Research On Control Method Of Variable Flow Spraying For Plant Protection Machine

As a powerful tool for precise agricultural production management,the plant protection machine is widely used in comprehensive prevention and cure of crops.In particular,it plays an important role in the control of spraying flow for precise on-demand pesticide application.During the spraying operation process,parameters such as the leakage of the pipeline,liquid volume elastic modulus of physic liquor are greatly affected by changes in plant protection machine operating conditions.In addition,the spraying system objectively has complex situations that are difficult to estimate,for instance,element wear and aging,spray nozzle jam,and hydraulic oil leakage.At present,extensive spraying and lagging response to the adjustment of the pesticide application flow are prevalent in plant protection machine,which causes problems such as liquid waste and environmental pollution.This thesis studies the spraying system of plant protection machine with piston pump as the core,fully considers the uncertainty of the spraying system in the complex and variable field environment,and deeply researches the precise control of the spraying flow of the plant protection machine.According to the market demand for plant protection machine at different levels and agronomic standards,the variable flow spraying controller for plant protection machine is designed.Firstly,this thesis analyzed the sources of system uncertainty,and the influence of the driving mode of the coaxial connection of the piston pump spindle and plant protection machine power shaft of the plant protection machine on spraying parameters.The displacement and speed of the variable piston of the piston pump,the force of the variable swash plate,and the displacement of the spool of the electro-hydraulic servo valve are selected as state variables.In the form of parameter perturbation,a fourth-order state space model of spraying system considering uncertainty and external disturbances is established.Secondly,for the simple structure,low-cost plant protection machine spraying system that directly adjusts the spraying flow by the displacement of the piston pump,the robust spraying flow controller is designed.It makes up for the deficiency of traditional PID control method which is sensitive to uncertainty.The robust stability is analyzed and transformed into a linear matrix inequality(LMI)that meets the robust H? performance index to solve the controller parameters.On this basis,for specific agronomic indicators,it is necessary to maintain the spray pressure at a constant value to ensure the demand of atomization distribution effect of nozzle,the thesis continues to study the constant pressure and variable flow spray control of higher process quality.According to the characteristic that the flow is proportional to the opening of the valve port under a constant pressure difference,a method for achieving constant pressure and variable flow spraying by using a piston pump to keep the spray pressure stable and coordinated with the opening adjustment of the electric regulating valve is proposed.Fuzzy rules are formulated based on the regulating valve opening error and rate of change.In addition,the fuzzy self-tuning PID controller for the opening of the valve port is designed to adjust the throttling conditions of the chemical liquid pipeline.Finally,the above-mentioned variable flow spraying control method is verified by simulation experiments,and the process of variable flow spraying of plant protection machine under various working conditions is simulated.The results show that the designed control system has fast response speed and strong robustness,which meet the requirements of plant protection machines with different costs and agronomic indicators require precision variable flow spraying of smart agriculture under a range of parameter perturbations and external disturbance.It realizes the real-time and accurate adjustment of the spray flow according to the running speed for a simple low-cost plant protection machine.In addition,for plant protection machines that require higher-quality agronomy,comprehensive decisions are made based on operating environment information,and constant pressure with variable flow spray control is performed,which effectively improves the utilization rate of pesticides.