Influence of particle sensor’s shape, size and wire on motion capture in ballast bed

Particle sensors can be used to obtain particle movement characteristics of a ballast bed, providing a particle-scale measure for assessing the state of the ballast bed. The sensor size, shape and wire fetter may have impacts on the applicable scenarios, measured results and subsequent analysis process. This paper conducts laboratory tests and discrete-element method (DEM) simulation to preliminarily discuss the influence of the particle sensor’s configuration when obtaining details of ballast particles’ motion. According to laboratory test results, particle motions from cubic sensors with two edge lengths show different magnitudes, where the influence of ballast packing is not effectively excluded. Hence, DEM simulation is employed to systematically investigate the influences of sensor size and shape (regular polyhedrons) on particle motion. The results indicate that for cubic particle sensors, the acceleration shows a decreasing trend with increasing sensor size. Moreover, the z-angular acceleration decreases first and then stabilises, with 40 mm as the boundary point. The change of sensor shape leads to significant fluctuations in the angular acceleration. The impact of wire fetter on particle motion characteristics is obtained from laboratory tests. It is seen that particle motion characteristics from wireless particle sensors show similar variation tendencies and magnitudes, while the magnitudes of particle acceleration in three directions from wired particle sensors are quite different.