Research On Design And Control Strategy Of Hydraulic Mechanical Continuously Variable Transmission For High-power Tractor

Hydro-mechanical Continuously Variable Transmission(HMCVT)is a compound continuously variable transmission that combines hydraulic transmission and mechanical transmission.Compared with ordinary transmissions,HMCVT has the advantages of realizing continuously variable transmission,large transmission power and high transmission efficiency.Applying HMCVT to tractors can significantly improve the fuel economy of the tractor,improve the performance of the tractor,reduce the labor intensity of the driver,and reduce the cost of agricultural development,which plays a huge role in the development of my country’s agricultural modernization.In this paper,HMCVT is studied from the aspects of transmission scheme,parameter design,simulation modeling,control strategy and so on.Firstly,the basic principle of the HMCVT transmission system is explained,and the characteristics of the components of the HMCVT are analyzed.Finally,the transmission scheme of the hydromechanical continuously variable transmission of the double planetary converging mechanism in the split-moment convergent speed type and the variable pump-fixed motor is determined.According to the basic parameters of the tractor and different working speed ranges,a five-stage hydraulic-mechanical stepless transmission system is designed to determine the transmission ratio range of each working section of HMCVT,and analyze the speed ratio,power split ratio and efficiency characteristics of each working section of HMCVT,To determine that HMCVT meets the tractor’s travel speed requirements and realizes continuously variable transmission.Through the MATLAB/Simulink simulation software,the simulation model of each transmission element is established,and the simulation model is combined into the HMCVT transmission system simulation model and the simulation test is performed to verify its output characteristics.Aiming at the shortcomings of the HMCVT output characteristics,suitable HMCVT control strategies and control logics are proposed to improve the HMCVT output accuracy,improve the stability of the driving speed of the tractor during operation,and enhance the intelligence and efficiency of the tractor in response to load and environmental changes.Choose PSO-PID control algorithm for control strategy,design PID controller based on PSO algorithm,and join HMCVT simulation system for simulation test.