Feasibility of derailment prevention control for railway vehicles during earthquakes using active suspension

The purpose of this study is to discuss the feasibility of utilizing active suspension systems to stabilize vehicle behavior during earthquakes, thereby preventing derailments. The vehicle is modeled as a quarter-car system represented by a model that possesses a total of ten degrees of freedom, accounting for the lateral, vertical, and roll motion of each vehicle component. Each rigid body of the vehicle is connected by springs and dampers. The characteristics of the stopper mechanism and secondary spring, located between the car body and the bogie frame, are modeled as nonlinear force elements. Actuators are installed in the lateral direction between the car body and the bogie frame, and control inputs are determined based on the optimal control theory. The control model has been designed to minimize the relative lateral displacement between the wheelset and the rail. Vehicle behavior simulations have been conducted using a model that incorporates only the passive mechanism, in addition to the controlled models. For the passive model, simulations are conducted not only with a standard damping coefficient but also with an increased damping coefficient. Comparisons of the passive model and the active controlled model reveal a tendency to prevent derailment in low frequency while inducing derailment in high frequency region. On the other hand, increasing the passive damping coefficient is expected to have a derailment prevention effect in the high-frequency region, whereas no such effect is observed in the low frequency. Therefore, the effectiveness in preventing derailment in the low frequency region is a characteristic of the active control. These findings indicate the feasibility of derailment prevention control using active suspension.