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Automatic transmission gear changes are transient disturbances in a non-linear system, during which the effective ratio of the transmission is continually changing. In addition, vehicle characteristics can very strongly influence customer perception of the shift event. Further, the interface elements between the vehicle and powertrain are often crucial in determining the quality of shift feel. This paper presents a validated CAE method that employs the ADAMS software to predict the intricate dynamics of the vehicle response due to transmission shift events. First principles of the transmission modeling elements are described. Model simulation results are compared to vehicle test data. A method to quantify the customer's perception of vehicle shift quality is discussed. Model simulation results for a FWD vehicle application are also analyzed.

A low-frequency vehicle shuffle can be excited when a reversal of torque occurs in a vehicle's drivetrain. It usually occurs during a throttle tip-in or tip-out event, or a static engagement shift event. This drivetrain shuffle vibration can introduce a vehicle fore-aft vibration that may affect the customer satisfaction of ride comfort and/or powertrain performance. Vehicle test data of the seat track acceleration from a 30 MPH wide-open-throttle tip-out event suggested a strong coupling between the CVT drivetrain shuffle and vehicle fore-aft vibration. An ADAMS based CVT model was developed and integrated into a full vehicle model for dynamic simulation of this vehicle shuffle issue. CAE DOE studies were performed to identify key vehicle and powertrain design parameters that could directly impact the vehicle shuffle vibration. Experimental tests were performed to verify the CAE design improvements of the CVT vehicle shuffle vibration.