Modeling and Analysis of Engine Torque Modulation for Shift Quality Improvement

An engine torque modulation methodology is developed for use in engines equipped with electronic throttle control, ETC. It is shown through simulation that an engine with ETC is capable of following a transmission torque modulation command that includes a linearly increasing torque during the torque phase, a torque reduction during the inertia phase and a post-shift torque increase. It is also shown that such a strategy can be used to minimize the transmission output torque variation during a shift. The impact of engine indicated mean effective pressure, IMEP, variation on vehicle longitudinal acceleration is analyzed using Monte-Carlo simulation. It is shown that the IMEP induced variation in the vehicle acceleration is largely due to end of shift engine torque output timing errors. It is then recommended that during a shift the engine IMEP variation be held to a one-sigma variation of three percent or less. Appendices A and B summarize the derivation of a low order planetary gear driveline model that is used to illustrate the torque relationships and dynamics associated with shifting an automatic transmission.