Research On The All Phase Dynamic Characteristics Of Hydro-mechanical Continuously Variable Transmission In The Special Vehicle

Hydro-mechanical Continuously Variable Transmission(HMT)is a new type of composite stepless transmission device which is composed of hydraulic transmission and mechanical transmission.it is one of the ideal transmission forms of high-power vehicles because of its large transmission ratio range,high efficiency is and the stepless speed regulation.HMT full power switching method can fundamentally solve the power interruption of HMT during switching,and improve the dynamic characteristics of HMT during the switching process.Based on the full power switching method,this subject makes the HMT full-stage model and the HMT full power switching controller model including full power switching and speed regulation to research dynamic characteristics.(1)Analyzed the full power switching method,which takes the target clutch zero-speed difference moment as the ideal timing for shifting.Calculated the speed characteristics,torque characteristics and power flow characteristics.(2)Established HMT full-stage simulation model,including diversion mechanism model,hydraulic flow mechanism model,mechanical flow mechanism model,confluence mechanism model,clutch model,vehicle model,etc.Simulated and test the whole process of HMT speed regulation,The accuracy of the model was verified by comparing the test results and simulation results of the main parameters including hydraulic circuit pressure,fixed displacement element speed,output speed and so on.The results show that the HMT full-stage model built in this paper can accurately describe the dynamic characteristics of HMT speed regulation and full power switching.(3)Analyzed the working process of HMT full power switching;calculated the key parameters of the full power switching process;combined with incremental PID,designed the segmented speed ratio tracking method;used PSO algorithm to optimize the PID parameters,build the HMT controller model.Use the existing controller model and HMT full-stage model to simulate different speed ratio tracking conditions,and the simulation results show that the controller model can achieve full power switching and speed ratio tracking speed.(4)Using the HMT full-stage model built in this paper,analyzed the influence of the output shaft inertia on the HMT shift process and output torque and HMT input torque and transmission efficiency,when loads and transmission ratios are different.