Roll-Down Process Development for Transmission Garage Shift Quality 2001-01-1500

A roll down methodology has been developed to predict the driver's seat track fore-aft acceleration response using measured half shaft torque time histories and an analytically predicted vehicle sensitivity function suitable for transverse front wheel drive powertrains. The predicted vehicle sensitivity function (a frequency response function) relates the transmission torque applied to the drive axles to the seat track fore-aft acceleration. An experimental procedure was developed to measure the in-situ vehicle sensitivity function. The experimental data was used to correlate the analytical model. The testing results have shown that in the frequency range of the “garage shift” that the vehicle body can be represented as a rigid body. A Nastran model utilizing a rigid body representation of the body and powertrain is used to predict the vehicle response to the torque transient. This simplified approach enables powertrain designers at the concept stage of development to predict the seat track fore-aft acceleration using a concept mounting, and “tune” a design to minimize the vehicle sensitivity to “garage shift”. The analytical model was correlated to a baseline vehicle, then applied to a powertrain that utilized a different powertrain mounting configuration and the updated model was used to predict the resulting seat track fore-aft acceleration.