Research On Modeling And Gear-shift Schedule Of Automatic Transmission

Internal automobile industry of China is in developmental period and domestic cars are increasing gradually of late years. As a result of cost restriction, at present the automobiles produced in china are almost equipped with manual transmission (MT).On the one hand, the automobile equipped with MT will increase Drivers' labor intensity, on the other hand, it does not favor the traffic safety. The automobile equipped with automatic transmission (AT) has smooth gearshifting and convenient operation. Moreover, it can automatically gearshift in term of optimal occasion, redounding to the improvement of dynamic performance and fuel economy, thus the automobile with automatic transmission specially suits amateur driver. In order to satisfy the amateur drivers' request for simple handle, many domestic manufacturers have considered AT as their development direction.In the course of AT researching, developing and matching with the entire vehicle, the characteristics of torque converter and transmission, together with the integral performance of the power train which mainly consists of engine and automatic transmission, need to be analyzed.This article has elaborated the input characteristic and the output characteristic when engine and torque converter work together, which is based on analyzing AT's structure and working principle. Furthermore, the article has discussed several computational method of the input and output characteristics of torque converter cooperating with engine, and analyzed the match question between the engine and torque converter, obtained torque converter's static and dynamic mathematical model by analyzing working characteristic of torque converter's various parts. The kernel of automatic gear shifting is gear-shift schedule and gear shfting is executived according to the control parameters. The dynamic schedule and economic schedule are designed according to the acceleration characteristic and fuel consumption. With provision for operating requirement, the general schedule is designed, too. Finally, according to the automobile travel dynamic equation, this article has established MATLAB/Simulink simulation model of automatic transmission system, established simulation model of the shift logic of optimal shift schedule with MATLAB/Stateflow, and carried on thesimulation analysis, confirmed the design plan's validity. The simulation result indicates that the simulation model and gear-shift schedule designed in the article is reasonable.