NGHIEN CU'U U'NG DyNG BO OI^U KHI^N MQ TRONG THII^T Bj SAY HAT NONG SAN ThS Trin Hdng Thao\ ThS Nguyin Birc Vinh\ PGS.TS Nguyin Van Liin* V/#/j Co dl^n Ndng nghidp vii Cdng nghe Sau thu hofich * Khoa Di$n - Tnrdmg D^i hge Bach khoa Ha Ngi T6m tit Cdc logi thiet bi sdy duac su dung bp diiu khiin di thvc hi?n qud trinh ldm khd ndng sdn din mpt dp am nhdt dirih theo yeu cdu Cdc phuang phdp diiu khiin qud trinh sdy truyin thdng cdn thi hien nhieu hgn che nhu chdt lupng sdn phdm khdng diu, tiiu tSn nhiiu ndng luang; cdc phuang phdp dieu khiin hi?n dgi, md cd diiu khiin m& to cd nhiiu lai thi khdc phye duac nhimg nhuac diim trin Tuy nhien, de dgt dugfc kit qud diiu khiin tot cdn cd cdc nghien cieu ky vi qud trinh say di qud trinh nhdn dgng md hinh diiu khiin duac chinh xdc Kit qud nghien cim md hinh dpng hpc qud trinh sdy, sie dting bp diiu khiin md ldm gidm dm hgt ndng sdn md nhiiu triin VQng cho cdng ngh? sdy de ndng cao chdt luang sdn phdm vd hi^u qud kinh ti linh viec bdo qudn chi biin ndng sdn, Ky hi$u: Wo - Dp dm han ddu ciia hgt, % Wch - Dp dm cdn bdng cita hgt, % W -Dp dm cuoi ciia hgt, % MR -Tyl4dpdm,% Qa - Luu lupng di qua hgt, m'/h RH -Dp dm tuang ddi cita khdng khi, % t - Th&i gian sdy, ph V - Vgn tpc ciia khdng sdy, m/s Ts - Nhi?t dp khdng sdy, "C Ta - Nhi?t dp khong mdi tru&ng, "C Tf - Nhi^t dp cudi ciia khdng khi, "C Cf, - Nhi?t dung rieng ctia hgt, J/kg "C I Giai THIEU Tronp qud trinh sdy hgt ndng sdn, nhiet dp tde nhdn sky, nhi^t dp Idm ndng khdi hgt, toe dp tde nhdn sdy, dp dm cfta hat vd thdi gian luu hgt bu6ng say dnh hudmg rat ldm din chdt lugng cua sdn phdm sau sdy Neu nhiet dp tde nhdn say cao ban nhi?t dp cho phep sdy thi d l gdy hi?n tugng nftt ngam hgt, chet mdm Nhiet tac nhdn say cdn phy thupe vdo dp dm ban ddu cfta hgt Nhi?t dp lam ndng khdi hgt budng sdy ty 1? nghjch vdi dp dm ban dau cua hgt, vi t h l che say vd thai gian say se phu thudc vdo dp am ban dau cfta moi logi hgt Qua trinh sdy hgt ndng sdn rat phftc tgp va khdng on dinh, d dd ddng thdi xdy cdc qud trinh truyin nhiet - dm ban thdn hgt vd giua hgt vdi mdi trudng, qud trinh truyin nhiet am tren thudng dugc md td bang he phuomg trinh vi phdn phftc tgp, vdy xdc dinh quy ludt thay doi ciia cac qua trinh bdng phuomg phdp tdch cdc thdnh phan cua he phuang trinh cdn phdi 131 gidi he phuang trinh vi phan phi tuyin vd khdng che mdt sd dilu kien dk gidi la nhiem vu kho khan De gidi quyet van dl nay, he thdng dilu khien say hgt ndng san [5] can phdi ddm bdo cac yeu cdu sau: - Duy tri yeu cdu chat lupmg san phdm sdy; khdng tinh den su nhieu loan van hanh mdy say vd cdc thay ddi qua trinh cdp lieu - Tang ndng suat thilt hi sdy, tdi uu chi phi nang lugng rieng va qud trinh sdy, gidm tdi da gid say - Ngan ngfta su qua khd va khdng dgt dp am sdy: Say khdng dgt dp am (dp khd) cd thl ddn din hu hdng hgt va luomg thuc; say qua khd sdn phdm dan den tang chi phi nang lugng va giam lgi nhuan, nd cung cd the gdy nen sir phd buy nhiet vdi cdc sdn pham mdn cdm nhiet dp - Qua trinh say dn dinh va ngan chan anh hudmg cfta cac bien nhieu loan ben ngodi - Lien quan den qua trinh dieu khien sdy, cdc bien sd ve nhiet do, ham lugng dm, tde dp ddng chdy, dp suat ket hgp vdi qua trinh say hgt ndng san theo me hodc say lien tuc cd thl phdn thdnh nhdm: Cac bd dieu khien may sdy me vd cdc bd dieu khien mdy sdy ddng hgt lien tuc [5,7] Theo phuang phap truyen thdng, cac bd dieu khien bao gdm: dieu khien thft cdng, dieu khien PID, dieu khien vugt trudc Ddi vdi cdc phuang phap chdt lupmg sdn phdm (hat) khdng deu va tieu tdn nhieu nang lugng Theo phuang phdp hien dai, cac bd dieu khien bao gdm: dieu khien thich nghi, dieu khien chuyen gia (Fuzzy) [2,7] Phuomg phdp khdc phuc dugc cdc nhugc diem cua phuang phap truyen thdng nhung ddi hdi phai cd cdc nghien cftu ky ban ve qud trinh sdy de cd the nhdn dugc md hinh dieu khien chinh xdc De xdy dung md hinh tin cdy (phftc tgp) cho dieu khien sdy ddi hdi sd lugng thi nghiem rat nhieu (yeu cdu ca thdi gian vd kinh phi), vdy ta chpn phuang phap dua vdo md hinh don gian ban de dieu khiin qud trinh va qua trinh suy ludn dugc thuc hien bdi bd dilu khiin md II PHU'aNG PHAP NGHIEN CU'U 2.1 Mo hinh dpng hoc qua trinh sly Xet quan he giua cdc dau vdo, vd nhieu qua trinh say nhu tren hinh 1, gdm: Ts(t)_ Tn,, RH Wo Cg i t t i W(t) Vgio Doi tu'ong say Hinh Cac ylu td anh huvng din qua trinh sly - Cdc biin ddu vdo cua mdy sdy gom: Nhiet dp tac nhdn sdy Ts; tde dp ddng tac nhan sdy Vgj6 ; tde dp cap lieu - Cdc biin ddu cua mdy sdy dien hinh nhdt Id: Hdm lugng dm cfta san phdm sau sdy W(t); nhiet cfta sdn phdm sau say Tc; nhiet cua thai; dm khdng thodt (khi thdi); chdt lugng sdn phdm (mau sde, mui vi, hogt tinh ) ^ - Ngodi cdn phdi ke din cdc nhiiu loan phd biin nhdt ciia mdy sdy la: Nhiet Tmt, dO dm RH khdng mdi trudmg xung quanh; ham lupmg dm cua hgt vdo Wo; nhiet dp hgt 132 Trong qud trinh sdy a tren cd mdt sd cdc biln khd xdc dinh nhu nhiet hgt, hdm lugng am cua hgt qud trinh sdy Md hinh ddng hpc cfta qua trinh sdy dugc xdy dung tft cdc phuang trinh ly thuyit cua Li vd Morey nhu sau [1,5,6,7]: W = W,,+(Wo-W,Je(-^'^) (1) O dd: K, N - Cdc he so thuc nghiem dugc xdc dinh theo nhiet tde nhdn say vd am hgt ban ddu ddi vdd mdt logi thilt bi say Md hinh tren da dugc tac gia [1] thuc nghiem sdy ngd vdi md hinh thilt bi sdy tdng sdi vdi cdc he sd: K = 0,04117 + 0,000001371 xTs^ - 0,001102xTsxWo (2) N = 0,505 - 0,0007622xWo^ + l,702xTs^ Do dm can bdng phu thudc vdo logi hgt, nhiet dp va dp dm cua mdi trudng xung quanh hgt, theo [1] tacd: ln(l-RH) W,b = (3) 5,786.10'.(r,+45,5) Trong dd: Dp dm tuomg doi cfta khdng RH, vung sdy gid thilt Id 80%) [1] 2.2 Mo hinh di§u khien qua trinh sly Tren ca sd phdn tich d tren vdi thilt bi sdy hgt ndng sdn nhiem vu cfta bdi todn tdng hgp bd dieu khien d ddy la thiet ke dieu khien qua trinh gidm dm bdm theo mdt qua trinh mau cho trudc, tiiy theo dp dm ban ddu cfta hat nd se dua dudng gidm am theo thdi gian khdc Dl cd thl bdm dugc dudmg am dd budc phdi dieu chinh nhiet dp tac nhdn sdy nam mdt gidi hgn cho phep de trdnh nftt va hgt Wn w Mau (i kk '—w-