Study On Characteristics Of Pressure Compensator For Load Sensitive Electro-hydraulic Proportional System Of Modern Agricultural Equipment

As the agricultural mechanization developed,the requirements of the market for the operation accuracy,stability and energy saving of agricultural equipment are becoming more and more intense.The load sensitive electro-hydraulic proportional system with pressure compensator is widely used in the hydraulic system of modern agricultural equipment.As the key core component of load sensitive electro-hydraulic proportional system,the performance of pressure compensator directly affects the operation accuracy,stability,energy saving and reliability of hydraulic system and complete equipment.However,the technical level of domestic load sensitive electro-hydraulic proportional valve is low,and the performance of pressure compensator is generally poor,which is difficult to meet the operation and energy-saving requirements of modern agricultural equipment.Therefore,this thesis designs a pressure compensator for load sensitive electro-hydraulic proportional system of modern agricultural equipment,and studies and analyzes its dynamic performance.Firstly,according to the working conditions and requirements of modern agricultural equipment,a load sensitive electro-hydraulic proportional system pressure compensator was designed.Taking the new pressure compensator as the research object and the pressure compensator of a multi-channel valve in the market as the comparison object,the state space equations of two pressure compensators based on boundary conditions were established by using the power bond graph theory.And the key system parameters such as each hydraulic resistance,the overflow area of each throttle and hydrodynamic force were theoretically analyzed and deduced.Based on MATLAB/Simulink,the dynamic response characteristics of the mathematical models of the two pressure compensation systems were analyzed and compared.The comparison results reflected that when the opening of the main valve port is certain,the response speed of the new pressure compensator is faster and the stability of the response is significantly improved compared with the multi-channel valve pressure compensator.Secondly,the full parameter simulation model of the new pressure compensator was built based on AMESim.The effects of the spring stiffness of the differential pressure reducing valve,the spring preload,the diameter of the damping hole in the control chamber,the viscous friction coefficient and the quality of the valve core on the dynamic response characteristics of the pressure compensator were studied.Through orthogonal simulation analysis,it was found that the pressure compensator with spring stiffness of 22 N/mm,spring preload of 90 N and viscous friction coefficient of 1(s?N)?m has the best dynamic response characteristics.And the optimal design of the pressure compensator of load sensitive electro-hydraulic proportional system of modern agricultural equipment was completed.Then,the AMESim simulation platform was used to build the simulation model of a multi-channel valve pressure compensator,and the start-up characteristics and compensation characteristics of the two pressure compensators were simulated,analyzed and compared.The comparison results reflected that the results of simulation analysis and mathematical analysis were homologous,which verifies the correctness of the mathematical model.Compared with the multi-channel valve pressure compensator,the starting speed of the new pressure compensator is improved,the oscillation process is weakened,and the stability of the response is obviously improved.Moreover,the new pressure compensator has better load pressure following characteristics,and its flow compensation characteristics and differential pressure compensation characteristics are better than the multi-channel valve pressure compensator.It is proved that the dynamic characteristic of the pressure compensator of the load sensitive electro-hydraulic proportional system of modern agricultural equipment is better than that of the multi-channel valve pressure compensator.Finally,the comprehensive experimental platform of intelligent electro-hydraulic proportional hydraulic valve was built,and the experimental data acquisition system was designed based on Lab VIEW.The new pressure compensator was inserted into the electro-hydraulic proportional lift valve of large tractor for experimental research.By designing four experimental schemes under different working conditions,the starting characteristics,compensation characteristics,differential pressure control characteristics and flow stability characteristics of the new pressure compensator were experimentally studied.The results reflected that the experimental results are similar with the simulation results,which proves the correctness of the simulation model and the correctness of the simulation test conclusion.Under the action of rectangular wave signal,the maximum overshoot of main valve output flow and main valve port pressure difference is less than 5%,which proves that the pressure compensator of load sensitive electro-hydraulic proportional system of modern agricultural equipment has good dynamic characteristics.