Adaptive Feed-Forward Control of the Clutch Filling Phase for Wet Dual Clutch Transmission

Clutch fill control in clutch-to-clutch shift process is an essential technique to ensure smooth and precise synchronization of clutches. The filling control methods proposed in previous works are difficult to apply to production vehicles because of huge calibration effort and numerical issues of the system model. Therefore, this paper focuses on the development of clutch fill control logic considering practical issues at the production vehicle level. In order to increase the usability, a simplified reduced model that describes the filling phase is designed. The proposed model is used to construct a model-based feed-forward controller, which is not affected by a time delay in the hydraulic system. Furthermore, an adaptation algorithm of a key model parameter is proposed to cope with the model changes due to the disturbances and uncertainties of the plant. In addition, a new volume indicator is proposed to observe the status of the filling phase. Based on the proposed controller and the indicator, tracking performance of the filling phase is guaranteed without over-fill or under-fill. As a result, the proposed control logic is applied to a production type transmission control unit in a test vehicle and its performance is experimentally verified through various scenarios.