mechanicalvibrationsenergyharvestingandpowermanagement-外文文獻(xiàn)-文庫吧
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【正文】 f its associated energy is quite low. The second parameter which conditions the available input energy is the inertial mass. Indeed, the available energy is proportional to this mass, but this mass can’t be very important for a micro system. Nevertheless, we patented the possibility to add to the passive mass the mass of some useful elements as electronic, battery and antenna. However that remains the principal limitation in the size reduction while the moving mass can represent 90% of the total system size. In consequence, it is interesting to have a bigger converter if it permits to improve the use of the moving mass. B. Maximizing the input energy extraction In order to maximize the input energy extraction, the scavenger must have its input impedance in agreement with the input vibration. If the input vibration is well know and don’t move with the time as on a machine supplied by the electrical work, the good input impedance can be obtain by a resonant system witch its resonant frequency is tuned on 1424425815/08/$ 169。2020 IEEE 29 IEEE SENSORS 2020 ConferenceAuthorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on January 13, 2020 at 05:55 from IEEE Xplore. Restrictions apply. the input vibration. Else, if the input vibration is not well defined or naturally move in the time as on a transportation machine (car, plane, train…), it is better to have a wide band of frequency system based on a good coupling between the mechanical part and the electrical part. We showed in a precedent paper [1] that for classical source of vibration (building, mechanical machine, transportation machine…) a good promise is to have a system able to scavenge from few Hz to 120 Hz by having a resonant frequency around 50 Hz and an electrical damping higher than 1/10. This high electrical damping can only be obtain with an electrostatic transduction in case of low input frequencies (100Hz) and for a small system size (3 cm3). III. DEMONSTRATORS APPROCHE In order to demonstrate the feasibility to use an electrostatic transduction system to convert mechanical vibration energy in electrical energy with good input impedance, we developed a first macroscopic demonstrator (cf. Figure 1). Figure 1. First bulk tungstene prototype (18 cm3) As presented on Figure2, we demonstrated on one part the possibility to convert a mechanical energy with a high efficiency of 60 % and on other part the capability of the system to extract a high level of the theoretically available energy for different input vibrations. Figure 2. Power balance for the tungsten prototype (for 50 Hz, 90 181。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
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