.

[0007] Specifically, this manifests as flow rate reduction due to deviations in operating conditions: The outlet pressure of actual irrigation pipelines is often far lower than the rated pressure of the booster pump, with pressure reduction reaching up to 40%. Since flow rate and pressure have a non-linear relationship, the pressure drop leads to a significantly lower actual flow rate than the rated flow rate. If calculations are still performed based on the calibration parameters, a positive deviation will inevitably occur. In practical applications, a 2 cubic meter, 5 kg booster pump is typically selected, with the pump outlet located after the filter, which is generally 2.5-3 kg.

[0008] Equipment aging exacerbates errors: After long-term operation, irreversible factors such as internal wear of the pump body and aging of seals will lead to a decrease in volumetric efficiency, further widening the deviation between rated parameters and actual flow rate.

[0009] Some existing technologies incorporate EC (conductivity) and pH (acidity / alkalinity) sensors to participate in fertilizer application calculation or correction, but due to limitations in the working principle and installation location of the sensors, there are obvious functional defects.

[0010] Non-specificity of monitoring parameters and error transmission: EC sensors can only reflect the total ion concentration of the solution and cannot specifically distinguish the content of specific nutrients such as nitrogen, phosphorus, and potassium. Moreover, their measurement accuracy is easily affected by temperature drift. The error caused by this indirect measurement will be directly added to the measurement result, causing control deviation.

[0011] The stability bottleneck of the sensor: The glass electrode used in the pH sensor is easily contaminated by impurities, crystallization and aging in the fertilizer solution environment, resulting in slow response and drift of measurement values. It requires frequent manual calibration and is difficult to adapt to the long-term unattended agricultural operation environment.

[0012] The dual lag in time and space leads to control failure: Existing equipment typically uses monitoring points located in the main flow channel downstream of the fertilizer inlet, a typical "post-event monitoring" model. More critically, EC / pH sensors operate on electrochemical principles, requiring a certain reaction time (usually several seconds to tens of seconds) for signal establishment and stabilization. In high-velocity irrigation pipelines, this combined effect of "location lag" and "response time lag" means that by the time the sensor detects an abnormal concentration, the system has already delivered a large amount of degraded fertilizer solution into the field pipeline. The system is simply unable to achieve real-time correction within the millisecond or second-level fertilization cycle, ultimately resulting in irreversible "over-application" or "under-application."

[0013] Ignoring fertilizer solubility and failing to consider the specific solubility characteristics of different fertilizer varieties, users often add solid fertilizer to the fertilizer tank based on experience in practical applications. This easily leads to situations where the amount of fertilizer added exceeds the current water volume's solubility limit. Undissolved solid fertilizer settles at the bottom of the tank, causing fertilizer waste, inaccurate metering, wear on the booster pump impeller, and blockage of irrigation pipes and drip irrigation equipment. Furthermore, different fertilizer varieties have vastly different solubility and temperature sensitivity. Existing equipment only uses general solubility parameters without considering the specific solubility characteristics of each fertilizer variety and real-time water temperature for compensation, resulting in extremely low warning accuracy and an inability to adapt to the actual application needs of various fertilizers.

[0014] To address the aforementioned industry pain points, this invention was developed to provide a pressure-calibrated precision fertilizer and its control method that is highly compliant, logically rigorous, supports automatic calibration, eliminates the need for precise water volume control, allows for independent operation of multiple tanks, is easy to operate, provides high fertilization accuracy and long-term stable operation, can accurately match fertilizer types, has a product-specific solubility-temperature curve intelligent early warning function, completely eliminates the dependence on flow meter and booster pump calibration flow, and supports remote control. Summary of the Invention

[0015] This invention provides a pressure-calibrated precision fertilizer and its control method. This invention abandons the reliance on traditional flow metering by using the pressure calibration principle. It has the characteristics of high metering accuracy, good long-term stability, convenient multi-bucket operation, and comprehensive intelligent early warning. It can be adapted to various agricultural scenarios and meet the needs of modern agriculture for precision fertilization and unmanned operation.

[0016] A pressure-calibrated precision fertilizer includes one or more fertilizer tanks, a pressure sensor, a temperature sensor, a human-machine interface, a control unit, a fertilization execution unit, a solenoid valve, and a level switch. The fertilizer tank is a vertical container with a uniform cross-section, specifically a cylindrical or prismatic structure, with its sidewalls strictly perpendicular to the horizontal base. During installation, the tank must be placed horizontally and vertically without tilting or offset to ensure a linear relationship between the liquid column pressure and the fertilizer weight, structurally guaranteeing the metering logic. The fertilizer tank is made of corrosion-resistant, acid- and alkali-resistant food-grade or industrial-grade plastic material to prevent corrosion and damage from the fertilizer solution, while also preventing material contamination from affecting the fertilizer solution concentration. It is used to store liquid fertilizer or fertilizer solution after solid fertilizer dissolution. The number of fertilizer tanks can be flexibly set according to operational needs.

[0017] The pressure sensor can be directly installed at the bottom of the fertilizer tank to collect pressure, or it can be guided to the main body of the water and fertilizer machine through a pressure guide pipe for collection. Each fertilizer tank has an independent pressure sensor to achieve independent pressure measurement of a single tank.

[0018] The temperature sensor adopts a single-channel shared design, eliminating the need for separate equipment for each fertilizer tank. The entire equipment uses a unified water source supply, and the temperature sensor is installed in the main water inlet of the equipment or in the corresponding position on the main body of the water fertilizer machine. This ensures that the system can calculate the dissolution curve before water is injected, and the overall water source temperature can be obtained by a single channel acquisition.

[0019] The human-machine interface 2 mainly includes fertilizer injection interface, fertilizer application interface and monitoring interface functional modules, which are used to realize parameter setting, command issuance and status monitoring.

[0020] The fertilizer injection interface includes a barrel selection area, a fertilizer type selection area, a fertilizer total input box, and a fertilizer injection calibration function key.

[0021] The fertilizer bin selection area interface is labeled "Bug One," "Bug Two," "Bug Three," etc., according to the actual number of fertilizer bins configured in the system. Each bin number has an independent checkbox in front of it. This module allows users to select the target fertilizer bin for the current operation by checking the boxes, supporting both single-bin selection and simultaneous selection of multiple bins. Unselected bins are in standby isolation state by default and do not participate in subsequent calibration processes and fertilization operations, thus achieving independent control of each fertilization channel.

[0022] When the system is a single fertilizer tank, no checkbox is set.

[0023] The fertilizer type selection area uses a drop-down menu, with the menu content being the fertilizer type.

[0024] The fertilizer quantity input box allows users to enter unit quantities and integrates an automatic matching function for international standard units of measurement. When the user selects a solid fertilizer, the unit is automatically displayed as "kg" (kilogram); when the user selects a liquid fertilizer, the unit is automatically displayed as "L" (liter). This design effectively avoids mixing errors caused by manual unit conversion mistakes.

[0025] Each fertilizer tank has a fertilizer calibration button on the back.

[0026] In the field irrigation electric valve system mode, the fertilization interface includes a mode drop-down box. When selecting the rotation irrigation mode, the interface displays the unit acreage, cylinder checkbox, average fertilizer amount per acre, fertilizer amount unit box, start valve, end valve, irrigation duration, and start button. In the single fertilizer tank system, there is no cylinder checkbox.

[0027] In the mode with field irrigation electric valve system, the fertilization interface includes a mode drop-down box. When selecting manual mode from the drop-down box, the fertilization interface includes valve display groups. The number of display groups is based on the system preset, such as 32, 64, or 128. The display also includes the unit acreage, cylinder checkbox, average fertilizer amount per acre, fertilizer amount unit box, and start button. In the single fertilizer tank system, there is no cylinder checkbox.

[0028] In the mode without the field irrigation electric valve system, the fertilization interface includes a mode display box, which only shows the manual mode. The fertilization interface includes valve display groups, the number of which is preset according to the system, such as 32, 64, or 128, a cylinder checkbox, fertilizer amount, fertilizer amount unit box, and a start button. In the single fertilizer tank system, there is no cylinder checkbox.

[0029] A temperature sensor is installed at the front end of the water inlet fertilizer tank. The system collects water temperature data. After the user selects solid fertilizer and enters the fertilizer weight, if the fertilizer weight is greater than the current solubility, the system will pop up a prompt box to warn of fertilizer dissolution and give the current maximum dissolution weight.

[0030] The control unit integrates a wired and wireless dual-mode communication module, which is connected to various electrical components and is responsible for signal acquisition, logic control, data interaction and remote operation. The communication module is compatible with at least one of the multiple communication methods such as RS485, 4G, WiFi, LoRa, and NB-IoT, and can flexibly adapt to complex field communication scenarios.

[0031] The fertilizer water inlet circuit adopts an independent control design, with each fertilizer tank independently equipped with a solenoid valve to realize automatic water inlet control for a single tank, and the circuits do not interfere with each other.

[0032] The liquid level switch is fixedly installed at a preset height inside the fertilizer tank. This height is defined as the standard total liquid level after the fertilizer solution and solid fertilizer are mixed. The system automatically adds water until the liquid level switch is triggered. This logic automatically eliminates the influence of the volume occupied by the solid fertilizer on the amount of water added.

[0033] The data from the temperature sensor is used for intelligent solubility early warning. The system uses the real-time water temperature collected by the temperature sensor, combined with the pre-stored solubility-temperature data specific to each fertilizer variety, to make intelligent judgments.

[0034] The temperature sensor data is also used for data visualization and process monitoring. The system collects water temperature data at regular intervals and displays it in real time on the human-machine interface and mobile terminal in the form of curves and numerical values.

[0035] The temperature sensor also has the function of "pressure sensor temperature drift correction", that is, eliminating the influence of temperature changes on the accuracy of pressure measurement.

[0036] The control unit executes a clear and coherent core operating logic: the user first selects the target tank number (such as tank one, tank two, etc.) on the fertilizer injection interface and enters the corresponding fertilizer parameters, then triggers a water injection calibration or remote calibration command; after the system responds to the command, it automatically opens the solenoid valve of the corresponding tank to inject water until the liquid level reaches the preset standard height; then the stirring unit starts to complete the fertilizer mixing operation, and after settling until the liquid column is completely stable, it collects the reference pressure value at the bottom of the fertilizer tank; the system establishes a unique direct mapping relationship between this reference pressure value and the total amount of fertilizer entered by the user, without needing to obtain fertilizer component concentration parameters or perform complex component conversions, significantly reducing the operation threshold; in addition, in the scenario of simultaneous selection of multiple tanks, each tank supports sequential calibration in a preset order or synchronous parallel calibration, and each channel operates independently without interference.

[0037] Once the fertilization operation begins, the system uses a physical model based on the fertilizer tank having a uniform cross-section and a uniform fertilizer solution density. It then uses a dedicated core metering model to accurately calculate the remaining amount of effective components in the fertilizer solution in real time. The core calculation formula is: M_remaining = M_total × P(t) / P_baseline.

[0038] Explanation of formula symbols and applicable conditions: M_remaining: The total amount of effective fertilizer components remaining in the container at the current moment; M Total: The initial total amount of fertilizer applied by the user, expressed as weight for solid fertilizer and volume for liquid fertilizer; P(t): Real-time pressure value detected at the bottom of the fertilizer tank at the current moment; P-reference: The reference pressure value at a fixed liquid level collected after calibration; Prerequisites for application: The prerequisites and boundary conditions for the application of this core metrology model are as follows: the fertilizer tank must be a standard vertical container with a uniform cross-section and be installed in a vertical and horizontal position; the fertilizer solution must be thoroughly stirred to ensure uniform density and that the fertilizer is completely dissolved without large particles settling or crystallizing; at the same time, the system operation process must ensure that there is no liquid leakage or overflow to maintain the mass conservation assumption.

[0039] The core metering logic of this invention possesses a high degree of independence and segregation, completely decoupled from the actual operating conditions of the booster pump, fertilizer flow rate metering data, and monitoring data from EC and pH sensors. The aforementioned auxiliary monitoring data only serve the functions of real-time display, operation process traceability, and anomaly alarms, strictly limiting their involvement in the core metering calculations. This design cuts off the transmission path of external monitoring errors to the metering process at its source, effectively ensuring that fertilization accuracy is not affected by external interference and significantly improving the system's reliability.

[0040] The supporting control method includes seven core steps, executed sequentially: tank selection, fertilizer input, solubility warning judgment, water injection calibration, parameter setting, data acquisition, fertilization execution, and shutdown archiving. For solid fertilizers, the system has added a temperature-compensated intelligent solubility judgment step based on the characteristics of the variety. This step combines the unified water temperature collected from a single source with the fertilizer's specific solubility curve for calculation. Once it detects that the amount of fertilizer added exceeds the solubility limit at the current water temperature, a standardized warning signal is immediately output. This mechanism effectively avoids the risks of metering inaccuracies, equipment component wear, and irrigation pipeline blockage caused by undissolved fertilizer, comprehensively ensuring the safety and metering accuracy of fertilization operations.

[0041] Beneficial effects.

[0042] It has high fertilization accuracy and no decay over a long period of time; it adopts a pressure sensor with no moving parts, and is equipped with an isolation diaphragm to prevent crystallization and blockage. There are no problems such as bearing wear and impurity jamming. The accuracy remains at the initial level for a long time, and no regular maintenance is required. It has high metering accuracy.

[0043] Completely unaffected by the operating conditions of the booster pump; the core metering is based on the linear proportional relationship between the weight of fertilizer in the tank and the pressure, and is completely independent of the rated parameters of the booster pump, actual pressure and flow, pipeline resistance, and zone differences, thus completely solving the core pain point of deviation between the calibration and actual operating conditions of traditional equipment.

[0044] Metering and monitoring are completely separated, and errors are not propagated; pressure metering operates independently, while irrigation flow meters, EC, pH sensors, etc., only serve as auxiliary displays and alarms. Even if the monitoring sensors malfunction or drift, the accuracy of fertilizer metering will not be affected.

[0045] Dedicated intelligent solubility warning: Combining fertilizer variety-specific solubility-temperature curves with real-time water temperature, it accurately judges fertilizer dissolution risk and outputs standardized warning signals, rather than a single pop-up window, adapting to different interaction scenarios.

[0046] The pressure proportional measurement method employed in this invention exhibits excellent temperature stability. Since the pressure sensor detects the weight (force) of the liquid column per unit area, according to the fluid mechanics principle P=mg / S, the pressure signal is independent of the liquid density. Even if the fertilizer solution expands or contracts (density changes) due to diurnal temperature variations or changes in ambient temperature, its total weight and the proportion of the remaining weight remain constant, and the pressure reading remains constant. Therefore, compared to traditional volumetric measurement methods, this invention inherently eliminates volumetric measurement errors caused by temperature changes from a physical perspective, requiring only routine temperature drift compensation of the sensor hardware, greatly improving the system's environmental adaptability.

[0047] Attached image description.

[0048] Figure 1 This is a schematic diagram of the overall water and fertilizer machine system provided in an embodiment of the present invention.

[0049] Figure 2 This is a front view of the water and fertilizer machine body provided in an embodiment of the present invention.

[0050] Figure 3 This is a side view of the water and fertilizer machine body provided in an embodiment of the present invention.

[0051] Figure 4 This is a rear view of the water and fertilizer machine body provided in an embodiment of the present invention.

[0052] Figure 5 This is a front view of the fertilizer bucket provided in an embodiment of the present invention.

[0053] Figure 6 This is the fertilizer injection interface for a single fertilizer tank provided in an embodiment of the present invention.

[0054] Figure 7 This is the fertilizer injection interface of the three fertilizer tanks provided in this embodiment of the invention.

[0055] Figure 8 This is a fertilization interface for a single fertilizer tank with an electric valve in a rotary irrigation mode, provided in an embodiment of the present invention.

[0056] Figure 9 This invention provides a manual fertilization interface for a single fertilizer tank with an electric valve, as shown in the embodiments of the present invention.

[0057] Figure 10 This invention provides a manual fertilization interface for a single fertilizer tank without an electric valve, as provided in an embodiment of the invention.

[0058] Figure 11 This is a fertilization interface for a three-fertilizer-bucket-with-electric-valve-driven rotating irrigation mode provided in an embodiment of the present invention.

[0059] Figure 12 This is a manual fertilization interface with an electric valve for three fertilizer tanks provided in an embodiment of the present invention.

[0060] Figure 13 The embodiment of the present invention provides a manual fertilization interface for three fertilizer tanks without electric valves.

[0061] Figure 14 The fertilizer tank with electric valve monitoring interface is provided in the embodiment of the present invention.

[0062] Figure 15 The fertilizer tank monitoring interface without electric valve is provided in the embodiment of the present invention.

[0063] In the diagram: 1-Water and fertilizer machine, 2-Human-machine interface, 3-Control unit, 4-Fertilization unit, 5-Temperature sensor, 6-Fertilizer tank, 7-Pressure sensor, 8-Solenoid valve, 9-Level switch, 10-Stirring unit, 21-Fertilizer injection interface, 211-Fertilizer tank checkbox on the fertilizer injection interface, 212-Fertilizer selection drop-down box, 213-Fertilizer total amount input box, 214-Fertilizer total amount unit box, 215-Fertilizer injection calibration button, 22-Fertilization interface, 221-Mode selection drop-down box, 222-Unit acreage, 223-Average fertilizer application per acre, 224-Fertilizer unit, 225-Start valve, 226-Termination valve, 227- Irrigation duration, 228-Start button, 229-Valve checkbox, 2210-Fertilizer amount input box, 23-Monitoring interface, 231-Fertilizer tank display box with drop-down menu, 232-Currently open valve display box, 233-Irrigation duration display box, 234-Irrigated duration display box, 235-Total fertilizer amount, 236-Remaining fertilizer amount, 237-Fertilizer amount injected this time, 238-Remaining fertilizer amount this time, 239-Water injection solenoid valve status display box, 2310-Agitator status display box, 2311-Level switch status display box, 2312-Fertilizer injection device status display box, 2313-Pressure sensor pressure value display box.

[0064] Detailed implementation method.

[0065] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The following description is intended to clearly illustrate the technical solutions of the present invention, and not to limit its scope of protection. Those skilled in the art should understand that adjustments to the number of filter units, the material of the sealing components, and the cleaning parameters, without departing from the core concept of the present invention, are all within the scope of protection of the present invention.

[0066] Equipment installation and initialization.

[0067] Several cylindrical fertilizer tanks with uniform cross-sections are configured according to operational requirements. During installation, a level is required for calibration to ensure the tanks are vertical, the bottom is horizontal, and there is no tilting or offset, strictly meeting the prerequisite requirements for the metering structure. Each tank is sequentially labeled with a number (e.g., Tank 1, Tank 2) for identification. The pressure sensing unit is installed in a dedicated groove at the bottom of the tank, using a structure with no moving parts and an accuracy better than ±0.5%. Its pressure-sensing diaphragm has an additional corrosion-resistant, anti-crystallization isolation diaphragm on the outer layer, directly contacting the fertilizer solution and effectively preventing damage to the core sensing element from impurities and crystals. The system is based on a unified water supply architecture, deploying a single-channel temperature sensor only at the main water inlet or the main unit, eliminating the need for independent deployment in each tank. The water temperature data collected by this single sensor is simultaneously used for temperature correction of the pressure sensor and intelligent solubility judgment, achieving data reuse and significantly reducing system hardware redundancy.

[0068] Each fertilizer tank has an independent corrosion-resistant solenoid valve installed at its water inlet. A fixed-height liquid level switch is installed inside the tank; the height is not adjustable after installation. The fixed liquid level is defined as the total liquid level after mixing the fertilizer solution and fertilizer. The system automatically fills water until the liquid level switch is triggered. A stirring unit is installed inside the tank, with the stirring paddle extending into the liquid. The stirring speed is adjustable to ensure thorough mixing of the fertilizer solution. The control unit is connected to each pressure sensor, single-channel temperature sensor, solenoid valve, liquid level switch, stirring unit, fertilizer application unit, and human-machine interface. The fertilizer application unit uses a booster pump or venturi tube, with its input connected to the fertilizer tank outlet and its output connected to the irrigation pipeline. A communication module connects to field electric valves, irrigation flow meters, EC sensors, pH sensors, soil monitoring equipment, meteorological monitoring equipment, a cloud server, and mobile terminals to complete communication parameters and initial system parameter settings. The pressure sensor temperature drift correction function is enabled to ensure normal equipment operation.

[0069] Fertilizer solubility database preset.

[0070] The control unit has a pre-stored database of solubility values ​​for common fertilizers such as urea, potassium nitrate, potassium sulfate, potassium dihydrogen phosphate, and general compound fertilizers. It covers precise solubility thresholds for different temperature ranges, supports cloud updates and custom fertilizer parameter input, and marks the stirring time and settling time for complete dissolution of various fertilizers to ensure accurate solubility judgment for various fertilizers.

[0071] The process includes selecting the container, inputting fertilizer, and issuing an early warning for the solubility of solid fertilizer.

[0072] Barrel selection and parameter input.

[0073] Before operation, the user selects the target application tank in the "Tank Selection Area" of the fertilizer application interface via a checkbox. The system supports flexible operation modes: for single-tank operation, only tank one or tank two is selected; for simultaneous operation of multiple tanks, both tank one and tank two can be selected simultaneously; if the fertigation machine comes standard with only one fertilizer tank, the checkbox will be automatically hidden or the tank will be selected by default. After selecting the tank, the user selects the fertilizer type; after selecting the type, the user enters the total amount of fertilizer (solid fertilizer is in kg, liquid fertilizer is in L).

[0074] Intelligent solubility warning (only for solid fertilizers).

[0075] The system automatically reads the real-time water temperature collected by a single-channel temperature sensor. For solid fertilizers, the control unit calculates the maximum amount of fertilizer that can be dissolved at the current water temperature based on a pre-stored solubility database specific to the selected fertilizer variety and the water volume corresponding to a fixed liquid level, and determines whether the amount of fertilizer input by the user exceeds the dissolving capacity.

[0076] If the solubility is exceeded, the system will output a solubility warning signal and pop up a prompt box on the human-computer interaction interface, displaying the solubility risk and the recommended maximum amount of fertilizer, and providing the options of "Continue Calibration" or "Cancel Calibration"; the user can proceed to the next step only after confirmation.

[0077] If it is liquid fertilizer, since it is a homogeneous solution, there is no risk of incomplete dissolution. The system automatically skips the solubility warning step and directly enters the calibration process.

[0078] Water injection calibration.

[0079] After the user clicks "Water Injection Calibration" on the corresponding selected container, the system automatically controls the solenoid valve of the selected container to inject water to a fixed level (triggered by the level switch), starts the stirring unit to mix the fertilizer solution, and after settling and stabilizing, collects the reference pressure value P at the bottom of the container and establishes a unique calibration relationship between the reference pressure P and the total amount of fertilizer input by the user. No manual intervention is required throughout the process.

[0080] Liquid level control: The status of the liquid level switch is monitored in real time during the water injection process. When the liquid level reaches the preset height and triggers the liquid level switch, the solenoid valve is immediately closed to stop water injection.

[0081] Mixing and settling: After watering, continue stirring for a preset time (e.g., 3-5 minutes) to ensure the fertilizer solution is completely dissolved and evenly mixed; then stop stirring and let it stand for a preset time (e.g., 1-2 minutes) until the liquid column is completely stable and there are no bubbles on the surface, thus eliminating dynamic interference.

[0082] Reference calibration: The control unit collects the current value of the corresponding pressure sensor, records it as the reference pressure reference P reference, and establishes a unique direct mapping relationship between this value and the total amount of fertilizer M input by the user to complete the calibration.

[0083] Multi-bucket logic: If the user selects multi-bucket synchronous operation, the system will complete the calibration of each bucket in sequence according to the preset control strategy (serial mode), or control each bucket to complete the calibration independently in parallel (parallel mode). Data from each channel is collected independently and does not interfere with each other.

[0084] Fertilization interface parameter settings.

[0085] In the mode including the electric valve system for field irrigation, click the mode drop-down box in the upper left corner of the fertilizer application interface, select the rotation irrigation mode from the drop-down box, and the interface will display the unit acreage, cylinder check box, average fertilizer amount per acre, fertilizer amount unit box, start valve, end valve, irrigation duration, and start button respectively; when it is a single fertilizer tank system, there is no cylinder check box.

[0086] In the mode including the electric valve system for field irrigation, click the mode drop-down box in the upper left corner of the fertilizer interface, select manual mode from the drop-down box, and the interface will display each valve button, unit acreage, cylinder checkbox, average fertilizer application per acre, fertilizer unit box, and start button; when it is a single fertilizer tank system, there is no cylinder checkbox.

[0087] In the mode without the field irrigation electric valve system, the mode display box in the upper left corner of the fertilizer interface only shows the manual mode and cannot be clicked. The fertilizer interface only displays the cylinder check box, fertilizer amount, fertilizer amount unit box, and start button. When it is a single fertilizer tank system, there is no cylinder check box.

[0088] Data acquisition and visualization.

[0089] In the field irrigation electric valve system mode, a fertilizer tank drop-down box is set in the upper left corner in multi-tank mode, and a fertilizer tank display box is set in single-tank mode. The display box cannot be clicked. The left side of the interface is a fertilizer tank interface, which includes a water injection solenoid valve status display box, a stirring device status display box, a liquid level switch display box, a fertilizer injection unit status display box, and a pressure value display box. The right side of the interface is the fertilizer status section, which displays the currently open valve, irrigation duration, irrigation duration, total fertilizer amount, remaining fertilizer amount, current fertilizer injection amount, and current remaining fertilizer amount.

[0090] In the mode without the field irrigation electric valve system, the fertilizer tank drop-down box is set in the upper left corner in the multi-tank mode, and the fertilizer tank display box is set in the single-tank mode. It cannot be clicked and selected. The left side of the interface is a fertilizer tank interface, which includes the status display box of the water injection solenoid valve, the status display box of the stirring device, the liquid level switch, the status display box of the fertilizer injection unit, and the pressure value display box. The right side of the interface is the fertilizer status section, which displays the total amount of fertilizer, the amount of fertilizer remaining, the amount of fertilizer injected this time, and the amount of fertilizer remaining this time.

[0091] The system periodically and frequently collects real-time pressure, temperature, irrigation flow, EC value, pH value, water temperature, soil moisture, and meteorological data. Combined with the core metering formula, it calculates the remaining fertilizer amount and the amount of fertilizer already applied in real time, and displays them in the form of curves and numerical values ​​on the human-machine interface and mobile terminals. All monitoring data is only used for over-monitoring and abnormal alarms and is absolutely not involved in metering calculations. At the same time, it is cached locally and uploaded to the cloud for easy historical traceability and report export.

[0092] Fertilization can be initiated manually, remotely via a terminal, or automatically triggered by equipment linkage. The control unit collects the real-time pressure value P(t) at the bottom of the selected tank at high frequency. Strictly adhering to the core measurement formula M_remaining = M_total × P(t) / P_benchmark, it accurately calculates the remaining effective components of the fertilizer solution in the tank in real time. Simultaneously, it compares the preset average fertilization rate per acre and the corresponding target total fertilization rate for that tank, automatically adjusting the start / stop of the fertilization equipment, the switching of irrigation zones, and the output flow rate of the fertilizer solution to ensure that the fertilizer application rate per tank accurately matches the average acre standard. In automatic mode, the system completes the fertilization operation sequentially according to the preset zone order, simultaneously verifying the acre-level application rate during zone fertilization to achieve uniform and precise fertilization across the entire area. In manual mode, the system maintains a constant flow output, with manual control of the irrigation pipeline. The interface displays the real-time fertilizer application rate per tank, the remaining average acre-level application rate, and the progress towards the target, providing clear and traceable data throughout the process. The entire fertilization process is completely unaffected by external factors such as booster pump wear, changes in pipeline resistance, and fluctuations in field conditions. Even after long-term use, the booster pump performance deteriorates, but the metering results remain accurate and stable without any deviation, and the differentiated per-acre ratio of multiple tanks remains undisturbed.

[0093] Downtime and data management.

[0094] Once the target fertilization amount is reached or a remote stop command is received, the system automatically shuts down the fertilization execution components and field valves, ending the operation. It automatically saves all data from the entire operation process, including selected tank information, calibration parameters, fertilizer information, fertilization amount, pressure curve, monitoring data, fault records, etc., and uploads them to the cloud. It supports report export and operation analysis, providing data support for subsequent fertilization plan optimization.

[0095] Fault diagnosis and intelligent linkage.

[0096] The equipment has a full-dimensional self-diagnostic function, which can monitor various abnormal situations in real time, such as water injection timeout, sensor malfunction, communication interruption, stirring failure, and excessive pressure drift. When an abnormality occurs, it will immediately trigger an audible and visual alarm and push a remote reminder at the same time. At the same time, it can automatically trigger or suspend fertilization according to soil moisture, automatically lock the fertilization function during rainfall, and issue a timely warning when the EC / pH value is abnormal, realizing intelligent irrigation closed-loop management without changing the core metering logic throughout the process, and firmly ensuring the accuracy of fertilization.

Claims

1. A pressure-calibrated precision fertilization machine and its control method, characterized in that, include: One or more fertilizer tanks, pressure sensors, temperature sensors, human-machine interface, control unit, fertilizer application unit, solenoid valve, level switch and stirring unit; The fertilizer bucket adopts a vertical container structure with a known cross-sectional integral distribution. The side walls and bottom of the bucket are perpendicular to each other, and the equipment is kept vertically placed in the installed state. The human-machine interface includes at least a fertilizer injection interface, a fertilizer application interface, and a monitoring screen; the fertilizer injection interface includes a single-tank interface with an electric valve, a multi-tank interface with an electric valve, a single-tank interface without an electric valve, and a multi-tank interface without an electric valve; the fertilizer application interface includes a single-tank interface with an electric valve, a multi-tank interface with an electric valve, a single-tank interface without an electric valve, and a multi-tank interface without an electric valve; the monitoring screen includes both interfaces with and without electric valves. The pressure sensor corresponds to a fertilizer tank and is fixedly installed at the bottom of the corresponding fertilizer tank or on a pressure-sensing pipe parallel to the bottom of the tank, used to collect the pressure data at the bottom of the fertilizer solution inside the tank; the temperature sensor is a single-channel shared type and is installed at the main water inlet of the equipment or inside the main body of the water-fertilizer machine; the solenoid valve corresponds to a fertilizer tank and is installed on the water inlet pipe of the corresponding fertilizer tank; the liquid level switch is fixedly installed at a preset height inside the fertilizer tank and is used to trigger a fixed liquid level signal. The control unit (3) is electrically connected to the pressure sensor, temperature sensor, solenoid valve, liquid level switch, fertilizer execution unit and human-machine interface respectively, and the control unit has a built-in communication module; The control unit is configured to execute the following control logic: acquire the target tank selection signal transmitted by the human-machine interface, respond to the water injection calibration command or remote calibration command, control the solenoid valve corresponding to the selected tank to open the water injection until the liquid level switch triggers the fixed total liquid level height and then closes the solenoid valve; start the stirring function to mix the fertilizer solution evenly, let it stand for a preset time after mixing, collect the reference pressure value P reference through the corresponding bottom pressure sensor, and establish a unique corresponding proportional relationship between the reference pressure value and the total amount of fertilizer parameter input by the user; after entering the fertilization operation process, based on the vertical structure of the fertilizer tank with equal cross-section, calculate the remaining amount of fertilizer in real time according to the core measurement formula M remaining = M total × P (t) / P reference.

2. The pressure-calibrated precision fertilizer applicator according to claim 1, characterized in that, The control unit calculates the fertilizer application rate entirely based on the pressure data collected by the pressure sensor. This method abandons the traditional accumulation method using flow meters or booster pumps and instead employs a mass back-calculation method using a "pressure sensor + equal cross-section container." It eliminates the need for intervention or correction from any flow metering equipment, booster pump calibration parameters, EC sensor data, pH sensor data, or other auxiliary monitoring equipment. The pressure sensor uses a high-precision pressure detection element, and its measurement data serves as the sole basis for fertilizer application rate calculation. This eliminates the cumulative errors caused by unstable pump operating conditions and pipeline impurities interfering with the flow meter from a physical perspective, resulting in significant technical benefits.

3. The pressure-calibrated precision fertilizer applicator according to claim 1, characterized in that, The introduction of a solubility-temperature curve for solid fertilizer dissolution warning solves the common pain point of "undissolved fertilizer causing blockage" in the actual application of fertilizer applicators. The control unit is also configured to: for solid fertilizer, calculate the maximum dissolution amount under the current operating conditions based on the specific solubility-temperature relationship of the selected fertilizer type and the water temperature collected by the single-channel temperature sensor, judge the fertilizer dissolution risk, and output a solubility warning signal if the dissolution capacity is exceeded, and display the warning information and remind the maximum fertilizer application amount on the human-machine interface, and provide operation options to continue calibration or cancel calibration.

4. The pressure-calibrated precision fertilizer applicator according to claim 1, characterized in that, The system does not require users to input complex parameters such as density and concentration. Instead, it automatically establishes the correspondence between pressure and weight through a closed-loop process of "water injection - stirring - settling - benchmark acquisition". This greatly reduces the user's operating threshold. After the water injection calibration function key is triggered, the system automatically executes the water filling and pressure measurement operation process: the control unit automatically controls the solenoid valve to open the water injection, and automatically stops the water injection based on the position signal of the liquid level switch fixedly installed at a preset height inside the equal-diameter fertilizer tank, accurately fixing the liquid level in the tank at the preset height. The user only needs to input a weight parameter in the total fertilizer input box on the fertilizer injection interface. Without any other operation or calculation, the system automatically completes water injection, mixing, settling, pressure acquisition, and calibration of the correspondence between the benchmark pressure value P and the weight parameter. The fertilizer tank has a structure with a known cross-sectional integral distribution to ensure that the liquid level height and liquid volume in the tank are in a fixed proportional relationship.

5. The pressure-calibrated precision fertilizer applicator according to claim 1, characterized in that, The fertilization modes include automatic control mode and manual auxiliary mode. In automatic mode, the control unit controls the electric valves and fertilization channels in the field according to preset parameters to achieve precise fertilization in different areas. In manual mode, the control unit outputs a fixed amount of fertilizer, and the irrigation pipeline is opened and closed manually. Both modes support remote control via mobile terminal.

6. The pressure-calibrated precision fertilizer applicator according to claim 1, characterized in that, The water and fertilizer machine monitoring interface is divided into two parts: real-time values ​​and status values. The real-time value interface displays the currently open valve, irrigation duration, remaining duration, total fertilizer application, remaining fertilizer amount, current fertilizer injection amount, and current remaining fertilizer amount. The status value displays the status of the water injection solenoid valve, pressure value, stirring motor status, and temperature value.

7. The pressure-calibrated precision fertilizer applicator according to claim 1, characterized in that, It also includes a mixing unit, which is located inside the fertilizer tank and electrically connected to the control unit. During the calibration process, the fertilizer solution is mixed evenly to ensure uniform fertilizer solution density.

8. The pressure-calibrated precision fertilizer applicator according to claim 1, characterized in that, The measurement error of the pressure sensor is controlled within ±0.5%.

9. A control method for a fertilizer applicator according to any one of claims 1-8, characterized in that, Includes the following steps: Barrel selection steps: On the fertilizer injection interface of the human-computer interaction interface, the user selects the target barrel for single or multiple barrels by checking the box in front of the barrel number. Fertilizer input steps: Users select the fertilizer type through the human-computer interaction interface and input the weight of solid fertilizer or the volume of liquid fertilizer; Solubility warning steps: For solid fertilizers, the control unit combines the variety-specific solubility-temperature curve with the water temperature collected from a single source to determine the dissolution risk and output corresponding warning information; Water injection calibration steps: When the user triggers the calibration command, the system automatically completes the water injection, stirring, and settling process for the selected tank, collects the reference pressure, and completes the mapping calibration with the total amount of fertilizer. Parameter setting steps: Input the area of ​​a single irrigation unit, in the fertilizer application amount per mu section of the fertilizer application interface, set the corresponding fertilizer application amount per mu for each selected bucket, the system will automatically calculate the target fertilizer amount per bucket, select the fertilizer application mode, and enable the corresponding intelligent linkage function. Metered fertilization process: The system collects real-time pressure data of the selected tank at high frequency, calculates the remaining amount of fertilizer according to the core metering formula, automatically controls the operation of the fertilization execution unit, and accurately outputs fertilizer. Shutdown and archiving steps: After reaching the target fertilization amount or receiving a shutdown command, the operation will automatically stop, and the entire process operation data will be saved and uploaded.

10. The control method according to claim 9, characterized in that, During the water injection calibration process, the total liquid level is fixed at the liquid level switch trigger height, and the system automatically offsets the impact of solid fertilizer volume occupation, requiring no additional volume compensation.

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