Tuyen tap bao cao khoa hgc Hdi nghi Khoa hgc ky thuat Do ludng toan qudc ldn thii IV Hd Ngi, 11 - 2005 VE MOT THUAT TOAN DIEU KHIEN DONG LUC HOC LO NHIET THEO NGUYEN LY DIEU CHE DO RONG XUNG O N G DUNG KY THUAT VI XlJf LY Le Vinh Hd, Do Vdn Lap, Le Viet Hoan Vien Ten Ida Trung tdm KHKT - CN Qudn sif Tom tdt: Tren ca sd gidi bdi todn ddng life hgc Id nhiet de xud't thudt todn bdm nhiet theo nguyen ly diiu che'dd rdng xung ndng lifffng Xdy difng thugt todn dieu khien tren nguyen tdc difa td'c thay do'i nhiet theo thdi gian gidm ddn den Bdo cdo trinh hdy plufffng phdp thie't ke mot he thd'ng hdm nhiet sif dung ky thudt vi xif ly cdc sd lieu ddu nhit: i dug sud't P nhiet cdn ddt Ti, thdi gian gift nhiet ti cho cdc (hu trinh gia nhiet difgc ddt trifdc theo yen cdu cita mdi Idn hogt ddng Thie't hi co traug hi he lifu gill cdc sd'lieu nhiet sudi qud trinh cdng nghe - cdn duet cho viec qiichi ly cdng nghe cdn kiem tra He thd'ng bdm nhiet dugc thiet ke, che'tgo tren i a sd ly thuye't tren dd difgc sif dung cd hieu qua d mdt so ca sd vd ngodi qudn ddi Abstract: According to solving the problem of temperature dynamical i onirol, give a algorithm based on the method: the velocity of temperature changing is reduced gradually to zero The report presents the method to design a following hard on temperature system using microcontroler Input values as power, set temperature value, temperature keeping time for each cycle are set before working The system is equipped a storing temperature data device which is necessary for technological management The following hard on temperature system is designed and made based on that theory is used effecfivily inside and outside the army I M6 DAU Truydn nhifit la bdi toan phiic lap, vdy dd dieu khidn (bam) dugc nhifit dd chiing la cdn phai giai cac phuong trinh cdn bdng nhiet, phuong trinh truydn nhiet vdi didu kien bd hiiu han Tii dd chiing ta xdy dung thudt loan difiu khidn tren co sd cdc kfi't qua tim dugc II GIAI BAI TOAN DONG LUC HOC LO NHIET 2.L Phuong trinh can bdng nhiet Ndng Iugng cdn cd'p de tang nhifit toan bd Id nhifit kd td ldp each nhiet trd vao: Q,„,, = c,m,(T-To) • •(!) Trong dd: Qc6rch- Ndng lugng can cd'p dfi ndng nhifit cua Id't ca cdc phdn tir kd tfir Idp each nhifit trd vao (kd ca cac phdi, san ph^m), don vi la j (hoac kJ); c,- Nhifit dung rifing cua cdc ddi tugng dugc tdng nhifit (J/kg.°C); m,- Trgng Iugng ciia tdng phan tu (kg); 926 To- Nhifit dfi ban ddu ("C); T- Nhifit dfi cdn cd Dd'i vdi Id diing ndng lugng dien thi Q = P.t, Trong dd: P - Cdng sudt (W), t- Thdi gian cd'p dien (sec) Nang lugng tdn hao truydn nhifit, biic xa, dd'i luu qua loan bd bd mat tie'p xiic vdi mfii trudng cua Id nhifit dugc tfnh tdng qudt theo cfing Ihiic: T-T Q = P , H t = - ^ — ^ F t (2) —+— Vdi: Q,,,- Nang lugng tdn hao tdng hgp (J); T- Nhifit Id nhiet ("C); Tg- Nhifit mdi Irudng ("C); Si-Bi day Idp cdch nhiet thu" i (kfi ca vd Id) (m); Xi - He so ddn nhiet ciia W , , ' vdl lifiu each nhifit thii i (kfi ca vo Id) (——); aQ- He sd tdn hao tfing hgp biic xa - ddi m.°C W luu (———); F- Difin tich bfi mat tiep xiic vdi bfin ngoai cua Id nhifit (m"); l- Thdi gian (s) m C Phuong trinh cdn bdng nhifit cua Id nhifit vifi't tdng qudt nhu sau: Q = Qc6rch + Q,h = Pc6.-cht + P,,.t = P.l Vdi: Q- Tdng ndng lugng cdn cd'p (J); P- Tdng cdng sudt cdn cd'p (W), cu thd dd'i vdi Id nhiel Ihi: P.t = c m ( T - T^) + " F.t (3) —+— Trong dd: T-la tham so; TQ-nhiet mdi irudng, de don gian cho T^ = 2.2 Phuong trinh dgng hgc 16 nhiet diing nang lugng dien Tii phuong trinh cdn bang nhiet, xem nhiet T cong sud't tdn hao la iham sfi', ta cd thd vifi't phuong trinh dgng hgc cua Id nhifit theo each sau: - Cho sd gia cua thdi gian At - Xem cdng sud't cd'p P = PQ = const - Ddp ling dau vd nhifit Id AT, sau bie'n ddi, Iim I i m A / _ i O — ' = — chiing la Al dt dT dt + F Si (— -^ — ) c m At Ai ,^ cm(—+ At )> PQ , -T(p)a n.p cm s Po hay P(p) = cmp(p -1 a L-sJ' (4) aQ hoac dttdi dang toan ttt: F P-np)+ Po (5) ,Si ' cm(—.-l-—) It ao chung ta cd: T(p) = ^^0 Pip + a) (6) aQ Khi dd nghidm ciia qua trinh thay ddi nhidt cS'p cdng sua't cho Id nhidt se la: T(t) = ^ { l - e - " ) = T „ ( l - e - « ) 927 (7) Ky hidu K ^ a = J„ (°C) va hang sd thdi gian ciia Id x la 1/T = a (1/S) chung ta cd: r(/)=ro(l-e n (8) Qua trinh thay ddi nhidt Id nhiet dung nang lugng dien dugc bieu dien tren To V'^ I T„- T e *0 a < '^ ) Hinh Qua Irinh thay doi nhiet Id I Tfi'c dfi tang nhiet T ( t ) = T^.a-e '" (°C/s), P^= giai phuong trinh vi phdn vdi didu kien ddu t = 0, T = TQ (P = 0) chiing ta nhdn dugc su phu Ihudc vao nhifit dd Iheo thdi gian:7'_(0=7o.a.e ^ ("C/s), vi vdy Idc giam nhifit se la r_ ( = - ( ) a e ^ ("C/s) Nhu vdy 7" (/) = ( , tire la tdc dd tdng nhifit cd gia tri bdng gia tri tuyfit dd'i cua tdc dd giam nhifit; gid tri phu Ihudc vao chd'l lugng ldp cdch nhiet cua Id nhiel va tfch cm ciing nhu cdng sudi cd'p cho Id PQ III NGUYEN LY DIEU KHIEN NHIET BANG P H U O N G P H A P DIEU CHE DO RONG XUNG N A N G L U O N G Nhu tren da Irinh bay, td'c tdng nhifit cua Id phu Ihudc vao hang sd thdi gian cua Id nhifit (lugng l6n hao, khdi lugng cdn ldm ndng, cdc tham sd vdl ly cua cac vdt lifiu lam ndng) va cong sudt cdp cho Id nhiet TCr phuong trinh (8) vdi Tg = ^0 • ^3 - Po '^ "^^^ cQn% sudt 100%, t/T la ty Ifi xd'p q ciia xung ndng lUcmg Khi Po(l) = Pg.t/T; dd l la dd rdng xung ndng lugng, cd thd suy cdng sud't trung binh cd dang xung don vi vdi bifin dd thay ddi theo tfn hieu difiu khidn Dang boan loan phu hop vdi dang cdng sud't PQ ma chting la da lim dugc nghiem: T{t)= ro(I - e~^^) Bdi loan dai la hay xac dinh P ( t ) = P „ t / T nhifit Id dat T^ (nhifit ddl-yfiu cdu) dd sai sd nhiet bdng ( d T / d t = ) Dfi ldm viec chiing la xem P(I) Id ham cua Ihdi gian vd dd cdng thiic tfnh T(t) cd dang: T[P(t),t]=^P(t)[l- ^ ] dd sai sd nhiet t=to; T(t)=T(t|,) chiing ta ld'y a dao ham T(i) theo P(t) va t: — = — + — = ^ a a? at P' ( t ) ( l - e""") + ^ a Pfti.CE.e""' a De dieu khien bam nhiet thi t « r , ta cd T[P(t), t] =Ko.P'(t) + Ko.P(t)(l-Oft) SaisdbambkngOthiT(t) = Giai phttong tnnh T'(t) = vdi cac dieu kien dau t=t„, P=Po va T=T(t„) ta ti'nh dttgc dd rdng xung nang Ittgng t theo cdng thttc sau: ^_a.t.e~'-(l + ôt) ^gã^ KwT.id-e-"'") dd K,^ la hfi sd ldn hao ciia Id nbifil - Nguyen tdc dieu che'dd rdng xung dung dieu khien nhiet bdng ky thugt sd + Dai lugng vao: Siic difin ddng tii can nhiet Mach didu khidn dung ddu bdng can nhiet cdn phai cd bifin phdp ky thudt loai trii anh hudng ciia su thay ddi nhifit mdi Irudng Qua trinh bam phai lao dugc ludt didu khidn dam bao cho cac qud trinh md ciia cdc van Thyristor bang cdc gdc md a theo su sai Ifich nhiet do, ludt bam id ludt PI, gdc md « „ = f ( A T ) Bidu dd difin dp cap cho ddy ddt dugc bidu didn trfin hlnh (ve cho pha) U.^^ Hinh Bieu dd dien dp cap cho ddy ddt Vdi hfi bdm dung ky thudt sd (vi xu ly): tao gdc md ciia cac van ddng luc theo sai a^ = 11.7^.6)^^ = f ( N - N ^ ) (10) sd nhifit dd, lao dugc su phu thugc: Trong dd: a„- gdc cdn cd ma d dd Thyristor khdng dugc md (dugc tao bang chuong trinh); n- sd IU nhifin phu thudc vao su sai Ifich nhifit dfi, n->co ihl tuong duong qud trinh bdm tuong tu; T(j- chu ky ddng hd nhip cua bd xii Iy; N - dai lugng dugc (bdng sd"); NQ- dai lugng cdn cd (bdng sd); 0)5(1- tdn sd gdc difin dp ludi 50Hz (314rad/s) IV X A Y D U N G T H U A T TOAN DIEU KHIEN TREN NGUYEN TAC DUA TOC D T H A Y D O I N H I E T GIAM THEO THCil GIAN DAN DEN Ddi vdi cdc Id nhifit diing nang luong difin dii cap nhiet true tifi'p hay gidn tifip ddu cd qud trinh trugt nhifit dd Miic dd trugt tiiy thudc vao: ke't cd'u cua Id, tinh chat co ly ciia cac vdt lifiu mdi trudng truydn nhiet (kd ca Id, cac vdt cdn lam ndng ), dai nhiet cdn dat dugc, cdng sud't cua Id Do vdy qua trinh bam nhifit, ngoai phdn cd'p nhiet dd cdn bdng vdi qud trinh tdn hao ta cdn phai luu y de'n trugt nhifit ciia timg dang id Thudt loan didu khidn nhifit tridn khai iing dung bd vi xir Iy dugc md ta d dang gia ma nhu sau: Dgc dit lifiu nhifit dd ban ddu (TQ) va nhiet can dat tdi (Tj), tfnh AT = T^ - To; nfi'u AT= thi ta khdng cd'p nang lugng niia, ndu AT>0 thi tiiy theo timg bai todn cu thd md ta cap nhiet dfi'n mdt didm diing vd sau dd chd tfnh trugt cua nhifit, td'c dd trugt nhiet sau dd di vao qud trinh bam; nfi'u AT