Study On Electro-hydraulic Control System For DCT

As the symbols of the development of the vehicle technology, both vehicle operation automatization and electronics in vehicles are the interminably pursued goals. Automatic transmission gearbox is the typical combination. It has many advantages such as easing the driver's labour, increasing the life of the powertrain, improving the productivity, economy and so on, and is used widely.Automated Manual Transmission (AMT) has the advantage of high efficiency, low cost and easily manufactured. So the current manufacture equipment of manual transmission can be adequately used and particularly suitable for companies in China most of which use manual transmission manufacturing equipment.AMT is not powershift transmission and there is interruption of torque during the shift. So the launch performance and shift quality of AMT cannot be compared to Automatic Transmission (AT) to some extent. Powershift AMT is the innovation and change of the conventional AMT. It inherits the advantage of high efficiency and low cost of AMT and eliminates the power interruption of AMT during shift, so largely improves the market competitiveness. The current powershift AMT has two types: auxiliary torque AMT and double clutch transmission (DCT).DCT is a new generation automated mechanical transmission. It inherits the advantages of conventional AMT, such as high transmission efficiency, compact structure, low cost and so on, overcomes the problem produced by shifting with interruption of torque transfer ultimately, improves comfort ability of shift obviously, ensures vehicles a good power.This thesis analyzes the system theory of DCT; analyzes the characteristics of clutch pressure control; establishes the math model of clutch pressure control system; carries out the simulation in AMESim software; Completes the test of clutch hydraulic control system.Firstly, I introduce the development-history and prospect of DCT, and analyze the working characters of DCT and the technology of electro-hydraulic proportional valve. Then I point out the aim, main content and significance of this thesis.Secondly, I analyze and compare the structure characteristicsof single middle shaft DCT and double-middle shaft DCT, and discuss the power flow and shift process in the case of shift from first speed to second speed. Then I introduce the system structure and the basic control method of DCT's clutch hydraulic system. I illustrate the structure and working principle of valves that we used. The basic control strategies and the control flow chart are shown; Furthermore, I make out the basic demands of clutch hydraulic system. These are the basis of the DCT control systems.Thirdly, I study on the clutch hydraulic system, analyze the shifting process of DCT and math model, introduce the control methods of clutch hydraulic pressure during filling and draining oil of clutch .In the end, I decide to use proportional pressure valve to control the clutch pressure .I introduce the structure, components, working principle and characters of proportional pressure valve .I formulate out the clutch hydraulic control system math model, and derive the transfer function of hydraulic cylinder controlled by valve, and simplify the transfer function according to the load ;analyze the stability of system. A model of the clutch hydraulic system with DCT has been established with AMESim, finally the simulation result is shown and analyzed in depth. From the result, we can draw the conclusion that during the filling and draining oil, good static and dynamic characters of oil pressure of clutch hydraulic system can be obtained with proportional pressure valve close-loop control system through PID control segment.Finally , Based on the research of theory and simulation ,I complete the test of clutch hydraulic control system . I design the experiment platform of test and testing method. Then I summarize and analyze the experiment's result. The result of experiment shows that the proportional pressure valve can guarantee the steady increasing clutch hydraulic pressure and is suitable for the demands of clutch pressure control. From the experiment, I obtain some valuable conclusions, which has laid the foundation for future research and development of DCT. The experiment result shows that the math model can reflect the static and dynamic pressure of the clutch hydraulic system.In conclusion, I do research in the hydraulic system and thecontrol of clutch with proportional pressure valve. In this paper, my work will be valuable to the further research and development.