2. TOPI
CS
- Pr
ocess Cha
racter
isti
cs
- Contr
oller Behaviors
- PT
D Tuning Architecture
- PID
Tuning
(
Ziegler Nichols
tuning
- Open-Loop Method
method
)
- Closed-Loop Method
- Trial and Error
3. Process Characteristics
- Self l
l
e
g
ulating Process
- - - - -v
,....--,r - - - -MV
Process variable tr
end int
o
desired of Manipulated variable
and keep stability
- I
ntegrating Process
PV
Pr
ocess va
riable tr
end i
nto
de
si
r
ed of Manipul
at
ed v
ariable
but does not keep stabilit
y s
uch
as on-
off co
ntr
ol
MV
4. ' '
Controller Behaviors
- P Con
tro l ler
( Propor t ional , Cont rol l er G
a i n )
J
P contro l Ier wi 11 increase the
s ignal by m
ul t iply the signa l wi th
cont rol ler gain va lue.
'
. C
ootrol L
or Goin ol'rc-
.ct
I
'
'
5. Controller Behaviors
- I Control
ler
( Integr at ing, ReseL Tim
e )
J
Icontro l Ier wi 11 increase the
s ignal response for reach to
desi red vaIue.
6. ' '
' '
Controller Behaviors
- D Cont ro l le 1
· ( Der ivat ive, Rate Tim
e )
J
Dcontro l Ier wi 11 increase the
s igna l response and decrease
before reach to des ired va Iue,
this act ion wi l l decrease s ignal
dam
pi ng.
'
-
.'
7. PID Tuning
Bef
ore Tu
n
in
g
- Understood in the control philosophy
- Understood in hardware and contro
l
.
l
e
d environment
- Whal i s target of tuning?
Tuning
- Consider process cha
racteristic
- Select contr
ol method P, Pl, PD or PID
- Select tuning method Open-Loop, Closed-Loop or Trial
and Error
- Roughly tuning ( Tuning criteria )
- Fine tuning
8. PID Tuning
- Consider process characteristic
Change process se t-poi nt or M
V value of the control ler and
m
on itor process variable change ( PV Graph ) unt il process in to steady
sta te, PV graph wi l1 ind ica te process parameters that. usef ul for
ident i fy proper ly contTol method for the process.
.
'
'
•
' .
Se t-goint : .'
.,'
"
•• PV
' .
'
MV
-.
_
_
__
_
_ .;,..._..,. .._--------
-
" . .
'--- - .-.-· - - - - - - - - - - - - - -"
°TIM
E
/
' '
" .
,,_,.....
_
,
' , •
1
l'roco..
"ti
°"'"d Till&'
( L, )
Tiii!? c0f1
s l an t
( T, )
9. PIO Tuning
- Select control method
Cons ider D
ead t i m
e and Process t im
e cons tant ra t io ( L /Te ),
the table below use for the cont rol m
ethod select ion.
"
'"
Pf"Oc:HS 4 T1
lR OrO.r 0 T 0
2,..0rdtr 0.
28T 2.7T 0.1
03
3"'Ord•r 0.81 T J.,7T 0.218
le/T, Control Method
L,/T,< 0.
2 ON·OFF, P, Pl
0.2 < L,
/T,<l.O Pl, PIO
1.
0 < 4/T, Smith predictor ( Feedforward )
10. PID Tuning
Select tuning method ( Ziegler Nichols tuning method )
Consi
der pro
cess condi
tions and sel
ect properly t
uning method
by consi
der limitatio
n of each t
unin
g methods as belo
w.
Open-lo
op meth
od nee
d t
o co
ntr
ol t
he process lo
op in manual
mode f
or ch
ange t
he MV vaLu
e (Contr
ol val
ve, F
inal element and et
c. ).
Closed-l
oop method is more diffi
cultly t
han Open-loop met
hod
but t
akes adv
ant
age more as •
·
el l
, and h
as ri
sk t
o equi
pments in lo
op
damage cause process fluctuation, sel
ect
ed in case process cannot vary
MV vaL
u
c. Th
is met
h
od wil
l make more advant
age with i
nte
gr
aLin
g an
d
t·una'UY process.
Tri
al and Error method need L
o co
ntrol th
e process lo
op i
n
manua l mode like Open-loop method but t
he process parameters (dead
ti
me. Ti
me co
nst
ant and process gai
n ) arc not requir
ed, t
hi
s met
hod
need str
ongl
y undcrsL
undi
ng i
n J
>
I
O t
un
ing behavi
or
s.
11. PIO Tun ing
- Open-Loop method ( Ziegler Nichols tuning method )
- In controller manual mode, Change the MV value and Find
out
p1
·
ocess pa1
·
omete1·s from l'V graph.
!
'1·nr:e.'i.'i Gnin ( Sr.If Rcg11/ at.in11 l'rncc.<.< )
/;.
Steady stale l ine
6 P'
A M'
- ----- ------------------- --
:>
Process Gain ( Kp ) = lJ. PY
I lJ.
MY
13. PIO Tuni ng
( Ziegler Nichols tuning method )
- Open-Loop method
l'1·oc:ess Time Const a 1
1t ( Sel f lleg1
1
/at jac Process
)
'
•
,
'
/;.
' •
.
cady sta le I inc ' '
•
•
. .•• ....... ..
,
..
,
•
'' -
,
, ' '' '
..------------ -----;"':"
-------!----- ' ----, --------
' ' ,
I I " I I
: I ; I I I
' / : : : 0.632 6 PV
''
' ' ' '
' ' --
-
-
-
- -----
l_
_
_
___
__
. ------
- ' ' '
., ' '
'
' i>
- ' '
. '' '
,
' ' '
' Tl
' '
' '
- '
' ' '
f'l
Tl < T2 . Process Time Constant ( T, ) =
'
Tl
14. PIO Tuni ng
( Ziegler Nichols tuning method )
- Open-Loop method
ft ·ocess Deacl T
ime( Sel f 8etw lol i nc Pr
ocess
.
)
'' •''
- Steady
-
sta-
t-
e -I inc ,
'.'
- - - - -
''"
:
'
''
. ''
' '
'' '' '
''
'' ''
' ' '
' ' -,'--·
- ----- '
'
,-
'
' . '
' ' '
i>
· ·
. '
;
' I I
, . I
''
Process Dead Time
( L• )
15. .-.,1 -- ' - - - - - I-_;_J.IV
y :i::_
:::::_
_
,':_
·
::
,
, ' '
Equivalent Process Gain
,.
'' ,
,
;
',,,
,
"
:
PIO Tuning
( Ziegler Nichols tuning method )
Open-Loop method
Proces.
< Gain ( lntegrot jnc Process
)
16. PIO Tuning
- Open-Loop method (Ziegler Nichols tuning method
)
Process Time Constant 1111d Process Dead Time ( Integrat ing Process )
'
-·--------'r--------':-----':-----------------------.
---
, '
'I 'I 'I 'I
- --------•
r-------- ----'
--- ------r- ,
'0.632 A PV
: : : • 0.283 A l'V I
_;..._....,;..._-+-..I.-----_ L_ ---------t_ _ -
Process Time Constant ( T, ) = 1.5( Tl
T2 )
17. PIO Tuning
- Open-Loop method (Ziegler Nichols tuning method
)
Process Time Constant 1111d Process Dead Time ( Integrat ing Process )
'
-·--------'r--------':-----':----------------------- .
---
, '
'I 'I 'I 'I
- --------
'r-------- ----' --- ------r - , 2/3 6 1''
'
I I I t 1/3 {J. f'' I
_;..
'._..... ;
'..._-+
' ..I.------ ----------- ---
Process Time Constant ( T, ) = 1.4 ( Tl
T2 )
18. PIO Tuning
Open-Loop method
lloughl y Tuning by
( Ziegler Nichols tuning method )
ini t ia l value as table below. _
tl1
-0rc:
lie - Contrnl lc r glllll
VB = I/Kc x 100( ')
Ti • lntegrnl l illt: or rl'itl'l t illC
( Sec. I ft.•rci't )
Td • D
nri'lll iVt" t i9C or n it
( S
<
>
c
. )
Method Process Characlerlstlc
SellRerulat n& l
ntecratln1
P Control : Kc •T,/Kp l, Kc = t:. MV / Y
PlControl: Kc = 0
.
9T,/ Kp L, Kc = 0.9 t:.MV I Y
Ti •3.
33L, Ti = 3.33 4
P
I
OControl: Kc • 1.1T,/Kp l, Kc = 1.1t:.MV I v
Ti •2.0l, Ti •2.
0 lr
Td = 0.5l, Td = O.SL,
19. PID Tuning
Close
d-Loop method ( Ziegler Nichols tuning method )
- In control ler au tom
at ic mode ( opera t i ng condi t ion ) ,
PV
approx imate to set -poi 1n. change the 'lil'B of con tro l l er
In tegra l l im
e m
aximum and D
er i va l i ve t im
e min imum, then
and take load step ( change set -poi nt or change process
m
onitor PV r esponding unt i J PV occur sl ighl osci Ila t ion.
to maximum,
decrease 1
6
PB
Loads ) for
Record 1
6
Pll of
osc il la te condi li on ( UI t imate cont rol ler ga in, K
cu ) and Band width
( Ul t im
a te per iod, Pu ) .
l'I>
POosc ::; 1/ K
t u x 100()
20. PID Tuning
Cl
ose
d-Loop method ( Ziegler Nichols tuning method )
- In case cannot fi nd out the point of PV osci ll ation , another one
m
ethod
form
is a lter nat i ve. Adj us t %
Pll and Ti unt il PV become to Decay ra t io
( ll/ A = 1/ 4 ) . Then esti m
a te Pu and K
cu by fol l owing equa t ions.
Pu = 0.9 P
q
Kcu = I . 67 Kpq
PB dccur i-u io -= l/ K
P
<
1 x 100( )
SelJ>Oint
21. PID Tuning
Close
d-Loop method ( Ziegler Nichols tuning method )
lloughl y Tuning by ini tia l va lue as table below._
fh('rc-:
>:c - Controller iwin
'rlJ I/K
c x 1
00()
ll'U - ' ProportiOOlll b.nnd
Tl - lrlt('grlll t 111(! or r t t t tf.e
{ St'
.C./ Rcp•1
1
1 )
Td - Dcr(·ut lvt! t l . e or l'tllC'
( Soe.)
PControl: Kc = 0.
5 Kcu
PlControl: Kc = 0
.
45 Kcu
Ti=0.
83 Pu
P
I
O Control: Kc = 0.6 Kcu
TI =0.5 Pu
Td = 0.1
25 Pu
22. PID Tuning
Trial & Error method ( Ziegler Nichols tuning method )
- In contro l ler autom
at ic mode ( opera t i ng condi t ion ) , PV
approximate to set-poi 1
n . change the 'lil'B of contro l l er to maxim
um,
Integra l l im
e m
axim
um and D
er ival ive t im
e min im
um, then decrease 'liPB
and take load step ( change set -poi nt or change process L
oads ) for
m
oni tor PV responding unt i l PY occur s l ight oscil la t ion.
Sel-po inl
l'' Pt•
.riod
23. PID Tuning
Trial & Error method ( Ziegler Nichols tuning method )
- Adjust ini t ial value of the controller as fol lowing equa t ions.
Ti = 0.67 Pl' Per iod
%
PB =I. 33 'lf>
PB.,..
the control ler unt i l Pl' response as D
ecay ra t io form.
- Fi ne
adjust
>
:
c 'J
C
O
, Ti C:hnrt
:,t t r
Sot 110ir1t
" J I . . I o..-
1•, , 1
. . ..,,. . , l -
r
t.5
.
,
"
l.•,,
24. PID Tuning
Trial & Error method ( Ziegler Nichols tuning method )
- Adjust in i t ia l der ivat ive value of the contro l ler by Td : 0. I Ti
( Ti @ decay ra t io ) .
- Fine tuning, Deriva t ive t ime ( Td ) should vary around 0. L
Ti -
0. 25Ti incase PY respond ing is not target however a fter T
el increasi ng
Kc maybe increased
the prev ious ly,
tun ing cr i teria
to J. 25 t imes and Ti maybe decreased to 2/ 3 t imes of
Final ly Decry rat io form is the best prac t ice for
a f ter PY damping ( overshoot ) stay in tol erable.
25. ( Otfse1
)
r
•
•
Overstlool
cErrof
P Controller I Controller >OControner OJ)timizo )
•
PID Tuning Architecture
P Controller mitigates error but initiates offset.
- I
- D
Control ler
Controller
mit iga tes
mitigates
offset bu t initiates overshoo t.
overshoot for optimization.
