Research On Control Strategy Of Electro-hydraulic Lifting System For High-horsepower Tractor

At present,our country is in the key period of the transformation of agricultural power to agricultural power,domestic tractor electro-hydraulic lifting system in the intelligence,information,energy saving and other aspects compared with foreign similar products there is a big gap.In addition,in the application process of the electro-hydraulic lifting system,due to the existence of complex external interference and the great change of operation load,the tractor electro-hydraulic lifting system has problems such as poor control accuracy and high energy loss,which has become the bottleneck restricting the development of the tractor electro-hydraulic lifting system in China.In response to the goal of "strengthening the support of agricultural science and technology and equipment and realizing the modernization of rural agricultural equipment" put forward in the report of China’s "20th National Congress".This paper takes the tractor electro-hydraulic lifting system as the research object,aiming at the problems of the tractor electro-hydraulic lifting system in different soil environments,such as the large difference in tillage efficiency,low intelligence,low control accuracy and large energy consumption.The main research contents of this paper are as follows:(1)Firstly,the working principle of the traditional tractor mechanical hydraulic lifting system is introduced,and the structural composition,advantages and disadvantages of the traditional tractor mechanical hydraulic lifting system are analyzed;A tractor electro-hydraulic lifting system based on pump control system was established based on mechanical hydraulic lifting system.The mechanical structure and working principle of tractor pump-controlled electro-hydraulic lifting system are designed and analyzed,and the main components are designed and analyzed.(2)Secondly,the advantages and disadvantages of the existing electro-hydraulic lifting control mode are analyzed from the aspects of control accuracy,application range,mode switching,etc.,and the force and position integration control mode is determined.The concepts of equivalent tillage depth and comprehensive coefficient of force level were introduced,and the difference of weight distribution between tractive force and tillage depth position was realized by adjusting the comprehensive coefficient of force level,so as to meet the needs of different tillage environments.(3)Then,aiming at the non-linearity,lag and uncertainty of the influencing factors of the tractor electro-hydraulic lifting system,the mathematical model of the tractor electro-hydraulic lifting system is established,and the advantages and disadvantages of PID control,optimized PID control and sliding mode control algorithms are analyzed in the tractor electro-hydraulic lifting system.On this basis,an observer---sliding mode control algorithm is proposed and designed.Build the relevant controller model..(4)AMESim is used to build the simulation model of the hydraulic part of the electro-hydraulic lifting system,Simulink is used to build the control strategy model,and AMESim/Simulink are co-simulated through the interworking interface.The control effect of different control algorithms under the force and position integrated control mode and the traction integrated control mode are analyzed,and the adjustment strategies of different weight coefficients under the force and position integrated control mode are analyzed.(5)Finally,the test platform of electro-hydraulic lifting system is set up.The test platform is arranged with a roof structure,and the test platform consists of two parts:electro-hydraulic lifting system and load simulation system.The electro-hydraulic lifting system adopts the principle of pump control system design,and the load simulation system adopts valve control system design.The mathematical model,simulation model and control algorithm proposed in this paper are analyzed and verified by the test platform.The results show that the designed tractor electro-hydraulic lifting system and the proposed control strategy can achieve the expected effect.