mechanicalvibrationsenergyharvestingandpowermanagement-外文文獻(xiàn)-全文預(yù)覽
【正文】 tems for each sources, and to choose the best power path between sources, loads and battery in term of efficiency. Figure 9. Power path configuration management At present time, the integrated circuits are working under to depending on the technology and the functionality (analog or digital). The batteries are design to store the maximum of energy, so the trend is to increase the battery voltage over 3V. The energy sources outputs are not over 1V. The question is: how to avoid the power path from the sources (1V) to the battery (3V) trough a first DCDC converter, and then from the battery to the loads ( for example) trough a second DCDC converter and a LDO regulator? In this case with a 500181。W Transduction Mechanical energy 1760 181。W Discharge losses 3396 181。m) The 60% of efficiency takes in account the power management consumption. This system is in our knowledge the first electrostatic system pletely autonomous and able to produce an extra power directly in a current form and at a useful voltage (3V). However the system presents some limitations: o The gap between fingers must be higher than the relative displacement amplitude, which limits the capacitance density. o The efficiency decrease with the decrease of the displacement amplitude. This is due to a drop off in capacitance variation reducing the energy gain pare to the required energy for polarization. o The system needs an initial energy source to be polarized. We describe in the following parts our different way to go beyond these limitations. A. Capacitance densification Staying in the case of an in plane gapclosing structure, we showed that for a given displacement amplitude, it’s interesting to use a triangle structure in term of capacitance density. Furthermore, with this type of structure it is possible to mechanically adjust the gap and then adapt the structure to the vibrations conditions in order to maximize the capacitance variation. To validate the interest of its new geometry, we designed and fabricated a second tungsten prototype. This second prototype, presented on Figure 3, has an inertial mass 10 times smaller than the first one and permit us to have a first analyze the scaling effect. Figure 3. Second tungsten prototype with triangle fingers ( cm3) B. Initial energy production The big limitation in electrostatic transduction pare to other transduction principles is that it requires an initial energy to start. Indeed, if the electrostatic force can be actively driven to maximize the input energy absorption in against part it requires an initial energy source to be applied. If the objective of scavenging energy is to prolong the battery lifespan, that it’s good. But if the objective is to realize a system only based on energy scavenging with some long period without input energy, it can be a problem. To overe this limitation, we propose to bine the electrostatic principle with piezoelectricity by a judicious synchronization between the both phenomena [2]. The idea is that the piezoelectric structure reach its maximum of deformation when the capacitance of the electrostatic structure reach is maximum, enabling a direct transfer from the piezoelectric element to the capacitance. The electrostatic structure is then naturally polarized at the good time without external source. After the starting, the system can e back in an optimizing active mode. 1052 181。2020 IEEE 29 IEEE SENSORS 2020 ConferenceAuthorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on Janua
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