Design Of Variable Flow Controller For Plant Protection Machine

Large machines for plant protection are necessary agricultural tools for large-scale mechanized production in modern agriculture,which help save manpower and improve production efficiency.However,it is incredibly difficult to keep spraying uniform on the foliage of plants when plant protection machines are traveling at a high speed and under different conditions of insecticide supply.During the long-term continuous operation,the plant protection machine may come across such problems as changes of the nozzle and plunger pump,and failure of the control valve,which result in inaccurate flow control of the plant protection machine,easily causing insufficient spraying or excessive spraying.This paper studies the variable flow spraying control system of the plant protection machine with the plunger pump as the core,fully considers the complex situation of the plant protection machine’s operation in the field,and a precise variable flow controller with strong robustness and fault tolerance is designed.Since the characteristics of the servo valve,the swash plate drive mechanism of the plunger pump,and the control valve of the liquid medicine circuit are prone to change,some parameters in the model will occur perturbation.Hence,an engineering model with undefined items is built.For this engineering model,a robust adaptive controller is designed based on the RBF neural network.Firstly,the RBF neural network is used to approximate these items for parameter perturbation and external disturbance,and then the design of controller is completed by combining the Backstepping method.The simulation is conducted to verify the controller,which achieves desirable control effects under various working conditions and when the parameters of the plant protection machine are perturbed.The controller boasts favorable robustness and anti-interference ability to the parameter perturbation of the plunger pump during operation.Finally,after considering the situation that the electro-hydraulic servo valve as actuator is prone to failure and that the Backstepping algorithm is vulnerable to “computational explosion”,the controller is improved.The dynamic surface control is introduced to redesign the fault-tolerant controller with fault-tolerant capability for the failure of the electro-hydraulic servo valve.By means of simulation verification,the control effect of the electro-hydraulic servo valve as actuator in different degrees of failure and with parameter perturbation interference are simulated.The results show that the fault-tolerant controller can still accurately control the flow of the plant protection machine even in the case of partial failure of the electro-hydraulic servo valve,and has an even faster response speed,which achieves better control effect than the robust adaptive controller and PID controller.