In this study, a gear fork control algorithm for a dual-clutch transmission is proposed to improve the shift quality for the downshift from second gear to first gear during coast-down. First, to investigate the shift characteristics, a dual-clutch transmission shift performance simulator was developed including the gear fork system. Using the dual-clutch transmission simulator, the shift characteristics for the downshift from second gear to first gear were investigated during coast-down. From the simulations and the test results, it was found that vibrations occur in the speed of the output shaft owing the large change in the speed gradient of the input shaft at the moment of synchronization, resulting in a change in the longitudinal acceleration of the vehicle, which causes the shift quality to deteriorate. Based on the dynamic models of the gear fork system and the test results, a gear fork control algorithm is proposed which generates a constant cone torque to reduce the speed gradient of the input shaft. It was found from the simulations and the vehicle test results that the amplitudes of the vibrations in the speed of the output shaft and the peak-to-peak acceleration of the vehicle were reduced by the gear fork control algorithm proposed in this study, which improved the shift quality by as much as 50%.

A battery charging control using a driving motor is proposed for an AT based parallel HEV. To charge the battery using the driving motor, a 2-clutch system control is proposed which uses the engine clutch and the clutch inside the transmission. The battery charging efficiency is estimated from the engine fuel consumption and efficiency of the power electronics. To evaluate the performance of the suggested battery charging control, HEV performance simulator is developed and simulations are performed for FTP-72 mode. Simulation results show that battery charging using the driving motor has a higher charging efficiency and faster charging speed compared with the conventional battery charging system using the ISG.