Study On Simulation Of Hydro-Mechanical Continuously Variable Transmission And Control

Hydro-mechanical Continuously Variable Transmission is used extensively for the constructions, such as building, mining, highway, railroad, port and the military engineering etc. They have important function to ease the labor intensity and lower the engineering cost, and relate directly to the national construction project. The work environment of the engineering machine is worse and the load is continual variety, so the engineering machine requires higher efficiency in energy using and transition. It is importance to raise the economy energy, operability, safety and the driver's comfort of the engineering machine.Generally, automatic transmission of the engineering machinery is required to improve the performance of the power system because of their rugged, complicated and variable working conditions. The transmission system of engineering machinery is generally hydrodynamic-mechanical transmission system to improve the adaptive abilities to load. The control system for hydrodynamic-mechanical transmission can adjust ratio automatically according to the change of work condition, so it is able to achieve variable transmission in a certain rang. But transmission ratio is not continuous between the multi-rang. In the course of changing shift, there is impact to make driver feel uncomfortable, and rotation speed of the engine is unsteady that the exhaustion of the waste gas can be increase. In addition, the efficiency of hydrodynamic-mechanical transmission is lower, thus the power and economic features of construction vehicle are affected largely. The hydraulic transmission can provide the stable speed, and can be control accurately that variable transmission is able to come true. But the efficiency of hydraulic transmission is lower. Hydraulic transmission of high-power construction machinery vehicle is replaced by hydrostatic-mechanic transmission which has the perfect performance of continuously variable transmission and could realize the large power transmissionhigh efficiently. Hydrostatic-mechanic transmission makes the most of the power of engine and guarantees the driver to be comfortable at the same time. Hydrostatic-mechanic transmission has become leading direction in high-power construction machinery developing. Tied with the above discussion and analysis, the dissertation, aiming at the problems of that the drive ratio of construction vehicle is discontinuity and the transmission efficiency is lower, investigates the design of hydrostatic-mechanic transmission system. By incorporating the engine, hydro-mechanic transmission gear-box and load to a dynamic system, the theoretical research of the performance in power and the economic features was carried on. In pursuit of promoting utilization ratio of power on vehicular transmission, the dissertation has designed the control system which controlled the pump to constant rotation by adjusting pump displacement according to the changing rotation of engine. Study of this dissertation is as following:(1) The dissertation analyzes the evolution background and present research situation of hydrostatic-mechanic transmission technology in vehicle oversea and inland. And the application productions of the variable transmission in construction machinery are introduced. The key technology of hydroc-mechanic transmission system is analyzed, and then the developmental orientation of hydrostatic-mechanic transmission for vehicle is made certain.(2) Aiming at the transmission demand for construction vehicle, a scheme of hydrostatic-mechanic transmission was designed, and the characteristics were analyzed. The control method used in the course of the transmission system has generally summarized. According to working conditions and characteristics, the matching method for the co-operation characteristic of engine and variety of load is developed. The control scheme can improve the power performance and economic feature of construction vehicle. The control methods for components, which are controlled, are analyzed.(3) The dissertation has set up mathematics model and transmitted function of engine, variable volume pump, valve and cylinder, and also has simplified the model according to request of the simulink. By means of computer simulation,the computer models of intelligent control on hydrostatic-mechanic transmission for construction vehicle are set up. The computer Simulink experiment was used simulink module of Matlab on the control system. The simulink result indicates that the fuzzy control system is effective to steady rotate speed of the engine when load has variety.