The process of collecting low-level kinetic energy, which is present in all moving systems, by using energy harvesting principles, is of particular interest in wearable technology, especially in ultra-low power devices for medical applications. In fact, the replacement of batteries with innovative piezoelectric energy harvesting devices can result in mass and size reduction, favoring the miniaturization of wearable devices, as well as drastically increasing their autonomy. The aim of this work is to assess the power requirements of wearable sensors for medical applications, and address the intrinsic problem of piezoelectric kinetic energy harvesting devices that can be used to power them; namely, the narrow area of optimal operation around the eigenfrequencies of a specific device. This is achieved by using complex numerical models comprising modal, harmonic and transient analyses. In order to overcome the random nature of excitations generated by human motion, novel excitation modalities are investigated with the goal of increasing the specific power outputs. A solution embracing an optimized harvester geometry and relying on an excitation mechanism suitable for wearable medical sensors is hence proposed. The electrical circuitry required for efficient energy management is considered as well.

With the aim of increasing the efficiency of maintenance and fuel usage in airplanes, structural health monitoring (SHM) of critical composite structures is increasingly expected and required. The optimized usage of this concept is subject of intensive work in the framework of the EU COST Action CA18203 “Optimising Design for Inspection” (ODIN). In this context, a thorough review of a broad range of energy harvesting (EH) technologies to be potentially used as power sources for the acoustic emission and guided wave propagation sensors of the considered SHM systems, as well as for the respective data elaboration and wireless communication modules, is provided in this work. EH devices based on the usage of kinetic energy, thermal gradients, solar radiation, airflow, and other viable energy sources, proposed so far in the literature, are thus described with a critical review of the respective specific power levels, of their potential placement on airplanes, as well as the consequently necessary power management architectures. The guidelines provided for the selection of the most appropriate EH and power management technologies create the preconditions to develop a new class of autonomous sensor nodes for the in-process, non-destructive SHM of airplane components.

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Original scientific paperIn this paper general second-order low-pass and band-pass filter sections are presented. The voltage noise spectral density and Schoeffler sensitivity are calculated for the simple design procedure and for three different types of optimization. The optimization procedure is also done for the forth-order low-pass and band-pass filter. The resulting low noise and sensitivity is investigated using the RMS noise voltage and multi-parameter sensitivity measure. The optimization gives lower noise and lower sensitivity filters. All analyzes are performed using Matlab and Spice programming tools.Key words: Low-pass filter, Band-pass filter, Noise, Sensitivity, OptimizationOptimizirani NP i PP filtri drugog ičetvrtog reda. U radu su prikazane opće filtarske sekcije drugog ičetvrtog reda. Izračunati su spektralna gustoća napona šuma i Schoefflerova osjetljivost i to za jednostavan proračun te za tri različita tipa optimizacije. Optimizacija je takoer provedena za nisko propusni i pojasno propusni filtař cetvrtog reda. Dobiveni niski šum kao i osjetljivost ispitani su računanjem efektivne vrijednosti napona šuma i više-parametarske mjere osjetljivosti. Rezultati optimizacije daju filtre koji imaju manji šum kao i osjetljivost. Svi su proračuni izvedeni korištenjem programskih alata Matlab i Spice.