Research On Vibration Frequency Of Electric Vehicle Suspension Systems Converted From Traditional Buses

The conversion of buses from diesel engines to electric ones plays a pivotal role in reducing pollution, improving air quality, and supporting sustainable development in Da Nang. This project contributes to the city’s goal of achieving net-zero emissions by 2050, promoting progress in local technology, economic growth, and public transportation modernization. However, changes in weight and load on distribution probably affect the natural frequency of the suspension system. To ensure comfort and safety for passengers, the natural frequency needs to be reassessed after transitioning from traditional buses to electric ones. In this research, a simulation model of the suspension system, without considering air spring characteristics, is calibrated on a full-vehicle dynamics model and evaluated according to the QCVN09:2011/BGTVT standard issued by the Vietnamese Ministry of Transport. The bus is placed on a test bench at heights $h=70 \mathrm{~mm}$ and $h=120 \mathrm{~mm}$, then freely dropped, and the acceleration responses are recorded and analyzed over time. The simulation results show that the natural frequency of the suspension system before and after conversion in the test case with a height of $h=120 \mathrm{~mm}$ is $f=2.32 \mathrm{~Hz}$ and 2.38 Hz, corresponding to a decrease of $2.52 \%$ and an increase of $6.72 \%$ compared to $h=70 \mathrm{~mm}$. Based on these results, it can be observed that the seat bench height has little or no significant effect on the natural frequency of the suspension system. Furthermore, according to the QCVN09:2011/BGTVT standard, the natural frequency should not exceed 2.5 Hz. Therefore, the simulation results in both test cases ensure that the natural oscillation frequency remains within the allowable limit. In the future, elastic components incorporating air spring characteristics will be designed and integrated into the simulation. These simulation findings serve as a foundation for evaluating and refining the oscillation frequency between scenarios with and without air springs.