Study On Start And Shift Jerk Character Of AMT

With the development of auto-transmission technology and people's pursuit of power and comfort, more and more attention has been paid to shift quality. A perfect shifting process should be smooth, quiet, harmonious, natural and so on. Today, shift quality has become to be an important branch in the field of auto-transmission. The content of shift quality research includes (1) comfort index, such as shift jerk caused by the change of transmission ratio and shift noise caused by the fluctuation of engine speed and vibration; (2) fuel and emission index which put environment and resources into consideration; (3) part-longevity index which will determined by the maximal load on the parts of transmission system during shifting process; (4) manipulatory index which reflects in what extent the responding speed satisfies the driver's intent. This thesis, supported by"Research on the Dynamic System of Shift Quality Synthetic Evaluation"-National Science Foundation of China (50505014), focuses mainly on the research of jerk character during start and shifting procress of AMT.Automatic Mechanical Transmission is non-power shift device, which produces jerk during gearshifts because of the torque interruption. So, the smoothness performance of AMT is worse than that of other transmissions. The research on shift quality is the key to develop AMT products. As an important part of shift quality, it is very significant to research on shift jerk. The aim of this paper, based on AMT car, is to find out the influence to shift jerk during shifting process by each parameter.AMT is fixed in the traditional coaxial transmission and dry clutch on the basis of the electronic control unit at the core, through the implementation of the hydraulic control system of separation and engagement of clutch, the election shift operation and the regulation of the engine throttle to achieve start and shift automation.This paper will analysis and study various factors, which cause shift jerk against the vehicle start and moving two shift working conditions ,focused on AMT shift control of the clutch engaging law and shift schedule. And a dynamic simulation of the vehicle is established through the study of start and moving two shift working conditions, so as to laid the foundation for the research of shifting quality evaluation method.This paper focus on the following aspects:(1)This thesis systematically describes shift jerk theory and its evaluation index, analyzes vehicle start and shift process. Through experiment, velocity performance of engine is obtained, and all performance curves of engine are acquired through calculation. On the basis of above study, the reasonable shift schedule and control strategy of the AMT are established. Clutch diaphragm spring performance, such as burthen performance, abruption performance, engagement performance, abrasion performance etc, are studied through experiment. Finally torque transferring performance of clutch is obtained by calculation.(2)According to the automobile travel dynamic equation, the dissertation has established MATLAB/Simulink simulation model of engine, clutch, transmission, final drive, surface resistance model, and vehicle model, through analysis of simulation result, the jerk character graphs during start and shift process are obtained. The emphasis in this paper lay on the clutch engaging velocity and throttle, which influence shift jerk. The simulation puts forward new research method for the study of the AMT jerk character.(3)This thesis analyzes the factors causing shift jerk during the shifting process and the reason how the shift jerk produced. The dissertation uses jerk as restrictive conditions in the actual control process, thus analyzes its engagement characteristics in the theory, establishes preferable AMT clutch engaging dimension and velocity, and puts forward control strategies of engine and clutch. (4)On the basis of simulation analyse and control strategies, through experiment, the article indicates that the simulation model and gear-shift schedule designed in the article is reasonable, thus the shift performance are improved.Through the simulation analysis during start and shift process, we can get the following conclusion:(1)In the course of clutch engagement, clutch engagement speed is the main impact factor of the jerk.(2)In the drive process, clutch is rigidly connected, the torque that clutch transfers is engine torque, the produced jerk mainly decided by the engine angle acceleration change velocity and engine output torque change velocity .(3)In the course of start, outside resistance of the vehicle increases from zero to the most, but in the course of shift , outside resistance basically keep unchanging, so the same clutch engamement speed produces larger jerk in the start than that in the shift process.In the end of this thesis, a series of comparison tests have been made to validate the conclusion above. The testing car starts up with 1st gear, and accelerates to the highest gear, then reduces to the lowest gear. Through changing the throttle opening and the shift rule, a series of data in different work conditions can be obtained. After comparing and analyzing, the conclusion mentioned above can be validated.