Analysis of start-up transient for a powertrain system with a nonlinear clutch damper

• Develop and experimentally validate a new 4DOF nonlinear powertrain model for transient events within the clutch damper and transmission during the engine start-up.
• Correlate the interactions between multiple transient events using new metrics.
• Examine nonlinear characteristics and find the transient envelope of the clutch damper using harmonic balance method for a slowly varying process.
• Develop analytical formulas to approximate the transient amplification for a rapidly varying process.

The transient vibration phenomenon in a vehicle powertrain system during the start-up (or shut-down) process is studied with a focus on the nonlinear characteristics of a multi-staged clutch damper. First, a four-degree-of-freedom torsional model with multiple discontinuous nonlinearities under flywheel motion input is developed, and the powertrain transient event is validated with a vehicle start-up experiment. Second, the role of the nonlinear torsional path on the transient event is investigated in the time and time−frequency domains; interactions between the clutch damper and the transmission transients are estimated by using two metrics. Third, the harmonic balance method is applied to examine the nonlinear characteristics of clutch damper during a slowly varying non-stationary process in a simplified and validated single-degree-of-freedom powertrain system model. Finally, analytical formulas are successfully developed and verified to approximate the nonlinear amplification level for a rapidly varying process.