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Ngi bin son: Lm Tng c - Nguyn Kim nh 150

CHNG 7 NHNG NG DNG CA PLC (5 LT)

7.1. ng dng PLC trong lnh vc iu khin robot: V vn robot cng nghip ch yu l cc cnh tay my lm vic trong cc nh my lp rp v sn xut t, m t, ti cc bn cng, kho bi cha hngth PLC c nhng vai tr rt ln. y ch gii thiu n bn c ch yu l cc bn sinh vin tham d cc cuc thi robocon. y l chng trnh thng xuyn t chc hng nm, vic cho robot t ng d theo cc vch trng l ti chnh m rt nhiu bn trong cuc tn rt nhiu thi gian. Sau y ti s a ra mt gii php cc bn tham kho trong qu trnh ng dng PLC vo lnh vc ny. y l m hnh s sn u:

Hnh 1: S sn u v hnh trnh m robot cn phi thc hin Bng 1: M t hnh trnh lm vic ca Robot

S vch 4 5 8 9 10 12 13 16 17 23 24 27 28 29 30

Bnh tri T1 T1 T1 T1 T1 T1 T1 L1 T1 L1 T1 T1 T1

Bnh phi T2 L2 T2

cng thm

1 vch L2 T2 L2 T2 T2 T2 T2 T2 L2 T2

cng thm

1 vch



ch lm vic

chy thng

r phi

chy thng

b bng

r phi

chy thng

r phi

chy thng

r tri

chy thng

r tri

chy thng

r phi

chy thng

b bng

S vch 31 33 36 41 42 43 >43

Bnh tri L1 T1 L1 T1 T1 T1

Bnh phi T2 T2 T2 T2 L2 T2

ch lm vic

r tri

chy thng

r tri

chy thng

r phi

chy thng

ngng & b bng

Ly tp File t ANTN Dng b sung.(S b tr cm bin trn robot; S phn b rng xung; S bm in p; s thut ton ca chng trnh; Chng trnh vit di dng STL).

7.2. ng dng PLC trong h thng sn xut linh hot: Hin nay, ht hng cn bng nh lng c ng dng rt rng ri trong cc

nh my x nghip cng nghip. ni u c s phi trn cc cht theo t l nh trc (bi ton phi liu) th c s tham gia ca cn bng nh lng, c bit l cc nh my ch bin vt liu xy dng, nh my phn bn, cao su... H thng ny c kh nng iu chnh t ng c tng cht ng vi t l t trc da trn c s cc vng lp iu chnh v d PI, PID.

t vn : Lm th no phi liu theo gi tr t trc ca 3 cht clanhke, thch cao, ph gia tng ng l 70%, 20% 10% nghin xi thnh xi mng. Trong tng khi lng cn phi vo my nghin l A tn/h. Ngoi ra, h thng lm vic cn ph thuc vo cn liu hi v u vo ca my nghin (sau khi ra khi my nghin nhng ht c khi lng ln c hi v nh phn ly ng) v in y ca my nhgin. C ngha l lc no h thng

Hnh 2: S cng ngh ca h thng phi liu



lm vic cng phi m bo c yu t u tin l in dy ca my nghin l 80%. Nu lng liu t h thng phi liu a n cng vi liu hi v lm cho in y ca my nghin vt mc 80%B tn/h th h s t ng gim lng liu cung cp n nhng vn m bo c t l phn trm ca bi ton phi liu mc d khi lng xut khng t A tn/h, ngoi ra vng lp iu chnh cn phi nhn bit c s thay i tham s ca Clanhke kp thi iu chnh ph gia v thch cao. S thay i thng s trn thch cao v ph gia l hm bc nht vi bin l clanhke. Nh vy mi bng ti c mt vng lp iu chnh PI vi thng s phn hi l tn hiu tng hp t hai tn hiu ca loadcell v encoder, u ra l gi tr setpoint xung bin tn theo ng USS. Ngoi ra h thng cn lm vic c ch Manual, trong ch ny h thng khng quan tm n lng liu hi v v in y ca my nghin. Nh vy h thng lm vic 3 ch : MN80%B; MN>80%B; Manual. gi s 80% lng liu trong my nghin l 270 tn. C th m t s khi iu khin h thng nh sau:

ng nhin l h thng phi qun l trong gii hn nht nh, nu mt trong 3 bng ti gp s c gi y m lng liu vt mc ngng c t ti u cn bng, lc dng a v vt mc 20mA th h thng s dng lm vic thng qua chng trnh con x l s c. Hoc bt c 1 bng chuyn no cng c gim st trt ai, nu xy ra th chng trnh x l s c cng s c gi. Yu cu phn cng ca h thng:

+ 1 PLC_CPU 226

PID_2 PV CV SP MM4 M

chun ho

Bng ti


chun ho

Bng ti


chun ho

Bng ti A

270 B

Cn liu hi v

in y ca

MN

Manual

B t hp

chuyn mch

Hnh 3: S m t h thng iu khin CBL cho h thng nghin xi mng

Clanhke

Thch cao

Ph gia



+ 2 EM235 Module + 3 Bin tn MM3 hoc MM4 (iu chnh tc 3 bng ti) + 4 Load cell (ly tn hiu v u cn) + 4 u cn (chun ho tn hiu v t 420 mA; ci t gi tr gii hn trn) + 1 Sound Sensor + B cp ng trc ni t RS-485 Port n PLC + 3 Encoder

S u ni h thng nh hnh 2. Qa trnh tnh ton, chun ho, setpoint cho tng vng lp c thc hin nh sau: Bi ton t ra l lm th no tn hiu phn hi v c chuyn sang n v tn/h so snh vi gi tr setpoint. Tnh ti trng Q:

2L.qQ =

Vi: Q: Ti trng im [Kg] q: Ti trng trn bng ti [Kg/m] L: Chiu di tnh ton [m] Cng thc tnh trng lng P trn bng ti theo thi gian :

V.LQ.2V.qP == (*)

Vi: P: Trng lng bng ti theo thi gian [Kg/s] V: Vn tc di ca bng ti [m/s]

Theo (*), tnh q bng cch tnh Q v L bit trc. chun ho q t [01]ta chia q cho qmax ; tnh qmax ta da vo Pmax l gi tr t tng ng vi % ca mi cht v Vmax ca bng ti (da vo tc nh mc ca ng c). Nh vy, tn hiu phn hi v chnh l P [tn/h]. Cn phi tm vn tc V [m/h] v ti trng trn bng ti q [tn/m]. Xy dng cng thc tnh ton tc ca bng ti nh vo Encoder: Gi s chn thi gian tnh ton l 250ms tng ng vi s xung tnh c l x xung Nu ta chn loi encoder c thng s 500xung/vng th sau x xung:

Bnh xe encoder quay c: 500x (vng) tng ng vi gc quay

500x2 (rad).

Sau 1ms bnh xe encoder quay c: 500.250

2 x (rad). Nh vy vn tc gc ca bnh xe l:

5002.

2501.1000 x = (

srad )

Vn tc di ca bnh xe bng vn tc di ca bng ti:

Hnh 3: Mt ct dc ca bng ti



2

.5002.

2501.1000

2. dxdVed

== (sm ) = btV

d: ng knh ca bnh xe: chn d = 0,1 [m]; L=0.5 [m]

xdxVV edbt 086,18500.250.2.1000.3600 === (

hm )

Chun ho v gi tr t [01] tin hnh chia cho Vmax ; tnh Vmax da vo tc nh mc ca ng c. Chun ho v a v u vo CV (Current Value) ca b PID ca PLC:

[ ] [ ]0,10,0q

q0q

q

max

max

max

==

[ ][ ] [ ]0,10,00,10,0.0,10,0V.q

V.qP

P

maxmax

bt

max

=== Qa trnh thc hin c thc hin theo s khi sau:



Cc qu trnh tnh ton ny thc hin trong PLC. tnh Q da vo u vo analog tng ng, ti y ta phi thc hin cc bc ly mu. i vi b PID ta phi c chng trnh khai bo cc tham s cn thit ca b PID lin h chng 3. tnh vn tc V phi s dng b m tc cao... iu khin cc bin tn trong mng dng giao thc USS protocol nh trnh by phn 7.5. 7.3. ng dng PLC trong iu khin qu trnh: Di y l s cng ngh ca h thng phi liu, nghin, phn loi v phn phi xi mng vo trong cc sil. y khng xt n vic iu khin h thng phi liu nh nu trn phn 7.2. Ch thc hin cng vic tng i n gin: Chn sil mun nhp vo thng qua cc van sau: chuyn v tr ca van 3 ng v chn v tr ca van trn mng kh ng 3. Nu chuyn van 3 ng sang bn phi th sil 1 c nhp. Sang v tr gia th sil 1 v sil 2 hoc sil 3, nu van trn mng kh ng 3 ng th sil 2 c nhp, van trng thi m th sil 3 c nhp. Nu van 3 ng chuyn sang tri th sil 2 hoc sil 3, nu van trn mng kh ng 3 ng th sil 2 c nhp, van trng thi m th sil 3 c nhp. Gi s khi ang nhp cho sil 1 (van 3 ng v tr bn tri) m pht hin y th h thng s t ng chuyn van 3 ng sang bn phi nhp cho sil 2 hoc 3 (nu 2 y th nhp vo 3 v ngc li). iu kin khi ng h thng:



Cc sil cha y. Du thu lc cp cho my nghin p sut. Cc bng chuyn khng b trt ai. Sau khi chn sil v kim tra cc iu kin an ton cho vic khi ng, h thng phi c khi ng theo trnh t nh sau: MK2, MK3 MK1 M van Qut ht (lc bi) Gu ti Phn ly ng M van du My nghin BTC BTTG BTCL, BTPG, BTTC. T yu cu cng nh nh trn ta tin hnh thit k chng trnh nh sau:

1. V gin thi gian hoc vit lu thut ton. 2. Tnh chn PLC v module m rng. 3. Phn cng I/O. 4. Quy nh cc nh gim st li, khi ng hoc dng t xa. 5. Tin hnh dch sang ngn ng ca PLC t gin thi gian hoc vit lu

thut ton. 7.4. ng dng PLC trong mng thu nhn d liu t bin tn: iu khin bin tn thng qua PLC ngi ta thng dng cc cch sau:

1. Dng cc du vo/ra s ca PLC, nhng ch thc hin c nhng chc nng n gin nh dng, khi ng, o chiu cn vic thay i thi gian khi ng hc dng, t li tc ...khgn th thc hin c ch ny.

Hnh 5: S cng ngh ca h thng cp liu, nhin, phn loi, phn phi xi mng



2. thay i gi tr setpoint trong iu khin phn hi, mi bin tn mt i 1 u vo analog v 1 u ra analog . Ngoi ra cn phi dng cc du vo/ra s iu khin bin tn.

3. iu khin bin tn qua mng Profibus, i vi loi MM3, MM4 ca Siemens c sn giao din Profibus trn RS458 Port. Nhng i vi nhng ng dng nh th vic thit k mt mng Profibus s a gi thnh ln cao, do khng kinh t.

4. Dng Port 0 ca PLC kt ni ti cc Port ca bin tn, 1 PLC c th u khin ti a 1 mng gm 31 bin tn. Mng ny gi l mng USS. Dng kt ni l im-im. Ta c th iu khin ton b cc chc nng ca bin tn thng qua mng ny, ngoi ra cn cn c th gim st c dng in, in p, tc , hng quay...dc vo cc vng nh m PLC dnh ring cho mn bin tn. Chi ph cho mng ny l thp v ti u nht cho cc ng dng nh v va.

5. Chun iu khin mng bin tn (giao thc USS) Sau y l phng php iu khin mng bin tn dng PLC qua giao thc USS: 7.4.1. iu kin s dng giao thc USS: Th vin lnh ca STEP 7 - Micro/Win cung cp 14 chng trnh con, 3 th tc ngt v mt tp lnh (gm 8 lnh) h tr cho giao thc USS. + Giao thc USS s dng Cng 0 (Port 0) cho truyn thng USS.

S dng lnh USS_INIT la chn Port 0 cho c USS hoc PPI. Sau khi la chn Port 0 cho truyn thng vi chun USS, khng c s dng Port 0 cho bt k mc ch no khc.

pht trin cc chng trnh ng dng s dng giao thc USS, nn s dng CPU 226, CPU 226XM hoc module EM 277 PROFIBUS-DP kt ni n card PROFIBUS-CP my tnh. Cng truyn thng th hai cc loi CPU ny s cho php STEP 7 - Micro/Win gim st c ng dng trong khi s dng giao thc USS. + Cc lnh USS tc ng n tt c cc bit SM vi truyn thng Freeport qua Port 0. + Cc lnh USS s dng 14 chng trnh con v 3 th tc ngt. + Cc gi tr ca cc lnh USS yu cu 400 byte ca min nh V. a ch bt u c n nh bi ngi s dng v phn cn li dnh cho cc gi tr khc. + Vi lnh trong lnh USS yu cu mt b m truyn thng 16 byte. Chng hn vi mt tham s cho lnh, cn phi cung cp mt a ch bt u trong min nh V ca b m ny. + Khi thc hin cc php tnh, cc lnh USS s dng thanh ghi AC0 n AC3. Cng c th s dng cc thanh ghi trong chng trnh; tuy nhin, gi tr trong cc thanh ghi s b thay i bi lnh USS.



+ Cc lnh USS s lm tng b nh ca chng trnh ln n 3450 byte. Tu thuc vo loi lnh USS m dung lng ca b nh c th tng t 2150 byte n 3450 byte.

+ Cc lnh USS khng th s dng trong chng trnh con. * Lu : thay i phng thc truyn thng ca Port 0 tr li PPI truyn thng vi STEP 7 - Micro/Win, cn phi s dng lnh USS _ INIT khc n nh li phng thc cho Port 0. Cng c th nh li phng thc bng cch chuyn S7-200 sang ch STOP, vic ny s Reset cc tham s ca Port 0. 7.4.2. Thi gian yu cu cho vic truyn thng vi bin tn: Truyn thng vi cc MicroMaster (MM) khng ng b vi vng qut ca S7-200. S7-200 hon thnh vi vng qut trc khi mt MM hon thnh vic truyn thng. Cc yu t gip xc nh thi gian yu cu: s MM c trong mng, tc baud, v thi gian vng qut ca S7-200. C vi loi yu cu thi gian tr di hn khi s dng cc lnh truy xut thng s. Thi gian yu cu cho vic truy nhp cc tham s tu thuc loi thit b v tham s c truy nhp.

Sau khi lnh USS _ INIT n nh Port 0 cho giao thc USS, S7-200 s thc hin hi vng tt c cc bin tn trong nhng khong thi gian theo di y.

Bng 2.5: Thi gian yu cu cho truyn thng vi MM Tc Thi gian hi vng gia cc bin tn 1200 240 ms (max) 2400 130 ms (max) 4800 75 ms (max) 9600 50 ms (max) 19200 35 ms (max) 38400 30 ms (max) 57600 25 ms (max) 115200 25 ms (max)

Hnh 2.11: Kt ni PLC v bin tn theo giao thc USS



7.4.3. S dng cc lnh USS: s dng cc lnh trong chng trnh iu khin S7-200, cn phi theo cc bc sau: 1. a lnh USS _INIT vo trong chng trnh v thc hin lnh ny cho mi mt vng qut. C th s dng lnh ny thit lp cc gi tr hoc thay i cc thng s truyn thng. Khi s dng lnh USS _ INIT s c vi n chng trnh con v th tc ngt c t ng thm vo trong chng trnh. 2. Ch thc hin mt lnh USS _ INIT trong chng trnh cho mi Drive. C th a vo nhiu lnh USS_RPM_x hay USS_WPM_x khi c yu cu, nhng ch mt lnh c lm vic trong mt thi im. 3. Cp pht vng nh V cho th vin lnh bng cch kch chut phi (ly t menu) trn Program Block trong cy th mc. 4. Ci t cc tham s v a ch v tc c s dng trong chng trnh cho drive. 5. Dng cp kt ni truyn thng t S7-200 n cc drive.

* Ch : Cc thit b kt ni vi in th khc nhau c th l nguyn nhn sinh ra dng in khng mong mun trong cp kt ni. Dng in ny l nguyn nhn dn n cc li truyn thng hoc lm hng thit b. Cn phi chc chn rng cc thit b c kt ni vi cp u c cng dng in nh mc hoc c cch ly ngn nga dng in khng mong mun. 7.4.4. Cc lnh trong giao thc USS:

4.1. Lnh USS- INIT: Cu trc lnh:

Lnh USS_ INIT c s dng cho php thit lp hoc khng cho php truyn thng vi cc MM. Trc khi bt k mt lnh USS no khc c s dng, lnh USS_INIT phi c thc hin trc m khng c xy ra li no. Khi lnh thc hin xong v bit Done c set ln ngay lp tc trc khi thc hin lnh k tip. Lnh ny c thc hin mi vng qut khi u vo EN c tc ng. Thc hin lnh USS_INIT ch mt ln cho mi s thay i trng thi truyn thng. S dng lnh chuyn i dng to mt xung u vo EN. Khi thay i gi tr ban u cc tham s s thc hin mt lnh USS_ INIT mi.

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