Study On Design Of Electro-hydraulic Suspension Valve Controll System Of Tractor

The electro-hydraulic suspension system is an important subsystem of the tractor set,and its performance directly affects the working quality and efficiency of the tractor.The electro-hydraulic proportional valve,as the core part of the electro-hydraulic suspension system,directly affects the control accuracy of the electro-hydraulic suspension system,because of its response speed,the linearity of the control current and flow rate,and the anti-interference ability.At the same time,because the working environment of the tractor is very bad,complex and changeable,a reasonable control strategy need be worked out to improve the tillage quality of tractor.In the paper,the electro-hydraulic suspension valve controll system that meets the above requirements is designed to achieve the intelligent control of the electro-hydraulic lifting of tractor,and this study has important theoretical and practical significance for improving its control quality and tillage quality.Based on the analysis of the traditional hydraulic suspension system of the tractor,the electro-hydraulic suspension valve controll system and the integrated special electro-hydraulic proportional valve are designed.Based on analyzing the structure and working process of electro-hydraulic proportional valve,the lifting process are simulated and analyzed.The results show that the designed electro-hydraulic suspension valve controll system has quick response,and the control current and flow rate are linear in the working interval.Based on the comparative analysis of the tractor tillage depth adjustment methods and control strategies,a fuzzy PID control strategy based on force and position integrated control is laied out.The fuzzy subset and membership function of the input and PID control parameters are defined,and the fuzzy control rules of PID control parameters are established.On this basis,the fuzzy controller is edited and the fuzzy PID control system is established.The core hydraulic components and the hydraulic system are modeled and simulated,and their steady and dynamic characteristics and the anti-interference ability are analyzed.A combined simulation model of the electro-hydraulic control system based on fuzzy PID control is established,and the changes of tractor's tillage depth and traction resistance under different force and position proportional ratios are analyzed.The results show that the system control current and flow rate are linear in the working interval,the system step response time is 0.02s.When the system is disturbed by the external resistance,the flow rate tends to be stable in about 0.1s,and the anti-interference ability is strong.In the process of the comprehensive adjustment of the force and position,the response of the electro-hydraulic suspension valve control system is rapid,and the effect of tillage is good.The experiment researches for the designed electro-hydraulic proportional valve and fuzzy PID control strategy are carried out respectively.The relationship between the control current and flow rate of the electro-hydraulic proportional valve is tested,and the variations of ploughing depth and the working quality of tractor under different force and position proportional ratios are also tested.The accuracy of the control and the feasibility of the system are checked up.The experiment results are consistent with the simulation results in general,which can achieve high precision control for the lifting speed of the tractor hanging agricultural implements,and it can take into the evenness of the tractor ploughing depth and the stability of load,and adapt to the tractor complex and changeable working environments.