# Control Strategy Development of Driveline Vibration Reduction for Power-Split Hybrid Vehicles
## 5 Conclusions  
This research established a forward Two-Mode Hybrid System module with MATLAB/Simulink, and incorporated elastomers such as engine damper, half-shaft, and tires to present the vibration situation of the driveline while driving. Previous research majorly focused on the driveline vibration caused by the traction motor during start and speed-up of vehicle. This research included the torque disturbance from cylinder pressure of the internal combustion engine, and control strategies were applied on electric motors that had quick responses to eliminate the vibration caused by the torque disturbance from the engine and driveline system. Vibration reduction control to the driveline was applied while the internal combustion engine was started or transmission was shifting modes. At the same time, without changing the power demand, three control methods were implemented. Such as Pulse Cancellation, which could reduce vibration by expecting vibration derived from the operation of the internal combustion engine and the angular acceleration of the transmission output, and PID control, which was able to adjust the speed of the faster-responsive motor/generator to reduce the vibration that was created by the angular velocity of the transmission output. The two control methods above were combined at the end. According to the data analysis in the previous sections, the following conclusions can be drawn:  
1. The vibration of the half-shaft torque feedback under each control method was observed in the time domain, the effect of PC was obvious when the vehicle accelerated and the internal combustion engine started up, the vibration reduction range of peak-to-peak value of torque was able to reach up to 22.5%. On the whole, however, the PID vibration reduction effect was more significant. The vibration reduction range of peak-to-peak value was able to reach up to 40% when the vehicle accelerated, the convergence speed was also faster, and the torque output was smoother. In addition, the effect in the time domain was not much different from the PID; therefore, the difference will be need to be determined by the frequency response. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **PC (\%)** & **PID (\%)** & **PC-PID (\%)** \\ \hline
**5 Hz** & 4.3\% & 78.2\% & 78.2\% \\ \hline
**11 Hz** & 24.7\% & 94.7\% & 92.9\% \\ \hline
**16 Hz** & 60\% & 78.7\% & 86.2\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of the vibration deduction of different control methods in the frequency domain. Figure 10: Half-shaft torque comparison with different control methods in frequency domain. Apart from the observation of torque in the time domain, Fast Fourier Transform analysis of half-shaft torque of the vehicle was performed. In the frequency response of half-shaft torque, it was found that although the vibration was deduced with PC, and the vibration reduction at engine damper natural frequency, 16 Hz, was able to reach up to 60%. The vibration deduction at tire natural frequency, 5 Hz, was not obvious. The vibration reduction was relatively better in the PID frequency domain response. In the original vibration, sources of 5 Hz, 11 Hz, and 16 Hz were also effectively isolated, each reduced by 78.2%, 94.7%, and 78.7%, respectively, while the effect of vibration reduction of the PC-PID at 16 Hz increased another 8%, strengthening the effect of vibration reduction for the internal combustion engine. 3. The vibration reduction analysis of this research focused on the low-frequency vibration, which was directly related to the comfort of the human body. This research simulated the vibration situation when the power source was operated by estimating of the torque of the internal combustion engine derived from the cylinder pressure and adding elastomers such as a internal combustion engine damper, Half-Shaft, and tires to the driveline. There are a few more ideas for the modeling process as follows, which could be applied to improve accuracy in the future.