Abstract
Multi-converter piezoelectric harvesters based on mono-axial and bi-axial configurations are proposed. The harvesters exploit two and four piezoelectric converters (PCs) and adopt an impinging spherical steel ball to harvest electrical energy from human motion. When the harvester undergoes a shake, a tilt, or a combination of the two, the ball hits one PC, inducing an impact-based frequency-up conversion. Prototypes of the harvesters have been designed, fabricated, fastened to the wrist of a person by means of a wristband and watchband, and experimentally tested for different motion levels. The PCs of the harvesters have been fed to passive diode-based voltage-doubler rectifiers connected in parallel to a storage capacitor, Cs = 220 nF. By employing the mono-axial harvester, after 8.5 s of consecutive impacts induced by rotations of the wrist, a voltage vcs(t) of 40.2 V across the capacitor was obtained, which corresponded to a stored energy of 178 μJ. By employing the bi-axial harvester, the peak instantaneous power provided by the PCs to an optimal resistive load was 1.58 mW, with an average power of 9.65 μW over 0.7 s. The proposed harvesters are suitable to scavenge electrical energy from low-frequency nonperiodical mechanical movements, such as human motion.
Highlights
The development and employment of wearable electronic devices have rapidly increased in recent years
The impact between the ball and the piezoelectric converters (PCs) happens as soon as the external excitation applied to the harvester by a shake or a tilt causes the ball to roll towards a cantilever
The path of the ball is confined within a predefined volume, designed to make the overall size compliant with the dimension constraints of wearable and unobtrusive devices
Summary
The development and employment of wearable electronic devices have rapidly increased in recent years. An improvement can be achieved by employing a rigid ball, confined within a predefined volume, as the moving element impacting a piezoelectric converter, leading to an energy harvesting mechanism that is sensitive to input excitations along multiple spatial directions. Experimental results show that for a pendulum ball excited with a 2.5 mm horizontal displacement at 2 Hz, the open-circuit peak voltage is 15.8 V and a maximum output power of 10.53 μW is achieved across a 130 kΩ load resistance In this context, the present work proposes wearable mono-axial and bi-axial ballimpact multi-converter piezoelectric harvesters to scavenge energy from human motion. Prototypes of the mono-axial and bi-axial ball-impact multi-converter harvesters described in Section 2 were fabricated employing 1.6 mm-thick FR-4 sheets as structural elements in a multi-layer arrangement. TTThhheee eeellleeeccctttrrriiicccaaalll cccooommmpppooonnneeennntttsssCCCpppccc aanndd RRppccccccaaannnbbbeeeaaassssssuuummmeeedddttoo bbee ffrreeqquueennccyy--iinnddeeppeennddeenntt,, wwwhhhiiillleeevvpppccc((t(t)t))dddeeetteteerrmrmmiininneesessoopoppeenenn--cc-icirricrcucuuiittivtvovololttalatgagegevevoovcc(o(ttc))(ata)nnaddnrrdeeffrlleeecflcttessctthsheethddeyyndnayammnaiicmcmmiceecmchheaacnnhiicacanallircreae-lsrspepsoopnnossneesooeffotthfhetehcceaancntatiinlleetvivleervrfefoorrrfeoearaccehhaicimmhppimaaccpttaeecvvteeennvtt,e,dndete,sscdcrreiibsbceerddibiinendSSeienccttSiiooencnt3i3oaannnd3darrenepdpoorrrettepeddoriintneFdFiigign-uFurirgeeu66r..ePP6hh.yysPsihiccayalslpipcraroolpppeerrrottipieeessrotoiffetsthhoeefPPtChCsesaPannCddsssatteneedellbsbtaaellellwwbiaitthlhl twthheietghgeetohomme egetetrroiiccmaaleldtdriiimmcaeelnndssiiiomonnessnoosfifotthnhese dodefevtvheeleloodppeeedvdemmlooopnneodo--aamxxioiaanlloaa-nnaddxibbaili--aaaxnxiidaallbhhia-aarrvxveieassltteehrrassravarreeesltlieissrttseeddariiennlTTisaatbebldlee1i1n..PPTiaieebzzlooecce1er.raaPmmieiiczcoeelcleeemmraeemnntitscs cecalaennmsseuunffftfeserrcpaponosssssuiibfbflleeerlloponongsg-s-titeberlrmemloddnuugrra-atbebirillmiittyydlluiimmraiitbtaaitltiiiotoynnslsimaaffittteearrtirroeenppseeaaatfteteeddriirmmepppeaaacctttessddduiumeepttoaocttthhseediuinne-tttroriintnhssieiccinbbrtrriitittntllseeinnceebssrssitatanlnedndessseesnnassniittdiivvsiitetyynsttiootivtthihteeyptpohhetehnneoompmheeennnooonnmooeffnfofaanttiigogufuefea..tTiTghhueee.mmTaahssessm((00a..5s51s1(gg0).)5aa1nngdd) dadniiaadmmdeeittaeemrr (e(55temmr m(m5))moofmf tth)heoefbbtaahllel wwbeaerlrleewppreroroeppeperrrlloyypsseeerllleeyccttseeeddletctootekkdeeetepopkmmeeeecpchhamanneiicccahalal pnprircooappleeprrtrtioieepsseccrootmimes-pcpoaamttiibpbllaeetiwbwlieitthhwwiwthrriiswstt-r-wwisoto-rwrnnoaarpnpppallpiiccpaaltiticiooanntissoanansndadnttdoo tpporrepevrveeevnnettnddtaadmmamaaggaeegettoototthhtheeePPPCCCss.s..AAAsssaaa dddiiiffffffeeerrreeennnttt aaapppppprrroooaaaccchhh,,, tttooo fffuuurrrttthhheeerrr aaavvvoooiiiddd ooovvveeerrrssstttrrreeessssss tttooo PPPCCCsss,,, sssooollluuutttiiiooonnnsss bbbaaassseeeddd ooonnn iiinnndddiiirrreeecccttt iiimmmpppaaaccctttsss,,, eee...ggg...,,, iiimmmpppaaaccctttssshhhaaappppppeeennniiinnngggooonnnttthhheeesssuuubbbssstttrrraaattteeeooonnnwwwhhhiiiccchhhttthhheeepppiiieeezzzoooeeellleeeccctttrrriiiccctttrrraaannnsssddduuuccceeerrriiisssiiinnnssstttaaallllleeeddd,,,ooorrr mmmaaagggnnneeetttiiiccciiinnnttteeerrraaaccctttiiiooonnnssstttoootttrrriiiggggggeeerrrttthhheeefffrrreeeqqquuueeennncccyyy---uuupppcccooonnnvvveeerrrsssiiiooonnncccaaannnbbbeeeeeexxxpppllloooiiittteeeddd[[[111777,,5,55444]]]
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