Identification of Trapped Foreign Objects in Railway Switches Using Drive Outputs

Abstract

Railway switches are crucial in enhancing railway network flexibility but are also a significant source of operational disruptions. A common cause of disruption is when foreign objects such as ballast stones, metal debris, snow, or ice become trapped between the switch and stock rail during switch rail actuations. Such obstructions can hinder switch operations and thereby cause train delays and increased operational costs. If they cause significant local gauge narrowing, there is an increased risk of derailment if trains pass by. To prevent such scenarios, it is crucial to accurately and cost-effectively identify trapped foreign objects at an early stage. The Swedish switch designs currently in operation often use a combination of drive (point machine) locking tolerances and additional position sensors along the switch rail to detect foreign objects that can constitute a derailment risk. These sensors require maintenance and sometimes cause traffic disruptions by themselves due to malfunction. When an obstruction is present, the drive exerts additional force to close the induced gap via bending of the switch rail, resulting in increased power and current consumption. The aim is to develop a robust condition monitoring system for identifying trapped foreign objects by analysing the current output of drives in addition to their locking tolerances. By examining current output curves, deviations from ideal operational conditions can be observed, enabling the identification of dangerous objects. The aim of this paper is to analyse deviations from ideal operational conditions for different object scenarios by utilizing a multibody simulation (MBS) model of a standard switch. Simulations were carried out for varying object sizes and positions between the drives. The presence of a trapped foreign object under various operational conditions was detected by analyzing the force-displacement outputs at the drives.