Design And Experiment On The Electric-hydraulic Control System Of Tractor’s Three-point Suspension

The development of agriculture lies in agricultural mechanization,in the context of deepening the development of agricultural mechanization of high quality,how to improve the tractor tillage efficiency and reduce labor costs is particularly important in the study of tractors,so the study of tractor rear suspension system with automatic control of tillage depth is of great significance to the future development of agricultural machinery.In recent years,microelectronic control technology and hydraulic technology is increasingly mature,the application on the tractor more and more widely,the thesis to a 1304 type wheeled tractor as a prototype,its hydraulic oil circuit and control system research and analysis,on the basis of which the design of the tractor electric-hydraulic control system with tillage depth automatic adjustment function,can effectively solve the traditional tractor field operation when the tillage depth inconsistent problem.In the hydraulic design section,a hydraulic control system for the rear suspension of the prototype was designed according to the common field operation movements of the tractor,using electro-hydraulic proportional reversing valve as the main control valve,based on the parameters of the original double-acting cylinder of the tractor,determine the type of key hydraulic components,according to the type of the selected valve group and the hydraulic schematic diagram to complete the design of the integrated valve block.The electronic control system takes STM32 microcontroller as the core controller,designs the corresponding circuit module in hardware,adopts the control strategy of position control,completes the design of interface circuit combined with dual tilt sensors and proportional valve,realizes signal acquisition and signal transmission,completes the adjustment of PID parameters according to the engineering adjustment method,eliminates certain overshoot,and the software is developed based on C language,completes the main control system The software is developed based on C language,And the main procedure design and control board design of the control system are accomplished.Also,the system’s hardware and software parts are improved and some anti-interference measures are proposed.In order to study the dynamic characteristics of the hydraulic-electric control system,this paper used AMEsim software to build a hydraulic simulation model,and the simplified models of two hydraulic systems were established based on the practical working situations in the field to study the dynamic reaction curves of the hydraulic-electric control system of the tractor under lifting and side tilting conditions respectively.The simulation results show that the system reaches the maximum value after 3.2s piston rod stroke under lifting condition,and the target displacement of the piston rod under side tilting condition is within ±5mm after the adjustment of PID controller,which can meet the actual operation requirements.In order to further verify the correctness of the control strategy and control algorithm,this paper built a rear suspension electric-hydraulic control system test bench based on the rear suspension mechanical part of the prototype,and carried out the lifting test and position control test of the rear suspension agricultural implements.The test results show that the tractor rear suspension electric-hydraulic control system can effectively complete the position adjustment of agricultural implements,and the actual position error can be controlled within 6%.