CROSSTALK ANALYSIS FOR HIGH-PRECISION OPTICAL PICKUP ACTUATOR SYSTEM

Jounal o Theoeial and Applied Inomaion Tehnology h Apil 2. Vol. 5 No. 25-2 JATIT & LLS. All ighs eseved. ISSN: 992-8645 www.jai.og E-ISSN: 87-95 CROSSTALK ANALYSIS FOR HIGH-PRECISION OPTICAL PICKUP ACTUATOR SYSTEM QINGXI JIA, * ZHIZHENG WU, YANG LI, MEI LIU Depamen o Peision Mehanial Engineeing, Shanghai Univesiy, Shanghai, China, 272 * E-mail: zhizhengwu@shu.edu.n ASTRACT The adiional opial pikup auao model based on he assumpion ha he auao spaial magnei ield disibues uniomly ignoes he ossalk haaeisi among he movemens o dieen dieions. Cossalk haaeisi is a key ao ha aes he auao dynami popey and, onsequenly, he auay o eading and wiing opeaion in he uue highe densiy opial soage sysems. In his pape, he auao spaial magnei ield disibuion model is is esablished, hen he ossalk movemen phenomenon o he auao is analyzed and simulaed in CST sowae based on inie-dieene ime-domain (FDTD) piniple. y invesigaing he paamees o he widh and heigh o he pemanen magne and he hikness o he ousing oil, i is onluded ha he ossalk haaeisi is losely elaed wih hese suual paamees and ossalk an be eeively edued by opimal design o hem, hus, he dynami peomane o he auao an be impoved. Keywods: Cossalk Chaaeisi, Opial soage, Highe densiy, Suual Paamees Assuming he auao spaial magnei ield. INTRODUCTION disibues uniomly, he adiional auao model Wih he densiy o opial disk soage and daa anse speed oninuing o inease, he equiemens o he auao movemen auay and dynami peomane in high-peision opial soage sysems beome highe and highe. The disane beween he objeive lens and dis will dop down o less han nm o he nex geneaion nea ield opial soage sysems [], whih neessiaes a even demanding posiion auay. Cossalk haaeisi beween eah movemen dieion in he adiional pikup auaos no only esuls in he delining o he eading and wiing auay, bu also ould ause a ollision beween he objeive lens and he disk. In he wo-dimensional auao as shown in Figue, he movable pas ae suppoed by boh he suspension wies and he eleomagnei oe and peom he wo-dimensional movemens, inluding ousing movemen and aking movemen. The ousing movemen makes he objeive lens move in he dieion pependiula o he opial dis suae o ensue he ousing spo ousing on he dis suae auaely. Taking movemen an eeively onol he objeive lens o move in he dieion paallel o he opial dis suae [2]. simply onsides he movemens o he aking and ousing dieions sepaaely and heeoe he ossalk haaeisi beween eah movemen is ignoed. Sine he ousing and aking movemens ollow he same piniple in he low equeny ange, he movemen in eah dieion usually is simpliied as a one-dimensional mass-sping-dampe sysem, as shown in Figue 2 [-4]. Howeve, his adiional model based on he uniom magnei ield is no longe applied in he uue highe densiy opial soage sysem. In his pape he non-uniom magnei ield and he oss-oe applied o he movable omponens o auao ae analyzed, and he ossalk haaeisi is uhe simulaed in CST sowae based on FDTD piniple. Fig Two-Dimensional Wie Auao 682

Jounal o Theoeial and Applied Inomaion Tehnology h Apil 2. Vol. 5 No. 25-2 JATIT & LLS. All ighs eseved. ISSN: 992-8645 www.jai.og E-ISSN: 87-95 Fig. 2 One-Dimensional Mass-Sping-Dampe Sysem Model 2. SPATIAL MODEL OF MAGNETIC FIELD The oe on he auao is deided by he disibuion o he eleomagnei ield. Theeoe, he analysis o he eleomagnei ield is iial o opimize he dynami haaeisi o he auao [5-7]. Geneally, he wo-dimensional wie auao's spaial magnei ield is mainly omposed o a magnei ield geneaed by wo pemanen magnes, a magnei ield geneaed by he ousing oil and a magnei ield geneaed by he ou aking oil, as shown in Figue. In iniial sae, he pemanen magnes, he ous oil and aking oil shae one geomei ene denoed as poin O ( x, y, z ). When hey move away om he enal i i i i loaion, hei geomei enes will be denoed as Oi( xi, yi, z i) O ( x, y, z ) O ( x, y, z ), espeively. 2. SPATIAL MAGNETIC FIELD MODEL OF PERMANENT MAGNET Fig. Diagam O The Auao Coils Fig. 4 Auao Pemanen Magnei Aoding o he heoy o medium magneizaion, M was egaded as a hypoheial magnei hage densiy while ompuing he magnei ield o he pemanen magne. In he pemanen magne whih is magneized uniomly, suae hage only exi on he ineae o magnei medium. Suae magnei hage densiy σ is σ = M n () The pemanen magne auao is shown in Figue 4. Assuming he pemanen magnes ae uniomly magneized, he wo opposie suaes Ⅱ Ⅲ ae magneized as N pole, he ohe wo suaes Ⅰ and Ⅳ ae magneized as S pole. Aoding o he equivalen magnei hage mehod, uni magnei hage a he poin P ( x, y, z ) on he suae geneaes magnei lux a any poin in he spae. The magnei induion o any poin Pxyz (,, ) geneaed by he poin P( x, y, z ) on he suae Ⅰ, an be expessed as: σ d = da (2) whee = ( x x) i+ ( y) j+ ( z z) k an be ompued aoding o he magnei ield supeposiion piniple. da is he suae inegal o suaeⅠ. Magnei ield disibuion geneaed by suaeⅠ is: m2 n2 σ dydz = 5 m n () σ m2 n2 ( x x) i + ( y) j + ( z z) k = 5 dydz m n whee m = y a /2, m = y + a /2, n = z + b /2, n = z + b /2. i i 2 i i i i 2 i i The magnei ield geneaed by he pemanen magne is he sum o he ou magnei ield geneaed by he suaes Ⅰ, Ⅱ, Ⅲ and Ⅳ 4 = = i+ j+ k (4) Denoe i n ix iy iz n= m2 n2 = F m, d n A dd y z w= xyz,,, F Ⅰ Ⅱ Ⅲ Ⅳ, hen 4 σ ( x xn ) w da 5 n F = n n =, = (5) 68

Jounal o Theoeial and Applied Inomaion Tehnology h Apil 2. Vol. 5 No. 25-2 JATIT & LLS. All ighs eseved. ISSN: 992-8645 www.jai.og E-ISSN: 87-95 2.2 Spaial Magnei Field Model O Fousinging Coil Coils o auao ae wounded by exellen onduo. The analysis an be peomed aoding o he eleomagnei ield podued by he uen soue. Fig.5The Suue O The Fousing Coil io-sava law saes ha he magnei induion d o any poin p geneaed by he uen elemen I dl is popoional o he uen elemen, and popoional o he sine o he angle θ beween he uen elemen I dl and he veo om he uen elemen o he poin o p, and invesely popoional o he squae o he size o he veo: I dl sinθ d = (6) 2 The veo expession is as ollows: I d = (7) whee, is a popoional oeiien, is he pemeabiliy o vauum, and is value is 7 2 = N A. The suue o he ousing oil is shown in he Figue 5. The heigh, widh and lengh o ousing oil ae denoed as a b espeively.the uns o he ousing oil is n, he diamee o he oil wie is d, and he inpu uen is I. The oil is equivalen o a uniom annulus loop. The 2 equivalen uen densiy is J = 4 I / π d and he equivalen uen hikness is T 2 /4 = π nd n. The oil is divided ino ou pas alled A,, C and D. Eah pa o he uen is uniom. Taking C segmen o example, he magnei ield geneaed by he uen elemen a any poin is: J ( ) ( ) y j + z z k d = (8) J ( y) k ( z z) j = hen, J ( y) k ( z z) j = (9) V whee is volume inegal o pa C. The expession o he magnei ield geneaed by he ohe hee oils an be obained in he same way. Then he supeposiion piniple an be applied o obain he oal spaial magnei ield geneaed by he ousing oils: 4 = = i + j + k () i x y z i= Theeoe, he magnei ield geneaed by he ousing oil in hee dieions is: J y y D x = + D D D () z za x x A A J + A y = (2) z zc x xd + C C D D C D J ya y C z = A C A C A C () 2. Spaial Magnei Field Model O Taking Coil 684

Jounal o Theoeial and Applied Inomaion Tehnology h Apil 2. Vol. 5 No. 25-2 JATIT & LLS. All ighs eseved. ISSN: 992-8645 www.jai.og E-ISSN: 87-95 Fig.6 The Suue O Taking Coil The aking oil suue o he auao is shown in he Figue 6. Wih he same deiniion o he ousing oil, and is suual paamees ae onsideed as he heigh o he aking oil (inne ile), he widh, he lengh, and he equivalen hikness o he oil, whih ae denoed as: L W H n, espeively. Thee ae ou goups o aking oils, and eah se has n uns, wih a wie diamee is d. The inpu uen is I. Similaly, i an be assumed ha he espeive aking oils ae equivalen o a uniom dense ill eangula loop. The equivalen o he oil uen 2 densiy is J = 4 I / π d, and he equivalen hikness is T 2 = π nd /4H. Eah aking oil is divided ino ou pas, and he uens beween he adjaen oils ae opposie, as shown in he Figue 6: 4 = = i+ j+ k (4) nw x y z n= w epesens A,, C, D, espeively. The hee omponens o he aking oil magnei ield ae as ollows: J y z z = { [ ia i x ia i ia i i=, ia i yic z zid + ic ic + id ic id y z z + [ + ja j ja ja j j= 2,4 ja j y z z jd jd jd id ] jd J x xia x x ic y = { ia ic ia ic i, = ia ic x xja x x + } ja ja + j= 2,4 ja ]} j (6) (5) J x xi x x id z = { i id i id i, = i id (7) x xj x x jd + } j j + jd jd j= 2,4 j jd 2.4 The Spaial Toal Magnei Field Simila o he above analysis o eah pa, he oal magnei ield is also in line wih he piniple o supeposiion. The magnei ield a any poin Pxyz (,, ) in he auao spae is as ollows: ( P) = i + + σi m J i (8) = A da m + i m 4 Vi i π i m Ji + V i i i. THE SIMULATION RESULTS OF THE SPATIAL DISTRIUTION OF MAGNETIC FIELD ased on he analysis o spaial magnei ield model, he ull esuls o magnei ield disibuion an be obseved hough numeial simulaion. Thee ae a lo o sowaes ha an be used o alulae he eleomagnei ield. The Anso om Unied Saes based on he inie elemen analysis and Geman CST sowae based on he inie-dieene ime-domain (FDTD) mehod ae he popula sowaes. In his pape, he EM STDIO module o CST sowae is used o analyze he spaial eleomagnei ield o he auao.. Simulaion O The Pemanen Magne Field The spaial magnei ield o he auao is mainly podued by pemanen magnes. In he simulaion o he magnei ield o pemanen magnes, he maeial paamees o he geomei model, inluding elaive pemeabiliy, emnan lux densiy and he ai elaive pemeabiliy in he bounday ondiion, ae lised in Table. Maeial pemanen magne Table Paamees o pemanen magne elaive pemeabiliy ai. emnan lux densiy(t).6.4 Though alulaion, he magnei induion inensiy disibuion o he pemanen magnes in 685

Jounal o Theoeial and Applied Inomaion Tehnology h Apil 2. Vol. 5 No. 25-2 JATIT & LLS. All ighs eseved. ISSN: 992-8645 www.jai.og E-ISSN: 87-95 he ai is displayed in Fig 7and 8. Fig 7 is based on he inie-dieene ime-domain mehod, while Fig. 8 is based on he inie elemen analysis mehod. Fom he simulaion esuls, we an ge he a ha he magnei ield is symmeial abou he enoid bu non-uniom. Fig.7 Side view o he magnei induion inensiy o pemanen magnes Fig. Top view o induion inensiy o he ousing oil. Simulaion O The Taking Coil Magnei Field Taking oils o he auao ae divided ino ou goups. They ae disibued on he sides o ousing oil. The paamees needed ae he uen and uns ae shown in he Table. Table Paamees o aking oil uen (A) uns. 4*2 Fig. 8 Top view o induion inensiy o pemanen magnes.2 Simulaion O The Magnei Field O The Fousinging Coil Thee is only one goup o ousing oil in he wo-dimensional auao whih onols he movemen o he movable pas in he Y dieion. Using oil exiaion mehod in he CST sowae, he magnei ield disibuion o he ousing oil an be simulaed and alulaed. The equied simulaion paamees ae he uen and uns whih ae shown in he Table 2: Table 2 Paamees o ousing oil uen(a) uns. 56 The spaial magnei induion inensiy disibuion o he ousing oil is shown in Fig. 9 and. I is appaen ha he disibuion o he ousing oil is symmeial abou he enoid bu non-uniom, whih is simila o he disibuion o he aking oil. Moeove, he magnei induion is muh smalle han ha o he pemanen magne. Fig. Side view o magnei induion inensiy o he aking oil Fig.2 Top view o induion inensiy o he aking oil The spaial magnei induion inensiy disibuion o he aking oil is shown in Fig. and 2. The oal spaial disibuion o magnei ield o he auao an be obained hough simila analysis as shown in Fig. and 4. Fig. Synhesize oveall induion inensiy o he auao Fig. 9 Side view o he magnei induion inensiy o he ousing oil Fig.4 Side view o he oveall induion inensiy 686

Jounal o Theoeial and Applied Inomaion Tehnology h Apil 2. Vol. 5 No. 25-2 JATIT & LLS. All ighs eseved. ISSN: 992-8645 www.jai.og E-ISSN: 87-95 Though he simulaion, i an be onluded ha he magnei ield o he auao is symmei o he ene o he auao bu non-uniom. When he movable pas move in he non-uniom magnei ield, hey deviae om he ene posiion. The movable pa is no only auaed in he expeed dieion, bu also is oed in anohe dieion aused by he asymmei magnei ield, whih esul in a ossalk movemen. Fig.8 Change O The Magnei Induion O Taking Dieion Wih Widh Vaiaion O Pemanen Magne 4. INFLUENCE OF STRUCTURAL PARAMETER OF ACTUATOR ON THE MAGNETIC FIELD I has been shown ha magnei ield o auao is geneaed by he pemanen magne, ousing oil and aking oils. Some o hei suue paamees suh as he heigh o he pemanen magne and he widh and hikness o ousing oil ae he key paamees ha should be onsideed while designing he auao. In ode o veiy he ee o he above suue paamees on he ousing and aking moion, in he ollowing, wo segmens ha aoss he enoid and espeively paallel o he X axis and he Y axis ae seleed o analysis. The inensiy o magnei induion on he line is analyzed along wih he vaied suue paamees. The anges o movemen o he movable pas ae ±.5mm o he ousing dieion and ±.mm o he aking dieion. The magnei ield vaiaion is sudied wihin his ange o he wo segmens. Fig.5 Change O The Magnei Induion O Fousing Dieion Wih Heigh Vaiaion O Pemanen Magne Fig.6 Change O The Magnei Induion O Taking Dieion Wih Heigh Vaiaion O Pemanen Magne Fig.7 Change O The Magnei Induion O Fousing Dieion Wih Widh Vaiaion O Pemanen Magne Fig.9 Change O The Magnei Induion O Fousing Dieion Wih Widh Vaiaion O Fousing Coil Fig.2 Change O The Magnei Induion O Taking Dieion Wih Widh Vaiaion O Fousing Coil ased on he analysis esuls as shown in Fig 5 o 2, i an be onluded ha he magnei ield disibuion o he ousing dieion and he aking dieion will be moe uniom when he heigh o hikness o he pemanen magne is edued. Cossalk haaeisi in he auao will be hen weakened. Howeve, he hikness hange o he ousing oil has lile ee on he magnei ield disibuion boh on he ousing dieion o he aking dieion. Fo example, onsideing he minimum eleomagnei oe ha equied o dive he moveable pas o he auao, he magnei induion should, espeively, be geae han.55t in he ousing dieion and.7t in he aking dieion, hen he opimal suue paamees an be obained wih he heigh o he pemanen magnei a =4.5mm and he widh o he pemanen magnei b =.75mm. The inluene o he widh hange o he ous oil is lile. 5. CONCLUSION In his pape, he disibuion popeies o he auao spaial magnei ield is analyzed and simulaed by he CST sowae based on FDTD piniple. The essenial ause o he ossalk haaeisi in he auao is invesigaed. Though simulaion, he ends o he magnei induion vaiaion in he ousing and aking dieion wih he hange o auao suue paamees inluding he heigh, he hikness o he 687

Jounal o Theoeial and Applied Inomaion Tehnology h Apil 2. Vol. 5 No. 25-2 JATIT & LLS. All ighs eseved. ISSN: 992-8645 www.jai.og E-ISSN: 87-95 pemanen magne and hikness o he ousing oil ae obained, hus, based on whih he desied suue paamees o he auao ae opimized. Sine he ossalk haaeisi anno be eliminaed ompleely, an advaned onol mehod o he pikup auao is also expeed in ode o eliminae he ossalk haaeisi ompleely in he nex geneaion high-densiy opial soage sysems. ACKNOWLEDGMENT This wok was suppoed by he Naional Naual Siene Foundaion o China (575254), he Shanghai Pujiang Pogam (PJ44) and he Innovaion Pogam o Shanghai Muniipal Eduaion Commission (YZ6). REFRENCES: [] N. Pak, Y. Pak, K. Pak, H. Yang. Appliaion o Nex Geneaion Opial Daa Soage Tehnologies, IEEE Tansaions on Magnei, Vol. 47, No., 2, pp.59-545. [2] T. Shi, G. Wu, Reseah on he ous sevo sysem o DVD, China, Apil, 28, pp.5-2. [] S.S. Wang, Reseah on opi pikup adjusing mahine digial sevo sysem o DVD, China, Febuay, 26, pp.2-25. [4] H.D. Kwon, and Y.P. Pak, Dynami haaeisis o sepped anileve beams onneed wih a igid body, Jounal o Sound and Vibaion, 2, Vol. 255, No. 4, pp. 7-77. [5] H.H. William, A.. John. Engineeing eleomagneis, MGaw-Hill Siene, eijing, 24. [6] I.H. Choi, S.P. Hong, W.E. Chung e al. Conenaed Anisoopi Magneizaion o High Sensiiviy o Opial Pikup Auao, IEEE Tansaions on Magneis, Vol.5, 999, pp.86-864. [7].Q. Zhang, J.S. Ma, L.F Pan, J.G. Ru, Impovemen o high equeny dynami peomane o auao in opial pikup by inie elemen and sensiiviy mehods, Opis and Peision Engineeing, Vol. 5, No.7, 27, pp.2-8. 688