CN-121986768-A - PWM variable spraying system and control method thereof

CN121986768ACN 121986768 ACN121986768 ACN 121986768ACN-121986768-A

Abstract

The invention discloses a PWM variable spraying system and a control method thereof, wherein the PWM variable spraying system comprises a medicine box, a variable spray head assembly, a PWM variable spraying control system, an intelligent central control platform, a spraying donor pipeline, at least one spraying branch pipeline, a return pipeline, a medicine liquid pump, a control valve group, an acquisition assembly and a pressure stabilizing filter assembly, and the control valve group comprises a main switch valve, a main pipeline switch valve, a branch switch valve and a proportional overflow valve. The invention reduces the coupling effect of 'pressure change caused by flow regulation and rheology caused by pressure regulation' by constructing a three-layer measurement and control structure of 'spray start-stop cycle-pressure regulation cycle-flow regulation cycle', adopts long-period and short-period cooperative scheduling, and improves the recovery speed and control stability under the state transition working condition. And the total spraying flow feedback structure is introduced to realize flow closed loop correction, so that the control precision and the robustness of the spraying quantity are improved.

Inventors

WEI XINHUA
WANG KUN
WEI XIAOYANG
SONG QI
LIU CHENGLIANG
SUN YONG

Assignees

江苏大学
镇江金泰智能科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260211

Claims (10)

1. The PWM variable spraying system is characterized by comprising a medicine box (1), a variable spray head assembly, a PWM variable spraying control system (2), an intelligent central control platform (19), a spraying donor pipeline (3), at least one spraying branch pipeline (4), a return pipeline (5), a medicine liquid pump (6), a control valve group, an acquisition assembly and a stable pressure filtering assembly (7); Each spraying branch pipeline (4) is respectively communicated with a spraying donor pipeline (3), at least two groups of variable nozzle assemblies are arranged at the tail end of each spraying branch pipeline (4) in parallel, the other end of each spraying donor pipeline (3) is communicated with a liquid inlet of the medicine box (1), one end of the reflux pipeline (5) is arranged on a pipeline between the spraying donor pipeline (3) and the spraying branch pipeline (4), and the other end of the reflux pipeline is communicated with the reflux inlet of the medicine box (1); The control valve group comprises a main switching valve (8), a main pipeline switching valve (10), a branch switching valve (9) and a proportional overflow valve (15); The main switch valve (8), the liquid medicine pump (6), the pressure stabilizing filter assembly (7), the main pipeline switch valve (10) and the acquisition assembly are sequentially arranged on the spraying donor pipeline (3), the branch switch valve (9) is respectively arranged on each spraying branch pipeline (4), and the proportional overflow valve (15) is arranged on the return pipeline (5); The PWM variable spraying controller (2) is respectively in signal connection with the branch switching valve (9), the main pipeline switching valve (10) and the acquisition component; The intelligent central control platform (19) is in signal connection with the environment wind speed sensor (14) and the PWM variable spraying control system (2) respectively.
2. The PWM variable spraying system according to claim 1, wherein the collecting assembly comprises a main pipeline turbine flow sensor (11) and a pipeline pressure sensor (12), one end of the return pipeline (5) is arranged between the main pipeline switching valve (10) and the collecting assembly, and the main pipeline turbine flow sensor (11) and the pipeline pressure sensor (12) are respectively connected with the PWM variable spraying control system (2) in a signal mode.
3. The variable PWM spraying system according to claim 1, further comprising a rotational speed sensor (13), wherein the rotational speed sensor (13) is connected to the liquid medicine pump (6) and is in signal connection with the variable PWM spraying control system (2).
4. The PWM variable spraying system according to claim 1, wherein a reflux pipeline turbine flow sensor (16) in signal connection with the PWM variable spraying control system (2) is further arranged between the medicine box (1) and the proportional overflow valve (15).
5. The PWM variable spraying system according to claim 1, wherein the PWM variable spraying control system (2) comprises a PWM variable spraying controller, a PWM signal generator and a driver, and the intelligent central control platform (19) and the PWM variable spraying controller, the PWM signal generator and the driver are all mounted on the same CAN bus.
6. The PWM variable spraying system according to claim 1, wherein the variable spraying head assembly comprises a spraying head (17) and an electromagnetic valve (18), the electromagnetic valve (18) and the spraying head (17) are sequentially arranged on the spraying branch pipeline (4), liquid medicine flows to the spraying head (17) through the electromagnetic valve (18), and the electromagnetic valve (18) is in signal connection with the PWM variable spraying control system (2).
7. The control method for realizing the PWM variable spraying system according to any one of claims 1 to 6, which is characterized by comprising the following steps: adopts a three-layer measurement and control circulation structure of spray start-stop circulation, pressure regulation circulation and flow regulation circulation in a variable dosing mode, The spray start-stop circulation is used for controlling a main switch valve (8) and a branch switch valve (9) of a main pipeline switch valve (10) to realize start-up, stop-up and partition start-stop, and enable a system to timely enter long-period regulation and control to finish the resetting of a working point when the state changes; The pressure regulation and control cycle comprises pressure regulation and pressure stability control, and is used for regulating the reflux quantity through a proportional relief valve (15) so as to enable the spray pressure to track the set spray pressure In the normal operation process, the pressure is controlled stably according to a fixed period so as to eliminate the influence of the fluctuation of the rotating speed of the liquid medicine pump (6); the flow regulation cycle comprises flow regulation and flow stabilization control for spraying pressure in real time Under the condition of calculating and outputting PWM duty ratio of each spray head (17) so as to make total spray flow follow target total spray flow In the normal operation process, the stable control of the pesticide application flow is carried out according to a fixed period so as to eliminate the influence of the fluctuation of the operation speed of the pesticide application machine; The pressure regulation and control cycle and the flow regulation and control cycle adopt a scheduling mechanism combining a long period and a short period, wherein the long period is used for setting a working point when the working state is switched or the target spray quantity is changed, and the short period is used for closed-loop stable control of Tian Nalian continuous advancing processes.
8. The method for controlling a PWM variable spraying system according to claim 7, wherein the spray start-stop cycle is specifically: after the whole machine is electrified, a PWM variable spraying controller (2) obtains the partition topology, namely the partition number of a spray head (17) Number of nozzles (17) per zone, flow coefficient of nozzle PWM cycle Minimum on/off pulse width , Pressure target Filter coefficient PID parameters of pressure inner loop And anti-saturation parameter And a total flow correction parameter ; Collecting and checking states of a pipeline pressure sensor (12), a main pipeline turbine flow sensor (11), a return pipeline turbine flow sensor (16), a speed signal and a branch switch valve (9); Performing spray start-up and branch state judgment, controlling a main pipeline switch valve (8) and a branch switch valve (9) of a spray donor pipeline (3) to realize start-up/stop-up/partition start-up according to the operation command and the state of the branch switch valve (9), and generating a long-period trigger mark When any one of the following conditions is satisfied Starting the spraying, turning the machine on the line, restarting the line after turning around, stopping the spraying, starting the machine again after stopping the spraying, and enabling the step change of the prescription value and the target application amount and the state change of the partition switch valve to exceed a threshold value.
9. The method for controlling a PWM variable spraying system according to claim 7, wherein the pressure adjustment and the flow adjustment are open-loop decoupling adjustment with a long period: Pressure regulation: determining the current set spray pressure according to the current ambient wind speed, the liquid medicine characteristics and the anti-drift requirements, and collecting the rotation speed of the pump And obtaining the pump liquid supply amount from the pump characteristic model Constructing a target reflux overflow amount: will be dependent on the characteristics of the proportional relief valve (15) Converting into a valve control instruction and outputting the valve control instruction to enable the pressure to approach the set spraying pressure; because the action of the proportional overflow valve (15) is slower, the execution time of the pressure regulating process is longer, and when the prescription value and the application amount decision value are changed or the process is only executed once, the process also needs to be executed when the environmental wind speed is changed to disperse the fog drops to other application areas; And (3) flow regulation: According to the total spraying target flow of the spraying branch pipeline (4) Based on the target application rate Real-time speed And effectively spray the width Calculating a target total spray flow: calculating the target flow of each spraying branch pipeline (4) according to the opening and closing states of the branch switch valve (9) Then obtaining the target flow of the single spray head (17) according to the number of the spray heads (17) of each spraying branch pipeline (4) : Wherein the method comprises the steps of Is the first The spraying branch pipelines (4) are assembled with the spray heads (17); Pressure is collected Calculating the flow rate when the electromagnetic valve (18) is fully opened: The electromagnetic valve (18) is periodically opened and closed at a fixed frequency, and the duty ratio is calculated by the flow of the target single spray head (17): for each duty cycle: And applies a minimum on/off pulse width constraint: Then distributing phase offset according to the number of the spray head (17), wherein each path of PWM signal is output in opposite phase at intervals, namely one path of positive phase output and one path of opposite phase output; Because the action frequency of the electromagnetic valve (18) is faster and the signal frequency of the electromagnetic valve (18) is unchanged, the flow adjustment process time is short, and the flow adjustment precision is improved, the flow adjustment of multiple rounds is carried out in one pressure adjustment process, and the current real-time application pressure is adopted for calculating the duty ratio in each round.
10. The method of claim 7, wherein the pressure stabilizing control and the flow stabilizing control are closed loop control with a short period: The pressure of the spraying donor pipeline (3) is used as a controlled quantity, the opening of the proportional overflow valve (15) is used as a control input, and the pressure stability control is realized by proportional, integral and differential adjustment of pressure deviation: performing first-order low-pass filtering on the measured pressure: in order to obtain the value of the pressure after filtering, Is the measured pressure value; defining a pressure control error as: In the event of a pressure error, Setting a pressure value; the PID controller outputs control instructions for the proportional overflow valve (15) The basic form is as follows: considering the physical constraints of the valve control command, the actual output saturation value: Taking out , ; Based on pressure errors Disturbance estimator constructed with pressure change rate And adds compensation term in the output instruction of the proportional overflow valve (15) Wherein the method comprises the steps of Is PID output after anti-saturation; the output value is the output value after disturbance rejection estimation; The flow stability control, namely, the default pressure is the set pressure, and is only disturbed by the operation speed of the pesticide applying machine, the total spraying flow of the system is taken as the feedback quantity, the integral PID control of the duty ratio is carried out, the integral correction quantity of the duty ratio is limited by amplitude limitation, and the closed loop correction factor is introduced to compensate systematic deviation caused by wear and blockage of a spray head (17), viscosity change of liquid medicine or calibration error of the coefficient of the spray head (17); In a short period, obtaining real-time total flow based on the total spraying flow sensor Constructing a flow error: and applying an integral correction to the duty cycle of each nozzle (17) : The correction amount is added to the duty ratio of each spray head (17) and limited: simultaneously introducing a closed loop correction factor: And (3) superposing correction factors to obtain: 。

Description

PWM variable spraying system and control method thereof Technical Field The invention relates to a PWM variable spraying system and a control method thereof, belonging to the technical field of agricultural plant protection machinery and precise pesticide application control. Background The excessive use of pesticides in agricultural production is easy to cause environmental pollution and waste of liquid medicine, and the accurate agricultural requirement is to adjust the application amount in real time according to the prescription amount or working condition. Common implementations of variable dosing include pressure regulation, concentration variation, and PWM intermittent spraying. The PWM intermittent spraying can realize the adjustment of the application amount and maintain the spraying uniformity by controlling the duty ratio of the high-speed switching electromagnetic valve to adjust the equivalent flow. The Chinese patent with publication number CN202010978945.6 discloses a dual PID control accurate variable drug delivery system and a feedback regulation method thereof, variable drug delivery is realized by changing spraying time, spraying pressure or liquid medicine concentration, wherein a PWM regulating water pump is adopted to realize flow control by changing spraying pressure, and in order to improve flow control stability and response speed, the dual PID is adopted, an outer ring carries out PID by deviation of flow feedback and set flow, outputs 'required compensated flow/target rotating speed', an inner ring takes speed measurement of a motor tail shaft photoelectric encoder as feedback as PID, and finally, a motor end voltage and rotating speed are changed by regulating a motor, thereby indirectly realizing flow tracking. Chinese patent publication No. CN202510088278.7 discloses an independent variable dosing voltage stabilizing system and control method. The system is based on a spray head electromagnetic valve of PWM, and the patent proposes a control framework of self-running test and self-learning correction, wherein the control framework comprises the steps of automatically identifying and fitting the relation between flow and pressure of a regulating valve, the relation between flow and PWM frequency of a spray head, the relation between duty ratio and pressure of a main pipeline, calibrating the reference flow of the main pipeline when each operation or flow change occurs, calculating the opening degree of the regulating valve and the duty ratio of the spray head of the next grid in advance according to grids during operation, adopting a strategy of grading assignment and restarting PID if necessary, realizing quick voltage stabilization during grid switching, and simultaneously recording the opening deviation and correcting by recent average so as to improve voltage stabilization precision. The disadvantage is that the need to run the calibration fit on-site frequently in advance results in high field adaptability and maintenance costs. The control of the method depends on a fitting model and a discrete assignment strategy, systematic deviation is easy to generate when nonlinear conditions such as abrupt change, valve hysteresis, blocking abrasion and the like are met, PID feedback correction is required to be frequently started, and the robustness is limited. The fitting model and the discrete assignment strategy are used for regarding the relation between the flow and the pressure by using a coupling thought, and the control of the pressure and the flow in the coupling state is realized by calibrating corresponding parameters. However, the strategy of realizing the application rate control by pressure regulation is commonly adopted in the existing spray application system, namely the flow rate of a spray head and the pressure of a pipeline approximately meet the square root relation, and the system changes the flow rate by changing the pressure and meets the application rate requirement of a unit area. In field operation, the fluctuation of the operation speed is common, if the pressure regulation compensation speed is still adopted, the pressure is inevitably changed along with the flow regulation, and the atomized particle size, the fog drop distribution and the anti-drift performance are further changed, so that the uncertainty of the applied effect is generated, and the problem of pressure-flow coupling is formed. Therefore, a control system and a method are needed that can keep the pipeline pressure stable in the presence of disturbance and uncertainty, and can quickly adjust the spraying amount through PWM under the pressure stable condition, so as to realize the mutual decoupling of the unit area pesticide application amount control and the pressure stable. Disclosure of Invention The invention aims to: aiming at the defects existing in the prior art, the invention provides a PWM variable spraying system and a control method thereof, the invention constructs a three-layer