Keywords: railway switch, point machine, trapped foreign object, field measurement, multibody dynamics simulation, model calibration.

Railway switches are critical for network flexibility but remain a significant source of operational disruptions, particularly when foreign objects become trapped between the switch and stock rails during actuation. Such obstructions can prevent proper switch closure, causing delays and increased maintenance costs, or, in cases of local gauge narrowing, raise the risk of derailment if undetected. It is therefore of interest to detect such disturbances as efficiently as possible. This study explores whether switch rail end position detection can be achieved using drive output alone, without supplementary sensors that require additional systems and maintenance. When an obstruction is present, the drive must exert additional force to close the induced gap, altering its force and current profile in a way that may indirectly reveal the presence of a foreign object. To better quantify this influence and allow for future development of detection algorithms, a multi-body system (MBS) model of switch actuation under a trapped foreign object is developed and calibrated against field measurements of forces in actuation rods and foreign object. After calibration of the slide chair friction coefficient and drive stiffnesses, the simulated results show good agreement to field measurement results. The model therefore provides a foundation for combining simulation and field data to develop an efficient detection method for foreign objects.

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