University of Rijeka, Faculty of Engineering, Vukovarska 58, 51000 Rijeka, Croatia.
University of Rijeka, Centre for Micro- and Nanosciences and Technologies, Radmile Matejčić 2, 51000 Rijeka, Croatia.
Sensors (Basel). 2021 Oct 24;21(21):7042. doi: 10.3390/s21217042.
The development of wearable devices and remote sensor networks progressively relies on their increased power autonomy, which can be further expanded by replacing conventional power sources, characterized by limited lifetimes, with energy harvesting systems. Due to its pervasiveness, kinetic energy is considered as one of the most promising energy forms, especially when combined with the simple and scalable piezoelectric approach. The integration of piezoelectric energy harvesters, generally in the form of bimorph cantilevers, with wearable and remote sensors, highlighted a drawback of such a configuration, i.e., their narrow operating bandwidth. In order to overcome this disadvantage while maximizing power outputs, optimized cantilever geometries, developed using the design of experiments approach, are analysed and combined in this work with frequency up-conversion excitation that allows converting random kinetic ambient motion into a periodical excitation of the harvester. The developed optimised designs, all with the same harvesters' footprint area of 23 × 15 mm, are thoroughly analysed via coupled harmonic and transient numerical analyses, along with the mostly neglected strength analyses. The models are validated experimentally via innovative experimental setups. The thus-proposed = 50 mm watch-like prototype allows, by using a rotating flywheel, the collection of low-frequency (ca. 1 to 3 Hz) human kinetic energy, and the periodic excitation of the optimized harvesters that, oscillating at their eigenfrequencies (~325 to ~930 Hz), display specific power outputs improved by up to 5.5 times, when compared to a conventional rectangular form, with maximal power outputs of up to >130 mW and average power outputs of up to >3 mW. These power levels should amply satisfy the requirements of factual wearable medical systems, while providing also an adaptability to accommodate several diverse sensors. All of this creates the preconditions for the development of novel autonomous wearable devices aimed not only at sensor networks for remote patient monitoring and telemedicine, but, potentially, also for IoT and structural health monitoring.
可穿戴设备和远程传感器网络的发展越来越依赖于其增强的自主供电能力，通过用能量收集系统替代具有有限寿命的传统电源，可以进一步扩展这种能力。由于其普遍性，动能被认为是最有前途的能量形式之一，特别是与简单且可扩展的压电方法相结合时。压电能量收集器（通常为双模态悬臂梁）与可穿戴和远程传感器的集成突出了这种配置的一个缺点，即其较窄的工作带宽。为了克服这一缺点并最大限度地提高功率输出，本文使用实验设计方法对优化的悬臂梁几何形状进行了分析，并将其与频率上变频激励相结合，该激励允许将随机的环境运动转换为对收集器的周期性激励。在所开发的优化设计中，所有设计都具有相同的收集器足迹面积 23×15mm，通过耦合谐波和瞬态数值分析以及通常被忽略的强度分析进行了彻底分析。通过创新的实验设置对模型进行了实验验证。所提出的 =50mm 手表状原型通过使用旋转飞轮，可以收集低频（约 1 到 3Hz）人体动能，并周期性地激励优化的收集器，这些收集器以其固有频率（325 到930Hz）振荡时，与传统的矩形形式相比，特定功率输出提高了 5.5 倍，最大输出功率高达 >130mW，平均输出功率高达 >3mW。这些功率水平应该足以满足实际可穿戴医疗系统的要求，同时还提供了适应各种不同传感器的能力。所有这些都为新型自主可穿戴设备的开发创造了前提条件，这些设备不仅旨在用于远程患者监测和远程医疗的传感器网络，而且还可能用于物联网和结构健康监测。
