Research On Key Technology For AMT System Of Heavy Truck

In recent years, AMT has become a new type of automatic transmission technologies, which plays an important role in the family of the automatic transmission and has been widely concerned in the world. AMT has lot of advantages, such as higher efficiency, lower manufacturing cost, higher cost performance and smaller equipment investment; in addition, its production can follow the existing manual transmission production lines. So, AMT is very suitable for the development of Chinese automobile industry, and it has very good industrialization prospects and wide applications range. Despite AMT technology of the heavy trucks has been researched in the worldwide and has achieved a product-promotion,system stability and reliability continues to be the key technologies and difficulty in its development process because of the strong compression of gas media, AMT system owner characteristics and technical complexity, the vehicle start, shift. The research in this paper is based on the focus project "Commercial Vehicle AMT" of China FAW Group Corporation R&D Center. The in-depth systematic theory and experimental research work have been done for a number of control technical problems of heavy truck AMT system and its pneumatic actuator, and the control strategy has been researched using the intelligent control theory and methods.This paper introduces three kinds of typical automatic transmission characteristics, development status and the main applications control method of the automatic mechanical transmission in the worldwide, besides, this paper describes the development prospects, technical problems and practical significance of heavy truck AMT system. So, the academic, practical application background and necessity of the research in this paper has been expounded.The model of the engine toque is based on the multiple linear regressions. What's more, the regression coefficient is for the first time checked, and the independent variable, which plays a faint role in the result, is eliminated. It firstly tests the degree of fitting by means of multiple correlation coefficients, which is modified by the degree of freedom, and thus it avoids the phenomenon of blind increase of the independent variable, which is the result of the pursuit of the fitting effect. The vehicle model is based on the clutch slipping stage and fully combined stage, which has been tested the validity by vehicle experiment of the FAW heavy truck which preparing assembly AMT system.The manipulation in AMT of research truck is electric control-pneumatic actuator. The composition and working principle of clutch pneumatic actuator, selection pneumatic actuator and shift pneumatic actuator is described in this paper. The various pneumatic actuator mathematical models of FAW heavy truck AMT system has established firstly based on gas dynamics theory and its work process has been simulation. The model correctness of clutch pneumatic actuator has been proved using clutch static test bench, in addition, the control difficulties and existing problem have been analyzed, which determined the research direction and content for further in-depth study on the clutch Intelligent Control Method.The dynamics of vehicle starting has been analyzed in the paper. The subjective and external estimation method has also been introduced. The clutch control objectives of vehicle start has been confirmed with fully studying the influence on the heavy truck start based on the throttle, engine initial speed, clutch engagement speed and vehicle load. As the vehicle started will wear clutch, especially for heavy truck full loaded, so the clearance of the clutch driving disk and driven disk is dissimilar in each starting, in addition, the consistency of Diaphragm clutch is not Satisfactory because of clutch production process limits in our country. So there haven't condition on measure the clearance of Diaphragm clutch driving and driven disk as clutch has been separated. But the synchronization time can been gained by speed sensor. So, the fast engage moment for eliminating the clearance of clutch driving and driven disk has not been considered and the fast engage moment after synchronization has been research. The control of heavy truck start has two modes. Before clutch driving and driven disk synchronization, the start controller has been designed for clutch engagement. After clutch driving and driven disk synchronization, the open loop control of clutch pneumatic actuator has been done for engaging clutch with the maximum speed.The start controller designed in this paper has three layers. In the first layer, choosing the accelerator pedal displacement and its rate of change as input variables, using intelligent fuzzy reasoning algorithm, the start intention of the driver can be gained. In the second layer, choosing the driver intentions and the speed difference of clutch driving and driven disk as input variables, choosing clutch engagement speed as output variable. In the third layer, the clutch bearing displacement has been chosen as the control objective of the clutch pneumatic actuator. The control of clutch bearing displacement achieves by the pneumatic actuator, which precise control is more difficult because of the non-linear of high-speed switching valve dead-zone, power supply voltage fluctuations, gas strong compression and diaphragm spring strong non-linear and so on. In the simulating and testing on the clutch pneumatic actuator, when the direct feedback control was used on the clutch solenoid valve, it can be found that if the clutch cylinder piston target displacement is smaller, the effect of piston displacement is better because of the cylinder pressure, piston speed and acceleration is smaller. And if the clutch cylinder piston target displacement is bigger, the system overshoot is bigger because of the clutch cylinder pressure, piston speed and acceleration is bigger. The section dynamic control method is designed to control the clutch pneumatic actuator. When the clutch bearing target displacement is small, the closed-loop control has been used to control the clutch pneumatic actuator. And if the clutch bearing target displacement is larger, the dynamic look-up table method has been used to compensate the intake and exhaust gas for clutch cylinder, and the simulation and test both confirms its validity. The Constant speed control strategy has been used on the engine, and set engine speed threshold and maximum target speed value. The fuzzy controller has been used on accelerator pedal, choosing engine speed and its rate of change as input variables, using intelligent fuzzy reasoning algorithm, the change of accelerator pedal displacement as output variable. The control strategy can reflect the intention of the driver and decrease the Friction power. The process of vehicle normal start, 5% and 10% initial slope start with empty and full load has been separately simulated by the simulation model in this paper. the smooth start of heavy truck also approved the start control method in this paper is validity and the section dynamic control method which in the bottom of the start controller can meet the control needs of the clutch bearing displacement, it is strong practical.The control effect of the control system is affected in a large extent because of the characteristics of controlled object. The different characteristics of two diaphragm spring clutches have been researched as controlled object, simulation and bench test results of following sine wave and Triangle wave were compared, which provides the theoretical guidance of selection of diaphragm spring clutch for the heavy truck AMT system.The shift process dynamics of heavy truck AMT system has been analyzed. The best dynamic and best economy shift rule has been calculated. For heavy-duty truck load large and shifting power interruption time is longer, the vehicle speed loss during shift process has been calculated for the first time based on the traction and driving resistance before shifting and dynamic corrected the shift rule by considering the vehicle speed dynamic loss compensation before shifting. The minimum acceleration thresholds after shifting has been set by calculating the driving force and driving resistance after shifting and make up the heavy trucks less power after shifting. The vehicle mathematic model of before and after shifting has been built and the shift strategy has been designed based on the research shift operate of skilled driver. In addition, a new type of gear detection sensors has been designed to detect selection and shift position. The operation of engine, clutch, selection and shift Pneumatic actuator has been coordinated during shifting. Truck continuance shift working process has been simulated by the best power and economy shift rule and truck test has been done by FAW AMT prototype to examine the result of theoretical studies. The result shows that the shift rule and the shift control system in this paper has achieved a more satisfactory result and the simulation model also has a strong practicality.