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Nâng Cao Chất Lượng Điều Khiển Hệ Thống Cán Tấm
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S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.edu.vn I HC THI NGUYN TRNG I HC K THUT CNG NGHIP --------------------------------------- LUN VN THC S K THUT NGNH : T NG HA NNG CAO CHT LNG IU KHIN H THNG CN THP TM BAN GIM HIU KHOA SAU I HC NGI HD KHOA HC PGS T.S NGUYN NH HIN HC VIN C TUN
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.edu.vn Thi Nguyn, 2011 LI CAM OAN Ti xin cam oan y l cng trnh nghin cu v tng hp cc ti liu ca ring ti, cc s liu, kt qu nu trong lun vn ny l trung thc v cha tng c ai cng b trong bt k cng trnh no khc. Hc vin c Tun
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.edu.vn LI CM N Nc ta ang phn u n nm 2020 c bn tr thnh mt nc cng nghip c trnh pht trin kh. Chin lc trong nhng nm ti l phi a t nc pht trin nhanh v bn vng, xy dng nn kinh t t ch, ch ng hi nhp c hiu qu vi kinh t quc t v tip tc i mi su rng hn na. Ngnh thp l mt ngnh cng nghip then cht trong nn kinh t quc dn, l u vo cho rt nhiu cc ngnh cng nghip khc. Thp c nh gi l vt t chin lc v c vai tr ht sc quan trng trong s nghip CNH-HH t nc. Sn phm thp rt a dng trong phi k n thp tm (l) l mt trong nhng dng sn phm cn kinh t nht. T thp tm v thp bng ngi ta sn xut thp ng, thp hnh un, cc loi kt cu hn v cc sn phm dp rt a dng. nc ta, trong nh hng pht trin ca nghnh luyn kim d kin tng nhu cu thp vo nm 2010 l 6.400.000 tn, trong c 3.500.000 tn thp l v 2.900.000 tn thp hnh v dy. Nh vy khi lng thp tm, l chim gn 55% tng sn phm thp cn. Hin ti nc ta ch c duy nht nh my cn thp tm l cng ty TNHH mt thnh vin Thp Ci Ln ang hot ng. H thng cn thp tm c nghin cu v s dng rng ri ti cc c s nghin cu v thc nghim nhng hu ht cc cng trnh ny u khng xt n nh hng phi tuyn ca h thng thy lc do vy cc m hnh ny tng i n gin v phm vi ng dng hp. Mt vn quan trng trong iu khin qu trnh cn l cn ci thin thi k qu . Xut pht t l do trn, tc gi la chn ti Nng cao cht lng iu khin h thng cn thp tm.
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.edu.vn Do mt phn khi kin thc dung nghin cu , gii quyt nhng vn ln trong tai thuc linh vc Cng ngh cn thp tm , tc gi phi t hc trong mt thi gian ngn , ti liu tham kho phc v cho lun vn gp nhiu kh khn, thi gian nghin cu lun vn va kha nng t ngh in cu cua tac gia con hn ch, nn khng th trnh khi nhng thiu st. Rt mong s quan tm, gp ca cc Thy, C v ng nghip tac gia linh hi b sung cho chng trnh nghin cu, nng cao trinh cua ban thn ngay mt tt hn. lun vn hon thnh ng thi hn, cng vi s n lc ca bn thn, tc gi nhn c rt nhiu s gip ; trc tin tc gi xin chn thnh cm n PGS T.S Nguyn Nh Hin, thy hng dn khoa hc chnh gip tc gi hon thnh lun vn ny. Ngoi ra, tc gi cng xin chn thnh cm n thy Bi Chnh Minh cng cc thy (c) trong khoa in, cc bn b, ng nghip gip , chia s kinh nghim gip tc gi hon thnh lun vn ny ./. Thi Nguyn, thng 9 nm 2011 Hc vin c Tun
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
10
10
Ch-ng 1. Gii thiu cng ngh cn thp tm
Chng 1
GII THIU CNG NGH CN THP TM
Thp tm hay cn gi l thp l l mt trong nhng dng sn phm cn kinh
t nht. T thp tm v thp bng ngi ta sn xut thp ng, thp hnh un, cc
loi kt cu hn v cc sn phm dp rt a dng. Ch to cc dng ng v thp
hnh nh t thp tm v thp bng (c dy nh hn so vi sn phm ng v thp
hnh cn) cho php tit kim c 10- 15% kim loi.
mt s nc cng nghip pht trin, t trng thp tm v thp bng trong
tng khi lng sn phm cn chim ti 50- 70%. Cng vi s gia tng nhu cu v
thp bng v thp tm ni chung, khi lng sn phm thp l cng khng ngng
tng nhanh, chim t trng trn 40% tng sn phm v thp bng.
nc ta, trong nh hng pht trin ca ngnh luyn kim d kin tng
nhu cu thp vo nm 2010 l 6.400.000 tn, trong c 3.500.000 tn thp l v
2.900.000 tn thp hnh v dy. Nh vy khi lng thp tm, l chim gn 55%
tng sn phm thp cn.
m bo nhu cu nu trn, d kin xy dng, phn b v pht trin nng
lc thit b nhm cn i nhu cu sn phm cng c xut cho tng giai on
n 2005 v 2010, bao gm cc nh my cn nng, cn ngui thp bng lin tc vi
tng sn lng d kin n 2010 ti hn 4 triu tn/ nm [1].
1.1. PHI CHO SN XUT THP TM V THP BNG CN NNG
sn xut thp tm ngi ta s dng phi l slab v thp thi. Slab l phi
c t l gia chiu rng v chiu dy khong 312. Kich thc ph bin ca slab,
dng cho cc my cn hin i l: HBL = (100 300) mm (600 320)mm
(1500 14000 mm, khi lng t (35 45) T.
Theo phng php sn xut, slab chia lm hai loi: slab c v slab cn.
Slab cn c cn t thi cc my bluming, luming-slabing v slabing. Khi
cn slab cc my bluming, luming-slabing ngi ta p dng nhng ln cn bin.
Do vy, b rng ln nht ca slab b hn ch bi khong cch nng trc cc i.
Cc my bluming c th sn xut slab vi chiu rng ln nht (800100) mm, cn
cc my blumming-slabing -(1600 1900)mm [1].
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
11
11
Ch-ng 1. Gii thiu cng ngh cn thp tm
Slabing l loi my cn ch yu dng sn xut slab cn. Slab cn cc
my ny m bo c hnh dng, kch thc v cht lng gia cng. Khong cch
gia hai trc ng v gia hai trc ln cho php cn slab c b rng n 2240 mm.
Qu trnh cn cc my slabing c tin hnh vi s ln o chiu v s ln cn t
nht. Cho nn nng sut ca cc my cn slabing ln hn nhiu so vi cc my cn
slab khc.
Sn xut slab t thi bng phng php cn c nhiu im hn ch:
- H s tiu hao kim loi ln.
- Qui trnh cng ngh phc tp, tn thi gian v nng lng.
- Slab c s khng ng nht v c tnh do s khng ng nht v thnh phn ha
hc v t chc ca thi gy nn.
Sn xut slab bng phng php c lin tc khc phc c hu ht nhng
nhc im k trn. Do c s ng nht v thnh phn ha hc v t chc nn cht
lng ca slab c cao hn slab cn. Ngoi ra, phng php c lin tc cn cho
php gim mt cch ng k hiu s tiu hao kim loi, nng lng v thi gian cho
qui trnh cng ngh. Chnh v vy m gi thnh ca slab c thp hn nhiu so vi
slab cn.
Do c nhng u im kinh t - k thut nu trn, hin nay phng php c
lin tc slab c p dng mt cch rng ri v tr thnh phng php sn xut
phi ch yu cho cc my cn thp tm.
Cn thp tm t phi slab l phng php cng ngh hp l hn c. Bng
phng php ny, ta c th nng cao c tnh, cht lng b mt ca thp thnh
phm, ng thi gim ng k h s tiu hao kim loi, tng nng sut v m rng
rng chng loi sn phm ca my.
Kch thc v khi lng ca slab c xc nh cn c vo kch thc ca
sn phm.
i vi cc my cn tm, nhng phi slab c chiu dy nh nht v chiu
rng (hoc chiu di) bng chiu rng ca tm thnh phm l nhng phi c kch
thc ti u. Cc phi ny cho php gim ti a s ln cn v bng cch nng
cao nng sut ca my. Chiu di ca phi thng b hn ch bi chiu di thn trc
cn, bi l cc phi c chiu di vt qu chiu di thn trc, ta khng th p dng
s cn ngang to b rng cho thp thnh phm. cc my cn tm ln, khi
lng ca slab c th ln ti 40T hoc hn.
Khi cn cc my cn thp bng rng bn lin tc v bn lin tc, ngi ta
da vo kh nng p ca cc gi cn, kch thc l nung phi, c im v tnh
nng ca cc thit b ph tnh ton kch thc slab.
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
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12
Ch-ng 1. Gii thiu cng ngh cn thp tm
Khi chn kch thc ti u cho slab, ta cng cn ch n kh nng v tnh
hp l ca vic sn xut chng cc my cn phi hay cc thit b c lin tc.
1.2. C IM, THNH PHN V CCH B TR THIT B CC NH
MY CN TM
Chiu di thn trc cn ca cc my cn tm c xc nh theo chiu rng
ca thp thnh phm. Chiu rng ln nht ca tm sau khi cn phi nh hn chiu
di thn trc t 200 mm n 400mm.
Cc my cn tm gm mt hoc hai gi phn b ni tip nhau. S lng gi
cn c xc nh cn c vo nng sut cn thit v yu cu v cht lng ca thp
thnh phm. Vi nng sut (300.000 500.000) T/nm, ngi ta thng t my
cn mt gi. My hai gi cn cn trong trng hp yu cu nng sut cao hn.
Cc gi cn ca my cn tm thng l kiu 2 trc (duo) o chiu, 4 trc
(kvarto) hoc 4 trc vn nng ( 4 trc ngang kt hp vi 2 trc ng). Kiu gi 3
trc, vi trc gia nh hn khng truyn ng (trio Lau ta).
Cc gi cn duo v trio lauta c cng thp, thng gy nn khng
ng u ngang v dc ng k ca chiu dy thp cn. i vi cc gi cn trio
lauta, cn cn phi c bn nng h b tr hai bn gi cn, h thng ny thng rt
nng n, mt mt lm hn ch khi lng v kch thc thp cn, mt khc v tc
quay ca trc cn khng i sut trong qu trnh cn mt sn phm, nn ti trng
ng khi trc cn n thp rt ln. Ngoi ra cc gi cn trio lauta lng thp trong
mt ln cn thng b hn ch v thi gian ngh gia hai ln cn tng i di.
Chnh v nhng nhc im trn m hin nay, khi xy dng cc xng cn tm
mi, kiu gi cn trio lauta khng c dng na, cn cc gi cn duo ch c s
dng lm gi cn th cc my cn tm hai gi.
Kiu gi kvarto c s dng rng ri hn c. So vi cc kiu gi cn khc
(t trc hn), cc gi c kavarto c cng cao hn, do m bo c chnh
xc ca chiu dy thp thnh phm.
cn thp tm c mt bin c gia cng, ngi ta s dng cc gi cn
kvarto vn nng. Cc gi ny thng c dng lm cc gi cn tinh cc nh my
cn tm, bng dy v hp. Tuy nhin hiu sut s dng cc gi cn vn nng cc
my cn tm dy khng cao, bi v khi cn tm rng v tng i mng, khng th
p dng lng p bin trnh cho thp b un cong theo chiu ngang.
Mt s t nh my luyn kim c hin nay trn th gii vn cn s dng my
cn tm mt gi triolauta. Cc nh my ny thng c chiu di thn trc 1800
3850 mm, ng knh trc trn v di 650 1000 mm, ng knh trc gia 450
780 mm. Hai trc trn v di c truyn ng t ng c in xoay chiu, qua
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
13
13
Ch-ng 1. Gii thiu cng ngh cn thp tm
hp gim tc v bnh . Cc my ny thng cn tm dy 4 32 mm vi tc
2,5 3,5 m/s.
Cc my cn tm triolauta mt gi hin nay khng c ch to na.
cc my cn tm mt gi, ngoi gi kvarto, ngi ta thng t thm mt
trc ng, c nhim v nh g, gia cng mt bin v cn chiu rng. Trn hnh 1.1
trnh by s b tr thit b ca my cn tm mt gia kvardo 1050/2150 4300
(cng ha lin bang c). My cn tm c chiu dy n 40 mm, chiu rng n
4160 mm, t phi slab c khi lng n 40T. Phi trc khi cn c nung trong
l lin tc vi cng sut 206T/h. Nng sut ca my t ( 900 000 1000 000)
T/nm.
Mi trc lm vic c truyn ng t ng c ring, cng sut 3725KW.
Vn tc cn t 6m/s. Gi cn c kh nng chu ti n 8850 T.
My c trang b h thng t ng iu chnh chiu dy v c cu chng
un trc ta, cho php cn sn phm vi tc chnh xc v phng cao. Lc
chng un mi u trc t ti 1470 T.
Hnh 1.1. S b tr thit b ca my cn tm 1 gi o chiu kvarto 4300[1]
1- bn cn phi;2- l nung lin tc;3- gi cn o chiu kvarto; 4- my nn nng;
5- my ct la; 6- gin lm ngui; 7- gi kim tra v nghim thu sn phm (c
trang b my lt tm); 8- my ct u, ui; 9- my ct dc;10- my ct mp bin;
11- l thng ha; 12- my ct ngang; 13- my nn ngui
Trc gi cn ngi ta t thit b nh g thy lc, p sut nc t ti 170
at. Sau gi cn l my cn nng, c th nn thng thp tm c chiu dy n 95 mm.
My cn cng c trang b cc my ct u, ui, ct phn on v ct mp
bin, my nn ngui v cc l thng ha c chiu di 75m, rng 4,5m, cho php
nung thp tm c chiu di n 30m, rng n 4,1m vi nhit 500 11000C.
Do nhu cu a dng ha chng loi sn phm thp tm t cc mc thp
cacbon v thp hp kim, cng vi nhng yu cu ngy cng cao v cht lng b
mt v chnh xc ca sn phm, cc my cn tm lin hp duo kvarto v cc my
cn c khung gi di ng c s dng mt cch rng ri.
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
14
14
Ch-ng 1. Gii thiu cng ngh cn thp tm
My lin hp c cu to gm mt gi kvarto v mt b 2 trc cn (duo), c
chiu di thn trc nh hn chiu di thn trc gi cn kvarto, c g t nh mt
h thng dm ngang c bit. Do , my lin hp c th thay th phn no vai tr
ca hai gi cn: slabing v gi cn tm kvarto, cho php sn xut thp tm c cht
lng cao t thi.
Mt trong cc my cn lin hp ln nht th gii c xy dng Nht Bn,
b duo ( kch thc trc 1230 3000 mm) lm vic nh mt my slabing, c th cn
thi khi lng n 25T v slab kch thc H B = (100 400) mm (1200
1800) mm. B kvarto c kch thc trc 1020/1800 4300 mm, cho php cn tm
sn phm c chiu dy 6 150 mm, chiu rng 1200 4000 mm v chiu di n
20m. Gi cn lin hp c truyn ng t hai ng c vi cng sut mi chic
3680kW.
cc my cn tm c trang b cc gi cn c khung di ng, qu trnh cn
cc chng loi thp tm hp v rng c tin hnh vi cc trc c chiu di khc
nhau. iu cho php cn cc sn phm c dung sai chiu dy thp (gim nh
hng ca un trc do khng phi cn thp tm hp vi trc cn qu di). Khi
chng loi chiu rng thay i, mt trong hai khung gi c th dch chuyn n hai
v tr khc nhau nh cc xilanh thy lc. Khung gi c bt cht vo my bng
cc mc thy lc.
Mt trong nhng gi cn kvarto o chiu c khung di ng ln nht c
xy dng M. Chiu di thn trc gi cn ny c th thay i trong khong 4065
5335 mm, ng knh trc ta 1800 mm, ng knh trc lm vic 1000mm. Mi
trc lm vic c truyn ng t mt ng c ring vi cng sut 4470kW. My
cho php cn tm t cc mc thp cacbon v thp hp kim, kch thc hbl = (4,7
380)mm (760 5080)mm (29000)mm.
Cc my cn tm lin hp duo - kvarto v cc my cn c khung gi di ng
ch c hiu sut s dng cao trong trng hp cn sn phm c khi lng sn xut
nh v chng loi rng.
sn xut thp tm, cc my cn hai gi vn c s dng rng ri hn c.
Thnh phn ca cc my cn tm hai gi hin i thng gm mt gi trc ng v
hai gi trc ngang (cn th v cn tinh) b tr ni tip nhau. Cc my cn hai gi c
u im l cht lng b mt sn phm cao (do thp c nh sch g gi trc
ng v gi cn th trc khi cn trong gi cn tinh), thi gian lm vic ca trc
cn di (gim s ln thay trc), nng sut cao.
Cc my cn tm hai gi hin i c s phi hp gia cc gi cn nh sau:
- Gi cn th duo v gi cn tinh kvarto;
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
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15
Ch-ng 1. Gii thiu cng ngh cn thp tm
- Gi cn th kvarto v gi cn tinh kvarto.
Trn hnh 1.2 trnh by s b tr thit b ca my cn tm hai gi 2800.
My gm mt gi trc ng, mt gi cn th duo v mt gi cn tinh vn nng
kvarto. Sn phm ca my c kch thc hbl = (8 50)mm( 2500)mm (20
000)mm, c cn t slab kch thc HBL = ( 125250) mm ( 700 1600)mm
( 2500 6000)mm, khi lng n 12T. Nng sut ca my t 1000 000
T/nm[1].
Hnh 1.2. S b tr thit b ca my cn tm 2 gi 2800
1- my y phi;2- l nung lin tc; 3- gi cn trc ng;4- gi cn th o chiu
duo 1150x2800; 5- gi cn tinh o chiu kvarto 800/1400x2800; 6- ng bng
ln lm ngui; 7- my nn;8- sn lm ngui; 9- b phn cha thp tm lm ngui
chm; 10- my lt tm; 11- xe ly du kch thc; 12- my ct chm dng ct
ngang v ct dc; 13- my ct a ct mp bin; 14- my ct chm c min hot
ng rng; 15- b phn cha thp tm; 16- l nung c sn con ln dng nhit luyn
thp tm; 17- xe vn chuyn thp;18-ng bng ln c my o in t; 19- h
cha vy g; 20- cu trc.
Gi trc ng c ng knh trc 1500mm, chiu di thn trc 600mm.
Cng sut ng c truyn ng cho gi trc ng 880 kW. Pha trc gi ny c
my o phi, pha sau l h thng nh g thy lc gm hai ng dn vi cc vi
phun nc p sut cao (n 100at), phn b pha trn v pha di tm thp.
Trc ca gi cn th duo c kch thc DL = 1150mm 2800mm. Mi trc
cn c ng c truyn ng ring, cng sut 2570kW, tc 0 -3-60 vng/pht.
Gi cn cng c trang b h thng nh g thy lc. Pha trc v sau gi cn c
gin con ln cn xoay thp mt gc 900 trong mt phng ngang v hai my cn dn
thp vo trc.
Trc ng ca gi cn tinh vn nng kvarto c kch thc DL=
700400mm. Mi trc c ng c truyn ng ring, cng sut 200kW. Trc lm
vic v trc ta c ng knh tng ng 800mm v 1400mm, chiu di thn trc
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
16
16
Ch-ng 1. Gii thiu cng ngh cn thp tm
2800mm. Hai trc lm vic c truyn ng t ng c in mt chiu, cng sut
5500kW, tc 0-60-120 vng/pht. Pha trc v pha sau gi cn c cc my cn
dn thp vo trc.
Nhng my cn tm ang lm vic v c thit k mi hin nay thng c
chiu di thn trc khng di 3000 mm. Mt s my cn tm ln c chiu di thn
trc ti 5590mm hoc hn.
Ph thuc vo chiu di thn trc, trc lm vic thng c ng knh (800
1130)mm, ng knh trc ta ( 1400 2300)mm.
nung phi slab v phi thi, ngi ta s dng kiu l nung lin tc hoc
l ging (cho cc thi ln).
Cc h thng cn tm hin nay u c trang b cc h thng t ng iu
khin, cho php cn sn phm c chnh xc v phng cao. Nhiu nh my cn
tm c t ng ha hon ton t khu nung phi cho n khi ra thp thnh phm.
1.3. K THUT CN THP CC NH MY CN TM
Hnh 1.3 trnh by s qu trnh cng ngh sn xut thp tm t cc mc
thp cacbon (a), thp khng g (b)v thp hp kim (c).
Sau khi kim tra v lm sch khuyt tt b mt (thi bng ngn la p sut
cao) phi slab v thi c nung trong cc l lin tc hoc l ging n nhit
1150- 1250C, khi t nhit cn thit, tng phi cn c a n my cn theo
ng bng ln.
Ph thuc vo thnh phn thit b ca my, ngi ta cn phi thnh tm
trong mt hay vi gi cn. V cc gi cn lm vic o chiu nn s ln cn bao gi
cng l s l, cc gi cn mt gi s ln cn th v cn tinh u tin hnh trong
mt gi. cc my cn hai gi, qu trnh cn c tin hnh theo th t sau: Phi
(slab) u tin c cn trong gi trc ng. Ti y, sau mt ln cn, phi c p
theo chiu ngang ( 10 50)mm. Tip theo phi c chuyn sang gi cn th v cn
y cho n khi t c dy v chiu rng cho trc. S ln cn trong gi cn
th thng t 5 n 11 ln. Sau ln cn th 2 v th 4 gi cn th, thp mt ln
na c a tr li trc ng cn bng cnh bin v cn chiu rng. Tip theo
gi cn th, thp c cn trong gi cn tinh cho n khi t dy cn thit sau
(59) ln cn.
cc my cn tm hai gi, ngi ta thng cn ng thi 2 phi- mt gi
cn th v mt gi cn tinh. m bo s ng b trong qu trnh lm vic, chu
trnh cn gi cn th v gi cn tinh phi xp x bng nhau.
c im ca qu trnh cn trong gi trc ng, gi cn th v gi cn tinh
c trnh by hnh 1.3a,b.
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
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17
Ch-ng 1. Gii thiu cng ngh cn thp tm
Thp cc bon v thp hp kim thp
Phi slab hoc thi
Lm sch khuyt tt b mt
Nung
Cn gi nhit n nhit nh
trc
Cn
Nn thng nng
Ct v ly mu kim tra
ng nhn v du
Nhit luyn
Nn thng ngui
Kim tra, lm sch
Xut xng
Thp khng g
Phi slab
Lm sch khuyt tt b mt
Nung
Nn thng bimetal
nhit 3006000C
Cn
ng du
Nhit luyn
Nn thng trng
thi ngui v ct
Ty sch b mt v
phn loi sn phm
Xut xng
Nn thng thp khng g khng gim nhit
Hnh 1.3a
S ha bi Trung tm Hc liu i hc Thi Nguyn http://www.lrc-tnu.
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18
Ch-ng 1. Gii thiu cng ngh cn thp tm
Cn thnh tm
Nn thng
Ct trng thi nng
Thp hp kim
Phi thi (600- 900C)
90
Nhit luyn
Lm sch b mt
Nung
Phi slab
Lm sch b mt
Nung
Nung
Cn thnh slab
Ct v ng du
ng du
Nhit luyn
Nn thng trng thi ngui
Kim tra, ty sch b mt v phn loi tm
Xut xng
Ti ram
Lm ngui n 200C
Lm ngui n 200C
Nhit luyn
Slab
Cn
Hnh 1.3b
1.3.1. Cn phi slab trong gi trc ng
Trong gi trc ng, phi slab c p theo chiu ngang nhm nh bng g
to ra trong qu trnh nung (g l) v san bng khng ng u ban u ca chiu
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19
19
Ch-ng 1. Gii thiu cng ngh cn thp tm
bv/2
h0 hph
bph bph
b1
b0
ltv
rng phi. G l sau khi b b gy c hc, c nh bng bng nc phun di p
sut (100200)at.
Cht lng nh g ph thuc vo thm thu ca bin dng trn tit din
ngang ca phi. Nu vng gia phi trong qu trnh cn khng bin dng do, th g
ch c nh bng vng hai mp bin, tc l vng c s gin rng bph (hnh 1.4).
Hnh 1.4. S bin dng ca phi slab trong gi cn trc ng
Chiu rng ln nht ca phi slab, m bo cho bin dng do thm thu
ton b tit din ngang, c th xc nh t iu kin sau:
btb=4,5ltv + 4h0 (1.1)
Trong : btb = 0,5(b0 + b1) - chiu rng trung bnh ca phi;
vbRtvl . - chiu di vng bin dng ( bv = b0-b1 lng p
trong gi trc ng).
Biu thc (1.1) cho thy, nu btb > 4,5ltv + 4h0, vng gia phi s khng
bin dng, hiu sut nh g ca gi trc ng s km. Tr s ca bph c th tnh
theo cng thc thc nghim:
tv
ph
l
h
h
b0
0
33,09,12
(1.2)
Trong h0 l chiu di ban u (mm)
ng knh trc cho php t hiu sut nh g cao nht :
R
hbvb
tb
2,20
2)4(0
(1.3)
Trong thc t, cht lng nh g ch m bo khi lng p ln hn so vi
lng p c tnh theo (1.3). i a s cc trng hp, khi cn phi c b ngang
tng i hp, nh sch g l, lng p ring tuyt i trong gi trc ng phi
t (5060)mm. Tuy nhin, do cng sut ng c truyn ng v ng knh trc
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20
20
Ch-ng 1. Gii thiu cng ngh cn thp tm
tng i nh nn vic tin hnh mt lng p ring ln, nh vy nhiu my
khng th thc hin c.
nng cao hiu sut nh g cc gi trc ng, ngi ta tng ng
knh trc ln ti (12001300)mm.
Vic p dng trc ng c khun hnh cng l bin php hiu qu tng cht
lng nh g. Khi cn trong trc ng c khun hnh, lng gin rng ca thp
vng tip gip vi trc b hn ch, cn lng bin dng gin di v thm thu
bin dng li tng ln ng k, lm cho g l c nh bng ton din hn.
Sau khi nh sch g l, thp c chuyn sang gi cn th. Tip theo gi
trc ng ch dng san bng mt bin v cn chiu rng cho thp gia nhng ln
cn th nht nh.
1.3.2. Cn trong gi cn th
gi cn th cc my cn tm hai gi, lng p tng t ti (7080)% tng
lng p theo chiu dy phi.
Ph thuc vo kt cu ca my cn, t s gia chiu rng ca tm sau khi
cn v chiu rng ca phi, yu cu v cht lng ca thp thnh phm, ta c th p
dng nhiu s cn khc nhau. Khi xt tng s , cn thng nht qui nh sau:
qu trnh cn dc theo trc ca thi hoc slab gi l cn dc (CD), cn vung gc
vi trc ca thi hoc ca slab gi l cn ngang(CN).
Nu phi l thi th qu trnh cn thng gm cc bc theo trnh t sau:
Cn mt cn (vt) v cc g sng ca thi theo s CD, qua 3- 4 ln
cn.
Cn ph b rng theo s CN vi s ln cn theo ch p nh. Bc
ny rt cn thit v chiu rng ca tm thp sau khi cn ln hn nhiu so vi b
rng ca thi. Cn ph b rng tin hnh sau khi xoay phi 900 trong mt phng
ngang.
Cn ph chiu dy v chiu di tin hnh theo s CD theo ch p nh
trc, sau khi xoay thp tr li 900.
Trong trng hp cn t phi slab, ta c th p dng cc s sau:
Nu chiu rng phi bp bng hoc ln hn chiu rng ca tm cha ct mp
bt qu trnh cn tin hnh theo s CD cho n khi t c dy cn thit.
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21
21
Ch-ng 1. Gii thiu cng ngh cn thp tm
bpbt
btbp
lp
bp
bp
bt
btbt
I IIIII
III
a)
b)
c)
d)
X90
X90
bt
Hnh 1.5. Cc s cn tm t Slab
I, II, III l cc bc ca qu trnh cn (X90- xoay 90 trong mt phng ngang);
a) cn dc (CD), bp bt;b) cn ngang, lp bt
c ) cn dc(CD), lp < bt, bp
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22
22
Ch-ng 1. Gii thiu cng ngh cn thp tm
Thp c xoay 900 v v tr dc (CD) v c cn cho n khi t c
dy cn thit. Giai on ny gi l bc cn gin di th hai:
Theo s CN, qu trnh cn gm hai giai on ( hnh 1-5d):
1. Bc cn gin di, tin hnh theo s CD cho n khi t chiu di bng
chiu rng ca tm cha ct mp sau 2 4 ln cn, vi 1 = 1,1 1,4;
2. Thp c cn theo s CN, sau khi xoay 900, cho n khi t c
dy cn thit[1].
Chiu dy ca tm thp sau khi cn ph b rng h2, c th xc nh theo cng
thc:
1 112
,hb
h mmb
(1.4)
Trong : b1, h1 tng ng chiu rng v chiu dy ca tm thp sau khi
cn gin di u tin.
b2 chiu rng cn thit ca tm thp sau khi cn ph b rng.
Lng p tuyt i- h v tng i- , cn thit cho bc cn ph b rng c th
tnh theo cc cng thc:
1 1 11 2 1 12 2
(1 ),b h b
h h h h h mmb b
(1.5)
1 2 2 1
1 2
.100% .100%h h b b
h b
(1.6)
Hnh 1.6. S cn gc
b0, l1- chiu rng v chiu di ca slab; b1, l1, b2, l2- tng ng chiu rng
v chiu di phi sau ln cn th nht v sau ln cn th hai
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23
23
Ch-ng 1. Gii thiu cng ngh cn thp tm
cc my cn mt gi trio lauta, c c chiu rng cn thit ca tm,
ngi ta thng tin hnh qu trnh cn vi phi a nghing mt gc so vi trc -
cn gc.
Trong qu trnh cn gc, chiu di v chiu rng ca phi tng ng thi.
Mc gia tng ca chiu rng v chiu di ph thuc vo gc a 0; gc a
cng ln th chiu rng tng cng t v chiu di tng cng nhiu. Trong thc t, gc
a 0 thng bng 10 200.
Chiu rng phi cn trong trng hp cn gc c th xc nh theo cng
thc sau:
)1(sin1 20
2
01
bb (1.7)
Trong : b0, b1- tng ng chiu rng ca phi (slab) trc v sau khi cn
mm; - h s gin di.
Trng hp cn gc, ti trng khi trc cn n kim loi gim i. Tuy nhin,
tiu hao kim loi cng gia tng do kh thu c kch thc vung vn ca tm
(tng lng ct bin v u, ui). Nng sut ca my cn do cng b gim i.
Trong qu trnh cn th cc my cn tm mt hoc gi, vic s dng trc
ng v h thng nh g thy lc khng phi lc no cng m bo c hiu qu
nh g cao. nng cao cht lng g, gi cn th ca cc my cn tm hai gi,
ngi ta s dng cc trc cn c rnh hoc g. Khi cn cc trc kiu ny, nh
hiu ng n ca hi nc trong cc rnh hoc g v s ph hy c do lng p
khng ng u tri rng trn ton b mt phi m hiu qu nh g c nng cao.
Yu t quan trng to hiu ng n hi l phi to c khoang kn cha
nc trong rnh (hoc g).
iu kin to c khoang kn trong rnh, cho trng hp > (- gc
nghing ca rnh; - gc n mn kim loi), c th vit nh sau:
2
1
2
14
b
Rah , mm (1.8)
Trong : h lng p tuyt i; R- bn knh trc cn; a1, b1- kch thc rnh.
Sau khi cn trong trc c rnh, trn b mt tm thp xut hin cc m g.
Nu m g qu cao, trn b mt thnh phm (sau khi cn gi cn tinh) c th to
thnh cc khuyt tt dng vy. khc phc nhc im ny, tng lng thp
trong gi cn tinh phi bng hoc ln hn 20% tng ca chiu dy ca phi (hp) v
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24
24
Ch-ng 1. Gii thiu cng ngh cn thp tm
4560
10 18mm
23 mm
3050mm
su ca rnh (a1). dy ca tm theo sau khi chuyn sang gi cn tinh ht c
th tnh theo cng thc thc nghim sau:
ht = 0,2(hp+a1) + htp, mm (1.9)
trong : htp- chiu dy thp tm thnh phm. Chiu su ca rnh thng bng
(25) mm.
Hnh 1.7. S phn b v kch thc rnh trn b mt trc cn
Trc rnh c nhc im km bn, tui th ngn, gia cng rnh trn b mt
trc phc tp v tn thi gian. khc phc cc nhc im trn, ngi ta thay
trc rnh bng cc trc g.
to g trn mt trc, ngi ta dng phng php hn, sau mi nhn
cc ng g.
So vi trc rnh, trc g c u im l ch to n gin, bn cao.
Ngoi ra khi cn trong trc rnh, cc m g to ra trn b mt thp ngui i
nhanh, cn khi cn trong trc g, cc ng lm in trn mt thp ngui khng
nhanh hn so vi ton b b mt tm, do khuyt tt b mt ca sn phm cn
trong trc g t hn.
Hnh 1.8. Trc cn c g
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25
25
Ch-ng 1. Gii thiu cng ngh cn thp tm
4
4
32
1
Qu trnh cn trong gi cn th tin hnh nhit cao. Nhit ca thp
khi vo gi cn th khong (11601200), nhit kt thc cn trong gi cn th
(1020 1050)0C.
Ph thuc vo kch thc sn phm, chiu dy ca thp khi chuyn sang gi
cn tinh nm trong khong (1580)mm.
1.3.3. Cn trong gi cn tinh
Sau khi cn gi cn th, thp c chuyn n gi cn tinh v c cn
y theo mt chiu cho n khi t c dy cn thit. Qu trnh cn trong gi
cn tinh phi m bo thu c sn phm c kch thc, chnh xc, hnh dng v
c-l tnh theo yu cu.
Tng lng p trong gi cn tinh bng (20 30)% lng p tng cng. Qu
trnh to bin dng v cht lng b mt cho php thc hin trong gi cn tinh v
ph thuc s phn b lng p ring cho cc ln cn. Do vy, m bo cc yu
cu v cht lng b mt, chnh xc v hnh dng ca sn phm, lng p c
phn b gim dn t ln cn u tin n ln cn cui cng. Trong hai ln cn cui,
lng p khng vt qu (310)%. Khi cn tm c chiu dy di 10mm, c th
xut hin mt s khuyt tt ca sn phm nh cong vnh, un sng gp phn
khc phc cc khuyt tt ny, ngi ta p dng mt ln cn vi khe cn khng i
hoc ln hn mt cht so vi khe cn trong ln cn cui cng.
Nhit ca thp khi vo gi cn tinh khng c thp hn (950 1000)0C
v nhit kt thc cn khng thp hn 7200C trnh cho thp b ha bn ng
k.
ty g to ra trong qu trnh cn trn b mt thp (g cn), gi cn tinh
c trang b h thng nh g thy lc (hnh 1.8).
Hnh 1.9. S b tr h thng nh g thy lc
1- Thp cn; 2- Vi phun nc p sut cao; 3- ng dn nc; 4- Trc cn
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26
26
Ch-ng 1. Gii thiu cng ngh cn thp tm
cc my cn tm mt gi, ch nhit v ch p cho nhng ln cn tinh
hon ton ging nh i vi gi cn tinh ca my hai gi. Tuy nhin, do ch c mt
gi, va cn th va cn tinh, nn cht lng sn phm thp hn so vi my hai gi.
Sau khi cn, thp tm c tip tc lm ngui ti sn lm ngui kiu con ln.
cng ha qu trnh ngui, y c th c trang b cc gin phun ma. Sau
khi lm ngui n nhit thch hp, thp tm c nhit luyn, nn phng trng
thi ngui v tinh chnh.
1.4. C IM BIN DNG CA THP KHI CN CC MY CN
TM
Khi cn trong cc gi trc ngang, chiu rng ca tm thp ln hn rt nhiu
so vi chiu dy. T l gia chiu rng ban u b0 v chiu dy trung bnh htb ca
tm thp thng ln hn 10. Trong trng hp ny, lng gin rng ca thp khng
ng k. Khi tnh lc cn, yu t gin rng c th b qua, c ngha l bin dng ca
thp c th coi nh phng v ng u.
gi cn trc ngang, thp bin dng trong iu kin t s lt/htb =(0,53) (lt
chiu di cung tip xc). Trong cc gi cn th lt/htb < 1,5 (nhng ln cn th u
tin tng ng lt/htb
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27
27
Ch-ng 1. Gii thiu cng ngh cn thp tm
khong cch gia hai b mt trc khi qu trnh cn n nh. Bin dng b sung
ca u trc phi thp c gii thch bi c im chy ca vt liu di tc
dng bin dng n hi ca gi cn, trong iu kin tn ti min ngoi khng hon
ton. di min bin dng b sung L bng khong 1/2 chiu rng ban u ca
phi.
S phn b khng ng u ca gin rng ti vng tip gip v bin dng b
sung hai u phi thp l nguyn nhn dn n gin rng b sung. Do vy khi cn
tm rng t phi hp theo s CD, nh mc ct mp tng (45)%; theo s cn
ngang, nh mc ct hai u tng (24)%. iu chng t, b rng ca tm thp
hnh thnh khng ch trong gi trc ng m c trong gi trc ngang.
b1
b0
llv
b)a)
b1
b2
Hnh 1.11. S cn trong gi trc ng (a) v trc ngang (b)
nh gi hiu sut s dng gi trc ng, ta cn cn c vo h s hu ch
v
vb
nb
v
1 (1.10)
Trong : bn lng gin rng b sung khi cn trong gi trc ngang, gy
nn bi gin rng khi cn trong gi trc ng;
bv lng p trong gi trc ng
Chiu rng ca thp sau khi cn trong gi trc ngang b2 ph thuc vo chiu rng
ca phi trc khi cn trong gi trc ng b0 v c th xc nh theo cng thc:
10012
bv
bbv
bb (1.11)
Trong : b1- chiu rng ca thp sau khi cn trong gi trc ng.
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28
28
Ch-ng 1. Gii thiu cng ngh cn thp tm
b1 lng gin rng t nhin ca tm thp c tit din ngang vung vn v chiu
rng b1 khi cn trong gi trc ngang.
H s hu ch ca gi cn trc ng, trong iu kin btb/ltv= (4,512) c th
xc nh theo cng thc thc nghim:
tvl
bv
tv00375,087,0 (1.12)
gim bt nh mc ct bin (theo s CD) v ct u, ui (theo s
CN), khi cn phi trong gi trc ng, ngi ta p dng phng php thay i
lng p theo chiu dc phi.
Phn u v phn cui ca phi vi chiu di (350700)mm c p trong
trc ng vi lng p thay i, nh hn lng p n nh phn gia phi. i
vi cc phi c chiu rng (10001200)mm, chnh lch v lng p hai u
v gia nm trong khong (6080)mm.
Ngoi phng php p trong trc ng vi lng p bin i theo chiu dc
phi nu trn. thu c thp tm c hnh dng vung vn, ngi ta cn p dng
phng php p hai u phi trong trc ng (p theo chiu dc).
1.5. CC THNG S NNG LNG CA QU TRNH CN TM
- Lc cn (p lc ton phn ca kim loi ln trc cn), trong trng hp cn
trong trc ngang, tnh theo cng thc:
P=ptb.Lt.b0i, (MN) (1.13)
Trong : ptb- p lc ring trung bnh ca kim loi ln trc cn, MN/m2;
lt chiu di cung tip xc (m)
b0i- chiu rng ca thp trc ln cn (m)
tnh p lc ring trung bnh, trong trng hp cn nng thp tm (khng
c lc ko cng), ta c th dng cc cng thc ca Korolev v Broman.
Cng thc Korolev, p dng khi lt/htb >1, vit nh sau:
21
1
1215,1
21
Ttbp ,MN/m2 (1.14)
Trong :
T - gii hn chy ca thp cn trong iu kin nhit , mc v tc bin
dng tng ng, MN/m2;
- lng p tng i ( mc bin dng) ,0h
h ;
htb- chiu dy trung bnh ca thp cn, htb = (ho+ht)/2,m
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29
29
Ch-ng 1. Gii thiu cng ngh cn thp tm
H s c xc nh theo cng thc sau:
h
tlyfyf
22
(1.15)
Trong : fy- h s ma st khi qu trnh cn n nh;
- gc tip xc ca thp vi trc cn;
h- lng p tuyt i, h=h0-h1
Cng thc Brovman:
+ Trng hp lt/htb >2:
tb
t
T h
l
tbp 25,075,015,1 (1.16)
+ Trng hp 0,5 lt/htb 2:
tl
tbh
tbh
tl
Ttbp
2
15,1 (1.17)
- H s ma st khi qu trnh cn n nh, fy, ph thuc vo thnh phn ha
hc ca thp, nhit cn, vn tc trt tng i gia thp v trc cn, vt liu v
trng thi b mt trc. H s ma st fy c th xc nh theo cng thc sau:
fy=k1.k2.f0 (1.18)
Trong : k1- h s tnh ti nh hng ca thnh phn ha hc thp cn (k1=
1 i vi thp cacbon thp; k1= 0,8-0,9- cc mc thp cacbon cao; k1= 1.1-1.2- cc
mc thp khng g); k2- h s tnh ti nh hng ca vt liu v trng thi b mt
trc cn; f0- h s ma st tng ng iu kin nhit v tc trt tng i cho
trc.
-Vn tc trt tng i ca thp trn mt trc, vtr, c th xc nh theo cng
thc:
0 1
1
, /3
tr t
h hv v m s
h
(1.19)
Trong : vt- vn tc bin ca trc cn, m/s.
- Chiu rng phn bin dng, bph, c th tnh theo cng thc
0
0 1,9 0,33phtv
hb h
l
(1.20)
1.6. TNH TON CH P CHO MY CN TM
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30
30
Ch-ng 1. Gii thiu cng ngh cn thp tm
Ch p trong qu trnh cn tm quyt nh mc cht ti ca cc thit b
c in, nng sut ca my, cht lng v chnh xc ca sn phm. Do vy, ch
p phi c tnh ton cho mi chng loi sn phm, c tnh ti tnh nng k
thut ca thit b, cc yu cu v cht lng b mt v chnh xc ca sn phm,
mc thp, nhit bt u v kt thc cn, khi lng v chng loi phi.
Lng p cho mi ln cn phi c xc nh cn c vo cc iu kin sau:
1.6.1. iu kin n thp
Trong qu trnh cn tm, ph thuc vo kiu my (o chiu, khng o
chiu), vn tc bin ca trc cn, chng loi v kch thc phi m lng p trong
mt vi ln cn u c th t nhiu b hn ch.
cc my o chiu v lin tc, trong nhng ln cn u tin, vn tc nh,
hai trc lm vic u c dn ng, do lng p khng my khi b hn ch bi
iu kin n thp. Gc n ti hn trong nhng ln cn u cc my o chiu v
lin tc cho php s dng lng p n (4080)mm. Tuy nhin, do b hn ch bi
nhiu yu t khc, nn kh nng ny khng c tn dng ht.
Lng p ti hn:
hmax=D(1-cosmax) (1.21)
Trong : D- ng knh trc cn
max- gc n ti hn
1.6.2. bn ca trc cn
bn ca trc cn l yu t quan trng nht quyt nh lng p. Tnh
ton lng p trn c s bn ca trc c ngha l m bo sao cho lc cn P
khng ln hn gi tr cho php Pcp:
PPcp (1.22)
Lc cho php xc nh cn c vo bn ca trc.
1.6.3. Cng sut ca ng c truyn ng
Khi p lc ton phn ca kim loi ln trc phn b ng u theo cc ln
cn, cng sut cn s gim dn t ln cn u tin n ln cn cui cng. Ta thy r
iu nh sau:
Nu cng sut cn (N) c biu th qua lc ma st (T) v vn tc trc (v) th
trong ln cn u tin ta c N1 = 2T1v1, trong ln cn th hai N2=2T2v2. Khi qu
trnh cn n nh th
T1= P1tg(1/2), T2= P2tg(2/2), vi i- l gc n kim loi trong cc ln cn. Nu P1=
P2, ta c:
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31
31
Ch-ng 1. Gii thiu cng ngh cn thp tm
2
1
2
1
2
1
h
h
N
N
(1.23)
lc cn phn b ng u theo cc ln cn, lng p phi gim dn t ln
cn u tin n ln cn cui cng. Nh vy, theo cng thc nhn c trn, cng
sut cn cng gim dn theo cc ln cn.
Ch p phi tha mn c cc iu kin:
Nm Ncp (1.24)
Trong : Nm- cng sut ng c tnh c; Ncp cng sut cho php ca ng c.
1.6.4. Nhit kim loi
Nhit cn nh hng n lng p qua gii hn chy ca thp, hay ni
mt cch khc, qua p lc ca kim loi ln trc.
Qu trnh cn my cn tm thng c tin hnh vi ch nhit sau
y:
+ Bt u cn th: (1150 1250)0C
+ Kt thc cn th: (1000 1100)0C
+ Bt u cn tinh: 9800C
+ Kt thc cn tinh: (850870)0C
Nhit ca thp trong mi ln cn tip theo ph thuc vo chiu dy ca
thp, s ln cn trc , thi gian cn
Trong qu trnh cn, nhit ca thp qua mi ln cn, c bit l cc ln
cn cui cng, gim i r rt, cn tr khng bin dng v p lc ca kim loi ln
trc tng ng k. Do , vic xc nh nhit ca thp sau mi ln cn l rt cn
thit.
gim nhit ca thp sau ln cn th i (Ti ) c th tnh gn ng theo
cng thc:
,.
4
1000021.0
ih
it
iT
iT
0C (1.25)
Trong : Ti nhit ca thp trong ln cn th i (K)
ti tng thi gian cn ln th I v thi gian ngh tip theo(s)
hi chiu dy ca thp sau ln cn th i(mm)
Ch p ti u phi m bo c cc yu cu sau y [1]:
1. Nng sut ca my i vi chng loi kch thc cho trc phi cao nht
c th
2. Cht lng sn phm phi ph hp vi tiu chun v cc yu cu k thut
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32
Ch-ng 1. Gii thiu cng ngh cn thp tm
3. Phi tn dng trit c kh nng ti ca cc thit b c- in.
4. H s tiu hao kim loi v gi thnh sn phm phi thp nht c th.
5. Phi pht huy c kh nng c kh ha v t ng ha qu trnh cn.
Tnh ton ch p cho my cn tm c tin hnh theo trnh t sau:
1. Chn s cn (CD hoc CN) hp l nht. Trong mi trng hp c th,
khi chn s cn phi cn c vo cc yu cu v nng sut my, h s tiu hao
kim loi, cht lng b mt, chnh xc v c-l tnh ca sn phm
2. Chn phi. Cn c vo s cn chn, ta tnh khi lng v kch
thc ca phi slab.
3. Phn b lng p cho cc gi cn v cho cc ln cn. Tng lng p cc
gi cn th ca my cn tm thng chim khong (70 80)% lng p tng cng,
cn gi cn tinh ch chim (2030)%. Phn b lng p cho cc ln cn phi cn
c vo lng p ti hn, lng p phn b cho cc ln cn theo hng gim dn.
nhng ln cn th cui, lng p thng b hn ch bi bn ca trc cn v cng
sut ca ng c truyn ng. nhng ln cn tinh cui, lng p b hn ch bi
yu cu v cht lng b mt ca thp thnh phm.
4. Chn ch vn tc cn v xc nh nhit ca thp sau mi ln cn.
Ch vn tc cn phi m bo sao cho chu k cn nh nht c th.
5. Tnh lc cn cho php.
6.Tnh p lc ring trung bnh (ptb), p lc ton phn ca kim loi ln trc
cn(P) v so snh kt qu tnh c vi lc cn cho php. Nu P > Pcp th phi gim
P bng cch gim lng p.
7. Tnh ton m men cn v cng sut ca cc ng c truyn ng. Nu
cng sut tnh c ca ng c ln hn cng sut cho php ta phi phn b li
lng p hoc sa i ch vn tc cn.
8. Xc nh thi gian chu ti ca gi cn th v gi cn tinh (i vi cc
my hai gi). Thi gian chu ti ca hai gi phi xp x nhau.Trong trng hp
chnh lch qu ln, phi hiu chnh li ch p. Ch p sau khi hiu chnh phi
tha mn cc iu kin n thp, bn trc cn, cng sut ng c truyn ng
1.7. NHIT LUYN V TINH CHNH THP TM
Qu trnh tinh chnh thp tm tin hnh sau khi cn, bao gm cc nguyn
cng sau: nn phng, lm ngui, ct, nhit luyn, ty khuyt tt b mt v cc
nguyn cng khc. Nh vy, tinh chnh thp tm cn nhiu loi thit b khc
nhau. c im, tnh nng k thut ca cc thit b cng nh thnh phn v phn b
thit b b phn tinh chnh ph thuc vo kiu my v chng loi sn phm cn.
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33
Ch-ng 1. Gii thiu cng ngh cn thp tm
cc my cn tm, c cu v s phn b thit b tinh chnh cho php t
chc dy chuyn lm vic mt cch lin tc. i vi cc chng loi chiu dy khc
nhau, do thi gian lm ngui v thit b tinh chnh khng ging nhau, nn dy
chuyn lm vic c t chc ring bit cho mi loi chiu dy.
tng phng, thp c nn sau khi cn. Nguyn cng nn thng tin
hnh trng thi nng, nhm lm gim lc nn v ng sut d trong thp. Do ,
my nn nng c t tip trn ng bng ln sau gi cn tinh. Nguyn cng nn
ngui ch p dng i vi thp khng qua nn nng v sau khi nhit luyn.
nn phng thp tm, ngi ta s dng my nn gm hai gin con ln b
tr song song (hnh 1.12).
Qu trnh lm ngui thp tin hnh trong khi vn chuyn theo ng bng
ln, sn ti v trn gi lm ngui. Trn ng bng ln, thp c lm ngui bng
bi nc n (600800)0C, sau chuyn n my nn nng. Sau khi nn, thp tip
tc c lm ngui trn sn ti v trn cc gi lm ngui.
Nguyn cng kim tra cht lng b mt thp c tin hnh khi thp
ngui ti bn kim tra, c trang b my lt tm. Tip theo thp c chuyn n
b phn ly du kch thc v n my ct.
Nhit luyn thp tm c p dng rng ri nhm tng tnh do v hon
thin t chc hoc nng cao cc c tnh bn.
Thng ha l dng nhit luyn ph bin i vi thp tm t cc mc thp
cacbon v thp hp kim thp. Thng ha l qu trnh nung thp n nhit cao
hn im ti hn trn khong (2030)0C, sau lm ngui ngoi khng kh hay
trong l cho n nhit thng. Sau khi thng ha, thp c t chc ht nh v
c kh bin cng, do c tnh do v c tnh tt hn.
i vi thp tm t cc mc thp cacbon v thp hp kim thp, c chiu dy
ln hn 15mm, thay cho thng ha, ngi ta p dng dng nhit luyn ti km
theo ram.
i vi thp tm t cc mc thp hp kim, tng gin di tng i,
gim cng v gii hn bn, ngi ta p dng phng php .
Thp tm dy (1215)mm t cc mac thp cc bon trung bnh v thp
ccbon cao c th c nhit luyn ha bn. Thp c nung ti (900920)0C v
Hnh 1.12. S nn phng thp tm vi hai gin con ln b tr song song
Thp tm
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34
Ch-ng 1. Gii thiu cng ngh cn thp tm
lm ngui trong nc my ti p, nhm ngn nga s cong vnh. Sau khi nhit
luyn ha bn, bn ca thp tng (20 25)% trong khi do ca thp vn gi
c mc trung bnh.
nhit luyn thp tm, ngi ta dng cc l c sn con ln, thp c th np
vo l trng thi nng hoc ngui.
Ngoi cc dng nhit luyn nu trn, ngi ta cn p dng rng ri phng
php ha bn nhit thp tm t nhit cn. Ha bn nhit t nhit cn l mt
dng ca phng php gia cng nhit c, da trn c s kt hp gia qu trnh nhit
luyn v qu trnh bin dng do.
Mc bin dng trong ln cn cui cng, dy ca thp, nhit cn ln
cui, nhit ti, tc lm ngui, nhit ram,l cc yu t c bn nh hng
n c tnh ca thp c ha bn t nhit cn. Thc t cho thy, mc bin
dng trong ln cn cui cng t 10% n 20% cho php kt hp cc yu t khc
t c c tnh ti u ca thp tm dy.
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35
Ch-ng 1. Gii thiu cng ngh cn thp tm
1.8 Gii thiu quy trnh cng ngh ca nh my cn thp Ci Ln
1.8.1 S quy trnh cng ngh sn xut
Phi thp
Chun b phi v gia nhit
Kh vy bng nc cao p
Cn
Nn thng bng my nn thng
Sn ngui lm ngui
Kim tra v mi gia cng b mt
My ct a ct hai bin
My ct nh thc ct u ui v ct
nh thc
Ct nh thc ly mu
Thu gom thp tm
Kim tra, mi gia cng, nh nhn mc, ct,
thu gom
nhng tm thp dy
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36
Ch-ng 1. Gii thiu cng ngh cn thp tm
nh nhn mc thp tm
Nhp kho thp tm
1.8.2 Khi qut quy trnh cng ngh sn xut
1.8.2.1 Chun b phi v gia nhit
Gia nhit cho phi thp s dng cng ngh a phi vo trng thi ngui.
Nhng phi thp c mua t bn ngoi c kch thc ph hp vi yu cu c
xe vn chuyn ti nh my, dng cu trc xp ng. Nhng phi thp cn c
ct th phi dng cu trc vn chuyn n khu vc ct uc ct thnh nhng phi
thp c kch thc quy nh, sau li dng cu trc a phi thp ln bn con
ln ln liu, sau li thng qua thit b cn phi cn phi sau phi thp c
chuyn n bn con ln vo l, my y phi thp s y phi thp vo l. Cn c
vo yu cu v cng ngh v nhp cn, sau khi gia nhit cho phi thp n
khong 1100~12500C, s dng my y thp y thp ra khi l nung thng qua
tm trt chuyn phi thp sang bn con ln ra l
1.8.2.2 Kh vy bng nc cao p
Phi thp t bn con ln sau khi ra l chuyn ti bn con ln kh vy bng
nc cao p, m cc ming phun nc cao p 18Mpa kh cc vy thp ti mt trn
v mt di ca phi thp. Sau li chuyn phi thp n bn con ln vn chuyn
trc my cn. cao ca cc ming vi phun nc pha trn thng nc cao p c
th iu chnh c theo dy khng ging nhau ca thp tm.
1.8.2.3 Cn
Thp tm c vn chuyn a ti my cn bn trc o chiu thng qua
bn con ln chuyn thp trc my cn, cn c vo k hoch cn, loi thp, mc
ch s dng thp c th la chn hai phng thc cn l cn thng thng v cn
khng ch, dng kiu cn c th xoay phi theo chiu ngang dc 900, di ln
nht ca phi thp sau khi kt thc qu trnh cn l 26m, rng ln nht l
3100mm.
1- Cn thng
Khi di ca phi thp tng i ngn phi thp theo chiu ngang i vo
trong my cn bn trc o chiu s tin hnh cn nh hnh, thng thng thng
qua 1~4 ln cn nh hnh tin hnh xoay phi 900 trc my cn, sau tin hnh
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37
Ch-ng 1. Gii thiu cng ngh cn thp tm
cn theo chiu rng; sau khi cn n rng theo yu cu th li tin hnh xoay
phi mt ln na sau cn n dy theo yu cu.
Khi phi thp gn t ti hoc t ti chiu di ln nht, th phi thp c xoay
900 trc my cn, sau tin hnh cn theo chiu rng, sau khi t n rng
theo yu cu th tin hnh xoay phi 900 trc my cn, sau cng cn theo chiu di
cho ti khi t ti dy theo yu cu.
Trong qu trnh cn, h thng t ng iu chnh dy bng thu lc s tin
hnh t ng iu chnh iu chnh dy ca chi tit cn.
Nhm nng cao cht lng b mt thp tm, th trong qu trnh cn cc ng gp
nc cao p trn my cn bn trc o chiu s tin hnh kh sch cc vy thp
bm trn n.
2- Cn khng ch
i vi cc loi thp tm ng tu, cc loi thp hp kim thp ca ccbon th
dng cng ngh cn khng ch.
Cn c vo yu cu v chng loi thp, quy cch v tnh nng sn phm s dng
phng thc cn hai giai on. Khi s dng hai thp tm cng cn, th mt tm
ang cn v mt tm ang trong giai on i gim nhit .
Hai giai on thng thng gi l: giai on th nht i nhit, giai on th hai
cn, i vi cc loi sn phm khc nhau th c nhng yu cu khc nhau v s ln
cn, nhit ch, lng p xung, nhit kt thc qu trnh cn. Thng thng
th nhit bt u cn l 1050~11500C, giai on cn th nht cn khong 6~9
ln, t sut p xung chim 60% tng lng p, giai on ch gim nhit khong
850~8800C, giai on cn th hai cn khong 5~6 ln, nhit thnh phm sau khi
kt thc qu trnh cn l 770~8500 C
Khi chi tit cn i gim nhit trn bn con ln i gim nhit , th bn
con ln phi chuyn ng lin tc theo hai hng trc v sau, trnh khng to nn
nhng vch en trn thp do con ln hp th nhit t thp, ng thi bo v cho
ng con ln khng b h hi.
1.8.2.4 Nn thng ti my nn nng
Thp tm c a t bn con ln vn chuyn thp ca my nn n my
nn tin hnh nn thng, nhit khi nn khong 600~8000C.
Tc nn c xc nh cn c vo nhit tm thp khi nn, dy v tnh
nng ca thp, phm vi tc khong 0.6~1.6m/s.
Lng p xung ca my nn ch yu c quyt nh bi nhit , dy v tnh
nng v cng ca thp tm, thng thng la chn trong khong 1.0~5.0mm,
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Ch-ng 1. Gii thiu cng ngh cn thp tm
i vi nhng tm thp c nhit thp th la chn gi tr nh, i vi nhng tm
thp c nhit cao th la chn gi tr ln. Ngoi ra khi la chn lng p xung
khi nn cn phi tnh ton n s nh hng ca dy tm thp, nhng tm thp
mng lng p xung ln, nhng tm thp dy th lng p xung nh.
S ln p xung trong qu trnh nn thng thng l 1 ln, i vi nhng
tm thp c cn khng ch c th sinh ra khng bng phng ln sau khi kt
thc qu trnh cn, nhm t ti yu cu v bng phng ca thnh phm cn cn
phi tin hnh cn i nn li 1~2 ln, khi nn li c th nhc trc ca my nn ln
con ln chuyn ng ngc tr li.
1.8.2.5 Lm ngui ti sn ngui
Thp tm sau khi nn xong th nhit thng thng l 600~8000C c
a vo sn ngui. Thp tm tng tm thp mt c t dn ln sn ngui, thng
qua dy xch v a xoay, di chuyn tm thp trong tnh trng khng b va chm v
khng b co xc i cho n khi nhit thp tm xung khong 1500C th ri
khi sn ngui.
1.8.2.6 Kim tra b mt v mi gia cng
Thp tm sau khi ri khi sn ngui t bn con ln ca sn ngui c
chuyn ti bn con ln trn gi gia cng tin hnh kim tra b mt ca thp tm,
i vi nhng khuyt tt trn b mt ca thp tm s do cng nhn dng my mi
tin hnh mi gia cng cho sn phm. Sau khi gia cng xong th chuyn thp
ti tuyn ct. i vi nhng tm thp c khuyt tt ti mt di c pht hin nh
gng kim tra khuyt tt th thp c my lt tm lt mt ca tm thp, chuyn
sang khu vc gi mi gia cng v li c gia cng b mt bng phng php
th cng, sau li c lt tm v chuyn n bn con ln vn chuyn trn tuyn
ct.
1.8.2.7 Ct bin bng my ct a (thp c dy t 30mm tr xung)
Thp tm c vn chuyn n bn con ln trc my ct, thng qua thit b
nh v tm thp bng t tnh v nh du bng quang hc tin hnh c nh nh v
thp tm, cho hai mp ca thp tm c song song v cn i vi nhau. Li khi
ng bn con ln vn chuyn trn my ct, bn con ln vn chuyn sau my ct,
my ct a (bao gm c ct vn), vn chuyn vi cng 1 vn tc, my ct a tin
hnh ct hai mp ca tm thp.
Cn c vo dy v cng ca thp tm m my ct a ct thp vi
nhng vn tc khc nhau, vn tc ct l 0.2~0.8m/s, thp tm sau khi c ct s
chuyn n khu vc my ct nh kch thc.
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39
Ch-ng 1. Gii thiu cng ngh cn thp tm
ng thi nhng mp thp c ct ra s c ct vn. Nhng vn thp
sau khi i ra t my ct vn s c a n my vn chuyn thng qua nhng rnh
dn thp, ng thi vn chuyn n hp ct u.
1.8.2.8 My ct nh thc ct u ui, ct nh kch thc
Nhng thp tm c ct bin th s tip tc c a n bn con ln
vn chuyn trc my ct, sau khi c nh v ngay ngn, cn c theo yu cu
ct u, ng thi cn c theo yu cu ca hp ng ct thp tm thnh
nhng tm c di khc nhau, sau cng ct phn ui. Tm thp nh kch thc
c chiu di ln nht l 18m.
1.8.2.9 Ly mu ct nh kch thc
Khi cn thit phi ly mu kim tra phi cn c theo yu cu ct thp,
do ngi cng nhn mang n phng kim nh.
1.8.2.10 Thu gom thnh phm
Nhng thp tm thnh phm c vn chuyn n bn ngoi ng con ln
thu gom thnh phm, i vi nhng tm thp c di nh hn 12m v trng lng
nh hn 4, 5 tn c cu mang i bng nhng cu trc mm t 5+5 tn, cn c
theo nhng quy cch ca thp tm m c xp ng ti khu vc thnh phm. i
vi nhng tm thp c di ln 12m hoc khi lng ln hn 4, 5 tn th dng
loi cu trc mm t 10+10 tn hoc dng loi cu kp xp ng thnh phm.
1.8.2.11 nh nhn mc
Nhng tm thp c ct theo ng kch thc c chuyn n ng
con ln thu gom thnh phm, sau dng cu kp hoc cu mm t di chuyn
thp n khu ng nhn mc v c ngi cng nhn ng nhn mc cho thp
tm, ch yu ghi ln c biu tng ca cng ty, loi thp, quy cch, ngy sn
xut
i vi mt s loi thp tm chuyn dng c ngnh cng nhn nh thp tm
ng tu khi cn thit cn phi nh du ln c biu tng ca cng hi.
1.8.2.12 Nhp kho
Nhng chng thp sau khi thu thp xong dng loi cu trc hai mc cu
thp n khu vc xp thp, nhp kho, xut hng. i vi loi thp tm c chiu di
ln hn 12m c th trc tip dng cu trc mm t cu thp t khu vc bn con ln
sang khu vc xp ng, sau dng loi cu trc mm t hoc kiu kp 10+10 tn
a vo kho xp ng, ch xut xng.
1.8.2.13 Kim tra, mi gia cng, nh nhn mc, ct, thu thp nhp kho cho
nhng loi thp c dy t 30mm
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Ch-ng 1. Gii thiu cng ngh cn thp tm
Thp tm sau khi i qua sn ngui, c chuyn n sn mi gia cng, sau
khi thng qua kim tra, mi gia cng, nh nhn mc dng my lt tm kim tra
b mt di ca tm thp, sau khi gia cng, nh nhn mc xong, dng cu trc
loi 30 tn mc thp ln xe vn chuyn n khu vc ct uc. Khi cn thit phi
ct uc th dng cu trc vn chuyn n khu vc ct uc, my ct uc s tin
hnh ct u ui, ct bin, ct nh thc, sau vn chuyn n khu vc xp
ng. Khi cn xut hng, dng cu trc loi 10+10 tn chuyn thp ln xe in ng
20 tn, ng thi vn chuyn n khu vc thnh phm, li dng loi cu trc 10+10
tn chuyn thp ln xe ch giao hng.
* KT LUN CHNG 1
Trong chng ny gii thiu khi qut v cng ngh cn thp tm, gii
thiu quy trnh cn thp tm ca mt nh my c th. Vn t ra l lm th no
nng cao cht lng ca sn phm thp tm. lm c iu trc ht
chng ta i nghin cu m hnh ton hc v cu trc ca cc b iu khin trong h
thng cn thp tm (chng 2) thy c u v nhc im ca cc b iu
khin ny. T s thit k b iu khin nng cao cht lng ca h thng cn
thp tm.
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
Chng 2
M HNH TON HC V CU TRC CA CC B IU
KHIN TRONG H THNG CN THP TM
Trn th gii, h thng cn thp tm c cc nh iu khin hc nghin cu v s
dng rng ri t rt lu nhng u c n gin ha, h l h tuyn tnh mt u
vo - mt u ra hoc hai u vo- hai u ra. Cc phng php m hnh ho h
thng cn c xy dng t kinh nghim, thc nghim n l thuyt. Miura et al
(1993), K.Hunt (1993), Large et al (1994), v Hwang et al (1996) m hnh qu
trnh cn thp dng trong iu khin chiu dy. Cc m hnh ton hc ny da vo
s thay i ca chiu dy ph thuc vo lc cn. Cc tc gi ny khng xt n nh
hng phi tuyn ca h thng thu lc v do vy cc m hnh ny tng i n
gin. Cc phn t phi tuyn c tuyn tnh ho v h l h mt u vo-mt u ra
tuyn tnh. Trong cc ng dng khng yu cu cao v chnh xc v vng n
nh, cc phng php trn c th s dng c.
Pedersen et al (1998), Lar Malcolm Pedersen v B.Wittenmark (1998)
pht trin b iu khin hai u vo-hai u ra iu khin qu trnh cn. Trong
phng php iu khin ny, n gin ho m hnh ton hc c s dng. Hn
ch ca cc phng php trn l vng n nh ca h thng iu khin b thu nh.
Hn na cc b iu khin ny khng k n nh hng ca nhiu ni v ngoi, sai
s do lch tm ca cc trc cn, khe h ca du bi trn, v cc phn t phi tuyn
khng m hnh ho c.
Ngoi ra, cc tc gi, xem J.W.Perng, K.W.Han (1998) a ra mt s gii
php thit k cc b iu khin phi tuyn ti u H cho h thng cn thp tm
Trong chng ny gii thiu mt s b iu khin cho h thng cn thp tm
c cc tc gi cng b.
2.1. B iu khin tuyn tnh PI [5]
Cc i lng vt l c bn ca qu trnh v cc bin c lin quan tham gia
vo vn iu khin c a ra trong hnh 2.1
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42
Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
he
le
vl
la
vw
srs0+2sr
ha
fw
Hnh 2.1. M hnh h thng cn tm
- fW l lc cn,
- he dy ca phi u vo ;
- ha l dy ca phi ti u ra ;
- le v la l nhng v tr ca sensor dy;
- s0 l khong cch con ln vi lc cn bng khng;
- sr l kch thc ca con ln khi lc cn bng khng;
- vi l vn tc u vo;
- vw l vn tc u ra.
Cc bin s c o l he, ha, vi, vw, v fw. ng lc hc ca con ln c th
c xem nh h thng l xo gim chn vi s dch chuyn hiu qu ca u vo
s0, khong cch con ln khi lc cn bng khng (fw = 0). Khong cch con ln lm
vic pha di s rng hn ty thuc vo chiu dy ca di u vo he v co dn
theo chiu ng. Mc tiu iu khin l gi ha cng gn vi gi tr mong mun haref
cng tt.
2.1.1. M hnh ton hc
Cc phng trnh c bn ny thit lp mi quan h gia cc bin c cho
bi cc im cn bng xc nh bi cc c trng ca vt liu v ng cong lm
vic ca gi . Cc c tnh ca gi c m t bi cc quan h tuyn tnh sau:
w 0af M h s (2.1)
y M khng i. Cc c tnh ca vt liu c cho bi :
'w , , , e a ef f K R h h f (2.2)
Trong :
K: gii hn n hi trung bnh (N/ m2);
: ng sut ko trung bnh (N/ m2);
: h s ma st gia con ln lm vic v ti
R': bn knh con ln bin dng (m)
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
2 4 2
02 4 22 4
s s se
v V Vds s h
M M M
fe : s hi phc n hi u vo (N)
m phng h thng, cng thc (2) c n gin ha nh sau:
w 0af M h s (2.3)
im cn bng c cho bi cc giao im ca hai ng cong lc, c th l
(2.1) v (2.3). V (2.3) l bc hai nn th c c mt gii php ng cc im giao
nhau ha. Trong thc t, xem xt
aeSa hhvshM )( 0 (2.4)
v gii ra vi ds = ha s0 , cho ta:
Trong : 0ah s ds
v wf Mds
Ngoi ra, mi quan h gia cc vn tc c cho bi we i
a
h vv
h . Cc cm bin
o chiu dy u ra c t cch my cn la (m). Theo cch ny, thi gian cht
lin quan n s o c ca ha l Ta = la / vW. Mt khc, he c lin quan n mt tr
quan h vi vi cho bi Te = le/vi. Cc hiu ng nhiu khng cha trong cc m
phng. Mi hiu ng ng hc t cc thit b truyn ng v b cm bin c
b qua. Mc tiu iu khin c bn l gi cho dy ca vt liu u ra ha
cng gn vi gi tr mong mun haerf cng tt, l
max
2
0
t
aerf a t
t
I h h dt
(2.5)
Vn tc u vo ca phi cn c cho bi mt ng cong l thuyt vi
mt giai on nht nh ca tng v gim tc (mt on dc ln t 1- 5 m/s, theo
ung thng, sau l on dc xung). Mi thay i ca chiu dy u vo phi
cn he c coi l nhiu. y, mt bin dng nht nh vi nhng thay i xung
quanh im vn hnh he=5mm c chn.
2.1.2. Cu trc b iu khin
Cu trc ca b iu khin PI truyn thng cho h thng cn tm gm hai
thnh phn: b iu khin phn hi v b iu chnh nhiu tc ng u vo nh
hnh 2.2.
Trong
:
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
U
VPIharef
DS0
e-sTa
Dhe
U
V
I
V
B iu khin
ha
Hnh 2.2. Cu trc ca h thng cn vi b iu khin PI
Trong :
- Bin Dhe v Dso : biu th cho nhng sai s nh ca im lm vic (he = 5
mm, ha = 3 mm, s0 = 2 mm).
- Te : thi gian tr
- Bin he (Dhe) : biu th cc gi tr o tr ca dy phi trc khi vo gi
cn.
- Khuch i U v V l cc o hm ring ca hm truyn ti im vn hnh.
n gin, thi gian tr Te c b qua trong cc s khi. B iu
khin iu chnh nhiu tc ng u vo c gii thiu b cc nhiu o c
A/Ie. Cc iu khin phn hi PI thit lp sai s bng khng trng thi n nh.
Thi gian tr Te ph thuc vo vn tc ca phi.
y gii thiu b iu khin tn hiu trc b trc cho gi tr nhiu
Dhe. B phn hi PI c dung sai bng khng trng thi bn vng.
Thi gian tr Te ph thuc vo vn tc ca phi .
( )( )
aa
W
lT t
v t (2.6)
Hng s thi gian ca PI l Ti s c chun ha Ta bng cch thm bin T
t c h thng kn bt bin theo thi gian.
, i
a
TT
T (2.7)
t c bin pha 65, im gc ca h iu khin c t tn s 2,2
[rad/s] v T = 0,454 ; K= 0,316 (-10dB).
2.1.3. Kt qu
Phn ng ca h iu khin tn hiu trc v h phn hi c trnh by nh
hnh 2.3
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
Hnh 2.3 Phn hi trng thi vng kn ca h iu khin PI
R rng sai s ca qu trnh chy m phng ln u tin v cui cng s ln
lt tng ng vi qu trnh tng tc v gim tc ca phi.
* Hn ch : B iu khin ny s khng t c sai s bng khng khi my
cn thay i theo thi gian. Nhng tn hiu nhiu ph thuc vo dy u vo
phi v khong cch ly mu. Cc nh l do s thay i ca chiu dy u vo v
khong thi gian ly mu. Trong trng hp xu nht b iu khin iu chnh
nhiu tc ng u vo phn ng vi chu trnh ly mu qu chm.
2.2. B iu khin a bin [6]
Chc nng ca my cn thp nng l to ra mt sn phm thp dng tm t
mt khi thp c lm nng, tc l cn mng v ko di tm thp. dy ca
tm thp s gim bng cch ko tm gia 2 con ln c t song song nh
hnh 2.4. dy ca tm thp c kim sot bng con ln trn. Bi ton t ra l
lm sao kim sot c dy tm thp. y ngi ta thit k b iu khin c
th kim sot ring r dy 2 cnh bn ca my cn. u tin ngi ta tuyn
tnh ha h thng nh v bng tuyn tnh ha phn hi sau dng thit k khng
gian ring bc hai cho h thng a bin c tuyn tnh ha. c th t c
sai s dy tnh bng khng ngi ta dng thm b iu khin tch phn.
Hng chuyn ng quay, con ln trn
V tr con ln trn
Hng cn Vng lnh
Hng chuyn ng quay, con ln di
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46
Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
.
Hnh 2.4. Qu trnh cn nhn t hng vung gc vi hng
chuyn ng ca phi
2.2.1. M hnh ton hc
My cn c phn chia thnh hai h thng con nh hnh 2.5
+ Cc h thng nh v thy lc
+ Gi cn bao gm v my cn, cc vt, 4 con ln v phi.
Hnh 2.5. My cn nhn t gc song song vi chuyn ng ca phi
rng ca phi c kim sot bng cch iu chnh v tr ca h
thng thy lc. C 2 h thng thy lc ging nhau, t ti mi u con ln mt
h thng. Ta c th kim sot v tr ca c 2 u con ln trn iu ny lm cho
qu trnh a bin v mt thay i ti mt u con ln cng nh hng n dy
ca u kia.
V my cn
V my cn Pittong
Van tr ng
Pittong bi trn
H thng thy lc nam
Con ln trn
Con ln d phng
Con ln lm vic
Con ln d phng
Con ln lm vic
phi
H thng thy lc bc
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
Gi cn
H pha bc
H pha nam
zcn
zcs
xrn
xrs
vcn
vcs
Hnh 2.6. S khi cho h thng cn
H thng pha bc c tham chiu cho v tr trt van pha bc xrn, lc
trt fn v o hm cnd
fdt
l u vo v v tr zn ca con ln pha bc l u ra.
H thng cho con ln pha nam c cng cc tn hiu u vo v u ra. K hiu n
v s ch cc bin ln lt l ca h pha bc v pha nam ca con ln.
Trong hnh xrn v xrs ch ra v tr ca trt van ca van tr ng, vcn v vcs
l dy cnh.
Ngi ta xy dng 2 khi cho gi cn:
+ 1 khi s dng thit k b iu khin
+ 1 b quan st c on dy
Khi thit k b iu khin c zn v zc lm cc u vo v dy phi pha
bc vcn dy pha nam vcs lm u ra. Ta cng c c nhng c on cho lc
cn fcn v fcs v o hm dt
dfcn v
dt
dfcs lm u ra cho khi.
2.2.1.1. H thng thy lc
Cc m hnh cho h thng thy lc pha bc l phi tuyn. Xem [8], [9],
[10], [11].
2( ) ( ) ( ) ( ( )) ( ) ( )
1 1 3cn n cnt a x t t a z z t f t a f t
n rn n t n n nz (2.8)
Trong
( )
1 ( )
( ) 0( )
( ) 0
rn
rn
f ts nn
f ts s n
P x tt
P P x t
(2.9)
Trong : - , an1, an2, v an3 l cc tham s dng cha bit.
- Ps l lc p u vo v zt l v tr cc i ca pittng.
\
fcn v cnd
fdt
fcs v dt
dfcs
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
S hng u tin trong m hnh m t dng chy qua van tr ng, s
hng th 2 v th 3 m t dng do p lc du thy lc v dng d r gia pittng
v thnh xy lanh.
Cc tham s ca m hnh cho h thng thy lc c tm thy bng
cch s dng cc gi tr o tham chiu cho cc v tr ca van tr ng xrn v xrs,
cc lc cn fn v fs v tr con ln zn v zs t my cn nng ti nh my Cn an
Mch.
Cc kt qu t vic xc nh thng s cho thy an1 c th c xem nh
hng s trong khi an2 v an3 c th thay i cc iu kin lm vic khc nhau.
2.2.1.2. Gi cn
S dng mt m hnh vt l cho gi cn v c hc Lagrng cho cc
phng trnh vi phn mt phn sau:
),0();,(21)4(
2
1),(
2
1),(
2
1),(
2
1 xtx
dmddmdvatxvAtxvatxvEI (2.10)
Vi cc iu kin bin, xem [12], [13]
)(),(2
1),(
2
1)2/(
)(),0(2
1),0(
2
1)2/(
0),(2
1
0),0(2
1
)3(
)3(
)1(
)1(
tztvtvKEI
tztvtvKEI
tv
tv
S
n
dd
dd
d
d
(2.11)
Trong (vd) (n) ch n ln vi phn 1 phn tng ng vi t. am1 v am2 l
cc tham s d liu; EI v K l cc s hng cng lin quan n gi cn, A l
khi lng ring ca khi con ln, vd l bin dng dy ca phi
v Tsn zzz l vect chuyn v ca h thng thy lc. S dng mt chuyn trng thi v phng php Galerkins[14], nghim
ca (2.11) c th bng xp x:
)(2
1)()()(),(
2
1
tzxtqxtxv cii
d i
(2.12)
Trong i l cc o hm ring, l hm s dng trong trng thi
chuyn, v qi l cc ta . Cc hm ring 1 v 2 v cc ta qc1 v qc2 c
lin kt theo cc phng trnh vi phn:
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
)(2
1
)(
)(0)(
)(2
10
)(
)(
0)(
2
1)()(
32
1
2
1
112
12
tzAty
tyItq
tzty
tyI
aEI
atzBtyAty
c
cc
c
ccccc
m
m
(2.13)
Trong
2 3 4EI A (2.14)
Trong 1, 2, 3 v 4 l cc ma trn 2x2 c trong mu.
1 2 1 2 yT T
c c c c c cq q q v y y
l cc bin trng thi ca phng trnh vi phn (2.13). Ch c vit di cho thy
cc bin l u ra ca m hnh thit k b iu khin.
S dng cc iu kin bin ca (2.11) cng lc mi quan h gia yc v qc
ca (2.13) b quan st c th c xy dng
5 3
2 1 5 2 3
3
1
2
1( ) ( ) ( )
2
( ) 1( ) 0 ( )
( ) 2
e
m m
e
c
c
Ay t f t z t
a a
y tq t I A z t
y t
(2.15)
Trong f = [ fn fs ]T v 5 l ma trn 2x2 c trong mu. Ch s e ch ra
cc bin ny thuc v b quan st.
Dng (2.12), dy ti cc cnh c th c vit di dng
)()(
)()(
2)(
2)(
tztce
tztcc
qtv
qtv
D
D
(2.16)
Trong T
v v vc cn cs
, v l cc ma trn 2x2 c trong mu.
Vic s dng ve cho ta mt kt qu chun xc hn v b quan st c lc cn nh
mt u vo b sung. Mt c tnh lc cn f c th c tnh ton t cc iu
kin bin ca (2.11)
)(2)( tqKtf Cc (2.17)
Trong T
c cn csf f f . Ta thm vo c mi quan h xp x
03 D A (2.18)
iu ny s c s dng trong thit k b iu khin.
Cc tham s mu cho my cn (2.13) v (2.15) c tm ra bng cch
s dng tnh ton lc cn f, v tr con ln z, v dy v t con ln cn nng ti
nh my Cn an Mch.
2.2.2. Thit k b iu khin
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
Nhn vo cu trc b iu khin (hnh 2.7), ta c T
rn rsx x x l u vo
ca qu trnh cn v z, f l cc bin o c.
2.2.2.1. Tuyn tnh ha phn hi
Ngi ta chn tuyn tnh ha phn hi kim sot h thng thy lc v
phng php ny kh l n gin v em n kh nng iu khin h thng thy
lc tt mi v tr lm vic. L thuyt chnh ca tuyn tnh ha phn hi l thc
hin thit k b iu khin trong 2 bc. Trong bc th nht ngi ta thit k
quy lut phn hi lm cho h thng tuyn tnh t u vo n u ra c h
thng v trong bc 2 mt nh lut kim sot tuyn tnh c thit k cho h
thng tuyn tnh. iu ny c th c xem nh kim sot theo bc vi mt
vng lp trong phi tuyn v mt vng lp ngoi, xem hnh 2.7.
Tuyn tnh phn hi cung cp kh nng kim sot cho vng lp trong phi
tuyn.
))()()()(()(
1)( 3322
11
tKztrtatata
tx nnnnnnnn
rn
(2.19)
Tuyn tnh phn hi H thng cn
-L B quan st
B tch phn Tnh ton dy
vr
qe
ve
xv
z
i
r
f
ye
Hnh 2.7. Cu trc ca h thng cn vi b iu khin a bin
Trong hnh vr l tham chiu dy ti cnh phi, v l dy thc ca phi,
ve l dy phi ti cnh c b quan st c on, f l lc cn, z l v tr con
ln, qe v ye l cc bin trong ca b iu khin dy, r l tn hiu iu khin
t b iu khin dy, v i l tham chiu cho cc v tr b trt van. V dy
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51
Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
phi v khng th o c c, ta s dng mt ch s c on do b quan st
xy dng vc. L l ma trn phn hi trng thi.
Trong
)()(
)())(()(
0)()(
0)()()(
3
2
1
tft
tfdt
dtzzt
txtfPP
txtfPt
nn
Cnntn
rnnSS
rnnS
n
(2.20)
Ta c th tm ra Cnf
dt
d bng cch s dng cng thc (2.17) v (2.8). p
dng cng thc trn hm rng cc h thng nh v c th c xem l cc h
thng bc 1 nh sau:
n n nz t Kz t r t
(2.21)
rn l tn hiu iu khin t b iu khin dy. K c s dng lm mt
tham s thit k trong thit k b iu khin. V an11 l s hng vt tri, cc s
hng bin thin an2 v an3 khng c nhiu vai tr quan trng cho hiu qu ca h
thng. Cc tc dng ca bin thin tham s cho h thng thy lc v vy s c
tnh ton k lng hn ti y.
2.2.2.2 Thit k khng gian ring
Khi kim sot dy phi, mt phng php thit k c kh nng gii
quyt cc h thng a bin s c chn. Kim sot bc 2 tuyn tnh l mt
trong nhng phng php tt nht kim sot h thng kiu ny. Mt kh
khn cho cho kim sot bc 2 tuyn tnh l vic chn mt ma trn khi lng
cho cc trng thi v u vo. Vn ny c th c gii quyt bng phng
php khng gian ring, c m t trong [15]. S dng phng php khng gian
ring, cc vn thit k ch cn l vic chn 2 tham s: thi gian phn hi ca
h thng vng kn v phn ly ca b kim sot dy 2 cnh my cn.
Khi s dng thit k khng gian ring ta c kh nng qui cc gi tr tim
cn cho cc gi tr ring v vect ring vng kn s dng thit k bc 2 tuyn
tnh (LQ), xem[15]. Bng cch s dng iu ny, mt cch tng i ta c th
tch iu khin dy ra lm 2 phn: cnh pha bc v nam ca my cn. iu
ny c ngha l ta c th kim sot dy hai bn c lp.
chun b cho thit k khng gian ring ta m rng trng thi mu cho gi
cn (2.13) vi cc kt lun t cc h thng nh v tuyn tnh ha phn hi
(2.21) v 2 trng thi nguyn i. Cc trng thi nguyn xc nh nh sau :
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
0
( ) ( )r c
t
i t v v t dt (2.22)
Cc trng thi ny c to ra m bo sai s tnh bng 0. (2.22),vr
l tham chiu dy cho dy cnh
( ) ( ) ( )0 0
1 1 1( ) 0 ( ) ( ) ( ) ( )
2 2 20 0 0
( ) ( ) ( )
C CC C
Z ch ch
i
cy t y t y tA B
z t C KI z t I r t A z t B r t
Ci t i t i t
(2.23)
Trong 0 0 ; 0 ;T
z i n sC C r r r l u ra ca phn hi trng
thi. Do cui cng ta c 1 phng trnh bc 8, vi 2 u vo v 2 u ra.
Trong thit k ny ngi ta ch nh 2 vect ring hu hn v 6 vec t
ring v hn. Ta quy gi tr cho cc vec t v hn sao cho c th tch ring
dy tng ng ca 2 cnh my cn. Bng cch chn cc vec t hu hn ta t
c iu ny 11 2 0 0 0T
v v .
Chn cc vec t v hn nh c hng dn trong:
3 4
5 6
27 8
v v Bch
v v A Bch ch
v v A Bch ch
(2.24)
Bng cch ny ta c th chc chn cc trng thi cn li ca 2 u ra
(2.23) c cng hng s thi gian v cc ch ny chy dn n v cc theo
kiu Butterworth vi cc vec t ring [v1 v2 v3 v4 v5 v6].
Cc vect vng kn hu hn v1 v v2 c tnh cht
chchf BAIspanvv1
21 )(
Trong f l gi tr mong mun cho cc gi tr ring hu hn vng kn. Ta
c
1
2
1
)(0
0)(
pA
p
p
fc
fc
(2.25)
Trong
2 4
1 1 1 1
2 4
2 2 2 2
( )
( )
c m m
c m m
p p Ap a p EI a
p p Ap a p EI a
(2.26)
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
Ta t c vec t ring 1 * * *T
v s dng (2.13), (2.16) v
(2.18) ta c, cho gi tr tim cn v1 v v2, phn ng xung lc vng kn ca dy
phi ti cnh tha mn
t
etvf
c
10
01)( (2.27)
iu ny c ngha rng phn hi vng kn do cc ch hu hn
c tch ly hon ton. Lut kim sot c thit k c th m bo rng cc
ch c gii hn s chim phn ln v phn hi ca cc ch khng c gii
hn s khng c vai tr quan trng trong trng hp ny.
Phn hi trng thi /PBL Tch c th tm c bng cch gii phng trnh
Riccati
/ 0T T Tch ch ch chPA A P H H PB B P (2.28)
Trong l s hng khi lng ca tn hiu iu khin v H tha mn
1
1 2 3 4 5 6 7 8TH B v v v v v v v vch
Cc bin thit k ca b iu khin dy l f, quyt nh hng s thi
gian v nh hng n tch ly ca kim sot dy 2 cnh my cn.
2.2.2.3. Cu trc b iu khin
Khi vn hnh b iu khin dy yc c thay th bng ye v b quan
st c th o c lc cn. Kt qu ca b kim sot c trnh by hnh 2.7,
theo cng thc
1 1
2 2 3 3
1 1
2 2 3 3
10
( )( )
1( )0
( )
( )( ) ( ) ( )
( )( ) ( ) ( )
( )
n nrn
rs
n n n n n
e
s
s s
s s s s
a tx t
x t
a t
z ta t a t Kz t
L y ta t a t Kz t
i t
(2.29)
n1, n2 v n3 c th c tm thy trong (2.20) v cng c mi quan h
tng t cho h thng thy lc pha bc. ye v vc c th c tm thy (2.15)
v (2.16) v i c th c tnh ton t (2.22). Lu rng php tnh ca yc v i
ch bao gm lc f v v tr z. Ta kt lun rng b kim sot dy l mt b
kim sot bc 2 phi tuyn s dng cc bin c sn trong cc h iu khin
dy c.
2.2.3. Kt qu
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
T hnh 2.8 ta thy vic tch ly dy hai cnh c tin hnh rt tt.
Tham s thit k ca tuyn tnh ha phn hi k c s dng cho h thng
thy lc c tuyn tnh ha mt hng s thi gian thch hp v vy trnh c
khuch i qu ln ca ma trn phn hi trng thi L.
* Hn ch : i vi b iu khin a bin, y n gin ha m hnh
ton hc v tuyn tnh ha h thng thy lc nn hn ch ca phng php l vng
n nh b thu nh. Hn na b iu khin ny khng k n nhiu ni v nhiu
ngoi, sai s do lch tm ca cc trc.
2.3. B iu khin H [7]
Mc ch chnh l thit k b iu khin H cho mt h thng cn mng.
Phng php khng gian trng thi hai Riccati c s dng thit k b iu
khin H cho c vng trong (vng phn hi lc cn) v vng ngoi (vng o dy
phi cn). trnh vic truyn lnh ca b iu khin vng ngoi, mt phng
php gim mu c s dng sau khi thit k vng trong c hon thnh.
2.3.1. K hiu
Cc k hiu sau s c s dng trong mc ny. Cho mt ma trn p rM C ,
M* ch chuyn v ghp cp, M ch gi tr n ln nht, v (M) ch bn knh
dy vcn (ng k lin) v vcs (ng t)
V tr con ln zcn (ng k lin) v zcs (ng t)
Hnh 2.8. Phn hi vi thay i u vo ti 1 cnh
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
quang ph ca n (nu p = r). nh mc ch cc nh mc c lit tiu chun
trn cc vect, G(s) ch ma trn hm truyn.
Php bin i phn s phi tuyn (LFT) ca G v K l
1
1 11 22 22 21, :F G K G G K I G K G
Khng gian H bao gm cc hm b chn c tnh lin tc c pht trin gii tch trn
na mt phng bn phi. nh mc H cho mt ma trn hm truyn G(s) l
: supG G j
Loi b ton b cc vec t v cc kch thc ma trn v gi s rng tt c cc thnh
phn u c kch thc thch hp.
2.3.2. Phng php tiu chun cho bi ton thit k H
H thng c m t theo nh hnh 2.9.
Bi ton iu khin ti u H l phi tm K ch s lm n nh vnh vin
my cn G, sao cho wzT nh nht, trong ,zw lT F G K ch ma trn hm
truyn t w ti z. Tuy nhin, mt vn iu khin km ti u hn H l phi tm
mt K sao cho wzT < y. Bi ton ti u c th c gii quyt bng cch tm mt
cho bi ton iu khin km ti u hn.
G
K
W z
yu
Hnh 2.9. S khi h thng
Ta c cc d kin sau:
a) (A, B2) n nh v (C2, A) l c th tm ra.
b) 12 1 12 0D C D I
c) 1 *
21
21
0BD
D I
d) 2
1 12
A j I B
C D
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
C hng theo ct cho tt c cc w thc
e) 1
2 21
A j I B
C D
C hng theo hng cho tt c cc w thc
Hai phng trnh Riccati c trong bi ton iu khin ti u H l
2 * *1 1 2 2 1 1 0A X X A X B B B B X C C
V * 2 * * *1 1 2 2 1 0AY Y A Y C C C C Y B B
nh l 1: Gi s G tha mn cc gi thit t a) n e). Tn ti mt iu khin
n nh K wzT < y khi v ch khi c 3 iu kin sau:
i. C mt nghim dng n nh na xc nh X
ii. C mt nghim dng n nh na xc nh Y
iii. 2X Y
nh l 1 em n mt phng php khng gian trng thi n gin
thit k mt b iu khin n nh di ti u, sao cho wzT . Cho trc mt
gi tr , ta c th gii hai phng trnh Riccati tm nghim X v Y.
2.3.3. Thit k b iu khin H
iu khin dy ca phi t c ti gi ca my cn. Mi gi cn bao gm mt
v my cha bn trong l hai con ln hnh tr, mt cp con ln ln hn d phng
(BUR)[16,17]. Hnh 2.10 m t mt gi cn 4 tng in hnh
Con ln d phng
Con ln d phng
Cm bin ti trng
Trc thy lc
Con ln ng lc
u ra
V my cn
Cm bin o tia X
u vo
Phi cn
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
Hnh 2.10. Gi cn 4 tng
dy phi c kim sot bng nh v con ln ng lc. V mng ca
phi trn gi con ln s thay i khi c mt s thay i tc cn cng nh bin
thin trong cng v nhit phi u vo, nn iu khin dy phi c kh
nng gi c dy di tc dng ca cc nhiu ny. Vic nh v con ln ng
lc trong qu trnh cn c gi l iu khin o t ng (AGC).
C hai phng php o dy phi. Phng php th nht l phng php
gin tip, s dng lc cn nh ch s o c bn cho iu khin v tr con ln. Phi
ch ra rng dy phi l khc nhau vi cc v tr con ln khc nhau v c cc
lch v my cn v bin dng con ln khc nhau. Li th ca iu khin l kh
nng phn hi nhanh chng, kh nng ny rt hiu qu trong vic loi b cc bin
thin dy v cng cho u vo gi cn. Tuy nhin, phng php phn hi
cng c mt nhc im ln l kh nng phn hi vi nhiu lch tm
BUR[16,17] v kt qu l phi sau khi cn s c bin thin di hnh tr trong
dy, c th dn n khng t c cht lng yu cu. Phng php th hai l
phng php trc tip nhng phi c thi gian ngh, s dng gi tr dy phi u
ra gi cn bng mt cm bin o dng tia X t cch xa cc con ln mt khong.
Cch kim sot dy phi s dng cc s liu o c gi l iu khin monitor.
iu khin monitor v iu khin o hp li thnh iu khin o t ng, y chnh
l l qu trnh iu khin phn hi nhiu vng.
2.3.3.1. M hnh h thng cn
M hnh my cn ngui mt gi c v hnh 2.11[18] .
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
Hnh 2.11. M hnh my cn ngui mt gi
Trong hnh 2.11, bin kim sot nh v vng kn con ln thy lc, bin
dy v cng u vo v nhiu lch tm ln lt l Pr(s), Ph(s), v Pe(s).
Mm ch h s cc bin ca my cn, Mm = 1.030 109 N/m, ch s ny ph
thuc vo bin thin v n hi ca my cn c ti.
Ms ch bin dng phi Ms=9.81x108N/m, ch s ny ph thuc vo bin
dng do ca phi c ti.
2.3.3.2. Qu trnh thit k
Thit k iu khin o t ng nhiu vng c chia lm 3 giai on chnh
Giai on 1. Thit k vng trong
Ngi ta s dng phng php iu khin ti u H tiu chun thit k
iu khin o s dng tnh ton v lc cn. Gim cc bin thin v dy v
cng u vo, lch tm v loi b nhiu o lc cn l nhng mc tiu ch yu
ca thit k vng trong. l
min
( )iK s zT
Trong Ki l b iu khin vng trong.
Giai on 2. Gim mu
Trong phng php khng gian trng thi hai Riccati, t nh l 1 ta c
th thy r rng bc ca b iu khin bng vi bc ca my cn G(s), m trong
c c bc ca hm trng s. Do , cn thit phi tin hnh gim mu trnh
truyn lnh ca b kim sot vng ngoi khi thit k vng trong c hon
Nhiu lch tm Pe
iu khin nh v thy lc Pr
Thc o cng u vo
Ph
Mm Lc cn
Nhiu o
Khuych i
L xo my
Thc
n
u
wx
Ms-1
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Ch-ng 2. M hnh ton hc v cu trc ca cc b iu khin trong h thng cn
thp tm
thnh[19,20].