This paper presents a mode shift control algorithm for reducing the variation in the driveshaft torque for a dual-mode power-split-type hybrid electric vehicle. To evaluate the shift characteristics of this hybrid electric vehicle, dynamic models for the hybrid electric vehicle powertrain were developed. Using the dynamic models, a mode shift performance simulator was developed, and simulations were performed. To analyse the shift characteristics during the mode shift, bond-graph models for the transient state were constructed, and state equations were derived. From the bond-graph models and state equations, it was found that the transient torque occurs because of the inertia torques of the first motor–generator and the second motor–generator. Based on the transient torque, a mode shift control algorithm was proposed, which compensates for the transient torque. To evaluate the performance of the proposed control algorithm, a test bench for the dual-mode power-split-type hybrid electric vehicle was developed. From the simulations and test results, it was found that the variation in the driveshaft torque was reduced by the proposed control algorithm, which provides improved shift quality.

In this paper, a shift control algorithm to improve the shift quality was proposed for an electric vehicle with a dry-type two-speed dual-clutch transmission. To analyse the shift characteristics of the target electric vehicle, dynamic models for the two-speed dual-clutch transmission and the drivetrain were developed. Based on the dynamic models, dynamic equations for the transient shift states were derived, and a shift performance simulator was constructed. From analysis of the transient shift state, it was found that the fluctuations in the driveshaft torque, which cause the shift quality to deteriorate, occurred as a result of the inertia torque. Based on the analytical results, a control algorithm was proposed using traction motor torque control as well as shift actuator stroke control. For traction motor control, a compensation torque was applied during the inertia phase. In that phase, actuator stroke control was performed by considering the torque margin and the kissing point during the torque phase instead of the existing map-based control. To evaluate the performance of the proposed control algorithm, a test bench for the target electric vehicle was developed. From the experimental results, it was found that the variations in the driveshaft torque and in the jerk were reduced by the proposed control algorithm, which thereby provides an improved shift quality.

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%.

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