Valve-controlled semi-active lateral vibration reduction system for high-speed EMUs and tests

To ensure the lateral ride comfort of high-speed EMUs running across the existing passenger transport line (160 km·h^-1), speed-up line (250 km·h^-1), and high-speed passenger transport line (350 km·h^-1), a semi-active lateral vibration control system was designed based on the sky-hook damping principle and valve-controlled semi-active damper. The bench test and line test were performed. A test was first carried out for the dynamic performance, valve-control characteristics, and response time delay of the valve-controlled semi-active damper. A rolling and vibration bench test was carried out to analyze the control effect under three types of track excitation. Furthermore, a low-speed line test was performed to evaluate the improvement effect of lateral vibration of the car body. The results show that the measured response time delay of the semi-active control system is about 140 ms. A time delay compensation method is then proposed based on vibration prediction, which can compensate time of 1/4 vibrating cycle. The bench test verifies the validity and necessity of the time delay compensation. The rolling vibration and bench test with different track spectra and vehicle speeds demonstrates the effectiveness of constant damping, on-off damping, and continuous damping control strategies. The lateral ride comfort index can be improved up to 19% and the bandwidth of vibration reduction is 1-20 Hz. The improvement effect gets better with higher vehicle speed and worse track spectrum. According to the line test, the semi-active damping system has significantly restrained the low-frequency vibration below 2.5 Hz on the car body. The improvement rate of the ride comfort index is 11% at 160 km·h^-1. The findings can provide theoretical and technical support for the application of active suspension technology, thus promoting the performance improvement of existing EMUs and the innovative design of higher-speed EMUs.