C6-PID Controller Tuning[1]

Chng 6: Chnh nh b iu khin PID

iu khin qu trnh

2Chng 6: Chnh nh b iu khin PID 2006 - HMS

Ni dung chng 6

6.1 Nhng vn c bn6.2 Cc phng php da trn c tnh6.3 Cc phng php da trn m hnh mu6.4 B tr s dng b d bo Smith


Mc ch bi ging

Nm c nhng vn c bn v chnh nh cc tham s P/PI/PID

Nm c nhng phng php chnh nh tham s b iu khin PID thng dng nht trong iu khin qutrnh

C kh nng la chn v p dng phng php phhp vi mt qu trnh thc t


1. Nhng vn c bn

Cc phng php tip cn (tng quan phng php chnh nh)

Vn m hnh i tng s dng Vn la chn kiu b iu khin c tnh cc vng iu khin s dng b iu khin

P/PI/PID ngha ca vic thay i, hiu chnh cc tham s


Cc phng php tip cn

Da trn c tnh ca qu trnh (c tnh thi gian hoc tn s): ZieglerNichols (I v II), phn hi r-le (strm v Hgglund),

Da trn m hnh qu trnh: Tng hp theo m hnh mu (h kn hoc h h): tng hp trc

tip (Chen v Seborg), chnh nh lam-da (Dahlin), IMC (Morari v Zafiriou), xp x c tnh tn,

Nn c tnh tn s (h kn hoc h h): ti u m-un (Kessler), d tr bin-pha (strm v Hgglund,...),...

Ti u ha tham s (theo cc ch tiu IAE, ISE, H,...) Da trn kinh nghim: Chnh nh m, h chuyn gia


Cc m hnh qu trnh thng dng

Bc nht:

Bc hai:

1( ) 1skeG s s

=+

5 2( ) 2 1

skeG ss s

=+ +

'5

1 2( ) ( 1)( 1)

skeG s s s

=+ +

2( )skeG s s

=

4( ) ( 1)skeG s s s

=+

6 2( 1)( )

2 1

sak s eG s

s s

+=+ +

'6

1 2

( 1)( ) ( 1)( 1)s

ak s eG s s s

+=

+ +

7 2( 1)( )

2 1

sak s eG s

s s

+=+ +

'7

1 2

( 1)( ) ( 1)( 1)s

ak s eG s s s

+=

+ +

3( ) 1skeG s s

=

81 2

( ) ( 1)( 1)skeG s s s

= + 9 1 2( ) ( 1)( 1)skeG s s s

=


Qu trnh c ng hc bc cao?

Ba cch tip cn:1. Nhn dng xp x v m hnh bc thp2. Nhn dng v m hnh bc cao, sau xp x v m

hnh bc thp (xp x gim bc)3. Thit k b iu khin bc cao, sau xp x v cu

trc P/PI/PID


Xp x theo phng php Skogestad -Lut chia i (half-rule)

Khi ct b cc thnh phn qun tnh bc cao ca i tng, cc hng s thi gian qun tnh b ct b c cng vo hng s thi gian tr.

Ring hng s thi gian b ct b ln nht c chia i mt na cng vo hng s thi gian tr, mt na cng vo hng s thi gian qun tnh c gi li nhnht.

i vi thnh phn p ng ngc b ct b, hng sthi gian p ng ngc cng c cng vo hng sthi gian tr.


Cng thc xp x

( )( )

( )01

1

1

1

m

in

pjj

zis

k sG s e

s

=

=

+

=+

p1 > p2 > p3

( )1skeG s s

=+

21 2

pp

= +

20

3 12n m

ppj zi

j i

= =

= + + +

( )( )( )1 21 1

skeG s s s

=+ +

31 1 2 2, 2

pp p

= = +

30

4 12n m

ppj zi

j i

= =

= + + +


Cn c chn kiu b iu khin?

c im ca qu trnh v thit b ng hc ca qu trnh ng hc ca thit b o c im ca nhiu o ...

Mc ch, yu cu ca bi ton iu khin Vai tr, c im ca tng lut iu khin

Vai tr n nh h thng? Vai tr trit tiu sai lch tnh? Vai tr ci thin c tnh ng hc? Tnh nhy cm vi nhiu o? ...


c tnh vng iu khin PI(khi tng kc)


c tnh vng iu khin PI(khi tng i)


c tnh vng iu khin PID(so snh vi PI)


nh hng ca thay i tham s PID


Chn lut iu khin cho cc bi ton tiu biu Vng iu khin lu lng: ng hc ca i tng ph

thuc ch yu vo van iu khin, nhiu o cao tn => hu nh ch cn s dng lut PI.

Vng iu khin mc: Qu trnh c c tnh tch phn, php o mc thng rt b nh hng ca nhiu => lut P cho iu khin lng v lut PI cho iu khin cht.

Vng iu khin p sut cht kh: ng hc ca i tng ph thuc ch yu vo thit b chp hnh, qu trnh cng c c tnh tch phn tng t nh bi ton iu khin mc nhng cao hn v chnh xc => Lut PI l ch yu.

Vng iu khin nhit : ng hc chm, php o t chu nh hng ca nhiu cao tn => s dng lut PID.

Vng iu khin thnh phn: Tng t nh vng iu khin nhit => thng s dng PID.


2. Cc phng php da trn c tnh

Ziegler-Nichols 1 (ZN-1): Da trn th p ng qu , cho h s tt dn 1/4, qu iu chnh 25%

Ziegler-Nichols 2 (ZN-2): Da trn c tnh dao ng ti hn (c tnh tn s), cho cht lng tng ng ZN-1

strm-Hgglund (AH) Phn hi r-le: Ci tin cch nhn dng c tnh dao ng ti hn ca ZN-2 (chp nhn km chnh xc hn)

Tyreus-Luyben (TL): Ci tin ZN-2, gim h s khuch i, tng thi gian vi phn v thi gian tch phn => b tham s thn trng hn


Ziegler-Nichols 1


Ziegler-Nichols 21. t h thng ch iu khin bng tay v a dn h

thng ti im lm vic, ch h thng n nh ti im lm vic

2. Chuyn h thng sang ch iu khin t ng vi b iu khin P. t h s khuch i kc tng i b.

3. Tng dn kc cho ti trng thi dao ng iu ha => h skhuch i ti hn (ku) v chu k dao ng ti hn (Tu).


strm-Hgglund (phn hi r-le)

4 /uk d a=


Tyreus-Luyben


V d iu khin thit b trao i nhit1.210.75( ) (30 1)(5 1)(2 1)

seG s s s s

=+ + +

Xp x v m hnh FOPDT theo lut chia i:5.710.75( ) 32.5 1

seG s s

=+


PI

PID


c ti liu (sch v ti liu in t) v cc phng php: Phng php Haalman Phng php Dahlin (chnh nh lamda) Phng php DS (Direct Synthesis) Phng php DS-d (Direct Synthesis with disturbance

rejection preference) Phng php IMC (Internal Model Control) Phng php xp x c tnh tn s (xem thm tp ch

K thut iu khin, 6/2006 v K yu Hi ngh KH 50 nm thnh lp trng HBKHN, phn ban in)

3. Cc phng php m hnh mu


3. Cc phng php m hnh mu

( )( ) ( )L sK s G s =

( ) ( )( ) 1 ( ) ( )K s G sT s K s G s= +

Cho m hnh mu (m hnh mong mun) ca h h/h kn:

( ) ( ) ( )L s K s G s=

( )( ) ( )(1 ( ))T sK s G s T s =

( )( ) ( )L sK s G s

( )( ) ( )(1 ( ))T sK s G s T s

hoc:


Cc vn cn gii quyt Hm truyn t nhn c khng c cu trc PI/PID: Xp

x b iu khin hoc chn m hnh mu v m hnh i tng ph hp

H kn c th khng n nh ni: Chn m hnh mu thch hp, m hnh i tng thng thng khng c im cc hoc im khng nm bn phi trc o

H d nhy cm vi sai lch m hnh: Chn m hnh mu theo hng thn trng

Tm li: Hai vn then cht l chn m hnh mu phhp v phng php xp x m hnh!

Cc dng m hnh mu thng c la chn:

1( ) so

L s es

= ( ) 1

s

c

eT s s

=+ 2

( )2 1

s

c c

eT ss s

=+ +


V d iu khin thit b trao i nhit1.210.75( ) (30 1)(5 1)(2 1)

seG s s s s

=+ + +

Xp x v m hnh SOPDT theo lut chia i:

2.210.75( ) (30 1)(6 1)seG s s s

=

+ +


Kt qu m phng vi lut PID


Ci thin cht lng bng b lc gi tr t(cho trng hp s dng DS-d)


4. B tr vi b d bo Smith

M hnh l tng ca i tng:

Vn : u ra o c b chm tr, nh hng ln ti cht lng iu khin

tng khc phc: D bo u ra khng c tr da trn m hnh

0( ) ( ) sG s G s e =

0( ) ( ) sG s G s e =


4. B tr vi b d bo Smith

0 0 0

0 0 0

0 0 0

0

( )( )

s

s

y y y y ey y y ey y yy

= + + + =

Gi s u ra thc khng c tr l y0:


V d m phng

Chnh nh b PID theo phng php xp x p ng tn s

10

3( ) ( 1)

seG ss

=

+


Nhim v luyn tp nh

S dng SIMULINK v m phng, th nghim cc phng php da trn c tnh

c ti liu v cc phng php da trn m hnh mu, th nghim m phng trn MATLAB

c ti liu i km v s dng 3 chng trnh phn mm nhn c tm hiu luyn tp cc phng php chnh nh khc

Chng 6: Chnh nh b iu khin PIDNi dung chng 6Mc ch bi ging1. Nhng vn c bnCc phng php tip cnCc m hnh qu trnh thng dngQu trnh c ng hc bc cao?Xp x theo phng php Skogestad -Lut chia i (half-rule)Cng thc xp xCn c chn kiu b iu khin?c tnh vng iu khin PI(khi tng kc)c tnh vng iu khin PI(khi tng ti)c tnh vng iu khin PID(so snh vi PI)nh hng ca thay i tham s PIDChn lut iu khin cho cc bi ton tiu biu2. Cc phng php da trn c tnhZiegler-Nichols 1Ziegler-Nichols 2strm-Hgglund (phn hi r-le)Tyreus-LuybenV d iu khin thit b trao i nhit3. Cc phng php m hnh muCc vn cn gii quytV d iu khin thit b trao i nhitKt qu m phng vi lut PIDCi thin cht lng bng b lc gi tr t(cho trng hp s dng DS-d)4. B tr vi b d bo Smith4. B tr vi b d bo SmithV d m phngNhim v luyn tp nh

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C6-PID Controller Tuning[1]