Gear shift control of a dual-clutch transmission using optimal control allocation

Abstract

This study develops control strategies for the gear shift of dual-clutch transmissions (DCTs) using optimal control allocation. DCT powertrains require sophisticated control of two clutch actuators and the engine throttle to achieve good shift performances, i.e. smooth and fast gear shifts. In this paper, a new approach to the control strategies is implemented through interpreting the DCT powertrain as an over-actuated system that possesses actuator redundancy. The developed control structure is divided into two stages: the upper level control that governs the procedure to determine the most suitable torque trajectories of the clutches and engine, and the lower level control that manages the strategy for each actuator controller to track the given torque trajectories. The core of this study is the development of an effective upper level controller based on the optimal control allocation, to which previous studies have not paid adequate attention. A major advantage of this control approach is that the resulting shift performances can be easily and intuitively adjusted by tuning only one parameter. The effectiveness of the control scheme is demonstrated through various simulations using a high-fidelity DCT model implemented with a commercial software SimDriveline, and detailed discussions of the results are also provided.