Abstract: Clutch engagement process consists of three sequential phases, i.e., open, slipping and stick (locked). The task scheduling period of the clutch control task should be selected carefully in case that the improper discretization leads to instability and deteriorates the engagement quality. An integrated approach which considers both control performance and real-time scheduling aspects is applied to allocate task scheduling periods. Firstly, the model of a closed-loop control system for a powertrain with a clutch element is developed and discretized by z-transformation. The stability criterion of the discretized system during slipping phase is derived, thus, the critical task scheduling period can be determined. The engagement quality in terms of vehicle jerk and clutch frictional losses is evaluated by simulation data, further, the dynamic response is also tested on transmission dynamometers. The results show that, the clutch engagement quality is insensitive to the task period which is less than the critical value, however, is deteriorated seriously when the task period exceeds the critical value.

Key words: task scheduling period, clutch engagement, stability, dynamic response