Water and fertilizer EC value rapid adjusting system and control method

Abstract

The invention provides a water and fertilizer EC value rapid adjusting system and a control method, the water and fertilizer EC value rapid adjusting system comprises an irrigation system, a fertilizer injection system and a control system, the irrigation system comprises 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 solenoid valve and the like; the fertilizer injection system is composed of a fertilizer application pressure reducing valve, a main pipe EC sensor, a fertilizer application pipe, a Venturi fertilizer suction device, a stirring motor, a fertilizer liquid barrel, a fertilizer suction flow meter, a fertilizer suction electromagnetic valve, a fertilizer application pump, a fertilizer application pipe flow meter, a fertilizer application pipe EC sensor and the like. According to the invention, the EC value of the fertilizer mother liquor is obtained by testing the flow duty ratio characteristic of the fertilizer suction electromagnetic valve and pre-operating the system, the relationship among parameters is obtained in real time, and errors are reduced while a control program is greatly simplified; the duty ratio of the fertilizer suction electromagnetic valve is calculated through the real-time target value and each flow, and the steady state is quickly achieved through staged assignment; and meanwhile, the duty ratio deviation of each operation is recorded, and self-learning correction is performed, so that the adjustment is more accurate.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated water and fertilizer in agriculture, and particularly relates to a rapid adjustment system and control method for the EC value of water and fertilizer. Background Technique

[0002] In recent years, due to the many advantages of the integrated water and fertilizer technology, such as water conservation, high irrigation uniformity, labor saving, fertilizer saving, and yield increase, it has developed rapidly in China and has been widely used. At present, the main fertilization equipment in the integrated water and fertilizer system includes differential pressure fertilization tanks, high-pressure fertilizer pumps, Venturi fertilizer applicators, hydraulic fertilizer pumps, etc. These devices achieve the purpose of applying fertilizers into the pipeline, but they cannot accurately control the applied concentration, EC, and PH, nor can they achieve automatic control, and they can no longer meet the requirements of precise integrated water and fertilizer. To solve this problem, the research and development of automatic water and fertilizer integrators have been carried out at home and abroad. The control system precisely adjusts water and fertilizer, mixes fertilizer solution and water continuously and quantitatively, and injects them into the irrigation pipeline, achieving high-precision fertilization.

[0003] When the existing water and fertilizer integrator applies fertilizer, according to the set EC target value, the PID controls the duty cycle of the fertilizer suction solenoid valve to change the fertilizer suction amount, and gradually reaches the EC set value. However, the PID control method takes a long time to adjust, generally 1 - 2 minutes, which affects the accuracy of water and fertilizer application. Especially for hydroponics and substrate cultivation, the irrigation and fertilization time each time is only a few minutes, so it is necessary to reach the target value quickly, and the shorter the adjustment time, the better. To solve this problem, currently, methods such as incremental PID algorithms, fuzzy controllers, and neural network models are used to try to improve the response speed of the equipment. However, during the crop cultivation process, due to the continuous changes in pressure, flow rate, mother liquor concentration, EC target value, and fertilizer type, these methods can only adapt to some scenarios with relatively fixed parameters and cannot adapt to the rapid response when parameters change. Therefore, a control method suitable for various scenarios and realizing rapid adjustment is needed. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a rapid adjustment system and control method for the EC value of water and fertilizer to solve the problem that the existing water and fertilizer control system cannot respond quickly to various changing scenarios.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a rapid adjustment system for the EC value of water and fertilizer, including: an irrigation system, a fertilizer injection system, and a control system, where the control system is used to control the operation of the irrigation system and the fertilizer injection system;

[0007] The irrigation system includes an irrigation pump, a main pipe flowmeter, a main pipe, a water-fertilizer mixing chamber, and field solenoid valves; the irrigation pump, the main pipe flowmeter, and the water-fertilizer mixing chamber are sequentially connected through the main pipe. The irrigation pump is used to input water into the main pipe, and the water-fertilizer mixing chamber is used to mix the water flowing into the main pipe and the fertilizer mother liquor input into the main pipe through the fertilizer injection system. The water-fertilizer output from the water-fertilizer mixing chamber is distributed to each round-robin irrigation area in the field through a plurality of field solenoid valves.

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

[0009] Optionally, the fertilizer injection system includes a fertilizer application pressure reducing valve, a main pipe EC sensor, a fertilizer application pipe, a Venturi fertilizer absorber, a fertilizer solution tank, a fertilizer application pump, a fertilizer application pipe flowmeter, and a fertilizer application pipe EC sensor;

[0010] The inlet and outlet of the fertilizer application pipe are respectively connected to the outlet and inlet of the water-fertilizer mixing chamber; the fertilizer application pressure reducing valve and the main pipe EC sensor are sequentially installed at the inlet of the fertilizer application pipe; the middle section of the fertilizer application pipe communicates with a plurality of fertilizer absorption pipes, and each fertilizer absorption pipe is equipped with a corresponding Venturi fertilizer absorber and a fertilizer solution tank; when the liquid in the fertilizer application pipe flows through the Venturi fertilizer absorber, the Venturi fertilizer absorber sucks the fertilizer mother liquor in the fertilizer solution tank and outputs it to the fertilizer application pipe, and the sucked fertilizer mother liquor is input into the main pipe after passing through the fertilizer application pump, the fertilizer application pipe flowmeter, and the fertilizer application pipe EC sensor in sequence.

[0011] Optionally, the fertilizer injection system further includes a stirring motor, a fertilizer absorption flowmeter, and a fertilizer absorption solenoid valve installed in each fertilizer absorption pipe; the stirring motor is used to stir the fertilizer mother liquor in the fertilizer solution tank, and the fertilizer absorption flowmeter and the fertilizer absorption solenoid valve are sequentially installed between the fertilizer solution tank and the Venturi fertilizer absorber.

[0012] In a second aspect, the present invention provides a control method for a water-fertilizer EC value rapid adjustment system using the system in the first aspect, including the following steps:

[0013] Step 1: Determine the relationship between the flow rate of the fertilizer absorption solenoid valve and the duty cycle;

[0014] Step 2: Pre-run the water-fertilizer EC value rapid adjustment system and measure the EC values of the fertilizer mother liquor in each fertilizer solution tank;

[0015] 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 flow rate of the fertilizer absorption solenoid valve and the duty cycle, calculate the duty cycles of each fertilizer absorption solenoid valve at steady state, and assign different duty cycles to each fertilizer absorption solenoid valve in stages;

[0016] Step 4: When the EC value of the main pipe collected by the main pipe EC sensor reaches the set ratio of the target EC value, start PID control, and the PWM controller controls the operation of the fertilizer absorption solenoid valve according to the duty cycle;

[0017] Step 5: During the operation stage, when the EC value of the main pipe is stable within the set range, the duty cycle is corrected according to the difference between the calculated duty cycle of the fertilizer suction solenoid valve and the actual duty cycle.

[0018] Optionally, step 1 includes:

[0019] Set the working pressure of the irrigation system, start the irrigation pump and the fertilization pump, and after the pressure stabilizes, set the duty cycle of the fertilizer suction solenoid valve, and take values ​​in the range of 10-90% at intervals of 5%. Use the fertilizer suction flowmeter to measure the flow rate at each duty cycle value, and obtain the relationship formula between the flow rate and the duty cycle of the fertilizer suction solenoid valve by data fitting: Qx=f(d), d=g(Qx); where Qx is the flow rate of the fertilizer suction solenoid valve, d is the duty cycle of the fertilizer suction solenoid valve, and f and g represent relationship functions.

[0020] Optionally, the step 2 includes:

[0021] Turn on the stirring motor of the fertilizer liquid barrel, set the working pressure of the irrigation system, start the irrigation pump, and after the pressure stabilizes, turn on the fertilizer pump and a fertilizer suction solenoid valve, and after the EC value Ef of the fertilizer pipeline stabilizes, record the fertilizer suction flow rate Qx and the fertilizer pipeline flow rate Qf at this time; the fertilizer pipeline EC value is measured by the fertilizer pipe EC sensor, the fertilizer suction flow rate Qx is measured by the fertilizer suction flowmeter, and the fertilizer pipeline flow rate Qf is measured by the fertilizer pipe flowmeter;

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

[0023] Open each fertilizer suction solenoid valve in turn and measure the EC value of the fertilizer mother solution in each fertilizer liquid barrel.

[0024] Optionally, step 3 includes:

[0025] For multiple fertilizer suction pipes sucking fertilizer at the same time, the following calculation is performed according to the ratio set for 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] Wherein, k1... kn are the fertilizer absorption ratios between n fertilizer absorption pipes, Em1... Emn are the EC values of the fertilizer mother liquor in n fertilizer solution barrels, Qxi is the fertilizer absorption flow rate of the i-th fertilizer absorption pipe, di is the duty cycle of the i-th fertilizer absorption solenoid valve at steady state, and g is the relationship function between the flow rate and the duty cycle of the fertilizer absorption solenoid valve;

[0031] For n fertilizer absorption solenoid valves, different duty cycles are assigned in stages in the following manner: for the i-th fertilizer absorption solenoid valve, first assign 1.5di; when reaching 50% of the target EC value, then assign 1.2di; when reaching 80% of the target EC value, assign di.

[0032] Optionally, in step 4, when the main pipe EC value reaches 95% of the target EC value, start PID control.

[0033] Optionally, step 5 includes:

[0034] During the operation stage, when the main pipe EC value is stable within 3%, record the duty cycle d of the fertilizer absorption solenoid valve calculated each time 计 and the difference d between the actual duty cycle d 实 = d 差 = d 实 - d 计 , and correct the duty cycle for the next operation as: d = d 计 + d 差 ;

[0035] After multiple operations, average the duty cycle differences for the last 10 times, and use the average value to correct the duty cycle for the next operation.

[0036] The beneficial effects of the present invention are as follows: Through the test of the duty cycle characteristics of the fertilizer absorption solenoid valve and the pre-operation of the system to obtain the EC values of the fertilizer mother liquor in each fertilizer solution barrel, the relationship between various parameters can be obtained in real time, which can greatly simplify the control program and algorithm, and at the same time reduce errors; By calculating the duty cycle of the fertilizer absorption valve based on the real-time target value and each flow rate, and the system assigns values to the fertilizer absorption valve in stages, it can achieve a rapid steady state (less than 40 s); At the same time, record the duty cycle deviation of each operation and perform self-learning correction to make the adjustment more accurate. The present invention solves the problems in the water and fertilizer integration technology, such as the long time to reach the EC target value, large steady-state fluctuations, and the inability to automatically test and correct the characteristics and parameters of the control equipment when the parameters change, has good economic value and social value, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0040] Figure 4 It is the quick adjustment effect diagram of the present invention.

[0041] The reference numerals are: 1, irrigation pump; 2, main pipe flowmeter; 3, main pipe; 4, water-fertilizer mixing chamber; 5, main pipe filter; 6, pressure sensor; 7, field solenoid valve; 8, fertilizer application pressure reducing valve 9, main pipe EC sensor; 10, fertilizer application pipe; 11, Venturi fertilizer absorber; 12, stirring motor; 13, fertilizer solution tank; 14, fertilizer absorption flowmeter; 15, fertilizer absorption solenoid valve; 16, control system; 17, fertilizer application pump; 18, fertilizer application pipe flowmeter; 19, fertilizer application pipe EC sensor. Detailed implementation manners

[0042] Now, the present invention will be further described in detail with reference to the accompanying drawings.

[0043] Embodiment 1

[0044] This embodiment provides a water-fertilizer EC value quick adjustment system, as Figure 1 shown, including an irrigation system, a fertilizer injection system, and a control system 16. The control system 16 controls the operation of each component of the system according to the programmed procedure. The irrigation system consists of an irrigation pump, a main pipe flowmeter, a main pipe, a water-fertilizer mixing chamber, a main pipe filter, a pressure sensor, a field solenoid valve, etc.; the fertilizer injection system consists of a fertilizer application pressure reducing valve, a main pipe EC sensor, a fertilizer application pipe, a Venturi fertilizer absorber, a stirring motor, a fertilizer solution tank, a fertilizer absorption flowmeter, a fertilizer absorption solenoid valve, a fertilizer application pump, a fertilizer application pipe flowmeter, a fertilizer application pipe EC sensor, etc.

[0045] In the irrigation system, the irrigation pump 1 is connected to the main pipe 3, and conveys water to the field through the main pipe 3 at a certain flow rate and pressure. The two ends of the main pipe flowmeter 2 are respectively connected to the irrigation pump 1 and the main pipe 3, and the flow rate in the main pipe 3 is measured in real time. The main pipe 3 is used to convey water at a certain flow rate and pressure. The water-fertilizer mixing chamber 4 is located on the main pipe 3, and its two ends are in the middle of the fertilizer application pipe 10 and the inlet and outlet of the main pipe 3. There is a stirring structure in the cavity to make the flowing water and fertilizer fully mixed and uniform. The main pipe filter 5 is used to filter impurities in the water. The pressure sensor 6 is used to measure the pipeline pressure, and the control system adjusts the operation of the water pump according to the pressure to ensure the normal operation of each component of the system. The field solenoid valve 7 is located in each sub-irrigation area in the field to distribute 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, reducing the relatively high pressure of the main pipe 3 to a set lower pressure and maintaining a constant pressure regardless of the main pipe pressure, 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 at the inlet of the fertilizer pipe 10, and is used to measure the EC value of the water-fertilizer mixture after sufficient mixing, that is, the final EC value entering the field. The control system uses this value as the basis for controlling the amount of water-fertilizer applied. The fertilizer pipe 10 is a pipe for a multi-fertilizer suction system, and is equipped with a variety of components. Fertilizer is sucked through the fertilizer pipe 10 and mixed and then enters the main pipe 3.

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

[0048] The fertilizer pump 17 is used to pressurize and inject the mixed water-fertilizer into the main pipe 3 to complete the application of the fertilizer. The two ends of the fertilizer pipe flowmeter 18 are respectively connected to the fertilizer pump 17 and the main pipe 3, and the flow rate in the fertilizer pipe 10 is measured in real time. The fertilizer pipe EC sensor 19 is located at the end of the fertilizer pipe 10 and is used to measure the EC value of the inhaled fertilizer in the fertilizer pipe 10. This EC value can sense the EC value of the fertilizer inhaled through the Venturi fertilizer suction device 11 earlier than the main pipe EC sensor 9. The control system can make decisions in advance, thus saving adjustment time and improving the response speed.

[0049] Embodiment 2

[0050] This embodiment proposes a control method for a water-fertilizer EC value rapid adjustment system based on Embodiment 1. The method includes the following steps:

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

[0052] Set the working pressure of the irrigation system, start the irrigation pump and the fertilizer pump. After the pressure is stable for 10 s, set the duty cycle of the fertilizer suction solenoid valve through the program. The duty cycle ranges from 10% to 90%, with an interval of 5%. The flow rate at each duty cycle is measured by the fertilizer suction flowmeter, and the relationship formula between the fertilizer suction solenoid valve flow rate 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 rate of the fertilizer suction solenoid valve, in L / min; d is the duty cycle of the fertilizer suction solenoid valve.

[0056] Step 2: Measure the EC value of the fertilizer mother liquor during pre-operation.

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

[0058] Em = Ef * Qf / Qx;

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

[0060] Repeat the above process for multiple fertilizer solution tanks to measure them separately.

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

[0062] During 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 pipeline flow meter, fertilizer application pipeline flow meter, and fertilizer suction pipeline flow meter. The duty cycle of the fertilizer suction 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 time to reach steady state is too long. First, assign 1.5d (≤90%), when reaching 50% of the target value, then assign 1.2d, when reaching 80% of the target value, assign d, and when reaching 95% of the target value, the PID is enabled. By this method, the speed to reach steady state can be increased, excessive overshoot can be avoided, and high steady-state accuracy can be ensured at the same time. The duty cycle characteristics of the solenoid valve are as Figure 3 shown.

[0067] Since the fertilizer needs to pass through the mixing chamber and a relatively long pipeline from the fertilizer application pipeline to the irrigation main pipeline, the Em of the main pipeline will lag behind the Ef of the fertilizer application pipeline by 5 - 15 s, which affects the response speed. Therefore, the Ef of the fertilizer application pipeline is used as the calculation benchmark, that is, calculated through 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 based on the set ratio:

[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 absorption ratio between n fertilizer absorption pipes, ki is the fertilizer absorption ratio of the i-th fertilizer absorption pipe, Emn is the EC value of the fertilizer mother liquid in the fertilizer tank connected to the n-th fertilizer absorption pipe, Qxi is the fertilizer absorption flow rate of the i-th fertilizer absorption pipe, and di is the duty cycle of the i-th fertilizer absorption solenoid valve.

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

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

[0078] Through the above steps, the EC value of the water-fertilizer control system can be quickly adjusted to within the range of ±3% after operation, achieving rapid stabilization, 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 phase, when the EC value of the main pipe is stable within 3%, record the difference between the calculated duty cycle of the fertilizer suction solenoid valve and the actual duty cycle. 差 =d 实 -d 计 , correct this value at the next run: d = d count + d 差 .

[0081] After multiple runs, the duty cycle differences are averaged over the last 10 times.

[0082] This method makes the duty cycle deviation smaller, closer to the set value, faster response speed and higher steady-state accuracy. Figure 4 shown.

[0083] The above are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. Any technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A water and fertilizer EC value rapid adjustment system, characterized in that: include: An irrigation system, a fertilizer injection system and a control system, wherein the control system is used to control the operation 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 a field electromagnetic valve (7); the irrigation pump (1), the main pipe flow meter (2) and the water-fertilizer mixing chamber (4) are connected in sequence through the main pipe (3); the irrigation pump (1) is used to input water into the main pipe (3); the water-fertilizer mixing chamber (4) is used to mix water flowing into the main pipe (3) and fertilizer mother liquid input into the main pipe (3) through a fertilizer injection system; the water and fertilizer output from the water-fertilizer mixing chamber (4) are distributed to each irrigation area in the field through a plurality of field electromagnetic valves (7).

2. A water-fertilizer EC value rapid adjustment system as claimed in claim 1, characterized in that: The irrigation system also includes a main pipe filter (5) and a pressure sensor (6), which are sequentially installed between the water-fertilizer mixing chamber (4) and the field electromagnetic valve (7).

3. A water-fertilizer EC value rapid adjustment system as claimed in claim 1, characterized in that: The fertilizer injection system comprises a fertilizer pressure reducing valve (8), a main pipe EC sensor (9), a fertilizer pipe (10), a venturi fertilizer suction device (11), a fertilizer liquid barrel (13), a fertilizer pump (17), a fertilizer pipe flow meter (18) and a fertilizer pipe EC sensor (19); The inlet and outlet of the fertilizer pipe (10) are respectively connected to the outlet and inlet of the water-fertilizer mixing chamber (4); the fertilizer pressure reducing valve (8) and the main pipe EC sensor (9) are sequentially installed at the inlet of the fertilizer pipe (10); the middle section of the fertilizer pipe (10) is connected to a plurality of fertilizer suction pipes, each of which is equipped with a corresponding venturi fertilizer suction device (11) and a fertilizer liquid barrel (13); when the liquid in the fertilizer pipe (10) flows through the venturi fertilizer suction device (11), the venturi fertilizer suction device (11) sucks the fertilizer mother liquid in the fertilizer liquid barrel (13) and outputs it to the fertilizer pipe (10); the sucked fertilizer mother liquid passes through a fertilizer pump (17), a fertilizer pipe flow meter (18) and a fertilizer pipe EC sensor (19) in sequence and is then input into the main pipe (3).

4. A water-fertilizer EC value rapid adjustment system as claimed in claim 3, characterized in that: The fertilizer injection system further comprises a stirring motor (12), a fertilizer suction flow meter (14) and a fertilizer suction solenoid valve (15) installed in each fertilizer suction pipe; the stirring motor (12) is used to stir the fertilizer mother liquid in the fertilizer liquid barrel (13), and the fertilizer suction flow meter (14) and the fertilizer suction solenoid valve (15) are installed in sequence between the fertilizer liquid barrel (13) and the Venturi fertilizer suction device (11).

5. A control method using the water-fertilizer EC value rapid adjustment system as claimed in claim 4, characterized in that: The steps include: Step 1: Determine the relationship between the flow rate and duty cycle of the fertilizer suction solenoid valve; Step 2: Pre-run the water and fertilizer EC value rapid adjustment system to measure the EC value of the fertilizer mother solution in each fertilizer liquid barrel; Step 3: According to the set target EC value of the main pipe, EC value of the fertilizer mother solution and the relationship between the flow rate and duty cycle of the fertilizer suction solenoid valve, calculate the duty cycle of each fertilizer suction solenoid valve in steady state, and assign different duty cycles to each fertilizer suction solenoid valve in stages; Step 4: When the EC value of the main pipe collected by the main pipe EC sensor reaches the set ratio of the target EC value, the PID control is started, and the PWM controller controls the operation of the fertilizer suction solenoid valve according to the duty cycle; Step 5: During the operation stage, when the EC value of the main pipe is stable within the set range, the duty cycle is corrected according to the difference between the calculated duty cycle of the fertilizer suction solenoid valve and the actual duty cycle.

6. The control method according to claim 5, characterized in that: The step 1 comprises: Set the working pressure of the irrigation system, start the irrigation pump and the fertilization pump, and after the pressure stabilizes, set the duty cycle of the fertilizer suction solenoid valve, and take values ​​in the range of 10-90% at intervals of 5%. Use the fertilizer suction flowmeter to measure the flow rate at each duty cycle value, and obtain the relationship formula between the flow rate and the duty cycle of the fertilizer suction solenoid valve by data fitting: Qx=f(d), d=g(Qx); where Qx is the flow rate of the fertilizer suction solenoid valve, d is the duty cycle of the fertilizer suction solenoid valve, and f and g represent relationship functions.

7. The control method according to claim 5, characterized in that: The step 2 comprises: Turn on the stirring motor of the fertilizer liquid barrel, set the working pressure of the irrigation system, start the irrigation pump, and after the pressure stabilizes, turn on the fertilizer pump and a fertilizer suction solenoid valve, and after the EC value Ef of the fertilizer pipeline stabilizes, record the fertilizer suction flow rate Qx and the fertilizer pipeline flow rate Qf at this time; the fertilizer pipeline EC value is measured by the fertilizer pipe EC sensor, the fertilizer suction flow rate Qx is measured by the fertilizer suction flowmeter, and the fertilizer pipeline flow rate Qf is measured by the fertilizer pipe flowmeter; The EC value Em of the fertilizer mother solution in the fertilizer tank is measured by the following formula: Em = Ef*Qf / Qx; Open each fertilizer suction solenoid valve in turn and measure the EC value of the fertilizer mother solution in each fertilizer liquid barrel.

8. The control method according to claim 7, characterized in that: The step 3 comprises: For multiple fertilizer suction pipes sucking fertilizer at the same time, the following calculation is performed according to the ratio set for 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); In the formula, k1...kn is the fertilizer absorption ratio between n fertilizer absorption pipes, Em1...Emn is the EC value of the fertilizer mother solution in n fertilizer liquid barrels, Qxi is the fertilizer absorption flow rate of the i-th fertilizer absorption pipe, di is the duty cycle of the i-th fertilizer absorption solenoid valve in steady state, and g is the relationship function between the fertilizer absorption solenoid valve flow rate and the duty cycle; For n fertilizer suction solenoid valves, different duty cycles are assigned in stages in the following manner: for the i-th fertilizer suction solenoid valve, 1.5di is first assigned; when it reaches 50% of the target EC value, 1.2di is assigned; when it reaches 80% of the target EC value, di is assigned.

9. The control method according to claim 8, characterized in that: In step 4, when the main pipe EC value reaches 95% of the target EC value, PID control is started.

10. The control method according to claim 5, characterized in that: The step 5 comprises: During the operation phase, when the EC value of the main pipe is stable within 3%, record the duty cycle d of the fertilizer suction solenoid valve calculated each time. 计 and the actual duty cycle d 实 The difference d 差 =d 实 -d 计 , and the duty cycle is corrected to: d = d 计 +d 差 ; After multiple runs, the duty cycle differences are averaged over the last 10 times, and the average value is used to correct the duty cycle during the next run.

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