Characteristics Study Of Closed Hydraulic System In The Hydro-mechanical Continuously Variable Transmission

Hydraulic mechanical variable transmission(HMT)is a kind of double power flows transmission with characteristic of high efficiency and stepless speed variation,which is compounded by hydraulic and mechanical transmission.The HMT conventional shift will cause speed fluctuations and short-term power interruption.The model identification and experimental study of HMT closed hydraulic system will help to improve the quality of shift.This paper carried out the study that the HMT closed hydraulic system identification and dynamic characteristics of the HMT closed hydraulic system.The main research contents included: First,it carried out the mathematical mechanism of variable displacement hydraulic component,the variable displacement hydraulic component module have been conducted on the basis of the theoretical modeling;then combined cavity model,fixed and variable displacement hydraulic component models,the transfer function of hydraulic stage and hydraulic mechanical stage of HMT closed hydraulic system been builded.It also provided prior knowledge for the system identification.Second,according to the transfer function of HMT closed hydraulic system,the system identification experiment reasonably designed.The experiment data been analysed by Matlab system identification toolbox.Then ARX and ARMAX model were identified by using the least square method and the extend least-square.Third,the dynamic response characteristics of HMT closed hydraulic system been experiment.The effect of flutter current on the dynamic response of HMTclosed hydraulic system been studied,the best flutter frequency and flutter amplitude been obtain.And the system step response experiment was experimented.The experimental results showed that the transfer functions by identification can reflect the response characteristics of HMT closed hydralic system.