Abstract: Due to the complexity of the service environment of high-speed trains, the carbody vibration amplitude increases and the passenger ride comfort decreases. Based on the optimal control theory of LQR algorithm, the idea of installing semi-active suspension on carbody underneath suspended system is proposed. Considering carbody flexible and suspended equipment, a coupled vertical vibration model of high-speed railway train is established, which is used to analyze the effect of the weighted coefficient R of the LQR algorithm on carbody vibration reduction, and also compared the effects of the passive suspension and the semi-active suspension. The results show that reducing the weighting coefficient R is beneficial to reducing carbody elastic vibration, and when the weighting coefficient is reduced to 1×10^-5, the elastic vibration would be significantly reduced. However, it does not affect the rigid vibration. The effect of the semi-active suspension on the vibration control of the vehicle body is closely related to the elastic vibration energy of the vehicle body. The greater the elastic vibration energy of the vehicle body, the better the control effect of the semi-active suspension is. When the body is elastically vibrated, the vibration reduction effect of the semi-active suspension body is significantly better than that of the passive suspension. Under the running speed of obvious carbody elastic vibration, the RMS value of the body vibration under the semi-active suspension is reduced by about half.

Key words: high-speed railway train, carbody underneath suspended system, semi-active control, LQR algorithm, carbody vibration reduction