Variable Flow Control Of Spraying Medicine For Tractor Mounted Machine

Plant protection is one of the important work in modern agricultural production.At present,the most common way to control diseases and insect pests is chemical treatment.However,in the process of prevention and control of diseases and insect pests,most of the liquid is scattered in the air and deposited in the soil,not only a large amount of chemicals are wasted,but the ingredients of these residues are likely to enter the body of the organism,and badly threatens the life safety of human and animal,and it also pollute the environment.Therefore,in order to reduce the pollution degree of pesticide to environment,variable spray technology is an important content and direction of current tractor-mounted machine research and development.The tractor-mounted machine can reduce environmental pollution by increasing the utilization rate of pesticides according to the requirements of spraying targets.This thesis mainly controls the output flow of variable spraying system of tractor-mounted machine.According to the requirement of spraying machine in the actual working process of tractor-mounted machine,a mathematical model of variable rate spraying system under two conditions is studied.One is the centralized parameter modeling of variable rate spray system based on magnetic circuit equation,motion equation and flow equation under the condit ion of constant pressure variable spray system.Because the pressure of the constant pressure variable spray system has a certain range of volatility,which leads to the uncertainty of the system,so the model of the system is established as a two order linear uncertain state space model.Based on the established uncertain linear state space model,a robust output tracking controller is designed to construct the optimal method,and the output tracking error is converged to zero.In the process of control design,the system augmented state equation is built first,then the optimal performance index with the specified stability degree is constructed for the augmented state equation of the nominal system,and the adjustment factor is introduced to get the better control input.And a simulation shows the control performance of the robust controller.The another is to control the output pressure of the piston pump by direct drive valve under the condition of the pressure variable injection system.The equation of the output pressure of the direct drive valve to control the piston pump is coupled with the proportional pressure relief valve to control the flow rate.A four order nonlinear system model is obtained.Then,the model is linearized at the working point,and the process of linearizing of model makes it produced uncertainty and error.And the four order linear uncertainty system with the variable pressure spray system is finally obtained.And then a robust output tracking control strategy is designed,a adjustment factor is introduced.Finally,the MATLAB simulation software is used and the result shows that the robust tracking control strategy based on the optimal algorithm can achieve good control performance on the output pressure and flow rate of the pressure variable spray system.