Control Algorithms Of Tractor Electro-hydraulic Lifting System And Leakage Diagnosis Of Lifting Cylinder

As a large agricultural country with sustained population growth,the development of agricultural technology of China is still at a low level.It is urgent to improve the degree of agricultural modernization for promoting national development and maintaining social stability.It is an inevitable trend for China's agricultural development to develop and popularize automated and intelligent agricultural machinery operation by combining agricultural machinery represented by tractor electro-hydraulic lifting system with electro-mechanical integration technology,intelligent control technology,computer technology,intelligent monitoring and maintenance technology.In order to improve the tractor's farming efficiency,optimize the farming effect and ensure the working reliability,this paper designs the software and hardware of its core system electro-hydraulic lifting system,establishes the mathematical model of the system,analyses the dynamic characteristics of the lifting mechanism and hydraulic system,and studies the improvement of the plowing depth and traction force in an ideal state.Control strategy,hardware-in-the-loop simulation platform of electro-hydraulic lifting system is built,and the diagnosis algorithm for common leakage faults of hydraulic system is put forward,so as to obtain an intelligent,efficient and reliable scheme of tractor hydraulic hoisting system.The main contents of this paper are as follows:(1)The whole and key sub-components of the tractor hydraulic hoisting system are designed.The function and structure of the system are proposed.Based on dynamic analysis,the hydraulic subsystem and components are designed and selected.The control circuit and user panel are further designed.Compared with the traditional lifting device,the designed system can reduce the driver's labor intensity,facilitate the accurate and efficient completion of ploughing operation,and improve the reliability and safety.(2)The control strategy of electro-hydraulic hoisting system is proposed.After comparing four classical control modes of tractor hydraulic lifting system,the advantages of force-position integrated control over other control schemes are pointed out,and the concepts of equivalent tillage depth and force-position integrated degree are put forward.The control system model is established and the transfer function is deduced.On this basis,the integrated PID control,fuzzy control and fuzzy PID control algorithm for the force and position of the electro-hydraulic hoisting system are proposed.(3)An algorithm for leakage diagnosis of electro-hydraulic lifting hydraulic actuator based on subspace identification is proposed.The system state space model is established by choosing the external force load of the piston rod of the hydraulic cylinder as the input signal,and the pressure of two chambers,displacement and velocity of the piston rod as the state variables.The estimation values of the related elements of the system matrix are obtained by subspace identification operation,and the existence,type and severity of the leakage fault are judged accordingly.Using MATLAB-Simulink to build the simulation model of the oil cylinder leakage system,the numerical simulation validation of the diagnosis method is carried out.The results show that the method is effective and has high accuracy.(4)The control strategy of electro-hydraulic lifting system is realized and verified.Simulink software model of electro-hydraulic hoisting system is established,and a hardware-in-the-loop simulation platform of electro-hydraulic hoisting system based on xPC target with high efficiency,low cost and strong reliability is built.The proposed control strategy is verified.The results show that the proposed control strategy can meet the predetermined control objectives of the hoisting system.