Fiber-optic Bragg system for the dynamic weighing of municipal waste: A pilot study

Recei ed May 7, 2021, accep ed June 26, 2021, da e o publica ion July 6, 2021, da e o cu en e sion July 19, 2021. Digi al Objec Iden i ie 10.1109/ACCESS.2021.3095219 Fibe -Op ic B agg Sys em o he Dynamic Weighing o Municipal Was e: A Pilo S udy MARCEL FAJKUS 1, JAN NEDOMA 1, (Membe , IEEE), RADEK MARTINEK 2, (Membe , IEEE), LUKAS DANYS 2, MICHAEL FRIDRICH 1, PAVEL MEC3, AND STANISLAV ZABKA1 1Depa men o Telecommunica ions, Facul y o Elec ical Enginee ing and Compu e Science, VSB—Technical Uni e si y o Os a a, 70833 Os a a, Czech Republic 2Depa men o Cybe ne ics and Biomedical Enginee ing, Facul y o Elec ical Enginee ing and Compu e Science, VSB—Technical Uni e si y o Os a a, 70833 Os a a, Czech Republic 3Depa men o Building Ma e ials and Diagnos ics o S uc u es, Facul y o Ci il Enginee ing, VSB—Technical Uni e si y o Os a a, 70833 Os a a, Czech Republic Co esponding au ho : Ma cel Fajkus (ma cel. ajkus@ sb.cz) This wo k was suppo ed in pa by he Eu opean Regional De elopmen Fund in Resea ch Pla o m ocused on Indus y 4.0 and Robo ics in Os a a unde P ojec CZ.02.1.01/0.0/0.0/17_049/0008425 wi hin he Ope a ional P og amme Resea ch, De elopmen , and Educa ion, and in pa by he Minis y o Educa ion o he Czech Republic unde P ojec SP2021/32 and P ojec SP2021/45. ABSTRACT The publica ion ocus on a pilo s udy (design, implemen a ion and e i ica ion) o a dynamic weighing sys em designed o weighing o municipal was e du ing he dumping o ga bage con aine s. The p esen ed solu ion is based on ibe B agg g a ings (FBG) and can be addi ionally implemen ed in o he li ing equipmen o commonly employed ga bage ucks. The weighing p inciple is based on he measu emen o de o ma ion e ec and ib a ion esponse o he li ing equipmen du ing he dumping o ga bage bins. The measu ing sys em le e ages he ad an ages o powe measu emen , which use he con e sion o he spec al shi o modula ed ligh signal du ing he measu emen o he change in op ical powe o a pai o spec al o e lapping B agg g a ings. Two di e en me hods a e p esen ed and discussed: he ampli ude me hod, which analyze he maximum ampli ude change o he signal and/o he me hod, which analyze he ime pe iod o he dampened oscilla ion o he li ing de ice. Due o he small dimensions, he comple e sys em can be ins alled oge he wi h FBG senso s di ec ly on o he li ing de ice. The pilo es s o he p esen ed sys em we e ca ied ou o o e 4 mon hs, showing an accu acy o up o ±4.04 kg in he ange o 10-100 kg o s anda dized con aine s used o municipal was e. The sys em wo ked in comple ely s andalone mode and he ga bage ucks we e no modi ied in any incon enien way. INDEX TERMS Fibe B agg g a ing, op ical senso , dynamic weighing. I. INTRODUCTION AND STATE-OF-THE-ART Dynamic was e weighing o e s a solu ion o a i ica ion o ci izens based on he amoun o p oduced was e. This ad an age is o e lapping – he de ailed o e iew o ga bage con aine s (including he in o ma ion ega ding hei used o ee capaci y) can be used by smalle ci ies o municipali ies o educe was e disposal cos s and addi ional ees. The whole was e disposal p ocess can also be op imized in e nally o ex e nally, based on ga he ed da a and beha io o ci izens. These majo ad an ages a e behind he inc easing deploy- men o dynamic weighing sys ems. RFID sys ems, which use inac i e plas ic chips placed on was e bins, can be used o ansmi he equi ed in o ma ion [1]–[4]. When he ga bage The associa e edi o coo dina ing he e iew o his manusc ip and app o ing i o publica ion was Sal a o e Su do . uck is equipped wi h a weighing sys em, an in o ma ion on he commodi y and weigh o he was e can be di ec ly ans- mi ed, hus iden i ying, and cha ging he speci ic ci izen. The da a is usually s o ed in a cen alized da abase and e alua ed by a con ol node. The con en ional app oaches o measu ing ehicle weigh , o dynamic weighing espec i ely, a e nowadays di ided in o wo p e e ed di ec ions o de elopmen : Weigh- In-Mo ion (WIM) and On-Boa d Weighing (OBW). WIM sys ems a e independen and ex e nal, while he OBW sys- ems a e buil in o he ehicle i sel . WIM echnology is usually used o measu e he axle load o ehicle du ing i s mo emen in combina ion wi h induc ion loops [5]–[7]. The deploymen o ibe op ic sys ems o dynamic weighing while d i ing based on a ious p inciples is u he desc ibed in publica ions [8]–[17]. Fo example, Malla e al. [8] 99050 This wo k is licensed unde a C ea i e Commons A ibu ion 4.0 License. Fo mo e in o ma ion, see h ps://c ea i ecommons.o g/licenses/by/4.0/ VOLUME 9, 2021 M. Fajkus e al.: Fibe -Op ic B agg Sys em o Dynamic Weighing o Municipal Was e: Pilo S udy p esen s in e es ing expe imen al esul s om a measu emen on a special op ical ibe o measu e wheel loads o ehi- cles. The ibe used has a unique design wi h wo concen- ic ligh -guiding egions o di e en e ec i e op ical pa h leng hs, which has he po en ial o enable di ec measu emen o magni udes as well as loca ions o o ces ac ing a mul iple poin s along a single ibe . In gene al, hese sys ems a e cha ac e ized by an e o a e o up o ±10 %. The so-called OBW sys ems, which a e ins alled di ec ly on he ehicle can be a much mo e in e es ing subjec . The common goal o he s udies men ioned below is o design ligh weigh senso s and sys em, wi h high accu- acy ha can be easily ins alled in o he exis ing ehicles (ei he di ec ly om he ac o y o e o i ed). The a i- cle [18] desc ibes a capaci i e lexible senso , whose dynamic beha io was desc ibed using he Maxwell-Kel in model. The esul s showed ha he measu emen e o is less han ±10 %. Khei alla e al. [19] deal wi h he de elopmen o an on-boa d weighing solu ion o an indus ial wheel loade o p o ide on- he-go weighing o ucks. Desc ibed measu - ing sys em consis s o he sensing elemen s (s ain gauges), which we e based on h ee locally made load pins ansduce s eplaced he exis ing pins be ween he wheel loade a m and he bucke . Sys em accu acy is wi hin accep able ange limi 0.7 % and 1 % o he measu ed magni udes unde s a ic and dynamic measu emen s, espec i ely. Radoiˆ cić [20] p esen ed a measu ing sys em ha is based on a p essu e senso moun ed di ec ly wi hin a hyd aulic pis on, which is used o li he was e con aine s. Radoicic and o he s [21] desc ibe an al e na i e sys em o con inuous ehicle weigh- ing du ing was e collec ion while in mo ion, which is based on s ain gauges. Thei de ia ions in he measu ed weigh alues ha e no exceeded 0.5 %. The collec i e behind a i- cle [22] desc ibes a sys em whe e he ca go weigh du ing loading is de e mined by he gas p essu e in he suspension cylinde s a he ime o he oscilla ion ending and a he s a o he ib a ion smoo hing p ocess. The weighing e o is de ined by a maximum o 3 %. A icle [23] desc ibes a ehicle on-boa d weighing sys em based on BP (Back P opa- ga ion) neu al ne wo k. The eam ca ied ou an expe imen al measu emen s o uck axles de o ma ion, caused by a ious ehicle loads. The esul s show ha he load measu emen e o is wi hin 5 %. Based on he p e iously men ioned s udies, i can be clea ly decla ed ha a simila app oach ( he use o ibe -op ic senso s) in OBW sys ems has no ye been published. Va ious dynamic was e weighing sys ems a e cu en ly gaining on impo ance and a e o en pa o a newly manu ac- u ed ga bage ucks. Since he ga bage is o en also ga he ed by olde ehicles, a simila sys em mus be e oac i ely ins alled in o hese olde ehicles as well. Uni e sal mea- su ing sys ems can be e y expensi e, wi h p ices eaching up o uni s o ens o housands o dolla s, o example On-boa d ehicle weighing (Hawkley G oup Limi ed, Bo - don Hampshi e, UK), AE Weighing Sys ems (AE Van de Vlie , Tu nhou Belgium). Complex in eg a ion and design changes a e also equi ed ( o u he in o e e o men ioned publica ions). These adjus men s a e spanning om suspen- sion sys em adjus men s o comple e edesigns. These issues we e used as a mo i a ion o he au ho ’s eam o implemen a new simple and e o i iendly sys em o weighing munic- ipal was e. The main pa ame e s o cu en ly used weighing sys ems a e summa ized in Table 1, co e ing he e o a es, whe he he sys em can be e o i ed and whe he i is an ex e - nal (s andalone) o in e nal (ins alled di ec ly in o he ehicle) sys em. TABLE 1. The summa y o esea ched municipal was e weighing sys ems. Ou o iginal weighing solu ion is based on ibe op ic senso s, speci ically ibe B agg g a ings. The en i e sys em can be e o i ed in o a ga bage uck and, due o i s small size and weigh , can be ins alled oge he wi h FBG senso s di ec ly on he ga bage ucks li ing equipmen , wi hou any addi ional modi ica ions o he ehicle. Thanks o he use o powe measu emen s o in o ma ion e alua ion, he ligh sou ce in he o m o Ligh -Emi ing Diode (LED), and con- en ional low-cos FBG senso s he p ice o he whole sys em is app ox. $2000 (coun ing only he necessa y ma e ial). The applicabili y, usabili y and accu acy o he p esen ed sys em is de e mined by an ini ial s udy (4 mon hs) on a eal es ing ga bage uck and s anda d 0-100 kg con aine s. II. ANALYSIS OF SUITABLE PLACES FOR INSTALLATION OF FIBER BRAGG GRATINGS The designed weighing sys em based on ibe B agg g a - ings echnology was es ed on a selec ed commonly used ga bage uck (MAN TGS 28.360 6 ×2-4 BL). The li ing sys em o a ga bage uck is gene ally o med by a s eel ec angula solid p o iles, which a e connec ed by pins and d i en by a hyd aulic pis on. The weighing sys em is based on he mechanical s ess o hese p o iles du ing he emp ying o ga bage bins. This mechanical s ess causes measu able de o ma ions o he p o iles. The in oduc o y pa o he esea ch was mainly ocused on he selec ion o sui able loca ions o B agg g a ings and unde s anding o he dynamic beha io o de o ma ion o ces on indi idual pa s o he li ing sys em du ing he dumping o ga bage bins. The esis ance oil s ain gauges we e chosen as a sui able echnology. Resis ance s ain gauges a e used as a sensing elemen o a ious de o ma ion o ces and a e a s anda d- ized solu ion o de o ma ion sensing. The iNET-555-EU measu ing con ol panel (GW Ins umen s, Cha les own, USA) and SGD-3/350-LY11 (Omega Enginee ing, No walk, USA) esis ance oil s ain gauges we e selec ed o he measu emen s. VOLUME 9, 2021 99051 M. Fajkus e al.: Fibe -Op ic B agg Sys em o Dynamic Weighing o Municipal Was e: Pilo S udy Foil s ain gauges we e ins alled in p eselec ed loca ions, whe e he la ges loads we e p esumed. These loca ions we e p ede e mined by an ea lie simula ion o li ing sys em. Six oil s ain gauges we e i ed di ec ly o he p o iles o he li ing sys em (Fig. 1) – he posi ions a e ma ked as P1 o P6. Th ee oil s ain gauges we e moun ed on he uppe a m o he li ing sys em, while h ee o he we e moun ed on he lowe a m. FIGURE 1. Ga bage uck li ing sys em wi h p ede e mined oil s ain gauges loca ions. Based on an ini ial s udy, a se o epea ed ‘‘emp ying cycles’’ was pe o med on wo ypes o plas ic ga bage bins (ga bage bin A: olume 120 li e s, con aine weigh 10 kg; ga bage bin B: olume 240 li e s, con aine weigh 15kg). Da a ga he ed du ing hese ini ial es we e used as a basis o u he analysis. In he ini ial s udy, he ‘‘emp ying cycle’’ was ca ied ou wi h bo h emp y bins and bins wi h p ede- e mined weigh s (10-100 kg, 10 kg s ep). The ou pu was used o p ede e mine he mos sui able loca ion o he B agg g a ing senso s on he li ing sys em. Based on he analysis o he ga he ed da a - whe e he magni ude o he esponse o de o ma ion, he dependence on he weigh o he ga bage bin con en s and he s abili y du ing he ‘‘emp ying’’ p ocess we emoni o ed-posi ionP5wasselec edas hemos sui able spo o moun ing o he ibe B agg g a ing senso . A ypical wa e o m cap u ed by he oil s ain gauge loca ed a he selec ed posi ion (P5) can be seen in Fig. 2. The example ep esen s he speci ic ‘‘emp ying cycle’’ o 240 l ga bage bin weighing 30 kg. Phase 1 is a ‘‘wa ming up’’ 4 second long in e al, whe e he whole li ing mechanism is es ing. This phase is ollowed by Phase 2, which ep e- sen s he li ing and emp ying p ocesses and can be u he di ided in o h ee pa s. Pa 2a ep esen s he beginning o he li . This sec ion is cha ac e ized by oscilla ion o he li ing sys em, wi h subsequen slow a enua ion in a ime in e al o abou 0.7 s. Pa 2b ep esen s he li ing p ocess, whe e he de o ma ion o he li ing a m a posi ion P5 is a i s maximum, ollowed by a signi ican impac caused by connec ion o he wo main mo ing pa s o he li ing a m. FIGURE 2. A ypical wa e o m cap u ed om he s ain gauge du ing emp ying cycle. Pa 2c ep esen s he las impac o he a m on he s uc- u e o he ehicle, which again causes he li ing sys em o oscilla e. The analyzed da a showed ha he de ec ed de o ma ion a he P5 loca ion is in he measu able ange ±100 µs ain and a e he e o e also measu able by ibe B agg g a ings. III. BRAGG GRATING SENSORS, BASIC PRINCIPLE AND INSTALLATION OF THE DESIGNED SYSTEM A. FIBER BRAGG GRATING (FBG) Fibe B agg g a ing (FBG) is o med by a s uc u e wi h pe i- odic a ia ion in he index o he ibe co e. In his s uc u e, he e ac i e index o he co e n1al e na es wi h an inc eased e ac i e index n3=n1+δn, whe e δnis he induced e ac- i e index which esul s om exposu e o he pho osensi i e op ical ibe o UV ligh . Figu e 3shows he s uc u e and he unc ional p inciple o he B agg g a ing. FIGURE 3. S uc u e and ope a ional p inciple o he B agg g a ing. The s uc u e o he B agg g a ing e lec s a na ow e- quency band o he b oadband ligh and ansmi s he o he s. The cen al pa o he e lec ed spec um is called he B agg wa eleng h λBand is gi en by ela ion (1): λB=2ne 3, (1) whe e ne is he e ec i e e ac i e index o he g a ing in he ibe co e, 3is he g a ing pe iod. O he wa eleng hs a e ansmi ed wi hou a enua ion. The B agg wa eleng h is he geome ic and op ical p op- e ies ha change unde he in luence o mechanical and/o he mal s esses. I is impo an o men ion he equa ion (2), whe e he B agg wa eleng h change, he ela i e de o ma ion 99052 VOLUME 9, 2021 M. Fajkus e al.: Fibe -Op ic B agg Sys em o Dynamic Weighing o Municipal Was e: Pilo S udy and empe a u e change is exp essed by: 1λB λB =kε+(α3+αn)1T,(2) whe e 1λB ep esen s B agg wa eleng h shi , kis de o - ma ion coe icien , εis de o ma ion, α3is he coe icien o he mal expansion, αnis he he mo–op ic coe icien and 1T is change o empe a u e. [24] B. MEASURING POWER OF THE DEFORMATION BY A PAIR OF BRAGG GRATINGS In mul ipoin senso applica ions, he wa eleng h-di ision mul iplexing is one o he mos widely used and simples me hods. This mul iplexing me hod is based on he ac ha indi idual B agg senso s a e made wi h di e en B agg wa eleng hs. The op ical signal e lec ed om se ies o FBG senso sis o med by he sum o pa ially non-o e lapping e lec ion spec a. Moni o ing he p ecise shi o B agg spec- a equi es he employmen o cos ly e alua ion uni , which is o en based on a wide-spec al sou ce, a di ac ion g a ing and a as CCD linea de ec o . [25] The e o e, in case o single-pu pose applica ions wi h a limi ed numbe o FBG senso s, i is o en ad ised o an- si ion o simple powe measu emen s. This measu emen uses he con e sion o he B agg wa eleng h shi o change o he op ical powe . The mos commonly used me hods a e he deploymen o he wa eleng h-dependen il e [1], [2], a wa eleng h-dependen couple [4], [5] o a sys em wi h wo Chi ped B agg g a ings wi h o e lapping spec a [6], [7]. In his a icle, he p e iously men ioned me hod o wo B agg g a ings wi h o e lapping spec a, was used o weigh he was e and educe he long- e m cos s. The scheme o p oposed measu ing sys em (please see Fig.4) used wide-spec um LED (ligh -emi ing diode), ype SLD1550S-A1 1 mW (Tho labs, New on, New Je sey, USA), op ical ci cula o 1550 nm (Guilin GLsun Science and Tech G oup, Guilin, Guangxi, China), pai o B agg g a ings wi h pa ially o e lapping e lec ion spec a wi h pa ame e s men- ioned below. The e lec ed ligh is ed o a pho ode ec o (InGaAs APD G10899-01K 1.55 µm, Hamama su Pho onics K.K, Japan), digi ized by an A/D con e e , and p ocessed by a mic o p ocessing uni ha e alua es he weigh o he was e. The senso pa o he p oposed sys em consis s o a mea- su ing senso (FBGM) and a e e ence senso (FBGR). The measu ing senso is di ec ly a ached (by glue) o he p e i- ously men ioned posi ion (P5) o he li ing sys em, so he de o ma ions om he s uc u e we e ansmi ed o he g a - ing s uc u e o he measu ing FBGM senso . The e e ence senso is ins alled wi h espec o de o ma ion insensi i i y (by app op ia e encapsula ion as de ined below) on he li ing sys em o he ga bage uck. The ad an age o his app oach is au oma ic empe a u e impac compensa ion, because bo h used senso s a e a ec ed by he empe a u e equally. Figu e 5shows he spec a o bo h FBGM and FBGR senso s, whe e he ed colo o he spec um co esponds o FIGURE 4. Scheme o ibe -op ic sys em wi h a pai o B agg g a ings. FIGURE 5. Basic p inciple o a sys em wi h a pai o g a ing senso s whose spec a pa ially o e lap: (a) a measu ing senso in he unloaded s a e; (b) measu ing senso in loaded s a e. he FBGR e e ence senso and he blue colo co esponds o he FBGM measu ing senso . Figu e 5(a) desc ibes he s a e o he spec a when he FBGM measu ing senso is no in luenced by he measu ed de o ma ion (due o he weigh o he was e bin du ing he dumping p ocess). In his case, he e lec ed powe P1consis s o bo h e lec ed spec- a, his powe en e s he e alua ion uni (In e oga o pa ). Figu e 5(b) shows he spec a wi h he loaded FBGM senso (due o he weigh o he ash in he ash bin), which di ec ly co esponds o he inc eased dis ance be ween bo h spec a and he consequen inc ease o he a ea unde bo h spec a cu es. The powe P2(P2>P1) is used o e alua ion. Fo he pu pose o his speci ic measu emen scena io, a linea wo king a ea is used, which is loca ed a he begin- ning o he con e sion cha ac e is ic ( o de ails see Fig. 6). The de e mina ion o a sui able spec al con igu a ion o a pai o B agg g a ings was based on ou p e ious esea ch [26] in he Op iSys em en i onmen . Di e en spec- al wid hs o he B agg g a ings, hei spec al sepa a ion and e lec ance we e chosen o achie e he con e sion cha - ac e is ic app oaching he linea cou se wi h high s eepness and su icien measu ing ange. The ollowing Fig. 7shows he cha ac e is ics o he spec um wid hs o 300 pm, wi h a e lec ance o 95%. This cha ac e is ic ( o a spec um wid h VOLUME 9, 2021 99053 M. Fajkus e al.: Fibe -Op ic B agg Sys em o Dynamic Weighing o Municipal Was e: Pilo S udy FIGURE 6. Con e sion cha ac e is ic o he men ioned measu ing p inciple wi h a linea dependence o he measu ed powe on he de o ma ion. FIGURE 7. Analysis o a sui able spec al spacing o a pai o B agg g a ings usable o achie e he bes possible linea i y o he con e sion cha ac e is ic in he ange om -100 o 100 µs ain. o 300 pm) can be w i en by a linea ela ionship p1ε+p2 wi h he R-squa e pa ame e R2=0.9946, whe e εis de o - ma ion, p1=0.2973, and p2=104.5. I is a combina ion o pa ame e s ha exhibi s accep able p ope ies. Wi h ega d o he linea i y and s eepness o he con- e sion cha ac e is ic and he equi ed measu ing ange o 200 µs ain (see Chap e II), a a ian wi h a spec al spacing o bo h B agg g a ings o 300 pm was chosen. The selec ed con e sion cha ac e is ic shows (in he ange om −100 µs ain o +100 µs ain) a s eepness o 0.3 µW/µs ain wi h R-Squa ed pa ame e o 0.994. The ac ual pa ame e s o he B agg g a ings a ec ed by he p oduc ion me hod can be seen in Table 2. TABLE 2. Pa ame e s o used B agg g a ings. C. INSTALLATION OF FBG SENSORS B agg g a ings in polyimide p o ec ion (SM ibe , G.652.D. s anda d) on one ibe wi h a spacing o 25 cm we e used o FIGURE 8. Diag am o he ga bage uck li ing a m wi h loca ions o FBG senso s ( he ed line ep esen s he op ical ibe , in which he dashed lines a bo h pin A and B ep esen B agg g a ing). he ins alla ion. Polyimide ecoa ing o B agg g a ings was chosen due o he s onge igh ness o he p ima y p o ec ion and he op ical ibe and hus ensu ing he be e ansmission o de o ma ion e ec s o he op ical ibe wi h he FBG s uc u e. The loca ion o he measu ing senso (FBGM) and he e e ence senso (FBGR) on he li ing sys em is shown in Fig. 8and Fig. 9. The FBGM senso is ins alled by a ixed join (Loc i e EA 3430, Düsseldo , Ge many) a posi ion P5 as men ioned in p e ious simula ions. A simpli ied diag am o he li ing de ice can be seen in Fig. 8. The li ing sys em is a ached o he uck by a connec ing pin A. Ano he pin – Pin B – is i ed a he bending poin o he a m. A hyd aulic pis on used o li he whole a m is a ached di ec ly o he pin B. When he a m is li ed by he pis on, he ga bage bin (o con aine ) is aised o maximal heigh and he con aine is emp ied. A FBGR e e ence B agg g a ing is loca ed nea pin A. This speci ic loca ion was picked, since he e a e only e y small de o ma- ions, co esponding o wo o de s o magni ude lowe alues han in he place behind he pin B, whe e he measu ing B agg g a ing FBGM is loca ed. The e e ence FBGR senso was loca ed in he place wi h he smalles de o ma ion, as was de e mined by he p e ious measu emen s, which employed oil s ain gauges. The e - e ence g a ing was also no a ached di ec ly o he su ace o he s uc u e. I was sepa a ed by a se e al millime e laye o oamed polyme ic ma e ial. Due o his loca ion and speci ic a achmen , he ansmission o de o ma ions and ib a ions om he s uc u e o he e e ence g a ing was p e en ed. Due o he ela i ely small dis ance o bo h senso s and he employmen o he p e iously men ioned he mally conduc i e sealan , a compa able he mal s ess o bo h FBG g a ings is achie ed. Du ing he s a ic expe imen al measu emen s, he e we e only e y small empe a u e di e ences in bo h deployed loca ions. Acco ding o he measu emen s, he oscilla ion o empe a u e led o a change in he spec al sepa a ion (be ween FBGRand FBGM) by a maximum o 20 pm. Due o he su icien ly la ge wo king a ea o he ans e cha ac e is- ic (see Fig. 7), hese changes do no a ec he p inciple and 99054 VOLUME 9, 2021 M. Fajkus e al.: Fibe -Op ic B agg Sys em o Dynamic Weighing o Municipal Was e: Pilo S udy FIGURE 9. Ins alla ion o a pai o FBG on he li ing sys em o he ga bage uck. FIGURE 10. The p ocess o emp ying an emp y bin - ma king (blue colou ) he change in powe 1Ppeak o ampli ude me hod. accu acy o he weighing p inciple. In addi ion, he accu acy o weighing is no a ec ed, as he measu emen s o as dynamic phenomena a e no a ec ed by he slowly changing empe a u e. IV. EVALUATION PRINCIPLES Based on he ob ained da a, wo possible me hods o sig- nal p ocessing we e de ined o ind he op imal con e sion cha ac e is ic o he ga bage bin weigh . The i s one is an ampli ude me hod ha moni o s he inc ease in ampli ude du ing emp ying (Fig. 10), while he second one examines he oscilla ion pe iod o he li ing sys em (Fig. 12). A. AMPLITUDE METHOD Ampli ude me hod is based on he inc ease in signal ampli- ude du ing he emp ying p ocess. The moni o ed alue is he di e ence in powe ampli ude 1Ppeak be ween he a e aged alue shi ed o ze o in phase 1 and he maximum alue o Ppeak in phase 2 (o pa 2b) – o u he in o e e o Fig. 2 and Fig. 10. This me hod was used o pe o m a se ies o es measu e- men s du ing he ‘‘emp ying p ocess’’ wi h di e en weigh s spanning om 0 o 100 kg in s eps o 10 kg. Figu e 11 shows he a iance o powe change 1Ppeak and he de ia ions om FIGURE 11. Ampli ude me hod o was e weigh es ima ion: (a) box plo o changes in emp ying p ocess; (b) he de ia ion o he powe change om he a e aged alue o di e en weigh s. he a e aged alue o he powe change using a box plo s o all measu emen s (a o al o 220 cycles o emp ying cycles, 20 o each weigh ). The dependence o he a e age alue o he change in powe on weigh is linea wi h he eliabili y o R2=0.9935. Based on he alue o eliabili y, i is clea ha he a e age alues o pe o mance changes a e linea ly dependen o he weigh o he was e bin con en s. The me hod o con en mass calcula ion can be exp essed by he ollowing equa ion (3): w=0.311Ppeak −33.03.(3) Based on he equa ion (3) and he calcula ed cha ac e is- ics, he ela i e e o o he ga bage bin weigh was es ima ed as 14 %. The men ioned solu ion and he me hod o weigh calcula ion is only app oaching he eal alues – he e o e i is no su icien o was e collec ion op imaliza ion. Fo his eason, a second me hod based on he ib a ion esponse o he li ing sys em was p oposed. B. TIME METHOD A he beginning o he ‘‘li ’’, he cou se o de o ma ion is cha ac e ized by he oscilla ion o he li ing sys em, which is dampened quickly, see Fig. 2(phase 2a). In e ms o mechan- ical ib a ion, he equency o hese ib a ions depends on he magni ude o he igidi y o he li ing sys em and he weigh o he ga bage bin. The basic p inciple o he signal p ocessing can be seen in Fig. 12. The beginning o he wa e o m is cu , so ha a sec ion o 40 ms be o e he i s VOLUME 9, 2021 99055 M. Fajkus e al.: Fibe -Op ic B agg Sys em o Dynamic Weighing o Municipal Was e: Pilo S udy oscilla ion is s ill p esen . Subsequen ly, an o se shi is applied on he y-axis o he alue o 0. Then he ea pa o he signal is cu o , so ha only an in e al o 0.7 s is le . In he nex phase, local maxima (posi i e peaks) a e iden i ied, ime in e als be ween adjacen maxima a e calcula ed and hese in e als a e a e aged. The same p ocess is ca ied ou wi h local minima (nega i e peaks). FIGURE 12. Basic p inciple o ime me hod wi h local posi i e/nega i e peaks, which a e used o de e mina ion o he oscilla ion ime pe iod o li ing sys em. This me hod was also used in simila scena io as in he p e iously men ioned ampli ude me hod (emp ying ga bage bins weighing om 0 o 100 kg wi h s ep o 10 kg). Ga he ed da ase was used o de e mine he dependence o he oscilla ion ime pe iod on he weigh o he was e. Figu e 13 shows he a iances o he oscilla ion pe iod and he de ia ion om he a e aged alue. The oscilla ion pe iod is calcula ed as he a i hme ic mean be ween he pe iods ob ained om posi i e local maxima and he nega i e local maxima. The dependence o he a e age alue o he change in powe on weigh is linea wi h he eliabili y o R2=0.996. Based on he alue o eliabili y, i is clea ha he a e age alues o pe o mance changes a e linea ly dependen o he weigh o he was e bin con en s. The me hod o con en mass calcula ion can be exp essed by he ollowing equa ion (4): w=0.921T−116.15.(4) Based on he equa ion (4) and he calcula ed cha ac e is- ics, he ela i e e o o he ga bage bin weigh was es ima ed as ±6 %. The p esen ed solu ion o municipal was e weighing is compa able o comme cially a ailable solu ions and shows a p omising solu ion o was e collec ion op imaliza ion, while also o e ing signi ican ad an ages such as simple ins alla ion and much lowe p ice. V. LONG-TERM TESTING The e i ica ion o he unc ionali y and i s accu acy was ca ied ou du ing a 4-mon h pilo s udy, in which he sys- em was subjec ed o a o al o 2589 emp ying cycles wi h a p e iously known weigh o was e in ga bage bins. This long- e m measu emen was no ca ied ou in eal condi ions, since i was necessa y o know he exac weigh o he was e o de e mine he quali y pa ame e s ela ed o he accu acy and FIGURE 13. Time me hod o was e weigh es ima ion: (a) box plo ep esen ing changes in ime pe iods du ing emp ying p ocess; (b) he de ia ion o he pe iod change om he a e aged alue o di e en weigh s. ep oducibili y o he weighing. The long- e m measu emen was ca ied ou in he backg ound o he company ha p o- ides was e collec ion. The expe imen al se up was he same as in he analysis o he weighing p inciple in he p e ious Chap e . A ga bage uck (MAN TGS 29.360 6 ×2-4 BL) wi h a pai o B agg g a ings ins alled on he li ing de ice was used o he mea- su emen (see Fig. 9). The signal om he B agg g a ings was ou ed ia an op ical cable o he e alua ion uni loca ed in he ea o he ehicle. The op ical signal is hen con e ed o an elec ical digi al signal using a con en ional pho ode ec o and an A/D con e e wi h sampling equency o 500 Sps. This disc e e signal is p ocessed in he µPC uni and he es ima ed weigh o was e in he con aine is s o ed in he in e nal memo y (Fig. 4). A 120 l was e collec ion con aine wi h a ious es weigh s om 10 o 100 kg was used o es he sys em. The esul s o he 4-mon h pilo s udy can be seen in Fig. 14. Fig 14(a) shows all measu emen s, whe e each poin ep esen s one ga bage dump p ocess. The dependence o he es ima ed weigh and he ac ual weigh co esponds o a linea dependence wi h he R pa ame e o 0.9937. Fig. 14(b) shows he a iance o he weighed weigh s, whe e he x-axis shows he a e age alue o he es ima ed and ac ual weigh s, while he y-axis shows he di e ence be ween he es ima ed weigh and he ac ual weigh . The igu e shows he con idence band ±1.96 SD (S anda d De ia ion) wi h a wid h o 8.09 kg and i s mean sys ema ic e o o −0.24kg. 99056 VOLUME 9, 2021 M. Fajkus e al.: Fibe -Op ic B agg Sys em o Dynamic Weighing o Municipal Was e: Pilo S udy FIGURE 14. Resul s o was e weighing om a 4-mon h long- e m measu emen . (a) dependence o he measu ed weigh s o he was e on he ac ual dump weigh ; (b) absolu e weighing e o ; (c) ela i e weighing e o ; (d) ep oducibili y o he weighing sys em scena io, de e mined by he a iabili y o he da a se ou lied by a s anda d de ia ion. The esul s show ha 97.91% o he measu emen s lie in he con idence band o andom e o s. Only in case o 54 dumps ou o a o al o 2589 is he e o g ea e han he band de ined by wice he s anda d de ia ion. Fig. 14(c) shows he ela i e weighing e o ela i e o he ac ual weigh o he dumped was e. Weighing accu acy o weigh s up o 20 kg shows a ela i e a e age e o o app ox. 16%, while he weigh s o up o 50 kg eached app ox. 7%, and weigh s o e 80% eached app ox. 5%. Due o he lon- e m measu emen , which was sp ead o e a pe iod o 4 mon hs (Sep embe o Decembe ), i is no possible o speci y he epea abili y o he measu emen , bu he ep oducibili y o he measu emen , which indica es he a iabili y o he weighing, can s ill be epea ed. Fig. 14(d) shows he weighing a iabili y by he s anda d de ia ion. The s anda d de ia ion was calcula ed o all weighed weigh s ounded o he nea es kilog am. The epe i ions o each weigh o was e we e di e en and anged om 13 o weigh o 100 kg o 47 epe i ions o a weigh o 59 kg. The smalles s anda d de ia ion o 1.268 occu s a a weigh o 21 kg, while he la ges s anda d de ia ion o 2.993 us a a weigh o 98 kg. The p esen ed weighing sys em shows a weighing accu- acy o ±4.04 kg wi h a mean alue o -0.24 kg in 97.91% o was e dumping p ocesses. Based on a 4-mon h expe imen , a o al o 140 682 kg o was e was dumped in epea ed es cycles. In e ms o absolu e alues, a o al o 140 062 kg was measu ed by he ins alled ibe op ic weighing sys em. The di e ence was he e o e only 620 kg, which ep esen s a di e ence o 0.44% compa ed o he eal es ing weigh o he was e. The e alua ion sys em was du ing long- e m measu e- men s loca ed in he ea o he ehicle, whe e he s o age space o he ehicle ope a o is de ined. This minimized he necessa y dis ance o he in e connec ing op ical ibe si ua ed be ween he senso pa and he e alua ion pa ( his dis ance was app ox. 2m). The encapsula ion o he used op ical cable (G.657.D) in o a polyme ube wi h Ke la wi h an ou e diame e o 3mm gua an ees ha he sys em is esis an o ex e nal in luences (wea he ) and mechanical damage. The 2m op ical ibe ensu es ha he a enua ion o he ibe is a negligible alue. VI. DISCUSSION This publica ion desc ibes an in oduc o y s udy e i ying p ima ily he p inciple o unc ionali y and a possible new di ec ion in he de elopmen o a ibe op ic sys em o weighing municipal was e when emp ying ga bage bins. The men ioned solu ion can be addi ionally implemen ed on he li ing sys em o any comme cial ga bage uck wi hou any addi ional s uc u al modi ica ions o he ehicle, which is a signi ican ad an age. Howe e , i should be no ed ha due o he complex issues o his p oposed solu ion, he esea ch and long- e m es ing was ca ied ou on a selec ed (commonly used) ype o ga bage uck. In case o o he ypes o li ing equipmen , i migh be necessa y o speci y mo e sui able places o he ins alla ion o FBG senso s and o calib a e he sys em again. The au ho ’s eam is now ocusing on his speci ic a ea. Long- e m es ing was pe o med wi hin he es polygon and he esul s we e p esen ed o local companies dealing VOLUME 9, 2021 99057 M. Fajkus e al.: Fibe -Op ic B agg Sys em o Dynamic Weighing o Municipal Was e: Pilo S udy wi h he collec ion o municipal was e. Discussions on he deploymen o his solu ion on a pilo es ca in eal ope a ion a e cu en ly unde way. The sys em will be supplemen ed wi h a GPS module and an iden i ica ion code eade in o de o c ea e a comp ehensi e solu ion o moni o ing he amoun o municipal was e in o de o educe cos s and s eamline was e collec ion. The p ice o he whole sys em, including measu ing sen- so s, is app ox. $ 2000, coun ing only he necessa y ma e ial. The au ho ’s eam is awa e o he ac ha a sys em o dynamic weighing o was e is nowadays a pa o newly man- u ac u ed ga bage ucks. Ne e heless, i should be no ed ha he majo i y o companies s ill employ ca s wi h an olde p oduc ion da e, which in he case o deploymen o dynamic weighing sys em equi e addi ional ins alla ion o cus omized equipmen . Uni e sal measu ing sys ems can be expensi e, wi h p ices eaching up o ens o housands o dolla s, o example On-boa d ehicle weighing (Hawkley G oup Limi ed, Bo don Hampshi e, UK), AE WEIGHING SYSTEMS (Tu nhou Belgium). Two weigh e alua ion app oaches a e discussed - he ampli ude me hod analyzing he maximum change in signal ampli ude and he me hod analyzing he ime pe iods o damped oscilla ions in he signal. In bo h cases, he HW con- igu a ion was he same, only he e alua ion algo i hm behind he A/D con e e was changed. The esul s om he ampli- ude app oach o signal p ocessing show ha he amoun o de o ma ion o he a m o he li ing de ice inc eases wi h inc easing weigh o he was e. Howe e , om he poin o iew o weighing accu acy, he au ho ’s eam ecommends using he ime app oach o da a p ocessing, in which a highe accu acy was achie ed and main ained. VII. CONCLUSION This publica ion summa izes he esul s o an ini ial pilo s udy desc ibing he design, implemen a ion and e i ica ion o a new ibe op ic sys em based on ibe B agg g a ing o weighing municipal was e. The p esen ed sys em can be addi ionally implemen ed on he li ing sys em o commonly used ga bage ucks. The p inciple o weighing is based on he measu emen o de o ma ion e ec s and ib a ion esponse o he li ing equipmen o ga bage ucks du ing he dumping o ga bage bins. Two weigh e alua ion app oaches a e discussed - he ampli ude me hod analyzing he maximum change in signal ampli ude and he me hod analyzing he ime pe iods o damped oscilla ions in he signal. 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Ma inek, ‘‘Pa ame e analysis o a pai o B agg g a ings wi h o e lapping spec a o powe measu emen o small de o ma ions,’’ Op oelec on. Ad . Ma e . Rapid Commun., ol. 13, pp. 168–174, Ma ./Ap . 2019. 99058 VOLUME 9, 2021