Control Strategies To Reduce Both The Frictional Energy Loss And Jerk In DCT Gearshifts

The dual-clutch transmission (DCT) is one of the most convenient and efficient practical transmissions in the world nowadays. It has high mechanical efficiency similar to traditional manual transmission (MT) and realized similar power shifts as automatic transmissions (AT) have. Because the Chinese local automotive companies have a long experience on the production of manual gearboxes, the development of DCT is of great practical meaning for China.The old contradiction between reducing jerks and reducing frictional energy losses has been a serious problem in the study of traditional clutch control. If we want to reduce the level of jerks, then more frictional energy loss will be caused. Otherwise, if we reduce the frictional energy loss, then the level of gearshift jerks will rise. This thesis reconsiders the contradiction very carefully by finding out the real dominating time zone of jerks and friction occurring, and applies new control strategies to achieve new better balance between the old contradictions.The research firstly sets up a new dynamic model of gearshifts for the DCT under an assumption that: the transmission is a multiple-degree-of-freedom (SDOF) rigid body system, without any stiffness or damping coefficient along the driveline. Some other surrounding factors are also simplified in the model without losing the dynamic characteristics of the system. The interruption to the system inputs is also neglected. For simulation comparison, another benchmark model is founded as well.This control strategy of this thesis is concentrating on the control strategy to improve the performance of gearshifts in two main aspects: depressing the longitudinal jerk and decreasing the frictional energy dissipation. The model reference control method (MRC) is proposed and applied to realize the goals, and the final'locked'mode of the DCT gearshift is chosen as the referenced model to instruct the running direction of the plant.Finally, analytical models have been set up on the platform of MATLAB/Simulink based on the dynamic and mathematical derivation, with no usage of professional toolboxes. By investigating the transient responses of gear shifting simulation, it has evidently shown that the MRC method can greatly improve the performance of dual-clutch transmission by reducing both the vehicle jerk and frictional loss. Besides, the DCT gearshifts are achieved responding quicker eventually.In summary, this thesis spans from the DCT dynamic modeling, MRC controller design and numeric simulations. The general gearshift of a DCT is carefully analyzed and divided into several stages for better dynamic derivation and controller design. It is the first time that the MRC method is applied on the control of DCT transmissions, which is proved to be a wise choice of DCT controlling strategy in this thesis.