Fertilization quality metering device applied to intelligent fertilizer applicator

Abstract

The invention relates to the field of intelligent agriculture, and discloses a fertilization quality metering device applied to an intelligent fertilizer applicator. The fertilizer suction passage is used for connecting the fertilizer liquid storage container and the fertilizer applicator; a filter assembly; the filtering assembly is arranged on the fertilizer suction passage and is used for filtering the flowing fertilizer liquid; an impeller flowmeter; the impeller flowmeter is arranged on the fertilizer suction passage and is used for acquiring the volume of the fertilizer liquid flowing through the fertilizer suction passage; the density measuring assembly is communicated with the fertilizer absorbing passage and is used for collecting a fertilizer liquid sample and measuring the density of the fertilizer liquid; a control unit; the control unit is electrically connected with the impeller flowmeter and the density measuring assembly. By means of the technical scheme, accurate metering of the fertilization quality is achieved.

Description

Technical Field

[0001] This application relates to the field of agricultural fertilization, and more particularly to a fertilization quality measurement device for use in intelligent fertilizer applicators. Background Technology

[0002] With the development of modern agricultural technology, fertigation technology has been widely used in field crops due to its advantages of water conservation, fertilizer conservation, and labor saving. Intelligent fertilizer applicators in fertigation systems typically use a fertilizer suction channel to draw fertilizer solution from a storage tank and deliver it to the crop roots.

[0003] Currently, most fertilizer application equipment on the market uses flow meters to measure the volume of fertilizer solution. However, in agricultural production material management, the procurement, inventory, and cost accounting of solid and liquid fertilizers are usually based on mass. Because different ratios and types of fertilizer solutions have significant density differences, simple volume measurement cannot accurately reflect the actual weight of fertilizer applied. This makes it difficult for managers to accurately assess the total amount of fertilizer consumed during planting, and also makes it difficult to effectively supervise fertilizer loss and worker violations during the fertilization process.

[0004] Solving this technical problem is a technical challenge that needs to be overcome by those skilled in the art. Summary of the Invention

[0005] This application provides a fertilizer quality measuring device for use in intelligent fertilizer applicators, which at least partially solves the above-mentioned technical problems.

[0006] To achieve the above objectives, this application provides a fertilizer application quality measuring device for use in intelligent fertilizer applicators, comprising: Fertilizer absorption passage; the fertilizer absorption passage is used to connect the fertilizer solution storage container and the fertilizer applicator; A filter assembly; the filter assembly is disposed on the fertilizer absorption passage and is used to filter the flowing fertilizer solution; Impeller flow meter; the impeller flow meter is installed on the fertilizer suction passage and is used to obtain the volume of fertilizer solution flowing through the fertilizer suction passage; A density measurement component, connected to the fertilizer absorption pathway, is used to collect fertilizer solution samples and measure the density of the fertilizer solution. Control unit; the control unit is electrically connected to both the impeller flow meter and the density measurement assembly; the control unit is configured as follows: Start the fertilizer suction operation and use an impeller flow meter to measure the volume of fertilizer solution flowing through it, which is recorded as the first volume; Obtain the fertilizer solution density measured by the density measurement component; The corrected volume is obtained by correcting the first volume based on the currently measured fertilizer solution density; The fertilization quality for the current sampling period is obtained based on the corrected volume and the currently measured fertilizer solution density.

[0007] In this embodiment of the application, the fertilizer solution mass is calculated by the density measurement component and the impeller flow meter through the above technical solution. The volume measurement value obtained by the impeller flow meter is corrected by the obtained density value. The fertilizer mass is obtained by subtracting the water mass from the fertilizer solution mass. The systematic measurement deviation caused by the impeller flow meter due to the change of fluid properties is eliminated. It can be used to statistically analyze the mass of a single application of fertilizer as well as the mass of multiple applications of fertilizer.

[0008] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of an implementation system of a fertilizer quality measuring device applied to an intelligent fertilizer applicator, provided in an exemplary embodiment of this application; Figure 2 This is a schematic diagram of a fertilizer quality measuring device applied to an intelligent fertilizer applicator according to this application; Figure 3 This is a schematic diagram of the density measurement component of this application. Detailed Implementation

[0011] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0012] This application provides a fertilizer application quality measurement device for use in intelligent fertilizer applicators. Please refer to [link / reference]. Figure 1-3 The fertilizer quality measuring device for use in intelligent fertilizer applicators provided in this application embodiment includes: Fertilizer absorption passage; the fertilizer absorption passage is used to connect the fertilizer solution storage container and the fertilizer applicator; the fertilizer absorption passage refers to the fluid transport pipeline system that connects the fertilizer solution storage container and the main unit of the fertilizer applicator, and is used to connect the fertilizer solution storage container and the fertilizer applicator.

[0013] A filter assembly is disposed on the fertilizer absorption passage and is used to filter the fertilizer solution flowing through it. The filter assembly is installed at the front end of the fertilizer absorption passage and is used to intercept suspended particles and crystalline impurities in the fertilizer solution to prevent clogging of the flow meter and nozzle.

[0014] Impeller flow meter; the impeller flow meter is installed on the fertilizer suction passage and is used to obtain the volume of fertilizer liquid flowing through the fertilizer suction passage; the impeller flow meter is a volumetric flow sensor based on the pulse signal generated by the fluid driving the impeller to rotate. Its output pulse frequency is proportional to the instantaneous flow rate. The accumulated pulse number can be converted into the flow volume. It is suitable for metering medium and low viscosity liquids and is used to obtain the volume of fertilizer liquid flowing through the fertilizer suction passage, which is recorded as the first volume, that is, the uncorrected volume measurement value of the original output of the impeller flow meter.

[0015] A density measurement component, connected to the fertilizer absorption pathway, is used to collect fertilizer solution samples and measure the density of the fertilizer solution. Control unit; the control unit is electrically connected to both the impeller flow meter and the density measurement assembly; the control unit is configured as follows: Start the fertilizer suction operation and use an impeller flow meter to measure the volume of fertilizer solution flowing through it, which is recorded as the first volume; Obtain the fertilizer solution density measured by the density measurement component; The corrected volume is obtained by correcting the first volume based on the currently measured fertilizer solution density; The fertilization quality for the current sampling period is obtained based on the corrected volume and the currently measured fertilizer solution density.

[0016] Specifically, traditional fertilizer applicators rely solely on flow meters to obtain the volume of fertilizer solution and assume a constant density to calculate mass. However, the actual density of the fertilizer solution varies depending on the type and concentration of fertilizer, leading to significant errors in mass conversion. This invention calculates the mass of the fertilizer solution using a density measurement component and an impeller flow meter, and corrects the volume measurement value obtained by the impeller flow meter with the obtained density value. The mass of the fertilizer solution is obtained by subtracting the mass of water from the mass of the fertilizer solution. This application also eliminates the systematic measurement deviation caused by changes in fluid properties of the impeller flow meter, enabling statistical analysis of both single and multiple fertilizer applications.

[0017] In some embodiments, the density measurement component includes: A fixed container; the top of the fixed container is provided with a drain hole; A weighing sensor; the fixed container is mounted on the weighing sensor; the weighing sensor is used to measure the weight of the fixed container and the fertilizer solution inside it; A storage tank; the storage tank is located below the fixed container and is used to receive the fertilizer solution overflowing from the drain hole and the fertilizer solution discharged from the fixed container after the measurement is completed; Liquid level measuring plate; the liquid level measuring plate is installed inside the liquid storage tank and is used to monitor the liquid level status inside the liquid storage tank; The liquid inlet branch connects the fertilizer absorption passage to the fixed container and is used to inject liquid into the fixed container; A reflux branch connects the liquid storage tank to the fertilizer absorption passage, and a reflux valve is provided on the branch. The control unit is also configured to: Control the opening of the inlet branch to allow the fertilizer solution to enter the fixed container; When the liquid level in the storage tank is detected to be increasing by the liquid level measuring plate, it is determined that the fertilizer solution in the fixed container has overflowed from the drain hole and reached the preset fixed volume. The weighing sensor is then triggered to obtain the weight of the fertilizer solution in the fixed container and calculate the density in combination with the preset fixed volume of the fixed container. After the density calculation is completed, the fertilizer solution in the fixed container is discharged into the storage tank and the reflux valve is opened. The negative pressure generated by the fertilizer applicator is used to draw the fertilizer solution in the storage tank back to the fertilizer absorption passage.

[0018] In some embodiments, the control unit is further configured to: During the process of controlling the opening of the reflux valve to draw back the liquid, the liquid level in the storage tank is monitored by the liquid level measuring plate. When the liquid level is detected to drop to the preset safety lower limit, the reflux valve is closed to prevent air from entering the fertilizer absorption passage through the storage tank.

[0019] Specifically, when using the negative pressure of the fertilizer applicator to draw fertilizer solution from the storage tank back to the main process, if the reflux valve remains open until the liquid in the tank is completely emptied, external air will instantly rush into the fertilizer suction passage through the reflux branch, which can easily lead to: 1. Gas-liquid two-phase flow causing instability in the impeller speed of the flow meter, resulting in inaccurate volume measurement; 2. Residual air bubbles circulating with the fertilizer solution to the density measurement component, interfering with the weighing process of the fixed container, and the adhesion of air bubbles causing the weight measurement value to be lower, resulting in distorted density calculation. This application, based on a liquid level measuring plate, implements liquid level tracking during the reflux process. When the monitored value drops to a calibrated preset safety lower limit, this threshold ensures that a trace liquid seal layer is retained at the bottom of the tank, and the control unit closes the reflux valve to block the air intrusion path.

[0020] In some embodiments, the filter assembly is equipped with a backwashing system; the backwashing system includes: A drain valve is located on the front side of the liquid inlet end of the filter assembly and leads to the drain tank; A backwash passage is connected to an external pressurized water source and the rear side of the liquid outlet of the filter assembly. A backwash valve is provided on the passage. A fertilizer suction valve is located downstream of the filter assembly on the fertilizer suction passage. The control unit is configured to perform a backwashing mode: close the fertilizer suction valve, open the backwash valve and the drain valve, use external pressurized water to backwash the filter assembly and discharge the wastewater through the drain valve.

[0021] Specifically, during continuous operation, if the filter components of an intelligent fertilizer applicator become clogged due to the accumulation of impurities in the fertilizer solution, it not only interrupts the fertilization process and reduces operational efficiency, but also causes pressure fluctuations and pulsating flow in the flow channel, distorting the pulse signal of the impeller flowmeter. Impurities entering the density measurement component can easily contaminate the drain hole of the fixed container or adhere to the weighing sensor, causing deviations in density data. This design uses a fertilizer suction valve, a backwash valve, and a drain valve. During backwashing, the fertilizer suction valve is closed to cut off the main fertilizer solution passage, while the backwash valve and drain valve are opened. Pressurized water from outside is used to backwash the filter components from the outlet end under high pressure, causing impurities to detach from the filter screen and be discharged from the system through the drain valve at the front of the inlet end, thus extending the life of the filter components.

[0022] In some embodiments, the control unit is configured to: After obtaining the real-time density value measured by the density measurement component, the density interval in which the real-time density value is located is retrieved from the database, and the flow correction coefficients corresponding to the reference density values ​​at both ends of the density interval are obtained. Based on the flow correction coefficients at both ends of the interval, a linear interpolation algorithm is used to calculate the target flow correction coefficients that are suitable for the current fertilizer solution. The target flow correction coefficient is applied as a multiplier factor to the first volume to obtain the corrected volume, thereby eliminating the volume measurement error of the impeller flowmeter caused by the change in fertilizer solution density.

[0023] Specifically, the factory calibration of impeller flowmeters is typically based on clean water with a density of approximately 1.0 g / mL. However, the actual density of fertilizer solutions varies due to differences in fertilizer type, concentration, and temperature; urea solution has a density of approximately 1.05 g / mL, while high-concentration compound fertilizers can reach 1.35 g / mL. This leads to changes in fluid viscosity and inertial forces, causing a shift in the impeller's response characteristics. This application's control unit acquires the fertilizer solution density output from the density measurement component in real time, locates the target range in a pre-calibrated density-flow correction coefficient database, generates a target flow correction coefficient matching the current physical properties using a linear interpolation algorithm, and uses this coefficient as a multiplier factor to correct the first volume of the impeller flowmeter's original output, ensuring that the corrected volume reflects the actual volume of fertilizer solution flowing through it.

[0024] In some embodiments, the control unit is further configured to: In N consecutive density measurement cycles, record the number of pulse signals output by the impeller flowmeter during each injection of liquid into the fixed container until overflow; N≥2; The total number of N pulse signals is accumulated, and the real-time flow coefficient K value of the impeller flow meter is calculated based on N times the preset fixed volume of the fixed container; The real-time flow coefficient K is set as the current volume conversion reference coefficient of the impeller flow meter; in subsequent sampling periods, the original pulse signal output by the impeller flow meter is converted into the first volume based on the volume conversion reference coefficient.

[0025] Specifically, during long-term operation, the impeller flow meter is affected by bearing wear, impeller scaling, and fertilizer adhesion, causing the factory flow coefficient K value to drift. This application calculates the real-time K value by accumulating the total number of pulse signals generated by the impeller flow meter flowing through the standard volume over N consecutive density measurement cycles, using K = total number of pulses / (N × fixed container volume). The updated K value is used as the volume conversion reference coefficient to eliminate the error introduced by hardware drift.

[0026] In some embodiments, the metering device further includes a temperature sensor; the temperature sensor is used to collect the temperature of the fertilizer solution in real time. The control unit is also configured to: Obtain the temperature of the fertilizer solution as measured by the temperature sensor; The density of the fertilizer solution is obtained by temperature compensation based on the weight measured by the weighing sensor and the density value calculated by the preset fixed volume of the fixed container, according to the temperature of the fertilizer solution. When the real-time temperature is lower than a preset low-temperature threshold, the control unit is also configured to extend the backwashing duration during the backwashing process.

[0027] Specifically, fertilizer solution density exhibits temperature-dependent characteristics; as temperature changes, density also changes. This application uses a temperature sensor to acquire the fertilizer solution temperature in real time and calls a temperature-density compensation model matched to the fertilizer type to correct the measured density to the equivalent value at the standard reference temperature, making quality measurement more accurate. At low temperatures, the viscosity of the fertilizer solution increases sharply, making it prone to crystallization. Standard backwashing time is insufficient to remove deposits adhering to the micropores of the filter components, and residual impurities will gradually accumulate, causing flow channel blockage. This application extends the execution time of the backwashing system when the real-time temperature is below a preset low-temperature threshold, enhancing the rinsing efficiency for high-viscosity residues.

[0028] In some embodiments, the control unit is further configured to: Before performing the flow coefficient K value calibration process, calculate the fertilizer solution density change rate measured by the density measurement component and the real-time temperature change rate measured by the temperature sensor between the current sampling period and the previous sampling period; when the density change rate exceeds the preset density change rate threshold, or the real-time temperature is lower than the preset low temperature threshold, set the N value to the first preset number. When, within a consecutive preset number of density measurement cycles, the absolute value of the fluctuation of the real-time flow coefficient K value and the historical moving average value of K value calculated in each cycle is less than a preset fluctuation threshold, and the density change rate is lower than the preset density change rate threshold and the real-time temperature change rate is lower than the preset temperature change rate threshold, the N value is set as a second preset number; wherein the first preset number is greater than the second preset number; The slope of change is calculated based on the historical sequence of K values, and the current N value is corrected based on the comparison between the absolute value of the slope of change and a preset slope threshold: when the absolute value of the slope of change is greater than the first preset slope threshold, the current N value is reduced by a preset adjustment amount to increase the execution frequency of flow coefficient K value calibration; when the absolute value of the slope of change is less than the second preset slope threshold, the current N value is increased by a preset adjustment amount to reduce the execution frequency of flow coefficient K value calibration. The corrected N value is constrained between the second preset number and the first preset number, and the historical moving average of the K value is calculated based on the K value of a preset number of historical valid calibration periods.

[0029] Specifically, a fixed N value cannot adapt to changes in fertilizer solution conditions and the trend of K value itself. If the N value is fixed too small, K value calibration will be too frequent, increasing equipment operating wear and tear and potentially interfering with the continuity of fertilization operations. If the N value is fixed too large, when the fertilizer solution density change rate exceeds the standard or the real-time temperature is too low, it is easy to cause fluctuations in fertilizer solution characteristics, leading to K value deviation or a large slope of K value change. If calibration is not timely, K value deviation will accumulate, which will lead to a decrease in the volumetric measurement accuracy of the impeller flowmeter, affecting the accuracy of the corrected volume and fertilizer quality calculation, and failing to meet the measurement requirements of precision fertilization. This application combines the fertilizer solution density change rate and real-time temperature change rate to determine the stability of the operating conditions. When the operating conditions are unstable, a larger first preset number is used to ensure sufficient sampling and accurate results for K value calibration. When the operating conditions are stable, a smaller second preset number is used to reduce the calibration frequency and reduce equipment wear. The calibration frequency is further adapted by the historical change slope of the K value. When the K value changes rapidly, the calibration frequency is increased, and when the change is gradual, the calibration frequency is decreased, thus constraining the N value within a reasonable range. This avoids the drawbacks of fixing the N value and achieves the matching of calibration frequency with changes in operating conditions and the trend of the K value.

[0030] In some embodiments, the control unit is further configured to: When fertilization is started or a fertilizer solution replacement signal is detected, the current fertilizer solution is matched with a preset fertilizer solution type feature library by a pre-set clustering algorithm based on the fertilizer solution density data sequence measured by the density measurement component and the temperature data sequence measured by the temperature sensor within multiple consecutive sampling periods, thereby identifying the current fertilizer solution type; the fertilizer solution type feature library includes urea solution, compound fertilizer solution and liquid formula fertilizer. Based on the identified fertilizer solution type, perform the following operations: During the database retrieval process, the retrieval scope is limited to the flow correction coefficient sub-library corresponding to the fertilizer type to improve the accuracy and efficiency of density range retrieval. During the temperature compensation process, the density value is compensated by calling the temperature compensation curve sub-liquid library that matches the fertilizer solution type. Configure the initial setting of the N value as a preset baseline value associated with the fertilizer type.

[0031] Specifically, different types of fertilizer solutions exhibit varying density-temperature characteristics and flow response patterns. Without differentiation, a unified search of the entire flow correction coefficient library would increase the search volume. This solution, upon initiation of fertilization or replacement of the fertilizer solution, uses a clustering algorithm combined with continuously sampled density and temperature data sequences to match and identify the current fertilizer solution type against a pre-defined fertilizer solution type feature library, distinguishing between urea solutions and compound fertilizer solutions. Based on the identification results, adaptation operations are performed: limiting the search range of the corresponding type's flow correction coefficient sub-library to reduce search redundancy and improve search accuracy and efficiency; calling the matching temperature compensation curve sub-library to make density compensation more closely match the density-temperature characteristics of the current fertilizer solution, reducing compensation errors; and initially setting the N value as a benchmark value associated with the fertilizer solution type to make the initial parameters for K value calibration more reasonable, improving the accuracy of fertilizer quality measurement.

[0032] In some embodiments, the preset clustering algorithm is the K-means clustering algorithm; the cluster centers of the K-means clustering algorithm are preset to be the mean of the standard temperature and density feature vectors of each type of fertilizer solution in the fertilizer solution type feature library.

[0033] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0034] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0035] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0036] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A fertilizer application quality measuring device for use in intelligent fertilizer applicators, characterized in that, include: Fertilizer suction passage; The fertilizer absorption passage is used to connect the fertilizer solution storage container and the fertilizer applicator; Filtering components; The filter assembly is disposed on the fertilizer absorption passage and is used to filter the fertilizer solution flowing through it; Impeller flow meter; the impeller flow meter is installed on the fertilizer suction passage and is used to obtain the volume of fertilizer solution flowing through the fertilizer suction passage; A density measurement component, connected to the fertilizer absorption pathway, is used to collect fertilizer solution samples and measure the density of the fertilizer solution. Control unit; the control unit is electrically connected to both the impeller flow meter and the density measurement assembly; the control unit is configured as follows: Start the fertilizer suction operation and use an impeller flow meter to measure the volume of fertilizer solution flowing through it, which is recorded as the first volume; Obtain the fertilizer solution density measured by the density measurement component; The corrected volume is obtained by correcting the first volume based on the currently measured fertilizer solution density; The fertilization quality for the current sampling period is obtained based on the corrected volume and the currently measured fertilizer solution density.

2. The metering device according to claim 1, characterized in that, The density measurement component includes: A fixed container; the top of the fixed container is provided with a drain hole; A weighing sensor; the fixed container is mounted on the weighing sensor; the weighing sensor is used to measure the weight of the fixed container and the fertilizer solution inside it; A storage tank; the storage tank is located below the fixed container and is used to receive the fertilizer solution overflowing from the drain hole and the fertilizer solution discharged from the fixed container after the measurement is completed; Liquid level measuring plate; the liquid level measuring plate is installed inside the liquid storage tank and is used to monitor the liquid level and electrical conductivity of the fertilizer solution in the liquid storage tank; The liquid inlet branch connects the fertilizer absorption passage to the fixed container and is used to inject liquid into the fixed container; A reflux branch connects the liquid storage tank to the fertilizer absorption passage, and a reflux valve is provided on the branch. The control unit is also configured to: Control the opening of the inlet branch to allow the fertilizer solution to enter the fixed container; When the liquid level in the storage tank is detected to be increasing by the liquid level measuring plate, it is determined that the fertilizer solution in the fixed container has overflowed from the drain hole and reached the preset fixed volume. The weighing sensor is then triggered to obtain the weight of the fertilizer solution in the fixed container and calculate the density in combination with the preset fixed volume of the fixed container. After the density calculation is completed, the fertilizer solution in the fixed container is discharged into the storage tank and the reflux valve is opened. The negative pressure generated by the fertilizer applicator is used to draw the fertilizer solution in the storage tank back to the fertilizer absorption passage.

3. The metering device according to claim 2, characterized in that, The control unit is also configured to: During the process of controlling the opening of the reflux valve to draw back the liquid, the liquid level in the storage tank is monitored by the liquid level measuring plate. When the liquid level is detected to drop to the preset safety lower limit, the reflux valve is closed to prevent air from entering the fertilizer absorption passage through the storage tank.

4. The metering device according to claim 3, characterized in that, The filter assembly is equipped with a backwashing system; the backwashing system includes: A drain valve is located on the front side of the liquid inlet end of the filter assembly and leads to the drain tank; A backwash passage is connected to an external pressurized water source and the rear side of the liquid outlet of the filter assembly. A backwash valve is provided on the passage. A fertilizer suction valve is located downstream of the filter assembly on the fertilizer suction passage. The control unit is configured to perform a backwashing mode: close the fertilizer suction valve, open the backwash valve and the drain valve, use external pressurized water to backwash the filter assembly and discharge the wastewater through the drain valve.

5. The metering device according to claim 4, characterized in that, The control unit is configured to: After obtaining the real-time density value measured by the density measurement component, the density interval in which the real-time density value is located is retrieved from the database, and the flow correction coefficients corresponding to the reference density values ​​at both ends of the density interval are obtained. Based on the flow correction coefficients at both ends of the interval, a linear interpolation algorithm is used to calculate the target flow correction coefficients that are suitable for the current fertilizer solution. The target flow correction coefficient is applied as a multiplier factor to the first volume to obtain the corrected volume, thereby eliminating the volume measurement error of the impeller flowmeter caused by the change in fertilizer solution density.

6. The metering device according to claim 5, characterized in that, The control unit is also configured to: In N consecutive density measurement cycles, record the number of pulse signals output by the impeller flowmeter during each injection of liquid into the fixed container until overflow; N≥2; The total number of N pulse signals is accumulated, and the real-time flow coefficient K value of the impeller flow meter is calculated based on N times the preset fixed volume of the fixed container; The real-time flow coefficient K is set as the current volume conversion reference coefficient of the impeller flow meter; in subsequent sampling periods, the original pulse signal output by the impeller flow meter is converted into the first volume based on the volume conversion reference coefficient.

7. The metering device according to claim 6, characterized in that, The metering device also includes a temperature sensor; the temperature sensor is used to collect the temperature of the fertilizer solution in real time. The control unit is also configured to: Obtain the temperature of the fertilizer solution as measured by the temperature sensor; The density of the fertilizer solution is obtained by temperature compensation based on the weight measured by the weighing sensor and the density value calculated by the preset fixed volume of the fixed container, according to the temperature of the fertilizer solution. When the real-time temperature is lower than a preset low-temperature threshold, the control unit is also configured to extend the backwashing duration during the backwashing process.

8. The metering device according to claim 7, characterized in that, The control unit is also configured to: Before performing the flow coefficient K value calibration process, calculate the fertilizer solution density change rate measured by the density measurement component and the real-time temperature change rate measured by the temperature sensor between the current sampling period and the previous sampling period; when the density change rate exceeds the preset density change rate threshold, or the real-time temperature is lower than the preset low temperature threshold, set the N value to the first preset number. When, within a consecutive preset number of density measurement cycles, the absolute value of the fluctuation of the real-time flow coefficient K value and the historical moving average value of K value calculated in each cycle is less than a preset fluctuation threshold, and the density change rate is lower than the preset density change rate threshold and the real-time temperature change rate is lower than the preset temperature change rate threshold, the N value is set as a second preset number; wherein the first preset number is greater than the second preset number. The slope of change is calculated based on the historical sequence of K values, and the current N value is corrected based on the comparison between the absolute value of the slope of change and a preset slope threshold: when the absolute value of the slope of change is greater than the first preset slope threshold, the current N value is reduced by a preset adjustment amount to increase the execution frequency of flow coefficient K value calibration; when the absolute value of the slope of change is less than the second preset slope threshold, the current N value is increased by a preset adjustment amount to reduce the execution frequency of flow coefficient K value calibration. The corrected N value is constrained between the second preset number and the first preset number, and the historical moving average of the K value is calculated based on the K value of a preset number of historical valid calibration periods.

9. The metering device according to claim 8, characterized in that, The control unit is also configured to: When fertilization is initiated or a fertilizer solution replacement signal is detected, the current fertilizer solution type is identified by matching it with a preset fertilizer solution type feature library using a pre-set clustering algorithm. The fertilizer solution type feature library includes urea solution, compound fertilizer solution, and liquid formula fertilizer. Based on the identified fertilizer solution type, perform the following operations: During the database retrieval process, the retrieval scope is limited to the sub-liquidity of the flow correction coefficient corresponding to the fertilizer type to improve the accuracy and efficiency of density range retrieval. During the temperature compensation process, the density value is compensated by calling the temperature compensation curve sub-liquid library that matches the fertilizer solution type. Configure the initial setting of the N value as a preset baseline value associated with the fertilizer type.

10. The metering device according to claim 9, characterized in that, The preset clustering algorithm is the K-means clustering algorithm.

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