Ngôn Ngữ Lập Trình SFC

Chng 1: Tng quan v ngn ng SFC

1.1 Cc nh ngha v ngn ng SFC Theo Automating With PLCs SFC c nh ngha Sequential Function

Charts (SFCs) are a graphical technique for writing concur-rent control

programs[1]. Sch Programming Manual (SFC) vit: SFC, an abbreviation for

"Sequential Function Chart", is a control specification description format in

which a sequence of control operations is split into a series of steps to enable a

clear expression of the program execution sequence and execution conditions

[2]. Tuy hai ngun c cch din t khc nhau nhng chung quy ta rt ra nh

ngha SFC vit tt ca Sequential Function Chart, l mt phng php lp trnh

c bit kiu ha trong chng trnh s c chia thnh chui cc bc

(step) v iu kin chuyn tip bc(transition condition). SFC thch hp

lp trnh cho h thng c nhiu hot ng xy ra ng thi vi nhau.

1.2 Gii thiu chung v ngn ng SFC SFC l mt trong nm loi ngn ng lp trnh tiu chun c cp

trong phin bn IEC61131-3 c cng b nm 2003. Nm ngn ng c

chun ha l lit k lnh( IL, Instruction List), s tip im (LD, Ladder

Diagram), s khi chc nng (FBD, Function Block Diagram), vn bn c

cu trc (ST, Structured Text) v biu hot ng tun t (SFC, Sequential

Function Chart).

1.3 c im ca ngn ng SFC SFC c bit ph hp vi cc ng dng c th c cu trc thnh cc bc

xc nh r rng. Mch logic trong mt bc c th c lp trnh trong bt k

ngn ng lp trnh khc, ngoi ra SFC cn c mt s c im c bn nh sau:

D lp trnh v sa li chng trnh.

Chng ta c th a cc chng trnh iu khin nguyn mt nh my, iu

khin cc thit b thuc cc trm khc v ton b my mc vo chui cc khi v

bc ca mt chng trnh SFC . Vi cch lp trnh vi ngn ng c dng biu

nh SFC ngi lp trnh c th thy r hot ng ca tng bc trong h thng nn

s d dng hn cho vic k v sa li, nht l nhng ng dng phc tp nh

Hnh 1.1

[ngun: Programing Manual]

Khng cn n mch kha cho phc tp.

Mch kha cho ch c s dng trong s iu khin ng ra cho mi bc. Bi

v khng mt cng tc kha cho no c tc ng gia cc bc vi nhau trong

Hnh 1.1. ng dng ngn ng SFC trong iu khin phc tp

chng trnh SFC. Khi mi bc ca chng trnh SFC c kch hot bi iu

kin chuyn tip, n s xa hot ng ca bc lin trc tr mt s trng hp ta

dng n cc khi c bit.

V d v mch kha cho c cho trong Hnh 1.2.


Hnh 1.2. Mch kha cho trong chng trnh SFC

SFC c s tng ng vi dng lu gii thut trong cch chuyn

t bc ny sang bc khc, ta c th quan st qua v d trong Hnh 1.3

[ngun: PLC Programmable Logic Controllers theory and implementation

Second Edition]

S thit lp cho cc khi v cc bc c th thay i rt d dng cho mt

ng dng mi.

i vi cc loi ngn ng khc nh Ladder hay Instruction List khi ta mun

thay i hay m rng thm cho ng dng th ta c th phi vit li chng trnh

iu khin, iu ny gy bt li nht l nhng dy chuyn nhp khu hon ton

nc ngoi h c th m ha chng trnh khng cho php chng ta can thip.

Tuy nhin vi SFC, ta c th m rng ng dng d dng hn. Bng cch lp

Hnh 1.3 S tng quan gia SFC v Flowchart

trnh theo khi (phn ny n khng cp) th khi thm mt ng dng ta c

th lp trnh ng dng vo mt khi ring ri a vo chng trnh chnh, thng

qua cc iu kin chuyn tip chng trnh s hot ng ng theo ca

ngi lp trnh. C th:

o Tng cng ta c th to 320 khi trong mt chng trnh SFC o Ti a 512 bc c th to trong mt khi o C ti 2000 bc tun t c th to cho ton b cc khi ng ra. o Mt iu kin chuyn tip khc c th c to trong uy nht mt

khi ladder.

C th to nhiu khi m u trong mt chng trnh.

Chng ta c th to mt chng trnh vi nhiu bc m u nh v d trong

Hnh 1.3. Khi c nhiu khi m u c kch hot ( S0,S1,S2,S3) ti bt k

mt bc m c iu kin chuyn tip c tha mn (t4 n t7) th bc S8 s

c thc thi.


Hnh 1.4 Chng trnh SFC vi nhiu bc m u

Chng 2: Cu trc ngn ng SFC

2.1. Cu trc mt chng trnh SFC c bn Theo tiu chun IEC, mt chng trnh SFC bao gm ba thnh phn chnh l:

Cc bc (steps)

Cc s chuyn tip(transitions)

Cc tc ng( actions)

[ngun: PLC Programmable Logic Controllers theory and implementation

Second Edition]

2.2. Cc bc

Mt step biu din mt trng thi trong hot ng ca mt khi chng

trnh vi cc tn hiu ng vo v ng ra c xc nh theo cc hot ng lin

kt ca bc. Mt bc c th c kch hot hoc khng c kch hot. Trng

thi ca cc hot ng trong chng trnh thay i ph thuc vo trng thi ca

cc bc [3]. Mi bc c th c hoc khng c tc ng lin kt vi n. Mt

tc ng lin kt vi bc bao gm dy cc lnh PLC thc hin mt chc

nng no trong khong thi gian bc tch cc. Mt Action c th c lp

Hnh 2.1. Cu trc mt chng rnh SFC c bn

trnh bng mt trong bn ngn ng lp trnh cn li ca IEC61131-3

languages.[4]

Trong SFC, c cc loi bc c bn s c lit k trong cc phn di

y.

2.2.1. Initial steps Initial step l mt bc m u, c k hiu l mt hnh vung nt i. N

i din cho s bt u ca mt mt khi. Trong mt khi chng ta c th thit

k ti a 32 bc m u.

Nu c nhiu hn mt khi m u c kch hot th chng trnh s c thc

thi nu c bt c mt iu kin chuyn tip sau bc m u c tha mn.

Ta xt v d trong Hnh 2.2 sau:

Trong hnh trn, cc bc m u S0,S1,S2,S3 cng c kch hot, nu mt

trong cc iu kin chuyn tip t0,t1,t2,t3 c tha mn th bc S4 s c

thc thi.

2.2.2. Dummy step Dummy step l mt bc m ti khng c chng trnh xut ra ng ra

ca PLC, do Dummy step c th c s dng nh mt bc to tr.

PLC s kim tra iu kin chuyn tip pha sau bc Dummy step tng ng

trong khonng thi gian hot ng ca n v chng trnh s x l bc tip

theo khi m iu kin chuyn tip c tha mn.

Dummy step s tr thnh mt step khi m ta to cho n mt chng trnh xut

d liu.

Hnh 2.2. Thit k chng trnh vi nhiu khi m u

2.2.3. Coil Hold Step Mt Coil HOLD step l mt step m ti cun dy c duy tr in

khi chng trnh chuyn qua bc khc.

Trong chng trnh SFC bnh thng khng s dng Coil Hold Step, trng thi

ON ca tip im cun dy s t ng chuyn sang trng thi OFF ngay sau khi

diu kin chuyn tip ti bc khc c tha mn. Ta c th thy r hot ng

qua Hnh 2.3.

[ngun: Programming Manual]

Hnh 2.3. bc n khi X1c tc ng th cun dy Y10 c cp in, khi

chng trnh chuyn qua bc n+1 th cun dy Y10 mt in v tip im

cun dy Y10 ti bc n+1 khng chuyn trng thi (vn trng thi off).

Bng cch thit k mt bc ng ra theo cch s dng Coil HOLD step,

tip im thng h ca cun dy s c tc ng li khi chng trnh ang x

l bc k tip.Ta phn tch Hnh 2.4 v Hnh 2.5 sau:

Hnh 2.4. bc n khi X1c tc ng th cun dy Y10 c cp in, tip

im Y10 ca cun dy bc n+1 ang thng h.

Hnh 2.3. Hot ng ca mt bc bnh thng


Hnh 2.5. Khi chng trnh SFC chuyn qua bc n+1 tip im Y10 chuyn

trng thi sang ON d X1 chuyn sang trng thi OFF.


Hnh 2.5. Hot ng ca Coil Hold Step

Hnh2.4. Hot ng ca Coil Hold Step

Khi trng thi ON ca cun dy c duy tr trong bc k tip, cun dy s

b mt in trong cc trng hp sau:

Khi chng trnh thc hin bc End( ngoi tr trng hp SM327 ang

ON)

Khi lnh iu khin chng trnh SFC(RST BLm) thc thi mt lnh END

cng bc ti khi ang x l.

Khi m thit b to tn hiu cho khi START/END ca chng trnh SFC

b reset.

Khi m bc reset c chc nng reset bc Coil Hold Step c kch

hot.

Khi m thit b iu khin chng trnh SFC START/STOP (SM321) b

tt.

Khi cun dy trong bc Coil Hold step b reset bi cc lnh trong

chng trnh.

Khi lnh STOP c thc thi.

2.2.4. Operation Hold Step (without transition check) Operation Hold Step l bc m ti hot ng xut tn hiu ng ra ca

bc Operation Hold step vn tip tc sau khi chng trnh chuyn qua bc

k tip. Tuy nhin, chng trnh s khng chuyn qua bc k tip nu iu kin

chuyn tip qua bc c tha mn mt ln na. Ta quan st hot ng ca

Operation Hold Step (without transition check) qua Hnh 2.6 v Hnh 2.7 di.

Khi chng trnh SFC khng s dng Operation Hold Step (without transition

check), trng thi ON ca tip im cun dy ( c kch hot bi lnh OUT ) s

t ng chuyn sang OFF trc khi chng trnh SFC chuyn qua bc k tip.

Khi s dng Operation Hold Step (without transition check) th trng thi ng ra

ca bc ny s c gi khi chng trnh x l sang bc tip theo.

V vy khi tn hiu ng vo thay i th trng thi ca tip cun dy cng thay

i theo.


Nh trong Hnh 2.6 trn ta thy khi chuyn t bc n sang n+1 th

trng thi ng ra ca bc n l tip im cun dy Y10 khng thay i, khi

trng thi ca tn hiu ng vo cp cho Y10 l X1 chuyn t ON sang OFF trong

bc n th sau khi chuyn qua bc n+1 trng thi ca Y10 cng thay i

theo.

Hnh 2.7. Sau khi chng trnh x l sang bc tip theo s khng c s kim

tra iu kin chuyn tip t bc Operation Hold Step (without transition check)

sang bc k tip na, v vy s khng c s chuyn bc xy ra khi iu kin

chuyn tip c tha mn mt ln na. Chng trnh s thc thi bc k tip

nu iu kin chuyn tip ca bc c tha mn.

Hnh 2.6 Hot ng ca Operation Hold Step


Bc Operation HOLD step (without transition check) s b mt tch cc khi

mt trong nhng trng hp sau xy ra:

Khi bc END ca khi c thc thi.


cng bc ti khi

Khi m bc Operation HOLD step b reset bi cc lnh iu

khinchng trnh SFC( RST BLm\ RST Sn). ( ngoi tr trng hp

SM327 ang trng thi ON)


b reset.

Khi m bc reset bc Operation HOLD c kch hot

Khi m rle (SM321) iu khin chng trnh SFC START/STOP b a

xung mc OFF

2.2.5. Operation Hold Step (with transition check) Operation Hold Step l bc m ti hot ng xut tn hiu ng ra ca

bc Operation Hold step vn tip tc sau khi chng trnh chuyn qua bc

k tip. Tuy nhin, chng trnh s vn chuyn qua bc k tip nu iu kin

chuyn tip qua bc c tha mn mt ln na (c kch hot li).

Hnh 2.7. Qu trnh chuyn tip

Trong chng trnh SFC bnh thng th trng thi ON ca tip im cun

dy (c kch hot bi lnh OUT) s t ng chuyn sang OFF trc khi

chng trnh SFC chuyn qua bc k tip.

Khi s dng Operation Hold Step (with transition check) th trng thi ng

ra ca bc ny s c gi khi chng trnh x l sang bc tip theo.

V vy khi tn hiu ng vo thay i th trng thi ca tip im cun dy

cng thay i theo. Ta c th quan st s thay i ca cun dy Y10 theo X1

qua Hnh 2.8 di


Nh trong hnh trn ta thy khi chuyn t bc n sang n+1 th trng

thi ng ra ca bc n l tip im cun dy Y10 khng thay i, khi trng

thi ca tn hiu ng vo cp cho Y10 l X1 chuyn t ON sang OFF trong bc

n th sau khi chuyn qua bc n+1 trng thi ca Y10 cng thay i theo.

Sau khi chng trnh x l sang bc tip chng trnh s kim tra li

iu kin chuyn tip t bc Operation Hold Step (with transition check) , do

khi iu kin chuyn tip ca bc c tha mn li th chng trnh s

quay li bc va x l v thc thi n. Nu iu kin khng tha mn th

chng trnh mi thc hin bc k tip.

Hnh 2.8. Hot ng ca Operation Hold Step


Bc Operation HOLD step (with transition check) s b mt kch hot khi mt

trong nhng trng hp sau xy ra:

Khi chng trnh thc hin bc End( ngoi tr trng hp SM327 ang

ON)


cng bc ti khi ang x l.


b reset.

Khi m bc reset c chc nng reset bc Coil Hold Step c kch

hot.

Khi m thit b iu khin chng trnh SFC START/STOP (SM321) b

tt.

Hnh 2.9. S chuyn tip ca Operation Hold Step

(with transition check)

2.2.6. Reset Step Reset Step l bc m ti mt bc c chn s b xa kch hot mt

cch cng bc. Ngoi ra bc reset cn c th dng reset cc tn hiu ng ra

nh trong cc dng ngn ng khc.


Khi lp trnh mt s phn mm v d nh GX-Deverloper nu mun reset mt

bc xc nh ta s th t ca bc mun reset vo Reset, khi bc Reset

c kch hot step 3 s b reset.

2.2.7. Block START Step (with END check) Block START Step (with END check) l bc m ti khi c xc

nh bi bc s c bt u, khi chng trnh thc thi bc END ca khi

ny th chng trnh s kim tra iu kin chuyn qua bc khc.

Khi bc Block START Step (with END check) c kch hot, chng

trnh s cho php khi m c thc thi.

Chng trnh chnh s khng thc thi bt c mt hot ng no trong khi

khi m ang c x l.

Khi chng trnh x l trong khi m gp bc END th chng trnh s

ch kim tra iu kin chuyn tip.

Khi iu kin chuyn tip c tha mn th chng trnh s x l sang

bc tip theo.

Hnh 2.10. Hot ng ca bc Reset


[Ngun: PLC Programmable Logic Controllers theory and implementation 2nd

ed][4]

Hnh 2.12 cho ta thy hot ng ca chng trnh khi gp Block START Step.

Ta c th thy r l chng trnh chnh s r nhnh qua thc hin chng trnh

trong Block m. Sau khi chng trnh thc thi xong cc Bc trong Blockm

mi chuyn v chng trnh chnh v kim tra iu kin tip tc.

Hnh 2.11. Hnh dng Block START Step(with END check)

Hinh 2.12 Hot ng x l chng trnh khi gp bc Block START Step(with END check)

2.2.8. Block START Step (without END check) Block START Step (without END check) l bc m ti khi c xc

nh bi bc s c bt u, trong lc chng trnh ang thc thi cc bc

trong khi th iu kin chuyn tip vn c kim tra.

Khi c kch hot Block START Step (without END check) s cho php

khi m c hot ng.

Sau khi khi m hot ng, iu kin chuyn tip t bc m sang

bc k tip l xung tc ng cnh ln X0 s c kim tra.


Nu iu kin chuyn tip c tha mn th chng trnh s chuyn qua

bc k tip m khng cn ch cho ti khi khi m kt thc.

2.2.9. END Step END Step l bc m ti tt c s hot ng ca khi b dng li.

Hot ng ca bc END nh sau:

Khi bc END c kch hot cc hot ng sau s c x l kt

thc hot ng ca khi:

o Tt c cc bc trong khi b mt kch hot o Cun dy c cp in bi lnh OUT tt c b mt in

Hnh 2.13. Hnh dng Block START Step

(without END check)

2.3. S chuyn tip Qu trnh chuyn tip l thnh phn c bn ca mt khi, sau khi PLC

thc hin xong cc lnh trong phn tc ng gn vi bc, PLC s thc hin mt

s chuyn tip ri mi thc thi bc k tip. Mt iu kin chuyn tip l iu

kin tin hnh thc hin cc bc tip theo sau khi iu kin c tha

mn. Mt chuyn tip c th ly t cc tn hiu ng vo c s thay i, kt qu

ca tc ng bc k trc hay l kt qu mt php so snh (e.g.,

IFTemp_1100 trong Hnh 2.1).[4]

Mt s loi chuyn tip c cho trong Bng 2.1

Bng2.1. Chc nng mt s chuyn tip

Loi Chc nng tng loi

Serial transition Khi iu kin chuyn tip tha mn, bc tip theo c

thc hin, v tng t cho cc bc sau .

Selection transition

(branch/coupling)

- Mt nhnh ra hoc vo vi nhiu iu kin chuyn tip.

- Trong s nhiu iu kin chuyn tip, bc tip theo s

c thc hin ni iu kin chuyn tip tha mn.

Parallel transition

(branch/coupling)

- Thc hin tin hnh nhiu bc t mt bc duy nht.

- Khi cc bc tc thi trc khp ni c thc thi,

bc tip theo cng s c thc thi khi cc iu kin

chuyn tip thng thng tha mn.

Jump transition Khi iu kin chuyn tip tha mn, s tin hnh thc thi

cc bc quy nh trong cng mt khi.

2.3.1. Serial transition Serial transition l qu trnh chuyn i ni tip, trong s x l v tin

hnh cc bc ngay di bc hin ti, khi cc iu kin chuyn tip tha mn.

.


Qu trnh chuyn i ni tip c ti a 512 bc trong mi

khi. V vy cng c 512 qu trnh chuyn i ni tip c m t.

Tuy nhin , c mt s hn ch v s lng cc dng nh ch ra trong hnh 2.15

di y. ph thuc vo cc hin th ct SFC.

Hnh 2.14. V tr ca Transition


Khi chng trnh SFC hin 1 hoc 2

ct th:

- S bc(dng) ti a l 1536

- S chuyn i ni tip ti a l 512

Hnh 2.15. S lng cc bc v iu kin chuyn tip trong mt khi ca chng trnh SFC

Hnh 2.15. cho ta thy trong mt chng trnh SFC, s c ti a 32 hot ng

song song (32 ct) v khi trrong khi s c s lng cc bc tnh theo cng

thc trn.

Bng 2.2 lit k s dng tng ng ti a vi s ct ca SFC

Bng 2.2: S lng cc dng v cc ct trong mt khi ca mt chng

trnh SFC

S ct hin th S bc hin th ti a tng ng

1 hoc 2 1536

8 384

16 192

22 138

28 108

32 96

2.3.2. Selection transition

Selection transition l s la chn chuyn tip, trong x l song song

cc iu kin chuyn tip. iu kin chuyn tip nhnh no tha mn th bc

tip theo ca nhnh c thc hin.

Ta xt s la chn r nhnh v la chn ghp ni theo Bng 2.3 sau:

Bng 2.3: S hot ng ca cc iu kin chuyn tip

R

nhnh

T bc n s x

l thc thi bc

n+1 hoc n+2

thng qua hai iu

kin chuyn tip

b hoc c tng

ng.

Nu c 2 iu kin

chuyn i c

tha mn ng thi,

th iu kin bn

tri s c u tin.

Bc n s ngng

hot ng.

X l cc bc

cng nh cc iu

kin c tin hnh

tip tc trong tng

ct cho n khi gp

mt khp ni song

song.

Ghp

ni

Khi cc iu kin

chuyn i b hoc

c c tha mn

th cc bc thc

thi [A] hoc [B] s

b ngng hot ng.

Bc n+2 s

c thc thi.

S c ti a 32 bc c sn la chn chuyn i.


Khi hai hoc nhiu iu kin la chn chuyn tip tha mn, th iu kin tn

cng bn tri c u tin.

V d: hnh 2.16 Khi iu kin chuyn tip c, d, e cng tha mn th

chng trnh SFC s u tin chn bc n+2 thc thi trc tin.

Hnh 2.16: S lng cc bc c th chn la trong mt khi


Trong mt qu trnh la con chuyn i, s la chn ghp ni c th c b

qua bi mt chuyn i nhy, hoc chuyn i kt thc.


Ch : Trong mt qu trnh chuyn i c chn lc, s lng chi nhnh v s

lng ca khp ni c th khc nhau.

Tuy nhin, mt chi nhnh la chn v khp ni song song hoc mt chi nhnh

song song v la chn khp ni khng th c kt hp.

Hnh 2.18. Chuyn tip nhy bc

Khi iu kin chuyn tip b tha

mn th bc n+1 c thc thi,

sau tip tc kim tra chuyn tip

v thc thi cc bc pha di, cho

n khi iu kin chuyn tip d

tha mn th thc thi chuyn tip

nhy n bc n.

Hnh 2.17: La chn bc u tin

2.3.3. Parallel transition Parallel transition l s qu trnh chuyn tip song song. Trong cc

bc lin kt song song c thc thi ng thi khi iu kin chuyn tip tha

mn.

Bng 2.4. S hot ng ca cc iu kin chuyn tip

R

nhnh

T bc n nu iu

kin chuyn tip b

tha mn th s thc

hin ng thi bc

n+1 v bc n+3

iu kin chuyn

tip c tha mn th

thc hin bc

n+2, cn d tha

mn s thc hin

bc n+4

Ghp

ni

Khi iu kin chuyn

tip b, c tha

mn th bc n,

n+1 ngng hot

ng v thc thi cc

bc ch i.

Bc ch i c

s dng ng b

ha song song. Khi

iu kin chuyn tip

d c tha mn

cc bc ch i,

chng trnh s tin

hnh thc thi bc

n+2.

Bc ch i l bc

gi lp (dummy

steps) vi yu cu

khn c u ra hot

ng

C ti a 32 bc x l ng thi cc chuyn i song song.

Hnh 2.19: S bc ti a c th la chn


Nu khi khc c bt u bng cc hot ng x l song song, khi ngun bt

u khi v bt u khi im n s c thc thi cng mt lc. Trong v d

di bc n+1 s c thc hin ng thi vi khi 1.


Khp ni phi c s dng khi cn ti cc cc bc thc thi v iu kin

chuyn tip song song. Chng trnh c to ra khng th khng c khp ni.

Hnh 2.21: Chuyn tip song song

Theo quy nh, mt bc ch i phi c to ra trc khi thc hin

khp ni. Tuy nhin, trong trng hp nh v d di y ca cc ct qu trnh

chuyn i song song bao gm ch c 1 bc (chng trnh m khng cn mt

iu kin chuyn tip gia cc qu trnh chuyn tip song song chi nhnh v

khp ni), mt bc ch i khng cn thit.

Hnh 2.20. Thc thi khi v bc

Khi iu kin chuyn tip

b tha mn sau khi thc

hin bc n, th bc

n+1 v khi 1 s c

thc thi ng thi. Sau

khi 0 v khi 1 s c x

l ng thi.

Hnh 2.22: Khp ni song song


2.3.4. Jump transition Jump transition l mt chuyn tip nhy, mt chuyn tip c quy nh

trong cng mt khi, bc ny c thc thi khi iu iu kin chuyn tip tha

mn.

Hnh 2.23: Chuyn tip ca bc nhy


hnh 2.23. khi iu kin chuyn tip b tha mn th bc n s ngng hot

ng, chng trnh chuyn qua thc hin bc m.

Khng c hn ch v s lng ca qu trnh chuyn i nhy trong mt khi duy

nht.

Trong cc nh dng chuyn tip song song, ch c th nhy theo hng thng

ng tng chi nhnh.

Chng 3: Lp trnh bng ngn ng SFC vi PLC

ca Mitsubish Mt s dng PLC ca hng Mitsubishi cho php lp trnh vi ngn ng

SFC, tuy nhin cng c mt s dng khng h tr. Khi lp trnh ta c th chuyn

i sang ngn ng khc m PLC h tr. Cc dng PLC Mitsubishi cho php lp

trnh vi ngn ng SFC [xem ph lc 1]

3.1. Ngn ng SFC vi PLC ca Mitsubishi Ngn ng SFC l ngn ng quc t c chun ha, do cc nh sn

xut PLC khi s dng SFC lp trnh cho PLC ca h u phi theo chun ca

ngn ng v i vi hng Mitsubishi cng khng ngai l. Tuy nhin khi ng

dng mt ngn ng chun vo th nh sn xut vn c mt s t thay i.

i vi PLC Mitsubishi ngn ng SFC c mt s ty chnh cc bc

thc thi. Mt v d c th l khi lp trnh bng phn mm GX Developer, phn

ng ra v iu kin chuyn tip c lp trnh ring trong 1 ca s khc. Cn i

vi mt s phn mm khc nh: phn mm CoDeSys, phn mm RSLogix 5000

th phn xut d liu ng ra, iu kin chuyn tip c lp trnh lin k vi

khi chc nng tun th theo ng ngn ng SFC. [ph lc 2]

3.2. Trnh t lp trnh bng ngn ng SFC Trnh t lp trnh bng ngn ng SFC c th chia thnh cc bc cc bc

c bn sau

Bc 1: T yu cu ca h thng cn lp trnh, ta tin hnh xc nh s u vo

v u ra. Mi lin h gia cc u vo v u ra ny.

Bc 2: Xc nh s bc, s iu kin chuyn tip, cc hot ng cng lc,

hot ng theo trnh t, lin tc hoc gin on

Bc 3: Tin hnh lp lu gii thut, t lu gii thut ta tin hnh lp

trnh chi tit trn phn mm.

3.3. Trnh t PLC thc hin cc bc trong chng trnh SFC

Ta xt v d Hnh 3.1


Chng trnh SFC s thc hin mt chui cc cng on, bt u t bc u

tin, sau thc hin bc tip theo khi iu kin chuyn tip c tha mn,

v kt thc vi bc END.

C th:

Khi chng trnh SFC c bt u, chng trnh s chy bc trn cng

u tin( bc kim tra iu kin khi ng)

Chng trnh c thc hin bc u cho ti khi iu kin 1 c tha

mn. Khi iu kin 1 tha mn, hot ng ca bc u s b dng li, v

chng trnh s thc hin bc tip theo.

Hot ng ca chng trnh SFC tip tc t bc ny qua bc khc theo

cch nh trn cho ti khi bc kt thc END c thc hin.

Hnh 3.1. Cu trc mt chng rnh SFC c bn

3.4. Chuyn i ngn ng SFC sang dng ngn ng khc Ngn ng SFC c th chuyn i sang cc dng ngn ng khc, tuy nhin

s chuyn i khng phi chuyn i hon ton. Trong v d Hnh 3.2 ta s xt

cc bc chuyn i mt chng trnh vit bng ngn ng SFC sang ngn ng

Ladder.

V d 3.1: Chng trnh SFC iu khin cho mt my dp

Nguyn l hot ng ca my:

Nhn nt Start, nu nt nhn automatic c nhn tip th chng trnh s

bt ngun cho my dp v n bo sng. Khi cm bin xc nh vt phm, ba

dp s c y xung v chm cng tc hnh trnh hn di. Khi gp cng tc

hnh trnh hn di, ba dp c nng ln li cho ti khi gp cng tc hnh

trnh hn trn, v ba dp s dng hot ng.

Mt nt nhn dng khn cp c thit k c th dng chng trnh khi

ba dp ang hot ng. Khi chng trnh hoat ng xong mt chu trnh, mt

nt reset c tc ng trc nt automatic. Sau bc th 6 chng trnh s ch

cho vt phm c ly ra ri mi chuyn qua bc khc.

Hnh 3.2: Chng trnh SFC iu khin my dp

[ngun: Automating With PLCs]

Chng trnh SFC c th chuyn i trc tip qua dng Ladder logic theo cch

sau:

Phn u chng trnh Ladder s bt u vi mt bc khi ng cc trng

thi v cc iu kin. Mt iu kin bt u s qut ton b cc bc v iu

kin trong chng trnh SFC.

Phn tip chng trnh ladder l kim tra iu kin chuyn tip c tha

mn hay khng. Nu iu kin chuyn tip c tha mn th bc hoc iu

kin chuyn tip k tip c kch hot v iu kin chuyn tip ban u b xa.

Sau khi mi bc c xt v chng trnh logic chuyn qua bc khc,

Vic quan trng tip theo ca vic lp trnh l kim tra v thc hin cc thao tc

xut tn hiu ra ng ra thc hin cc thao tc.

Chng 4: Nhng ng dng ngn ng lp trnh SFC y ta s dng phn mm GX-Developer lp trnh [ph lc 3 ]

4.1. Chng trnh SFC iu khin hai n sng theo gin

thi gian Hnh 4.1

Yu cu: S dng SFC lp trnh cho hai n sng theo gin thi gian Hnh

4.1. Trong gin thi gian, Plight_1 sng trong 1s trong khi Plight_2 ang tt,

sau Plight_1 trong 1s ng thi lc ny th Plight_2 sng . mt nt Start v

mt nt Reset c thit k nh trong Hnh 4.1. Khi nhn nt Reeset th c hai

n u tt. Mch cn bao gm mt n bo ngun (Light_EN) s sng sau khi

nhn Start v ch tt khi nhn nt Reset.

Hnh 4.2 Gin thi gian hot ng ca cc nt nhn v n

Hnh 4.1 Gin thi gian hot ng ca hai bng n

Bng 4.1 cc thit b ng vo ng ra trong ng dng 4.1

Loi a ch thit

b Tn thit b Hot ng

INPUT

X0 ST: Start Nt khi ng

X1 Reset Nt Reset

T0 T1 timer

T1 T2 Timer

OUTPUT

Y0 Plight_1 iu khin n 1

Y1 Plight_2 iu khin n 2

Y2 Plight_EN iu khin n bo ngun

Chng trnh lp trnh bng phn mm GX-Deverloper(xem ph lc 4)

4.2 iu khin bng ti Cho mt h thng gm c 2 thng hng, 1 cnh tay robot gp sn phm, 3

bng truyn di chuyn sn phm. Thit k h thng theo yu cu sau:

Thng hng 1 c sn phm, cm bin X5 nhn bit c sn phm th cnh

tay robot gp hng a ln bng truyn 1.

Cm bin X0 xc nh c sn phm, bng truyn 1 hot ng, sn phm di

chuyn v chuyn tip qua bng truyn 2.

Plight_1=False

Plight_2 = False

START

2

TRUE

Reset

Reset

Light_EN(R) 3

Plight_1 = ON

Plight_2 = OFF

Light_EN(S)

4 Plight_1 = OFF

Plight_1 = ON

NOT Reset

1

T1 = 1s

T2 = 1s

Hnh 4.3 Chng trnh SFC iu khin hai bng n

0

Cm bin X1 xc nh sn phm, bng truyn 1 ngng hat ng, bng

truyn 2 hot ng, sn phm di chuyn xung bng truyn 3.

Cm bin X2 xc nh sn phm, bng truyn 2 ngng hot ng, bng

truyn 3 hot ng a sn phm vo thng hng th 2.

Kt thc 1 chu trnh lm vic, v bt u 1 chu trnh mi, h thng s

ngng hot ng khi thng hng 1 ht sn phm.

Vi cnh tay robot c a ch Y7, cm bin xc nh cnh tay robot khi

v tr thng hng 1 l X5, bng truyn 1 trn cao l Y0, cm bin u bng

truyn trn cao l X0, bng truyn 2 l Y2, cm bin u bng truyn 2 l X1,

bng truyn 3 l Y4, cm bin u bng truyn 3 l X2, cm bin vt th vo

thng hng 2 l X3.

Hnh 4.4. H thng bng ti

[ngun:phn mm FXTRN-BEG-E]

Bng 4.2. Chi tit ng vo v ra

Loi a ch thit b Tn thit b Hot ng

Input

X0

Cm bin Nhn bit sn phm

X1

X2

X3

X4

Output

Y0 Bng truyn 1

Di chuyn sn phm Y2 Bng truyn 2

Y4 Bng truyn 3

Y7 Cnh tay robot Gp sn phm

Hnh 4.5. Biu hot ng ca chng trnh

Chng trnh lp trnh bng phn mm GX-Deverloper [ ph lc 5]

4.3 ng dng SFC lp trnh cho h thng trn nguyn liu Qu trnh hot ng:

H thng trn nguyn liu c nhim v trn hai khi A v B cha cc

nguyn liu rn vi mt khi lng cht lng tng ng bao gm cht lng A

v B . Mt nt khi ng(ST) c th la chn ch hot ng iu khin bng

tay hoc t ng iu khin qu trnh o lng v trn nguyn liu bt u

START

Tay Robot N Y7

Bng 1 N Y0

Bng 2 N Y2

Bng 3 N Y4

X3 = 1

X2 = 1

X5 = 1

X0 =1

X1 = 1

vi s hot ng cng lc ca hai nhm thit b l bng ti vn chuyn v hot

ng cn khi lng.

Qu trnh nh sau:

Loi cht lng A s c cho chy vo mng C vi khi lng l a, sau

cht lng B cng c cho vo mt lng c khi lng l b, qu

trnh ny c kim sot bi cn WC.

Hai khi cha nguyn liu rn c bng ti a vo bung trn.

Sau khi kt thc hai qu trnh a nguyn liu rn v van VC m cho

cht lng vo bung trn th motor my trn s lm vic, sau mt thi gian trn

c t l t1, qu trnh trn kt thc, motor MP c nhim v nghing bung

trn sn phm i ra. Khi bung trn ht sn phm, motor MP s a

bung trn v v tr xc nh bi S0, v motor MR hot ng li.

Hnh 4.1. S h thng trn nguyn liu

Chng trnh SFC iu khin hot ng ca h thng trn nguyn liu

Hnh 4.1. Chng trnh SFC iu khin qu trnh trn nguyn liu

START N DONE

Weigh A N VA BRICK 1 S MT

Weigh B N VB

FILL N VC

DROP 1

BRICK 2

DROP 2

MIX S MR

TIP N MP1 S1

R MT

RAISE R MR

N MP0 S0

S1

T_MIX >= t1

WC = WA+Z

WC >= WA+WB+ Z

ST & S0 & WC

Ti liu tham kho

[1] Automating With PLCs,

[2] Programming Manual (SFC),

[3] IEC 61131-3 Programmable controllers - Programming languages,

[4] Luis Bryan & Eric Bryan. PLC Programmable Logic Controllers theory and

implementation Second Edition.

MC LC Chng 1: Tng quan v ngn ng SFC ......................................................................................1

1.1 Cc nh ngha v ngn ng SFC .................................................................................. 1

1.2 Gii thiu chung v ngn ng SFC ............................................................................... 1

1.3 c im ca ngn ng SFC ........................................................................................ 1

Chng 2: Cu trc ngn ng SFC ..............................................................................................6 2.1. Cu trc mt chng trnh SFC c bn ........................................................................ 6

2.2. Cc bc ..................................................................................................................... 6

2.2.1. Initial steps ................................................................................................................7

2.2.2. Dummy step ..............................................................................................................7

2.2.4. Operation Hold Step (without transition check) ..............................................10

2.2.5. Operation Hold Step (with transition check) ....................................................12

2.2.7. Block START Step (with END check) ...............................................................15

2.2.8. Block START Step (without END check) ..........................................................17

2.2.9. END Step ................................................................................................................17

2.3. S chuyn tip ........................................................................................................... 18

2.3.1. Serial transition ........................................................................................................19

2.3.2. Selection transition ..................................................................................................21

2.3.3. Parallel transition .....................................................................................................25

2.3.4. Jump transition ........................................................................................................28

Chng 3: Lp trnh bng ngn ng SFC vi PLC ca Mitsubish .............................................29 3.1. Ngn ng SFC vi PLC ca Mitsubishi ..................................................................... 29

3.2. Trnh t lp trnh bng ngn ng SFC........................................................................ 29

3.3. Trnh t PLC thc hin cc bc trong chng trnh SFC ......................................... 30

3.4. Chuyn i ngn ng SFC sang dng ngn ng khc ................................................ 31

Chng 4: Nhng ng dng ngn ng lp trnh SFC .................................................................37 4.1. Chng trnh SFC iu khin hai n sng theo gin thi gian Hnh 4.1 ............... 37

4.2 iu khin bng ti .................................................................................................... 39

4.3 ng dng SFC lp trnh cho h thng trn nguyn liu ............................................... 42

Ti liu tham kho.....................................................................................................................46

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Ngôn Ngữ Lập Trình SFC