Online detection and control of car body low-frequency swaying in railway vehicles

Low-frequency swaying is an abnormal vibration of railway vehicles. It is manifested by a low-frequency and high-amplitude swaying of the car body, which continues for a period of time, posing a significant threat to the passengers' ride comfort and even the vehicle operation safety. However, the complexity of swaying makes the alleviation of this hazard by the conventional suspension parameters and available wheel-rail profile optimisation schemes quite problematic. This study analyses the specifics of vibration signal detection and active low-frequency vibration absorption, based on which a comprehensive set of implementable and universal process approaches to detect and control the low-frequency swaying is proposed. First, the intrinsic parameters of various stages of the swaying signal were obtained via the wavelet packet transform. Based on this, two online detection methods based on a single intrinsic parameter and a combination of intrinsic parameters were proposed. Subsequently, an active low-frequency inerter-spring-damper (ISD) type dynamic vibration absorber (DVA) control strategy was adopted to suppress low-frequency swaying. Finally, full-vehicle models with passive suspension and active low-frequency ISD-DVA were established to investigate the effect of online detection and control of low-frequency swaying. The results obtained proved that the proposed method could promptly detect and accurately identify different swaying stages of the railway vehicle, and the active ISD-DVA is instrumental in the low-frequency swaying elimination and overall improvement of the vibration performance of railway vehicle systems.