Bo co s b v b iu khin m theo lut PID
Bo co s b v b iu khin m theo lut PID
A L thytB iu khin m PID c thit k theo hai thut ton:
Thut ton chnh nh PID m
Thut ton PID tc
B iu khin m c thit k theo thut ton chnh nh PID gm
u vo: 3 u vo gm sai lch ET gia tn hiu ch o v tn hiu ra, o hm DET
ca sai lch v tch phn IET ca sai lch. u ra: chnh l tn hiu iu khin
u(t)
B iu khin m vi thut ton PID tc bao gm
u vo: 3 u vo gm sai lch ET gia tn hiu u vo v tn hiu ch o, o hm
bc nht DET1 v o hm bc hai DET2 ca sai lch
u ra: l o hm ca tnhiu iu khin u( t)
Do trong thc t thng mt hoc hai thnh phn ca b iu khin PID c b qua
nn thay v thit k mt b iu khin PID hon chnh ngi ta li thng tng hp cc
b iu khin kiu PI hay PD.
B. V dV d v b iu khin m theo lut PD:I. Yu cu:
2 u vo E- sai lch gia tn hiu ch o v tn hiu ra ca b cm bin t -20
n 20, DET l o hm ca sai lch,u ra l P-cng sut lm mt hay si m t -5kW
n 5kW.Phn cng gm 1 cm bin nhit phn hi v chn c ADC ca vi iu khin coi
my lnh l mt thit b c th iu khin cng sut bng in p t 0 n 10 V tng ng
vi cng sut t -5000W n 5000 W. iu khin nhit bng bin tr ni vi mt knh
ADC ca vi iu khin . Chn chu k trch mu l 10s
II. Thit k:
1. i tng: nhit phng 10oC - 40oC.
2. Cm bin nhit : 10oC - 40oC ng vi in phn hi Uph = 0V-10V
3. B iu khin: dng vi iu khin
2 u vo Analog mt u vo cho U mt u cho Uph
1 u ra Analog dng Uk t cng sut iu khin cho my lnh.
4. C cu chp hnh my lnh vi cng sut -5000W n 5000W tng ng vi in p
t 0-10V
* Thut ton cho vi iu khin:
c gi tr ADC1;
c gi tr ADC2;
tnh chnh lch nhit ET v sai phn DET t chnh lch nhit v o hm dng b
iu khin m tnh ton c gi tr t cho cng sut ca my lnh.
t gi tr cng sut tnh c tnh ra gi tr cn np cho DAC a ra in p iu
khin.
* Thit k b iu khin m cho my lnh:
Thit b hp thnh ca b iu khin thc hin cc lut iu khin sau:Nu ET=NM
v DET=ZE th P=PM hoc
Nu ET=ZE v DET=ZE th P=ZE hoc
Nu ET=PM v DET=ZE th P=NM hoc
Nu ET=NM v DET=NM th P=PM hocNu ET=ZE v DET=NM th P=PM hocNu
ET=PM v DET=NM th P=ZE hocNu ET=NM v DET=PM th P=ZE hocNu ET=ZE v
DET=PM th P=NM hocNu ET=PM v DET=PM th P=NM S dng thit b hp thnh
MAX-MIN v gii m theo phng php trng tm tnh P vi mi ET v DET tnh c
cng sut iu khin P
v d:
vi chu k trch mu 10s trong chu k u nhit t l 20oC, nhit o c l
30oC. tnh c ET = -10, lc ny DET=0
ta tnh (-10) = { 0.5, 0.5, 0 }; (0) = { 0, 1, 0 };
tnh c cng sut cho iu khin l:
WSau 10s tc l chu k trch mu tip theo ta o c nhit phng l 29oC
nhit t vn l 20oC ta tnh c ET= -9; DET=
tip tc tnh
tnh c cng sut iu khin l:
W
tng t ta c bng mt s gi tr tnh ton c:ETDETP
100.05-2500
20-0.05-2500
150.053333
15-0.05-1000
-20-0.15000
EMBED Equation.DSMT4
EMBED Equation.DSMT4
B iu khin m
i tng
nhiu
ET
DET
IET
u(t)
EMBED Equation.DSMT4
EMBED Equation.DSMT4
B iu khin m
ET
DET1
DET2
nhiu
EMBED Equation.DSMT4
EMBED Equation.DSMT4
i tng
u
Uk
Bin Tr
cm bin nhit
Uph
U
VK
my lnh
DAC
ADC2
ADC1
EMBED Equation.DSMT4
B iu khin m
i tng
S khi h thng
ET
DET
P
Tc
Ts
S khi b iu khin
PM
ZE
NM
20
0
-20
ET
PM
ZE
NM
0.1
0
-0.1
DET
P
PS
ZE
NS
5000
0
-5000
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