I. Introduction
Internet of Things smart devices can be profitably used in freight trains applications for improving transportation safety and efficiency. These smart devices need to be supplied even if, on freight trains, the electricity lacks. Therefore, in order to overcome such a limitation it is necessary to look for the harvesting of alternative energy sources. A promising solution is represented by the harvesting of the vibrations mechanical energy dissipated in railcar suspensions. In the literature, a number of Train Suspension Energy Harvesters (EHs) has been proposed [1]. The great majority of these systems is based on a three-phase electromagnetic generator [2]. In [3] an energy harvester system for railcar suspensions composed by a rack and pinion shaft, a Mechanical Motion Rectifier (MMR), a gearhead and a three-phase electromagnetic generator is proposed.