Launch and shift dynamics of dual-clutch transmission vehicles

In DCT vehicle operation, the two clutches in the transmission are engaged alternatively in the drive range to transfer the engine power to the driving wheels. Vehicle launch is realized by controlling the slippage in one of the two clutches and gear shifts are realized by controlling the slippage in both the oncoming and off-going clutch. In a shift, torque transfer is not interrupted due to the controlled slippage in the clutches. This results in a shift quality similar to clutch-to-clutch shift in a conventional automatic transmission. The timing of engagement and disengagement of the two clutches is critical for achieving a smooth shift without engine flare and clutch tie-up. In the absence of prototype experiments, computer based model is the key to analyze the dynamic transients during launch and shifts and to obtain technical data for transmission design and clutch control. This paper presents an analytical model for the simulation and analysis for dual-clutch transmission vehicles. The presented work is concentrated on modeling the vehicle dynamics during shifts and establishing a Matlab/Simulink based simulation tool for shift control using clutch pressure profiles as the control signals. As a numerical example, the model is used for a vehicle equipped with a dual clutch transmission to simulate the wide-open throttle performance. The output torque variation in response to different clutch pressure profiles has been quantitatively studied using the model. Optimized clutch pressure profiles were obtained for the best possible shift quality based on model simulation.