Multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation and control method

Abstract

The invention relates to a multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation and a control method, and belongs to the field of agricultural intelligent irrigation and water and fertilizer integration. A plurality of independent diaphragm pumps, a suction pipe, an output pipe, a main pipeline and a control box are fixedly mounted on a rack; inlets of the diaphragm pumps are respectively connected with respective fertilizer source barrels through suction pipes, and outlets of the diaphragm pumps are respectively converged into the main pipeline through output pipes; an EC / PH sensor is mounted on the main pipeline and is used for monitoring the conductivity and the pH value of the mixed fertilizer liquid in real time; a control box is installed on the upper portion of the machine frame, an electric control system is installed in the control box, and the electric control system comprises a main controller, a man-machine interaction interface and a speed regulation driving module. The human-computer interaction interface is connected with the main controller; the interface end of the speed regulation driving module is connected with the main controller, and the output end of the speed regulation driving module is connected with the diaphragm pumps. The device is reasonable in structure and accurate in control, continuous, linear and pulse-free injection of fertilizer liquid can be achieved, and energy consumption is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of intelligent agricultural irrigation and fertigation technology, and in particular to a multi-channel fertilizer applicator and control method based on diaphragm pump direct injection and PWM speed regulation. Background Technology

[0002] In modern precision agriculture, fertigation technology is key to achieving efficient, cost-effective, and environmentally friendly irrigation. Currently, most mainstream automatic fertilizer applicators on the market use a venturi tube combined with a solenoid valve. Its working principle involves using a water pump to create a high-speed water flow in the main pipeline, drawing fertilizer solution from the fertilizer tank through the local vacuum generated by the venturi tube, and then mixing and injecting it into the irrigation system.

[0003] However, this traditional approach has the following inherent drawbacks: First, fertilization is discontinuous and exhibits pulse phenomena. Due to the switching action of the solenoid valve, fertilizer injection is intermittent, making continuous and smooth injection impossible. This causes frequent fluctuations in the EC / pH value of the mixed solution around the target value, severely limiting control precision and stability and affecting the uniform absorption of nutrients by crops. Second, energy efficiency is extremely low. The Venturi effect itself involves significant energy loss, requiring high-power water pumps to maintain high pressure in the main pipeline. Most of the electrical energy is ultimately converted into heat and dissipated, resulting in high overall system energy consumption, which does not align with the trend of green energy conservation. Third, it places high demands on the power grid and infrastructure. The start-up and operation of high-power motors can impact the relatively weak power grids in rural areas, often requiring dedicated power supply lines. This significantly increases the installation cost of the equipment and limits its application in scenarios without a stable high-power power source. Finally, the system is highly dependent. Fertilization efficiency is strongly correlated with the pressure in the main pipeline. Pressure fluctuations in the irrigation network directly and non-linearly affect the fertilizer absorption of the Venturi tube, making the control model complex and difficult to achieve stable and precise fertilizer-solution ratios. Therefore, how to design a fertilization device with a reasonable structure, precise control, and the ability to achieve continuous, linear, and pulse-free injection of fertilizer solution while significantly reducing energy consumption has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] To overcome the problems existing in the background technology, the present invention provides a multi-channel fertilizer applicator and its control method based on diaphragm pump direct injection and PWM speed regulation, which has a reasonable structure, precise control, can realize continuous, linear, pulse-free fertilizer injection, and significantly reduce energy consumption.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation, comprising a frame; multiple independent diaphragm pumps, suction pipes, output pipes, a main pipeline, and a control box are fixedly installed on the frame; the inlets of the multiple diaphragm pumps are respectively connected to their respective fertilizer source tanks through suction pipes, and their outlets are respectively connected to the main pipeline through output pipes; an EC / PH sensor is installed on the main pipeline to monitor the conductivity and pH of the mixed fertilizer solution in real time; a control box is installed on the upper part of the frame, and an electrical control system is installed in the control box, which includes a main controller, a human-machine interface, and a speed regulation drive module; the human-machine interface is connected to the main controller; the interface of the speed regulation drive module is connected to the main controller, and its output is connected to the multiple diaphragm pumps respectively. Multiple independent diaphragm pumps are used as direct-drive injection units to directly and actively pump fertilizer solutions from each channel into the main pipeline, eliminating dependence on the pressure of the main pipeline and achieving independent control of the injection process. At the same time, through real-time feedback from EC / PH sensors and closed-loop control of the main controller, combined with precise speed regulation of the diaphragm pumps by the speed regulation drive module, continuous stepless adjustment of the flow rate can be achieved, thereby ensuring the accurate and stable EC / PH value of the mixed fertilizer solution.

[0006] In the above technical solutions, the diaphragm pumps are all DC diaphragm pumps. DC diaphragm pumps have the advantages of rapid start-up and shutdown, excellent speed regulation characteristics, and simple control. They are particularly suitable for PWM pulse width modulation speed regulation, providing an ideal actuator for achieving high-precision linear control of flow rate.

[0007] In the above technical solution, the speed control drive module includes a current analog output module and a DC motor speed control module. The input terminal of the current analog output module is connected to the main controller, and the output terminal is communicatively connected to the DC motor speed control module. The DC motor speed control module is communicatively connected to the diaphragm pump. The main controller controls the current analog output module through digital or analog signals, which then drives the DC motor speed control module to generate precise PWM signals, forming a hierarchical stable drive architecture. This ensures accurate transmission of control commands and enhances the anti-interference capability and system reliability under high-current drive.

[0008] In the above technical solution, there are at least 3 diaphragm pumps, and the diaphragm pumps are matched with the DC motor speed control module.

[0009] In the above technical solution, the EC / PH sensor is connected to the main controller via an EC / PH transmitter. The EC / PH transmitter converts the weak signal detected by the sensor into a standard signal (such as 4-20mA or 0-10V) and transmits it to the main controller, improving the anti-interference capability and measurement accuracy of signal transmission, and providing a reliable data foundation for closed-loop control.

[0010] In the above technical solution, the operating voltage of the diaphragm pump is 12-48V.

[0011] This technical solution also provides a control method for a multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation, characterized by the following steps: S1. Set the target EC and pH values ​​of the mixed fertilizer solution through the human-computer interaction interface; S2. The main controller collects the actual values ​​of the mixed fertilizer solution detected by the EC / pH sensor in real time; S3. The main controller compares the detected actual value with the corresponding target value and uses the built-in control algorithm to calculate the real-time injection flow rate required for each fertilizer solution and acid-base adjustment solution. S4. The main controller converts the real-time injected flow of each channel into the corresponding PWM duty cycle command and sends it to the speed control drive module. S5. The speed control drive module outputs multiple PWM signals with adjustable duty cycles according to the received instructions, which drive multiple diaphragm pumps to run at corresponding speeds, thereby achieving continuous linear regulation of flow rate. S6. Repeat steps S2 to S5 to form a closed-loop control, so that the EC value and pH value of the mixed fertilizer solution are dynamically stabilized at the set target value.

[0012] This method is based on real-time EC / PH detection and dynamically adjusts the PWM drive signal of each diaphragm pump through a closed-loop algorithm, thereby achieving synchronous, continuous and precise control of the fertilizer injection flow rate of multiple channels and ensuring the constant concentration of the final mixed fertilizer solution.

[0013] In the above technical solution, the control algorithm described in step S3 is a fuzzy PID control algorithm or a model predictive control (MPC) algorithm. Using advanced control algorithms such as fuzzy PID or MPC can better handle the multivariable, nonlinear, and time-delay characteristics of the fertilization system. Compared with traditional PID, it has a faster response speed, stronger anti-disturbance capability, and higher steady-state accuracy, further improving the system's control performance.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention replaces the Venturi tube with a diaphragm pump for direct injection and combines it with PWM stepless speed regulation technology to achieve continuous, linear and pulse-free injection of fertilizer solution, thereby eliminating the flow pulsation of the traditional solution from the source and significantly improving the control accuracy and stability of EC / PH value. Since the fertilizer injection power comes from the diaphragm pump itself rather than the main pipeline pressure, the system is not sensitive to the pressure fluctuation of the main pipeline, the fertilizer injection stability is higher, the complexity of the control model is simplified, and the robustness of the system is improved.

[0015] (2) The present invention uses a low-power DC diaphragm pump, which completely eliminates the need for a high-power water pump, reduces energy consumption by about 86%, has a significant energy-saving effect, and has no impact on the power grid, reducing the requirements for infrastructure and broadening the applicable scenarios.

[0016] (3) The present invention features multi-channel independent control, complete decoupling of fertilizer injection amount and main pipeline pressure, strong anti-interference ability of the system, and simple and reliable control model; through the combination of PWM speed regulation and EC / PH closed-loop control, high-precision and automated control of fertilizer ratio and total amount is achieved, meeting the requirements of precision agriculture; modular and multi-channel design supports flexible ratio of various fertilizers and regulators, and has good scalability.

[0017] (4) This invention adopts diaphragm pump direct injection and PWM stepless speed regulation, completely abandoning the traditional solenoid valve switching mode, realizing continuous, linear and pulse-free smooth injection of fertilizer solution from zero to maximum flow. Preliminary tests show that its flow control curve has excellent linearity, fundamentally solving the problem of EC / PH value fluctuation, and achieving a qualitative leap in control accuracy and stability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 This is a system schematic diagram of an embodiment of the present invention; Figure 3 This is a circuit control diagram of the speed control drive module according to an embodiment of the present invention; Figure 4 This is a circuit control diagram of the diaphragm pump according to an embodiment of the present invention; In the diagram, 1. Frame, 2. Diaphragm pump, 3. Suction pipe, 4. Output pipe, 5. Main pipeline, 6. Control box, 7. Fertilizer tank, 8. EC / PH sensor, 9. Main controller, 10. Human-machine interface, 11. Speed ​​control drive module, 111. Current analog output module, 112. DC motor speed control module, 12. EC / PH transmitter. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0021] In the following description, when referring to the accompanying drawings, the same numbers in different drawings denote the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0022] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances. Furthermore, in the description of this invention, unless otherwise stated, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] like Figures 1 to 4 The multi-channel fertilizer applicator shown includes a frame 11. At least three independent diaphragm pumps 2, suction pipes 3, output pipes 4, a main pipeline 5, and a control box 6 are fixedly mounted on the frame 11. In this embodiment, three diaphragm pumps 2 are installed. The inlets of the three pumps 2 are connected to their respective fertilizer source tanks 7 via suction pipes 3, and their outlets are connected to the main pipeline 5 via output pipes 4. The three pumps 2 are used to inject fertilizer solution A, fertilizer solution B, and acid-base adjustment solution, respectively. In this structure, the three pumps 2 act as independent power units, drawing fertilizer solution from their respective fertilizer source tanks 7 via suction pipes 3 and pumping the fertilizer solution directly into the main pipeline 5 via output pipes 4 to mix with irrigation water. This "pump direct injection" method completely eliminates the dependence on the Venturi negative pressure effect and the high pressure of the main pipeline, making the fertilizer injection action completely autonomous and controllable. At the same time, by operating the three pumps independently, it achieves the precise addition of A / B fertilizers and acid-base adjustment solution without interference, providing a physical basis for precise multi-variable proportioning.

[0025] An EC / PH sensor 8 is installed on the main pipeline 5 to monitor the conductivity and pH of the mixed fertilizer solution in real time. The EC / PH sensor 8 is connected to the main controller 9 via an EC / PH transmitter 12. The EC / PH transmitter 12 performs temperature compensation, amplification, and conversion of the electrode signal from the EC / PH sensor 8 into a standard industrial signal. Simultaneously, the signal conditioning function of the EC / PH transmitter 12 effectively suppresses noise interference during long-distance transmission, providing the main controller 9 with high-precision and high-stability EC / PH measurements. This is an indispensable foundation for achieving high-precision closed-loop control.

[0026] A control box 6 is mounted on the upper part of the frame 1. The control box 6 houses an electrical control system, which includes a main controller 9, a human-machine interface 10, and a speed control drive module 11. The human-machine interface 10 is connected to the main controller 9. The interface of the speed control drive module 11 is connected to the main controller 9, and its output is connected to three diaphragm pumps 2. The speed control drive module 11 includes a current analog output module 111 and a DC motor speed control module 112. The input of the current analog output module 111 is connected to the main controller 9, and its output is communicatively connected to the DC motor speed control module 112. The DC motor speed control module 112 is communicatively connected to the diaphragm pumps 2. In this embodiment, the main controller 9 is a Linux industrial computer with a built-in 4G module. As the brain of the system, it outputs digital or low-level analog signals to the current analog output module 111, which generates a stable, interference-resistant current signal to control the DC motor speed control module 112. Simultaneously, this hierarchical drive design effectively isolates low-voltage control from high-voltage drive, protecting the core main controller 9 while ensuring the stability and reliability of the high current driving the diaphragm pump 2, achieving synergistic optimization of control accuracy and drive capability. The human-machine interface 10 is a 7-inch touchscreen integrated into the control box 6 panel, used for parameter setting, status display, and manual control. It provides users with an intuitive entry point for parameter setting and status monitoring. The main controller 9, as the brain, is responsible for processing data from the 8EC / PH sensors, executing control algorithms, and issuing control commands. The speed control drive module 11, as the "nerve endings and actuators," converts digital commands into physical signals to drive the diaphragm pump 2. These three components work together to form a complete monitoring-decision-execution closed loop, ensuring intelligent and automatic system operation.

[0027] In this embodiment, the analog current output module 111 has an RS485 communication interface and three PWM signal output terminals. The analog current output module 111 receives instructions from the main controller 9 through the RS485 communication interface and converts them into three independent PWM signals. The three independent PWM signals are transmitted to three DC motor speed control modules 112, which drive three diaphragm pumps 2. The main controller 9 sends flow setting instructions to the speed control drive module 11 through the RS485 bus, ensuring reliable communication over long distances and strong scalability. The speed control drive module 11 internally calculates the instructions into three independent PWM duty cycle signals, which precisely control the DC motor speeds of the three diaphragm pumps 2. Simultaneously, by adjusting the PWM duty cycle, stepless and linear adjustment of the pump speed is achieved, thereby obtaining a continuous, smooth, and precisely controllable fertilizer solution flow rate, fundamentally eliminating pulse injection.

[0028] In some embodiments, the speed control drive module 11 is an integrated RS485 to multi-channel PWM DC motor speed controller. The main controller 9 is a Linux industrial computer with a built-in 4G module, running a mature integrated water and fertilizer control program and capable of communicating with a cloud platform. The three diaphragm pumps 2 are preferably diaphragm pumps powered by 24V DC. In this combined structure, the Linux industrial computer provides a powerful computing platform that can run complex algorithms such as fuzzy PID or MPC to handle multivariable coupled control; the combination of low-power DC diaphragm pumps 2 and efficient PWM speed control drive results in extremely low overall system power consumption (more than 86% lower than the traditional 2.2KW solution), and it can be driven by ordinary mains power or even solar panels, greatly reducing energy consumption and the barrier to entry; the cloud communication function enables remote management of equipment, data analysis, and fault early warning, improving the level of intelligent operation and maintenance.

[0029] This embodiment is based on a control method for a multi-channel fertilizer applicator using diaphragm pump direct injection and PWM speed regulation, including the following steps: S1. Set the target EC value and pH value of the mixed fertilizer solution through the human-computer interaction interface 10; S2, The main controller 9 collects the actual values ​​of the mixed fertilizer solution detected by the EC / pH sensor 8 in real time; S3 and main controller 9 compare the detected actual value with the corresponding target value and use the built-in control algorithm to calculate the real-time injection flow rate required for each fertilizer solution and acid-base adjustment solution. S4, the main controller 9 converts the real-time injected flow of each channel into the corresponding PWM duty cycle command and sends it to the speed control drive module 11; S5. The speed control drive module 11 outputs multiple PWM signals with adjustable duty cycles according to the received instructions, and drives multiple diaphragm pumps 2 to run at corresponding speeds to achieve continuous linear adjustment of flow rate. S6. Repeat steps S2 to S5 to form a closed-loop control, dynamically stabilizing the EC and pH values ​​of the mixed fertilizer solution at the set target values. In this method, flow control is converted into PWM control of the rotation speed of the DC diaphragm pump 2, with a direct and continuously adjustable response. At the same time, through real-time feedback of EC / pH values, the rotation speed of each pump is dynamically corrected, forming a fast and adaptive adjustment loop. This ensures that even when the EC value of the water source fluctuates or the fertilizer formula changes, the final concentration of the mixed solution remains highly stable.

[0030] To address system time delays and nonlinearities and further improve control quality, in some embodiments, the control algorithm described in step S3 is a fuzzy PID control algorithm or a model predictive control (MPC) algorithm. The fuzzy PID algorithm can self-tune PID parameters online to adapt to changes in system operating conditions; the MPC algorithm can predict future dynamics based on the system model and optimize the current control input. Furthermore, by employing these advanced algorithms and combining them with the fast and linear controlled object characteristics of the "independent pump direct injection + PWM speed regulation" method of this invention, the advantages of the algorithms can be fully utilized to achieve excellent control effects such as small overshoot, short settling time, and zero steady-state error—achievements that are difficult to attain with traditional Venturi systems due to their inherent delays and nonlinearities.

[0031] Referring to the accompanying drawings, the working principle of this invention is as follows: The user sets the desired EC and pH values ​​of the fertilizer solution through the human-machine interface 10. After the system starts, each diaphragm pump 2 begins to work under the initial PWM signal drive, pumping different fertilizer solutions from the fertilizer source tank 7 through the suction pipe 3, and mixing them in the main pipeline 5 through the output pipe 4. The EC / pH sensor 8 installed on the main pipeline 5 detects the concentration and pH of the mixed solution in real time, and sends the signal to the main controller 9 through the EC / pH transmitter 12. The main controller 9 compares the measured value with the set value, calculates the required flow rate change of each channel to eliminate the deviation according to algorithms such as fuzzy PID or MPC, and then converts it into a new PWM duty cycle command and sends it to the speed control drive module 11. The speed control drive module 11 adjusts the PWM signal output to each diaphragm pump 2, changing its speed, thereby precisely regulating the instantaneous injection flow rate of each channel. This process is repeated cyclically, forming a real-time closed loop, so that the EC / pH value of the mixed fertilizer solution is accurately maintained near the set target. Therefore, this invention fundamentally solves a series of inherent defects of traditional Venturi fertilizer applicators, such as discontinuous fertilizer injection, high energy consumption, dependence on pipeline pressure, and poor control accuracy, through the synergistic innovation of two core technologies: "independent DC diaphragm pump 2 direct drive injection" and "PWM closed-loop speed regulation based on real-time EC / PH feedback". This invention achieves continuous, precise, efficient and energy-saving fertilization operations.

[0032] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this application, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0033] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation, characterized in that: The system includes a frame (1); multiple independent diaphragm pumps (2), suction pipes (3), output pipes (4), main pipelines (5), and a control box (6) are fixedly installed on the frame (1); the inlets of the multiple diaphragm pumps (2) are connected to their respective fertilizer source tanks (7) through suction pipes (3), and their outlets are connected to the main pipelines (5) through output pipes (4); an EC / PH sensor (8) is installed on the main pipelines (5) to monitor the conductivity and pH of the mixed fertilizer solution in real time; a control box (6) is installed on the upper part of the frame (1), and an electrical control system is installed inside the control box (6). The electrical control system includes a main controller (9), a human-machine interface (10), and a speed control drive module (11); the human-machine interface (10) is connected to the main controller (9); the interface of the speed control drive module (11) is connected to the main controller (9), and its output is connected to the multiple diaphragm pumps (2).

2. The multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation according to claim 1, characterized in that: The diaphragm pumps (2) mentioned above are all DC diaphragm pumps.

3. A multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation according to claim 1, characterized in that: The speed control drive module (11) includes a current analog output module (111) and a DC motor speed control module (112); the input end of the current analog output module (111) is connected to the main controller (9), and the output end is connected to the DC motor speed control module (112) in communication. The DC motor speed control module (112) is connected to the diaphragm pump (2) in communication.

4. A multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation according to claim 3, characterized in that: The diaphragm pump (2) is at least 3 units, and the diaphragm pump (2) is matched with the DC motor speed control module (112).

5. A multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation as described in claim 1, characterized in that: The EC / PH sensor (8) is connected to the main controller (9) via the EC / PH transmitter (12).

6. A multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation according to claim 1, characterized in that: The working voltage of the diaphragm pump (2) is 12-48V.

7. The control method for a multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation according to any one of claims 1-6, characterized in that: Includes the following steps: S1. Set the target EC value and pH value of the mixed fertilizer solution through the human-computer interaction interface (10); S2, The main controller (9) collects the actual value of the mixed fertilizer solution detected by the EC / pH sensor (8) in real time; S3. The main controller (9) compares the detected actual value with the corresponding target value and uses the built-in control algorithm to calculate the real-time injection flow rate required for each fertilizer solution and acid-base adjustment solution. S4. The main controller (9) converts the real-time injected flow of each channel into the corresponding PWM duty cycle instruction and sends it to the speed control drive module (11). S5. The speed control drive module (11) outputs multiple PWM signals with adjustable duty cycles according to the received instructions, and drives multiple diaphragm pumps (2) to run at corresponding speeds to achieve continuous linear regulation of flow rate. S6. Repeat steps S2 to S5 to form a closed-loop control, so that the EC value and pH value of the mixed fertilizer solution are dynamically stabilized at the set target value.

8. The control method for a multi-channel fertilizer applicator based on diaphragm pump direct injection and PWM speed regulation according to claim 7, characterized in that: The control algorithm described in step S3 is either a fuzzy PID control algorithm or a model predictive control (MPC) algorithm.

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