To improve operational safety and system reliability, real-time wireless health monitoring systems are necessary for freight trains. However, due to the lack of onboard power and space restrictions, monitoring sensors rely on batteries as power sources, which are not eco-friendly and involve high maintenance costs for battery replacement. Therefore, developing self-powered maintenance-free wireless monitoring sensors integrated with energy harvesting is in urgent demand. Here, we propose a compact ultralow-frequency and broadband piezoelectric energy harvester (UBPEH) that can be easily installed in the limited space of the axle box to effectively harvest bogie lateral vibrations. The T-shaped UBPEH employs magnetic interaction to soften the stiffness and strengthen the stopper operation in a low-frequency range. To predict and optimize the prototype, we establish the model of UBPEH by considering the displacement, inclination angle, and shape of the magnets. Theoretical and experimental results show that the prototyped UBPEH might operate in the range of 1–11 Hz, covering the representative frequencies of bogie vibrations on freight trains. An output power of 605 μW on a matched resistance of 200 kΩ under the acceleration of 11 Hz and 0.5 g (g = 9.8 m s⁻²) is achieved, and the harvested electric power can successfully drive typical commercial wireless Bluetooth sensors. Furthermore, the harvester possesses output stability and mechanical durability under actual service hours of freight trains. The results of this work pave the way to implement self-powered wireless condition monitoring on freight trains.

为了提高运行安全性和系统可靠性，货运列车需要实时无线健康监测系统。然而，由于车载电源和空间限制，监控传感器依赖电池作为电源，不环保，更换电池需要高昂的维护成本。因此，迫切需要开发与能量收集集成的自供电免维护无线监控传感器。在这里，我们提出了一种紧凑的超低频和宽带压电能量收集器（UBPEH），它可以很容易地安装在轴箱的有限空间内，以有效地收集转向架横向振动。T 形 UBPEH 采用磁相互作用来软化刚度并加强低频范围内的止动器操作。为了预测和优化原型，我们通过考虑磁体的位移、倾角和形状建立了 UBPEH 模型。理论和实验结果表明，原型 UBPEH 可以在 1-11 Hz 的范围内运行，涵盖货运列车转向架振动的代表性频率。在 11 Hz 和 0.5 g (g = 9.8 m s^{− 2} ) 实现，收集的电能可以成功驱动典型的商用无线蓝牙传感器。此外，该收割机在货运列车的实际运行时间内具有输出稳定性和机械耐用性。这项工作的结果为在货运列车上实施自供电无线状态监测铺平了道路。