Bo Thi Mil vd Dig Tgp chi KHOA HOC & CONG NGHE 169(09). 63- GIAI QUYET BAI TOAN CAN BONG
TRONG M O HINH HE T H O N G CAN BANG DINH LtTONG
Do Thi Mai*, Duong Chi'nh Cuotig VQ Tbach Duong, Do Van ChuySn Trudng Dgi hgc Cong ngh? thong tm vd truyen thdng ~ DH Thai Nguyin TOM TAT
Xii ly tin hieu tuong ty la mgt ph4n kien thiic can ban khdng the thieu trong cac he th6ng digu kiu^n va ty ddng hda, bdi vl thong tin trgng thai ciia qua trinh dieu khien dupc phan ^nh thdng qua cam bien cd tin hieu hoac so, hogc tuong ty DSy la mdt phan kien thirc nen tang co ban va la yeu cau bSt buoc doi vdi sinh vien nganh Cdng nghp ky thuat dieu khign va tu dgng hda khi tdt nghiep Trong bii bao ndy, phuong phap xii ly tin higu tuong tu tir cam bien ygng lugng (Loadcell) duoc de xuat va iing dung yong mo hinh hg thdng c3n bSng dmh lugng tgi phdng Thyc hanh Ty dong hda nSng cao-Trudng BHCNTT&TT Bai toan c3n ddng da duoc xay dyng va thur nghiem tren he thdng c5n bSng dinh lugng co 03 bang tai, dgi dign cho 03 nguyen ligu khde nhau. Qua trinh thir nghipm su dyng phuong phap trich mlu do va dam bao sai sd trong dai cho phep.
Tir khoa: cdn bang djnh lugng; xu ly tin hi$u tuang ty; cdn dong.
DAT VAN DE
Ghep noi cdc thiet bi cap trudng vdi PLC vd xii ly tin hieu tir phdn anh trgng thdi cua doi tupng dieu khien la khau quan trong bac nhat trong hp thong dieu khien vd gidm sdt. Nhu chiing ta biet, tin hieu ngo ra cam bien dupc phan chia thanh hai dgng co bdn. tin hipu so va tin hieu tuong tu. Doi vdi cdc tin hipu tuong ty, vipc xii Iy thong tin dien ra phirc tgp hon nhieu so vdi van de xii ly tin hieu sd. Dgc bi§t, can phai chii y tin hieu dau ra cam bien thupe dgng chuan cdng nghipp, hay chua chuan cdng nghipp, dang dp hay dang ddng de cd the ghep ndi vdi PLC.
Mdt trong sd cdc cam bien tuong ty xii dyng rat phd bien hipn nay la Loadcell Linh vyc ling dyng cua Loadcell chii yeu trong cdc hp thdng can noi chung va he thdng can bdng dinh luong ndi neng.
Trgn the gidi, hp thdng can bang djnh lupng da va dang la m$t phan khdng the thieu trong cac day chuyen sdn xuat ty dpng : khai khoang, sdn xuat xi mang, luyen kim, dieu ch^ dupc, che bien thyc pham...
Hipn nay d nude ta, viec ap dung h% thong can bang dinh lupng vao trong san xuat moi chi bd hpp d trong khau tiep lieu, trpn lipu d
Tel: 0966 643949, Email- [email protected] vn .
cac nha may xi mang, cac day truyen san xuat gdl XI mang ty dpng, tram tron be tong tu ddng. Hau het quy trinh cong nghe deu dupc chuyen giao tir cac qudc gia cd nen cong nghiep phat trien tren the gidi Vai trd ciia ky su ngdnh Tu dpng hda Id lap rdp, bdo tri, bdo duong, vgn hanh he thdng.
Nhan thay ITnh vuc iing dung rpng Idn vd vai trd cua xii Iy tin hieu tuang ty trong he thong can bang dinh lugng trong thyc te sdn xuat, nhdm nghien cuu ciia Khoa Cong nghp Ty dpng hda - Trudng Dai hpc Cdng nghp thdng tin va truyen thong da tien hanh n^ien ciiu, thiet ke va che tao mo hinh h§ thong can bang dinh lupng cho Phdng thyc hanh Ty dpng hda nang cao. Myc dich chinh cua vipc xay dyng mo hinh he thdng can bang dinh luong Id de phuc vy cho cdng tdc gidng dgy, nghien ciiu khoa hpc ciia gidng vien, hpc t^p cua sinh vien, va nang cao nang lye thuc hdnh giiip sinh vien cd thi tilp xiic vdi mo hinh thyc te ngay khi cdn ngdi tren ghe nha trudng. Dac bipt, md hinh nay duoc xay dyng vdi chi phi thap va da bd sung them cdc trang thiet bi thyc hanh lien quan den xu Iy tin hipu tuong ty trong he thdng dieu khien qua trinh.
H$ T H O N G CAN B A N G DINH LU'ONG ' Can dinh lupng Id mpt khai niem chi viec sir
dyng cdc phuong phap do ludng vd xir ly ket qua do nham xac dinh chinh xac khdi lupng
D6 Th] Mai vd Dtg Tap chi KHOA HOC & CONG NGHE 169(09)163-68 cua mpt doi tuong hogc mpt nhdm ddi tuong
cung ban chat khdi lupng. Tiiy tiieo tinh chat chuyen dpng cua ddi tupng can xdc djnh khdi luong trong qua trinh cdn md bdi todn can bang dinh lupng chia ra thanh "can dpng" vd
"can tinh",
Trong md hinh he thdng duac nhdm tac gid xay dyng, bdi todn can bang dinh lucmg dupe dua ra gidi quyet la bai todn can dpng lien tuc.
Bdi toan can ddng dupc md td nhu tren Hinh I.
Hinh 1. Sa dd md hinh he thdng vd thugt todn Nguyen ly hoat ddng (Xem minh hoa tren Hinh I): qua trinh can dpng phai dam bdo tinh lien tye cua ddng chay vat lipu khi me thii I dmh lupng xong, thi ngay lgp tiic van tiep lieu silo ddng Igi, bang tdi can se dirng lgi de chuyen sang budc trpn lipu. Me tiep theo se dupc tien hanh can ngay sau khi trpn lieu xong, Qua trinh hoat dpng lap Iai cho den khi nhan dimg hp thdng.
Nhu vgy, khi bat dau me thii 2 sS tdn tgi mpt khdi lupng nguyen lieu tren bang tdi. Khdi lupng nguyen lipu nay thyc chat la thupe me thii 1, nhung do viec tat truyen dpng bdng tdi ddng thai vdi viec khda van tiep hpu silo nen sd lupng nguypn heu AP nay chua do vdo tilling trpn. Me thii I se bi thieu hut mot lupng AP nhung tir me thii 2 khoi lupng nguyen li$u tdng se duoc bu mpt lupng AP tir me 1.., nhu vay he thdng se hoat dpng dn dinh tir me thii 2.
So dd dieu khien vdng don thuan tiiy dupc mo ta nhu tren Hinh 2 [5],
Cac ky hipu sii dung trong bdi bdo bao gom:
W: Trpng lupng (weight); I: Hien thi (Indication) R: Ghi chep (Record); A: Bao ddng (Alarm) C: Dieu khien (ConhoI).T: Truyen, phat (Transmit)
- K J ^
r-xs: X )
Hinh 2. Sa do dieu khien qud trinh Cdc budc tiin hdnh:
Cdc npi dung tien hdnh nhu sau, Npi dung 1: Thiet ke va thi cong hp thdng tmyen dpng ca khi tren ca sd mo hinh hda hp thdng can bang dinh lupng [6];
Npi dung 2: Thiet ke vd lap dgt hp thdng dien, he thong dieu khien;
Npi dung 3: Lap trinh dieu khien h^ thdng;
Npi dung 4: Hodn thien va test hp thdng.
Bai bao nay tiip trung trinh bdy van de xii Iy tin hipu tuong tu trong PLC S7-1200, ddng thdi dua ra mpt phuang phap gidi quyet bai todn can dpng cd the ung dyng 1dm tdi lieu hoc tgp cua sinh vien ciing nhu img dyng thyc te vdl sai so nam trong gidi hgn cho phep.
Bdi todn ySu chu ddi vdi xu /j5 tin hi^u tuong tu - Hien thi gid tri khdi lupng vat lipu thuc te cdn dupe tgi mpi thdi diem
Thiet bi sA dting:
- Loadcell vdi tin hipu ngo ra Id tin hipu tuong ty dgng dipn dp tu 0 - 3 mV. Ddi can cua Loadcell la tir 0 - 1 0 0 Kg:
- PLC S7-I200: sii dyng module CPU 121IC DC/DC/DC, cd tich hop san I4DI/I0DO; 2 ngo vao tuong ty;
- Bp khuech dgi, dua tin hipu dau ra Loacell ve dgng chuan cdng nghiep (0-IOV), de tin hipu tiep tuc dupc xii ly trong module AI ciia PLC S7-I200,
Mgch khuech dgi do chinh nhdm tdc gid nghien ciiu vd thiet ke duac hinh dung dudi dang so dd khdi nhu mo ta tren Hinh 3.
D 6 T h i M a i v a £ ) ( ^ Tap chi KHOA HOC & CONG NGHE 169(09)'63-68
I Nguin 12 VDC j = ^ Nguon 5 VDC
KI161 khuech d ^ i d i f n ^
Hinh 3. Sa dS khdi bg khuich dgi + Phan ngudn: cung cap ngudn 12V, -t-/-5V cho cac Iinh kien trong mach cung nhu cho loadcell,
+ Phan tien khuech d^, in hieu ddu ra cua loadcell (Sig+ va Sig-) dupc khuech dgi vi sai qua IC chuyen dung AD620, sau do tin hieu dau ra ciia IC chuyen dyng ndy dupc chia thanh hai nhanh de dua vdo hai bd khuech dgi ddng va khuech dgi dp.
+ Phan khuech dai dp, ddng dien' su dung IC LM358
+ Phan tinh chinh sai sd lech: chinh sai sd Ipch (offset) cua loadcell "ve diem khong"
trudc khi van hanh he thdng
Vi tri lap dat toan bp cac linh kien dien tii tren mach khuech dai sau khi thi4c ke tren ban ve ed so do mo phdng nhu tren Hinh 4,
Hinh 4. Mo phong 3D cua mgch khuech dgi sau thiei ki
Xtr L t TIN HIEU TUONG TIT TRONG PLCS7-1200
Dp xu ly tin hieu tuong ty tren PLC, chimg ta can xdc dinh,
- Logi cam bien dau ndi vdi PLC (cam bien sd/cdm bien tuong ty;
- Dgng tin hieu dau ra cdm bien (dgng ddng dipn/ dien ap; miic tin hipu chuan cong ng^ipp/hay khcng chuan cong nghiep) - Module tin hipu ciia PLC ghep ndi vdi cam bien tuang ung
- Cdc chan tin hipu ngo ra cdm bien (cam bien 2/3/4/5 day; cdch thiic dau ndi vdi module tin hipu cua PLC tuong iing)
Nguyen ly chung cho vipc ghep ndi va chuyen doi tin hieu giua cdm bien tuong ty vd module AI cua PLC dupe the hien nhu tren Hinh 5,
r ^
Hinh 5. Sa do khoi chuc ndng edm bien vd module analog
Tuy vao logi module xii Iy tin hieu tuong ty AI ciia PLC va loai cdm bien sii dyng ma ta cd cac gia tri chuyen ddi integer khac nhau. Doi vdi PLC S7-1200, gia tri chuyen ddi cd dupc nhu trong bang I,
Bang 1. Dmh dgng du li^u ddu vao/ra vd gid tri chuyen doi trong PLC Djnh dgng dit lieu Gid tri chuyen doi Kieu tin higu ddi xumg -27648 den 27648 Kieu dtt lieu bat doi xiing 0 den 27648
1
1
< :;^c^
'.
Y WilB<ON/0FF)stS.
1 ^ fV
Hinh 6. Sa do mgch ngo vdo luang lv- ket n ngo ra dien dp
Eac{+)B6 Sie(+)Xanhlacly E)(c {-) Ben Sig {-) Trang Hinh 7. Sa do mgch Loadcell - Ham xii ly tin hieu tuong tu trong PLC S7- 1200 [2]
Bdi cam bien sii dyng Id unbipolar sensor. Do vdy tin hieu dupc xii ly trong AI la don cyc;
tin hipu dang dien dp khi di vao module analog ciia PLC se duoc chuyen ddi thanh dii
Dd Thi Mai vd Dtg Tgp chi KHOA HOC & CONG NGHB 169(09). 63- heu dgng integer cd ddi gid tri nam tir 0 -
27648. Qua hai ham xii ly tin hi§u tuong ty ciia PLC S7-1200 la ham NORM_X va ham SCALE_X, chuyen ddi sd nguyen interger do thanh gid tri dien dp dau vao AI tuong irng.
Toan bp phan xii Iy tin hipu tuong ty duoc dgt trong mpt khdi FCI,
- Cac budc tien hanh xii ly tin hipu tuong tu trong chuang trinh ciia PLC S7-I200 [1]
+ Tgo Project + Chen thiet bi phan cimg + Cau hinh phan ciing + Cau hinh dia chi mang + Cau hinh ngo vdo tuong ty
+Xdc dinh dia chi ngd ^ ^ tuong ly dupc sii dyng + Xac dinh dia chi nhan dgng p h ^ ciing ciia ngd vdo tuong tu
+ Download hardware xuong hp thong thyc de nhan dgng phan ciing
+ Lap trinh xii ly tin hieu tuong tu + Go online
+ Download chuong trinh (software) + Chay chuong trinh
UNG DUNG Bu&c 1: Ghep ndi thiit hi
Thdng qua cdc so dd mach tgi Hinh 6,7, ciing vdi nguyen tdc ghep ndi cdc thiet bj dipn, dipn tli, ta cd dupe so do ghep ndi thiet bi cam bien - mgch khuech dai - ngd vdo tuong tu AI (PLC) nhu ti^en Hinh 8.
t!4\'DC -2JVDC
!
HUJ -'i
Hinh 8. Sa do ddu noi Budc 2: Cdn chinh gid tri Gain vd Offset cua bp khuich dai
Budc 3: Md hinh hoa doi tuang [4]
-Thu thgp dir lieu
Bdi todn can dpng dupc gidi quyet thdng qua phuong phap dinh lupng thuc nghipm; sii dyng phuong phdp do gian tiep (gia tri diu ra
cua loadcell Id gid tri dipn dp tiiong img vdi gia tri khdi lupng vat lieu tren bang chuyen). ^ De giai quyet bdi toan can dpng, nhdm tdc gij da sii dung vat mau. Vgt mau Id vat rdn, hinh khdi chir nhat, mgt dp khoi luong dan deu theo die tich, Tdng khdi luong vat mllu M_mau = 5,873 kg (bao gom cdc vgt mau nho cd khdi luong 655g; 770g; 695g; 7I0g; 765g;
780g; 760g),
Chieu ddi bang tdi L=2m; vat mau dupc trai deu tren chieu dai bang tai nhu tren Hinh 9,
W
Hinh 9, Sado biiu thi phdn bo vgt mdu tren bdngchuyeii Chieu chuyen dpng theo chi4u miii ten Vi tri Loadcell dat tai giQ'a bang tai. PhU'O'ng ph^p.
nr Iy tm hieu do la phLPCng phap trich mlu do.
Tien hdnh lay mau 3 lan, moi lan tir 15-20 diem do vdi chu ky lay mau khac nhau, tin hieu dau ra ciia Loadcell Id gia tri dien ap tuong img vdi khdi lupng vdt lipu tren to^
bp chieu ddi bang tai. Can chu y rang, gid tri khdi luong vat lieu tren bang chuyen dupc tinh toan hodn todn dua vao cac gia tri thvc nghipm thdng ke trung binh, khdng dieu khien dn djnh tdc dp dpng co, khdng dieu khien ddng md analog ddi vdi van silo, Thdi gian lay mau tinh theo ms; tin hipu dien dp dau ra Loadcell cd don vi la mV, Sau khi qua bp khuech dgi, dua vao xu ly qua module AI cua PLC S7-1200, sd lipu ve gia tri dipn dp (V) ihu dupc tai dau vao module AI cua PLC tuong iing vdi timg khodng thdi gian idy mau khde nhau dupc tiinh bdy nhu trong bang 1,2,3, Dii lipu trong Bang 1. 2, 3 tiid hipn gia tri dien dp tire thdi md loadcell do dupc tai timg thdi diem Tir bang du lipu thyc nghipm co the tiiay dupc gia tri dipn dp nho nhat V__min=
0,1540799 (V), gia tri dipn dp Idn nhat V_raax= 0,1976314 (V), tuong iing vdi kh6i lupng vgt lipu dao dong trong khoang tii 1,540799 kg dpnl,9763I4kg,
D6 Thi Mai vd Dtg Tgp chi KHOA HOC & CONG NGHE 169(09); 6 3 - 6 8 Bang 1. Gid tri di$n dp Ihu dugc tuong img then gian lay mdu At = 500 ms
t. t| ta ta U ts U U ts U(t) 0,18193 0,1920573 0.166739 0.18193 0,1833767 0.1898872 0,1848235 0,1783131
U(t) 0,1663773 0.18193 0.1920573 0.166739 0,18193 0,1833767 0,1898872 Bang 2. Gid trj di^n dp thu dugc tucmg ung thai gian lay mdu Al = 200 ms
U(t) 0,1844618 0.1775897 0,1841001 0.1739728 0.18193 0.1786748 0,1761429 0,172526 tio
U(t) 0.162037 0,1685475 0,1848235 0,187717 0,1910359 0.1912274
U(t) 0,1942274
Bang 3. Gid trj di$n dp thu dugc tuang ung then gian lay mdu At = 100 ms
t, tl t2 h U tj te t7 U(t) 0,1656539 0.1540799 0,1576968 0.1602286 0,1605903 0,1616753 Q.1750579
U(t) 0.1790365 0.1844618 0,1779514 0.1801215 0.1718027 0.162037 0.1696325
t. tis tis
U(t)
Gid tri tnmg binh dien dp tinh todn doi vdi timg khoang lay mau rieng bipt dupc the hipn nhu trong bang 4
Bang 4. Gid tri dien dp trung binh
0M2SZ11 0,1786748 0.1801215 Md hinh todn hoc ve gia tn trung binh khdi luong vdt lipu tren bang chuyen Id tuong thich, ddp ling yeu cau.
Tin hi§u dau ra ciia Loadcell di vdo bp khuech dgi. Tin hieu tir bp khuech dgi di vdo module analog ciia PLC S7-1200 cd ddi dipnaptir(a-10)V
Budc 4: Tinh todn gid trf khoi lugng v$t lieu can dugfc theo thdi gian
Khdi FCI dupc gpi ra trong khdi "cyclic interrupt"- OB30 thyc hipn tuan hodn vdi chu kyAt= 100ms [3].
Bdi khdi lupng can dupc bdi Loadcell tgi thdi diem bat ky chinh Id gid tn khdi lupng nguyen lipu tren toan bd chieu dai (L=2m) bdng tdi.
Theo thyc nghiem ta cd:
-Cai dat bien tan dieu khien tdc do dpng co d tansdf=IOHz.
-Thdi gian chgy het chieu ddi bang tdi d tan sd dd Id 70s,
-Gid tri dipn dp ra trung binh Uib_oui 0,17627958 (V), tiic tiiong duong vdi M_i. - 1,7627958 Kg, Ma khdi lupng tiiyc te vat lieu tren bang tai la M_^^^ = 5,873 kg => hp sd dieu chinh:
500 n 200 ms
Uu, 0,1746 0.184136 0.170103 Gid tri dlpn ap trung binh ddi vdi todn bp cac diem do thu dupc:
U,b_o«t = 0,17627958 (V)
Phdn tich du heu vd ddnh gid md hinh ddt tucmg Do thi sai sd giira gia tri do vd gid tri trung binh
Do thj sai l$ch giu'a gia trj trung binh v& gii trj do
U(lill) udW) U(tMl ^ — U ( t l K )
Hmh 10. Do thi sai lich giira gid tri 'rung binh vd gid tri do
Tu bang dir lipu tiiyc nghipm (Bang 1,2,3) va dd tiii sai Ipch giua gid tri do trung binh vai gid tti do tiiyc te (Hinh 10) => gia tri sai sd Idn nhat thu dupc: A = 2,22%,
Do Th] Mai vd Dtg Tap chi KHOA HOC & CONG NGH5 169(09) 6 3 - k = M_^,u/M_L = 3,32
=> Khdi lupng tinh tiieo mpt chu ky tiiyc hien ciia khdi OB30:
m l _ c h u k y = 8 , 3 6 10-' Tdng khdi lupng vgt lieu tiiu duoc tai thoi diem bat k y . M I _ T O N G Id gia tii cong ddn khdi lupng vgt lieu tren bang chuyen sau moi chu ky tiiyc hi^n khdi OB30. Khdi OB30 dupc gpi thyc hipn trong khoi OB I.
M 1 _ T 0 N G = M I _ T O N G + ml_chuky Bdi khdi lupng M I T O N G tiiu dupe tai mpi tiidi diem khong tiie'chinh xdc bang vdi khdi lupng can can ma phai cd mdt sai so cd the chap nhgn dupc. Bdi vay ta can tim gidi han tren vd gidi han dudi cho M I _ T 0 N G . Khdi OB30 xii ly theo chu ky 100ms, bdi vgy.
- Gidl hgn dudi Limit_L = M_setpoint - m l _ c h u k y
- > Limit_L = 5.873 - 8,36,10'' = 5,86464 (kg) - Gldl hgn tren Limit_H = M_setpomt + m l _ c h u k y
=> Limit_H = 5,873 + 8,36,10"^ = 5,88136 (kg)
=> sai sd tuong ddi nhan duoc:
e = (8,36.10-^5,873)* 100 = 0,1423%
=>Tdng sai so tuong ddi nhdn dupc A = 0,1423 + 2,22 = 2,3423 % Nhu vgy A < 5%, nam trong gidi hgn cho phep.
K E T LUAN
Trong bdi bdo nay, nhom tac gid da trinh bay mpt phuong phdp gidi q u y l t bdi todn can dinh lupng sir dyng p h u a n g phdp trich mau do (3 day chiing tdi lay mau vdi 3 chu ky trich mau khac nhau. moi chu ky trich mSu lay tir 15 den 20 diem, Ddy la mpt dang ciia phucri^
phdp xdc xuat thdng ke, Ddi vdi phuong phap ndy, sd Ian lay mau cdng nhieu, thi gia tri ket qud trung binh d u a ra cdng chinh xdc. Trong bdi Viet tdi, chung toi se dua ra mpt danh gia cu the hon niia ve m o hinh toan hoc ma minh xay dyng, bao g d m co danh gia sai so sau, loai bd sai sd sau, xay dyng ham phdn phoi, vd danh gia lai tinh t u o n g thich ciia mo hinh todn hoc sau khi logi bd sai sd sdu, thyc hien dieu khien t u a n g t y vdi van silo cap Heu.
T A I L I E U T H A M K H A O 1 Siemens (11/2009), Simatie S7-1200 easy boolc manual. Siemen AG
2 Siemens (02/2002). Trainning document, Module B2 Analog value processing, Siemen A(^B 3 Siemens (02/2002). Trainning document.
Module B4 Data blooks. Siemen AG. ^ 4 B. B. Ka^iapoB (1971), Memodbi KudepnemUKU B xuMiiu u xuMuiecKoii mexHojioziiu M,
«XHMHa».
5 HoSng Minh Son (2009), Diiu khiin qud Irini^
NXB Bach khoa Ha NOi.
6 S Aleksandrovio, M Jovic, Conveyor bell scale realization using ihe microcontroller. T&L 07/04 7. Ashawim Bhiungade (2015), Automation of conveyor using PLC. Technical Research organization India.
S U M M A R Y
S O L V I N G D Y N A M I C B A L A N C I N G T A S K IN T H E M O D E L O F Q U A N T I T I V E j B A L A N C I N G S Y S T E M
Do Thi Mai*, Duong Chinh Cuong Vu Thach Duong, Do Van Chuyen University of Information and Communication Technology - TNU Analog signal processing is an essentia! requuement knowledge for the students of automation confrol engmeenng. The status of autiomation control system is always reflected by digital or analog sensors Therefore, it is necessary to process the analog or digital signal in the practical control system This paper presents the analog signal processing method of loadcell using m the quantitative balancing system of Automation Laboratory - Thai Nguyen university of Information and Comunication Technology. Practical test on the weighing system including three materials is earned out to check the vadility of the proposed method
Keywords: quantitative balancing system, analog signal processing, dynamic -weighing.
Ngdy nhdn bdi: 01/3/2017; Ngdy phdn bi$n: 11/4/2017; Ngdy duyit ddng: 30/9/2017 Tel: 0966 643949. Email- dlmai(a)ictit.edii.vn
