Design And Analysis Of Electro-Hydraulic Suspension Control System For High Power Tractor Based On Soil Specific Resistivity

With the gradually increase of modern agriculture for the refine working requirements,the electro-hydraulic control system replacing the traditional hydraulic suspension system has become the development trend of high power tractor.At present,in view of the larger and frequent working environment of soil specific resistance,the research of electro-hydraulic suspension control system focuses on stability,response time and operation quality.Therefore,based on the relationship between the soil specific resistance and the weight coefficient,the control scheme of the electro-hydraulic suspension control system is deeply studied from the aspects of system structure analysis,control strategy construction,improvement of operation precision and field test.In view of the disadvantages of low intelligence and poor quality of the traditional hydraulic suspension system,the electro-hydraulic suspension control system and control scheme based on soil specific resistance were designed.Based on the functional requirements,the hydraulic system is designed,and the proportional solenoid valve,sensor and flipping plow are selected.By analyzing the influence factors of soil specific resistance,a mathematical model between soil specific resistance,soil water content and soil clay content was constructedFor the characteristics of electro-hydraulic control system such as time-varying and nonlinear,a fuzzy PID control strategy is built,and the fuzzy PID control parameters are designed according to the system requirements.By constructing mathematical models of proportional electromagnet,proportional valve driving hydrau;:c cylinder,suspension mechanism and sensors,the simulation comparison between fuzzy PID control and PID control is carried out on Matlab/Simulik platform in three aspects:position adjustment,force adjustment and force-position adjustment.It is sh(?)is that fuzzy PID has prominent advantages in response time,standard deviation of respense and anti-interference ability of the systemOn the basis of building fuzzy PID control strategy,the relationship between soil specific resistance and weight coefficient is simulated.In the soil resistivity variation were 0,10,20,30,40,50k(?)/m2,the force-position control simulations were carried out with weight coefficient of 0.2,0.4,0.6,0.8 and 1.Combining with the actual operation requirements,the lationship between the weight coefficient and the specific resistance of soil is obtained by processing the simulation data,and the three order fitting curve equation is established.Based on the SCM,main program of electrohydraulic control system and the subroutines of AD conversion,PWM signal output,weight coefficient automatic control and fuzzy PID control are designed,and the progressiveness test and weight coefficient automatic control field test of electro-hydraulic suspension system are carried out.The test results show that the electro-hydraulic control system can realize the expected function.