A precise control device for fertilizer injection and mixing and a working method thereof

Abstract

The present invention relates to a precise control device for fertilizer injection and mixing and a working method. The device comprises a fertilizer injection unit and a fertilizer mixing unit. The fertilizer injection unit comprises an irrigation branch and a fertilizer injection branch. The irrigation branch delivers water required for irrigation to an inlet of a static mixer through a pipeline. The fertilizer injection branch delivers fertilizer to the inlet of the static mixer through a pipeline. The fertilizer mixing unit comprises a static mixer, a premixing tank, a buffer tank and a water-fertilizer pump connected in sequence through pipelines. The static mixer, the premixing tank and the buffer tank are provided with an EC sensor and a pH sensor. The premixing tank and the buffer tank are provided with an agitator. The water-fertilizer concentration control unit is configured to: determine a duty cycle of a pulse width modulation solenoid valve according to the EC value and pH value of the water-fertilizer solution in the buffer tank to achieve regulation of the fertilizer injection amount; determine the uniformity of the fertilizer mixing according to the EC value, pH value and corresponding deviation rate of the water-fertilizer solution in the static mixer within a set time period, and regulate the operation of the agitator.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizer mixing, and in particular to a precise control device for fertilizer injection and mixing and a working method. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In the agricultural field, traditional extensive irrigation methods easily lead to problems such as waste of water resources, low fertilizer utilization, soil compaction and serious environmental pollution. In addition, traditional irrigation and fertilization are labor-intensive, time-consuming and labor-intensive, and have low agricultural production efficiency.

[0004] Integrated water and fertilizer application technology is an agricultural technology that combines irrigation and fertilization to achieve precise control of irrigation water and fertilizer amounts. The use of this technology can reduce water resource waste and improve water utilization efficiency; improve fertilizer utilization and reduce environmental pollution; reduce labor intensity, improve agricultural production efficiency, and promote green agricultural development.

[0005] The current integrated water and fertilizer application technology generally adopts the Venturi principle to absorb fertilizer and manually control fertilization. The water and fertilizer control accuracy is poor, and due to the lack of a fertilizer mixing link, the uniformity of water and fertilizer is difficult to ensure. In addition, due to the lack of an adaptive feedback unit, the degree of intelligence is low. Summary of the Invention

[0006] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a precise control device and working method for fertilizer injection and mixing, which starts from the two operation links of fertilizer injection and fertilizer mixing to realize adaptive control of water and fertilizer concentration, improve water and fertilizer utilization rate, reduce environmental pollution, and promote green development of agriculture.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A first aspect of the present invention provides a precise control device for fertilizer injection and mixing, comprising a fertilizer injection unit and a fertilizer mixing unit, wherein the fertilizer injection unit comprises an irrigation branch and a fertilizer injection branch;

[0009] Irrigation branch, which delivers the water required for irrigation to the inlet of the static mixer through a pipeline, and the pipeline is equipped with a flow meter and an irrigation pump;

[0010] A fertilizer injection branch, which delivers fertilizer to the inlet of the static mixer through a pipeline, and a flow meter and a pulse width modulation solenoid valve are provided on the pipeline;

[0011] The fertilizer mixing unit includes a static mixer, a premixing tank, a buffer tank and a water-fertilizer pump connected in sequence through pipelines. The static mixer, premixing tank and buffer tank are equipped with EC sensors and pH sensors, and the premixing tank and buffer tank are equipped with a stirrer;

[0012] The water and fertilizer concentration control unit is configured to: determine the duty cycle of the pulse width modulation solenoid valve according to the EC value and pH value of the water and fertilizer solution in the buffer tank, so as to achieve the regulation of the fertilizer injection amount;

[0013] The water-fertilizer concentration control unit is also configured to determine the uniformity of the mixed fertilizer and regulate the operation of the agitator based on the EC value, pH value and corresponding deviation rate of the water-fertilizer solution in the buffer tank within a set time period.

[0014] Furthermore, according to the EC value, pH value and corresponding deviation rate of the water-fertilizer solution in the buffer tank within the set time period, the uniformity of the mixed fertilizer is determined and the operation of the agitator is regulated, specifically:

[0015] EC and pH values ​​were collected twice within a given time period and recorded as EC n 、EC n+1 and pH n , pH n+1 , determine the deviation rate δ, as shown in the following formula:

[0016] δ EC =(EC n+1 -EC n ) / EC n ,δ pH =(pH n+1 -pH n ) / pH n ;

[0017] Among them, δ EC is the EC value deviation rate, δ pH is the pH deviation rate;

[0018] When δ EC ≤5%, and δ pH When the content is ≤5%, the uniformity of the mixed fertilizer meets the requirements;

[0019] When δ EC >5%, and δ pH When the value is greater than 5%, the uniformity of the mixed fertilizer does not meet the requirements, and the operating frequency of the variable frequency motor corresponding to the agitator should be increased.

[0020] Furthermore, the water and fertilizer concentration control unit is configured to determine the operating frequency of the irrigation pump based on the deviation between the average monitored flow rate and the target flow rate within the current set time period of the irrigation branch, thereby achieving regulation of the irrigation amount.

[0021] Furthermore, the water-fertilizer concentration control unit is also configured to control the state of the switch valve between the premixing tank and the buffer tank in the fertilizer mixing unit according to the change of the liquid level in the buffer tank.

[0022] Furthermore, the water and fertilizer concentration control unit is also configured to control the operating frequency of the irrigation pump according to the change of the liquid level in the premix tank.

[0023] Furthermore, the irrigation branch includes a water tank, an irrigation pump, a switch valve, a flow meter and a check valve connected in sequence through pipes. The other end of the check valve is connected to the inlet of the static mixer through a pipe. A pressure transmitter is provided on the pipe between the switch valve and the electromagnetic flowmeter.

[0024] Furthermore, the fertilizer injection branch has at least one group, and multiple groups of fertilizer injection branches are arranged in parallel, and the outlet pipes of all fertilizer injection branches are connected to the inlet of the static mixer.

[0025] Furthermore, the fertilizer injection branch includes a fertilizer barrel, a fertilizer injection pump, a filter, a pulse width modulation solenoid valve and a flow meter connected in sequence through pipes. The other end of the flow meter is connected to the inlet of the static mixer through a pipe. A pressure transmitter is provided on the pipe between the pulse width modulation solenoid valve and the flow meter.

[0026] Furthermore, the static mixer includes a first-stage static mixer and a second-stage static mixer connected in series, the first-stage static mixer is an SK type static mixer, and the second-stage static mixer is an SV type static mixer.

[0027] A second aspect of the present invention provides a working method of a device for precise control of fertilizer injection and mixing, comprising the following steps:

[0028] The irrigation pump, fertilizer injection pump and water-fertilizer pump are started, and the operating frequency of the irrigation pump and fertilizer injection pump is adjusted according to the predetermined irrigation amount and water-fertilizer concentration target value;

[0029] Obtain the pressure and flow of the irrigation branch of the fertilization unit, the pressure and flow of the fertilizer injection branch, and the EC value and pH value of the fertilizer mixing unit, and compare them with the target values ​​to achieve regulation of irrigation amount, fertilizer injection amount and fertilizer mixing uniformity, as well as liquid level regulation in the premixing tank and buffer tank.

[0030] Compared with the existing technology, one or more of the above technical solutions have the following beneficial effects:

[0031] 1. The two processes of fertilizer injection and fertilizer mixing are comprehensively considered to ensure that the fertilizer is injected into the static mixer and mixed with the irrigation water to form a sufficiently uniform water-fertilizer solution. It then passes through the premixing tank and buffer tank for subsequent fertilization operations, thereby improving the utilization rate of irrigation water and fertilizer, reducing environmental pollution, reducing labor intensity, and improving agricultural production efficiency.

[0032] 2. Focusing on the two operational stages of fertilizer injection and mixing, the system intelligently and precisely controls irrigation volume, fertilizer injection volume, fertilizer mixing uniformity, and the liquid levels in the premix and buffer tanks in real time based on dynamic changes in monitoring information from the injection and mixing units during integrated fertilization, thereby improving fertilizer utilization and application uniformity. This highly intelligent device, with a simple structure and easy operation, is readily applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1 This is a schematic structural diagram of a fertilizer injection and mixing control device provided by one or more embodiments of the present invention;

[0035] Figure 2 It is a schematic diagram of the fertilizer injection and mixing control process provided by one or more embodiments of the present invention.

[0036] In the figure, 1-water tank; 2-irrigation pump; 3-on / off valve 1; 4-pressure transmitter 1; 5-electromagnetic flowmeter; 6-check valve; 7-fertilizer barrel 1; 8-fertilizer injection pump 1; 9-filter 1; 10-pulse width modulation solenoid valve 1; 11-pressure transmitter 2; 12-flowmeter 1; 13-fertilizer barrel 2; 14-fertilizer injection pump 2; 15-filter 2; 16-pulse width modulation solenoid valve 2; 17-pressure transmitter 3; 18-flowmeter 2; 19-first-stage static mixer; 20-second-stage static mixer; 21-premixing tank; 22-on / off valve 2; 23-buffer tank; 24-water and fertilizer pump. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0039] The following examples provide a precise control device and method for fertilizer injection and mixing. By automatically acquiring real-time information such as irrigation volume, fertilizer injection volume, and water-fertilizer concentration during integrated water-fertilizer application, the device intelligently adjusts irrigation volume, fertilizer injection volume, fertilizer mixing uniformity, and the liquid levels in the premixing and buffer tanks based on dynamic changes in this information, achieving precise control of fertilizer concentration and mixing uniformity. This device is highly intelligent, simple in structure, and easy to operate, making it suitable for widespread application.

[0040] Example 1:

[0041] like Figure 1 As shown, a precise control device for fertilizer injection and mixing includes a fertilizer injection unit and a fertilizer mixing unit, wherein the fertilizer injection unit includes an irrigation branch and a fertilizer injection branch.

[0042] The irrigation branch includes a water tank 1, an irrigation pump 2, a switch valve 3, an electromagnetic flowmeter 5, and a check valve 6, which are connected in sequence through pipes. The other end of the check valve 6 is connected to the inlet of the static mixer through a pipe. A pressure transmitter 4 is provided on the pipe between the switch valve 3 and the electromagnetic flowmeter 5.

[0043] The fertilizer injection branch in this embodiment has two groups of fertilizer injection branches arranged in parallel. It can be understood that there can be multiple groups of fertilizer injection branches in actual applications. This embodiment takes two groups of fertilizer injection branches as an example to explain this solution. The two groups of fertilizer injection branches have the same structure, specifically: the fertilizer injection branch includes a fertilizer barrel 7 (13), a fertilizer injection pump 8 (14), a filter 9 (15), a pulse width modulation solenoid valve 10 (16) and a flow meter 12 (18) connected in sequence through pipelines. The other end of the flow meter 12 (18) is connected to the inlet of the static mixer through a pipeline. A pressure transmitter 11 (17) is provided on the pipeline between the pulse width modulation solenoid valve 10 (16) and the flow meter 12 (18).

[0044] The fertilizer mixing unit includes a static mixer, a premixing tank 21, a switch valve 22, a buffer tank 23 and a water-fertilizer pump 24 connected in sequence by pipelines. The buffer tank is provided with an EC sensor (conductivity sensor), a pH sensor and a liquid level meter. The outlet of the water-fertilizer pump 24 is used to connect to the existing irrigation network. The static mixer includes a first-stage static mixer 19 and a second-stage static mixer 20 connected in series.

[0045] A static mixer is a highly efficient mixing device with no moving parts. Its working mechanism is to use a mixing unit fixed in the tube to change the flow state of the fluid in the tube to achieve good dispersion and sufficient mixing between different fluids.

[0046] The first-stage static mixer in this embodiment adopts an SK type static mixer, which is welded by single-channel left and right twisted spiral plates to achieve rough mixing of water and fertilizer.

[0047] The secondary static mixer in this embodiment adopts an SV type static mixer, which is assembled from corrugated plates to achieve fine mixing of water and fertilizer.

[0048] In order to further achieve uniform mixing of water and fertilizer, a premixing tank 21 and a buffer tank 23 are respectively set after the secondary static mixer, and the two tanks are equipped with agitators driven by variable frequency motors.

[0049] It also has a water and fertilizer concentration control unit, including a water and fertilizer concentration controller and a touch screen, which is used to perform automatic control based on the EC value (electrical conductivity), pH value in the fertilizer mixing unit, and the water and fertilizer liquid levels in the premixing tank and buffer tank, and the pressure and flow obtained in the fertilizer injection branch and the irrigation branch.

[0050] In this embodiment, the values ​​characterizing fertilizer concentration include the EC value, which measures the soluble salt concentration of the fertilizer, and the pH value, which measures the hydrogen ion concentration (acidity or alkalinity) of the fertilizer. The EC sensor measures the soluble salt concentration in the fertilizer solution, while the pH sensor measures the pH of the fertilizer solution. The requirements for the soluble salt concentration and pH of fertilizer solutions for crops are: 1 < EC ≤ 4 mS / cm, 5 ≤ pH ≤ 8.

[0051] In this embodiment, the water-fertilizer concentration controller uses an STM32 microcontroller and interacts with a capacitive serial touchscreen via an RS232 interface. The controller monitors the parameters of the pressure transmitter and electromagnetic flowmeter in the irrigation branch of the fertilizer injection unit, the pressure transmitter and flowmeter in the fertilizer injection branch of the fertilizer injection unit, and the EC sensor, pH sensor, and liquid level gauge in the fertilizer mixing unit in real time. The controller compares these sensor parameters with the target water-fertilizer concentration and achieves adaptive regulation of the water-fertilizer concentration by adjusting the operating frequency of the irrigation pump and the duty cycle of the solenoid valve in the fertilizer injection branch.

[0052] The controller uses an STM32F103VET6 single-chip microcomputer, which interacts with the capacitive serial touch screen through the RS232 interface to receive sensor measurement data and display the working status and parameter settings of the integrated water and fertilizer application.

[0053] This embodiment automatically acquires real-time information, including irrigation volume, fertilizer injection volume, and water-fertilizer concentration indicators, during the integrated water-fertilizer application process, focusing on the two operations of fertilizer injection and mixing. Based on the dynamic changes in this information, it intelligently adjusts the water-fertilizer concentration in real time. Simultaneously, it adds a fertilizer mixing operation to achieve precise control and uniformity of water-fertilizer concentration. This device is highly intelligent, simple in structure, and easy to operate, making it easy to promote and apply.

[0054] In this embodiment, pulse width modulation solenoid valves 10 and 16 can control their on / off states through pulse width modulation (PWM) technology, thereby achieving precise flow control. PWM technology adjusts the solenoid valve's on / off time by varying the pulse duty cycle. The duty cycle ranges from 0% to 100%, corresponding to the solenoid valve switching from fully closed to fully open.

[0055] In this embodiment, flow meters 5, 12, and 18 are all electromagnetic flow meters. The electromagnetic flow meter 5 monitors the flow value of the irrigation branch in real time, compares it with the irrigation amount set on the touch screen, and adjusts the operating frequency of the irrigation pump to achieve irrigation flow control. Specifically, when the average monitored flow rate within a set time period is less than the set irrigation flow rate, the operating frequency of the irrigation pump is increased by a frequency increment δ f The frequency is 2% of the current operating frequency. When the monitored flow rate exceeds the set irrigation flow rate, the irrigation pump's operating frequency is reduced by 2% of the current operating frequency. After each frequency change, the average monitored flow rate over the set time period is measured and compared with the set flow rate. The decision to continue adjusting the frequency is made until the average monitored flow rate after the frequency change is equal to or close to the set irrigation flow rate (for example, the rate of change is less than 5%).

[0056] Precise control of fertilizer injection volume: The EC and pH values ​​of the water-fertilizer solution are monitored in real time using the EC sensor and pH sensor in the buffer tank. These values ​​are compared with the EC and pH values ​​corresponding to the fertilizer injection volume set on the touch screen. The fertilizer injection volume is then regulated by adjusting the duty cycle of the pulse-width modulation solenoid valve. Specifically, when the monitored EC and pH values ​​of the water-fertilizer solution are less than the set values, the duty cycle of the pulse-width modulation solenoid valve is increased. When the monitored EC and pH values ​​of the water-fertilizer solution are greater than the set values, the duty cycle of the pulse-width modulation solenoid valve is decreased. Furthermore, a mathematical model is first constructed between the pulse-width modulation solenoid valve flow rate Q and the duty cycle DC. Based on this mathematical model, the solenoid valve duty cycle corresponding to the target fertilizer injection volume is determined.

[0057] During fertilization, since the irrigation volume is significantly greater than the fertilizer injection volume, and the solenoid valve allows a relatively small flow rate, regulating the irrigation volume is not practical. Consequently, the fertilizer injection volume is significantly smaller than the irrigation volume, and adjusting the fertilizer injection pump's operating frequency to achieve the desired accuracy is difficult. While irrigation volume regulation can be achieved by adjusting the valve, the internal structure of the valve limits the accuracy. Therefore, in this embodiment, the irrigation volume is regulated by adjusting the irrigation pump's speed, while the fertilizer injection volume is regulated by adjusting the solenoid valve's duty cycle.

[0058] The mathematical model between the pulse width modulation solenoid valve flow Q and the duty cycle DC is:

[0059] Q DC =k×DC+A;

[0060] Where Q DC is the flow rate corresponding to the duty cycle, k is the proportional coefficient, A is a constant, and DC is the duty cycle. Generally speaking, the DC value is 20%-80%. Duty cycles below 20% and above 80% are not recommended because the solenoid valve opening time is too short or too long, and the solenoid valve's own response time causes the flow rate and duty cycle to be non-linear.

[0061] Judgment and control of fertilizer mixing uniformity: EC value and pH value of the water-fertilizer solution in the buffer tank are collected twice within a given time period and recorded as EC n 、EC n+1 and pH n , pH n+1 , given a time period of 1 minute, the calculation formula for the deviation rate δ is:

[0062] δ EC =(EC n+1 -EC n ) / EC n , δ pH =(pH n+1 -pH n ) / pH n ;

[0063] When δ EC ≤5%, and δ pH When the value is ≤5%, the uniformity of the mixed fertilizer is judged to meet the requirements;

[0064] When δ EC >5%, and δ pH When the concentration of water and fertilizer is greater than 5%, it is determined that the uniformity of the mixed fertilizer does not meet the requirements, and the water and fertilizer concentration controller increases the operating frequency of the mixer variable frequency motor.

[0065] The coefficient of variation can also be used to determine the uniformity of the fertilizer mixture: collect EC and pH values ​​n times within a given time period and calculate the standard deviation σ, as shown in the following formula:

[0066]

[0067] Among them, n is the number of collected data, x i is the i-th measurement value, is the average value of n collected data.

[0068] Coefficient of variation c v When ≤5%, the uniformity of the mixed fertilizer is considered to meet the requirements.

[0069] Premix and buffer tank level control: When the buffer tank level exceeds a specified level, the water-fertilizer concentration controller closes the on-off valve in the fertilizer mixing unit. When the buffer tank level falls below a specified level, the water-fertilizer concentration controller opens the on-off valve in the fertilizer mixing unit. Similarly, when the premix tank level exceeds a specified level, the water-fertilizer concentration controller reduces the operating frequency of the irrigation pump. When the premix tank level falls below a specified level, the water-fertilizer concentration controller increases the operating frequency of the irrigation pump.

[0070] The working principle of the above device is:

[0071] During the water and fertilizer application process, the irrigation amount and water and fertilizer concentration target value are input through the touch screen of the water and fertilizer concentration control unit. The device intelligently matches the operating efficiency of the irrigation pump in the irrigation branch and the duty cycle of the pulse width modulation solenoid valve according to the target value. The water and fertilizer concentration control unit collects the pressure and flow in the irrigation branch, the pressure and flow in the fertilizer injection branch, and the EC value and pH value representing the water and fertilizer concentration in the fertilizer mixing unit in real time, and compares them with the target value. If there is a deviation between the measured value and the target value, the water and fertilizer concentration is adaptively adjusted by adjusting the operating frequency of the irrigation pump in the irrigation branch and the duty cycle of the pulse width modulation solenoid valve in the fertilizer injection branch.

[0072] The fertilizer mixing unit is equipped with a two-stage static mixer, a premixing pipe and a buffer tank. The uniformity of the fertilizer mixture is judged based on the deviation rate of the EC value and pH value collected twice within a given time period. The speed of the variable frequency motor of the agitator in the premixing tank and the buffer tank is adjusted to achieve adaptive and uniform fertilizer mixing. Based on the liquid level in the buffer tank, the opening and closing of the switch valve between the buffer tank and the premixing tank are intelligently decided. Also based on the liquid level in the premixing tank, the operating frequency of the irrigation pump is intelligently adjusted.

[0073] Focusing on the two operational steps of fertilizer injection and mixing, the system intelligently and precisely controls irrigation volume, fertilizer injection volume, fertilizer mixing uniformity, and the liquid levels in the premixing and buffer tanks in real time based on dynamic changes in monitoring information from the injection and mixing units during integrated fertilization, thereby improving fertilizer utilization and application uniformity. This highly intelligent device, with a simple structure and easy operation, is readily applicable and readily adaptable.

[0074] Example 2:

[0075] A method for accurately controlling a device for injecting and mixing fertilizers, comprising the following steps:

[0076] The irrigation pump, fertilizer injection pump and water-fertilizer pump are started, and the operating frequency of the irrigation pump and fertilizer injection pump is adjusted according to the predetermined irrigation amount and water-fertilizer concentration target value;

[0077] Obtain the pressure and flow of the irrigation branch of the fertilization unit, the pressure and flow of the fertilizer injection branch, and the EC value and pH value of the fertilizer mixing unit, and compare them with the target values ​​to achieve regulation of irrigation amount, fertilizer injection amount and fertilizer mixing uniformity, as well as liquid level regulation in the premixing tank and buffer tank.

[0078] Figure 2The following is a flowchart of the precise fertilizer injection and mixing control process. After the water-fertilizer concentration controller is powered on and reset, the system initializes the CAN bus communication interface and enters the main operating parameter setting interface. After completing the operating parameter settings, press the "Water and Fertilizer Application" button to begin the integrated water and fertilizer application process. The irrigation pump, fertilizer injection pump, and water-fertilizer pump are turned on, and their operating frequencies are automatically adjusted according to the irrigation volume and water-fertilizer concentration target values ​​entered in the operating parameters. The controller collects real-time pressure and flow from the irrigation branch of the fertilizer injection unit, the pressure and flow from the fertilizer injection branch, and the EC and pH values ​​of the fertilizer mixing unit. The controller compares the collected measurements with the target values ​​and sends the corresponding control parameters and instructions to the execution unit, achieving precise control of the irrigation volume, fertilizer injection volume, fertilizer mixing uniformity, and the liquid levels in the premix tank and buffer tank.

[0079] The specific adjustment process is as follows:

[0080] When the flow measurement value in the irrigation branch is inconsistent with the target value, the operating frequency of the irrigation pump is adjusted;

[0081] When the measured value of the fertilizer injection amount is inconsistent with the target value, the duty cycle of the pulse width modulation solenoid valve in the fertilizer injection branch is adjusted to achieve precise control of the fertilizer injection amount;

[0082] When the uniformity of the mixed fertilizer does not meet the requirements, adjust the operating frequency of the frequency conversion motor of the agitator in the premixing tank and buffer tank;

[0083] When the liquid level in the buffer tank exceeds or falls below the limit value, the switch valve of the fertilizer mixing unit is opened or closed; when the liquid level in the premix tank exceeds or falls below the limit value, the operating frequency of the irrigation pump is adjusted.

[0084] The above process is repeated until the integrated water and fertilizer application operation is completed.

[0085] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A precise control device for fertilizer injection and mixing, characterized in that: It includes a fertilizer injection unit and a fertilizer mixing unit. The fertilizer injection unit includes an irrigation branch and a fertilizer injection branch; An irrigation branch, which delivers irrigation water to the inlet of a static mixer via a pipeline, with a flow meter and an irrigation pump provided on the pipeline. The static mixer comprises a primary static mixer and a secondary static mixer connected in series. The irrigation branch comprises a water storage tank, an irrigation pump, an on-off valve, a flow meter, and a check valve, which are sequentially connected via pipelines. The other end of the check valve is connected to the inlet of the static mixer via a pipeline. A pressure transmitter is provided on the pipeline between the on-off valve and the electromagnetic flow meter. A fertilizer injection branch delivers fertilizer to the inlet of the static mixer through a pipeline, and a flow meter and a pulse width modulation solenoid valve are provided on the pipeline; the pulse width modulation solenoid valve controls the on / off state of the solenoid valve using pulse width modulation technology; the fertilizer injection branch comprises at least one group, and multiple groups of fertilizer injection branches are arranged in parallel, and the outlet pipes of all fertilizer injection branches are connected to the inlet of the static mixer; The fertilizer mixing unit includes a static mixer, a premixing tank, a buffer tank and a water-fertilizer pump connected in sequence through pipelines. The static mixer, premixing tank and buffer tank are equipped with EC sensors and pH sensors, and the premixing tank and buffer tank are equipped with a stirrer; The water and fertilizer concentration control unit is configured to: determine the duty cycle of the pulse width modulation solenoid valve according to the EC value and pH value of the water and fertilizer solution in the buffer tank, so as to achieve the regulation of the fertilizer injection amount; The water-fertilizer concentration control unit is also configured to determine the uniformity of the mixed fertilizer and regulate the operation of the agitator based on the EC value, pH value and corresponding deviation rate of the water-fertilizer solution in the buffer tank within a set time period.

2. A precise control device for fertilizer injection and mixing according to claim 1, characterized in that: According to the EC value, pH value and corresponding deviation rate of the water-fertilizer solution in the buffer tank within the set time period, the uniformity of the mixed fertilizer is determined and the operation of the agitator is regulated. Specifically: EC and pH values ​​were collected twice within a given time period and recorded as EC n 、EC n+1 and pH n , pH n+1 , determine the deviation rate δ, as shown in the following formula: δ EC =(EC n+1 -EC n ) / EC n ,δ pH =(pH n +1-pH n ) / pH n ; Among them, δ EC is the EC value deviation rate, δ pH is the pH deviation rate; When δEC≤5% and δpH≤5%, the uniformity of the mixed fertilizer meets the requirements; When δEC>5% and δpH>5%, the uniformity of the mixed fertilizer does not meet the requirements, and the operating frequency of the variable frequency motor corresponding to the agitator is increased.

3. A precise control device for fertilizer injection and mixing according to claim 1, characterized in that: The water and fertilizer concentration control unit is configured to determine the operating frequency of the irrigation pump based on the deviation between the average monitored flow rate and the target flow rate within the current set time period of the irrigation branch, thereby achieving regulation of the irrigation amount.

4. A precise control device for fertilizer injection and mixing according to claim 1, characterized in that: The water-fertilizer concentration control unit is further configured to control the state of the switch valve between the premixing tank and the buffer tank in the fertilizer mixing unit according to the change of the liquid level in the buffer tank.

5. A precise control device for fertilizer injection and mixing according to claim 1, characterized in that: The water and fertilizer concentration control unit is further configured to control the operating frequency of the irrigation pump according to the change of the liquid level in the premix tank.

6. A precise control device for fertilizer injection and mixing according to claim 1, characterized in that: The fertilizer injection branch includes a fertilizer barrel, a fertilizer injection pump, a filter, a pulse width modulation solenoid valve and a flow meter connected in sequence through a pipeline. The other end of the flow meter is connected to the inlet of the static mixer through a pipeline. A pressure transmitter is provided on the pipeline between the pulse width modulation solenoid valve and the flow meter.

7. A precise control device for fertilizer injection and mixing according to claim 1, characterized in that: The first-stage static mixer is an SK-type static mixer, and the second-stage static mixer is an SV-type static mixer.

8. A working method based on the precise control device for fertilizer injection and mixing according to any one of claims 1 to 7, characterized in that: The following steps are involved: The irrigation pump, fertilizer injection pump and water-fertilizer pump are started, and the operating frequency of the irrigation pump and fertilizer injection pump is adjusted according to the predetermined irrigation amount and water-fertilizer concentration target value; Obtain the pressure and flow of the irrigation branch of the fertilization unit, the pressure and flow of the fertilizer injection branch, and the EC value and pH value of the fertilizer mixing unit, and compare them with the target values ​​to achieve regulation of irrigation amount, fertilizer injection amount and fertilizer mixing uniformity, as well as liquid level regulation in the premixing tank and buffer tank.

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