Design And Performance Research Of AMT Shift System Based On Direct-drive Technology

Automated mechanical transmission(AMT) is converted from conventional manual transmission, it has a high transmission efficiency, low cost and simple structure. In recent years, more and more research institutions at home and abroad have paid attention to the study of electric AMT, and the direct-drive technology has begun to be used.In order to improve the shift quality of electric AMT, a class of shift system based on direct-drive technology is proposed in the thesis. Two degree of freedom electromagnetic actuator(2-DOF EMA) and servo synchronizer are developed.2-DOF EMA assembles the rotary and linear movement in an overall structure and the movement is independent of each other. Servo synchronizer has the function of self-energizing. These technical measures can improve the compactness of the system and the shift quality of AMT, at the same time, the shifting energy loss happened in the process of gear switching is reduced greatly. In this thesis, the key technologies of shift system based on direct-drive technology are researched by theoretical analysis, simulation and experiment as the following:(1) The technical program of AMT shift mechanism based on direct-drive technology was determined. Consider the general requirements of automatic transmission technology for shift mechanism, two programs of AMT shift mechanism were designed by the optimal targets of shift quality and compactness respectively. The shift mechanism program driven by two degree of freedom actuator that the internal structure of traditional manual transmission was smaller altered had been chosen as the main technical program in the last.(2) Two degree of freedom electromagnetic actuator based on electromagnetic conversion characteristics was developed. Consider the drive requirements and compactness of AMT shift mechanism, the subject independently developed a2-DOF EMA who assembles the rotary and linear movement in an overall structure and has a high power density. The static and dynamic characteristics were researched by simulation analysis and bench testing after the system prototype had been developed.(3) The detailed kinetic models of gear shift process were built and the performance of shift mechanism was simulated. The gear shift process is divided into several stages on the basis of the analysis for the principles of transmission, and the function of gear shift timing overlap for AMT shift mechanism was discussed. At these points, the performance simulation of AMT shift mechanism could be completed based on MATLAB/Simulink and the relationship between the shift parameter and the performance of shift mechanism was researched.(4) The influence of strength and stiffness of shift fork on the shift force loading rules was analyzed and the determination principle of the maximum instantaneous force was discussed. The finite element analysis model of shift fork based on ABAQUS was established in the thesis. It can obtain the maximum instantaneous force output by driving device under the strength requirement of shift fork and correct the shift control strategy according to the stiffness analysis results of shift fork.(5) An AMT shift system based on direct-drive and self-energizing shifting system was developed in the thesis, it has the function of self-energizing and improving the robustness of shift system. For the problems of AMT shift system caused by direct-drive technology, the research designed a servo synchronizer with the function of self-energizing. Respectively, the feasibility and functionality were verified through mechanics and energy conservation. And then, the sample of servo synchronizer is developed. The maximum instantaneous force provided by self-energizing shifting system is smaller than traditional shifting system in the same shifting quality, and the shifting energy loss can be reduced greatly. The ability to resist external disturbances is improved for using AMT shift system based on direct-drive and self-energizing shifting system. It has laid a good technical foundation for decreasing the volume of driving device and reducing the difficulty of shifting control system design.(6) The universal test bench for AMT shift system based on2-DOF EMA was constructed. The feasibility, functionality and versatility of AMT shift system based on direct-drive technology were verified in the last. The function of gear shift timing overlap for AMT shift system using2-DOF EMA as driving device was verified under the suitable shift control strategy. The feasibility and versatility of the new shift system were verified through the experiments of changing shift parameters. Comparative the test results of the two AMT shift system tested before and after the test bench was modified, thus, the feasibility and functionality for direct-drive and self-energizing shifting system could be verified. The results show that the2-3gear shift time of family car is controlled in200ms and the synchronization time is controlled at107ms when the rotary speed difference is500r/min, the moment of inertia is0.03kg-m2and the maximum instantaneous force reaches1000N. In this case, the maximum degree of shift shock is179.5rad/s5and the friction work per unit area is0.057J/mm2. It gets a smaller shift shock and meets the requirement of synchronizer life, the power interruption time of gear shift process is deeply shortened. The force amplification coefficient of the direct-drive and self-energizing shifting system is nearly1.542, at this moment, the maximum instantaneous force provided by shift driving device can be reduced nearly35%. It has laid a good technical foundation for decreasing the volume of driving device and reducing the difficulty of shifting control system design.