The degradation of the frictional characteristics of a wet clutch, with repeated engagements throughout its full life, alters the dynamic responses of the powertrain, which weakens the effect of the control system with a fixed control law. To solve this problem, cooperative effects of control parameters on the dynamic responses of the vehicle start-up process throughout the full life cycle of the wet clutch were studied. First, the degradation law of the wet clutch frictional characteristics was obtained with a test rig, and the life cycle of wet clutch was divided into three stages, based on statistical data from the automobile factory. Then, the powertrain model of start-up process was developed and verified with a test. Finally, the cooperative effects of the hydraulic-pressure rising rate and the initial relative speed on the dynamic responses of the vehicle powertrain at the three stages of the clutch life were studied. The results revealed that the control parameters have different influences on the dynamic responses of the vehicle start-up at the different stages of wet clutch service life. To obtain good start-up performance, different optimal combinations of controllable parameters should be adopted at different stages of the wet-clutch service life.
