3rd Interntonl Conference on Mterls Engneerng, Mnufcturng Technology nd Control (ICMEMTC 016) Shelf System Loclzton Algorthm Reserch bsed on RFID Technology L Zhu1,, Jn Ln Lu,b 1 College of Mthemtcs nd Computer Scence, Jngx Scence nd Technology Norml Unversty, Nnchng, Chn College of Mthemtcs nd Computer Scence, Jngx Scence nd Technology Norml Unversty, Nnchng, Chn bln_198@sn.com, bljln081@163.com Keywords: Loclzton lgorthm; RFID technology; Smrt shelves; Reference lbel; Dtbse Abstrct. Wth the rpd development of nformton technology, rdo frequency technology pplcton hs become n mportnt symbol of ntellgence relzton. Accordng to the requrements of ntellgent bookshelf system, ths pper nlyzes nd desgns ntellgent bookshelf system structure from two spects of hrdwre nd softwre. In determnng postonng lgorthm of ntellgent bookshelf system, nlyze the clssfcton of ndoor locton lgorthm nd dvntges nd dsdvntges of vrous lgorthms, select RFID ndoor loclzton lgorthm becuse of ntellgent bookshelf system s ctul demnd for locton selecton, nd mprove t on the bss of LANDMARC system lgorthm. Anlyze from receved power selecton, reference lbel dstrbuton, nerest neghbors number set nd lgorthm weght set nd so on, desgn books ccurte loclzton lgorthm scheme, nd mke experments to test the expermentl dt nd lgorthm vldton to effectvely mprove smrt shelves system book postonng ccurcy. I. INTRODUCTION Lbrry s the mportnt plce for us to obtn knowledge. Only wth constntly updted knowledge cn we keep up wth the pce of The Tmes. Book collecton number nd ctegores chngng mke the lbrry work under pressure: people hve choce of trgeted redng, nd t the sme tme, the lrge number of books hs ncresed the dffculty of lbrry mngers nd reders query nd retreve books. Wreless rdo frequency dentfcton technology s ncresngly mture whch wdens the scope of ts pplcton. Ths technology cn be ppled n lbrry mngement to gretly enhnce servce qulty nd mprove work effcency. II. SMART SHELVES SYSTEM RFID technology s knd of non-contct utomtc dentfcton technology bsed on wreless communcton technology. It utomtclly dentfes trget object through rdo frequency sgnl trnsmsson nd ccesses to relevnt dt nd provdes t to bckground computer processng system for correspondng dt processng [1]; Smrt shelves system s knd system equpped wth RFID reders, RFID lbel nd RFID trnscever ntenns. Reder cn detect nd locte the ctul locton shelf of the books t ny tme, nd t s set of ntellgent nd dgtl books mngement system mngement system for rel-tme books nd locton dt nformton processng nd book poston locton by reder nd computer connecton []. Lbrry ntellgent bookshelf system mnly hs four prtcptng enttes: reders, ntellgent bookshelf ontology, lbrrns nd lbrry lterture to fcltte prt entty mngement operton, mxmlly mprove the performnce of ntellgent bookshelf system, nd mprove the performnce of the system[3]. Intellgent bookshelf system entty reltonshp dgrm s shown n Fgure 1: 016. The uthors - Publshed by Atlnts Press 1475
Reder Postonng termnl nqury User Informton Mngement t Smrt g shelves v n s k o B e h n t o t o t g v g n n o l t e f b r s c k r o B Owned by the whole rcrft Countng the scrutny Admnstrtor Self-help books borrowed Bblogrphc regster Purchse Ctegores The book lterture Fgure 1 System entty reltonshp dgrm One of mportnt steps of system nlyss nd desgn s to buld system use cse model. System use cse s to mke functonl descrpton of system from the ngle of the user, nd descrbe the connecton between system nd system prtcpnts. III. INTELLIGENT BOOKSHELF SYSTEM LOCALIZATION ALGORITHM Accordng to the dfferent wy of postonng, RFID ndoor loclzton lgorthm s dvded nto three ctegores: sgnl rrvl tme loclzton lgorthm, sgnl rrvl ngle postonng lgorthm nd receved sgnl strength postonng lgorthm [4]. A. Sgnl rrvl tme loclzton lgorthm Sgnl rrvl tme s TOA. The loclzton lgorthm uses movng trgets nd mesures rnge wreless sgnl propgton tme to determne the locton, whch s to determne the locton of the object by mesurng trvel tme or the tme dfference of electromgnetc wve from luncher propgton to multple recevers devces [5]. Assume sgnl propgton tme between the movng trget nd bse stton s t, then the dstnce between them cn be represented wth r = vt. Becuse RF sgnl speed vlue n the r s lmost Gungsu C, use the followng formul to clculte the dstnce between the movng trgets to the mesure devce: r =c (t -t 0 ) (1) Fgure s TOA lgorthm dgrm. Fgure TOA lgorthm dgrm ( s the bt of three crcles ntercton, b s the multpont of three crcles ntercton) By movng three mesurng devces closer to the trget dstnce, get three dstnce vlues nd the movng trget poston coordntes cn be clculted. By the nture nd formul of crcle e = (x - x0 ) + ( y - y 0 ), solve (x n, y n ) coordntes wth the smultneous equtons obtned; In ctul stuton, locted regon my not nterct to one pont, s s shown n Fgure b, nd TOA lgorthm hs extremely hgh requrements for the synchronzton of trnsmtters nd recevers. There s need to dd tme dentfcton to the sgnl nd postonng devce ponts should be t 1476
lest three or more, so ths wll nevtbly cuse some errors; To mprove the postonng precson, other lgorthms should be ntroduced for poston compenston, but the system cost nd the complexty of lgorthm lso ncrese, so TOA s not sutble for the condtons of ntellgent bookshelf system postonng. B. Sgnl rrve ngle postonng lgorthm Wreless rdo frequency sgnl lunched by the movng trget s mesured by ntenn rry. Recevng devce mesures electromgnetc wve ncdent ngle nd forms locton lne from the luncher to recever to determne the drecton of the movng trget locton nd mplement postonng ccordng to the sgnl rrve ngle. Ths s AOA locton [6]. The dvntge of sgnl rrve ngle postonng lgorthm s tht t only needs two reference ponts to determne the trget locton, nd there wll be no postonng fuzzy phenomenon wth multple ntercton ponts n the movement pth; But AOA locton hs hgh requrement on the hrdwre. Hrdwre equpment s complex nd precson s gretly ffected by envronment multpth effect, so, n order to mesure ncdent ngle ccurtely, not only mprove recever ntenn, lso nstll drectonl ntenn rry. C. Receved sgnl strength postonng lgorthm Typcl postonng lgorthm pplcton systems bsed on recevng nformton strength re RADAR system nd LANDMARC system [7]; RADAR system s the erlest use of wreless rdo frequency sgnl recevng strength RSS to develop RFID ndoor postonng system. Ths pproch hs pplcton lmttons, nd s mnly ppled n two stutons: one s the need to combne wth other reltve postonng technologes to mprove the ccurcy of postonng; The second s ppled to not hgh user requrements for postonng ccurcy, such s the movement of the trget rnge, etc.; RADAR postonng prncple s very smple, nd ts system model cn be clculted by expermentl dt, nd cn be derved through experence theory; Wth combnton of experence system testng nd sgnl trnsmsson model, t requres less nformton reference ponts, nd the bottom wreless network structure desgn s smple nd convenent for system nstllton; Compred wth TOA lgorthm, the loclzton lgorthm bsed on RSS s less ffected by the ndoor envronment multpth effect, but n ndoor envronment, rdo frequency sgnl propgton model s complex, RADAR system postonng ccurcy bsed on RSS s low. LANDMARC system s bsed on ctve RFID electronc lbel sgnl strength s ndoor locton dentfcton system. It uses reference lbel s the system s reference postonng pont for uxlry orentton, nd estmte dstnce by obtnng sgnl strength vlue of reference lbels nd lbels under test to rel-tme forecst the locton of the object under test [8]. Loctng method s the commonly used mesurng postonng wy t present for ndoor postonng. System pstes reference lbel n ndoor needs to locte the poston of the known coordntes nd records electromgnetc wve sgnl ntensty lunched by reference lbel wth reders n fxed poston. When the under test trget lbel gets to postonng rdton re, reder detects the energy vlue sent by the trget lbel. It lso s the comprson of receved sgnl strength vlue nd the RSS vlue sent by the recorded reference lbels. Through certn locton coordntes clculton, determne the poston nformton of the under test trget. IV. EXPERIMENTAL SIMULATION ANALYSIS A. RFID ndoor postonng prncple RFID ndoor locton mproved the technology of LANDMARC system, nd mproved the postonng ccurcy by chngng reder dstrbuton nd quntty, doptng pssve lbels, determnng reference lbel dstrbuton nd quntty, nd mprovng lgorthm process n order to sut the postonng requrements of lbrry envronment ntellgent bookshelf system; A bsc wreless rdo frequency postonng system usully conssts of three prts: dt redng cquston devce, locton estmton loclzton lgorthm nd front end poston dsply pplcton progrm [9]. RFID ndoor postonng system s workng prncple s: frst, the user ssues the locte request, nd the system sends request nd submts t to the reder. The reder sends rdo frequency sgnls by rdton power to ctvte electronc lbels. Lbels return memory nformton or sgnl strength nformton through rdo frequency sgnl to reder, nd then select loclzton lgorthm. 1477
Mke poston estmton through the sgnl nformton of dfferent mesurng tme, ngle, nd receved sgnl strength of TOA nd AOA, RSS lgorthms. Clculte the under test trget locton coordntes wth neurl network, nerest neghbors lgorthm, probblty clculton method, nd wth trnsformton use dsply system for users to red. B. The settng of loclzton lgorthm prmeters (1) Reference lbel dstrbuton Pendng lbel locton s fnlly locted bsed on severl references lbel poston dstrbuted round t, so reference lbel dstrbuton method wll ffect the ccurcy of the lgorthm. The ntellgent bookshelf system postonng s ccurte to bookshelf mnmum cell. Tke mnmum cell of the shelf s the reserch object, nd then expnd the whole bookshelf. Assume evluton poston precson prmeters re the verge poston error, nd the expresson cn be expressed s: M 1 MEE = ( x x 0 ) + ( y y 0 ) () M The ctul locton coordntes of the under test lbel s (x0, y0). Loclzton lgorthm s used to get the estmton coordntes (x, y). M s the number of expermentl smulton. Tke second order weght s the weght for respectve smulton, nd the verge poston error got s shown n Tble 1. Reference lbel number Tble 1 Dfferent reference lbel number verge poston error tble Averge poston error Reference Averge poston /m (100 tmes) lbel error/m (100 tmes) number 6 0.0650 1 0.043 7 0.0551 13 0.055 8 0.0335 14 0.0610 9 0.0495 15 0.0650 10 0.056 16 0.0687 11 0.0455 Fgure 3 s error dstrbuton for dfferent lbel number. Fgure 3 Dfferent reference lbel number error dstrbuton Through smulton nlyss, when the reference lbel number s 8, there s the smllest verge poston error. The verge orentton error of 100 tmes s 0.033 m, so pste reference lbel on bookshelf mnmum cell s eght pex ngles, nd two djcent cells use four reference lbels on the connecton surfce. () The nerest neghbors lbel number set The number of nerest neghbors lbel decdes the number of reference lbels nvolved n clcultng n system lgorthms, whch cn sgnfcntly ffect the coordntes of the trget lbel under test. The number of nerest neghbors lbels cn be one, two or more. These lbel coordnte vlues eventully determne the poston of the trget lbel ccordng to certn weght proporton sum. Ths lgorthm s clled KNN nerest neghbor lgorthm; lrger error reference lbels my brng greter error when postonng coordntes clculton weght n order to mprove the poston 1478
precson of the system lgorthm, so consder the determnton of nerest neghbors lbel number k vlue n demnd nlyss. Accordng to under test lbel sgnl strength vlue nd reference lbel sgnl strength vlue, obtn Euclden dstnce vector E to regulton sequence. Mke weghted the mnmum Euclden dstnce reference lbel poston coordntes wth under test lbel. Expermentl results show tht f k vlue s too lrge or too smll, t ws not vled to mprove the precson of postonng, so determne the sze of the k vlue through specfc experments. Through dt nlyss, when the number of nerest neghbors lbels s 8, verge poston error mount s the mnmum. The verge error of 100 tmes orentton s 0.039 m, nd k vlue s 8 to fcltte delmt the smllest scope. Lmt the lbel under test wthn the smllest cell of frst lyer of the shelf. Ths mproves the exstng ntellgent bookshelf whch only lmts fult plne books n one lyer nd mproves the postonng precson. (3) Determne the nerest neghbors lbel weghts There re mny wys to determne the nerest neghbors lbel weghts, but they must stsfy two bsc condtons: ownershp weghts weghtngs sum must be 1, whch s ccord wth W1+W+...+Wk=1; weght W must be monotony decrese functon, nmely f reference lbels nd the Euclden dstnce E of lbels under test re lrger, weght W of reference lbels must be smller. Commonly used wys of weght settng re one order weghts vlue, second order weghts vlue nd rght logrthmc weghts vlue; trget lbel locton vlues got by dfferent weghts settng methods re not the sme. In order to cheve hgh precson postonng effect, nlyze the nfluence of dfferent weghts settng methods on lbel locton coordntes. Frst defne vrble to descrbe the poston nd sgnl ntensty of under test lbel, clculte close degree of mnmum E vlue reference lbel wth Euclden dstnce. So sngle lbel dependent fctor s ξ, nd the expresson s s shown n Formul (3). W ξ= ( ) mx (3) When the under test lbel sgnl chrcterzton dstnce E s of the sme vlue, the bgger lbel dependent fctorξ shows the greter sngle lbel dependence, tht s to sy tht the clculted under test lbel poston s closer to the lrgest weght nd the nerest neghborng reference lbel poston. By nlyzng, t s known tht qudrtc weghtng settng method s sngle lbel dependence s on the hghest degree. Ths mens tht lbel locton coordntes re closer to the nerest neghbors coordntes, nd logrthmc weghtng settng method hs the lowest sngle lbel dependence. The loclzton lgorthm dopts qudrtc weghtng weghts; ech reference lbel hs weght W, nd the bgger weghts mens tht t s the closer to the under test lbel. C. Anlyss of expermentl results Experments re done to vldte the effectveness of ntellgent bookshelf loclzton lgorthm. Locte wthn four djcent mnmum cells of two sdes of ntellgent bookshelf frst floor n the lbrry. Select the mnmum cell sze s 1.0 m * 0.5 m * 0.5 m, nd pste eght reference lbels respectvely on eght cell vertex ngles of the mnmum cell. Publclly use four lbels t djcent two unts jonts. Wthout consderng sptl coordntes n the vertcl drecton, descrbe the under test coordntes vlue, whch s shown n Tble : Tble Under test lbel s ctul coordntes Under test lbel Coordntes Under test lbel Coordntes 1 (0.5, 0.5) 5 (0.7, 0.75) (0.50, 0.30) 6 (1.5,0.63) 3 (1.05, 0.5) 7 (1.68, 0.80) 4 (0.45, 0.80) 8 (1.75, 0.90) Under test lbel estmton poston coordntes clculted by lgorthm smulton s s shown n Tble 3: 1479
Tble 3 Under test lbel estmton poston coordntes Under test lbel Rel coordntes Under test lbel Rel coordntes 1 (0.3, 0.) 5 (0.70, 0.7) (0.47, 0.8) 6 (1.4,0.63) 3 (1.03, 0.1) 7 (1.64, 0.79) 4 (0.48, 0.8) 8 (1.77, 0.93) The verge poston error of under test lbel obtned by clculton s 0.036 m. Intellgent shelves loclzton lgorthm gets hgher postonng ccurcy nd stsfes the reders demnd to locte books to mnml cells. V. CONCLUSION Wreless rdo frequency dentfcton technology s new postonng nformton cquston nd processng technology, whch s wdely used n logstcs mngement, retl nd other vrous felds. In order to mprove the effcency of reder's borrowng nd lbrrns' work effcency nd relze ntellgent mngement nd mprove lbrry servce level. Compred wth the exstng ntellgent bookshelf, ntellgent bookshelf system postonng precson lgorthm hs gretly mproved ccordng to lbrry envronment nd reder poston needs. From books loctng shelf one floor to bookshelf mnmum cell, t reduces the complexty of the system, nd reduces the system cost. It lso cn effectvely smplfy books borrowed process nd mprove the utomtc dentfcton nd rpd postonng blty of books. REFERENCE [1] L Wefeng, Wng Dong. Indoor locton technology reserch bsed on RFID [D]. Shngh: Shngh Jotong Unversty, 010 [] Tn Zhongdng. Rfd trckng technology lbrres dsorderly frme strtegy comprson [D]. Journl of Gungx Acdemy of Scences, 011 [3] Chen Congchn, He Lnglun. Regonl refnement of RFID ndoor loclzton lgorthm [J]. Journl of Computer Applctons nd Softwre, 011 [4] Chen Bng, Lu Khu, Sh Wegung. Vrtul lbel mproved lgorthm bsed on RFID [J]. Computer Engneerng, 011 [5] Yo Yun. The pplcton reserch of RFID technology n unversty lbrry [D]. Shngh: Shngh Jotong Unversty, 011 [6] Zho Jnglng, Yo Jnje, Su Xnyn. Indoor postonng system desgn bsed on rdo frequency dentfcton [J]. Computer Mesurement nd Control, 011 [7] Tn Hengy. Insnty open-shelf books borrowng nd redng phenomenon countermesures n unversty lbrry [J]. Chn's Economy nd Trde, 010 [8] Jng He, Go Hu. The lbrry nformton mngement system bsed on RFID [D]. Chengdu: Unversty of Electronc Scence nd Technology, 010 [9] Zhng Yusong, Du Jngln. Lbrry ntellgent bookshelf scheme reserch nd desgn bsed on uhf RFID. Nnjng Informton Engneerng Unversty Lbrry. Nnjng. Lbrry Journl. 014 [10] Chen We, Shen Zeqn. Dt vsulzton [M]. Bejng: Electronc Industry Press, 013 [11] M Xotng. Lbrry dt vsulzton nlyss system desgn nd mplementton. Lnzhou Informton Engneerng College, 015 1480