&6 Manh Tuan TrUdng Cao dang Nghe Dau khi Email: tuando.pvmtc@gmail.com Bg dieu khien PID vdi 3 tham sd dieu khien P - proportional -t^le,l- integral - tich phdn, D - derivative - vi ph
Trang 1AP DUNG PHUONG PHAP TINH TOAN THL/C NGHIEM ZIEGLER & NICHOLS XAC 0 ! N H C A C THAM SO CHO BO DIEU KHIEN LUU LUONG DONG TRONG CONG NGHIEP DAU KHI
ThS &6 Manh Tuan TrUdng Cao dang Nghe Dau khi Email: tuando.pvmtc@gmail.com
Bg dieu khien PID vdi 3 tham sd dieu khien (P - proportional -t^le,l- integral - tich phdn, D - derivative - vi phdn) dang dUUc sUdung rgng rdi diduy tri lUu lugng dong va cac thdng so cdng nghe khdc d gid trj cdi dgt tgi cde nhd mdy hda ddu cua Petrovietnam Tuy nhien, di' bg dieu khien Idm viec hieu qud cdn phdi xdc dinh cde tham sddieu khien P,
I, D phu hap
Phuong phdp tinh todn thuc nghiem cde tham sddieu khien P, I, D cua Ziegler & Nichols cho bg dieu khien PID dUn
I gidn, nhanh chdng, hiiu qud vd khd chinh xdc Do do cac thdng sdcdng nghe quan trgng cua nhd mdy dugc kiem sodt
on dinh theo thiet ketgo ra sdn pham cd chdt lucfng cao
TUkhda: Tham so dieu khien, bo dieu khien dong, luu luang dong, PID, cong nghiep dau khi, Ziegler & Nichols
Kjf Lflu Iflpng dong la mdt bien qud trinh eo bdn dnh
hfldng Idn tdi eac qud trinh edng nghe, dac biet vdi nganh
cdng nghiep dau khi ma hau hdt cac nguyen lieu dau vao
^ va san pha'm dau ra hoae la chat Idng, hoae la chat khi,
ji chang han nhu dau thd va xdng/dau tai nha may Ipc hda
dau, nha may phan tach khi, nha mdy dam Khdng chi
nganh cdng nghiep dau khi ma cd cac nganh cdng nghiep
khde eung vay Thdng qua lUu Iflong ddng, ed the dieu
khien duoc ca ve trao ddi khdi Iflpng, trao ddi nhiet va trao
ddi nangIflpng
fdi Trong cae nha may hda dau, Iflu Iflong ddng dflPc sfl
\ dung de dieu khien hau het eae bien qua trinh khac rat
hieu qua.Tfldd kiem sodt cde qud trinh eong nghe dn dmh
de eho sdn pham chat Iflpng cao Vi du: chinh Iflu lupng
ddng vdo vd ddng ra hop ly se gifl dflpc mfle d i u thd trong
bdn d gia trj mong mudn; hoac chinh ddng dau thd va
dong hdi Iflu hop ly se kiem sodt dflOc nhiet dp dinh thdp
chflng c a t d l c d sdn p h i m xang chat Iflpng
Bd dieu khien PID vdi 3 tham sd dieu khien (P
-proportional - t y 1$, I - integral - tich phdn va D- derivative
- vi phan) dang dflpc sfl dung rat rdng rdi trong dieu
khien dieu tiet trong cac nhd may che bien hien dai Bp
tham sd P, I, D quyet djnh chat Iflpng dieu khien eua bd
dieu khien Do dd, can phdi cd phflOng phdp don gidn,
hieu qua de xdc djnh cde thdng sd nay Phuong phdp
tinh todn thfle nghiem cae tham sd dieu khien cP bdn
cfla Ziegler & Nichols cho bd dieu khien PID da dflpc ap
dungthdnhcdng
2 Mo hinh
Md hinh trinh bay he thdng dieu khien Iflu IflOng ddng nfldc bang cde thiet bt/he thdng do Ifldng - tfl dpng
- hda hten trfldng (field instruments), cde thiet bi cdng nghe thfle, gdm cd:
PhflOng tien do Iflu Iflong ddng FT-1: cd cdm bidn la tam orifice, do Iflu Iflpng ddng the ti'ch thfle te, rdi gfli tin hieu tdi bd dieu khien
Bd dieu khien FIC011 kieu PID: nam trong he thdng dieu khien phan tan Centum CS3000 R3/Yokogawa (so sanh tin hieu PVvdiSV,xflly sai lech rdi xuat tin hieu ra MV [manipulated variable - bien thao tae) tdi bp chuyen doi tin hieu dien sang khi nen (l/P transducer))
Van dieu khien kieu khi nen, thfldng ddng: di kem l/P transducer de bidn ddi tin hieu ddng dien 4 - 20mA sang tin hieu khi nen tieu chuan 3 - 1 Spsig de dieu tiet dp
md van dieu khien CV-1 lam thay ddi lflu Iflpng ddng Mdi quan he gifla Iflu Iflpng ddng Q(t) va tdn that dp trong van dieu khien, ma sat dfldng dng va ma sat tam orifice thfldng la he phi tuyen Trong thu'c te, dflpc coi la tuyen tinh bang cdch phan tieh eac bien trong pham vi gidi ban quanh diem van hanh, do vay mo hinh todn hpc dflpc tao ra nhfl Hinh 2
Trong do:
Trang 2K Van (tht/ing ddng), |
IP}:B<m: flC011:Bddiealihienddngc6chllhi: DVSoileehaioPVsovdiSV]
FT-l Phuang tien do luu luang dong; l/P:B6 chuyin Soi dong iien sang kliinin; j
Hinh 1 Luu ddP&ID (thiet bi vd dudng dng) cua he thong dieu khien luu luang ddng
•*•[ P I D j —
-®^
Hinh 2 Sado khoi cua md hinh todn hgc
Cde timgtagff OW LUu tifong ddng (mVs); MV(t) Bien thao lac 1%);
PsgJp sudi bom (mHP): g(t)Q(ll-OlO): m«ll):MV(ll-MV(Oj,
P'sg Psg • Psgm m True cua van chdt tm); PV(t):Bien qua tnnh;
mrJdnhoodptrentdmOri&elmHpi mil) X(tJ-MO): pv(t)-(PVlt) - PV(0)1/SPAN;
m Ton hao dp trin van (mHfi), SV(tl: Bien cai ddi (m'/s), DV(I) Ba lech =PV-SV
CV-He so von dieu khien; SPAN.Daida
cvCV-CV(C), svlt)i5V(lj-SV(0)}/SPAN,
pi7(5) = Gp(s)my(s) -H GaP'sg{s) (2)
(Trong trfldng hpp nay, nhieu he thdng la gia trj ty le eija dau ap
may bom)
Khi P'^g(s) - 0, phflong trinh (2) ed dang:
pv(s) Kpe-h'
Trong dd:
K : Dd Ipi qua trinh; K^ - APV{%)/AMV{%);
L : Dd nhay qua trinh (giay);
T : Hang sd thdi gian (gidy)
3 Xac djnh tham so dieu khi^n PID b^ni phuang phap thUc nghiem cua Ziegler g Nichols
Xdc djnh tham sd dieu khien PID bSnj
phfldng phap thu'c nghiem cfla Ziegler &
Nichols thfle hi^n theo trinh t f l sau:
3.1 Ldy dudng phdn Ung
Dau tien thu thap dfldng phdn flng ciJa doi tflPng dieu khien trfldc tdc ddng dieu khien ]J dfldng do thi the hien sfl thay ddi cua Iflu lUOng
d d n g t r f l d c t h a y d d i d p m d v a n ,
3.2 Tinh cac tham so cua dong qud trinh
Tfl dfldng do thj xac djnh dflpc thude tinh cfla ddng qua trinh the hien qua 3 tham sa
Tfl phflpng trinh (3) suy ra:
P^f^^ = T^'^^f^^' ^'^^('^ = ^ '^'
Tfl Hinh 3, MV[t) dflpc dp dung bdi ham bfldc nhdy don vi khi khdng co nhieu qua trinli hoae qua trinh Id dn djnh Dap flng PV trong Hinh 3 got la "dfldng phdn flng" trong dd thill gian L^ va T^ cd the tinh dflpc bang each k& dfldng a, b va c (Hinh 3) va K^ dflpc tinh tfl ty so gifla sai lech PV va sai lech MV
3.3 Xdc djnh hudng tdc dgng dieu khien (control action direction) cho bd dieu khien
Hfldng tdc dpng cfla bd didu khien IS hfldng thay ddi tin hieu ngd ra trfldc sfl thay ddi cfla bien dflpc dieu khiln
Hfldng thuan (direct): bp dieu khien thay ddi ngd ra cung chieu vdi chieu thay ddi cOa bien dflpc dieu khien
Hfldng nghich (reverse): bd dieu khien thay ddi ngo ra ngfloe chieu vdi chieu thay ddi ciia bien dflpc didu khien
Lflu y: Su tang hay gidm ve bien dp cda MV tuy thudc vao gia tri cua tham sd PID
VI du: Xdc dinh hfldng tde dpng dieu khiln cho qud trinh dieu khien dong vdi van dieu khien dflng khi n^n de md
4 0 DAUKIli-Sd2/2016
Trang 3Tac dong di4u khien
Hinh 3 Duong phdn Ung cualVIVlt) dp dung ham bUde nhdy 3on vi
ing 1 Hudng tdc ddng dieu khien: tdc ddng thuan vd tac ddng nghich
DV=PV-SV
DV = (-H)
DV = (-}
DV = (-h)
DV = (-}
MV
mv t (tang)
mv •!- (giam) mv T [tang)
/
FIC011 100,0%p OPN
CLS 0,0%
PV /
Kp=APV(%) IA MV(%) = (+)
Q(t)
t
-Hinh 4 Qud trinh dieu khien dong bdng von dieu khien dimg khi nen demd
De chpn tdc dpng dieu khien, mpt cO che vat ly cfla qua trinh
dflpc xem xet ehu yeu (Hinh 4) Gid sfl, Iflc bat dau Iflu Iflpng ddng
thfle te (PV) nhd hdn Iflu Iflpng mong mudn (SV)
So dd Hinh 4 cho t h i y , neu tin hieu ngd ra cua bd dieu khien
(MV) tang, dp suit khi nen se tdng de nang true van len va lam tdng
dp md eua van dieu khien khien Iflu lUPng ddng Q{t) va PV tang Tdm lai, khi MV tang, PV tang
Trong trfldng hpp nay, de gidm thieu dp sai lech gifla PV va SV, MV phdi tang Theo gid sfl luc d i u DV - PV - SV < 0, tac ddng nay tflong flng vdi tac dpng nghjch trong Bang 1, khi DV
am, tin hieu MV tdng bdi bd dieu khien Do vdy chpn hfldng tdc ddng dieu khien nghjch cho bd dieu khien
Trang thai Nghich Hfldng mong mudn cfla MV
D V - ( - ) *->• mvT(tang)
Ddi vdi vi du ndy, K^ = APV(%)/AMV(%) < 0 Ndi cdch khae, neu van dieu khien Id kieu dung khi nen de ddng, K se am, tflong ung vdi tde ddng thuan Cach de xdc djnh tde ddng dieu khien la gidng nhflcach cfla vidu 1
Ket luan ve each xdc dmh tde ddng dieu khien Id:
v^ Sfl dyng tac dpng nghjch khi K > 0; v' Sfl dyng tac ddng thuan khi K < 0
3.4 Tinh todn PID
Cac tham sd dieu khien PID dupe ttnh toan bang cdng thfle thfle nghiem cua Ziegler & Nichols (Bang 2)
4 Ket qua thUc hi^n tren he thdng dong qua trinh thUc te
4.1 DUdng phdn Ung
Dflpc ghi lat trong Trend (do thj xu hfldng) cua he thdng dieu khien phdn tan (DCS) vdi chu
ky cap nhat Is
Diem khdo sdt tai Iflu Iflpng ddng = 50%
Ap dung thay ddi bfldc tang dp md van
AMV = 5% (tfl MV^, ^ 44,2% len 49,2%) Lflu
Iflpng ddng thay ddi, tang len vd dn djnh d 56,8% (APV-6,8%)
Phdn flng cfla dong qud trinh trfldc thay ddi dflpc ghi lai tren Trend (DCS) nhfl Hinh 5
4.2 Xdc dinh cac tham sdtUdUdng phdn Ung
Tfl dfldng phdn flng tinh dflpc edc tham sd
Trang 4Bdng 2 Bdng cdng
Oieu khien
P
PI
thuc thuc nghiem detinh toan cac tham so dieu khien PID
P
l O O j K , , ! ^
l l O I K p j ^
1 (s) D(s)
0
3,3 L, 0
83[Kp\
K = A P V / A M V = 6 , 8 / 5 = 1,53 > 0 D o d d phdi d|t
h f l d n g d i e u khidn n g h j c h c h o b p d i e u khien F l C O l l
1^ = 4,1(5)
Tp = 5,6(s)
T i n h t o d n cac t h a m sd didu khien P, I, D (Bang 3)
4.3 Kiem nghidm Igi cde tham sddieu khien
D f l p c t h f l e hten b a n g cdch n a p cde b d t h a m sd P, I,
D c h o t f l n g kieu d i e u k h i e n (kieu P, kidu PI va kidu PIO)
c h o b d d i e u k h i e n lflu I f l d n g FIC011 t h d n g q u a giao diei
t u n i n g D e FIC011 d c h e d p t f l d p n g sau d d dp dung
t h a y d d i bfldc d O n vi ( t a n g ) vdi ASV = 5% T h e o doi va
p h d n t i c h d f l d n g d o t h j d a p flng cua FICOl 1 t f l d d n g d i a
c h i n h M V ( d p m d v a n ) d e dfla Iflu I f l p n g d o n g thfle te l^n
SV m d i
D i e u khien kieu P ( H i n h 8 )
D i e u khien kieu PI ( H i n h 9)
D i e u khien kieu PID ( H i n h 10)
Hinh 7 Chon hudng dieu khien nghich cho bo dieu khien trong database Hinh 10 Dieu khien kieu PID
Bdng 3 Ke! qud Imh todn ede tham sddieu khien
Dieu khien kieu P Oieu k h i l n kieu PI | p i e u khien kieu p i b
P l(s) D(s) \ ' P ' ' "
lQO\Kp\:f-111,7 9999,9
no\K,\f
Ks}
3,3 Lp D(s)
83\K,\:^
I (s) D(s)
2,0 Lp 0,05 Lp
Trang 55 Ket luan
Trong Hinh 8 - dieu khien kieu P: bd dieu khien
khong the dfla dflpc PV (Iflu Iflpng thfle te) ve Iflu Iflpng
mong mudn SV mdi Luon co sai lech (offset)
Trong Hinh 9 - dieu khien kieu PI: bd dieu khien
nhanh chdng dfla dfloc PV ve va on djnh d SV
Trong Hinh 10 - dieu khien kieu PID: bd dieu khidn
rat nhanh ehdng dfla dflpc PV vd SV, nhflng ket qua lai vot
Id tr^n (overshoot) vd vot Id dfldi (undershoot)
Do qua trinh ddng dap flng nhanh, thdi gian tre
khdng ddng ke, nhieu loan chi do rung ddng cfla mdy bom
vd ddng xody, t f l ket qud neu tren rut ra kieu dieu khien
thich hop la PI (ty le - tich phdn ket hpp)
Qud trinh dieu khien phflc tap vd khd cd the phat trien
md hinh toan hpe trong thdi gian ngan Cach don gian
de dieu chinh tham sd tuning cua vdng dieu khien la dp
dung phflOng phdp tinh todn thyc nghiem cua Ziegler &
Nichols PhflOng phdp se hieu qua ddi vdi cac qua trinh co dac tinh gan gidng vdi tre bac nhat
Tai li^u tham khdo
1 Bruce R.Whalen Basic of instrumentation
Petroleum extension Service, division of continuing Education University of Texas at Austin 1983
2 Hoang Minh Son Gido trinh CO sd he thong dieu khiin qud trinh Nhd xuat bdn Bach khoa Ha Ndt 2009
3 J.G.Ziegler and N.B.Niehols Optimum settings for
automatic controllers.Ttam ASME 1942; 64: p 759 - 768
Application of Ziegler & Nichols' experiment method for calculating the parameters for flow controllers
in the petroleum industry
Do Manh Tuan
Petrovietnam Manpower Traing College Email: tuando.pvmtc@gmail.com
Summary
PID controllers with 3 control parameters (P - proportional, I - Integral, and D - derivative) are widely used to maintain flow rate and other variables of various processes at set values in Petrovietnam's petrochemical plants In order to ensure the proper function of these controllers, suitable control parameters ofP, I and D need to be found
The Ziegler & Nichols' experiment method has been applied for calculating the P, I and D parameters for the PID controllers because it is rather simple, fast, effective and correct The critical process variables at the plants have, therefore, been kept stable at setpoints, resulting in the production of high quality products
Key words: Control parameter, flow controller, flow rate, PID, petroleum industry, Ziegler & Nichols