Study on the improvement of the shift characteristics for the passenger car automatic transmission

Dynamic simulation techniques are developed to analyze the shift characteristics of the vehicle powertrain with automatic transmissions. In this study, the mathematical modeling of powertrain components such as engine, clutch system, planetary gear system and road load, is presented for the simulation. The clutch engagement condition, which determines the degree of freedom of the system, is also proposed. By using a detailed nonlinear model of torque converter, it is possible to accurately analyze the extremely transient state such as the shift. Dynamo-based experiments are carried out to prove the validity of the proposed simulation techniques. Using the developed simulation program, the effects of the dynamic design variables and the control conditions, focused on the shift, are evaluated to improve the driving comfortability.