He Dieu Khien Phan Tan

7/31/2019 He Dieu Khien Phan Tan

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H THNGIU KHN PHN TN

Lecture Notes

Distributed Control Systems

TS. Hong Minh Sn

B MN IU KHIN T NG, KHOA IN

I HC BCH KHOA HNI


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4.1.1 H thng thi gian thc 284.1.2 X l thi gian thc 284.1.3 H iu hnh thi gian thc 29

MC LC1 NHP MN 1

1.1 Phm vi cp 11.2 Ni dung chng trnh 11.3 Yu cu kin thc cs 21.4 Tng quan cc gii php iu khin 2

1.4.1 c trng cc lnh vc ng dng iu khin 21.4.2 Cc h thng iu khin cng nghip 31.4.3 H iu khin phn tn 3

2 CU TRC CC H THNG IU KHIN V GIM ST 52.1 Cu trc v cc thnh phn c bn 52.2 M hnh phn cp 6

2.2.1 Cp chp hnh 72.2.2 Cp iu khin 72.2.3 Cp iu khin gim st 8

2.3 Cu trc iu khin 82.3.1 iu khin tp trung 82.3.2 iu khin tp trung vi vo/ra phn tn 92.3.3 iu khinphn tn 102.3.4 iu khinphn tn vi vo/ra phn tn 11

3 CC THNH PHN CA MT H IU KHIN PHN TN 13

3.1 Cu hnh c bn 133.1.1 Trm iu khin cc b 143.1.2 Bus trng v cc trm vo/ra t xa 153.1.3 Trm vn hnh 173.1.4 Trm k thu t v cc cng c pht trin 183.1.5 Bus h thng 19

3.2 Phn loi 213.2.1 Cc h DCS truyn thng 213.2.2 Cc h DCS trn nn PLC 213.2.3 Cc h DCS trn nn PC 25

3.3 Cc vn k thut 264 X L THI GIAN THC V X L PHN TN 28

4.1 Mt s khi nim c bn 28


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4.1.4 X lphn tn 31

4.2 Cc kin trc x l phn tn 314.3 C ch giao tip 324.4 ng b ha trong x lphn tn 34

4.4.1 ng b ha cc tn hiu vo/ra 344.4.2 ng b ha thi gian 34

5 CNG NGH I TNG TRONG IU KHIN PHN TN 365.1 Lp trnh hng i tng 365.2 Phn tch v thit k hng i tng 36

5.2.1 Ngn ng m hnh ha thng nht UML 385.2.2 Mu thit k 38

5.2.3 Phn mm khung 395.3 Phn mm thnhphn 39

5.4 i tngphn tn 40

6 KIN TRC I TNG PHN TN 426.1 Yu cu chung 426.2 Cc mu thit k 426.3 Gii thiu chun CORBA 43

6.4 Gii thiu chun COM/DCOM 446.4.1 Giao din 456.4.2 i tng COM 46

6.4.3 Giao tip gia client v object 496.4.4 Ngn ng m t giao din 516.4.5 M hnh i tng thnh phn phn tn DCOM 51

7 CC M HNH NG DNG IU KHIN PHN TN 537.1 IEC-6 1131 53

7.1.1 M hnh phn mm 547.1.2 M hnh giao tip 55

7.2 IEC-6 1499 567.2.1 M hnh h thng 577.2.2 M hnh thitb 587.2.3 M hnh ti nguyn 587.2.4 M hnh ng dng 607.2.5 M hnh khi chc nng 617.2.6 M hnh phn tn 637.2.7 M hnh qun l 637.2.8 M hnh trng thi hot ng 63

8 MT S CHUN GIAO TIP CNG NGHIP 65


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8.1 MMS 65

8.2 IEC-61 131 -5 698.2.1 M hnh giao tip mng 698.2.2 Dch v giao tip 698.2.3 Cc khi chc nng giao tip 70

8.3 OPC 728.3.1 Tng quan v kin trc OPC 728.3.2 OPC Custom Interfac es 758.3.3 OPC Automation Interface 76

8.4 Ngn ng nh du kh m XML 778.4.1 Gii thiu chung 778.4.2 ng dng XML trong phn mm khung iPC 78

9 M T H THNG IU KHIN PHN TN 819.1 Cc phng php m t ha 819.2 Lu P&ID 82

9.2.1 Chun ISA S5.1 829.2.2 Chun ISA S5.3 87

9.3 M hnh ha hng i tng 88

10 LP TRNH IU KHIN PHN TN 8910.1 Lp trnh theo chun IEC 61131-3 89

10.1.1 Kiu d liu 90

10.1.2 T chc chng trnh 9210.1.3 Ngn ng FBD 9510.1.4 Ngn ng ST 96

10.1.5 Ngn ng SFC 9710.2 Lp trnh vi ngn ng bc cao 98

11 CHC NNG IU KHIN GIM ST 99

11.1 Gii thiu chung v cc h iu khin gim st 9911.1.1 Cc thnh phn chc nng cbn 10011.1.2 Cng c phn mm SCADA/HMI 101

11.2 Xy dng cu trc h thng 10411.3 Thit k giao din ngi-my 104

11.3.1 Yu cu chung 10511.3.2 Cc phng php giao tip ngi-my 10511.3.3 Thit k cu trc mn hnh 10511.3.4 Cc nguyn tc thit k 106

12 TNH SN SNG V TIN CY CA CC H KPT 10712.1 t vn 107


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12.2 C ch d phng 107

12.3 C ch an ton 10812.4 C ch khi ng li sau s c 108

12.5 Bo mt 10812.6 Bo tr 108

13 NH GI V LA CHN GII PHP IU KHIN PHN TN 11013.1 nh gi v la chn cc sn phm DCS tch hp trn vn 110

13.1.1 Phm vi chc nng 11013.1.2 Cu trc h thng v cc thit b thnh phn 11013.1.3 Tnh nng m 11013.1.4 Pht trin h thng 111

13.1.5 tin cy v tnh sn sng 11113.1.6 Gi thnh, chi ph 111

13.2 So snh gii php DCS tch hp trn vn vi cc gii php khc

112

14 GII THIU MT S H IU KHIN PHN TN TIU BIU 11314.1 PCS7 ca Siemens 11314.2 Plan tScape ca Honeywe ll 113

14.3 DeltaV ca Fisher Rosermount 11314.4 Centum CS1000/CS3000 ca Yokogawa 11314.5 AdvantOCS ca ABB 113

15 MT S HNG NGHIN CU V NG DNG 11415.1 Tr tu nhn to phn tn 11415.2 iu khin v gim st cc h thng giao thng 115

15.2.1 t vn 11515.2.2 M hnh h thng iu khin n tn hiu giao thng bng cngngh Agent 116

15.3 iu khin v gim st cc h thng sn xut v cung cp in 117

TI LIU THAM KHO 119


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DANH MC HNH V

Hnh 1-1: Lch s pht trin cc gii php iu khin................................ 3

Hnh 2-1: Cc thnh phn c bn ca mt h thng iu khin v gim st

5

Hnh 2-2: M hnh phn cp chc nng ca mt h thng iu khin vgim st7

Hnh 2-3: Cu trc iu khin tp trung vi vo/ra tp trun g..................... 9

Hnh 2-4: Cu trc iu khin tp trung vi vo/ra phn tn ................... 10

Hnh 2-5: Cu trc iu khin phn tn vi vo/ra tp trung ................... 11

Hnh 2-6: Cu trc iu khin phn tn vi vo/ra phn tn.................... 12Hnh 3-1: Cu hnh c bn mt h iu khin phn tn........................... 13

Hnh 3-2: M s hnh nh t iu khin DCS .......................................... 16

Hnh 3-3: Cc phng php b tr trm vn hnh.................................... 18

Hnh 3-4: Cu hnh tiu biu mt h iu khin phn tn hin i .......... 20

Hnh 3-5: Cc thnh phn chc nng chnh ca mt PLC ........................ 24

Hnh 5-1: M hnh ha mt h thng iu khin s dng UML................ 38

Hnh 6-1: Cc mu thit k giao tip gia client v i tng server ........ 43

Hnh 6-2: Cu trc m hnh CORBA........................................................ 44

Hnh 6-3: M hnh mt i tng COM.................................................... 46

Hnh 6-4: S thc thi con tr giao din.................................................... 47

Hnh 6-5: Giao tip gia i tng v kh ch hng.................................... 49

Hnh 6-6: Giao tip gia hai i tng ..................................................... 50

Hnh 6-7: Giao tip gia i tng v khch hng trn cng qu trnh .... 50

Hnh 6-8: Giao tip gia i tng v khch hng trn hai qu trnh khcnhau 51

Hnh 6-9: Giao tip gia i tng v khch hng trn hai my khc nhau

vi DCOM ............................................................................................. 52

Hnh 7-1: M hnh phn mm theo IEC 61131-3 ..................................... 54

Hnh 7-2: Giao tip bn trong chng trnh ............................................. 55Hnh 7-3: Giao tip gia cc chng trnh trong cng mt cu hnh bng

bin ton cc ........................................................................................ 55

Hnh 7-4: Giao tip qua khi chc nng .................................................. 56

Hnh 7-5: Giao tip qua ng dn truy cp ............................................ 56


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Hnh 7-6: M hnh h thng theo IEC 61499 ........................................... 57

Hnh 7-7: M hnh thit b theo IEC 61499 (v d thit b 2 trong Hnh 7-6.58

Hnh 7-8: M hnh ti nguyn .................................................................. 59

Hnh 7-9: M hnh ng dng.................................................................... 60

Hnh 7-10: M hnh khi chc nng .......................................................... 61

Hnh 8.1: M hnh giao tip mng theo IEC 61131-5 ............................... 69

Hnh 8.2: Kin trc slc ca OPC ....................................................... 73

Hnh 8.3: Kin trc Client/Se rver trong OPC............................................ 74

Hnh 8.4: OPC Custom Interfac es............................................................ 75

Hnh 8.5: M hnh pht trin iPC ............................................................ 78Hnh 9.1: Lu chi tit mt vng iu khin p sut (bn tri) v lu

n gin ha (bn phi) ........................................................................ 86

Hnh 10-1: Minh ha mt s ngn ng lp trnh PLC................................. 89

Hnh 10-2: Khai bo v s dng mt hm .............................................. 93

Hnh 10-3: Khai bo hm np chng v hm thng thng .................... 94

Hnh 10-4: Khai bo v s dng mt khi chc nng ............................. 94

Hnh 10-5: Mt v d SFC n gin ........................................................... 98

Hnh 11-1: Cc thnh phn phn mm trong mt h SCADA................... 101


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1 NHP MN

1.1 Phm vi cp

Phm vi cp ca mn H thngiu khin phn tn l cc h thng tng ho hin i c cu trc phn tn trong cng nghip cng nh trongnhiu lnh vc khc. Mn hc c xy dng trn c sng dng cc tin bmi nht ca k thut iu khin, k thut truyn thng cng nghip, cngngh phn mm vo trong cc h thng iu khin v gim st.

Mc ch ca mn hc cho sinh vin lm quen vi cu trc v cc thit b

phn cng cng nh cc thnh phn phn mm ca cc h thng iu khinv gim st hin i, nm c cc nguyn tc v phng php c bn chohng gii quyt nhng bi ton thng c t ra trong thc t nh thit

k cu trc h thng, tch hp h thng, a vo vn hnh v chn on hthng. Bn cnh , mn hc a ra cc hng nghin cu l thuyt v ngdng mi, to c scho cc sinh vin mun tip tc hc v nghin cu ccbc sau i hc.

1.2 Ni dung chng trnh

Ni dung bi ging bao gm cc ch chnh sau:

Cu trc cc h thng iu khin v gim st: M hnh phn cp,cc thnh phn chc nng c bn, m t h thng

C stin hc: X l phn tn, cng ngh hng i tng, phn mm

thnh phn Cc h thng iu khin phn tn truyn thng (DCS): Cu trc

h thng, cc thnh phn h thng, phng php pht trin h thng, giithiu mt s h DCS tiu biu.

Cc h thng iu khin phn tn trn nn PLC (PLC-based DCS) Cc h thng iu khin phn tn trn nn PC (PC-based DCS) H thng iu khin gim st v thu thp d liu (SCADA): Cu trc h

thng, cng c phn mm, thit k giao din ngi-my

Ccchun

giao tip cngngh ip:

MMS, OPC,XML

Cc hng nghin cu v ng dng.

2002, Hong Minh Sn 1


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1.3 Yu cu kin thc c s

Phn ln ni dung cc bi ging mang tnh cht tng hp, lin mn, ginhcho sinh vin nm cui. Bn cnh cc mn c s chuyn ngnh, yu cu hcvin phi nm vng kin thc c bn trong cc mn hc sau: iu khin s Mng truyn thng cng nghi p K thut lp trnh C++ (hng i tng)

Bn cnh bi ging, phn ln cc ti liu tham kho cho mn hc c tphp trong mt a CD cc hc vin c th t sao chp.

1.4 Tng quan cc gii php iukhi n

1.4.1 c trng cc lnh vc ng dng iu khi n

Khi xy dng mt gii php iu khin, ta phi quan tm ti qui m vc th ca lnh vc ng dng. Mt vi lnh vc ng dng tiu biu v cc giiphp iu khin c th tng ng c tm tt di y. iu khin cc thit b v my mc n l (cng nghip v gia dng):

Cc my mc, thit b c sn xut hng lot, v vy yu cu u tcho gii php iu khin phi tht tit kim (chng trnh nh, tn tb nh). Cc bi ton iu khin c th rt khc nhau, t iu khinlogic ti iu khin phn hi, iu khin chuyn ng, iu khinm, Cc gii php iu khin tiu biu l iu khin nhng (P, C),CNC, PLC,...

T ng ha cng ngh ip, c chia ra hai lnh vc: Cng nghip ch bin, khai thc: Cc bi ton iu khin tiu biu

l iu khin qu trnh (process control ), iu khin trnh t(sequence control ), bn cnh iu khin logic. Cc thit b c dngph bin l PLC, DCS, (I)PC, Compact Digital Controllers. Cng nghip ch to, lp rp: Cc bi ton iu khin tiu biu l iu

khin logic, iu khin chuyn ng, iu khin s kin ri rc. Ccthit b c dng ch yu l PLC, CNC, PC. Nay cc h DCS cng tm

c mt s ng dng trong lnh vc ny. iu khin cc h thng giao thng, vn ti: c th l cc bi ton

iu khin logic, iu khin s kin ri rc. Cc thit b c dng l

PLC, DCS, PC, P, C,...



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iu khin cc h thng phn phi nng lng (du kh, gas, in):

Kt hp gia cc bi ton iu khin qu trnh vi iu khin s kinri rc, iu khin logic, s dng PLC, DCS, IPC,...

T ng ha ta nh: Rle, PLC, p, C,... iu khin v gim st cc h thng quc phng: IPC, P, C, DSP

v cc thit b c chng khc. iu khin v gim st cc h thng thy li, mi trng: PLC, IPC, ... ...

1.4.2 Cc h thng iu khin cng nghi p

Chng trnh hc t trng tm vo cc gii php iu khin cng nghi p,chia lm hai lnh vc ng dng cbn: Cng nghip ch bin, khai thc (Process Industry): Du kh, ha du,

ha m phm, dc phm, xi mng, giy, ... Cng nghip ch to, lp rp (Manufactoring Industry): Cng

ngh ip t, my cng c, cng nghip in t, vi in t, thit b dndng,...

IU KHIN LIN TC/TRNH T IU KHIN RI RC/LOGIC

Cc b iu khin c

B iu khin PID khnn

(1920-1930)

B iu khin PID in t(1940-1950)

Direct Digital Controller DDC(K tp trung, 1965-1975)

Cc h iu khinc

Rlein

ProgrammableLogicController(PLC), 1970

Compact DigitalController DCS PLC-based DCS

PC-based DCS

DISTRIBUTED CONTROL SYSTEMS

Hnh 1-1: Lch spht trin cc gii php iu khi n

1.4.3 H iu khin phn tn

H iu khi n phn tn (Distributed Control System , DCS) l mt khi

nim xut x t cc ngnh cng nghip ch bin, ch cc h thng iu khin



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qu trnh tch hp trn vn ca mt nh sn xut. Ngy nay, khi nim DCS

c hiu vi ngha rng hn nhi u, ch tt c cc h thng iu khin tchhp ton din c cu trc iu khin phn tn. V th, ng dng cc h iukhin phn tn khng nhng ph bin trong cng nghip ch bin, m cnlan rng sang cc lnh vc khc. Cc h DCS ngy nay chim khong 12% th

phn trong c th trng t ng ha.

Kin trc v cc gii php iu khin cng ngh ip cng c p dng rngri trong cc lnh vc ng dng khc. V th, cc ni dung cp trongchng trnh cng mang tnh tng qut, c th p dng ngoi cc ng dngcng nghip. V d, cc h thng iu khin v gim st h thng giao thng,vn ti (ng b, ng st hoc hng khng) hoc h thng phn phi nng

lng cng u l cc lnh vc thch hp ng dng phng php iu khinphn tn.



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NIThit b iu khin t ng

NI I/O NIN

2 CU TRC CC H THNG IU KHINV GIM ST

2.1 Cu trc v cc thnh phn cbn

Cc thnh phn c bn ca mt h thng iu khin v gim st qu trnhc minh ha trn Hnh 2-1. Cc cm bin v c cu chp hnh ng vai trl giao din gia cc thit b iu khin vi qu trnh k thut. Trong khi ,h thng iu khin gim st ng vai tr giao din gia ngi vn hnh vmy. Cc thit b c th c ghp ni trc tip im- im, hoc thng qua

mng tru yn thng.

H thng iu khin gim st

NI

ni trctip

NI

I/O

ni qua mng

NICm bin v chp hnh

NI networkinterface(giao din mng)

I/O input/output (vo/ra)

Qu trnh k thut

Hnh 2-1: Cc thnh phn c bn ca mth thngiu khin

v gim st

Ty theo loi cm bin, tn hiu ca chng a ra c th l tn hiu nh phn, tn hiu s hay tn hiu tng t theo cc chun in hc thng dngkhc nhau (1..10V, 0..5V, 4..20mA, 0..20mA, v.v...). Trc khi c th x ltrong my tnh s, cc tn hiu o cn c chuyn i, thch ng vi chu ngiao din vo/ra ca my tnh. Bn cnh , ta cng cn cc bin php cch lyin hc trnh s nh hng xu ln nhau gia cc thit b. chnh l

cc chc nng ca cc module vo/ra (I/O).



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Tm li, mt h thng iu khin v gim st bao gm cc thnh phn

chc nng chnh sau y: Giao din qu trnh: Cc cm bin v c cu chp hnh, ghp ni

vo/ra, chuyn i tn hiu. Thit b iu khin t ng: Cc thit b iu khin nh cc b

iu khin chuyn dng, b iu khin kh trnh PLC (programmablelogic controller ), thit b iu chnh s n l (compact digitalcontroller ) v my tnh c nhn cng vi cc phn mm iu khin tngng.

H thng iu khin gim st: Cc thit b v phn mm giao din

ngi my, cc trm k thut, cc trm vn hnh, gim st v iukhin cao cp.

H thng truyn thng: Ghp ni im- im, bus cm bin/c hp hnh,bus trng, bus h thng. H thng bo v, c ch thc hin chc nng an ton.

2.2 M hnh phn cp

Cng nhng cp di th cc chc nng cng mang tnh cht c bn hnv i hi yu cu cao hn v nhanh nhy, thi gian phn ng. Mt chc

nng cp trn c thc hin da trn cc chc nng cp di, tuy khngi hi thi gian phn ng nhanh nh cp di, nhng ngc li lngthng tin cn trao i v x l li ln hn nhi u. Thng thng, ngi ta ch

coi ba cp di thuc phm vi ca mt h thng iu khin v gim st. Tuynhin, biu th hai cp trn cng (qun l cng ty v iu hnh sn xut) trngip ta hiu thm mt m hnh l tng cho cu trc chc nng tng th cho

cc cng ty sn xut cng nghi p.



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Tnh ton gi thnh, li sutthng k s liu sn xut, kinh doanh,x l n t hng, k hoch ti nguyn

nh gi kt qu, lp k hoch snxut, bo dng my mc,tnh ton ti u ho sn xut

QLcng ty

iuhnhsn xut

Gim st, vn hnh,iu khin cao cp,Lp bo co

iu khin, iu chnh,bo v, an tonghi chp tng trnh

o lng, truyn ng,chuyn i tn hiu

iu khin gimst

iukhin

Chp hnh

Qu trnh k thut

Cpiukhin qutrnh

Cp trng

Hnh 2-2: M hnh phn cp chc nng ca mt h thng iu

khin v gim st

2.2.1 Cp chp hnh

Cc chc nng chnh ca cp chp hnh l o lng, truyn ng vchuyn i tn hiu trong trng hp cn thit. Thc t, a s cc thit bcm bin (senso r) hay c cu chp hnh (actuator ) cng c phn iu khinring cho vic thc hin o lng/tru yn ng c chnh xc v nhanh nhy.

Cc thit b thng minh1 cng c th m nhn vic x l th thng tin, trckhi a ln cp iu khin.

2.2.2 Cp iu khi n

Nhim v chnh ca cp iu khi n l nhn thng tin t cc cm bin, xl cc thng tin theo mt thut ton nht nh v truyn t li kt quxung cc c cu chp hnh. Khi cn iu khin th cng, nhim v cngi ng my trc tip m nhim qua vic theo di cc cng c o lng,s dng kin thc v kinh ngh im thc hin nhng thao tc cn thit nh

n nt ng/m van, iu chnh cn gt, nm xoay v.v... Trong mt h thng

1 Mt thit b c gi l thng minh, khi n c kh nng x l thng tin. Thc t, mi

thit b thng minh phi c t nht mt b vi x l ring.



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iu khin t ng hin i, vic thc hin th cng nhng nhim v c

thay th bng my tnh.

2.2.3 Cp iu khin gim st

Cp iu khin gim st c chc nng gim st v vn hnh mt qu trnhk thut. Khi a s cc chc nng nh o lng, iu khin, iu chnh, boton h thng c cc cp c sthc hin, th nhim v ca cp iu khingim st l h tr ngi s dng trong vic ci t ng dng, thao tc, theodi, gim st vn hnh v x l nhng tnh hung bt thng. Ngoi ra, trongmt s trng hp, cp ny cn thc hin cc bi ton iu khin cao cpnh iu khin phi hp, iu khin trnh t v iu khin theo cng thc (v

d trong ch bin dc phm, ho cht). Khc vi cc cp di, vic thchin cc chc nng cp iu khin gim st thng khng i hi phngtin, thit b phn cng c bit ngoi cc my tnh thng thng (my tnh cnhn, my trm, my ch, termimal,...).

Nh ta s thy, phn cp chc nng nh trn s tin li cho vic thit kh thng v la chn thit b. Trong thc t ng dng, s phn cp chc nngc th khc mt cht so vi trnh by y, ty thuc vo mc t ngho v cu trc h thng c th. Trong nhng trng hp ng dng n ginnh iu khin trang thit b dn dng (my git, my lnh, iu ha m,...), s phn chia nhiu cp c th hon ton khng cn thit. Ngc li,

trong t ng ha mt nh my ln hin i nh in nguyn t, sn xut ximng, lc du, ta c th chia nh hn na cc cp chc nng tin theo di.

2.3 Cu trc iu khi n

Bin th ca cu trc c bn trn Hnh 2-1 tm thy trong cc gii phpthc t kh c nhau s phn b chc nng iu khin cng nh s phn bv tr cc my tnh qu trnh v ph kin c la chn. Cn c vo , ta cth phn bit gia cu trc iu khin tp trung v cu trc iu khin phntn, cu trc vo/ra tp trung v cu trc vo/ra phn tn.

2.3.1 iu khin tp trungCu trc tiu biu ca mt h iu khin tp trung (centralized control

system )c minh ha trn Hnh 2-3. Mt my tnh duy nht c dng iu khin ton b qu trnh k thut. My tnh iu khin y (MTK) cth l cc b iu khin s trc tip (DDC), my tnh ln, my tnh c nhnhoc cc thit b iu khin kh trnh. Trong iu khin cng nghip, my



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tnh iu khin tp trung thng thng c t ti phng iu khin trung

tm, cch xa hin trng. Cc thit b cm bin v c cu chp hnh c nitrc tip, im- im vi my tnh iu khin trung tm qua cc cng vo/raca n. Cch b tr vo/ra ti my tnh iu khin nh vy cng c gi l

vo/ra tp trung (central I/O).

Phng iu khin trung tm MTK

I/O

Hin trng

A S A S A S

Phn on 1 Phn on 2 Phn on n

I/O: input/output A: actuator S: sensor

Hnh 2-3: Cu trc iu khin tp trung vi vo/ra tp trung

y l cu trc iu khin tiu biu trong nhng nm 1965-1975. Ngynay, cu trc tp trung trn y thng thch hp cho cc ng dng t ng

ha qui m va v nh, iu khin cc loi my mc v thit b bi s ngin, d thc hin v gi thnh mt ln cho my tnh iu khin. im ngch y l s tp trung ton b tr tu, tc chc nng x l thng tintrong mt thit b iu khin duy nht. Tuy nhin, cu trc ny bc l nhnghn ch sau: Cng vic ni dy phc tp, gi thnh cao Vic m rng h thng gp kh khn tin cy km.

2.3.2 iu khin tp trung vi vo/ra phn tn

Cu trc vo/ra tp trung vi cch ghp ni im- im th hin mt nhcim c bn l s lng ln cc cp ni, dn n gi thnh cao cho dy dnv cng thit k, lp t. Mt hn ch khc na l phng php truyn dntn hiu thng thng gia cc thit b trng v thit b iu khin d chunh hng ca nhiu, gy ra sai s ln. Vn ny c khc phc bngphng php dng bus trng nh nu trong phn trc. Hnh 2-4 minhha mt cu hnh mng n gin. y cc module vo/ra c y xung



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cp trng gn k vi cc cm bin v c cu chp hnh, v vy c gi l

cc vo/ra phn tn (Distributed I/O) hoc vo/ra t xa (Remote I/O). Mtcch ghp ni khc l s dng cc cm bin v c cu chp hnh thng minh(mu xm trn hnh v), c kh nng ni mng trc tip khng cn thng quacc module vo/ra. Bn cnh kh nng x l giao thc truyn thng, cc thitb ny cn m nhim mt s chc nng x l ti ch nh lc nhiu, chnhnh thang o, t t ch , im lm vic, chn on trng thi,v.v... Trongnhiu trng hp, cc thit b c th m nhim c nhim v iu khin n

gin.

bus trng

MTKPhng K trung tm

Hin trng

I/O I/O I/O S A S A

S A S A S A

Hnh 2-4: Cu trc iu khi n tp trung vi vo/ra phn tn

S dng bus trng v cu trc vo/ra phn tn mang li cc u im sau: Tit kim dy dn v cng i dy, ni dy Gim kch thc hp iu khin Tng linh hot h thng nh s dng cc thit b c giao din

chu n v kh nng ghp ni n gin Thit k v bo tr d dng nh cu trc n gin Kh nng chn on tt hn (cc thit b hng c pht hin d dng) Tng tin cy ca ton h thng.

2.3.3 iu khin phn tn

Trong a s cc ng dng c qui m va v ln, phn tn l tnh cht c

ha ca h thng. Mt dy chuyn sn xut thng c phn chia thnhnhiu phn on, c th c phn b ti nhiu v tr cch xa nhau. khcphc s ph thuc vo mt my tnh trung tm trong cu trc tp trung vtng tnh linh hot ca h thng, ta c th iu khin mi phn on bng

mt hoc mt s my tnh cc b, nh Hnh 2-5 minh ha.



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MTGSPHNG IU KHIN

TRUNG TM MTGS

bus hthng

MTK 1 MTK 2 PHNGIUKHIN CC B

MTK n

A S A S A S

HINTRNG


Hnh 2-5: Cu trc iu khin phn tn vi vo/ra tp trung

Cc my tnh iu khin cc b thng c t ri rc ti cc phng iukhin/phng in ca tng phn on, phn xng, v tr khng xa vi qutrnh k thut. Cc phn on c lin h tng tc vi nhau, v vy iu

khin qu trnh tng hp cn c s iu khin phi hp gia cc my tnhiu khin. Trong phn ln cc trng hp, cc my tnh iu khin c nimng vi nhau v vi mt hoc nhiu my tnh gim st (MTGS) trung tmqua bus h thng. Gii php ny dn n cc h thng c cu trc iu khinphn tn, hay c gi l cc h iu khi n phn tn (HKPT).

u th ca cu trc iu khin phn tn khng ch dng li linh hotcao hn so vi cu trc tp trung. Hiu nng cng nh tin cy tng th cah thng c nng cao nh s phn tn chc nng xung cc cp di. Vicphn tn chc nng x l thng tin v phi hp iu khin c s gim st tcc trm vn hnh trung tm m ra cc kh nng ng dng mi, tch hp

trn vn trong h thng nh lp trnh cao cp, iu khin trnh t, iu khintheo cng thc v ghp ni vi cp iu hnh sn xut.

2.3.4 iu khin phn tn vi vo/ra phn tn

Lu rng Hnh 2-5 ch minh ha cch ghp ni im- im gia mt mytnh iu khin vi cc cm bin v c cu chp hnh, s dng vo/ra tptrung. Tuy nhin, ta cng c th s dng bus trng thc hin cu trc

vo/ra phn tn nh trn Hnh 2-6. Khi , my tnh iu khin c th t ti



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MTK n

phng iu khin trung tm hoc ti cc phng iu khin cc b, ty theo

qui m ca h thng v kh nng ko di ca bus trng.

Gii php s dng cc h iu khin phn tn vi cu trc vo/ra phn tnv cc thit b trng thng minh chnh l xu hng trong xy dng cc hthng iu khin v gim st hin i. Bn cnh tin cy cao, tnh nng mv linh hot cao th yu t kinh t cng ng vai tr quan trng. Vicphntn chc nng x l thng tin, chc nng iu khin theo b rng cng nhtheo chiu su l tin cho kin trc tr tu phn tn (distributed

intelligence ) trong tng lai.

MTGS MTGS

bus hthng

PHNG IU KHINTRUNG TM

MTK 1

bus trng

MTK2

bus trng

PHNGIUKHIN CC B bus trng

I/O I/O I/O

S A S A S AHIN TRNG


Hnh 2-6: Cu trc iu khi n phn tn vi vo/ra phn tn



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My tnhphng th

3 CC THNH PHN CA MT H IUKHIN PHN TN

3.1 Cu hnh cbn

Cu hnh c bn mt h iu khin phn tn c minh ha trn Hnh3-1, bao gm cc thnh phn sau: Cc trm iu khin cc b (local control station, LCS), i khi

cn c gi l cc khi iu khin cc b (local control unit, LCU)hoc cc trm qu trnh (process station, PS).

Cc trm vn hnh (operator station, OS) Trm k thut (engineering station, ES) v cc cng c pht tri n H thng truyn thng (field bus , system bus).

PC

Factory LAN

OperatorStation

OperatorStation

EngineeringStation

System bus

Local ControlStation

Local ControlStation

RemoteI/O Station

PROCESS

Hnh 3-1: Cu hnh c bn mth iu khinphn tn



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y l cu hnh ti thiu, cc cu hnh c th c th cha cc thnh phn

khc nh trm vo/ra t xa (remote I/O station ), cc b iu khin chuyndng,...

3.1.1 Trm iu khin cc b

Thng thng, cc trm iu khin cc b c xy dng theo cu trcmodule. Cc thnh phn chnh bao gm: B cung cp ngun, thng thng c d phng Khi x l trung tm (CPU), c th la chn loi c d phng Giao din vi bus h thng, thng thng cng c d phng Giao din vibus trng nu s dng cu trc vo/ra phn tn Cc module vo/ra s cng nh tng t, c bit l cc module

vo/ra an ton chy n

Trong cu trc vo/ra tp trung, cc module vo/ra c ni vi CPUthng qua bus ni b ng sau gi (backplane-bus ). Chnh v vy, ccmodule ny cng phi do nh sn xut cung cp km theo CPU.

Trong cc h thng iu khin qu trnh, mt trm iu khin cc b cngthng c ci t giao din HART v cc module ghp ni ph kin khc.Cc thit b ny c lp t trong t iu khin cng vi cc linh kin h tr

khc nh hng kp u dy, cc b chuyn i tn hiu (transducers ), cckhi u cui (terminal blocka ),... Cc t iu khin thng c t trong

phng iu khin/phng in bn cnh phng iu khin trung tm hocri rc gn khu vc hin trng.

Cc chc nng do trm iu khin cc b m nhimbao gm: iu khin qu trnh (process control ): iu khin cc mch vng

kn (nhit , p sut, lu lng, pH, m c,...). Hu ht ccmch vng n c iu khin trn c slut PID, gii quyt bi toniu khin iu chnh, iu khin t l, iu khin tng. Cc h thnghin i cho php iu khin m, iu khin da m hnh (model-based control ), iu khin thch nghi, ...

iu khin trnh t (sequential control, sequence control) iu khin logic

Thc hin cc cng thc (recipe control ). t cc tn hiu u ra v trng thi an ton trong trng hp c s c

h thng Lu tr tm thi cc tn hiu qu trnh trong trng hp mt lin

lc vi trm vn hnh



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Nhn bit cc trng hp vt ngng gi tr v to cc thng bo bo

ng.

Chnh v y l thnh phn quan trng nht trong h thng, i a s cctrm iu khin cc b c tnh nng kim tra v sa li (error checking andcorrecting , ECC), cng nh cho php la chn cu hnh d phng. Mt iuquan trng l mt trm iu khin cc b phi c kh nng m bo tip tcthc hin cc chc nng ni trn trong trng hp trm vn hnh hoc ngtruyn bus h thng c s c.

Cc my tnh iu khin c th l my tnh c chng ca nh cung cp(vendor-specific controller ), PLC hoc my tnh c nhn cng nghip. Datrn c sny c th phn loi cc h thng iu khin phn tn c mt hin

nay trn th trng thnh cc h cc h truyn thng (sau y gi l DCStruyn thng), cc h trn nn PLC (PLC-based DCS) v cc h trn nn PC(PC-based DCS).

Bt k chng loi thit b no c s dng, cc yu cu quan trng nhtv mt k thut c t ra cho mt trm iu khin cc b l: Tnh nng thi thc tin cy v tnh sn sng Lp trnh thun tin, cho php s dng/ci t cc thut ton cao cp Kh nng iu khin lai (lin tc, trnh t v logic).

3.1.2 Bus trng v cc trm vo/ra t xaKhi s dng cu trc vo/ra phn tn, cc trm iu khin cc b s c

b sung cc module giao din bus ni vi cc trm vo/ra t xa (remoteI/Ostation ) v mt s thit b trng thng minh. Cc yu cu chung t ravi bus trng l tnh nng thi gian thc, mc n gin v gi thnhthp. Bn cnh , i vi mi trng d chy n cn cc yu cu k thut

c bit khc v chun truyn dn, tnh nng in hc ca cc linh kinmng, cp truyn,... Cc loi bus trng c h tr mnh nht l Profibus-DP, Foundation Fieldbus, DeviceNet v AS-I. Trong mi trng i hi anton chy n th Profibus-PA v Foundation Fieldbus H1 l hai h c sdng ph bin nht.

Mt trm vo/ra t xa thc cht c cu trc khng khc lm so vi mttrm iu khin cc b, duy ch thiu khi x l trung tm cho chc nngiu khin. Thng thng, cc trm vo/ra t xa c t rt gn vi qu

trnh k thut, v th tit kim nhiu cp truyn v n gin ha cu trc h



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thng. Trm vo/ra t xa cng c th t cng v tr vi trm iu khin cc

b, tuy nhin nh vy khng li dng c u im ca cu trc ny.

Khc vi cu trc vo/ra tp trung, cu trc vo/ra phn tn cho php sdng cc trm vo/ra t xa ca cc nh cung cp khc vi iu kin c h trloi bus trng qui nh. Tuy nhin, c th khai thc ti a kh nng cccng c phn mm tch hp v m bo tng thch hon ton gia cc thnhphn trong mt h DCS, vic dng trn sn phm ca mt hng vn l giiphp an ton nht.

Bn cnh phng php ghp ni thit b iu khin vi qu trnh k thut

thng qua cc module vo/ra, ta c th s dng cc cm bin hoc c cuchp hnh c giao din bus trng. Qua c th n gin ha cu trc h

thng hn na, tit kim tit kim ch trong t iu khin v nng cao tnhnng thi gian thc ca h thng do tn dng c kh nng x l thng tinca cc thit b trng.

Trn Hnh 3-4 l hnh nh mt s t iu khin DCS. Hnh bn tri l mttrm PCS7 (Siemens) vi b iu khin lp t cng cc module vo/ra phntn. Hnh gia minh ha mt trm vo/ra t xa lp c lp. T iu khinbn phi minh ha trm iu khin cc b DeltaV (Fisher-Rosermount) sdng gii php Foundation Fieldbus (khng cn cc module cc vo/ra).

Hnh 3-2: Ms hnh nh t iu khin DCS



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3.1.3 Trm vn hnh

Trm vn hnh v trm k thut c t ti phng iu khin trung tm.Cc trm vn hnh c th hot ng song song, c lp vi nhau. tin chovic vn hnh h thng, ngi ta thng sp xp mi trm vn hnh tngng vi mt phn on hoc mt phn xng. Tuy nhin, cc phn mm chytrn tt c cc trm hon ton ging nhau, v th trong trng hp cn thi tmi trm u c th thay th chc nng ca cc trm khc.

Cc chc nng tiu biu ca mt trm vn hnh gm c: Hin th cc hnh nh chun (hnh nh tng quan, hnh nh nhm,

hnh nh tng mch vng, hnh nh iu khin trnh t, cc th thigian thc v th qu kh)

Hin th cc hnh nh ha t do (lu cng ngh, cc phm iukhin)

H tr vn hnh h thng qua cc cng c thao tc tiu biu, cc h

thng hng dn ch o v hng dn tr gip To v qun l cc cng thc iu khin (cho iu khin m) X l cc s kin, s c X l, lu tr v qun l d liu Chn on h thng, h trngi vn hnh v bo tr h thng H tr lp bo co t ng

Khc vi cc trm iu khin, hu ht cc h DCS hin i u s dngcc sn phm thng mi thng dng nh my tnh c nhn (cng nghi p)

chy trn nn WindowsNT/2000, hoc cc my tnh trm chy trn nn UNIX.Cng vi cc mn hnh mu ln (thng l 19inch) vi phn gii cao theo di qu trnh sn xut, mt trm vn hnh hin i bao gi cng c ccthit b thao tc chun nh bn phm v chut. Mt trm vn hnh c th btr theo kiu mt ngi s dng (mt hoc nhiu mn hnh), hoc nhiungi s dng vi vi nhiu Terminals (Hnh 3-3).

Cc phn mm trn trm vn hnh bao gi cng i km ng b vi hthng, song thng h tr cc chun phn mm v chun giao tip cngnghip nh TCP/IP, DDE (Dynamic Data Exchange ), OLE (Object Linkingand Embeddin g), ODBC (Open Data Base Connectio n), OPC (OLE for

Process Control ).



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Operator Terminals

EngineeringStation

OperatorStation

Terminalsbus

Systembus

Controller

Hnh 3-3: Cc phng php b tr trm vn hnh

c im tiu biu ca cc trm vn hnh hin i l s dng k thutgiao din ngi-my kiu a ca s vi cc phn t giao din chun. Tuynhin, vic thit k cc mn hnh giao din cng nghip khc vi cc giao dinng dng vn phng, i hi kin thc tng hp v qu trnh cng ngh, mthut cng nghip, tm l hc cng nghip v cng ngh phn mm. Vn ny s c cp chi tit sau.

3.1.4 Trm k thut v cc cng c pht trin

Trm k thut l ni ci t cc cng c pht trin, cho php t cu hnhcho h thng, to v theo di cc chng trnh ng dng iu khin v giaodin ngi my, t cu hnh v tham s ha cc thit b trng. Vic to ngdng iu khin hu ht c thc hin theo phng php khai bo, ttham s v ghp ni cc khi chc nng c sn trong th vin. Cng nh cc

trm vn hnh, thit b s dng thng thng l cc my tnh c nhn (cngnghip) chy trn nn Windows95/98/NT/2000 hoc UNIX.

Mt s c tnh tiu biu ca cc cng c pht trin trn trm k thut l: Cc cng c pht trin c tch hp sn trong h thng Cng vic pht trin (Engineering ) khng yu cu c phn cng DCS

ti ch Cc ngn ng lp trnh thng dng l s khi hm (FBD-

Function Block Diagram , hoc CFC- Continuous Function Char t) v biu tin trnh (SFC -Sequential Function Char t), tng t IEC61131-3 FBD() v SFC

Mt d n c th do nhiu ngi cng phi hp pht trin song song Giao din vi cc h thng cp trn (CAD/CAM, MES, PPS, ERP,...)



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vic pht trin h thng phn mm c thun li, cc nh sn xut

cung cp cc th vin khi hm chuyn dng. Bn cnh , nhiu nh snxut cng cung cp phn mm m phng ngi pht trin h thng c thto cc u vo/ra m phng, gip cho vic pht trin phn mm c chcchn, an ton hn.

Trong mt s h thng, ngi ta khng phn bit gia trm vn hnh vtrm k thut, m s dng mt bn phm c kha chu yn qua li gia haich vn hnh vpht tri n.

3.1.5 Bus h thng

Bus h thng c chc nng ni mng cc trm iu khin cc b vi nhau

v vi cc trm vn hnh v trm k thut. Trong a s cc h thng ngdng, ngi ta la chn cu hnh c d phng cho bus h thng. Thm na, ci thin tnh nng thi gian thc, nhiu khi mt mng ring bit (c th cc d phng) c s dng ghp ni cc trm iu khin cc b (bus iukhin, control bus ). Gii php mng c th c chng ca ring cng ty, hocda trn mt mng chun quc t. Cc h thng mng c s dng nhi unht l Ethernet, Profibus-FMS v ControlNet.

c im ca vic trao i thng tin qua bus h thng l lu lng thngtin ln, v vy tc ng truyn phi tng i cao. Tnh nng thi gianthc cng l mt yu cu c t ra (nht l i vi bus iu khin), tuy

nhin khng nghim ngt nh vi bus trng. Thi gian phn ng thng chyu cu nm trong phm vi 0,1s tr ln. S lng trm tham gia thngkhng ln v nhu cu trao i d liu khng c t bin ln. V vy i vimng Ethernet, tnh bt nh ca phng php truy nhp bus CSMA/CDthng khng phi l vn gy lo ngh.

Hnh 3-4 minh ha cu hnh tiu biu ca mt h iu khin phn tnhin i. Bn cnh cc thnh phn m t, mt cu hnh tiu biu thngc thm mt s trm server, my tnh phn tch, my in, mt s b iu

khin cc b chuyn dng,...



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ControlStation 1

LDBUS

ControlStation 2

ControlStation n

LAB FactoryServer

OS OS ES SS

SYSTEM BUS

FIE

I/O

S A

I/O

S A

I/O

Controller

S A

Controller

S A

Controller

MotorControlCenter

S

A

I/O

S A S A S A


Hnh 3-4: Cu hnh tiu biu mt h iu khi n phn tn hin

i



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3.2 Phn loi

3.2.1 Cc h DCS truyn thng

Cc h ny s dng cc b iu khin qu trnh c chng theo kin trcring ca nh sn xut. Cc h c thng ng kn, t tun theo cc chungiao tip cng ngh ip, cc b iu khin c s dng cng thng ch lmnhim v iu khin qu trnh, v vy phi s dng kt hp PLC cho cc biton iu khin logic v iu khin trnh t. Cc h mi c tnh nng m tthn, mt s b iu khin lai m nhim c cc chc nng iu khin qutrnh, iu khin trnh t v iu khin logic (hybrid controller ).

h tr cc bi ton iu khin qu trnh din ra ng thi, khi x ltrung tm c ci t mt h iu hnh thi gian thc, a nhim - hoc caring nh sn xut pht trin hoc mt sn phm thng dng nh pSOS,TSOS, VRTX,... Chu k thi gian nh nht thc hin cc mch vng iukhin thng nm trong khong 10-100ms, trong trng hp c bit (v d

cho nh my in) c th ti 1ms.

Mt s sn phm tiu biu cng vi tn trm iu khin cc b c litk di y: AdvantOCS (ABB): Advant Controller, h iu hnh ring Freelance 2000 (ABB): D-PS hc D-FC, h iu hnh pSOS Symphonie (ABB): Melody, h iu hnh pSOS DeltaV (Fisher-Rosermount): Visual Controller, h iu hnh TSOS I/A Series (Foxboro): CP60, h iu hnh VRTX PlantScape (Honeywell): PlantScape Controller, h iu hnh ring Centum CS1000/CS3000 (Yokogawa): PFCx-E, AFS10x/AFS20x,

h iu hnh ORKID

3.2.2 Cc h DCS trn nn PLC

Thi t b iu khin kh trnh (PLC, programmable logic controller ) l mtloi my tnh iu khin chuyn d ng, do nh pht minh ngi M RichardMorley ln u tin a ra tng vo nm 1968. Da trn yu cu k thut

ca General Motors l xy dng mt thit b c kh nng lp trnh mm dothay th cho mch iu khin logic cng, hai cng ty c lp l Allen Bradleyv Bedford Associates (sau ny l Modicon) a ra trnh by cc sn phmu tin. Cc thit b ny ch x l c mt tp lnh logic c bn, 128 imvo/ra (1 bit) v 1kByte b nh. Lc u, ci tn programmable controlle r,vit tt l PC, c s dng rng ri. Trong khi , programmable logic



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controller hay PLC l thng hiu ng k ca cng ty Allen Bradley. Sau ny,

khi my tnh c nhn tr nn ph bin th t vit tt PLC hay c dng hn trnh nhm ln. V vy t y v sau ta s dng khi nim thit b iukhin kh trnh nhng vi t vit tt l PLC.

Vi cu trc ghp ni vo/ra linh hot, nguyn tc lm vic n gin theochu k, kh nng lp trnh v lu tr chng trnh trong b nh khng cncan thip trc tip ti phn cng, PLC nhanh chng thu ht s ch trong

gii chuyn ngnh. Vo thi im cc my tnh iu khin chuyn dng vkhng chuyn dng u c kch c rt ln v gi thnh rt cao, th vic sdng PLC l gii php l tng thay th cc mch logic t hp v tun ttrong iu khin cc qu trnh gin on.

Cho n nay, danh mc cc chng loi PLC c mt trn th trng thtphong ph n mc kh c th bao qut. Chng khng nhng khc nhau cng sut lm vic ca b x l trung tm, dung lng b nh v s lngcc cng vo/ra, m cn cc c tnh chc nng nh cu trc linh hot,phng php lp trnh v kh nng ni mng. Tr mt s loi nh dngtrong cc ng dng n gin, hu ht cc PLC hin i u khng dng li vic thc hin cc php tnh logic n gin, m cn c kh nng lm vic vicc tn hiu tng t v thc hin cc php ton s hc, thm ch c cc thut

ton iu khin phn hi nh iu khin nhi u im, PID v iu khin m.Cc b m, b nh thi v mt s hm ton hc thng dng thuc phm vi

chc nng chun ca mt PLC. Vic s dng PLC v vy khng ch dng li cc qu trnh gin on, m nay rt ph bin i vi iu khin cc qutrnh lin tc nh trong cng nghip ch bin, khai thc, cng ngh mitrng v.v...

Mt s h DCS trn nn PLC tiu biu l SattLine (ABB), Process Logix(Rockwell), Modicon TSX (Schneider Electric), PCS7 (Siemens), Thc cht,ngy nay a s cc PLC va c th s dng cho bi ton iu khin logic viu khin qu trnh. Tuy nhin, cc PLC c s dng trong cc h iukhin phn tn thng c cu hnh mnh, h tr iu khin trnh t cng vicc phng php lp trnh hin i (v d SFC).

Cu trc ph n cng

Hnh 3-5 minh ha cc thnh phn chc nng chnh ca mt h thngthit b iu khin kh trnh v quan h tng tc gia chng. V c bn, mtPLC cng c cc thnh phn ging nh mt my vi tnh thng thng, l vi

x l, cc b nh lm vic v b nh chng trnh, giao din vo/ra v cungcp ngun. Tuy nhin, mt im khc c bn l cc thnh phn giao din



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ngi-my nh mn hnh, bn phm v chut khng c trang b y. Vic

lp trnh v vy phi c thc hin gin tip bng mt my tnh ring bit,ghp ni vi CPU thng qua giao din thit b lp trnh (thng l mt cngni tip theo chun RS-232 hoc RS-485).

B x l trung tm (Central Processing Uni t, CPU) bao gm mt hocnhiu vi x l, b nh chng trnh, b nh lm vic, ng h nhp v giaodin vi thit b lp trnh, c lin kt vi nhau thng qua mt h bus nib. Nhim v chnh ca CPU l qun l cc cng vo/ra, x l thng tin, thchin cc thut ton iu khin. B nh chng trnh thng c dng EPROM(Erasable and Programmable Read Only Memory ) hoc EEPROM

(Electrically Erasable and Programmable Read Only Memory ), cha h

iu hnh v m chng trnh ng dng. D liu vo/ra cng nh cc d liutnh ton khc c lu trong b nh lm vic RAM (Random AccessMemory). ng h nhp c vai tr to ngt cng iu khin chng trnhtheo chu k, thng thng trong khong t 0,01giy ti 1000 pht.

Cc thnh phn vo/ra (input/oupu t, I/O) ng vai tr l giao din giaCPU v qu trnh k thut. Nhim v ca chng l chuyn i, thch ng tnhiu v cch ly galvanic gia cc thit b ngoi vi (cm bin, c cu chphnh) v CPU. Cc thnh phn vo/ra c lin kt vi CPU thng qua mt

h bus ni b hoc qua mt h bus trng (xem chng 3).

B cung cp ngun (power supply , PS) c vai tr bin i v n nh

ngun nui (thng thng 5V) cho CPU v cc thnh phn chc nng khc tmt ngun xoay chiu (110V, 220V,...) hoc mt chiu (12V, 24V,...).

Bn cnh cc thnh phn chnh nu trn, mt h thng PLC c th c cc

thnh phn chc nng khc nh ghp ni m rng, iu khin chuyn dngv x l truyn thng.



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Tnhiuo

Votngt

vvps

(AI,DI)

Ratngt

vras

(AO,

DO)

Tnhiuiukhin

Vi x l

CPU

nghnhp

Giao dinlp trnh

B nhchng trnh

B nhlm vic

Ngunnui(PS)

Hnh 3-5: Cc thnh phnchc nng chnh ca mt PLC

Thi t k module v thi t kgn

Ty theo s phn chia chc nng trn cc thnh phn thit b, ta c thphn bit gia cc PLC c thit k module v cc PLC c thit k gn. Trongmt PLC c thit k gn, tt c cc chc nng c tch hp gn trong mtthit b. Thng thng, loi PLC ny c sn mt s cng vo/ra c nh. Mts cng c tch hp giao din truyn thng cho mt loi bus trng. Tuynhin, mt s t loi c cu trc gn vn cho php tng s lng cng vo/rahoc b sung giao din mng bng cc module m rng c bit. PLC c cutrc gn thch hp vi cc bi ton n gin.

i vi cc ng dng c qui m va v ln, ta cn s dng cc PLC cthit k module bi linh hot cao. y, hu ht mi thnh phn chcnng c thc hin bi mt module phn cng ring bit, c lp t trnmt hoc nhiu gi . Bn cnh cc thnh phn c bn l CPU, ngun v cc

module vo/ra, mt PLC cn c th cha cc module chc nng, cc moduleghp ni v module truyn thng. H bus ni b c s dng ghp nicc module m rng vi CPU thng c gi l bus mt sau (backplanebus ).

Cc module chc nng (function modul e, FM) c s dng thc hinmt s nhim v iu khin ring, v d module iu khin PID, module iu

khin ng c bc, module cn,... Cc module ny hot ng tng i clp vi CPU, tuy nhin c th trao i d liu qu trnh v d liu tham s

thng qua bus ni b v cc hm hoc khi hm giao tip h thng.



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Cc module ghp ni (interface module , IM) c s dng trong vic m

rng h thng khi s lng cc module ln, khng ch trn mt gi .Thng thng, mi gi cn c mt module ngun ring bn cnh moduleghp ni. Thng qua cc module ghp ni, mt CPU c th qun l tt c ccmodule trn cc gi . S lng v chng loi cc module cho php trn mtgi cng nh s lng tng cng ph thuc vo kh nng qun l ca loiCPU c th.

Cc module truyn thng (communication modul e, CM) c vai tr l giaodin mng, c s dng ghp ni nhiu PLC vi nhau, vi cc thit btrng v vi my tnh gim st. Cc module truyn thng m nhim x lgiao thc mt cch c lp vi CPU. Tuy nhin trong mt s trng hp, b

x l trung tm cng c tch hp sn giao din mng cho mt h bustrng thng dng.

3.2.3 Cc h DCS trn nn PC

Gii php s dng my tnh c nhn (PC) trc tip lm thit b iu khinkhng nhng c bn ti rng ri, m tr thnh thc t ph bin trongnhng nm gn y. Nu so snh vi cc b iu khin kh trnh (PLC) vcc b iu khin DCS c chng th th mnh ca PC khng nhng nm tnh nng m, kh nng lp trnh t do, hiu nng tnh ton cao v a chcnng, m cn kha cnh kinh t. Cc bc tin ln trong k thut my tnh,

cng nghip phn mm v cng ngh bus trng chnh l cc yu t thc ykh nng cnh tranh ca PC trong iu khin cng nghi p.

DCS trn nn PC l mt hng gii php tng i mi, mi c mt s snphm trn th trng nh PCS7 (Siemens, gii php Slot-PLC), 4Control

(Softing), Stardom (Yokogawa), Ovation (Westinghouse-Emerson Process

Management) Hng gii php ny th hin nhiu u im v mt gi

thnh, hiu nng tnh ton v tnh nng m. Mt trm iu khin cc bchnh l mt my tnh c nhn cng nghip c ci t mt h iu hnhthi gian thc v cc card giao din bus trng v card giao din bus hthng.

Trong gii php iu khin dng my tnh c nhn th mt vn thngrt c quan tm l tin cy ca my tnh. Mt phn ta c th yn tm bivi cu trc vo/ra phn tn, my tnh iu khin c t trong phng iukhin trung tm vi iu kin mi trng lm vic tt. Mt khc, trn thtrng cng c rt nhiu loi my tnh c nhn cng nghip, m bo tin cy cao khng km mt PLC. Mt khi my tnh ch c ci t h iu



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hnh v phn mm iu khin th kh nng gy li do phn mm cng s

c gim thi u.

Tuy nhin, i vi cc ng dng c yu cu cao v tnh sn sng, tin cyca h thng, ta cn c mt gii php d phng thch hp. Gii php ngin v tit kim nht l d phng lnh, c ngha l trong trng hp c sc ti my tnh iu khin xy ra ta ch cn thay th mt my mi vi cuhnh v cc phn mm c ci t ging ht my chnh. Song gii phptt hn l s dng mt cu hnh d phng nng.

3.3 Cc vn k thut

Cc vn k thut di y ng vai tr c bit quan trng khi nghincu v cc h iu khin phn tn, s c cp chi tit trong cc phnsau. Kin trc x lphn tn (distributed processin g): Cu trc phn tn v

mt vt l (a l) dn n phn tn v mt x l thng tin. X l phntn l mt khi nim vay mn t lnh vc tin hc. X lphn tn khcvi x l cc b v khc vi x l ni mng tnh thng nht, xuynsut trong vic xy dng ng dng v trao i d liu gia cc trm.

Tnh nng thi gian thc (real-time ): Tnh nng ca mt h thng lun

sn sng phn ng vi cc s kin bn ngoi v a ra p ng mt

cch ng n v kp thi. Vi kin trc x l phn tn, vic p ng

tnh nng thi gian thc c ci thin bi kh nng x l thng tin tich. Song cng nhiu vn c t ra trong vic giao tip gia cc

thnh phn ( real-time interprocess communicatio n), trong vn giao thc mng ng mt vai tr quan trng.

Tnh sn sng (availability ) v tin cy (reliability ): Mt c im

ni bt so vi cc hng gii php khc l tnh sn sng cao thng quakh nng d phng tch hp, c th la chn d phng cho tng thnhphn. Tnh sn sng, phng php giao tip s, kin trc x l phntn, phn mm ng gi, phn cng chun ha cng nghip, tchhp cao gia cc thnh phn phn cng v phn mm l cc yu tgip cho cc h thng iu khin phn tn c tin cy cao.

H tr chun (standard support ): Thc ra, y khng phi l c imtiu biu ca cc h DCS truyn thng. Nhng y l mt yu cukhng th thiu c trong cc h DCS mi. c bit, s tng thchvi cc chun cng nghip l tin cho tnh nng m, cho kh nng

tng tc vi cc thit b ca cc hng th ba.



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Cng c phn mm (software tools ): Vic xy dng cc ng dng iu

khin c h trbi cc cng c lp trnh hoc cu hnh rt mnhv cc th vin phn mm ng gi chun, da theo cc chun quc t.

Cc cng c phn mm iu khin gim st cng c tch hp v sdng chung mt c sd liu trong h thng. Khc vi cc gii phpiu khin n l nh PLC hoc PC, ta khng phi s dng mt cngc ring, xy dng ring giao din ngi-my (HMI) v cc chc nngSCADA khc. SCADA chnh l mt thnh phn ca mt h DCS. Qutrnh to giao din ngi- my, to h thng cnh bo, to cng thciu khin, nm trong vic pht trin ng dng, i i vi vic xy

dng chng trnh iu khin cp thp.



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4 X L THI GIAN THC V X L PHNTN

4.1 Mts khi nim cbn

4.1.1 H thng thi gian thc

Mt h thng thi gian thc l mt h thng m s hot ng tin cy can khng ch ph thuc vo s chnh xc ca kt qu, m cn ph thuc vothi im a ra kt qu phn ng vi s kin bn ngoi. H thng c li

khi thi gian yu cu khng c tho mn.

Mt h thng thi gian thc c cc c im tiu biu sau: Tnh b ng: H thng phi phn ng vi cc s kin xut hin vo

cc thi im khng bit trc. Tnh nhanh nhy: H thng phi x l thng tin mt cch nhanh chng

c th a ra kt qu phn ng mt cch kp thi. Tnh tin nh: D on trc c thi gian phn ng tiu biu,

thi gian phn ng chm nht cng nh trnh t a ra cc phn ng.

Tuy tnh nhanh nhy l mt c im tiu biu, nhng mt h thng ctnh nng thi gian thc khng nht thit phi c p ng tht nhanh m

quan trng hn l phi c phn ng kp thi i vi cc yu cu, tc ng bnngoi. C th ni, tt cc cc h thng iu khin l cc h thng thi gianthc. Ngc li, mt s ln cc h thng thi gian thc l cc h thng iukhin. Mt b iu khin phi a ra c tn hiu iu khin kp thi saumt thi gian nhn c tn hiu o a qu trnh k thut v trng thimong mun. Mt h thng truyn thng c tnh nng thi gian thc phi ckh nng truyn tin mt cch tin cy v kp thi i vi cc yu cu ca cci tc truyn thng. Tnh nng thi gian thc ca mt h thng iu khinphn tn khng ch ph thuc vo tnh nng thi gian thc ca tng thnhphn trong h thng, m cn ph thuc vo s phi hp hot ng gia cc

thnh phn .

4.1.2 X l thi gian thc

X l thi gian thc l hnh thc x l thng tin trong mt h thng m bo tnh nng thi gian thc ca n. Nh vy, x l thi gian thc cngc cc c im tiu biu nu trn nh tnh b ng, tnh nhanh nhy v tnh



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tin nh. c th phn ng vi nhiu s kin din ra cng mt lc, mt h

thng x l thi gian thc s dng cc qu trnh tnh ton ng thi.

Qu trnh tnh ton l mt tin trnh thc hin mt hoc mt phn

chng trnh tun t do h iu hnh qun l trn mt my tnh, c th tnti ng thi vi cc qu trnh khc k c trong thi gian thc hin lnh vthi gian xp hng ch i thc hin.

Qu trnh tnh ton c chia thnh hai loi: Qu trnh nng cn (process ): l qu trnh tnh ton c khng gian

a ch ring. Qu trnh nh cn (thread ): l qu trnh khng c khng gian a ch

ring.

Cc hnh thc t chc cc qu trnh tnh ton ng thi: X l cnh tranh: Nhiu qu trnh tnh ton chia s thi gian x

l thng tin ca mt b x l. X l song song: Cc qu trnh tnh ton c phn chia thc hin song

song trn nhiu b x l ca mt my tnh. X l phn tn: Mi qu trnh tnh ton c thc hin ring trn

mt my tnh.

Trong cc h thng iu khin, khi nim task cng hay c s dng bncnh qu trnh tnh ton. C th ni, task l mt nhim v x l thng tintrong h thng, c th thc hin theo c ch tun hon (periodic task) hoc

theo s kin (event task). V d, mt task thc hin nhi m v iu khin chomt hoc nhiu mch vng kn c chu k trch mu ging nhau. Hoc, mttask c th thc hin nhi m v iu khin logic, iu khin trnh t theo ccs kin xy ra. Task c th thc hin di dng mt qu trnh tnh ton duynht, hoc mt dy cc qu trnh tnh ton khc nhau.

4.1.3 H iu hnh thi gian thc

Cc trm iu khin trong mt h iu khin phn tn bao gi cng hot

ng da trn nn mt h iu hnh thi gian thc. H iu hnh thi gianthc l mt h iu hnh h tr cc chng trnh ng dng x l thi gian

thc. Bn thn h iu hnh thi gian thc cng l mt h thi gian thc theong ngha ca n, v vy cng c cc c im tiu biu cp. Mt hiu hnh thi gian thc bao gi cng l mt h a nhim (multi-tasking), htr x l cnh trnh hoc/v x l song song. Lp lch, ng b ha qu trnhv giao tip lin qu trnh l cc khi nim quan trng trong mt h iuhnh thi gian thc.



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Ph ng php lp lch (Scheduling)

Vic lp lch thc hin cho cc task c th c thc hin theo hai cch: Lp lnh tnh: th t thc hin cc qu trnh tnh ton khng thay

i m c xc nh trc. Lp lnh ng: h iu hnh xc nh lnh trc hoc sau khi qu

trnh tnh ton bt u.

Tuy nhin, ta cn c mt sch lc lp lnh (strategy) p dng i vitng tnh hung c th. C th chn mt trong nhng cch sau: FIFO (First In First Out): mt tin trnh n trc s c thc hin

trc. Mc u tin c nh/ng: ti cng mt thi im, cc tin trnh c

t cc mc u tin c nh hoc c th thay i nu cn. Preemptive : cn gi l chen hng, tc l chn mt tin trnh

thc hin trc cc tin trnh khc. Non -Preemptiv e: khng chen hng. Cc tin trnh c thc hin bnh

thng da trn mc u tin ca chng.

Vic tnh mc u tin ca mi tin trnh c thc hin theo mt trong scc thu t ton lp lch sau: Rate monotonic : cng thng xuyn cng c u tin. Deadline monotonic : cng gp cng c u tin. Least laxit y: t l thi gian tnh ton/thi hn cui cng(deadline)

cng ln cng c u tin.

ng b ho qu trnh

Khi cc qu trnh tnh ton cng s dng mt ti nguyn loi tr ln nhaunh mt vng nh, cng vo/ra, hoc chng ph thuc ln vo nhau v dqu trnh 1 ch kt qu ca qu trnh 2... s rt d dn n tnh trng tcnghn (Deadlock), hay to ra mt tnh hung chy ua (Race Condition). Dovy vic ng b ho cc qu trnh l iu cn thi t.

C th thc hin vic ny theo cc phng php sau: Mutex (Mutual exclusion) Critical Section Semaphone

Monitor



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Giao tip lin qu trnh

Giao tip lin qu trnh l giao tip gia cc qu trnh tnh ton thuccng mt h iu hnh trn mt my. C hai loi: Gia cc Thread thuc cng mt Process: s dng cc bin ton cc. Gia cc Process khc nhau hoc gia cc Thread thuc cc

Process khc nhau: s dng cc phng php nh shared memory,slot, pipes, mailbox, files...

4.1.4 X lphn tn

X l phn tn gip nng cao nng lc x l thng tin ca mt h thng,gp phn ci thin tnh nng thi gian thc, nng cao tin cy v tnh linh

hot ca h thng.

Phn bit cc khi nim: X l cc b - ng dng n c X l cnh tranh - ng dng a nhim X l tp trung - ng dng tp trung X l ni mng - ng dng mng X lphn tn - ng dng phn tn

Cn phn bit r gia ng dng mng v ng dng phn tn. Trong mtng dng mng, cc chng trnh trn mi trm tn ti hon ton c lp vinhau v vic giao tip gia chng c thc hin qua c ch hin (explicit

communicatio n). Web l mt ng dng mng tiu biu. Trong mt ng dngphn tn, cc chng trnh trn cc trm hp tc cht ch vi nhau thng

qua c ch giao tip ngm (implicit communicatio n) cng thc hin mtnhim v tng th ca h thng. Chc nng iu khin trong mt h iu

khin phn tn c thc hin di dng mt ng dng phn tn.

Cc vn ca x lphn tn Phn chia v phi hp nhim v Giao tip gia cc trm ng b ha cc qu trnh x lphn tn D phng, khc phc li

4.2 Cc kintrc x lphn tn

Ki n trc Master/Slave Cc chc nng x l thng tin c phn chia trn nhiu trm t



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Mt trm ch phi hp hot ng ca nhiu trm t

Cc trm t c vai tr, nhim v tng t nh nhau (tuy vi cci tng khc nhau)

Cc trm t c th giao tip trc tip, hoc khng V d tiu biu: ng dng iu khin s dng bus trng, trm

iu khin l trm ch, cc vo/ra t xa hoc thit b trng l cc trmt.

Ki n trc Client/Server Chc nng x l thng tin c phn chia thnh hai phn khc

nhau, phn s dng chung cho nhiu bi ton c thc hin trn ccserver, phn ring thc hin trn tng client.

Gia cc client khng cn thit c giao tip trc tip Vai tr ch ng trong giao tip thuc v client V d tiu biu: Trong cp iu khin gim st, c th s dng

mt trm ch cho vic thu thp v qun l, lu tr d liu v cnh giibo ng, cc trm vn hnh l thc hin giao din ngi-my vi vai trl client.

Ki n trc bnh ng Cc trm c vai tr bnh ng, phi hp hot ng trc tip vi

nhau khng qua trung gian V d tiu biu: Trong cp iu khin, cc trm iu khin cc b phn

chia thc hin chc nng iu khin cho c dy chuyn sn xut.

Kin trc t tr Cc trm c vai tr bnh ng, c th hot ng tng i c

lp nhng s phi hp hot ng to hiu qu cao nht. V d tiu biu: Kin trc iu khin thng minh cc h thng n tn

hiu giao thng.

4.3 C ch giao tip

D liuton cc (Glo balData) Ging nh mt vng nh chung Mi trm u cha mt nh ca bng d liu ton cc, trong

c ton b d liu cn trao i ca tt c cc trm khc Mi trm gi phn d liu ca n ti tt c cc trm, mi trm t cp

nht nh ca bng d liu ton cc n gin, tin nh nhng km hiu qu p dng cho lng d liu nh, tun hon, thch hp trong kin

trc bnh ng (v d gia cc trm iu khin).



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Hi tun t (Polling, Scanning)

Mt trm ng vai tr Master C ch hi/ p tun t n gin, tin nh, hiu qu cao p dng cho trao i d liu tun hon, thch hp trong kin trc

Master/Slave

Tay i (Peer-To-Peer) Hnh thc c lin kt hoc khng lin kt, cu hnh trc hoc khng

cu hnh trc, c xc nhn hoc khng xc nhn, c yu cu hoc

khng c yu cu

Linh hot nhng th tc c th phc tp

p dng cho trao i d liu tun hon hoc khng tun hon, thchhp cho tt c cc kin trc khc nhau.

Cho/ t hng (Subscriber/ Publisher) Ni dung thng bo c mt trm ch cho v cc trm client t

theo c ch tun hon hoc theo s kin Thng bo ch c gi ti cc trm t (c th gi ring hoc gi

ng lot) Linh hot, tin nh, hiu sut cao p dng cho trao i d liu tun hon hoc khng tun hon, thch

hp cho kin trc Client/Server hoc kin trc bnh ng.

Hp th (Mailbox) Cc trm s dng mt mi trng trung gian nh files, mt c sd

liu hoc mt chng trnh server khc ghi v c d liu Mi bc th mang d liu v m cn cc (ni dung th hoc/v ngi

nhn)

Gi v nhn th c th din ra ti bt c thi im no Linh hot nhng km hiu qu, khng m bo tnh nng thi gian

thc

p dng cho trao i d liu c tnh cht t quan trng, thch hp cho

kin trc Client/Server hoc kin trc t tr.



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4.4 ng b ha trong x lphn tn

4.4.1 ng b ha cc tn hiuvo/ra

Cu trc vo/ra phn tn s dng bus trng lm ny sinh mt vn cha c xt ti trong l thuyt iu khin s. l s khng ng b cacc tn hiu vo/ra do thi gian tr tng knh khc nhau, kh xc nh.

C hai cch gii quyt sau: t cu hnh bus v chn chu k iu khin sao cho chu k bus

nh hn nhiu so vi chu k iu khin c th b qua thi gian trtng knh khc nhau.

S dng loi bus trng c h tr ng b ha cc u vo/ra, v dProfibus-DP.

V d, cc lnh di y c s dng trong Profibus-DP ng b hacc u vo/ra: FREEZE: hi nhn c lnh ny, cc DP-Slave s nhn d liu u ra

gi t DP-Master v sau s khng nhn d liu u ra gi t DP-Master na cho n khi kt thc lnh FREEZE.

UNFREEZE: Lnh ny lm kt thc lnh FREEZE . Cc DP-Slave stip tc nhn d liu u ra gi t DP-Master.

SYNC: Khi nhn c lnh ny,tt c hoc mt vi DP-Slave s gid liu ti DP-Master v sau DP-Master s khng nhn d liu u

vo gi t DP-Slave na cho n khi kt thc lnh SYNC. UNSYNC: Lnh ny lm ngng lnh SYNC. DP-Master s tip tc nhn

d liu u vo gi t cc DP-Slave.

4.4.2 ngb ha thi gian

Gia cc trm iu khin cc b v cc trm vn hnh cn c mt s ngb ha thi gian mt cch cht ch, v y l vn lin quan h trng titnh chnh xc v tin cy ca cc thng tin iu khin, vn hnh, thngbo bo ng.

ng b ho thi gian trong mt h iu kh in phn tn, mt trm vnhnh c th c chn lm qui chiu, tt c cc trm khc ni vi bus hthng c ng b ho thi gian theo trm ny thng qua cc thng bo ging lat. Trong mt s h thng mng c h tr trc tip vic ng b hathi gian, ngi ta c th chn mt thit b c chng (time master ) phc v

mc ch ny. Ta c th nh ngha 2 trm vn hnh lm qui chiu nhng ti



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mt thi im ch c mt trm mang tn hiu ng b ho, nu trm b li

th trm cn li t ng hot ng.

Trong cng nghip ch bin, khong thi gian chnh lch cho php giacc trm thng trong phm vi +/-5ms. Cc thng bo thi gian cn gi

ng lot theo chu k ti a 1 pht.



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5 CNG NGH I TNG TRONG IUKHIN PHN TN

5.1 Lp trnh hng i tng

Lp trnh hng i tng c coi l phng php lp trnh chun hinnay bi n c nhiu u im ln so vi cc phng php c in. Mc tium lp trnh hng i tng t ra l: n gin ho vic xy dng v s dng cc th vin Cho php dng li m. Nu hm th vin khng ph hp vi yu

cu ca ngi lp trnh th ngi lp trnh c kh nng sa i d dngm khng cn tm hin ngn ngun, khng cn phi c m ngun cahm trong tay. M sinh ra t thc nghim d dng c dng litrong m chnh thc. Ni khc i, ngi lp trnh c iu kin thoi mi sng to.

Ci thin kh nng bo tr ca m, m phi d hiu, d sa i. Trn

thc t, vic bin son ti liu bao gi cng i sau kh xa so vi mc vit ra.

Cho php to ra chng trnh d m rng. C th thm chc nng chochng trnh m khng nh hng dy chuyn n m vit. M angc l m hi, l tin bc, khng th tr gi t cho mi chc nng thm

vo.

Lp trnh hng i tng phi c thc hin thng qua mt ngn nglp trnh hng i tng. t c cc mc tiu trn, mi ngn ng lptrnh hng i tng u th hin ba khi nim: ng gi (encapsulation,packaging), a hnh (polymorphism ) v tha k (inheritance ). Cc ngn nglp trnh hng i tng thng dng l C++, Java, Ada...

5.2 Phn tch v thit k hng i tng

Theo dng pht trin ca cng ngh cng tin, phng php lp trnh tin ho t lp trnh khng c cu trc ln lp trnh c cu trc v ti nay llp trnh hng i tng. Phng php phn tch, thit k phn mm cngi theo cc bc tin ho ny. Trc y, ngi ta phn tch, thit k phnmm theo kiu hng th tc (procedure-oriented ) hoc hng d liu (data-

oriented ). Theo phng php ny, phn mm cn xy dng c chia thnhgii thut v cu trc d liu. Trong qu trnh phn tch, gii thut c



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phn chia thnh cc gii thut con n gin hn, cu trc d liu ln c

chia thnh nhng cu trc nh hn. Qu trnh tng t cng c tin hnhtrong qu trnh thit k.

Phng php phn tch, thit k hng th tc hoc hng d liu c uim n gin, nhanh chng to ra kt qu (do tin hnh theo kiu t trnxung) nhng kt qu to ra khng phn nh bn cht ca th gii thc dnn cng nhc, kh thay i khi yu cu t ra thay i, kh m rng khi hthng pht tri n.

Phng php phn tch, thit k phn mm tin tin hin nay l hng itng (object-oriente d), trong khi c bn xy dng nn phn mm li tng hay lp. Ni mt cch n gin, i tng l s phn nh th gii

t nhin xung quanh. V d nu trong h thng iu khin c cc thit bvo/ra s/tng t nh AI, AO, DI, DO th trong phn mm cng c cc lp AI,AO, DI, DO ; trong h thng iu khin c khu iu khin PID th trong

phn mm cng c lp PID,...

Trong cc h thng iu khin, cc i tng c th i din cc thnhphn h thng nh: Cc thut ton iu khin X l s kin v bo ng X l mnh lnh Quan st v chn on Cu hnh vo/ra Mphng Thng tin thit k

Vic tru tng ho th gii t nhin thnh cc lp i tng nh vy cgi l m hnh ho hng i tng. Da trn m hnh i tng thu c,phng php phn tch, thit k phn mm hng i tng s b sung thmcc lin kt v lp i tng mi, tinh chnh li,... to ra mt m hnh itng chi tit ca phn mm. Cui cng, ngi lp trnh s dng mt ngnng lp trnh no (khng nht thit phi l ngn ng hng i tng) thhin m hnh i tng chi tit thnh m ngun. u im ln nht ca phntch, thit k phn mm hng i tng khng phi nm ch to ra

chng trnh nhanh tn t cng sc, m nm ch n gn vi thc t v do thc y vic ti s dng li nhng thnh qu xy dng c nh m

lnh hay bn thit k.



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5.2.1 Ngn ng m hnh ha thng nht UML

phc v cho cng vic m hnh ho vn l ct li ca phn tch, thitk phn mm hng i tng, ngn ng UML (unified modeling language )c s dng rng ri. UML - mt chun quc t c qun l bi t chcOMG (object management group ) - l mt ngn ng ha dng trcquan ha, c t, xy dng v t liu ha h thng thin v phn mm. UMLem li cho ngi s dng phng php chun vit bn thit k h thngbao trm t nhng th c th nh cc lp vit bng mt ngn ng lp trnhno , cc thnh phn phn mm c th ti s dng,... cho n nhng yut tru tng nh chc nng ca ton b h thng. V l do ny, ngn ngUML khng ch c s dng m t, xy dng kin trc v thit k ca cc

h thng phn mm, m cn l mt cng c m hnh ha thch hp cho cch thng k thut ni chung v cc h thng iu khin ni ring. Trn Hnh

5-1 l mt biu lp UML, minh ha n gin cc lp i tng v quan h

ca chng trong mt h thng iu khin.

sensor

Sensor

Controller actuator

Actuator

1 controller

Thermometer

sensors

*ControlSystem

valves

1..*Valve

1 plant

Plant

PT2

Hnh 5-1: M hnh ha mth thngiu khin s dng UML

C th ni, UML l mt ngn ng m hnh ha rt mnh, a nng. Ti liu

v UML c rt nhiu, v d [1][2].

5.2.2 Mu thit k

Mu thi t k l s hnh thc ho ca cch tip cn ti mt vn thnggp trong ng cnh c th. Mi mu thit k m t mt gii php cho mt vn thit k c th trong mt ng cnh xc nh. Gii php ny c chng

minh l hp l, s dng nhiu ln em li kt qu tt v do c tru



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tng ho thnh mt mu. Ni mt cch ngn gn, mu thit k l kinh

nghim thit k c kt li. Bng cch dng cc mu thit k, ngi thit kkhng khi thit k h thng ca mnh t u m s dng li kinh nghim c t trc, dn n cht lng thit k tt hn, tng tnh ti s dng ca bnthit k. Mt s mu thit k tiu biu l Abstract factory , Iterator ,

Prototype , Singleton v Template metho d. xy dng cc h thng phntn hin i, ngi ta s dng cc mu thit k nh Proxy , Broker ,

Marshaling/Unmarshalin g, Adapter v Interface Mapping . Mt tc phmc coi l kinh in vit v ti ny l [3].

5.2.3 Phn mm khung

Phn mm khung l mt dng phn mm bao gm th vin v cc muthit k gip ngi s dng d dng to cc chng trnh ng dng bng cchb sung cc phn m ng dng c th vo cc khung c sn. im khc nhaugia mt phn mm khung vi mt th vin lp hay mt th vin hm nthun l: Mt th vin ch l mt tp hp ca cc lp hay hm hon chnh phc

v mt mc ch ng dng no . M ca mt th vin lp hay hmc chng trnh ng dng ch ng gi.

Mt phn mm khung cha mt s lp cha hon chnh, tc chas dng to th nghim c ngay (lp tru tng), m bt buc phidn xut v b sung m ng dng c th. Vic xy dng mt chng

trnh ng dng phi tun theo cc mu thit k c sn. Khng nhngchng trnh ng dng gi m trong phn mm khung, m mtrong phn mm khung cng ch ng gi m ng dng.

C th so snh mt phn mm khung nh mt khung nh b tng cc sn theo mt thit k, ngi thi cng cn b sung cc phn tng bao,tng ngn, ca s... theo thit k , s dng cc th vin l cc vin gch,cnh ca, tm vch ngn lm sn.

Mt s v d phn mm khung tiu biu l MFC (Microsoft FoundationClass ), Microsofts COM (Component Object Model), Borlands VCL (VitualComponent Library ).

5.3 Phn mm thnh phn

Phn mm thnh phn (component software ) l mt hng i mi, phttrin trn c sphng php lp trnh hng i tng. Lp trnh hng itng cho php s dng li phn mm (di dng cc class ) vo giai on



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bin dch (compile-time ), trong khi phn mm thnh phn cho php s dng

li phn mm (di dng cc component ) vo c giai on bin dch v giaion chy (run-time ). Do vy, theo t tng phn mm thnh phn, ngn nglp trnh cng nh lp l th yu, giao din mi l quan trng. Ni nh vytc l mt thnh phn phn mm (component ) l cc phn mm c th cvit cc ngn ng khc nhau, c hon chnh, bin dch v ng gi, ccc giao din chun c th s dng thun tin, linh hot trong nhiu ngdng khc nhau m khng cn bin dch li. Thm ch trong mt s trnghp, vic s dng cc thnh phn phn mm c sn khng i hi lp trnh.V d ngi son tho mt vn bn c th s dng kt hp cc thnh phnphn mm c sn nh trnh son tho cng thc, v th, ... m cm tngnh tt c u nm trong chng trnh son tho vn bn.

Mt s v d m hnh phn mm thnh phn tiu biu l: Delphi VC JavaBeans

Visual Basic VBX ActiveX-Controls

C th ni, hu ht cc h thng pht trin ng dng trong cc h iu

khin phn tn hin nay thc hin trit t tng hng i tng v phnmm thnh phn. T tng s dng khi hm, cc khi ha, cc khichng trnh trong nhiu h thng l nhng v d tiu biu.

5.4 i tng phn tn

i tng phn tn cng l mt hng pht trin t nhin t phng phplun hng i tng, bn cnh phn mm thnh phn. Trong khi phn mmthnh phn quan tm ti vic ng gi cc i tng c th s dng limt cch thun tin, th i tng phn tn tp trung vo vn kin trccc i tng c kh nng giao tip mt cch trong sut trn cc nn v hthng mng khc nhau (giao tip ngm). Cng ging nh phn mm thnhphn, mt i tng phn tn c th thc hin mt ngn ng bt k,nhng n phi c cc giao din theo mt chun no c th hp tc vi

nhau lin qu trnh v xuyn mng mt cch n gin nh hai i tngtrong mt chng trnh. Ni nh vy, mt i tng phn tn cng c sdng khi bin dch, ng gi hon chnh di dng mt server . Tuy nhin,vic s dng chng c th vn i hi phi lp trnh pha client (mt i

tng phn tn hoc mt chng trnh ng dng thng thng). Ngy nay, i



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tng phn tn v phn mm thnh phn gp nhau nhiu im, v d

trong cng ngh COM/DCOM/ActiveX.

Ni tm li, mt i tng phn tn l mt i tng phn mm trong mt

h thng phn tn, c th c s dng bi cc chng trnh ng dng hoccc i tng khc thuc cng mt qu trnh tnh ton, thuc mt qu trnhtnh ton khc hoc thuc mt trm khc trong mng theo mt phng thcthng nht thng qua giao tip ngm (khng ti giao thc truyn thngc th, trong sut vi h iu hnh, kin trc phn cng v h thng mng).Mt i tng phn tn c cc thuc tnh c th truy cp c t xa, c ccphp ton c th gi c t xa.

Mi i tng phn tn (distributed objec t) - bt k dng thc hin, nn

trin khai v v tr ci t - u c cn cc phn bit v c th c s dngnh cc i tng ni trnh (in-process objec t). Li th quyt nh y lvic to dng mt ng dng phn tn c thc hin mc tru tng caohn so vi kiu lp trnh mng c in, nh vy trn nguyn tc khng khcbit so vi to dng mt ng dng n c (stand-alone applicatio n).

t c iu , ta cn s h tr hu hiu ca mt phn mm khung(framework ). Hin nay c hai m hnh chun cho nhng cng trnh khung l DCOM v CORBA. CORBA cho php s dng mt cch rng ri v linhhot hn, trong khi DCOM hin nay hu nh ch s dng c trn cc h

Microsoft Windows (95, 98, NT, 2000).



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6 KIN TRC I TNG PHN TNMt kin trc i tng phn tn nh ngha m hnh cc i tng phn

tn, m hnh giao tip v chun giao tip gia cc i tng phn tn.

6.1 Yu cu chung

Mt kin trc i tng phn tn to iu kin cho vic lp trnh mtmc tru tng cao hn so vi phng php hng i tng c in. C th,im khc bit so vi lp trnh hng i tng c in nm tnh trongsut phn tn (distribution transparency ), th hin qua cc c tnh sau:

Trong sut v tr: Mt client khng cn bit rng i tng server nmtrong cng mt qu trnh tnh ton, thuc mt qu trnh tnh ton khctrn cng mt trm hoc trn mt trm khc, cch s dng i tngserver l thng nht. Ngc li cng vy.

Trong sut th hin: Client khng cn quan tm ti vic i tngserver c th hin bng ngn ng lp trnh no v bng phng phpno, m ch cn quan tm ti giao din c th s dng.

Trong sut nn: Mt client khng cn bit rng i tng server nm

trn h iu hnh no, trn nn my tnh kin trc ra sao. Trong sut truyn thng: M thc hin client v cc i tng

server khng lin quan ti mng truyn thng v giao thc truyn

thng c t h

6.2 Cc mu thit k

p ng cc yu cu trn, ngi ta thng p dng cc mu thit ksau y: Proxy : Mt i tng i din cho server bn pha client, client

c th s dng i tng server n gin nh vi mt i tng nitrnh (v d thng qua con tr).

Broker: B phn che du chi tit v c ch truyn thng c th, to iu

kin cho client/proxy v server giao tip vi nhau m khng ph thuc

vo nn v h thng truyn thng bn di. Broker c mt c bn clientv server.

Adapter : i tng trung gian, c vai tr thch ng giao din giabroker v server, to iu kin cho vic pht trin server mt cch clp, cng nh s dng cc server c sn (cha tun theo kin trc itng phn tn).



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Marshaling/Unmarshalin g: C ch thc hin m ha v ng gi

cc li gi hm bn client thnh cc bc in tng ng vi c chtruyn thng cp thp, cng m gi v gii m cc bc in thnh ligi hmchi tit bn i tng server. Cc phng thc tng t cng c thchin chuyn kt qu t server tr li client. Cc nhim v ny do

proxy, server hoc/v adapter m nhim. Interface Mapping : Gii quyt vn trong sut th hin bng cch

m t cc giao din bng mt ngn ng c lp IDL (Interface

Description Languag e) v cho php nh x sang thc hin bng mtngn ng c th.

Proze A

1: op ( )

Proze B

4: upcall()

5: op( )

client proxy adapter server

2: marshal ( ) 3: dispatch( )

broker_A IPC broker_B

Hnh 6-1: Cc mu thi t k giao tip gia client v i tngserver

6.3 Gii thiu chun CORBA

Chun CORBA [4] do t chc OMG (Object Management Group ) qun lv pht trin. y l hip hi ln nht ca cc nh pht trin, sn xut v ngdng phn mm trn th gii, hin nay c gn 1.000 thnh vin. ChunCORBA a ra mt kin trc i tng phn tn cng vi cc c t ngdng cho nhiu lnh vc khc nhau, nhiu nn khc nhau v nhiu ngn nglp trnh khc nhau. V tnh trung lp ca n, CORBA c h tr rt rng

ri, c bit trong cc h thng thng tin thng mi, phn mm giao dchkinh doanh v dch v vin thng. Tuy nhin, cng do tnh c lp ca ndn n nhi u l do m CORBA khng thc s mnh cc h thng ng quim va v nh.

Hnh 6-2 minh ha cu trc m hnh CORBA, trong b phn trutng trung gian mang tn Object Request Broker (ORB) gi vai tr quantrng nht (broker ). ORB cho php khch hng (clien t) s dng dch v ca

i tng phc v (server) m khng cn bit c th dng thc hin, nn



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trin khai v v tr ci t ca i tng phc v. Kin trc y c thc

hin theo cc mu thit k trnh by trong phn trc.

Client Object Implementation

Dynamic

InvocationIDL

Stubs

ORB

Interface

StaticIDL

Skeleton

Dynamic

SkeletonObject

Adapter

Object Request Broker Core

Hnh 6-2: Cu trc m hnh CORBA

6.4 Gii thiu chun COM/DCOM

COM (Component Object Model) l mt m hnh i tng thnh phn,

mt m hnh c s cho nhiu cng ngh phn mm quan trng ca hngMicrosoft. COM nh ngha chun nh phn v c t kt ni cho vic tngtc gia cc thnh phn ca mt phn mm vi mt thnh phn khc trncng mt qu trnh tnh ton, trn nhiu qu trnh khc nhau hay trn ccmy tnh ring bit. Hng Microsoft cng hy vng mt ngy khng xa COMcng c s dng ph bin trn cc nn phn cng v h iu hnh khcnhau.

COM l mt m hnh lp trnh cs i tng thit k nng cao stng tc gia cc thnh phn phn mm, ngha l, cho php hai hoc nhiung dng hay cc thnh phn d dng giao tip vi nhau cho d chng c

vit bi nhiu ngi khc nhau trong nhng khong thi gian khc nhau,bng nhiu ngn ng lp trnh khc nhau thm ch chy trn cc my tnhkhc nhau, khng hay ci t cng mt h iu hnh. thc hin iu ny,COM nh ngha v thc thi cc k thut cho php cc ng dng kt ni vinhau nh cc i tng phn mm.

Ni cch khc, COM a ra mt m hnh tng tc m qua mt khchhng (clien t) c th kt ni vi cc nh cung cp dch v (objec t) mt cch



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thun tin. Vi COM, cc ng dng kt ni vi nhau v vi h thng qua cc

tp hp ca cc li gi hm - xem nh l cc phng thc hay nhng hmthnh vin, cn gi l giao din.

Theo cch t duy COM, mt giao din l mt quy c kiu mnh giacc thnh phn phn mm nhm cung cp nhng lin quan d nh nhnghu dng tp cc thao tc lin quan danh ngha. Mt i tng c nhngha ph hp vi COM l mt s th hin c bit ca i tng. Mt itng COM ging nh mt i tng C++ nhng khc ch mt clientkhng truy nhp trc tip vo i tng COM m s qua cc giao din m itng cung cp.

6.4.1 Giao dinCch duy nht truy cp d liu hoc tc ng ln mt i tng COM

l thng qua giao din ca n. Mt giao din thc cht l mt nhm cc hmc sn lin quan vi nhau. C th so snh mt giao din vi mt lp c stru tng ch gm cc hm thun o trong ngn ng C++. Giao din nh

ngha c php cc hm thnh vin, gi l cc phng thc (methods ), kiutr v, s lng v cc kiu tham s. Mt giao din khng qui nh c th ccphng thc c thc hin nh th no. Thc cht vic th hin giaodin l s dng con tr truy nhp vo mt mng cc con tr khc v cc contr ny tr ti cc hm ca giao din.

Thng thng, tn ca giao din c bt u bng ch ci I, v d nhIUnknown, IData... nh danh tht ca giao din th hin ch danh GUID

ca n, cn tn ch thun tin cho vic lp trnh v h thng COM s sdng cc ch danh ny khi thao tc trn giao din.

Thm vo , khi giao din c tn hoc kiu c th v tn ca cc hmthnh vin, n ch nh ngha lm th no mt client c th s dng giao din v nhng p ng mong i t i tng qua giao din . V d, giaodin IStack vi hai hm thnh vin PUSH v POP ch nh ngha nhng thng

s v kiu tr v ca hai hm ny v nhng g chng c mong i thc hint client.

C th ni, giao din l phng tin i tng a ra nhng dch v can. C bn im quan trng v giao din m ta cn bit: Mt giao din khng ph i l mtlp theo nh ngha lp thng thng

bi mt lp c th c th hin qua mt i tng cn mt giao dinth khng bi n khng km theo s thc thi.



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Mt giao din khng phi l mti tngbi mt giao din ch n

thun l mt nhm cc hm lin quan v l chun nh phn m qua client v object c th giao tip vi nhau. Cn i tng th c th thc

thi trn nhiu ngn ng vi nhiu th hin ca trng thi bn trong, vdo n c th cung cp con tr n cc hm thnh vin ca giao din.

Giao din c kiu mnh: Mi mt giao din u c mt nh danh

ring nn ngn chn c kh nng xung t c th xy ra i vi cctn ta t cho giao din. iu ny tng thm tnh bn vng cho chngtrnh.

Cc giao din c phn bitr rng: Mi s thay i nh thm hoc

xo hm thnh vin, thay i ng ngha u dn ti hnh thnh mtgiao din mi v c gn mt nh danh mi. Do giao din mi vc khng th xung t vi nhau cho d mi s thay i ch n thu nl v ng ngha.

6.4.2 i tng COM

Mt i tng COM c th c lp trnh bng mt ngn ng thng dngnh C, C++ hoc VB. Mt i tng c th cung cp nhiu giao din. Tt ccc i tng COM u c mt giao din c bn l IUnknown. y l giaodin c scho tt c cc giao din khc trong COM m mi i tng phi htr. Bn cnh , i tng cng c kh nng thc thi nhiu giao din khc.Cc i tng vi nhiu giao din c th cung cp cc con tr truy nhp vo

nhiu bng cha cc hm. Cc con tr ny c th gi c con tr giao din.Trong COM, giao din l mt bng cc con tr ( ging nh vtable trong C++)vo cc hm c thc hin bi i tng.

IUnknown

A

Cc giaoi tng

din khc B

Hnh 6-3: M hnh mti tng COM



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Trong thc t, mt con tr tr n mt giao din l mt con tr ti mt

con tr tr ti bng cc con tr vo cc hm thnh vin. Tuy nhin, trnhcch din t quanh co ny khi ni v giao din ngi ta thng s dngthut ng con tr giao din thay th. Khi s thc thi giao din n gin

l dng con tr tr ti mng cc con tr ti cc hm. Hnh 6-4 sau minh hacho iu ny.

Giao din IUnknown

Nh trnh by trn, mi i tng COM, khng c s loi tr, u htr giao din IUnknown. Giao din ny c ba phng thc AddRef() ,

Release() v QueryInterface() . Tt c cc giao din khc u dn xut t giaodin IUnknown v u c cc con tr n cc phng thc ny.

Hai phng thc u tnh ton s m tham chiu iu khin thi giansng ca i tng. Khi i tng c to ln u, ta cn gi phng thcAddRef() ca i tng tng s m. Khi khng cn cn ti i tng, tagi phng thc Release() gim s m tham chiu. Khi ngi dng cui

cng gi phng thc Release(), s m gim v 0 th i tng s t hu.

Interface Pointer

pointer

Interface FunctionTable

PointertoFunction1

PointertoFunction2

PointertoFunction3

...

Function1(...){...}

Function2(...){...}

Function3(...){...}

...

Hnh 6-4: S thc thi con trgiao din

Ta c th thy r vn hn qua s thc thi n gin hai phng thc

IUnknown::AddRef() v IUnknown::Release() di y:

//tng bin thnh vin cha s m tham chiu



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ULONG IUnknown::AddRef() {return ++m_RefCount;

}//gim bin cha s m tham chiu, nu bng 0 th hu i tngULONG IUnknown::Release(){

--m_RefCout;if (m_RefCount== 0) {

delete this;return 0;

}return m_RefCount;

}

Khi ta c mt con tr n i tng th thc cht, nhng g ta c ch lmt con tr n mt trong s cc giao din ca n, cn l giao din no

th li ph thuc vocch

m ta c con tr . T con tr vo mt giao din,ta c th truy cp c con tr vo cc giao din khc m i tng h tr.i tng c th hoc khng h tr giao din m ta quan tm, nh ng mi itng u c m bo h trgiao din Iunknown nn ta c th yu cu ccgiao din khc qua phng thc IUnknow::QueryInterface().

Cc giao din c nh danh bi cc IIDs (Interface IDs) v d nhIID_IUnknown ca giao din IUnknown. Khi ta gi phng thcQueryInterface(), ta gi IID ca giao din m ta cn cho n v mt con tr ntham s u ra. Nu i tng h trgiao din yu cu, n s tr li on mbo thnh cng S_OK (nh ngha l 0) v t vo tham s u ra m ta cungcp con tr n giao din yu cu. Nu i tng khng h tr giao din nyn bo li v t tham s u ra l NULL. Ta xt mt s thc thi n ginsau:

HRESULT IUnknown::QueryInterface(REFIID riid , LPVOID * ppv) {//kimtra IID xem i tng c h tr giao din yu cu khng,//nu h tr ta tng s m tham chiu,a vo bin u ra cung cp// mt con tr n giao din, v bo rng thnh cng

if (riid == IDD_IUnknow) {AddRef();*ppv = (LPVOID)this;return S_OK;

}//nu khng h tr giao din ta t bin u ra cung cp l NULL v// tr v mt m thng bo li

else {*ppv = NULL;return E_NOINTERFACE;

}}



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Quan hgia i tng v cc giao din

Cc client ch ktni qua con tr ti cc giao din. Khi mt clienttruy nhp vo mt i tng, client ch n thun thng qua con trgiao din. Con tr giu i ni dung ca thao tc bn trong, ta khng ththy chi tit v i tng m ch c th thy thng tin v trng thica chng. i tng c th thc thi nhiu giao din. Mt lp thc thi i tng

c th thc thi nhiu giao din, v d qua phng php a tha k.

6.4.3 Giao tipgia client v object

Cch thc ca sgiao tip

Trc khi s dng mt i tng COM trong mt ng dng, ta cn khito c ch COM trong ng dng bng li gi CoInitialize(...) v sau to itng COM mong mun. Client kt ni vi object thng qua con tr giao dinv khng bao gi truy nhp trc tip vo object. Khi cn s dng dch v no ca i tng, client hiu rng n cn c con tr n mt hay nhiu giaodin ca i tng. to mt i tng COM v nhn mt con tr vo giaodin, ta c th gi mt trong hai hm CoCreateInstance() hoc

CoCreateInstanceEx() vi cc tham s xc nh i tng.

ClientApplication InterfacePointer

Object

Hnh 6-5: Giao tip gia i tngv khch hng

Trong mt s trng hp, bn thn client s ng vai tr mt object vcung cp cho cc i tng khc nhng chc nng gi cc s kin hoc ara cc dch v ca n. Lc ny client l mt i tng thc thi cn object l

mt khch hng.



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ApplicationObject

Object

Application

Hnh 6-6: Giao tip gia hai itng

Giao tip trn cng m t qu trnh tnh ton

Khi client v i tng COM cng nm trn mt qu trnh tnh ton th

client s kt ni trc tip vi object qua con tr giao din.

Qu trnh client

clientserver

object

Hnh 6-7: Giao tip gia i tngv khch hng trn cngqu

trnh

Giao tip lin qu trnh

Nu client v object khng cng nm trn mt khng gian a ch hay nmtrn cc my tnh khc nhau th COM s thit lp mt i tng i din(proxy) bn pha client v mt i tng gc (stub) bn pha object. Proxy vstub s kt ni vi nhau qua knh giao tip (channel). Khi , client s thchin li gi dch v trong khng gian a ch ca n tc l giao tip trc tipvi proxy. Proxy s thu thp (marshal) cc thng s, gi chng n stub quaknh giao tip. Stub thc hin li gi n i tng dch v, ng gi kt qu

v a v cho proxy.



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Qu trnh clientQu trnh dch v cc bhay t xa

server

proxy Stub object

COMEngine

Hnh 6-8: Giao tip gia i tng v khch hng trn hai qu

trnh khc nhau

6.4.4 Ngn ng m t giao din

IDL (Interface Description Language ) l mt ngn ng kiu mnh dng m t giao din ca i tng COM, c lp vi ngn ng lp trnh. Cphp ca ngn ng ny khng phc tp so vi mt ngn ng lp trnh. Khixy dng mt i tng COM, ta cn m t cc phng thc ca giao dinbng cch s dng ngn ng ny. Sau khi tp xong file m t giao din ny, tacn lu n dng *.idl chng trnh dch c th hiu c. Chng trnh

dch (IDL-Compiler) s dch sang mt ngn ng lp trnh, v d C++. Khi mt giao din s c chuyn sang thc hin bng mt cu trc thch hptrong ngn ng lp trnh, v d mt lp thun o trong C++.

6.4.5 M hnh i tng thnh phn phn tn DCOM

DCOM (Distributed COM) m rng COM cho vic giao tip gia cc itng phn tn, thuc cc chng trnh chy trn nhiu my tnh khc nhautrn mng LAN, WAN hay Internet. Vi DCOM, cc ng dng c th phn tntrn nhiu v tr em li s thun li cho chnh ng dng. Ngy nay khi ngita ni ti COM l cng thng bao hm DCOM trong .

DCOM l mt cng ngh l tng cho nhng ng dng nhiu tng lp biv n cho php nhng thnh phn ActiveX lm vic ngang qua mng. Nhiungi c th pht trin thm cng mt thnh phn m khng cn phi lo lngv lp trnh mng, tnh tng thch h thng hoc s hp nht ca nhngthnh phn xy dng t nhng ngn ng khc nhau. N dn ti h thp gi

thnh v lm gim s phc tp ca vicphn tn cc ng dng thnh phn.



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Khi cc i tng trn cc my tnh khc nhau, DCOM n gin thc

hin s thay th truyn thng lin qu trnh cc b bi giao thc mng. Hnhdi y minh ha r nt cch thc giao tip gia cc i tng nm trn hai

my tnh khc nhau.

Client Proxy Stub Component

CoCreateInstance()SecurityProvider

DCERPCSecurityProvider

DCE RPC

COMRuntime

ProtocolStack ProtocolStackCoCreateInstance()

(Remote)Activation

SCM SCM

DCOMnetwork-protocol

Hnh 6-9: Giao tip gia i tng v khch hng trn hai my

khc nhau vi DCOM

Th vin COM Run-Time cung cp nhng dch v hng i tng tikhch hng v thnh phn mun giao tip vi nhau ng thi s dng RPC vnh cung cp an ton to chun ni mng ng gi tun theo giao thctruyn thng cho DCOM.

Mt ng dng client c th to mt i tng trn mt my tnh khc quahm API CoCreateInstance(). Ta xt mt v d n gin sau:

HRESUL hr = CoCreateInstance(CLSID_CData, // nhdanh lp ca i tng yu cuNULL,CLSCTX_REMOTE_SERVER,// dch v t xa c yu cu&si); // tham s u ra cha con tr giao din



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7 CC M HNH NG DNG IU KHINPHN TN

7.1 IEC-61131

IEC (International Electrotechnical Commissio n) l mt t chc ton cubao gm cc hi ng cc quc gia. Mc tiu ca t chc ny l thc ycng vic chun ho trong lnh vc in v in t.

IEC 61131 l tiu chun v b iu khin kh trnh PLC v cc thit bngoi vi i km vi n. Chun IEC 61131 bao gm 9 phn, trong cc phn1 n 5 l quan trng nht: Phn 1 (General Information ): a ra cc nh ngha chung v cc

c tnh chc nng tiu biu cho mi h thng iu khin s dng PLC,v d c ch thc hin tun hon, nh qu trnh, thit b lp trnh vgiao din ngi-my.

Phn 2 (Equipment requirement s): t ra cc yu cu in hc, c hc

v chc nng cho cc thit b; nh ngha phng php kim tra v thnghim cc kiu thit b tng ng. Cc yu cu c nh ngha l

nhit , m, cung cp ngun, khng nhiu, phm vi tn hiulogic v sc bn c hc ca cc thit b.

Phn 3 (Programming language s): nh ngha cc ngn ng lp trnhcho cc thit b iu khin kh trnh. Ngoi ba ngn ng kinh in lbiu hnh thang (Ladder Diagram , LD), biu khi chc nng(Function Block Diagram , FBD) v lit k lnh (Instruction List, IL), vmt ngn ng bc cao kiu vn bn c cu trc (Structured Text, ST)th mt phng php lp trnh ha phc v biu din cc thut toniu khin trnh t l SFC (Sequential Function Char t) cng cchun ha.

Phn 4 (Guidelines for user s): a ra cc nguyn tc ch o cho ngi

s dng trong cc qu trnh ca mt d n, t phn tch h thng choti la chn thit b, vn hnh v bo tr h thng.

Phn 5 (Communicatio n): cp ti phng php truyn thng giacc PLC cng nh gia PLC v mt thit b khc trn c s cc khihm chun. Cc dch v truyn thng ny m rng chun ISO/IEC

9506-1/2, thc cht l mt tp con trong cc dch v c qui nh

trong MMS.



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FB FB

7.1.1 M hnh phnmm

Mi PLC ti mt thi im bt k ch c mt cu hnh (configuration) no. Mt cu hnh bao gm mt hay nhiu ti nguyn (resource) bn trong

c trng cho kh nng x l tn hiu ca PLC. Mi ti nguyn bao gm tnht mt chng trnh (program) hot ng di s iu khin ca tc v

(task). Chng trnh c xy dng nn t cc khi chc nng (functionblock) hoc cc yu t ngn ng khc (c c thy 5 ngn ng lp trnh cnh ngha trong phn ny). Cc bin ton cc (global variable) v li truycp (access path) l nhng c ch giao tip trong chng trnh v gia cc ti

nguyn vi nhau.

CONFIGURATION

RESOURCE

TASK TASK

PROGRAM PROGRAM

RESOURCE

TASK TASK

PROGRAM PROGRAM

FB FB

GLOBAL and DIRECTLY REPRESENTED VARIABLESand INSTANCE-SPECIFIC INITIALIZATIONS

ACCESSPATHS

Communication function (See IEC 1131-5)

Execution control path

or Variable accesspaths

FB Functionblock

Variable

Hnh 7-1: M hnh phnmm theo IEC 61131-3



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CONFIGURATION C CONFIGURATION D

PROGRAMsend

SEND

rcv1 PROGRAM

RCV

FB1FB_

a

SD1 RD1 FB2FB_b

Hnh 7-4: Giao tip qua khi chcnng

Sau cng, b iu khin kh trnh v h thng khng phi PLC c th

truyn d liu qua li thng qua li truy cp nh biu din trong Hnh 7-5, s

dng cc c ch nh ngha trong IEC 61131-5.

CONFIGURATION C CONFIGURATION DP1

PROGRAMAFB1

FB_X

a Z

VAR_ACCESSCSX: P1.Z : REALREAD_ONLY;

PROGRAMB

TO_FB2

READ

RD1

'CSX' VAR_1

FB2

FB_Y

b

Hnh 7-5: Giao tip qua ng dn truy cp

7.2 IEC-61499

IEC 61499 l tiu chun lin quan n vic s dng cc khi chc nngvi t cch l cc module phn mm trong h thng o lng - iu khin



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phn tn. ng t quan im hng i tng, mi khi chc nng c coi

l mt i tng phn tn vi mt chc nng trong h thng. Chun IEC61499 bao gm 3 phn trong phn 1 l quan trng nht. IEC 61499-1nh ngha kin trc chung ca h thng o lng - iu khin, khichc nng ng vai tr ct li, di dng cc m hnh tham kho. C tt c 8m hnh c nh ngha nh trnh by di y.

7.2.1 M hnh h thng

Chun IEC m t h thng o lng - iu khin qu trnh cng nghip dng mt tp hp cc thit b kt ni li v lin lc vi nhau thng qua mt

hay nhiu mng truyn thng nh trong Hnh 7-6 di y. Cc mng ny c

th c t chc theo th bc.

H thng mng truyn thng

Thit b 1 Thit b 2 Thitb 3 Thitb4

ng dng A

ng dngB

ng dngC

Qutrnh k thut

Hnh 7-6: M hnh h thng theo IEC 61499

Mi chc nng c thc hin bi h thng o lng - iu khin c m

hnh ha bng mt ng dng nh trong hnh v trn. Mt ng dng c thnm trong mt t

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He Dieu Khien Phan Tan