Water and fertilizer EC value quick adjusting system and control method

Abstract

The application provides a water and fertilizer EC value quick adjusting system and a control method, which comprises an irrigation system, a fertilizer injection system and a control system, the irrigation system is composed of an irrigation pump, a main pipe flowmeter, a main pipe, a water and fertilizer mixing cavity, a main pipe filter, a pressure sensor, a field electromagnetic valve and the like; and the fertilizer injection system is composed of a fertilizer injection pressure reducing valve, a main pipe EC sensor, a fertilizer injection pipe, a Venturi fertilizer suction device, a stirring motor, a fertilizer liquid barrel, a fertilizer suction flowmeter, a fertilizer suction electromagnetic valve, a fertilizer injection pump, a fertilizer injection pipe flowmeter, a fertilizer injection pipe EC sensor and the like. The fertilizer mother liquor EC value is obtained through the test of the flow duty cycle characteristic of the fertilizer suction electromagnetic valve and the pre-operation of the system, the relationship among the parameters is obtained in real time, the control program is greatly simplified, and the error is reduced; the fertilizer suction electromagnetic valve duty cycle is calculated through the real-time target value and the flow, the duty cycle is assigned in stages, the steady state is quickly reached, the duty cycle deviation of each operation is recorded, self-learning correction is carried out, and the adjustment is more accurate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of agricultural water and fertilizer integration, and particularly relates to a water and fertilizer EC value rapid adjustment system and a control method. BACKGROUND

[0002] In recent years, due to the advantages of water and fertilizer integration technology such as water saving, high irrigation uniformity, labor saving, fertilizer saving and yield increasing, the technology has developed rapidly in China and has been widely used. At present, the fertilization equipment in the water and fertilizer integration system mainly includes differential pressure type fertilization tank, high-pressure fertilization pump, Venturi fertilization device and hydraulic fertilization pump. These devices achieve the purpose of applying fertilizer into the pipeline, but cannot accurately control the concentration, EC and PH of the applied fertilizer, and cannot realize automatic control, which cannot meet the requirements of precise water and fertilizer integration. In order to solve this problem, automatic water and fertilizer integration machines are developed at home and abroad, which can accurately adjust water and fertilizer by a control system, mix fertilizer solution and water continuously and quantitatively into the irrigation pipeline, and realize high-precision fertilization.

[0003] When the existing water and fertilizer integration machine fertilizes, the PID control method is used to adjust the duty cycle of the fertilizer suction solenoid valve according to the set EC target value, so as to change the amount of fertilizer suction, and gradually reach the set EC value. However, the PID control method takes a long time to adjust, generally 1-2 minutes, which affects the precision of water and fertilizer application. Especially for water culture and substrate cultivation, the fertilization time is only a few minutes each time, so it is necessary to quickly reach the target value, and the shorter the adjustment time is, the better. In view of this problem, at present, incremental PID algorithm, fuzzy controller and neural network model are used to try to improve the response speed of the equipment. However, in the process of crop cultivation, the pressure, flow, mother liquor concentration, EC target value and type of fertilizer are constantly changing. These methods can only adapt to scenes where some parameters are relatively fixed, and cannot adapt to rapid response when parameters change. Therefore, a control method suitable for various scenes to realize rapid adjustment is needed. SUMMARY

[0004] The application provides a water and fertilizer EC value rapid adjustment system and a control method to solve the problem that multiple changing scenes in the existing water and fertilizer control system cannot respond quickly.

[0005] To achieve the above-mentioned purposes, the application adopts the following technical solutions:

[0006] In a first aspect, the application provides a water and fertilizer EC value rapid adjustment system, which comprises an irrigation system, a fertilizer injection system and a control system, wherein the control system is used to control the work of the irrigation system and the fertilizer injection system.

[0007] The irrigation system comprises an irrigation pump, a main pipe flow meter, a main pipe, a water-fertilizer mixing chamber and field electromagnetic valves; the irrigation pump, the main pipe flow meter and the water-fertilizer mixing chamber are sequentially connected through the main pipe, the irrigation pump is configured to input water into the main pipe, the water-fertilizer mixing chamber is configured to mix the water flowing into the main pipe and the fertilizer mother liquor input into the main pipe through a fertilizer injection system, and the water-fertilizer mixture output by the water-fertilizer mixing chamber is distributed to each field irrigation area through the field electromagnetic valves.

[0008] Optionally, the irrigation system further comprises a main pipe filter and a pressure sensor, which are sequentially installed between the water-fertilizer mixing chamber and the field electromagnetic valves.

[0009] Optionally, the fertilizer injection system comprises a fertilizer injection pressure reducing valve, a main pipe EC sensor, a fertilizer injection pipe, a Venturi fertilizer suction device, a fertilizer liquid tank, a fertilizer injection pump, a fertilizer injection pipe flow meter and a fertilizer injection pipe EC sensor.

[0010] The inlet and outlet of the fertilizer injection pipe are connected to the outlet and inlet of the water-fertilizer mixing chamber respectively; the fertilizer injection pressure reducing valve and the main pipe EC sensor are sequentially installed at the inlet of the fertilizer injection pipe; the middle section of the fertilizer injection pipe is communicated with a plurality of fertilizer suction pipes, each of which is provided with a corresponding Venturi fertilizer suction device and a fertilizer liquid tank; when the liquid in the fertilizer injection pipe flows through the Venturi fertilizer suction device, the Venturi fertilizer suction device sucks the fertilizer mother liquor in the fertilizer liquid tank and outputs the fertilizer mother liquor to the fertilizer injection pipe, and the sucked fertilizer mother liquor is sequentially input into the main pipe through the fertilizer injection pump, the fertilizer injection pipe flow meter and the fertilizer injection pipe EC sensor.

[0011] Optionally, the fertilizer injection system further comprises a stirring motor, a fertilizer suction flow meter and a fertilizer suction electromagnetic valve installed in each of the fertilizer suction pipes; the stirring motor is configured to stir the fertilizer mother liquor in the fertilizer liquid tank, and the fertilizer suction flow meter and the fertilizer suction electromagnetic valve are sequentially installed between the fertilizer liquid tank and the Venturi fertilizer suction device.

[0012] In a second aspect, the present application provides a control method for the water-fertilizer EC value rapid adjustment system of the first aspect, which comprises the following steps:

[0013] Step 1: determining the relationship between the fertilizer suction electromagnetic valve flow and the duty cycle;

[0014] Step 2: pre-operating the water-fertilizer EC value rapid adjustment system to measure the EC values of the fertilizer mother liquor in each of the fertilizer liquid tanks;

[0015] Step 3: according to the target EC value of the main pipe, the EC values of the fertilizer mother liquor and the relationship between the fertilizer suction electromagnetic valve flow and the duty cycle, calculating the duty cycles of the fertilizer suction electromagnetic valves in the steady state, and assigning different duty cycles to each of the fertilizer suction electromagnetic valves in stages;

[0016] Step 4: when the EC value of the main pipe collected by the main pipe EC sensor reaches a set proportion of the target EC value, starting the PID control, and controlling the operation of the fertilizer suction electromagnetic valves by the PWM controller according to the duty cycles.

[0017] Step 5: In the running stage, when the main EC value is stable in the set range, according to the difference between the calculated fertilizer suction solenoid duty ratio and the actual duty ratio, the duty ratio is corrected.

[0018] Optionally, the step 1 comprises:

[0019] The working pressure of the irrigation system is set, the irrigation pump and the fertilizer pump are started, and after the pressure is stable, the duty ratio of the fertilizer suction solenoid is set to take values in the range of 10-90% at intervals of 5%. The flow rate under each duty ratio value is measured by the fertilizer suction flow meter, and the relationship formula between the fertilizer suction solenoid flow rate and the duty ratio is obtained by data fitting: Qx = f(d), d = g(Qx); in the formula, Qx is the flow rate of the fertilizer suction solenoid, d is the duty ratio of the fertilizer suction solenoid, and f and g represent the relationship functions.

[0020] Optionally, the step 2 comprises:

[0021] The stirring motor of the fertilizer solution tank is started, the working pressure of the irrigation system is set, the irrigation pump is started, and after the pressure is stable, the fertilizer pump and one fertilizer suction solenoid are started. After the EC value Ef of the fertilizer pipeline is stable, the fertilizer suction flow rate Qx and the fertilizer pipeline flow rate Qf at this time are recorded; wherein the EC value of the fertilizer pipeline is measured by the fertilizer pipe EC sensor, the fertilizer suction flow rate Qx is measured by the fertilizer suction flow meter, and the fertilizer pipeline flow rate Qf is measured by the fertilizer pipe flow meter.

[0022] The EC value Em of the fertilizer mother liquor in the fertilizer solution tank is measured by the following formula: Em = Ef*Qf / Qx;

[0023] Each fertilizer suction solenoid is started in turn, and the EC value of the fertilizer mother liquor in each fertilizer solution tank is measured.

[0024] Optionally, the step 3 comprises:

[0025] For multiple fertilizer suction pipes that suction fertilizer at the same time, the following calculation is performed according to the set proportion of each fertilizer suction pipe:

[0026] Emz = (k1 / (k1+……+kn))Em1+…··+(kn / (k1+……+kn))Emn;

[0027] Qx = Ef*Qf / Emz;

[0028] Qxi = (ki / (k1+……+kn))Qx;

[0029] di = g(Qxi);

[0030] In the formula, k1……kn is the fertilizer absorption ratio among the n fertilizer suction tubes, Em1……Emn is the EC value of the fertilizer mother liquor in the n fertilizer tanks, Qxi is the fertilizer absorption flow rate of the i-th fertilizer suction tube, di is the duty cycle of the i-th fertilizer suction solenoid valve in steady state, and g is the relationship function between the flow rate and the duty cycle of the fertilizer suction solenoid valve.

[0031] For n fertilizer suction solenoid valves, different duty cycles are assigned in stages as follows: For the i-th fertilizer suction solenoid valve, first assign 1.5di; when it reaches 50% of the target EC value, assign 1.2di; when it reaches 80% of the target EC value, assign di.

[0032] Optionally, in step 4, PID control is initiated when the supervisor's EC value reaches 95% of the target EC value.

[0033] Optionally, step 5 includes:

[0034] During operation, when the EC value of the main control valve is stable within 3%, record the calculated duty cycle d of the fertilizer suction solenoid valve for each operation. 计 and actual duty cycle d 实 The difference d 差 =d 实 -d 计 And in the next run, the duty cycle will be adjusted to: d = d 计 +d 差 ;

[0035] After multiple runs, the duty cycle difference is averaged over the last 10 runs, and the average value is used to adjust the duty cycle for the next run.

[0036] The beneficial effects of this invention are as follows: By testing the duty cycle characteristics of the fertilizer suction solenoid valve and obtaining the EC values ​​of the fertilizer mother liquor in each fertilizer tank during system pre-running, the relationship between various parameters can be obtained in real time, which greatly simplifies the control program and algorithm and reduces errors. The duty cycle of the fertilizer suction valve is calculated based on the real-time target value and various flow rates, and the system assigns values ​​to the fertilizer suction valve in stages, enabling rapid attainment of steady state (less than 40 seconds). Simultaneously, the duty cycle deviation of each run is recorded, and self-learning correction is performed, resulting in more precise adjustment. This invention solves the problems of long time to reach the EC target value, large steady-state fluctuations, and the inability to automatically test and correct control equipment characteristics and parameters when parameters change in integrated water and fertilizer technology. It has good economic and social value and promising application prospects. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the composition principle of the water and fertilizer EC value rapid adjustment system of the present invention.

[0038] Figure 2 This is the control flowchart of the water and fertilizer EC value rapid adjustment system of the present invention.

[0039] Figure 3 This is a duty cycle characteristic diagram of the solenoid valve of the present invention.

[0040] Figure 4 This is a diagram illustrating the rapid adjustment effect of the present invention.

[0041] The attached diagram is labeled as follows: 1. Irrigation pump; 2. Main pipe flow meter; 3. Main pipe; 4. Water and fertilizer mixing chamber; 5. Main pipe filter; 6. Pressure sensor; 7. Field solenoid valve; 8. Fertilizer pressure reducing valve; 9. Main pipe EC sensor; 10. Fertilizer pipe; 11. Venturi fertilizer suction device; 12. Mixing motor; 13. Fertilizer liquid tank; 14. Fertilizer suction flow meter; 15. Fertilizer suction solenoid valve; 16. Control system; 17. Fertilizer pump; 18. Fertilizer pipe flow meter; 19. Fertilizer pipe EC sensor. Detailed Implementation

[0042] The invention will now be described in further detail with reference to the accompanying drawings.

[0043] Example 1

[0044] This embodiment proposes a rapid adjustment system for water and fertilizer EC values, such as... Figure 1 As shown, the system includes an irrigation system, a fertilization system, and a control system 16. The control system 16 controls the operation of each component according to a programmed sequence. The irrigation system consists of an irrigation pump, a main flow meter, a main pipe, a water-fertilizer mixing chamber, a main pipe filter, a pressure sensor, and a field solenoid valve. The fertilization system consists of a fertilizer pressure reducing valve, a main pipe EC sensor, a fertilizer pipe, a Venturi fertilizer suction device, a mixing motor, a fertilizer tank, a fertilizer suction flow meter, a fertilizer suction solenoid valve, a fertilizer pump, a fertilizer pipe flow meter, and a fertilizer pipe EC sensor.

[0045] In the irrigation system, irrigation pump 1 is connected to main pipe 3, delivering water to the field at a certain flow rate and pressure. Main pipe flow meter 2 is connected to both irrigation pump 1 and main pipe 3, measuring the flow rate in main pipe 3 in real time. Main pipe 3 is used to deliver water at a certain flow rate and pressure. Water-fertilizer mixing chamber 4 is located on main pipe 3, with its two ends positioned between the fertilizer pipe 10 and the inlet / outlet of main pipe 3. The chamber contains a stirring structure to ensure thorough and uniform mixing of the flowing water and fertilizer. Main pipe filter 5 is used to filter impurities from the water. Pressure sensor 6 measures the pipeline pressure; the control system adjusts the pump operation based on the pressure to ensure the normal operation of all system components. Field solenoid valves 7 are located in each irrigation zone in the field, distributing water and fertilizer to the required areas.

[0046] In the fertilizer injection system, the fertilizer pressure reducing valve 8 is located at the inlet of the fertilizer pipe 10 to reduce the pressure of the main pipe 3 to a set lower pressure, which remains constant regardless of the pressure of the main pipe, so that the operating environment of the fertilizer pipe 10 remains consistent. The main pipe EC sensor 9 is located at the rear end of the mixing chamber and the inlet of the fertilizer pipe 10 to measure the EC value of the fully mixed water and fertilizer, i.e. the final EC value entering the field, which is used by the control system as the basis for controlling the amount of water and fertilizer injected. The fertilizer pipe 10 is a pipe for a multi-fertilizer suction system and is equipped with various components. Fertilizer is sucked into the fertilizer pipe 10 and mixed before entering the main pipe 3.

[0047] The Venturi fertilizer suction device 11 is installed in the middle of the fertilizer suction pipe. When water flows through the Venturi fertilizer suction device 11, negative pressure is generated at the fertilizer suction port, and the fertilizer mother liquor in the fertilizer liquid tank 13 is sucked in. The stirring motor 12 is located at the upper end of the fertilizer liquid tank 13, and the stirring device at the lower end is located in the tank. When the fertilizer is sucked, the stirring motor 12 rotates to stir the fertilizer mother liquor in the tank to make it uniform in concentration. There are multiple fertilizer liquid tanks 13 for storing fertilizer mother liquor. The fertilizer suction flow meter 14 is located in the middle of the fertilizer suction pipe between the Venturi fertilizer suction device 11 and the fertilizer liquid tank 13, and is used to measure the real-time fertilizer suction flow. The fertilizer suction solenoid valve 15 is located on the fertilizer suction pipe, and its opening time is controlled by PWM to control the fertilizer suction flow.

[0048] The fertilizer pump 17 is used to pressurize and inject the mixed water and fertilizer into the main pipe 3 to complete the injection of the fertilizer. The fertilizer pipe flow meter 18 is connected to the fertilizer pump 17 and the main pipe 3 at both ends to measure the flow in the fertilizer pipe 10 in real time. The fertilizer pipe EC sensor 19 is located at the end of the fertilizer pipe 10 to measure the EC value of the sucked fertilizer in the fertilizer pipe 10. This EC value can be sensed earlier than the EC value of the fertilizer sucked through the Venturi fertilizer suction device 11 by the main pipe EC sensor 9, so the control system can make decisions in advance to save adjustment time and improve response speed.

[0049] Example Two

[0050] The present embodiment proposes a control method for a water and fertilizer EC value rapid adjustment system based on example one, which comprises the following steps:

[0051] Step 1: Determine the relationship between the fertilizer suction solenoid valve flow and the duty cycle.

[0052] Set the working pressure of the irrigation system, start the irrigation pump and the fertilizer pump, and after the pressure is stable for 10 seconds, set the duty cycle of the fertilizer suction solenoid valve through the program. The duty cycle is 10-90%, with an interval of 5%. The flow at each duty cycle is measured by the fertilizer suction flow meter, and the relationship formula between the fertilizer suction solenoid valve flow and the duty cycle is obtained by data fitting:

[0053] Qx = f(d);

[0054] d = g(Qx);

[0055] In the formula, Qx is the flow of the fertilizer solenoid valve, L / min; d is the duty cycle of the fertilizer solenoid valve.

[0056] Step 2: Pre-run to measure the EC value of the fertilizer mother liquor.

[0057] Turn on the fertilizer solution tank stirring motor for 30 s, set the irrigation system working pressure, start the irrigation pump, and after the pressure is stable for 10 s, turn on the fertilizer pump and one fertilizer solenoid valve, and after the EC value Ef of the fertilizer pipeline is stable for 5 s, record the fertilizer flow Qx and the fertilizer pipeline flow Qf at this time. The system can automatically measure the EC value Em of the fertilizer mother liquor in the fertilizer solution tank by the following formula:

[0058] Em = Ef * Qf / Qx;

[0059] Repeat this step after each change of the fertilizer mother liquor to obtain the new EC value Em of the fertilizer mother liquor.

[0060] Repeat the above process to measure the EC value of the fertilizer mother liquor in each fertilizer solution tank.

[0061] Step 3: Calculate the duty cycle of the fertilizer solenoid valve, assign different duty cycles in stages, and quickly approach the set value.

[0062] In the actual irrigation and fertilization process, according to the target EC value Ez set by the user and the known EC value Em of the fertilizer mother liquor, the real-time flow rates Qz, Qf and Qx are obtained through the main pipe flow meter, the fertilizer pipe flow meter and the fertilizer pipe flow meter. The duty cycle of the fertilizer solenoid valve at steady state can be calculated according to the following formula:

[0063] Ef = Ez * Qz / Qf;

[0064] Qx = Ef * Qf / Em;

[0065] d = g(Qx);

[0066] If the predicted duty cycle d is used as the initial value, the steady state time is too long, first assign 1.5d (≤90%), when the target value 50% is reached, assign 1.2d, when the target value 80% is reached, assign d, and when 95% is reached, PID is enabled. By this method, the speed of reaching steady state can be improved, and excessive overshoot can be avoided, while ensuring high steady state accuracy. The duty cycle characteristics of the electromagnetic valve are shown in Figure 3

[0067] Because the fertilizer needs to pass through the mixing chamber and a long pipeline from the fertilizer pipe to the irrigation main pipe, the main pipe Em will lag behind the fertilizer pipe Ef by 5-15 s, affecting the response speed, therefore, the fertilizer pipe Ef is used as the calculation basis, that is, calculated by the following formula:

[0068] Qx = Ef * Qf / Em; ​

[0069] d = g(Qx);

[0070] If there are multiple fertilizer suction pipes sucking fertilizer at the same time, the calculation is carried out according to the set proportion:

[0071] Emz = (k1 / (k1+…+kn))Em1+…··+(kn / (k1+…+kn))Emn;

[0072] Qx = Ef*Qf / Emz;

[0073] Qxi = (ki / (k1+…+kn))Qx;

[0074] di = g(Qxi);

[0075] In the formula: k1…kn is the fertilizer suction ratio between n fertilizer suction pipes, ki is the fertilizer suction ratio of the i-th fertilizer suction pipe, Emn is the EC value of the fertilizer mother liquor of the n-th fertilizer suction pipe connected fertilizer liquid barrel, Qxi is the fertilizer suction flow of the i-th fertilizer suction pipe, di is the duty cycle of the i-th fertilizer solenoid valve.

[0076] Step 4: PID fine tuning, stable operation.

[0077] When the EC value reaches the target value of 95% during operation, PID control is enabled, the EC value is collected and provided by the main pipe EC sensor, and the PWM controller controls the operation of the fertilizer solenoid valve according to the duty cycle. Multiple Venturi fertilizer suction devices suck fertilizer at the same time, realizing fast and high-precision water and fertilizer ratio.

[0078] Through the above steps, the EC value of the water and fertilizer control system can be quickly adjusted to within ±3% after operation, realizing fast and stable operation, and the time is generally less than 40s, which is greatly reduced compared with the general 80s or more.

[0079] Step 5: Self-learning duty cycle deviation correction.

[0080] During the operation stage, when the main pipe EC value is stable within 3%, record the difference d between the calculated fertilizer solenoid valve duty cycle and the actual duty cycle each time 差 = d 实 -d 计 , and correct this value next time: d = dcount+d 差 .

[0081] After multiple operations, the duty cycle difference is averaged for the last 10 times.

[0082] Through this method, the duty cycle deviation is smaller and closer to the set value, the response speed is faster, and the steady-state accuracy is higher. The fast adjustment effect is as shown in Figure 4 .

[0083] The above are only preferred embodiments of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments. Any technical scheme falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled in the art, some improvements and refinements without departing from the principles of the present application shall be considered as the protection scope of the present application.

Claims

1. A control method for a water-soluble fertilizer EC value rapid adjustment system, the water-soluble fertilizer EC value rapid adjustment system comprising: Irrigation system, fertilizer injection system and control system, the control system is used for controlling the work of the irrigation system and the fertilizer injection system; the irrigation system comprises an irrigation pump (1), a main pipe flow meter (2), a main pipe (3), a water-fertilizer mixing chamber (4) and field electromagnetic valves (7); the irrigation pump (1), the main pipe flow meter (2) and the water-fertilizer mixing chamber (4) are sequentially connected through the main pipe (3), the irrigation pump (1) is used for inputting water into the main pipe (3), the water-fertilizer mixing chamber (4) is used for mixing water flowing in the main pipe (3) and fertilizer mother liquor input into the main pipe (3) through the fertilizer injection system, and water-fertilizer output by the water-fertilizer mixing chamber (4) is distributed to each wheel irrigation area in the field through the field electromagnetic valves (7); The fertilizer injection system comprises a fertilizer injection pressure reducing valve (8), a main pipe EC sensor (9), a fertilizer injection pipe (10), a Venturi fertilizer suction device (11), a fertilizer liquid barrel (13), a fertilizer injection pump (17), a fertilizer injection pipe flow meter (18) and a fertilizer injection pipe EC sensor (19); the inlet and outlet of the fertilizer injection pipe (10) are connected with the outlet and inlet of the water-fertilizer mixing chamber (4) respectively; the fertilizer injection pressure reducing valve (8) and the main pipe EC sensor (9) are sequentially installed at the inlet of the fertilizer injection pipe (10); the middle section of the fertilizer injection pipe (10) is communicated with a plurality of fertilizer suction pipes, each fertilizer suction pipe is provided with a corresponding Venturi fertilizer suction device (11) and a fertilizer liquid barrel (13); when liquid in the fertilizer injection pipe (10) flows through the Venturi fertilizer suction device (11), the Venturi fertilizer suction device (11) sucks the fertilizer mother liquor in the fertilizer liquid barrel (13) and then outputs the fertilizer mother liquor to the fertilizer injection pipe (10), and the sucked fertilizer mother liquor sequentially passes through the fertilizer injection pump (17), the fertilizer injection pipe flow meter (18) and the fertilizer injection pipe EC sensor (19) and then is input into the main pipe (3); The fertilizer injection system further comprises a stirring motor (12), a fertilizer suction flow meter (14) and a fertilizer suction electromagnetic valve (15) installed in each fertilizer suction pipe; the stirring motor (12) is used for stirring the fertilizer mother liquor in the fertilizer liquid barrel (13), and the fertilizer suction flow meter (14) and the fertilizer suction electromagnetic valve (15) are sequentially installed between the fertilizer liquid barrel (13) and the Venturi fertilizer suction device (11); It is characterized by comprising the following steps: Step 1: determining the relationship between the fertilizer suction electromagnetic valve flow and the duty ratio; setting the working pressure of the irrigation system, starting the irrigation pump and the fertilizer injection pump, setting the duty ratio of the fertilizer suction electromagnetic valve after the pressure is stable, taking the value in the range of 10-90% of the duty ratio at an interval of 5%, measuring the flow under each value of the duty ratio by the fertilizer suction flow meter, and obtaining the relationship between the fertilizer suction electromagnetic valve flow and the duty ratio through data fitting; Step 2: pre-running the water-fertilizer EC value rapid adjustment system to measure the EC value of the fertilizer mother liquor in each fertilizer liquid barrel; Step 3: according to the set target EC value of the main pipe, the EC value of the fertilizer mother liquor and the relationship between the fertilizer suction electromagnetic valve flow and the duty ratio, the duty ratio of each fertilizer suction electromagnetic valve in the steady state is calculated, and different duty ratios are assigned to each fertilizer suction electromagnetic valve in stages; Step 4: when the main pipe EC value collected by the main pipe EC sensor reaches the set proportion of the target EC value, starting the PID control, and the PWM controller controls the operation of the fertilizer suction electromagnetic valve according to the duty ratio. Step 5: In the running stage, when the main EC value is stable in the set range, according to the difference between the calculated fertilizer suction solenoid duty ratio and the actual duty ratio, the duty ratio is corrected.

2. The control method according to claim 1, characterized by: The irrigation system further comprises a main pipe filter (5) and a pressure sensor (6) installed between the water-fertilizer mixing chamber (4) and the field electromagnetic valve (7) in sequence.

3. The control method of claim 1, wherein: The step 2 comprises: Start the stirring motor of the fertilizer solution tank, set the working pressure of the irrigation system, start the irrigation pump, open the fertilizer pump and a fertilizer suction solenoid valve after the pressure is stable, record the fertilizer suction flow Qx and the fertilizer pipe flow Qf when the EC value Ef of the fertilizer pipe is stable; wherein the EC value of the fertilizer pipe is measured by the fertilizer pipe EC sensor, the fertilizer suction flow Qx is measured by the fertilizer suction flow meter, and the fertilizer pipe flow Qf is measured by the fertilizer pipe flow meter; The EC value Em of the fertilizer mother liquor in the fertilizer solution tank is measured by the following formula: Em=Ef*Qf / Qx; The EC value Em of the fertilizer mother liquor in the fertilizer solution tank is measured by the following formula: Em=Ef*Qf / Qx; 4. The control method according to claim 3, characterized by: The step 3 comprises: For multiple fertilizer suction pipes that suck fertilizer at the same time, the following calculations are performed according to the set proportion of each fertilizer suction pipe: Emz=(k1 / (k1+……+kn))Em1+……+(kn / (k1+……+kn))Emn; Qx=Ef*Qf / Emz; Qxi=(ki / (k1+……+kn))Qx; di=g(Qxi); Wherein, k1……kn are the fertilizer suction proportions between n fertilizer suction pipes, Em1……Emn are the EC values of the fertilizer mother liquor in n fertilizer solution tanks, Qxi is the fertilizer suction flow of the i-th fertilizer suction pipe, di is the duty ratio of the i-th fertilizer suction solenoid valve in the steady state, and g is a function of the relationship between the flow and the duty ratio of the fertilizer suction solenoid valve; For n fertilizer suction solenoid valves, the following method is used to assign different duty ratios in stages: for the i-th fertilizer suction solenoid valve, first assign 1.5di; when 50% of the target EC value is reached, assign 1.2di; when 80% of the target EC value is reached, assign di.

5. The control method according to claim 4, characterized by: In the step 4, when the main EC value reaches 95% of the target EC value, the PID control is started.

6. The control method of claim 1, wherein: The step 5 comprises: In the running stage, when the main EC value is stable in the range of 3%, the difference between the calculated solenoid duty cycle d and the actual duty cycle d is recorded each time 计 and the duty cycle is corrected in the next run as follows: d = d + d 实 差 实 计 计 差 ;​​​​​ After multiple runs, the difference in duty ratio is averaged for the last 10 times, and the average value is used to correct the duty ratio in the next run. After multiple runs, the difference in duty ratio is averaged for the last 10 times, and the average value is used to correct the duty ratio in the next run.

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