Study On The Control System Of Hydro-Mechanical Stepless Transmission

Hydro-mechanical Continuously Variable Transmission combines the advantages of mechanical transmission and hydraulic transmission, not only can realize the function of continuously variable transmission,but also can increase the transfer power and efficiency of stepless transmission, so it has a wider application. This technology has already beed commercialized in the 60/70 20th century in western countries, and was used on military vehicles and heavy vehicles. In China, the current study of HMCVT is still in theory stage, there were significant gaps compared to abroad. Therefore, the study and research in HMCVT has a great significance.This dissertation analyzes the working principal and operating characteristics of HMCVT, making the East Red C702 crawler tractor as an installed object, designed a three-segment/arithmetic type HMCVT. On this basis, the main work which have been done as follows:(1)Give a detailed analysis of the working principle and characteristics of the diesel engine used in construction vehicles, design the transmission ratio contorl program of HMCVT, which can realize the transmission ratio automatically adjust when the load changes, with the purpose of the best match between the engine power and the load power, and to improve the power efficiency of the engine;(2)Give a comprehensive analysis of the advantages and disadvantages of various control algorithms, and HMCVT work characteristics, design the "segment change controller" which can control the segment changes automatically and the "adaptive fuzzy PID controller" which can control the variable pump to change its displacement automatically;(3)Use AMESim and Matlab/simulink established the HMCVT structure model and controller model,use the combined simulation technology give a test study of the HMCVT structure and controller. Simulation results show that the "segment change controller" and "adaptive fuzzy PID controller" can work properly to adjust the transmission ratio (change the segment automaticaly or change the displacement of the variable pump automatically)when the load changes, the purpose of keeping the engine speed/realizeing the reasonable march between engine power and load power was achieved.