Study On Virtual Test Platform Of Hydro-Mechanical Continuously Variable Transmission

With the acceleration of the development of agricultural mechanization in China,tractors equipped with Hydro-Mechanical Continuously Variable Transmission(HMCVT)have advantages such as good economy,strong power,and transmiting large power while achieving stepless speed change,So it became the focus of scientific research.However,there are many problems in the research of HMCVT,such as high cost,long period and limited test site.Using virtual test technology to build a virtual test platform of HMCVT can effectively solve the problem of test difficulty.The digital virtual test platform makes the test get rid of the limitation of the site,shorten the test cycle and save the test cost.The research on the test platform of HMCVT is of great significance to the development of HMCVT.In this paper,firstly,the transmission characteristics of HMCVT equipped on a certain type of wheeled tractor are analyzed,and the focus of relevant research is understood.Referring to the structure and control principle of tractor equipped with HMCVT,combining with the needs of the test,the functions of the virtual test platform are formulated,the overall planning of the platform is completed according to the functional requirements,and the scheme design of the platform is completed according to the planning.According to the module and parametric modeling method,The virtual test platform is divided into power source module,HMCVT module,main transmission module and tractor traveling mechanism module.The power source module takes the test data of the engine as the training sample,uses the BP neural network method to establish the mathematical model of the engine,and the other modules use the dynamic principle to build the mathematical model.Use the Simlink and Simscape modules in MATLB to build the simulation model of each module in the software.The design target function of the test platform is realized through the humancomputer interface established by GUI module in MATLB.The logic judgment module is set to prevent the conflict between human-computer interface and controller input signal,and the priority of signal input is established.Finally,the virtual test platform of HMCVT is designed.This paper analyzes the transformation of the working state of the clutch in the process of changing the HMCVT,forward the rules of smooth ranges shifting,establishes the logic control model of ranges shifting,and carries out the virtual test of changing the section of the HMCVT with two structures on the virtual test platform.The test results of the two structures are consistent,which shows that the virtual test platform has strong generality,and can complete the mechanical properties of the HMCVT of control performance by relevant tests in the early stage.